Question 1:
(a) Diagram 1.1 shows human digestive system.
Structure S in Diagram I is involved in the digestion of fat.
![](http://spmbiology.blog.onlinetuition.com.my/wp-content/uploads/sites/20/2019/10/Picture19-1.png)
(i) Name structure S.
(ii) Name the enzyme which digests fat in S.
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(iii) Diagram 1.2 shows a mechanism of an enzyme reaction.
Draw the diagram in the spaces III and IV provided in Diagram 1.2 to complete the mechanism of the enzyme reaction.
![](http://spmbiology.blog.onlinetuition.com.my/wp-content/uploads/sites/20/2019/10/Picture20.png)
(b)(i) Explain how starch is digested in the duodenum.
(ii) A student eats too many oranges.
Explain the effect of eating too many oranges on the digestion of starch in the duodenum.
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(c) In a food preparation process, a housewife carries out the following steps:
Step 1: Marinate pieces of meat with strips of unripe papaya in a basin.
Step 2: Immerse the basin in a container filled with water at 40
oC for 30 minutes as in Diagram 1.3.
![](http://spmbiology.blog.onlinetuition.com.my/wp-content/uploads/sites/20/2019/10/Picture21.png)
Explain why the housewife carries out Step 1 and Step 2.
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Answer:
(a)(i)
Structure S: Ileum
(a)(ii)
Enzyme which digests fat in S is Lipase
(a)(iii)
![](http://spmbiology.blog.onlinetuition.com.my/wp-content/uploads/sites/20/2019/10/Picture26-300x215.png)
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(b)(i)
The pancreas secretes an amylase into the duodenum which hydrolyses starch to maltose.
(b)(ii)
- The duodenum medium becomes acidic
- Which is not suitable for the action of the amylase on starch
- Slows down the digestion of starch
(c)
- Papaya contains papain/ protease
- The pieces of meat and papaya strips increase the total surface area
- To increase enzyme action
- Protease will tenderize the meat
- Takes place in water at 40
oC, which is the optimum temperature for enzyme reaction
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