Pupil sheet · Chemical digestion

Three enzymes, three foods — questions

Name ______________________ Date ____________

Try every question before you use a nudge. Write in full sentences where you are asked to explain.

1. describe

Match each enzyme to the products it makes when it breaks its food down.

Write the number of the matching option.

Tiny droplets of fat
Fatty acids and glycerol
Amino acids
Starch
Simple reducing sugars

Amylase: ______
Protease: ______
Lipase: ______

Nudge (only if you are stuck): Use the table "One enzyme for each food". Which food does each enzyme act on, and what is that food built from?

2. calculate

Each fat molecule is built from one glycerol joined to three fatty acids. (a) In one tube, lipase completely digests 40 fat molecules. Calculate how many fatty acid molecules and how many glycerol molecules are made. (b) In another tube, lipase makes 270 fatty acid molecules. Calculate how many fat molecules it digested.

(a) Fatty acid molecules: ______________ unit ________

(a) Glycerol molecules: ______________ unit ________

(b) Fat molecules digested: ______________ unit ________

Nudge (only if you are stuck): Think of one fat molecule first: how many of each product does it give? Then scale up.

3. identify

The drawing shows the digestive system, with eight organs lettered A to H. Which letter shows the organ that secretes lipase?

Outline of a human body from the mouth to the hips, with the digestive system. The mouth, the duodenum, the rectum and the anus are named; eight other organs are lettered. A: two small glands beside the mouth. B: the tube from the mouth down to the stomach. C: the large organ at the top of the abdomen, on the left of the drawing. D: the small green bag under it. E: the muscular bag on the right of the drawing, below the end of the tube. F: the long, flat organ below this bag. G: the coiled tube in the middle of the abdomen. H: the wide tube that runs up, across and down around the coils.

Circle one answer.

Organ C
Organ F
Organ D
Organ E

Nudge (only if you are stuck): Lipase is secreted by only one gland, and that gland makes the other two enzymes as well.

4. identify

Match each organ to the digestive enzymes it secretes.

Write the number of the matching option.

Lipase only
None of these three
Protease only
Amylase only
Amylase, protease and lipase

Salivary glands: ______
Stomach: ______
Pancreas: ______
Liver: ______

Nudge (only if you are stuck): Use the table "Where each enzyme is made and where it works". One gland appears in all three rows.

5. classify

Each food is mostly one kind of large molecule. Match each food to the enzyme that digests its main molecule.

Write the number of the matching option.

Bile
Amylase
Protease
Lipase

Rice: ______
Chicken breast: ______
Sunflower oil: ______
Coconut oil: ______
Noodles: ______
White fish: ______

Nudge (only if you are stuck): First decide whether each food is mostly starch, protein or fat. Then choose the enzyme for that molecule.

6. identify

Which row is correct for one digestive enzyme?

Row	Enzyme	Secreted by	Acts in
A	lipase	liver	small intestine
B	protease	pancreas	pancreas
C	amylase	salivary glands	mouth
D	lipase	pancreas	stomach

Circle one answer.

Nudge (only if you are stuck): Check each row one column at a time: the enzyme, then the organ that secretes it, then the place where it acts.

7. identify

Look at the drawing of the digestive system. Which lettered organs secrete an enzyme that digests protein? Choose all that are right.

Tick every correct statement.

Organ D
Organ C
Organ H
Organ F
Organ E
Organ A

Nudge (only if you are stuck): Which enzyme digests protein? Then: which organs make it?

8. explain

A pupil writes: "The pancreas digests fat, because lipase is made there." Explain why this statement is incorrect.

Nudge (only if you are stuck): Is the place where lipase is made the same as the place where it works? Follow the pancreatic juice.

9. explain

Two tubes hold the same full-cream milk, which contains fat and protein but no starch, with universal indicator and a little alkali: both are blue, about pH 9. A pupil adds lipase to tube 1 and amylase to tube 2, and keeps both at 37 °C. After 30 minutes, tube 1 has turned yellow-green, about pH 6; tube 2 is still blue. Explain the results. (Fatty acids, as their name says, are acids.)

Nudge (only if you are stuck): Which molecule does each enzyme act on, and is that molecule in the milk?

10. explain

Some medicines make the salivary glands produce very little saliva. A person taking one of these medicines eats a bowl of porridge, made from oats, which is mostly starch. Explain whether the starch in the porridge will still be digested, and where.

Nudge (only if you are stuck): Look at where amylase is secreted. Does all of it come from the salivary glands?

11. explain

Biological washing powder contains protease and lipase. It removes stains of egg and of grease from clothes better than washing powder without enzymes. Explain how the two enzymes help to remove these stains.

Nudge (only if you are stuck): Which kind of large molecule is egg rich in, and which kind is grease? What are the products, and what happens to them in the water?

12. explain / suggest

A pupil chews a mouthful of plain boiled rice with a little margarine for two minutes without swallowing. The rice starts to taste sweet, but the margarine, a fat, does not change. (a) Explain why the rice starts to taste sweet. (b) Suggest why the fat in the margarine is not digested in the mouth.

(a) Why the rice starts to taste sweet

(b) Why the fat is not digested in the mouth

Nudge (only if you are stuck): Which enzyme is in saliva, and which kind of molecule does it act on?