Biology form one notes

INTRODUCTIO TO BIOLOGY

biology is the study of life/living things

BRANCHES OF BIOLOGY
1. Zoology
Is the study of animals

2. Botany
Is the study of plants

3.Microbiology
 The study of microorganisms

 importance ofbiology

1.   helps to solve environmentalproblems 
2. Helps to learn scientificskills For entry into otherprofessions/careers
3.  To apply knowledge to everyday lifesituation
4.  To classify organisms into their rightgroups understanding livingorganisms

 characteristics of livingorganisms

•   feeding/nutrition 
• Growth and development
•  respiration (to produceenergy) 
• sensitivity/irritation/response 
• excretion (getting rid of metabolic wastematerial) 
• movement/locomotion 
• reproduction 

  differences between plants and animals

handlens
Is the Convex lens mounted on a frame and used to magnify small objects forviewing.

 How is a hand lens used?
place the lens a short distance from theeye Bring the object to be viewed near the lens until an enlarged and clear image can beseen.

When is a hand lens used?
 - For reasonably sized objects such as insect wing, leg, flower parts.-

Cannot be used for small objects such as cells,stomata.


calculation of drawing magnification

Drawing magnification= length of drawing ÷ length of object or image

Example
Object has length of 2 cm and the length of it is drawing is 8 cm. calculate drawing magnification of object.

Solution
You are given
      length of objective=2cm
      Length of drwaing=8cm
   Mgnificstion of drwaing =?

Length of magnification = 8cm/2cm
                                             = 4

Microscope
MICROSCOPES One of the most widely used tools in Biology

-An instrument that produces an enlarged image of an object

-Magnification – the increase in an object’s apparent size

-Resolution – the power of a microscope to clearly show detail

 TYPES OF MICROSCOPES

1. Compound Light Microscope LM

With this type of microscope the thin sliced (enough to be transparent) and sometimes stained specimen is mounted on a glass slide to be viewed

The slide is placed on the stage and a light source (a light bulb or mirror in the base) directs the light upward

Light passes through the specimen and through the objective lens, which is positioned directly above the specimen

A set of objective lenses is located on the rotating nosepiece enlarges the image of the specimen with different powers of magnification

The most powerful objective lens produces an image 40 times (40X) the actual size of the specimen From the objective lens, the magnified image is projected up through the body tube to the ocular lens in the eyepiece where it is magnified further (10X)

To compute the total magnification of a microscope, multiply the power of magnification of the lens being used (40X, 100X) by the power of magnification of the ocular or eyepiece lens (10X)

example: 40 X 10 = 400X total power of magnification

 The Resolution power of LM’s is limited by the physical characteristics of light (At powers of magnification beyond about 2000X, the image of the specimen becomes blurry.)


 LIGHT MICROSCOPE Electron

 Microscopes Used to view extremely small objects Beam of Electrons, rather than light, produces an enlarged image

Electron microscopes are more powerful than LM’s

 There are several types of electron microscopes

Transmission Electron Microscope Can magnify objects up to 200,000 times Projects image onto a screen or photographic plate Used to produce greatly magnified images of internal details of a specimen Can not be used to view living specimens TEM

MICROSCOPE Scanning Electron

Microscope (SEM) Produces a 3 dimensional image

 Specimens aren’t sliced but are sprayed with a fine metal coating A beam of electrons is passed over the surface of the metal coating to emit a shower of electrons

Showered electrons are projected onto a fluorescent screen or photographic plate SEM’s produce greatly magnified image of surface details of specimens

Can magnify up to 100,000 times Can not be used to view living specimens


classification
 Orderly arrangement of living organisms into various groups according to theirsimilarities.

for examples
 List the external features used to classifyplants rhizoids(e.g.mosses) frond (e.g.ferns) roots e.g. taproot, fibrous roots, modifiedroots flowers- leaves buds seeds -

 the external features used to classifyanimals horns e.g. cattle, goat, sheep, deer, gazelle etc 

hooves e.g. cattle, sheep,donkey mammary glands e.g. cattle, dog, sheep,cat 

hair e.g. human,cat

 Shell e.g. snail,Tortoise 

spines e.g. hedge hog,porcupine

  reasons why classification isimportant

- Placing/grouping living organisms into correct groups calledtaxa Identification arrange information about living organisms into orderly and sequential manner i.e. it is easy tostudy organisms ingroups

 -helps in understanding evolutionary relationships monitoring disappearance and appearance of organisms i.e. predict characteristics oforganisms 

 i) Name the taxonomic units of classification in descendingorder Kingdom (largestunit) Phylum (animals)/division(plants) Class Order Family Genus Species(smallestunit)

 - aspecies- all organisms which can interbreed and give rise to fertile (viable)offspring 

  the major kingdoms used inclassification

 -monera

 -protoctista/protista

 -fungi -plantae 

-animalia

 i)  the term binomialnomenclature a scientific system of naming organisms using the generic/genus and specific/species names- e.g. for humans, Homosapiens

  principles followed during binomialnomenclature 

- first (generic) name should begin with a capital letter while the rest are smallletters

- the two names are printed in italics and if handwritten should be underlined eachseparately

  advantages of using binomialnomenclature

- no confusion about which organism is referred to names are internationally accepted regardless oflanguage 

-shows evolutionary relationship hence easy tounderstand useful in naming many species unlike use of commonnames 

  types ofclassification traditional (using commonnames) scientific(using binomialnomenclature

CELL

 a) i) cell it is the basic unit of organization of an organism i.e. the basic functional and structural unit of an organism. 

