Digestion And Absorption

Question 1

Describe the function of the oesophagus

Answer 1

It carries food from the mouth to the stomach

Question 2

Describe the function of the stomach

Answer 2

• it is a muscular sac, primarily storing and digesting food
  -it contains an inner layer that produces digestive enzymes

Question 3

Describe the function of the ileum

Answer 3

• it is a long muscular tube which further digests food
• its inner membranes are folded into villi which further form many projections of microvilli increasing SA and absorbing the further products of digestion

Question 4

Describe the function of the large intestine

Answer 4

• it absorbs water

Question 5

Describe the function of the rectum

Answer 5

-the final section of the intestines which stores feces until egestion

Question 6

Describe the function of the salivary glands

Answer 6

• they are situated near the mouth and secrete amylase which hydrolyses starch into maltose

Question 7

Describe the function of the pancreas

Answer 7

• a sac below the stomach which releases pancreatic juices containing amylase, lipase and protease

Question 8

What are the two steps in digestion?

Answer 8

• physical breakdown
• chemical breakdown

Question 9

How is food physically digested?

Answer 9

-if food is too large, it is broken down into smaller pieces by the teeth
- this increases the surface area for digestion, making it more digestible

Question 10

How is food chemically digested?

Answer 10

• food can be broken down by digestive enzymes into smaller, soluble molecules

Question 11

Describe the steps of how carbohydrates are digested?

Answer 11

• saliva enters the mouth from salivary glands and mixes with food. Saliva contains amylase which hydrolyses starch into maltose. It also contains digestive enzymes which maintain an optimum PH
• food then enters the stomach which denatures amylase to prevent the further hydrolysis of starch
• when food enters the pancreas, pancreatic amylase hydrolyses any remaining starch
• the muscles in the intestine push food into the illeum which produces maltase, this hydrolyses maltose from the breakdown of glucose

Question 12

How are proteins digested?

Answer 12

• proteins are hydrolysed by peptidases:
  Endo-peptides: hydrolyses peptide bonds in the centre of proteins forming a series of peptides
  Exopeptides: Hydrolyses peptide bonds on terminal amino acids on peptides produced by endo - peptides releasing dipeptides and singular amino acids
  Dipeptides: Hydrolyses the peptide bonds between dipeptides

Question 13

How are lipids digested?

Answer 13

• lipids are hydroylsed by lipases
• lipase digests lipids into fatty acids and monoglycerides by hydrolysing ester bonds

Question 14

What are monoglycerides?

Answer 14

• a single fatty acid attached to a glycerol molecule

Question 15

What is the structure of the illeum?

Answer 15

• contains villi which are foldings of the inner membrane to increase SA
• increases surface area
• decreases diffusion distance
• supply’s blood vessel
• maintains diffusion gradients
• contains epithelial cells as linings of the illeum

Question 16

How are triglycerides absorbed?

Answer 16

• after forming in digestion, monolglycerides and fatty acids remain in association with bile salts
• this forms micelles
• when moving, micelles become in contact with epithelial cells within the lining of epithelial cells within the lining of the illeum
• this causes them to breakdown into monoglycerides and fatty acids
• these then diffuse into epithelial cells
• these are then transported to the RER where they are combinded to reform triglycerides
• in the Golgi apparatus, triglycerides associate with proteins and cholesterol, forming chylomicrons
• these chylomicrons move out of the epithelial cells by exocytosis and enter lacteals
• lacteals are lymphatic blood vessels which then allow triglycerides to be absorbed to the blood