Digestion and Absorption

Question 1

What is the function of carbodydrates and some sources of it?

Answer 1

• It is an energy source

- Bread, rice, pasta, cereals potatoes

Question 2

What is the function of protein and some sources of it?

Answer 2

• Used in repair and growth

- Meat, fish, dairy, lentils, seeds, nuts, tofu

Question 3

What is the function of fat and some sources of it?

Answer 3

• Long term energy store, insulation

- Meat, cheese, cream, nuts

Question 4

What is the function of vitamins and some sources of it?

Answer 4

-Function is vitamin specific; A=vision, C=antioxidant, D=Ca absorption
-A=liver, sweet potatoe
B= veg
C= citrus
D=oily fish

Question 5

What is the function of minerals and some sources of it?

Answer 5

-Mineral specific function; Fe=02 transport, Ca=bone mineralisation
-Ca=milk
Fe=red meat
K= bananas

Question 6

What is the function of fibre and some sources of it?

Answer 6

• Effective bowel function

- Plants (fruit, veg, nuts and cereals)

Question 7

What is the structure of fat?

Answer 7

• 90% are triglycerides
• Triglycerides = glycerol + 3 fatty acids
• May be saturated and unsaturated
• Cholesterol and phospholipids also in diet in smaller amounts.

Question 8

What is protein structure?

Answer 8

• Polymers of 20 amino acids

- 9 are essential in diet as cant be made in body

Question 9

What is carbohydrate structure?

Answer 9

-Can be: monosaccharides (glucose), disaccharides(sucrose) or polysaccharides

Question 10

Why do we need digestion and what is the basic breakdown of each of the 3 major food types?

Answer 10

• Foods not in molecular forms useful for body, digestion breaks down this into forms useful for the body
• Carb —>disaccharide—>monosaccharide
• Protein —>peptide—-> amino acids
• Triacylglycerol —> free fatty acid + diaclyglycerol + monoglycerol + glycerol

Question 11

What sorts of things aid digestion?

Answer 11

-Digestive secretions
Eg. carried out by enzymes secreted by:
-glandular cells in mouth
-chief cells in stomach
-exocrine cells of pancreas
-enzymes bound to the apical membrane of enterocytes

Question 12

What produces salivary secretions and what does it do?

Answer 12

• Produced by: parotid, submandibular and sublingual salivary glands
• Moistens food
• Starts digestion of carbohydrates with alpha amylase
• Starts digestion of lipids (lingual lipase)

Question 13

What are zymogens?

Answer 13

-Many enzymes are synthesised as inactive precursors that are subsequently activated by cleavage of one/ a few specific peptide bonds,
The inactive precursor is a zymogen.

Question 14

What is the function of the pancreas in digestion?

Answer 14

• Exocrine; pancreatic juices (enzyme) and alkali secretions. Also inactivate pepsin and provide optimal pH.
• Endocrine: secretion of insulin and glucagon.

Question 15

What are some examples of enzymes in pancreatic secretions?

Answer 15

Proteolytic = trypsin, elastase, phospholipase   (released as zymogens)
Non-proteolytic = alpha amylase, lipase, ribonuclease (released in active forms)

Question 16

What is the function of liver in digestion?

Answer 16

• Produces and secretes bile which is stored in gall bladder and released into duodenum after a meal.
• Causes emulsification of fat particles and aids absorption of fats by forming complexes called micelles.

Question 17

What are bile salts synthesised from?

Answer 17

Cholesterol

Question 18

What are the 3 sections of the small intestine and their functions?

Answer 18

-Duodenum; -mixing secretions from pancreas, liver and duodenum with food. 
Neutralisation of acid. 
Further digestion.
 Absorption.
-Jejenum; -completing breakdown.
Nutrient absorption.
-Ileum; -nutrient absorption

Question 19

What do enterokinases do?

Answer 19

In duodenum, is a protease that activates trypsin. Cleaves trypsinogen to make trypsin which activates other pancreatic zymogens.

Question 20

What are brush border enzymes?

Answer 20

Important in digestive system

-integral part of membrane eg. peptidases, lactase, sucrase, maltase

Question 21

What is chylomicron formation?

Answer 21

• If fatty acids are less than 12 carbons long they go straight to the portal blood.
• If larger they are reformed into a chylomicron. These are secreted into lymphatics via lacteals.

Question 22

What is the process of digestion in the mouth?

Answer 22

• Mastication begins and moistens food
• Bolus is formed
• Carbohydrates; starch broken down by alpha amylase to maltotriose, maltose and alpha limit dextrin.
• Proteins; nothing
• Lipids; lingual lipase present but minor contribution

Question 23

What is process of digestion in stomach?

Answer 23

• Bolus enters stomach and meets gastric juice and is churned and becomes chyme.
• Carbohydrates; nothing
• Proteins; HCl denatures protein and activates pepsin (endopeptidase that cleaves proteins to smaller peptides).
• Lipids; gastric lipase present but minor contribution

Question 24

What is process of digestion in duodenum?

Answer 24

• Chyme mixes with pancreatic juice and bile. Is slightly alkaline.
• Carbohydrate; alpha amylase further digests starch. brush border disaccharides (maltose, sucrose, lactose) result in monosaccharides
• Proteins; cleaved by trypsin, chymotrypsin, elastase, carboxypeptidases to produce increasingly smaller peptides/dipeptides.
• Lipids;pancreatic lipase digests lipids to monoglycerides and fatty acids. Phospholipase digests phospholipids to lysolecithin and fatty acids.

Question 25

What are the different types of absorption?

Answer 25

• Passive; -diffusion
• slow
• need conc. gradient or charge gradient
• Facilitated transport; -slightly faster
• involves membrane carrier
• controllable
• Active transport; -uses energy
• fast
• uses membrane carrier
• controllable