Mastering KCSE Biology with Comprehensive Topical Questions and Answers
A group of students set up an experiment to investigate a certain physiological process. The set up
|
Ions | Concentration in pond water | Concentration in cell |
Sodium | 50 | 30 |
Potassium | 2 | |
Calcium | 15 | 1 |
Chloride | 180 | 200 |
(i) Sodium ions
(ii) Potassium ions
(b) For each processes named in (a) (i) and (ii) above, state one condition necessary for the process to take place.
K.C.S.E Biology Q & A - MODEL 2019PP1QN11
(a) sportsmen release little, concentrated urine at the end of a strenuous exercise
(b) a rabbit has a higher oxygen demand than a camel
(b) a rabbit has a higher surface area to volume ratio/ smaller in size hence has a bigger surface area exposed to heat loss to the environment/ lose heat faster/ its more active than the camel; hence need more oxygen to(aerobically) respire (to synthesize the needed energy to support its activity /lifestyle;
K.C.S.E Biology Q & A - MODEL 2019PP1QN04
(b) Account for the observation made at the end of the experiment.
(c) State the likely identity of G.
(b) solution E is hypertonic/ had more solute molecules compared to solution F; solution F hypotonic to solution E; by osmosis water molecules move through the semi- permeable membrane G (from solution F to E); hence decreases in volume of F/ increased solution E;
(c) semi permeable membrane /visking tubing /slice of potato /pawpaw (any other permeable plant tissue) pig bladder/cellophane paper/dialysis membranes.
K.C.S.E Biology Q & A - MODEL 2018PP1QN04
(a) What biological process were they investigating?
(b) Name the structures from which the air bubbles were coming from.
(c) Explain the distribution of the structures named in (b) above on the leaf surfaces of a land plant.
b) Stoma/somata;
c) Are more on the lower surface of terrestrial plants/fewer on the upper surface; to reduce transpiration;
K.C.S.E Biology Q & A - MODEL 2017PP1QN21
- Differences in distribution of chlorophyll/leaf is variegated; green patches would photosynthesize forming starch; giving blue-black colour with iodine solution unlike the regions without chlorophyll;
Explain the physiological process responsible for keeping young seedlings upright.
- Osmosis; water moves into the cells becoming turgid; attaining mechanical support ;
K.C.S.E Biology Q & A - MODEL 2017PP1QN11
(ii) Give two examples of the process named in (a) (i) above in plants.
(b) State two ways by which the movement of dye molecules in the set up would be slowed down.
ii) Gaseous exchange/excretion of carbon (IV) oxide and oxygen;
Translocation of materials;
Absorption/uptake of mineral ions/salts;
b. Lowering the temperature of the medium;
Increasing thickness of the membrane;
Use less dye/add more water/reducing the concentration gradient;
K.C.S.E Biology Q & A - MODEL 2016PP2QN06
(b) When was the rate of reaction 2.6 mg of product per unit time?
(c) Account for the shape of the graph between:
(i) 5Ā°C and 40Ā°C
(ii) 45Ā°C and 60Ā°C
(d) Other than temperature name two ways in which the rate of reaction between 5Ā°C and 40Ā°C could be increased.
(e)(i) Name one digestive enzyme in the human body which works best in acidic condition.
(ii) how is the acidic condition for the enzyme named in (e) (I) above attainedā?
(f) The acidic condition in (e) (iii) above is later neutralized.
(i) Where does the neutralization take place?
(ii) Name the substance responsible for the neutralization.
32.5 - 33.5 and 51.0 ā 52.0
(c) (i) 5Ā°C and 40Ā° C
As temperature is increased rate of reaction is increased/ more products are formed (per unit time) because enzymes become more active
(ii) 45Ā° C and 60Ā° C
As temperature increase rate of reaction decreases less/products are formed (unit per time) because enzymes become denatured by high temperatures above 40, hence cannot act on substrate.
