10 Exchange of substances

Question 1

What is the importance of physical digestion?

Answer 1

it increases the surface area available for enzyme activity

Question 2

Why do large biological molecules need to be hydrolysed before they are absorbed?

Answer 2

they’re too large to be absorbed through lining of ileum

Question 3

What does hydrolysed mean?

Answer 3

molecule is split with addition of water

Question 4

What is the importance of chemical digestion?

Answer 4

large, insoluble molecules broken down into small, soluble ones by enzymes (hydrolases)

Question 5

What are the 3 main hydrolases?

Answer 5

carbohydrases, lipases, peptidases

Question 6

What is the general term given to enzymes that hydrolyse carbohydrates?

Answer 6

carbohydrases

Question 7

Is bile an enzyme?

Answer 7

no

Question 8

Does bile hydrolyse lipids?

Answer 8

no

Question 9

What are carbohydrates hydrolysed by and what is it turned into?

Answer 9

amylases
into maltose, glucose, and other monosaccharides

Question 10

What are lipids hydrolysed by and what is it turned into?

Answer 10

lipase
into fatty acids and monoglycerides

Question 11

What are proteins hydrolysed by and what is it turned into?

Answer 11

exopeptidases and endopeptidases
into amino acids

Question 12

Where is bile produced?

Answer 12

liver

Question 13

What 2 digestive chemicals is bile made of?

Answer 13

mineral and bile salts

Question 14

What is the role of bile salts in lipid digestion?

Answer 14

bile salts emulsify lipids into tiny droplets to increase surface area available to lipases

Question 15

Where are bile salts produced?

Answer 15

liver

Question 16

What can be used to model the activity of enzymes in the ileum?

Answer 16

visking tubing

Question 17

Visking tubing enables the effect of various factors, for example ____ and ___________, on enzyme activity to be tested.

Answer 17

Visking tubing enables the effect of various factors, for example pH and temperature, on enzyme activity to be tested.

Question 18

What is a micelle?

Answer 18

a tiny round complex formed from bile salts, fatty acids, and monoglycerides

Question 19

Why is Visking tubing a good model for the ileum?

Answer 19

it’s partially permeable, so it will allow small molecules to pass through it but not large ones

Question 20

________ are involved in the absorption of lipids.

Answer 20

Micelles are involved in the absorption of lipids.

Question 21

Give 3 factors on how the ileum is adapted to maximise absorption.

Answer 21

• very large surface area- lined with villi- villi covered in microvilli
• good blood supply (steep conc. gradient)
• thin walls (short diffusion pathway)

Question 22

In relation to the ileum, what does co-transport mean?

Answer 22

uptake of a biological molecule associated with uptake of an ion

Question 23

In the ileum, which substances are co-transported?

Answer 23

amino acids, glucose, sodium ions

Question 24

Is ATP required for co-transport? Explain your answer

Answer 24

no, because co-transport is a type of facilitated diffusion

Question 25

What is a monoglyceride?

Answer 25

a molecule of glycerol attached to one fatty acid

Question 26

What is a general term for enzymes that hydrolyse lipids?

Answer 26

lipases

Question 27

At which pH do enzymes in the ileum work best?

Answer 27

neutral pH (7)

Question 28

Why are several enzymes usually required to break down a biological molecule into monomers?

Answer 28

enzymes are substrate specific, so an enzyme that hydrolyses starch into maltose will not be able to hydrolyse maltose into glucose

Question 29

What is the difference between the action of exopeptidases and endopeptidases?

Answer 29

exopeptidases hydrolyse amino acids from ends of peptide; endopeptidases hydrolyse peptide bonds in central part of protein/ polypeptide