Digestion and Absorption

Question 1

Key features of specialised exchange surfaces

Answer 1

Large SA:V ratio
Very thin- short diffusion pathway
Selectively permeable
Transport system to maintain concentration gradient

Question 2

Digestion

Answer 2

The process in which large insoluble molecules are hydrolysed into smaller soluble molecules that can be absorbed into the bloodstream

Question 3

Why do we use Mechanical Digestion?

Answer 3

To increase the surface area for chemical digestion

Question 4

Why do we use Chemical Digestion?

Answer 4

Using enzymes to hydrolyse large insoluble molecules

Question 5

Function of the mouth and salivary glands

Answer 5

Breaks food down physically

Secretes amylase to break down starch

Question 6

Function of oesophagus

Answer 6

Carries food to stomach

Question 7

Function of stomach and pancreas

Answer 7

Churns food

Secretes all pancreatic enzymes (amylase,protease,lipase)

Question 8

Function of liver and gall bladder

Answer 8

Secretes bile

Stores bile

Question 9

Function of small and large intestine

Answer 9

Absorbs small soluble molecules

Absorbs water from churned food

Question 10

Function of rectum and anus

Answer 10

Stores faeces

Ejects faeces

Question 11

Three sections of the small intestine

Answer 11

Duodenum
Jejunum
Ileum

Question 12

How does amylase hydrolyse starch?

Answer 12

Amylase hydrolysed alternate glycosidic bonds of the starch molecule, leaving many maltose molecules

Thus is then hydrolysed into alpha glucose by maltase

Question 13

Process of starch through the digestive system

Answer 13

Food is chewed into smaller pieces
Salivary glands produce amylase to hydrolyse starch into maltase
Amylase gets denatured in the stomach
The pancreas produces amylase to hydrolyse remaining starch
Membrane-bound maltase on epithelial cells of the ileum hydrolyse maltose into alpha glucose

Question 14

Process of Glucose Absorption

Answer 14

Sodium Potassium Pump actively pumps 3 Na ions into the blood from the epithelial cell and 2 K ions I into the epithelial cell from the blood, using ATP
This decreases the conc of Na in the epithelial cell
Na and glucose are carrried into the epithelial cell via a symport protein
The conc of glucose in the epithelial cell increases
Glucose is carried into the bloodstream via facilitated diffusion

Question 15

How is the epithelial cell adapted for glucose absorption?

Answer 15

Villi and microvilli- large SA
membrane bound enzymes- quickly hydrolyses maltose
Many mitochondria- produces ATP for AT
Many Na-K pumps- for AT
Channel proteins- facilitated diffusion of glucose
Symport proteins- enables co-transport of glucose and Na

Question 16

Role of Endopeptidase

Answer 16

Hydrolyses bonds between amino acids in the central region of a protein (internal bonds) to form smaller peptide molecules

Question 17

Role of Exopeptidase

Answer 17

Hydrolyses bonds on the terminal amino acids of peptides formed by endopeptidase molecules

Question 18

Why do Endopeptidase and Exopeptidase work efficiently together?

Answer 18

Endopeptidase hydrolyses internal bonds to form many polypeptides
This means there is an increased surface area for Exopeptidase

Question 19

Role of Dipeptidase

Answer 19

Found in membrane of epithelial cells in small intestine

They hydrolyse do peptides into 2 amino acids which can be absorbed quickly