(d) Increase in enzyme and substance concentration
Use of co-factors and co-enzymes
(e) (i) Pepsin,
Chymosin
Renin
(ii) Wall of stomach/ gastric gland/ oxyntic/ pariental/ cell produced Hydrochloric
(f) (i) Duodenum
(ii) Bile juice/ e.g. NaHCO3
K.C.S.E Biology Q & A - MODEL 2016PP2QN05
(b) Suite the significance of the biological process involved in the experiment.
L2 - Inner cells lost water by osmosis; leading to (flaccidity) decrease in length; epidermal cells did not lose water due to waterproof leading to curvature
(b) Absorption of water by the roots
Opening and closing of the stomata
K.C.S.E Biology Q & A - MODEL 2015PP1QN06
(b) State the importance of the physiological process investigated in plants.
(c) Explain the observations made after 30 minutes.
(b) Absorption of water from the soil; opening and closing of stoma; feeding in insectivorous plants; support (in seedlings, leaves,herbaceous plants);
Movement of water from cell to cell in plants.
(c) The thistle funnel gained water by osmosis; because the sucrose solution was hypertonic;
K.C.S.E Biology Q & A - MODEL 2014PP1QN10
(i) Crenated cell.
(ii) Flaccid cell.
(ii) Flaccid cell is a flabby /shrunk plant cell that has lost waster by osmosis;
Explain two roles of diffusion in human beings.
- Absorption of materials e.g. diffusion of digested food into the blood stream;
- Gaseous exchange e.g. CO2,/O2, diffuses from capillaries into the alveoli.
- Excretion of nitrogenous wastes; e.g. urea diffuses from blood capillaries into the elimination sites.
K.C.S.E Biology Q & A - MODEL 2014PP1QN05
(b) Explain the observation made on the set up after one hour.
State two ways in which osmosis is significant to plants.
- Absorption of water; support;
- Opening and closing of stomata;
- Feeding in insectivorous/plants;
Describe how turgor pressure builds up.
- As the cell gains water by osmosis; the sap/cellvacuole enlarges; pushing the cytoplasm outwards; exerting pressure on the cell wall;
Explain how an increase in temperature affects the rate of active transport.
- The rate of active transport increases with increase intemperature up to the optimum temperature;
- Further increase in temperature slows down the rate of active transport until it stops because it denatures enzymes;
K.C.S.E Biology Q & A - MODEL 2012PP2QN03
(ii) Name the gas produced in this investigation.
(iii) Account for the results in test-tubes H and J.
(b) State two ways in which the human intestinal villus is adapted to its function.
(ii) oxygen; (1 mark)
(iii) Test tube H is at optimum temperature for enzyme activity; hence high rate of
photosynthesis/more bubbles. In test tube J most enzymes have been denaturedby the high temperature; hence low rate of photosynthesis/fewer bubbles.
(b) ā The villus epithelium is thin; for faster diffusion of dissolved food substances;
ā The epithelium has goblet cells; which produce mucus to lubricate food passage;
ā They have microvilli; which further increase their surface area for absorption;
Have lacteal; for absorption of fatty acid & glycerol/transportation of lipids;
Highly vascularised; for absorption of digested food.
K.C.S.E Biology Q & A - MODEL 2012PP1QN16
- The plant/flower is self sterile/not successfully self pollinated; covering prevents pollination; in flower P. Flower Q received pollen from other plants/cross pollination;
State three factors that affect the rate of diffusion.
K.C.S.E Biology Q & A - MODEL 2012PP1QN07
(b) State the role of potassium hydroxide in flask K.
(c) Account for the observation in boiling tube L and flask N.
L .
N
(b) Flask K Potassium hydroxide removes Carbon IV Oxide from atmospheric air;
(c) L - Lime water remains clear because Carbon (IV) Oxide has been removed;
Flask N lime water forms a white precipitate because the respiring cockroaches produce Carbon (IV) Ovide;
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