3. RESPIRATION/ TISSUE RESPIRATION/
INTERNAL RESPIRATION
1
Respiration is the chemical process by which b) State two situations in plants when the
food substances are chemically broken down in rate of respiration rises more than
all living cells to release heat energy, carbon normal
(IV) oxide, water, alcohol/lactic acid. During germination.
Respiration takes place in the mitochondria During rapid growth/ cell division.
slowly and is controlled by respiratory enzymes During active uptake/ transport of substances/
so that energy is produced continuously and in mineral salts.
small amounts.
This prevents cells from burning up if all the
Significance/ importance of respiration.
energy in the food were to be released all at It produces energy which is used for:
once. a) Muscular contraction.
Gaseous exchange is the physical exchange b) Conduction of nerve impulses.
of gases across the respiratory surfaces. c) Secretion of enzymes and hormones.
Study question 1. d) Growth and repair of worn out tissues.
What is the difference between respiration and e) Functioning of body organs e.g. kidney, heart,
gaseous exchange? brain.
Study question 2 f) Active uptake of nutrients.
a) Explain why plants have lower g) Digestion of food e.g. peristalsis, absorption
respiratory rates compared to animals of digested food, chewing, churning,
Plants are less active than animals hence require secretion of mucus/ digestive enzymes
less energy than animals.
© Sam obare 13-May-21
, Practical activity
2
Aim Procedure.
To investigate what gas is given off 1. Place some food sample in a dry
when food is burnt. boiling tube.
Requirements. 2. Hold the test-tube containing the
i. Starch powder/crushed food sample horizontally.
beans/maize flour/milk powder. 3. Pour a little calcium hydroxide
ii. Test-tube. solution (lime water) into another
iii. Boiling tube. test-tube and support it.
iv. Calcium hydroxide solution(lime 4. Using a delivery tube connect the
water). boiling tube to the test tube
ensuring the free end of the
v. Rubber stopper. delivery tube dips into calcium
vi. Anhydrous blue cobalt chloride hydroxide solution/ lime water.
paper.
vii. Source of heat, delivery tube.
viii. Retort stand.
© Sam obare 13-May-21
, 3
5. Heat the boiling tube containing Observation and conclusion.
the food sample strongly. When food is burnt, carbon (IV)
6. Observe and record what happens oxide is produced which turns lime
to the food sample, calcium water milky.
hydroxide solution and the upper Water vapour is also produced that
sides of the boiling tube with the accumulate on the inner upper side
food sample. of the test tube which turns
7. Disconnect the apparatus and rub anhydrous cobalt (II) chloride paper
anhydrous blue cobalt (II) pink.
chloride paper on the inner upper
side of the test-tube containing
the food sample.
8. Record the colour change
observed on the blue cobalt (II)
chloride paper.
© Sam obare 13-May-21
, © Sam obare 4 13-May-21
INTERNAL RESPIRATION
1
Respiration is the chemical process by which b) State two situations in plants when the
food substances are chemically broken down in rate of respiration rises more than
all living cells to release heat energy, carbon normal
(IV) oxide, water, alcohol/lactic acid. During germination.
Respiration takes place in the mitochondria During rapid growth/ cell division.
slowly and is controlled by respiratory enzymes During active uptake/ transport of substances/
so that energy is produced continuously and in mineral salts.
small amounts.
This prevents cells from burning up if all the
Significance/ importance of respiration.
energy in the food were to be released all at It produces energy which is used for:
once. a) Muscular contraction.
Gaseous exchange is the physical exchange b) Conduction of nerve impulses.
of gases across the respiratory surfaces. c) Secretion of enzymes and hormones.
Study question 1. d) Growth and repair of worn out tissues.
What is the difference between respiration and e) Functioning of body organs e.g. kidney, heart,
gaseous exchange? brain.
Study question 2 f) Active uptake of nutrients.
a) Explain why plants have lower g) Digestion of food e.g. peristalsis, absorption
respiratory rates compared to animals of digested food, chewing, churning,
Plants are less active than animals hence require secretion of mucus/ digestive enzymes
less energy than animals.
© Sam obare 13-May-21
, Practical activity
2
Aim Procedure.
To investigate what gas is given off 1. Place some food sample in a dry
when food is burnt. boiling tube.
Requirements. 2. Hold the test-tube containing the
i. Starch powder/crushed food sample horizontally.
beans/maize flour/milk powder. 3. Pour a little calcium hydroxide
ii. Test-tube. solution (lime water) into another
iii. Boiling tube. test-tube and support it.
iv. Calcium hydroxide solution(lime 4. Using a delivery tube connect the
water). boiling tube to the test tube
ensuring the free end of the
v. Rubber stopper. delivery tube dips into calcium
vi. Anhydrous blue cobalt chloride hydroxide solution/ lime water.
paper.
vii. Source of heat, delivery tube.
viii. Retort stand.
© Sam obare 13-May-21
, 3
5. Heat the boiling tube containing Observation and conclusion.
the food sample strongly. When food is burnt, carbon (IV)
6. Observe and record what happens oxide is produced which turns lime
to the food sample, calcium water milky.
hydroxide solution and the upper Water vapour is also produced that
sides of the boiling tube with the accumulate on the inner upper side
food sample. of the test tube which turns
7. Disconnect the apparatus and rub anhydrous cobalt (II) chloride paper
anhydrous blue cobalt (II) pink.
chloride paper on the inner upper
side of the test-tube containing
the food sample.
8. Record the colour change
observed on the blue cobalt (II)
chloride paper.
© Sam obare 13-May-21
, © Sam obare 4 13-May-21
