Nutrient Digestion 1

Question 1

What are the principle dietary constituents?

Answer 1

Carbohydrates

Protein

Fat

Vitamins

Minerals

Water

Question 2

What are different classes of carbohydrates?

Answer 2

Monosaccharides

Disaccharides

Polysaccharides

Question 3

What are monosaccharides?

Answer 3

Hexose sugars (6C)

Question 4

What are examples of monosaccharides?

Answer 4

Glucose

Galactose

Fructose

Question 5

Where are monosaccharides absorbed?

Answer 5

Small intestine

Question 6

What bond connects disaccharides?

Answer 6

Glycosidic bond

Question 7

What and where are disaccharides broken down into monosaccharides?

Answer 7

By brush border enzymes in the small intestine

Question 8

Why are all complex carbohydrates broken down into monosaccharides?

Answer 8

Only monosaccharides can be absorbed

Question 9

What is lactose formed from?

Answer 9

Glucose and galactose

Question 10

What enzyme breaks lactose down into glucose and galactose?

Answer 10

Lactase

Question 11

What is sucrose formed from?

Answer 11

Glucose and fructose

Question 12

What breaks sucrose down into glucose and fructose?

Answer 12

Sucrase

Question 13

What is maltose formed from?

Answer 13

Glucose and glucose

Question 14

What breaks maltose down into 2 glucose monomers?

Answer 14

Maltase

Question 15

What are some examples of polysaccharides?

Answer 15

Starch

Cellulose

Glycogen

Question 16

What is starch?

Answer 16

Plant storage form of glucose

Question 17

What are some examples of starch?

Answer 17

a-amylose (glucose linked in straight chains)

Amylopectin (glucose chains highly branched)

Question 18

What are glucose monomers linked by in starch?

Answer 18

a-1, 4 glycosidic bonds

Question 19

What are a-1, 4 glycosidic bonds broken down by?

Answer 19

Amylases

Question 20

What is cellulose?

Answer 20

Constituent of the plant cell wall

Unbranched linear chains of glucose monomers linked by B-1, 4 glycosidic bonds

cannot be broken down naturally and needs bacteria to be broken down (bacteria in large intestine)

Question 21

What are B-1, 4 glycosidic bonds broken down by?

Answer 21

Cellulase

Question 22

What is cellulose also known as?

Answer 22

Dietary fibre

Question 23

Why is cellulose only broken down by bacteria and not enzyme?

Answer 23

Animals do not synthesis cellulase which is required to break down B-1, 4 glycosidic bonds

Question 24

What is glycogen?

Answer 24

Animal storage form of glucose

Question 25

How are glucose monomers linked in glycogen?

Answer 25

a-1, 4 glycosidic bonds

Question 26

Where are maltase, sucrase and lactase found?

Answer 26

Brush border of the small intestine

Question 27

What increases the surface area of epithelial cells?

Answer 27

Villi for absorption

Question 28

What are the 2 membranes of epithelial cells?

Answer 28

Apical membrane facing the lumen of the gut Basal and lateral membranes facing the blood circulation

Question 29

What is transepithelial transport?

Answer 29

Travelling through both the apical and basal membranes of epithelial cells

Question 30

What is transport from the lumen to the blood circulation around the cells called?

Answer 30

Paracellular transport

Question 31

What is transport from the lumen to the blood circulation through the cells called?

Answer 31

Transcellular

Question 32

Which 2 of the 3 monosaccharides are absorbed by the same mechanism?

Answer 32

Glucose and galactose

Question 33

What is the process of glucose/galactose absorption?

Answer 33

1) Na/K ATPase found on basolateral membrane which hydrolyses ATP to pump Na out of the cell and Na into the cell created Na concentration gradient allowing SGLT1 to work 2) 1 Na and 1 glucose travel from gut lumen into cell through SGLT1 transporter protein 3) Glucose concentration develops inside cell to leaves down gradient into the circulation through GLUT-2 transport protein 4) Concentration gradient of Na causes water to travel from lumen of gut to blood through leaky membrane between cells

Question 34

What transport protein does 1 Na and 1 glucose use to travel from gut lumen into cell?

Answer 34

SGLT1 transporter protein

Question 35

Why does SGLT1 transporter protein need both Na and glucose to bind to transport molecules into the cell?

