Enzymes And Digestion

Question 1

What does the oesophagus do

Answer 1

Carries food from the mouth to stomach

Question 2

What’s the role of the stomach

Answer 2

Store and digest food, especially proteins. It has glands that produce enzymes which digest proteins

Question 3

What’s the purpose of the ileum and how is it adapted to it

Answer 3

Absorbing the products of digestion into the blood stream

Food is further digested by enzymes produced by its walls and glands that pour their secretion into it
The inner walls of the ileum are folded into villi- giving them a large SA. SA can be further increased by the mircrovilli on the epithelial cells of each villus

Question 4

What does the large intestine do

Answer 4

Absorb water- many of it is from the secretions of the many digestive glands

Question 5

What is the role of the rectum

Answer 5

Faeces are stored here before being removed by the Anya in egestion

Question 6

What do the salivary glands do

Answer 6

They pass their secretions via a duct in the mouth.

The secretions contain the enzyme amylase, which hydrolyses starch into maltose

Question 7

What is the role of the pancreas

Answer 7

Produced a secretion called pancreatic juice. It contains proteases to hydrolyse proteins, looses to hydrolyse lipids and amylase to hydrolyse starch

Question 8

What are the two stages of digestion

Answer 8

Physical breakdown

Chemical digestion

Question 9

What happens during physical breakdown stage

Answer 9

Broken down into smaller pieces by teeth - Providing a large SA for chemical digestion and make it possible to ingest food

Food is churned by muscles in stomach wall this physically breaks it up

Question 10

What happens during chemical digestion

Answer 10

It hydrolyses large, insoluble molecules into smaller, soluble ones.

Usually one enzyme hydrolyses a large molecule into sections and these sections are then hydrolysed into smaller molecules by one or more additional enzymes

Question 11

What do all digestive enzymes function by

Answer 11

Hydrolysis

Question 12

What are the three types of digestive enzymes

Answer 12

Carbohydrases- hydrolyse carbohydrates ultimately to monosaccharides

Lipases - hydrolyse lipids into glycerol and fatty acids

Proteases - hydrolyse proteins, ultimately to amino acids

Question 13

How is Maltase produced by the lining of the ileum

Answer 13

Saliva contains amylase - starts hydrolysing any food to maltose (contains mineral salts to maintain the pH around neutral- where they work best)

Food is swallowed and enters stomach - acid denatures the amylase and prevents further hydrolysis of starch

Food is passed into small intestine, where it mixes with pancreatic juice- contains amylase - continuing the hydrolysis of remaining starch to maltose (alkaline salts produced by Pancreas and intestinal wall to maintain pH around neutral for amylase to function)

Muscles in intestine wall push food along ileum. Epithelial lining produces maltase(membrane bound disaccharide). Maltase hydrolyses the maltose from starch breakdown into a-glucose

Question 14

What does sucrase hydrolyse

Answer 14

Single glycosidic bond in sucrose. Hydrolysis produces the two monosaccharides glucose and fructose

Question 15

What does lactase hydrolyse

Answer 15

Single glycosidic bond in the lactose molecule. This hydrolysis produces glucose and galactose

Question 16

Where are lipases produced and which bond do they hydrolyse

Answer 16

In the pancreas

they hydrolyse the ester bond

Question 17

What are lipids split up into micelles by

Answer 17

Bile salts ( produced by liver)

Question 18

In lipid digestion, what does emulsification do

Answer 18

Increase SA of the lipid so that the action of lipases is speeded up

Question 19

What are the three types of peptidases

Answer 19

Endopeptidases

Exopeptidases

Dipeptidases

Question 20

What does an endopeptidase do

Answer 20

Hydrolyse peptide bonds between amino acids in central region of a protein molecules forming a series of peptide molecules

Question 21

What does an exopeptidase do

Answer 21

Hydrolyse the peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases. In this way they progressively release dipeptides and single amino acids

Question 22

What do dipeptidases do

Answer 22

Hydrolyse bond between two amino acids of a dipeptide.

They are membrane bound, being part of the cell surface membrane of the epithelial cells lining the ileum

Question 23

How do the villis properties increase the efficiency of absorption

Answer 23

Increase SA for diffusion

Very thin walled, reducing diffusion distance

Contain muscle, able to move - helps maintain diffusion gradient as their movement mixes the contents of the ileum

Supplied well with blood vessels - so that blood can carry away absorbed molecules and maintain a diffusion gradient

Epithelial cells lining the villi posses microvilli- further increase SA for absorption

Question 24

What happens to the fatty acids and monoglycerides during absorption once inside the epithelial cells

Answer 24

Transported to endoplasmic reticulum- recombined to form triglycerides

Starting in endoplasmic reticulum and continuing in Golgi apparatus

Triglycerides associate with cholesterol and lipoproteins to form structures called chylomicrons(special particles adapted for transport of lipids)

Chylomicrons move out of epithelial cells by exocytosis

Enter lymphatic capillaries called lacteal and then the blood stream