KNEC KCSE BIOLOGY TOPICAL QUESTIONS AND ANSWERS

During a practical investigation on food tests, students were provided with the following reagents.
Benedict’s solution
Sodium hydrogen carbonate
Dilute hydrochloric acid.

(a)Identify the food substance the students were to test.
(b) State the role of dilute hydrochloric acid and sodium hydrogen carbonate during the experiment.
(i) Dilute hydrochloric acid
(ii) Sodium hydrogen carbonate

answers

a) Non reducing sugar;
b) (i) Hydrolyze/break down sucrose! non reducing sugars to reducing sugars/glucose/fructose;
(ii) neutralize the acid;

Comments

How does nutrition as a characteristic of living organisms differ in plants and animals?

30/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP1QN24

How does nutrition as a characteristic of living organisms differ in plants and animals?

answers

Plants make their own food from carbon (IV) oxide and water in the presence of light /photosynthesize/ autotrophic; while animals eat readymade food (some plants and animals heterotrophic;
If photosynthesis described all raw materials must be mentioned;
Carbon (IV) oxide the (IV) must be bracketed.
If sources of food for animals are mentioned then both plants and animals must appear.

Comments

State two functions of saliva.

30/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP1QN23

State two functions of saliva.,

answers

Lubricating food;
Digestion of starch;
Moistens food; Provides alkaline medium;
Softens food/ Dissolves food.

Comments

State two factors that affect enzymatic activities

30/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2016PP1QN13

State two factors that affect enzymatic activities

(b)Explain how one of the factors stated in (a) above affects enzymatic activities.

answers

Temperature PH co- factors, co- enzymes; enzyme product concentration; substance concentration/ metabolic poison

(b)

Temperature- increase in temperature increases rate of enzymatic activity upto an optimum
Low temperature decreases enzymatic activity/ too high temp above optimum point denatures enzymes.
Ph- Enzymes work best at optimum ph/extreme ph denatures enzymes.
Enzyme conc – Increase in conc. increase enzymatic activity.
Co- enzymes – complements enzymes increasing rate of activity
Substrate concentration increase enzymatic activity up to certain level.

Comments

K.C.S.E Biology Q & A - MODEL 2015PP1QN17

29/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2015PP1QN17

How is a human stomach adapted to
(i) protein digestion?
(ii) churning?

answers

(i) Has gastric glands; that secrete gastric juice;
(ii) Thick muscular wall; that contract and relax;

Comments

Describe the process of carbohydrate digestion in human beings.

28/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2014PP2QN07

Describe the process of carbohydrate digestion in human beings.

answers

In the mouth;

Food is chewed; to increase surface area for enzyme activity/saliva contains salivary amylase;
Saliva mixes with food and provides an alkaline medium; for amylase enzymes;
Salivary amylase acts on starch and converts them to maltose;

In duodenum;

Food is mixed with bile; and pancreatic juice;
Bile provides alkaline medium; for activity of duodenal enzymes; and neutralizes acidic
chyme from the stomach;
Pancreatic juice contains pancreatic amylase; which converts starch to maltose;

In the Ileum;

Epithelial cells in Ileum secrete succus entericus; which contains enzymes;
sucrase; which acts on sucrose and converts it to fructose and glucose;
Lactase; which acts on lactose and converts it to galactose and glucose;
Maltase; acts on maltose and converts it to glucose;

Comments

K.C.S.E Biology Q & A - MODEL 2014PP1QN26

28/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2014PP1QN26

The table provided shows the concentration of sodium and iodine in sea water and cell sap of a plant.

(a) (i) Name the process through which the plant cells take up sodium ions.
(ii) Give a reason for your answer in (a) (i) above.
(b) If the plant was sprayed with a chemical that inhibits respiration:
(i) which of the two ions uptake will be affected’?
(ii) give a reason for your answer in (b) (i) above.