Answer 35

Both binding causes conformational change that flips the protein, having an extremely high affinity when facing gut lumen and extremely low affinity when facing inside the cell to release the molecules

Question 36

What allows SGLT1 to work?

Answer 36

The concentration gradient of Na created by Na/K ATPase pumping Na out of the cell and K into the cell

Question 37

What protein does glucose use to leave the cell to the blood cirulation?

Answer 37

GLUT-2 transport protein

Question 38

Why does water travel from the gut lumen into the blood circulation during glucose/galactose absorption?

Answer 38

Concentration gradient of Na affects the osmolarity

Question 39

What is the process of fructose absorption?

Answer 39

1) Fructose travels into the cell from the lumen through the GLUT-5 transport protein 2) Enters the circulation from the cell through the GLUT-2 transport protein

Question 40

What transport protein does fructose use to enter the cell from the gut lumen?

Answer 40

GLUT-5 transport protein

Question 41

What transport protein does fructose use to enter the blood circulation from the cell?

Answer 41

GLUT-2 transport protein

Question 42

Does water travel from the gut lumen to the blood circulation during fructose absorption?

Answer 42

No because fructose transporters do not rely on Na gradient created by Na/K ATPase so osmolarity remains unchanged

Question 43

What are proteins?

Answer 43

Polymers of amino acids linked together by peptide bonds (between amino and carboxy ends)

Question 44

What bonds connects the polymers of amino acids to form proteins?

Answer 44

Peptide bond

Question 45

What do proteins often undergo after being synthesised?

Answer 45

Post-translational modifications

Question 46

What are examples of post translational modifications?

Answer 46

Addition of CHO making glycoproteins Addition of lipid making lipoproteins

Question 47

What are small proteins (3-10 amino acids in length) known as?

Answer 47

Peptides

Question 48

What enzymes hydrolyse peptide bonds to reduce proteins to amino acids?

Answer 48

Proteases or peptidases (known as peptidases when break down peptides which are small proteins)

Question 49

What are examples of proteases?

Answer 49

Trypsin and chymotrypsin

Question 50

What are the different categories of peptidases?

Answer 50

Endopeptidases Exopeptidases (aminopeptidase and carboxypeptidase)

Question 51

What do endopeptidases do?

Answer 51

Break bond in the middle of a protein

Question 52

What do exopeptidases do?

Answer 52

Break bond at the end of a protein

Question 53

What do aminopeptidases do?

Answer 53

Break bond at the amino terminal of a protein

Question 54

What do carboxypeptidases do?

Answer 54

Breaks bond at the carboxy terminal of a protein

Question 55

How many naturally occuring amino acids are they?

Answer 55

20

Question 56

What can be said about the transporting mechanisms of amino acids?

Answer 56

They all have their unique transporting mechanisms

Question 57

What is the process of a typical absorption mechanism of a protein?

Answer 57

1) Na/K ATPase pumps Na from cell to circulation and takes in K 2) Due to Na concentration gradient Na and amino acid are transported into th cell by SAAT1 transporter protein 3) Amino acid enters the circulation through a transporter protein down its concentration gradient 4) Water travels from gut lumen into circulation due to Na concentration gradient created by Na/K ATPase

Question 58

What transporter protein takes in Na and amino acid from the gut lumen into the cell?

Answer 58

SAAT1

Question 59

Does water travel from the gut lumen to the circulation during protein absorption?

Answer 59

Yes due to Na concentration gradient created by Na/K ATPase

Question 60

What can be absorbed instead of individual amino acids?

Answer 60

Di and tri-peptides

Question 61

What is the process of di/tri peptides being absorbed?

Answer 61

1) Di/tripeptide enters the cell from lumen with H ion through PepT1 transporter protein 2) H ion leaves cell back into lumen through NHE3 so Na can enter the cell 3) This H ion entering the lumen acidifies it and creases an acidic layer 4) Na leaves the cell into circulation due to ATPase, whilst K enters the cell from the circulation 5) Di/tripeptide leaves the cell into the circulation through transporter protein 6) Water travels from lumen into circulation due to Na concentration gradient created by Na/K ATPase

Question 62

What transporter protein does di/tripeptide and H use to enter the cell from the gut lumen?

Answer 62

PepT1

Question 63

What transporter protein does H use to leave the cell and return to the gut lumen with Na coming in from the lumen?

Answer 63

NHE3 transporter protein