KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

The equation below represents a process in a mammalian liver

31/10/2021

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The equation below represents a process in a mammalian liver

(a) Name the process shown by the equation above (1mk)

Deamination;

(b) List down a carbohydrate that is;-

(i) Stored in the mammalian liver (1mk)

Glycogen;

(ii) Found in abundance in mammalian blood (1mk)

Glucose;

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Name two functions of sodium in human body

30/10/2021

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Name two functions of sodium in human body (2mks)

Formation of the harmone thyropine;
Nerve impulse transmission;

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State the role of light in photosynthesis

30/10/2021

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State the role of light in photosynthesis (1mk)

Photolysis/provides energy required for splitting water molecules into hydrogen ions and oxygen gas;

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Explain the role of enzymes in living cells

16/9/2021

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(a) Explain the role of enzymes in living cells (1mk)

Enzymes speed up/slows down the rate of chemical reaction/metabolism in the body; without being used up

(b) The graph below shows the effects of temperature on the rate of reaction of the enzymes salivary amylase

The graph above shows the effects of temperature on the rate of reaction of the enzymes salivary amylase

(i) Account for the changes in the curve between C and D (1mk)

The rate of reaction decrease/drop as temperature increase (beyond 40 degrees C) due to denaturation of enzymes

(ii) What does the dotted line represent? (1mk)

Normal human temperature/the optimum for the enzyme salivary amylase

(c) Explain how the following factors affect the rate of enzyme activity
(i) Temperature (2mks)

Enzyme are proteinous in nature; are sensitive to temperature, changes/ work best within narrow range of temperature /have maximum activity at optimum temperature; temperatures above optimum destroy enzymes structure/denature enzyme while those below optimum lower enzyme activity due to inactivation enzymes.

(ii) Substrate concentration (2mks)

Increases in substrate concentration increases enzyme activity up to a certain level; this is due to an increase in the number of active sites; until all active sites of the enzyme are occupied.

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The diagram below shows a tip of a plant coleoptile with light coming towards it from one side

11/9/2021

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The diagram ABOVE shows a tip of a plant coleoptile with light coming towards it from one side

(a) How would the plant respond to light? (1mk)

by bending/curving

(b) Give the name of such response (1mk)

positive phototropism

(c) What is the advantage of plants responding in this way? (2mks)

exposes the leaves in position to maximize light absorption hence enhancing photosynthesis

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The set up below shows apparatus to demonstrate a certain biological process

7/9/2021

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(a) What biological process was being investigated in the experiment (1mk)

Gas produced during anaerobic respiration

(b)Write down a word equation that represents the reaction above (1mk)

Glucose > Ethanol + Carbon (IV) oxide +Energy

(c) In the above set up, why was it important to boil and cool glucose before adding yeast? (1mk)

To remove O2; cooling to provide suitable temperature for enzymatic reactions/ avoid destroying/killing yeast

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Give two destinations of food translocated from the leaves of plants

5/9/2021

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Give two destinations of food translocated from the leaves of plants. (2mks)

To roots/stems for storage
Oxidizes to produce energy
Converted into fats and oils
Converted into cellulose to make new cell walls

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Most terrestrial plants do not grow well in waterlogged soils. Give a reason for this

5/9/2021

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Most terrestrial plants do not grow well in waterlogged soils. Give a reason for this (1mk)

Lack of O₂for respiration

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Nutrition in Plants and Animals Questions and Answers

8/11/2020

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NUTRITION IN PLANTS AND ANIMALS

The diagram below shows chemical reactions I, and II which are controlled by enzymes respectively.

1. 1989 Q1 P1

Name reaction II and enzyme B

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K.C.S.E Biology Q & A - MODEL 2019PP2QN06

2/7/2020

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K.C.S.E Biology Q & A - MODEL 2019PP2QN06

The table below shows the rate of product formation for two enzymes, H and J over a range of pH values

(a) On the same axis, plot graphs of the rate of product formation against pH.
GRAPH PAPER
(b) Account for the rate of product formation for enzyme H between:
(i) pH 1.0 and 3.0
(ii) pH 3.0 and 7.0.
(c) From the graph, determine: .
(i) the pH value at which the rate of product formation of the two enzymes was the same
(ii) the value of the rate of product formation for enzymes H and J at the pH value stated in (c)(i) above
(iii) the optimum pH value for enzyme J
(d) State one variable that may lead to the change in the optimum rate of product-formation of the two enzymes.
(e) Suggest with a reason, the likely part of the human alimentary canal where enzyme H would be found.

answers

(b) (i) Rate of product formation increases with the increase in pH to the optimum then decreases;
   pH 5 is the optimum pH value for activity of enzyme H; between pH 1 and 2 enzyme H/enzyme molecules are activated; Between pH 2 and 3 enzyme H (enzyme molecules) are denatured/destroyed; (. Enzyme is inactivated/ less active for denatured
(ii) Rate of product formation (sharply) decreases with increase in pH; Enzyme H is (not formed by increase in pH hence is denatured); No product forms above pH 4.0 to 7.0; because all enzymes (enzyme molecules) are denatured;
(c) (i) 4.0
   (ii) 15.0 mg/hr
    (iii) 7.0
(d) -Temperature
-Substrate concentration;
-Enzyme concentration;
-Cofactors
-Co-enzymes
-(Enzyme) inhibitors
(e) Stomach;
Acidic medium/Low pH

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K.C.S.E Biology Q & A - MODEL 2019PP1QN19

2/7/2020

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K.C.S.E Biology Q & A - MODEL 2019PP1QN19

Below is a diagram of the human digestive system.