CELL BIOLOGY

  structure and functioning of a cell also called cytology

  microscope 

is an instrument used to magnify objects and make them appear bigger.  

 types of microscope

1. the light microscope

2. the electron microscope

 

-  The purpose of using a light microscope it magnifies and reveals the structure details of tiny objects such as the cell, that cannot be seen by the human eye directly 

-  light microscope

  functions of the labeled parts 

a.) Eye piece used to look through and to magnify the object

 b.) Course adjustment knob raises or lowers body tube and focuses object roughly

 c.)Fine adjustment knob raisesor lowers body tube by small distances to bring image into fine focus

 d.) objective lens brings image into focus and also magnifies object/image stageis a platform where object or specimen on slide is placed mirror reflects light through condenser and directs it to objective lens clips hold glass slide in position body tube holds eyepiece and revolving nose piece which has objective lenses limbor base support whole instrument arm for holding when carrying instrument revolving nose piece holds objective lens in place enabling change from one objective lens to another 

 e) i) Explain the procedure followed when using a microscope put the microscope on the bench with the stage facing away from you(viewer) turn the lower power objective to click in line with the eyepiece Ensure that the diaphragm/iris is fully open Adjust the mirror until the stage is illuminated with enough light - Place the slide containing the specimen on the stage for magnification

   precautions that are necessary when handling a microscope 

-always use two hands when carrying it

-never place a microscope too close to the edge of the bench or table

- do not touch the mirror and lens with wet or dirty hands

- clean dirty lenses using a special lens cleaning cloth 

-clean other parts using a soft cloth or tissue paper

- low power objective must click into position before and after use.

- Do not wet any part of the microscope Clean and store well after use 

  magnification

 The power of making an image larger

  parts of a cell

•  cell membrane 
• cytoplasm 
•  cell wall 
•  nucleus 
• vacuole

  general structure of a plant and animal cell 

  functions of each part of cell

1.  Cell wall found in plant cells in addition to cell membrane made of cellulose which makes the plant tough allows gases, water and other substances to pass through
2.  Cell membrane permeable/selective to control movement of materials in and out of cells bound/encloses the cell contents also called plasma membrane or plasmallema 
3.  Cytoplasm fluid medium where chemical reactions occur also where cell organelles are suspended 
4.  Nucleus controls cell activities 
5.  Nucleolus synthesizes DNA Vacuole sacs filled with fluid called cell sap large in plants but small in animals act as reservoirs for food and harmful wastes which would otherwise interfere with the metabolism in cytoplasm 
6.  Lysosomes store hydrolytic enzymes destroy worn out cell organelles, cells, pathogens digestion of food in unicellular organisms autolysis 
7.  Golgi apparatus processing/packaging of synthesized materials transporting/secretion of packaged materials/cell materials e.g. glycoproteins and mucus production of lysosomes Ribosomes where protein synthesis takes place  
8. Mitochondrion synthesis of ATP/energy Chloroplasts where photosynthesis takes place
9.  Endoplasmic reticulum transport of cell secretions can be rough or smooth 

  the functions of cell sap

• stores chemical substances, sugar, salts 
• maintains shape of the cell
• provides mechanical strength 
• plays a role in osmoregulation by creating an osmotic gradient that brings about movement of water 

 Comparison between plant and animal cells

1.  plant cells have chloroplasts lacking in animals 
2. animal cells have many small vacuoles while plant cells have a large central vacuole
3.  plant cell have cellulose cell walls lacking in animal cells 
4. cytoplasm in plant cell is in the periphery but in animal cell it is centrally placed
5.  plants store starch, oil and protein while animals store gats and glycogen 
6. animal cells have centrioles which plant cells do not have 

 Specialized plant cells include epidermal, guard cell and palisade cell

 Tissue these are cells of a particular type grouped together to perform a certain function animal tissues include epithelium, blood, nerves, muscle, skeletal and connective tissues plant tissues include epidermal, photosynthetic, vascular, strengthening tissues

 Organ tissues combine together to form organs an organ is a complex structure with a particular function animal examples include heart, liver, kidney, lungs, brain, blood vessels, muscles, skeleton Plant organs include leaves, roots, flowers, and stem. 

 Organ system  are grouped together to form systems also called organ systems animal systems include excretory, digestive, respiratory, nervous, circulatory, endocrine(hormones/glands), skeletalsystems plant systems include transport system

