6 Human
Nutrition
WS 1
1
(a) Structure P: X 1m
Structure
R: Z 1m
It is
because saliva present in structure P (mouth cavity) contains salivary amylase,
which
catalyses the breakdown of starch into maltose.
/ Saliva does not contain enzymes for the breakdown of proteins and lipids. 1m
Gastric
juice present in structure R (stomach) contains pepsin,
which
catalyses the breakdown of proteins into peptides.
/ Gastric juice does not contain enzymes for the breakdown of carbohydrates
and lipids. 1m
(b) The oil will be emulsified into small
droplets. 1m
(c) Due to the blockage of the pancreatic duct,
pancreatic lipase cannot reach the duodenum. 1m
Lipids
cannot be completely digested. Some of them cannot be absorbed and thus
appear in the faeces. 1m
(d) Structure T is very long. 1m
This
allows sufficient time for complete absorption. 1m
2
(a) The
concentration of glucose in the blood in Y is higher than that in X. 1m
Glucose from the breakdown of starch in the rice is
absorbed into the capillaries in the villi
of the small intestine and transported to the liver
via the hepatic portal vein (Y). 1m
Thus, the concentration of glucose in the blood in Y
increases. 1m
The excess glucose in the blood is converted to
glycogen in the liver. 1m
Therefore, the concentration of glucose in the blood
in the hepatic vein (X) does not change
after the person ate the rice. 1m
(b) Liver produces bile, which is a digestive juice. 1m
沒有留言:
張貼留言