(a) Label with Y on the diagram where enzyme amylase is produced.
(b) Besides the digestive role, explain one other function of the part labelled H.

answers

(b) Endocrine function/secrets (insulin/ glucagon) hormones; responsible for blood sugar regulation;

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Name the type of tooth in carnivores mainly used for piercing and killing of preys.

2/7/2020

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K.C.S.E Biology Q & A - MODEL 2019PP1QN18

Name the type of tooth in carnivores mainly used for piercing and killing of preys.

answers

canine acc. canines

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Distinguish between chemical and mechanical digestion.

1/7/2020

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K.C.S.E Biology Q & A - MODEL 2019PP1QN07

Distinguish between chemical and mechanical digestion.

answers

chemical digestion entails the action on / broken down of ingested food materials (in the alimentary canal) by the action of digestive enzymes (and converted into form that can be easily absorbed or assimilated in to the body system)while mechanical digestion refers to physical break down of(large) food molecules (into smaller form or pieces )which can subsequently be acted upon by digestive enzymes

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Describe what happens to a meal rich in proteins along the alimentary canal from ingestion to egestion.

1/7/2020

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K.C.S.E Biology Q & A - MODEL 2018PP2QN08

Describe what happens to a meal rich in proteins along the alimentary canal from ingestion to egestion.

answers

The meal is ingested through the mouth; (In the mouth), it is chewed/masticated (by teeth); to reduce/break it into smaller particles; mixed with saliva (from salivary gland);
The food is then rolled (by the tongue) into boluses; and pushed down into the oesophaghus/swallowed; The boluses move by peristalsis (into the stomach);
Constant contractions/relaxations of the stomach walls mix the food, (giving rise to chime); Presence of food in the stomach further stimulates production of gastric juice; which contains pepsinogen; and rennin/chymosin; Pepsinogen is activated to pepsin; by hydrochloric acid; (contained in the gastric juice). Pepsin breaks down proteins to peptides;
Rennin converts/coagulates the protein, caseinogen; in milk to casein; (which is abundant in young children). It is then pushed into the duodenum (through the pyloric sphincter); Pancreatic juice in the duodenum contains trypsin; which digests proteins into peptides; (secreted in an inactive form, trypsinogen)
In the ileum, intestinal juice/Succus enfericus is secreted; It contains peptidase enzymes; which breaks down polypeptides into amino acids; It also contains polypeptidase enzyme; which breaks down peptides to amino acids,completing the process of digestion of the proteins;
The amino acids are absorbed into the bloodstream/pass through the epithelia of the villi, and the capillary walls into the blood-stream; by active transport;
The undigested/indigestible proteins/food substances pass through to the colon/large intestines; where water is absorbed; leaving a semi-solid waste material being passed on to the rectum; then out through the anus (as faeces);

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Which sets of teeth would be used in chewing sugarcane for maximum extraction of sap?

1/7/2020

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K.C.S.E Biology Q & A - MODEL 2018PP1QN03

Which sets of teeth would be used in chewing sugarcane for maximum extraction of sap?

answers

Premolars; molars;

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<<Previous

​(a) Name the process shown by the equation above (1mk)

​(b) List down a carbohydrate that is;-

(i) Stored in the mammalian liver (1mk)

(ii) Found in abundance in mammalian blood (1mk)

Name two functions of sodium in human body (2mks)

​State the role of light in photosynthesis (1mk)

​(a) Explain the role of enzymes in living cells (1mk)

​(b) The graph below shows the effects of temperature on the rate of reaction of the enzymes salivary amylase

​(i) Account for the changes in the curve between C and D (1mk)

​(ii) What does the dotted line represent? (1mk)

​(c) Explain how the following factors affect the rate of enzyme activity (i) Temperature (2mks)

​(ii) Substrate concentration (2mks)

​(a) How would the plant respond to light? (1mk)

​(b) Give the name of such response (1mk)

(c) What is the advantage of plants responding in this way? (2mks)

(a) What biological process was being investigated in the experiment (1mk)

(b)Write down a word equation that represents the reaction above (1mk)

(c) In the above set up, why was it important to boil and cool glucose before adding yeast? (1mk)

​Give two destinations of food translocated from the leaves of plants. (2mks)

​Most terrestrial plants do not grow well in waterlogged soils. Give a reason for this (1mk)

NUTRITION IN PLANTS AND ANIMALS

​The diagram below shows chemical reactions I, and II which are controlled by enzymes respectively.

K.C.S.E Biology Q & A - MODEL 2019PP2QN06

K.C.S.E Biology Q & A - MODEL 2019PP1QN19

Name the type of tooth in carnivores mainly used for piercing and killing of preys.

Distinguish between chemical and mechanical digestion.

Describe what happens to a meal rich in proteins along the alimentary canal from ingestion to egestion.

Which sets of teeth would be used in chewing sugarcane for maximum extraction of sap?

TOPICS

Form 2

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(a) Name the process shown by the equation above (1mk)

(b) List down a carbohydrate that is;-

State the role of light in photosynthesis (1mk)

(a) Explain the role of enzymes in living cells (1mk)

(b) The graph below shows the effects of temperature on the rate of reaction of the enzymes salivary amylase

(i) Account for the changes in the curve between C and D (1mk)

(ii) What does the dotted line represent? (1mk)

(c) Explain how the following factors affect the rate of enzyme activity
(i) Temperature (2mks)

(ii) Substrate concentration (2mks)

(a) How would the plant respond to light? (1mk)

(b) Give the name of such response (1mk)

Give two destinations of food translocated from the leaves of plants. (2mks)

Most terrestrial plants do not grow well in waterlogged soils. Give a reason for this (1mk)

The diagram below shows chemical reactions I, and II which are controlled by enzymes respectively.