ANSWERS

(a) (i) Diffusion;
(ii) Sea water contains a higher concentration of sodium ions than the cell sap;
(b) (i) Iodide ions;
(ii) Sea water has a lower concentration of iodide ions than the cell.
The plant requires energy to take up the iodide ions (by active transport);

Comments

K.C.S.E Biology Q & A - MODEL 2013PP2QN03

28/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2013PP2QN03

(a) Explain the importance of the following in photosynthesis:
(i) light;
(ii) carbon(IV) oxide;
(iii) chlorophyll.

(b) Name one appropriate food substance for each of the following enzymes:
(i) ptyalin
(ii) pepsin
(c) State the cause and two symptoms of Ben-ben.
Cause
Symptoms

answers

(a) (i) Provides energy needed to split water molecules into oxygen and hydrogen/photolysis;
Provides energy for formation of ATP molecules (which is used in dark stage)
(ii) Combines with hydrogen ions to make glucose;
(iii) Used to trap light energy;
(b) (i) Starch;
(ii) Protein;
(c) (i) Lack of vitamin B1/thiamine;
(ii) . Stunted growth;
Paralysis of legs/arms/limbs/damage to peripheral nerves;
Heart failure
Swelling of feet/oedema
Gastrointestinal disturbances/loss of appetite/constipation/diarrhoea/vomiting;
Weight loss/muscle wasting
Pale skin

Comments

Explain how age determines a person’s energy requirements.

26/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2013PP1QN04

Explain how age determines a person’s energy requirements.

answers

Young people are more active; requiring more energy;/older people are less active; requiring less energy;

Comments

State two roles of mucus in the stomach.

26/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2013PP1QN04

State two roles of mucus in the stomach.

answers

Lubrication;
Protection;

Comments

Name two nutrients that are absorbed without being digested by enzymes in humans.

26/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2012PP1QN29

Name two nutrients that are absorbed without being digested by enzymes in humans.

answers

Water;
mineral ions;
vitamins

Comments

How does nutrition as a characteristic of living organisms differ in plants and animals?

26/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2012PP1QN01

How does nutrition as a characteristic of living organisms differ in plants and animals?

answers

Plants make their own food from Carbon (IV) Oxide and water in the presence of light autotrophic/ photosynthesis; while animals eat ready made food from plants or animals/heterotrophic nutrition;

Comments

State two functions of saliva.

25/6/2020

Comments

K.C.S.E Biology Q & A - MODEL 2011PP1QN18

State two functions of saliva.

answers

Lubricating food; digestion of starch; moisten food; provide alkaline medium;

Comments

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How is the surface area increased in the mammalian small intestines?

How is the surface area increased in the mammalian small intestines?

Name two enzymes in the human digestive system which are secreted in an inactive form.

Name two enzymes in the human digestive system which are secreted in an inactive form.

K.C.S.E Biology Q & A - MODEL 2017PP1QN03

K.C.S.E Biology Q & A - MODEL 2017PP1QN03

How does nutrition as a characteristic of living organisms differ in plants and animals?

How does nutrition as a characteristic of living organisms differ in plants and animals?

State two functions of saliva.

State two functions of saliva.,

State two factors that affect enzymatic activities

State two factors that affect enzymatic activities

K.C.S.E Biology Q & A - MODEL 2015PP1QN17

K.C.S.E Biology Q & A - MODEL 2015PP1QN17

Describe the process of carbohydrate digestion in human beings.

Describe the process of carbohydrate digestion in human beings.

K.C.S.E Biology Q & A - MODEL 2014PP1QN26

K.C.S.E Biology Q & A - MODEL 2014PP1QN26

K.C.S.E Biology Q & A - MODEL 2013PP2QN03

K.C.S.E Biology Q & A - MODEL 2013PP2QN03

Explain how age determines a person’s energy requirements.

Explain how age determines a person’s energy requirements.

State two roles of mucus in the stomach.

State two roles of mucus in the stomach.

Name two nutrients that are absorbed without being digested by enzymes in humans.

Name two nutrients that are absorbed without being digested by enzymes in humans.

How does nutrition as a characteristic of living organisms differ in plants and animals?

How does nutrition as a characteristic of living organisms differ in plants and animals?

State two functions of saliva.

State two functions of saliva.

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