  structures which are present in plant cells but absent in animal cells 

• Chloroplast 
• Cellwall 

 Name the structures which are present in animal cells but absent in plant cells Lysosomes Centrioles Pinocytic vesicles Explain how to estimate cellsize Materials cell sizes are measured in units knownas micrometers (my) required is a transparent ruler marked in millimeters 1mµ = 1 mm 1000 Procedure - Click to low power place transparent ruler with its millimeter marks on the stage focus so that the millimeter marks can be seen as thick dark lines estimate the diameter of field of view by counting the one millimeter spaces between the first mark and the last one across the field of view as shown below the diameter of the field of view above is estimated as 3.2 mm convert the diameter of the field of view from millimeters to micrometers i.e. 3.2/1000 Estimate the fraction of the field of view occupied by the cell. This is done by estimating the number of cells places end to end that would fill the diameter of the field of view as shown below in the figure above, it is estimated that approximately six cells will occupy the diameter of the field of view therefore, one cell will occupy 1/6 of the field of view its diameter is calculated as 1/6 times the diameter of the field of view i) In a drawing of a giraffe, the height of the head from the ground was recordedas 10cm. the drawing also showed a magnification of 0.02. calculate the actual height of the giraffe Drawing height= 10cm= 500cm Magnification 0.02 In a class experiment to estimate sizes of cells a student observed and obtainedmillimeter marks on the field of view of a microscope as shown in the diagrambelow. Millimeter marks If the student counted 40 cells on the diameter of the field of view, what was the approximate size of the each cell inmicrometers? Diameter of field of view= 3 x 1000= 75 mµ Numberofcells 40 Under which of the following light microscope magnifications would one see a largerpart of the specimen? X40 or x400? Give a reason x40 Smaller magnification gives a wider field of view hence a larger part seen. e.) a) i) Define cell physiology the study of the functions of a cell in relation to their structure State the functions of thecell exchange of materials between the cell and the external environment physiological reactions e.g. photosynthesis production of energy through mitochondria i) Describe the structure of cellmembrane made up of threelayers Lipid portion sandwiched between two proteinlayers Lipid portion enhances penetration of oil solublesubstances Pores present to facilitate inward and outward movement of water soluble substances Give the properties of cellmembrane semi-permeable sensitive to changes in temperature and pH Possesses electric charges. i) What isdiffusion? movement of substances/molecules/particles/ions from a region of high concentration to a region of low concentration (until equilibrium is reached) State the factors affectingdiffusion diffusion gradient/concentration gradient surface area to volume ratio temperature size of molecules state of the diffusing substance thickness of membrane and tissues Explain the roles of diffusion in living organisms gaseousexchange absorption of digested food in intestines movement ofsalts in plants movement of materials between blood capillaries and tissues removal of waste materials from bodies of small organisms air movement in intercellular spaces in plants Suggest an experiment to demonstratediffusion to a beaker of water, drop crystals of potassium permanganate or copper sulphate leave to stand in a place without disturbing observe the spreading of molecules liquid is coloured uniformly due to diffusion i) What isosmosis? Movement of water or solvent molecules from a dilute/hypotonic solution to a more concentrated/hypertonic solution across a semi-permeable membrane. OR movement of solvent molecules from a region of their higherconcentration to a region of theirlowerconcentration through a semi-permeable membrane State the factors affectingosmosis concentration of the solution concentration gradient temperature Explain the roles of osmosis in livingorganisms helps to draw water into roots of plants helps in the passage of water from one living cell to another in the plant helps to keep plant cells turgid increasing support Helps in opening and closing of stomata. Folding of leaves in Mimosa pudica when touched Feeding in insectivorous plants A group of students set up an experiment to investigate a certain physiologicalprocess. The set up is as shown in the diagrambelow. Aftersome time they observed that the level ofsugar had risen. What was the physiological process under investigation? Osmosis Why was there a rise in the level of sugar solution? sugar solution is more concentrated than cell sap osmosis those cells become more concentrated and therefore draw water from neighbouring cells this process continues until the cells in contact with the water in the container draw it up causing a risein the level of the sugarsolution Suggest the results that the students would obtain if they repeated the experiment using cooked potato The level of sugar solution will not rise. What is the reason for your suggestion? boiling kills/destroys cells making them osmotically inactive Explain the followingterms Hypnotic a solution whose concentration is lower than that of the cell Isotonic a solution whose concentration is the same as that of the cell Hypertonic a solution whose concentration is higher than that of the cell Turgor pressure As a cell gains water, its vacuole enlarges and exerts an outward pressure called turgor pressure. Plasmolysis if a plant is placed in a hypotonic solution if loses water the protoplasm shrinks to an extent that it pulls away from the cellulose cell wall Wilting when a plant is turgid it can standupright however, if the cells lose a lot of water, turgidity isreduced the plant then droops because the cells are flaccid the plant is said towilt Haemolysis if red blood cells are placed in distilled water, the cells take up water by osmosis, swell and burst this is because it does not have any mechanism like the cellulose cell wall to prevent overstretching nor any means of removing excess water this is called haemolysis A form one student placed red blood cells in different salt concentrations andobtained the followingresults:- Therewas a gain (+) no change (0 zero) and aloss (-)in the volume of the cells as show below:-Briefly explain the results of the experiment in the first solution , red blood cell absorbed water by osmosis, swell and burst (haemolysis) hence the solution is hypotonic in the second solution, there was nochange in size or structure as it was isotonic henceno osmotic gradient in the third solution the red blood cell lost water to shrink hence became crenated as the solution was hypotonic to the cell cytoplasm. i) What is activetransport? movement of molecules and ions against a concentration gradient the substances move from a lower to a higher concentration gradient by use of energy State the factors affecting active transport oxygen concentration temperature change in pH glucose concentration enzyme inhibitors Why is oxygen important in theprocess of activetransport? Oxygen is required for respiration, which produces energy necessary for the process tooccur. ) the factors that affect the rates of the following process in