(a)Describe briefly the process involved in the conversion of food to chyme in the stomach of a mammal.
(b)Complete the table below by stating one enzyme, digestive juice, food acted upon and
end-product in the corresponding spaces.
| One Enzyme |
One juice |
One food acted upon |
One end-product |
|
Pepsin (i) ———– Lipase |
(ii)————— (iii)————— (iv)————— |
(v) ——————– (vi) ——————- (vii) ——————- |
(viii)——————- Maltose (ix)———————– |
(c) Describe an experiment to show that carbon dioxide is necessary for photosynthesis.
Explanation
(a) Process of conversion of food to chyme in the stomach of a mammal
The stomach is a large thick-walled muscular sac; made of three layers of muscles; that contracts in different directions when food enters into it; bringing about a twisting/squeezing/churning effect; enabling food to mix with digestive juice; and HCL; this movement then converts food to the semi-liquid called chyme.
(b) Table
Enzyme |
Juice |
Food acted upon |
end product |
|
Pepsin |
ii. Gastric |
v. Protein |
viii. Peptone/ polypeptide |
|
iii. Saliva/pancreatic juice |
vi. Cooked starch/carbohydrate |
Maltose |
|
Lipase |
iv. Intestinal/Pancreatic juice |
vii. Fats and Oil |
ix. Fatty acid and glycerol |
(c) Experiment to show that carbon dioxide is necessary for photosynthesis
Two potted plants are de-starched by placing them in a dark cupboard for 24hours;
a leaf each from both plants are then tested for starch to ensure they have no starch/have been de-starched; the potted plants are placed on a board each; a beaker containing caustic soda is placed beside plant A; to absorb carbon dioxide; while a beaker containing water is placed beside plant B as control; they are both covered with bell jars labelled A and B respectively; the rim/edge is smeared with vaseline/petroleum jelly to make it air tight; the setup is exposed to sunlight/light for 4-6 hours; a leaf each from both plants are plucked and tested for starch.
Observation: It is observed that leaf from plant A is negative/does not contain starch/remains brown in colour while leaf from plant B is positive/contains starch/turns blue - black.
Conclusion: Carbon dioxide is necessary for photosynthesis.
OR
De-starch a well-watered potted plant by putting it in darkness for 48 hours; insert a leaf into a flask containing water which serves as a control experiment; and another leaf into another flask containing KOH/ potassium hydroxide/ caustic potash; ensure both flasks are air tight by smearing the split corks with Vaseline; leave the potted plant in a well-lit place for 6 to 9 hours; detach the leaves and test them for starch.
Observation: It is observed that the leaf in the flask containing caustic potash contains no starch while the leaf in the controlled experiment contained starch.
Conclusion: Carbon dioxide is necessary for photosynthesis.