Digestion And Absorption

Question 1

What happens in digestion?

Answer 1

Large biological molecules a hydrolyse to smaller molecules that can be absorbed across cell membranes

Question 2

Give examples of large biological molecules in food

Answer 2

Starch/proteins (too large to be absorbed across the cell membrane

Question 3

What does digestion break Large molecules such as starch on proteins down into and what does this mean?

Answer 3

Protein is broken into amino acid’s

Starch broken into glucose

Can be absorbed from the gut into the blood

Question 4

What is amylase produced by?

Answer 4

Saliva re gland is (released into mouth)

Pancreas (released into small intestine)

Question 5

Explain how starch (polysaccharide) is digested

Answer 5

1. Amylase hydrolyses starch to maltose (polysaccharide to disaccharide)
2. Membrane bound maltase (attached to epithelial cells lining ileum of small intestine) hydrolysed maltose to glucose (disaccharide to monosaccharide)
3. Hydrolysis of glycosidic bonds

Question 6

Where are membrane bound disaccharidases attached ?

Answer 6

Attached to epithelial cells lining the ileum of the small intestine

Question 7

Give three examples of membrane-bound disaccharidases?

Answer 7

Maltase
Lactase
Sucrase

Question 8

Explain how disaccharides are digested

Answer 8

Membrane-bound disaccharidases hydrolyse the disaccharide into two monosaccharides

MaltASE: maltose —> glucose + glucose
SucrASE: sucrose —> glucose + fructose
LactASE: lactose —> glucose + galactose

Hydrolysis of glycosidic bond

Question 9

Talk about bile salts

Answer 9

Bile salt produced by the liver

Bile salts emulsify lipid to the smaller lipid droplets

Increasing surface area of lipids means lipases can work at faster rate

Question 10

Where is lipase made?

Answer 10

Pancreas

Released into small intestine

Question 11

Explain how lipase hydrolyses lipids

Answer 11

Lipase hydrolyses lipids —> three fatty acids + glycerol

Breaking ester bonds

Monoglycerides, fatty acids and bile salts stick together to form micelles

Question 12

Endopeptidases

Answer 12

Hydrolyse peptide bonds within a protein/between amino acids in the central region

Breaking protein into two or more smaller peptides

Question 13

Exopeptidases

Answer 13

Hydrolyse peptide bonds at the end of protein molecules

Removing a single amino acid

Question 14

Dipeptidases are a type of…

Answer 14

Exopeptidase

Question 15

Dipeptidases

Answer 15

Often membrane-bound in ileum of small in testing

Hydrolyse peptide bond between a dipeptide to produce two amino acids

Question 16

Mechanisms for the absorption of the products of digestion by cells lining the ileum of mammals to include the role of micelles in the absorption of lipids

??????

Answer 16

Monoglycerides and fatty acids diffuse out of micelles in the lumen into epithelial cells

Because they are lipid soluble

——

Monoliths rides and triglycerides recombine to triglycerides which aggregate into globules

——
Globules coated with proteins to form chylomicrons

——
Leave via exocytosis and enter lymphatic vessels

——
Return to blood circulation

Question 17

The concentration of glucose in the blood rises after eating a mill contain carbohydrates.

The rise of slow if the carbohydrate is start rather than screws. Explain why.

Answer 17

Digestion of sucrose occurs in one single step

Starch is digested to maltose and then digested to glucose

Question 18

Group a actors as a control for the mouse yoghurt investigation. Explain the purpose of the control group. (2)

Answer 18

To show the effect of the inhibitor

To show the effects of yoghurt

Question 19

Give two reasons why it is important that all the marks were given the same food each day

Answer 19

Different foods contain different amounts of glucose

To keep starch/fibre intake the same

Question 20

Use your knowledge to suggest how the addition of the inhibitor of amylase could lead to lower blood glucose concentration (2)

Answer 20

FEWER ES COMPLEXES FORM

So less starch is digested to maltose

So less glucose from maltose

So less absorption of glucose from the gut

Question 21

Reasons why results may not support use of the inhibitor of amylase to treat diabetes and mice (5)

Answer 21

No SDs
So don’t know if results are significant

Larger sample needed
Might not be representative (anomalies may have a bigger or smaller affect)

Investigation only lasted 20 days
Don’t know long term effects

Fall in blood glucose small
Mice with inhibitor still have a large rise of blood glucose levels

Blood glucose could continue to fall to really low levels
Which could be harmful

Question 22

Where is Maltase produced?

Answer 22

On epithelium of small intestine

Question 23

Describe the proteins are digested in the human gut (4)

Answer 23

Hydrolysis of peptide bonds

Endopeptidases break polypeptides into smaller peptide chains

Exopeptidase is remove terminal amino acids

Dipeptideases hydrolyse dipeptides into amino acids