livingorganisms. a.) DIFFUSION. Diffusion gradient which refers to the difference in concentration of molecules between the region of high concentration and the region of low concentration. Increasing the concentration gradient causesan increase in rate of diffusion and viceversa. -Surface area to volume ratio .is the ratio of total surface area exposed by an organism compared to its body volume. Small sized living organisms have a large surface area to volume ratio. The larger the surface area to volume ratio ,the high the rate of diffusion and vice versa. Small organisms like amoeba and paramecium can hence rely on diffusion for transport of substances into and within its body and removal of waste products -thickness of membranes. Molecules take longer to diffuse across thick membranes than across thin membranes hence the thin the membrane the higher the rate of diffusion. -Temperature. Increasing temperature increases the kinetic energy of diffusing molecules making them to spread faster. Increasing temperature increases the rate of diffusion and vice versa -size of molecules/molecular weight.Small sized molecules/molecules of low molecular weight move/diffuse faster hence the rate of diffusion is high where the molecules involved are small or have low molecular weight and vice versa. B.)OSMOSIS -Temperature. Increasing temperature increases the kinetic energy of water molecules making them to spread faster. Increasing temperature increases the rate of osmosis and vice versa -concentration gradient/diffusion pressure deficit. Refers to the difference in concentration on either side of a semi-permeable membrane. The higher the osmotic pressure difference the higher the rate of osmosis. C.) ACTIVE TRANSPORT OXYGEN CONCENTRATION. It is required for respiration/to oxidize respiratory substrates to release energy required for active transport. an increase in oxygen concentration causes a simultaneous increase to the rate of active transport upto a certain level. PH Enzymes being protein in nature are PHspecific. Extreme change in PHaffect the rate of respiration which is controlled by enzymes and may denature the enzymes reducing the rate of active transport. - GLUCOSE CONCENTRATION. is the main respiratory substrate for energy production. An increase in glucose concentration in cells increase the rate of respiration and hence the rate of active transport is increased upto a certain optimum level beyond which any additional increase in glucose concentration has no effect. TEMPERATURE. The process of respiration by which energy for active transport is generated is controlled by enzymes. Enzymes work best at temperatures of between 350c-400c,usually called optimum temperature ranges. At very low temperatures enzymes are inactive lowering the rate of respiration hence low rates of active transport . increase in temperature above optimum ( above 400c)denatures enzymes slowing down respiration and ac tive transport until it finally stops. ENZYMES INHIBITORS. They are substances which slow down (by competing with the enzyme for the active sites in the substrate) or stop ( by blocking the active sites of the enzyme) the activity/funtioning of enzymes .this slows down or stops respiration and so is active transport. CONCENTRATION OF CARRIER MOLECULES IN THE CELL MEMBRANE. They are substances that bind to the ions being transported actively and carrying them across the membrane . increase in concentration of carrier molecules increases the rate of active transport upto a certain level and viseversa. 4.) explain briefly the role of osmosis in living tissues. Inplants: Osmosis facilitates the absorption of water from the soil by plant roots, water is required for the process of photosynthesis. Turgidity of cells contributes to support in herbaceous plants and helps plant to maintain shape. Helps in closing and opening of stomata regulating the process of gaseous exchange and transpiration. It facilitates feeding in insectivorous plants like venus fly trap. In animals: Enables reabsorption of water from the kidney tubules back to blood stream facilitating the process of osmoregulation. It enables organisms in fresh water bodies like amoeba to absorb water. it is applied in food preservation. 5.) explain what happens when plant and animal cells are put in hypotonic and hypertonic solutions. a. i)plant cells in hypotonic solution. The concentration of the plant cell sap is hypertonic to the solution/water medium. the cell draws in water by osmosis through the cell wall, cell membrane into the cell cytoplasm. Water enters the cell vacuole by osmosis; it enlarges and exerts an outward pressure on the cell wall called turgor pressure. Increased turgor pressure pushes the cell cytoplasm against the cell wall until the cell wall cannot stretch any further. The cell becomes firm or rigid and is said to be turgid. As the cell wall is being stretched outwards, it develops a resistant inwards pressure that is equal and opposite to the turgor pressure and this is called wall pressure. ii.) Plant cells in hypertonic solution. The plant cell sap is hypotonic to the solution medium. Water molecules are drawn out of the plant cells by osmosis into the hypertonic solution through the semi-permiable membrane of the plant cells. As a result the plant cell will start to shrink/less rigid and become flabby. The cell membrane/plasma membrane is pulled away from the cell wall and the cell is said to be flaccid. this process by which a plant cell lose water, shrink and become flaccid is called plasmolysis. However the shape of the plant cell is maintained by the tough rigid cellulose cell wall which prevents crenation in plant cells. b.i) Animal cells in hypotonic solution. The concentration of water in the cytoplasm of the plant cells is hypertonic to the solution medium in the test. Water molecules are then drawn into the animal cell cytoplasm from the surrounding medium by osmosis through the semipermiable membrane. the cell swells as water is drawn into them by osmosis .as water continues to enter into the cell,the weak animal cell membrane bursts a process called lysis. in red blood cells this process is called haemolysis. However in unicellular organisms like amoeba and paramecium,bursting of their cells does not take place because they have specialized organelles called contractile vacuoles for removal of exces water out of their bodies/cells. ii.) animal cells in hypertonic solution. The concentration of the animal cells cell cytoplasm is hypotonic to the solution medium in the test. the surrounding hypertonic solution will draw water out of the animal cells by osmosis through the semipermeable membrane. Continued loss of water causes the cells to be smaller in size and their membranes become wrinkled. This process will continue until the concentration of the cell sap and the surrounding medium is equal i.e isotonic.the process by which animal cells lose water and shrink is called crenation. 