Nutrient Digestion - Carbohydrates, Proteins, Fats, Vitamins and Minerals

Question 1

What are the only three sugars that can be taken up across the gut epithelia?

Answer 1

Monosaccharides - glucose, galactose and fructose

Question 2

What bonds are broken between disaccharide monomers to form simpler molecules?

Answer 2

Glycosidic

Question 3

Disaccharides are broken down to their constituent monomers through the use of what?

Answer 3

Brush border enzymes

Question 4

What are the three dietary disaccharides and their constituent monomers?

Answer 4

Lactose - glucose and galactose
Sucrose - glucose and fructose
Maltose - glucose monomers

Question 5

What are the enzymes responsible for breaking down disaccharides into their constituent monomers?

Answer 5

Lactase breaks down lactose
Sucrase breaks down sucrose
Maltase breaks down maltose

Question 6

The alpha-1,4-glycosidic bonds between the glucose monomers of starch are broken down by what?

Answer 6

The bonds are hydrolysed by amylases in saliva and in the pancreas

Question 7

Why can’t animals break down cellulose?

Answer 7

The beta-1,4-glycosidic bonds between the glucose monomers of cellulose can only be broken down by cellulase, which is an enzyme that no animals have the capability to express

Question 8

What breaks down glycogen?

Answer 8

Alpha-amylase

Question 9

What are the three mechanisms through which monosaccharides are absorbed across intestinal epithelial cells?

Answer 9

Transcellular
Paracellular
Vectorial Transport

Question 10

What is the route that most nutrients will take when absorbed across intestinal epithelial cells?

Answer 10

Transcellular - lipid soluble molecules which can cross apical and basolateral membranes

Question 11

What route of absorption across intestinal epithelial cells involves molecules of the right shape and size crossing through the tight junctions between epithelial cells?

Answer 11

Paracellular

Question 12

What transport mechanism is used for water soluble molecules which cannot transport across the lipid membrane?

Answer 12

Vectorial transport

Question 13

What transport mechanism involves the use of transporter proteins?

Answer 13

Vectorial transport

Question 14

What are peptides?

Answer 14

Polymers of amino acids, 3-10 amino acids in length

Question 15

Polymers of amino acids in chains with a length of 10 or more amino acids are what?

Answer 15

Proteins

Question 16

What bonds need to be hydrolysed between proteins in order to convert them to peptides and amino acids for digestion?

Answer 16

Peptide

Question 17

What enzymes hydrolyse peptide bonds?

Answer 17

Proteases and peptidases

Question 18

Where do endopeptidases act?

Answer 18

Somewhere in the middle of the protein

Question 19

Where do exopeptidases act?

Answer 19

Only on the terminal amino acids of a protein, removing amino acids one at a time

Question 20

How are amino acids and small peptides absorbed across gut epithelia?

Answer 20

Transported in/out by a pump

Question 21

What does the SAAT1 pump do?

Answer 21

Binds to a sodium molecule and an amino acid at the apical membrane and pumps both into the cell

Question 22

The movement of sodium through the cell and the ion gradient it creates causes what?

Answer 22

The movement of water in the same direction as sodium, through the tight junctions

Question 23

What is PepT1?

Answer 23

A protein coupled transporter which transports dipeptides and tripeptides as well as a hydrogen ion into the cell

Question 24

What can penicillin transport into the gut epithelial cells?

Answer 24

Tripeptides

Question 25

Almost all fat is ingested in the form of

Answer 25

triacylgylcerol

Question 26

What is triacylglycerol broken into during digestion?

Answer 26

Monoglyceride and fatty acids

Question 27

All fat digestion takes place _ through the use of _

Answer 27

in the small intestine | through the use of pancreatic lipase

Question 28

What will happen when pancreatic lipase is digesting triaclyglycerols which are present as large lipid droplets?

Answer 28

Pancreatic lipase is water soluble but not lipid soluble so can only work on the outer surface of the lipid droplet, it will therefore be unable to digest all the fat

Question 29

What is the name for fat in stools?

Answer 29

Steatorrhoea

Question 30

What does emulsification of ingested fats do?

Answer 30

Divides large lipid droplets (triaclyglycerols) into smaller droplets, increasing surface area available to pancreatic lipase and making fat digestion more manageable

Question 31

What three things does emulsification require?

Answer 31

Mechanical disruption Smooth muscle contraction An emulsifying agent

Question 32

What is the purpose of an emulsifying agent?

Answer 32

To stop the reformation of smaller lipid droplets into large lipid droplets

Question 33

What is the purpose of bile salts and phospholipids in fat digestion?

Answer 33

Both prevent the re-formation of small droplets of fat produced by emulsification into larger droplets

Question 34

Bile salts and phospholipids are secreted in

Answer 34

bile

Question 35

What feature of bile salts and phospholipids makes them effective at preventing the reformation of large lipid droplets?

Answer 35

They are amphipathic - non-polar portions associate with non-polar interior of the droplet leaving the polar portions exposed at the surface which repel other small lipid droplets

Question 36

What are the components of micelles?

Answer 36

Bile salt Monoglyceride Fatty acids Phospholipids

Question 37

What is the purpose of micelles in fat digestion?

Answer 37

Enhance fat absorption by taking fat molecule to the microvilli of the epithelia for absorption

Question 38

What happens once fatty acids and monoglycerides enter the smooth ER after entering epithelial cells?

Answer 38

They are reformed into triacylglycerol droplets which are emulsified

Question 39

What are the fat soluble vitamins?

Answer 39

A, D, E and K

Question 40

What are the water soluble vitamins and how are they absorbed?

Answer 40

B group, C and folic acid | Absorbed by passive diffusion or carrier-mediated transport

Question 41

How is vitamin B12 absorbed?

Answer 41

It binds to an intrinsic factor in the stomach to form a complex which is absorbed via a specific transport mechanism in the distal ileum

Question 42

What does a vitamin B12 deficiency cause?

Answer 42

Pernicious anaemia

Question 43

What percentage of daily ingested iron is absorbed across the intestine into the blood?

Answer 43

10%

Question 44

Iron ions are incorporated into what, in order to be stored intracellularly?

Answer 44

Ferritin

Question 45

For how long does iron stay bound in ferritin?

Answer 45

Until the cell containing the ferritin dies, at which point the iron is expelled from the body

Question 46

What happens to unbound iron?

Answer 46

It is transported across the serous membrane where it binds to transferrin and is taken to the liver for storage

Question 47

What 3 pairs of glands secrete saliva?

Answer 47

Parotid Submandibular Sublingual

Question 48

What are the components of saliva?

Answer 48

``` Water Mucins Alpha-amylase Electrolytes Lysozyme ```

Question 49

What are the functions of water in saliva?

Answer 49

Softens, moistens and dilutes particles

Question 50

What is the function of mucins in saliva?

Answer 50

To combine with water to form mucous which acts as a lubricant

Question 51

What is the function of alpha-amylase in the saliva?

Answer 51

Catalyses the breakdown of polysaccharides into disaccharides + glucose

Question 52

What is the function of electrolytes in the saliva?

Answer 52

Control the tonicity and pH

Question 53

What is the function of lysozyme in the saliva?

Answer 53

Bacteriocidal - cleaves the polysaccharide component of any bacterial cell wall ingested