(a) Define the term Denature as used in enzymes. (1 mark)

Denature change in protein structure so that some of its original properties/configuration stop functioning;

(b) (i) Optimum temperature 36⁰C 1; (ii) At 450 C time taken is more than at 350 C because the enzymes/pepsin is being denatured;

(c) (i) Pepsinogen; (ii) Digest stomach/digest lumen in its active form (pepsin) in absence of protein food;

(d) Epidermal tissue; Parenchyma; Sclerenchyma; Xylem tissue; Cholenchyma;

(e) Provides surface on which food/grass is pressed and cut:

(a) Food chain is a linear flow of energy from a producer to a consumer food web is inter- relationship between food chains;

(b) Organisms-grass; Reason organisms depend on for food. respiration

(d) Increased composition for grass with other primary consumer (locust/antelopes/caterpillar);

(e) Secondary consumer /3rd trophic level;

(f) Decomposition/decay;

(a) Loop of Henle;

(b) It increases the osmotic gradient; this forces water out of the collecting duct by osmosis or diffusion; this increases water reabsorption from the collecting duct;

(c) Proximal convoluted tubule/Distal convoluted tubule;

(d) Low sodium concentration increase aldosterone hormone secretion, stimulate reabsorption of chloride;

(e) Ultrafiltration

(a) (i) A stem; - Transport water and mineral salts/manufactured food;/support;

- B cotyledon; rej seeds. - Stores food/protect the plumule/photosynthesis;

(ii) Epigeal;

(b) (i) Respiration/oxidation/breakdown of food substances to provide energy for germination;

(ii) Soften the seed coat/testa /A solvent for stored food substances/medium for enzymes action/keep cells turgid /medium of transport;

(iii) Optimum temperature required for enzymes activity/it activates enzymes;

(a) X- Vacuole/Sap vacuole;

Y-Tonoplast; Z-Chloroplast;

(b) Cellulose;

(c) Active transport;

(d) The cell sap is hypertonic to the solution/distilled water; hence water molecules move into the cell; by osmosis; making it to swell and eventually burst;

(c) Bigger body size, small surface area volume ratio; hence loss less heat to the surroundings; require less energy to compensate for less energy lost; (d) Extra polation; 2.5 kg;

(e) (i) Lower; (iireptiles have poikobilotherms does not requireenergy to maintain body temperature;

(f) -Activity/occupation;

• Sex;
• Age; o State of health;
• (g) Proteins; (h) Provide grip hence prevent constipation; add bulk to the food;

Describe how the mammalian heart is adapted to its function:

- It has myogenic/cardiac muscles; which contract and relax rhythmically without fatigue (hence continuous pumping)

- Cardiac muscles fibres are interconnected to form network of fibres;to ensure rapid and uniform spread of excitation throughout the walls of the heart; - The heart is divided into four chambers (which are hollow);to accommodate a lot of blood;

- Ventricles wall are thicker than auricle walls; to generate higher pressure to pump blood over longer distance;

- There is a (longitudinal)septum; which separate it into two halves to prevent mixing of (the more) oxygenated blood and the less oxygenated blood/deoxygenated blood;

- It has valves; which prevents backflow of blood;

- Valves are connected with (tough strands of) connective tissue/chordae tendinae/tendons; prevent them from being pushed inside out when ventricles contracts/turning inside out;

- The heart is joined by blood vessels/aorta,vena cava, pulmonary vein, pulmonary artery);which channel blood to and from all body parts; - It has the coronary artery and coronary vein which supply the mycocardium with oxygen and nutrients; remove waste products respectively;

- The fibrous layers of pericardium surrounds the Herat; which keeps the heart in position and prevent over-dilating;

- The inner layer of pericardium secretes pericardiac fluid; which reduce friction between the two layers during systole and diastole; - Outer layer pericardium; is surrounded by a layer of fats; to act as shock absorbers protecting it from mechanical damage;

- It has Sino artricole node (SAN);to acts as pacemaker by regulating rate of beating and excitation of the heart; - Has nerves/vagus nerve and sympathetic nerve; which regulate heartbeat;

Discuss the role of plant hormone in growth and development. (20 marks)

Auxins/IAA; - Induces pattenocarpy in horticulture;

- Stimulates growth of adventitious roots in cuttings for vegetative, propagation;

- Stimulates cell division and elongation in shoots; promotes growth in stem;

- Selective weed killers; - Inhibits formation of side branches by removing apical bud; used in pruning tea, coffee; - Ripening of fruits;

- Induces leaf fall leaf abscission;
Gibberellins/Gibberellic acid;
- Stimulation of rapid growth; dwarf variety to grow to normal height by cell elongation/cell division;

- Stimulate growth side branches;

- Inhibit growth of adventurous roots;
Cytokinins;
- Promote cell division in presence of auxin(and growth in plant);

- Breaks seed dormancy; - Repair of wounds in plants/cellus tissue;

- Promotes flowering;retards aging;

- Promotes fruit growth;
Absissic acid;
- Promotes fruits fall;

- Promotes leaf fall/leaf abscission;

- Prevents seeds from germinating/dormancy of buds;

- Growth inhibitor;
Ethene;
- Ripening of fruits; - Causes leaf fall/abscission;

- Breaks dormancy in seeds/bud;