6.) Explain briefly the role of active transport in living organisms. It is involved in active reabsorption of glucose and mineral salts in kidney tubules during formation of urine. it enables the absorption of digested food from the alimentary canal/small intestines into the blood stream. Excretion of waste products from body cells for eventual removal. Involved in transmission of nerve impulses within the nerve cells through the sodium pump which maintains a balance between sodium and potassium ions. It facilitates accumulation of substances in the body cells to offset osmotic pressure of organisms in dry and marine environment allowing them to absorb water by osmosis and avoid desiccation. In plants it enables plant roots to absorb water from the soil against the concentration gradient. It’s involved in translocation of manufactured food in the phloem tissue within the plant body. It’s involved in the opening and closing of the stomata through the sodium-potassium pumpmechanism. Outline the roles of active transport in livingorganisms mineral salt intake by plants selective reabsorption of glucose and some salts by kidneytubules absorption of digested good by small intestines excretion of waste products from bodycells reabsorption of useful materials in the blood stream or at the tissue fluid sodium pump mechanism in the nerve cells/neurons f.) a) i) Define nutrition the process by which living organisms obtain and assimilate nutrients ii) State the importance of nutrition for respiration to get energy for growth for development to repair and replace worn out and damaged parts and tissues Differentiate the various modes offeeding Autotrophism manufacturing food from simple organic substances types are photosynthesis and chemosynthesis Heterotrophism obtaining food from autotrophes and other organic substances typesare holozoic, saprophytic andparasitic g.) a) i) Define photosynthesis the process by which green plants build up organic compounds from carbon IV oxide and water in the presence of sunlight ii. State the importance of photosynthesis formation of sugars/glucose which is a source of energy purification of air(CO2 is used, O2 is released) storage of energy to be used later in respiration stores energy in wood, coal, oil to be used later to run industries Structural adaptation of the leaf to its function The leaf has a broad and flattened lamina to provide a large surface area for trapping optimum light for photosynthesis and allow maximum gaseous exchange. The leaf epidermis is thin ( one cell thick) to reduce the distance across which diffusion of carbon (iv) oxide gas to palisade cells and oxygen gas from palisade cells takes place. The leaf has numerous stomata that allows easy diffusion of gases into and out of the palisade tissue. The leaf cuticle and epidermis are transparent to allow easy penetration of light to the photosynthetic tissue. The palisade cells are numerous,elongated and contain numerous chloroplasts to trapping optimum lightfor photosynthesis. The palisade tissue is just beneath the upper epidermis exposing them to trap optimum lightfor photosynthesis. The leaf has numerous leaf veinsconsistingof a.) xylem vessels and tracheids for transporting waterand dissolved mineral salts from the soil to the photosynthetictissue b.) phloem tissue for translocation of of manufactured food from the leaf to storage organs and other parts of the plant . Numerous and large air spaces in the spongy mesopyl layer for optimum gaseous exchange with the photosynthetic tissue. Phylotaxy which is regular arrangement of leaves on the stem minimizes overshadowing andoverlapping exposing all leaves to light forphotosynthesis. The prominent midrib and leaf veins reduces chances of rolling of leaves maintaining a large surface area for trapping optimum light forphotosynthesis. Describe the structure and function ofchloroplast Structure Function structure in which photosynthesis takes place Adaptations has numerous/many grana to provide large surface area for packing many chlorophyll pigments have numerous chlorophyll pigments which trap sunlight/light for photosynthesis has stroma/third matrix which contain certain enzymes that catalyze photosynthetic reactions d) i) Give a word equation for photosynthesis Carbon (iv)Oxide+water sunlight sugar + oxygen Chlorophyll NB6CO2 +6H2O C6H1206 +6O2 .) describe briefly the process of photosynthesis in plants. The process of photosynthesis takes place in green plants allowing them to make their own food. The process is controlled by enzymes and involves a series of reactions that take place in chloroplasts. The raw materials required are water and carbon (iv) oxide.the process takes place in two consecutive stages i.e Light reactionstage. It’s also called the light dependent stage as it requires light energy . the reactions take place in the granna of the chloroplast. light energy from the sun is trapped by chlorophyll in the chloroplast and converted into chemical energy. This energy splits water molecules into hydrogen ions and oxygen atoms a process is called photolysis. The oxygen atoms are released as aby product or used up in the process of respiration. The hydrogen ions formed are used in the dark stage ofphotosynthesis. Water hydrogen ions + oxygenatoms 2H2O 4H+ + o2 g Some of the light enrgy is used to combine a molecule called adenosine diphosphate(ADP) with a phosphate group to form the rich energy molecules called adenosine Tri-Phosphate(ATP) ADP +P ATP Dark reaction stage. It’s also called the light independent stage of photosynthesis since light is not required because it can take place both in presence and absence of light. the reactions are controlled by enzymes. the hydrogen atoms released in the light stage are combined with carbon(iv)oxide to form simple sugars mainly glucose. The process uses energy from ATP. This is reffered to as carbon (iv) oxide fixation. The reactions take place in the stroma of chloroplast. The excess glucose is converted into starch or lipids for storage. The general process of photosynthesis can be summarized by the following word and chemical equitions. Water + carbon(iv)oxide light&chlorophyll glucose + oxygen 6H2o +6co2 C6H12O6 +6O2 9.) factors that cause high rate of photosynthesis. High water availability in the soil. Water a raw material for photosynthesis is split in presence of light to provide the hydrogen ions required in carbon (iv) fixation. When water is readily available more hydrogen ions are produced hence high rate of photosynthesis. High light intensity. Light splits water molecules to hydrogen ions and oxygen atoms. Increasing light intensity increases the rate of photosynthesis up to a certain level beyond which other factors become limiting and rate of photosynthesis becomes constant. rate of photosynthesis Increasing light intensity Day length. Long day length especially at high latitudes (temperate regions) provides more light for photosynthesis causing an increase in the rate of photosynthesis. Light quality. The preferred wavelengths for photosynthesis range between 400nm-700nm. the rate of photosynthesis is higher in red and blue light and lower in all other types of light. Concentrationofcarbon(iv)oxide.It’sarawmaterialrequiredtocombinewithhydrogenionstoformsimple carbohydrate molecules. Increasing the concentration of carbon (iv) oxide increases the rate of photosynthesis up toanoptimumlevelbeyondwhichotherfactors limit the rate of photosynthesis. rateof photosynthesis concentration of co2 f) Give the differences between the light and dark reactions during photosynthesis Light reactions Dark reactions occurs in grana occurs in stroma h.) a) i) What are chemicals of life? substances which make up cells, tissues and organs of the living system they combine to form organic compounds What are organiccompounds? compounds that contain the