3B: Exchange of Substances

Question 1

What is Digestion?

Answer 1

The process in which large molecules are hydrolysed by enzymes into small molecules which can be absorbed and assimilated

Question 2

What is Physical Breakdown?

Answer 2

breaking up large pieces of food into small making the food ingestible (larger SA)

Question 3

What is Chemical Breakdown?

Answer 3

hydrolyses large insoluble molecules into smaller ones carries out by enzymes

Question 4

How many enzymes are needed to hydrolyse a large molecule?

Answer 4

> 1

Question 5

What are Carbohydrases?

Answer 5

Enzymes that hydrolyse carbohydrates into monosaccharides

Question 6

What are Lipases?

Answer 6

Enzymes that hydrolyse Lipids (fats and oils) into glycerol and fatty acids

Question 7

What are Proteases?

Answer 7

Enzymes that hydrolyse Proteins into Amino Acids

Question 8

Where is Amylase produced?

Answer 8

in the mouth and pancreas

Question 9

What does amylase do?

Answer 9

Hydrolyse alternate glyosidic bonds of starch to produce disaccharides of maltose

Question 10

What does Maltase do?

Answer 10

Hydrolyse maltose

Question 11

Where is maltase produced?

Answer 11

Ileum Lining, membrane-bound

Question 12

Why is saliva slightly alkaline?

Answer 12

to counteract any acid produced by bacteria and food to maintain a neutral pH for amylase

Question 13

What does Sucrase do?

Answer 13

Hydrolyse sucrose into glucose and fructose

Question 14

What does lactase do?

Answer 14

Hydrolyse lactose into glucose and galactose

Question 15

Where are lipases produced?

Answer 15

Pancreas

Question 16

What is a monoglyceride?

Answer 16

a glycerol molecule with a fatty acid attached

Question 17

What are micelles?

Answer 17

tiny droplets of lipids that are water soluble

Question 18

What emulsifies lipids and where is it produced?

Answer 18

Bile salts produced by the liver

Question 19

What is emulsification?

Answer 19

the process where bile salts break up lipids into micelles

Question 20

Why are bile salts needed to emulsify lipids?

Answer 20

to increase their surface area to speed up the hydrolysis reaction

Question 21

What are endopeptidases?

Answer 21

enzymes that hydrolyse peptide bonds between amino acids in the central region

Question 22

Where are endopeptidases produced?

Answer 22

the ileum

Question 23

What are exopeptidases?

Answer 23

enzymes that hydrolyse pepide bonds on terminal amino acids

Question 24

What are dipeptidases?

Answer 24

enzymes that hydrolyse peptide bonds in dipeptides

Question 25

How is the Ileum structure adapted for absoption?

Answer 25

thin walls lined with epithelial cells
a rich network of capillaries
villi and microvilli to increase surface area
constant muscle contraction to maintain concentration gradient

Question 26

How are amino acids and monosaccharides absorbed?

Answer 26

facilitated diffusion and co transport

Question 27

How are Lipids absorbed?

Answer 27

• emulsified into micelles by bile salts
• micelles release fatty acids, glycerol, and monoglycerides to diffuse into the epithelial cells lining the ileum
• the ER processes and packages the products into triglycerides
• the golgi apparatis packages these into chylomicrons
• chylomicrons enter blood stream via lacteals (exocytosis)

Question 28

Give examples of mechanical digestion

Answer 28

emulsification, chewing, oesophagus/small intestine contractions

Question 29

Give examples of chemical digestion

Answer 29

hydrolysis catalysed by enzymes

Question 30

What do micelles do?

Answer 30

Deliver fatty acids, glycerol and monoglycerides to the epithelial cells of the ileum by releasing them

Question 31

What is the Lymphatic System?

Answer 31

the system chich the lymph (excess tissue fluid) travels through after exiting th capillary, before rejoining the blood

Question 32

What is Transpiration?

Answer 32

the movement of water through the xylem vessels from evaporation of water from the leaves

Question 33

Describe the process of transpiration

Answer 33

1. water evaporates from mesophyll cells due to the heat from the sun
2. water molecules for hydrogen bonds causing cohesion
3. water forms continuous unbroken columns across mesophyll cells + down xylem
4. water evaporated from the mesophyll layers cause more water molecules to be drawn up

Question 34

Give evidence for cohestion theory

Answer 34

• trunk diameter changes due to rate of transpiration
• broken xylem vessels- air enters and flower droops
• broken xylem vessels- water doesn’t leak out (although root pressure)

Question 35

Describe the structure pf Xylem

Answer 35

dead, hollow lignin tubes with no wall ends

Question 36

What is the purpose of the Lymphatic System?

Answer 36

Drain excess tissue fluid that doesn’t get reabsorbed into the blood

Question 37

Describe the process of tissue fluid production in relation to capillaries, venules, and the lymphatic system

Answer 37

‘Tissue fluid’ leaks out of the gaps between the cells lining the capillaries due to the hydrostatic pressure from the heart
The water potential of the ‘blood’ decreases as water is the main component that leaks out
It fills the gaps around cells
The hydrostatic pressure in the venules is lower than the capillaries
Water moves via osmosis back into the venules down the water potential gradient, as well as other substances moving via diffusion
Excess tissue fluid is taken in by the lymphatic capillary, which is closed ended so it can only move forward.
Lymphatic capillaries have valvues to maintain unidirectional flow
The lymph moves through the lymphqtic system and reenters the blood flow near where the cardinal veins enter the heart