element carbon List the organiccompounds proteins carbohydrates lipids(fats and oils) vitamins enzymes nucleic acids(DNA and RNA) i) What arecarbohydrates? Compounds of carbon, hydrogen andoxygen The elements are in the ratio of I carbon: 2 hydrogen: 1oxygen ii) Name the groups of carbohydrates monosaccharides (simple carbohydrates) e.g. glucose, fructose and galactose disaccharides ( formed when two monosaccharides combine) e.g. maltose, sucrose, lactose polysaccharides (composed of many monosaccharides and disaccharides) e.g. starch, glycogen, cellulose State the general functions ofcarbohydrates production of chemical energy storage of starch(plants) and glycogen (animals) commercial uses e.g. manufacture of paper, textiles i) what areproteins? compounds of carbon, hydrogen and oxygen and in addition nitrogen, and sometimes sulphur and or phosphorus building blocks are called amino acids Name the types of aminoacids essential amino acids which must be supplied in food since they body cannot synthesize them Non-essential amino acids which body can synthesize. State the classes ofproteins first class proteins which supply all the essential amino acids second class proteins which lack at least one amino acid Give the functions ofproteins structural compounds e.g. muscles, hair, hooves, and feathers as enzymes e.g. pepsin, trypsinhormones e.g. insulin and glucagons antibodies part of haemoglobin molecule actin and myosin in muscles collagen in bones and cartilage pigments in rods and cones for coordination components of blood i.e. plasmaproteins d ) i) What are lipids Fats andoils They contain carbon, hydrogen andoxygen However, they contain a higher proportion of carbon and hydrogen but less oxygen that incarbohydrates Name the types oflipids oils(liquid under room temperature) fats (solid under room temperature) What are the building blocks oflipids? fatty acids and glycerol v) State the functions of lipids production of energy source of metabolic water structural compound e) i) What are enzymes? a chemical compound, protein in nature, which acts as a biological catalyst State the properties ofenzymes are highly specific in nature they are not used up during chemical reactions work within specific range of temperature work within specific range of pH enzyme controlled reactions are reversible State the factors that affect enzymeaction temperature substrate concentration pH of the medium enzyme concentration presence of inhibitors and co-factors Name the types of enzymeinhibitors competitive inhibitors non- competitive inhibitors What are the functions ofenzymes? enable cellular reactions to take place at a reasonably faster rate Control cell reactions therefore no violent incidences occur in cells that might burn them. i.) a) Explain the various types of heterotrophic nutrition Holozoic Mode of feeding by animals where solid complex food substances are ingested, digested and egested. Saprophytism feeding on dead organic matter Parasitism feeding from another organism but not killing it Symbiosis an association in which organisms of different species derive mutual benefit from one another Differentiate between omnivorous, carnivorous and herbivorous modes ofnutrition Herbivorous herbivores feed exclusively on vegetation Omnivorous omnivores are animals which feed partially on plant materials and partially on flesh e.g pigs Carnivorous Carnivores feed on flesh alone e.g. lion i) What isdentition? Refers to the number, arrangement and kind of teeth in an animal ii) Distinguish between the terms homodont and heterodont homodont have same kind , type, shape and size of teeth which perform similar function e.g. fish, reptiles and amphibians Heterodont have different kind, type, shape and size of teeth which perform different functions as those found in mammals. iv) Name the types of teeth found inmammals Incisors Canines Pre-molars Molars Describe the adaptations and functions of various types of mammalianteeth Incisors chisel shaped/wedge shaped found in the front of the buccal cavity used for cutting Canines next to incisors very sharp and pointed located at the sides ofjaws used for tearingfood ii) Premolars next to canines but before molars have cusps and ridges on theirsurface used for crushing and grinding iii) Molars found at the back of the jaw have cusps and ridges on their surface absent in young mammals but appear later when permanent teeth grow used for grinding and crushing i)Draw a labeled diagram to represent internal structure of a mammaliantooth. ii) State the functions of the labeled structures labeled Dentine main constituent of teeth like bone in structure but contains no cells Enamel protects tooth from mechanical/physical injury the hard covering of the exposed part of teeth Crown portion of tooth above the gum covered with dentine Root part imbedded in the jaw below the gum covered by substances called cement cement is hard and bone-like Cement bone-like substance covering root and enamel of mammalian tooth Neck region at the same level with the gum forms a junction between the crown and root covered by enamel Pulp cavity at centre of tooth within dentine has blood vessels for transporting nutrients/food and gases has nerves for sensitivity i) What is dental formula? formula indicating the number of each kind of teeth for a given species of mammal only half the jaw isincluded the number in the upper jaw of one side is written above that in the lower jaw of one side the categories of teeth are given in the order incisors, canines, pre-molars, molars Give examples of dentition in namedmammals carnivore e.g. dog i2/3 , c 1/1, pm 2/3, m2/3 = 42 herbivore e.g. sheep I 0/3, c 0/1, pm 2/3, m3/3=30 Omnivoree.g. human I 2/2. c1/1, pm2/2, m 3= 32 How would one use dental formula to identifythe following? Herbivores presence of diastema/gap between incisors and premolars free movement of tongue absence of incisors in upper jaw absence of canines presence of hard pad closely packed molars Carnivore presence of canines presence of carnassial teeth presence of incisors in upper jaw/absence of diastema/gap between incisor and premolar State the functions of the following structures inmammals Carnassials tearing flesh from bones Pad of gum provides grasping surface for lower incisors Name the common dental diseases dental caries periodontal (pyorrhea and gingivitis) j.) a) i) What is digestion? breakdown of complex food particles by enzymes to simple substances which can be absorbed ii) Explain the types of digestion Intercellular Digestion that takes place in food vacuoles inside cells. Extra cellular digestion that takes place outside cells e.g. in the digestive tract i)Draw human digestive system ii) Describe the process of digestion in the various parts of the human digestive system Mouth contains teeth for chewing has tongue for mixing food with saliva has salivary glands for chemical digestion, secretion of enzymes and mucus secretion starch is acted on by salivary amylase enzymes to produce maltose the tongue rolls food into a bolus which is carried into the stomach by peristalsis peristalsis is movement of food along the gut by waves of contraction it facilitates rapid digestion due to its mixing action Oesophagus also called gullet forms a passage for food by peristalsis connects the mouth to the stomach Stomach has gastric glands which secrete gastric juices these juices contain hydrochloric acid(HCL), mucus, and the enzymes pepsin, rennin and lipase HCL produces an acidic medium for enzyme action Proteins are acted upon by pepsin to produce peptides Caseinogen is acted upon by rennin to produce casein Fats are acted upon by lipase to produce fatty acids and glycerol Mucus lubricates the stomach and prevents autolysis of stomach (mucus protects stomach) Duodenum the first u-shaped part of the small intestine food in the stomach is now in a semi-liquid form called chime chime leaves the stomach by peristalsis into theduodenum there, the liver produces bile pigments, bile salts and sodium hydrogen carbonate the stomach is usually alkaline to neutralize chime which is acidic bile salts emulsify fats bile comes from the gall bladder through the bile duct sodium hydrogen carbonate provides the correct pH/alkaline pancreatic juices are released by pancreas into the duodenum the juices contain trypsin, chemotrypsin, amylase, lipase and protease proteins are acted upon by trypsin to form polypeptides and amino acids starch is broken down to maltose by amylase Ileum produces intestinaljuices Intestinal juice contains maltase, sucrase, lactase, erepsin, lipase, and several otherpeptidases Maltose is broken down to glucose and galactose bylactase Sucrose is acted upon by sucrase to glucose Polypeptides are broken down into amino acids byerepsin Mucus secretion is to protect the ileum wall fromdigestion/autolysis Colon Commonly called the largeintestine Wider than theileum has several mucus-producing cells Highly folded for waterabsorption Also prepares food foregestion egestion is the process by which the insoluble parts of food are discharged from the body in form offaeces. Rectum Muscular andenlarged it producesmucus used for storage and removal offaeces Anus found at the exterior end of the rectum The rectum opens into theanus The anus has anal sphincter to controlegestion Anus is used for egestion offaeces Explain how mammalian intestines are adapted to perform theirfunction - The mammalian intestines are relatively long and coiled. This allows food enough time and increases surface area for digestion and absorption of products of digestion The intestinal lumen (inner wall) has projections called villi to increase surface area forabsorption The villi have projections called micro-villi which lead to further increase of surface area for absorption - The walls have glands which secrete enzymes for digestion e.g. maltase, sucrase, lactase, peptidase andenterokinase. Goblet cells (mucus secreting cells or glands) produce mucus which protects the intestinal wall from beingdigested and reducesfriction. Intestines have openings of ducts which allow bile, a pancreatic juice into thelumen The intestines have circular and longitudinal muscles whose contraction and relaxation (peristalsis) leads tomixing of food with enzymes (juices) helps push food along thegut. The intestines are well supplied with blood vessels that supply oxygen and remove digestedfood. Intestines have lacteal vessels for transport of lipids (fats andoils) Intestines have thin epithelium to facilitate fast/rapidabsorption/diffusion What is the function of hydrochloric acid indigestion? killsbacteria activates trypsinogen to trypsin which digests proteins to peptones and peptones to soluble amino acids - provides acidic medium for gastricenzymes i) What isassimilation? The process by which digested food is taken up by cells and used in the body for variouspurposes. ii) State the uses of digested food in the bodies of animals Protection Repair Growth Energyproduction Name the types of food substances in the food that do not undergo digestion in humandigestive system mineral salts waterroughage vitamins k.) Explain the importance of the following food substances in human nutrition Vitamins are organic chemical compounds essential for a healthy body are obtained from fresh fruits and vegetables some are synthesized in the body e.g. vitamin K they are destroyed by overcooking food they protect the body against diseases, play regulatory mechanisms in the body and act as coenzymes insufficient amounts lead to deficiency diseases e.g. rickets, scurvy, beriberi Mineral salts are important in organic compounds containing elements which are essential for normal body metabolism those required in large quantities are called macro-nutrients while those required in small quantities are called micro-nutrients or traceelements They are used in bone and teeth formation. In osmotic balance and neurotransmission insufficient amounts lead to anaemia, rickets,goiter Excess amounts lead to high blood pressure, and dental disorders. Roughage composed of cellulose and plant fibers digested by cellulose contained by gut microorganisms provides grip essential for peristalsis lack of roughage leads to slow movement of food leading to constipation roughage adds bulk to food for peristalsis to take place Water used in transport in the body, universal solvent, hydrolysis insufficient leads to dehydration l.) Explain the factors that determine energy requirements in humans Basal Metabolic Rate (BMR) this is the energy required when the body is completely atrest used to carry out breathing, heartbeat, circulation of blood and other basicreactions also used in maintaining body temperature at constant all movements or physical work e.g. walking, eating required more energy. Occupation means activity occurring everyday everyday activity determines energy requirement People doing heavy work like digging require more energy than office workers. Age children carry out many activities and also have more cell division than adults their BMR is therefore higher than for adults as they grow older, they become less active and their energy requirements decrease Body size small bodied people have a large surface area to volume ratio their bodies lose more heat energy to the surrounding they therefore require more energy-giving foods this is the opposite for big bodied people Sex most males are more muscular than females they also do heavier work than females hence require more energy females do lighter work hence require less energy Climate in warm climate the body requires less energy in low temperatures the body requires more energy to maintain body temperature m.) Explain various tests carried out on food Test Procedure Observation Conclusion Starch - add iodine solution - colour changes to blue black/dark blue Present Reducing sugar Benedicts solution heat/boil/warm in hot water bath - colour changes to Green to yellow to orange to brown to red Present Non-reducing sugar Dilute HCL, NaHCO3, heat/boil, warm in hot water bath - colour changes to Green to yellow to orange to brown to red Present Proteins 1% CuSO4, 5% NaOH -- colour changes to purple/violet Present Ascorbic acid (Vitamin C) DCPIP drop wise DCPIP decolorized Present Fats/oils (lipids) rub on filterpaper ethanol translucentmark whiteemulsions present www.kcpe-kcse.com The other documents available on this website include;  All secondary school schemes of work. Form 1-form 4 revision papers in allsubjects. Marking schemes to most of the revisionpapers. K.C.S.E pastpapers. University pastpapers. K.A.S.N.E.B past papers e.g. C.P.A Primary school schemes ofwork. Primary school revision papers to allclasses. Marking schemes to primary school pastpapers. K.C.P.E pastpapers. Endemic - Diseases which occur in one region only

Diseases
Epidemic - Occurs when a diseases rapidly spreads through a large portion of a population

Pandemic - Occurs when an epidemic spreads across whole continents (ex AIDS)

Non-communicable Diseases - Diseases which are not infectious and are caused by factors like malnutrition, inheritance, environment or hormones

Examples of Non-communicable Diseases - Sickle-cell anemia,
 lung cancer, diabetes, marasmus, kwashiorkor, scurvy, rickets, night blindness, anemia

causes, transmission and prevention of various diseases-

Meningitis -
Causes
- Microorganisms such as viruses, bacteria or fungi

Transmission
- Direct contact with an affected individual or sharing of utensils

Symptoms
 - Swelling of the spinal and brain tissues

Prevention
- Vaccination, avoiding contact with infected individuals, use of preventive antibiotics


Cholera -
Causes
 - Bacteria called V. cholera found in water contaminated by feces from diseased carriers

 Transmissio
 - Through direct contamination of food or water by feces as a result of poor hygiene

 Symptoms
 - Watery diarrhea, vomiting excessively, body weakness, fast pulse, loss of body weight, severe dehydration, tightening of muscles with cramps in hands and feet

Prevention
- Provision of clean and safe drinking water, heating food to high temperatures, keeping food/drinks covered, washing hands before eating, wash fruits/vegetables in safe water, proper sewage treatment and sanitation, improve personal and public hygiene, proper use of toilets, treating carriers of the disease to break the cycle, vaccination

Effects
- Severe diarrhea, damage to cell lining in intestine, delay in treatment can lead to death

Malaria -
Causes
 - Four parasites of the genus plasmodium (P malaria, P vivax, P ovale, P falciparum)

Transmission
- Mosquitoes carry the plasmodium and infect humans by biting them

Symptoms
 - High fever, dizziness, joint pain, sometimes vomiting

Prevention
 - Attack the source, interrupt transmission, protect the host


Bilharzias (Schistomiasis)
 - Occurs in the abdomen or urinary tract

 Causes
- Caused by flatworms in the large and small intestine or urinary bladder

Transmission
- The worm lives in a snail until it produces larva which swim in a body of water and infect a human who is swimming there. They enter the water when a person with the worm urinates in the water

Symptoms
 - Pain and blood during urination due to the ulceration of the bladder and urethra, nausea, loss of appetite, blood in feces

Prevention
- Killing host snails, introduction of ducks to eat snails, destroy breeding places of snails, treat patients so the life cycle is broken, educating people on the importance of latrines and boiling water

Rickets -
Causes - Lack of vitamin D, common in children without access to vitamin D

Symptoms
 - Bone tenderness, dental problems, skeletal deformity

Prevention
 - Dietary supplements or more exposure to sunlight

Shock - Is a sudden loss of consciousness arising from the failure of blood to circulate properly to all body parts, especially the brain

Causes
 - Emotional stress, low blood pressure, illness (malaria or anemia), severe injury/blood loss

Syphilis -

Transmission
 - Sexually transmitted disease

Effects -
 Death of an unborn baby if syphilis is
transmitted to the baby, deafness of the baby, a person with syphilis can become blind or have heart disease

Typhoid -
Causes
 - Ingestion of contaminated water or food by the feces of an infected person which contain the salmonella bacteria

Symptoms
- High fever, sweating, diarrhea, inflammation of the GI tract

Prevention
 - Sanitation and hygiene to prevent people from eating or drinking contaminated food or water

Heart Burn
- A burning sensation in the chest caused by the regurgitation of gastric acid

Prevention of hearth burn
 - Use of medicine to stop the regurgitation of gastric acid

Ways of preventing malaria
 - Attacking the source, interrupting transmission, protecting the host
Attacking the source

 - Drain unwanted ponds and pools, clear bushes and grass around a living environment, introduction of animals which eat mosquitoes, do not leave standing water

Interrupting Transmission - Sleep under mosquito nets, use mosquito repellents and insecticides, burn mosquito coils to expel mosquitoes
Protect the Host

 - Effective treatment when sick, malaria prophylaxis like chloroquine or mephaquine


Diseases caused by bacteria

 - Tuberculosis, pneumonia, cholera, gonorrhea,
 syphilis,
throat infection,
diphtheria,
 salmonella (food poisoning),
 tetanus (lockjaw),
meningitis
 leprosy,
 botulism,
ringworm

Diseases caused by viruses
- AIDS,
measles,
rubella,
influenza (the flu),
polio,
 smallpox,
 herpes,
 mumps


Diseases caused by parasites
 - Malaria,
 bilharzias,
sleeping sickness,
 dysentery


Diseases caused by fungi
 - Ringworm,
 athlete’s foot,
thrush

Diseases transmitted by polluted water
- Cholera,
 typhoid fever,
schistosomiasis
 amoebiasis (amoebic dysentery),
bacterial dysentery


Diseases associated with uncooked food - All types of bacterial, viral and worm infections

Cause of fainting
 - Sudden drop of blood pressure

Anorexia Nervosa
 - An obsessive desire to lose weight by eating very little food

Emphysema
- Thinning of the lung tissue leading to the rupture of alveoli. Caused by smoking

Hypothermia
 - The cooling of the body until it is well below the normal 37°C

Meningitis - Inflammatory condition

Pathology - The scientific study of the effects on the body of disease

Shock
 - Is a sudden loss of consciousness arising from the failure of blood to circulate properly to all body parts, especially the brain

Vaccine
 - A suspension of dead, inactivated or harmless germs which when introduced to the blood stream stimulates the production of antibodies and makes the body immune to attack from that disease

HIV/AIDS andSTDs
HIV - The virus which causes AIDS.
 It is transmitted by
 unsafe sex with an infected person,
 blood transfusion,
sharing of needles by drug users

AIDS (Acquired Immunodeficiency Syndrome) - A disease caused by a virus which damages the immune system so that humans are unable to fight disease

Ways to contract HIV
 - Unsafe sex,
sharing of needles,
breast milk,
 transmission by mother to baby at birt

Ways not to contract HIV
 - Hugging,
 touching,
kissing,
 mosquitoes,
swimming with an infected person

Care and support forPWLH

How to care for those with HIV/AIDS - Clinical care, social care

Clinical Care
 - Preventative care with antibiotics,
insecticide treated nets,
 improving quality of drinking water,
good hygiene practices,
 nutritional counseling

Social Care
 - Avoiding segregation of HIV victims,
provide counseling,
 family support groups,
encouraging them not to spread HIV,
encourage physical exercise

Ways to care for HIV/AIDS patients
 - Avoiding stigmatization,
provide balanced diet,
support them mentally/physically/socially/financially,
 love them,
 clean their living environment,
send them to health centers for treatment and ARVs