Nutrition and Digestion (CHO + PROTEIN)

Question 1

Monosaccharides definition

Answer 1

hexose sugars (6C) - breakdown products of complex CHOs which are absorbed by the small intestine

Question 2

Monosaccharide examples

Answer 2

glucose, galactose, fructose

Question 3

Disaccharides definition

Answer 3

two monosaccharides linked together by glycosidic bonds

Question 4

How are disaccharides broken down

Answer 4

broken down into constituent monomers by brush border enzymes of the small intestine

Question 5

Lactose is broken down into

Answer 5

glucose + galactose using lactase

Question 6

Sucrose is broken down into

Answer 6

glucose + fructose using sucrase

Question 7

Maltose is broken down into

Answer 7

glucose + glucose using maltase

Question 8

Disaccharide examples

Answer 8

lactose, sucrose, maltose

Question 9

Polysaccharides definiton

Answer 9

long chains of monosaccharide units linked together by glycosidic bonds

Question 10

Polysaccharide examples

Answer 10

starch, cellulose, glycogen

Question 11

Starch definition

Answer 11

1. plant storage form of glucose
2. two types: a-amylose and amylopectin
3. linked by a-1.4 glycosidic bonds

Question 12

a-amylose chains are

Answer 12

straight chains of glucose

Question 13

amylopectin chains are

Answer 13

highly branched chains of glucose

Question 14

a-1,4 glycosidic bonds (starch, glycogen) are hydrolysed by what enzyme

Answer 14

amylases (some from saliva, most from pancreas)

Question 15

cellulose definition

Answer 15

1. constituent of plant cell walls
2. unbranched linear chains of glucose monomers
3. linked by B-1,4 glycosidic bonds

Question 16

can the B-1,4 glycosidic bonds in cellulose be enzymatically digested

Answer 16

no, it is a dietary fibre - requires cellulase which is found in bacteria

Question 17

glycogen definition

Answer 17

1. animal storage form of glucose

2. glucose monomers linked by a-1,4 glycosidic bonds

Question 18

Polysaccharides are broken down by amylases into

Answer 18

disaccharides

Question 19

sucrose, maltose and lactose are all

Answer 19

oligosaccharidases

Question 20

Enterocyte definition

Answer 20

intestinal absorptive cells - simple columnar epithelial cells found in the small intestine

Question 21

How do glucose and galactose get into the cytoplasm of enterocytes

Answer 21

sodium-glucose co-transproters (SGLT-1) that are found on the apical surface of enterocytes

Question 22

How does fructose get into the cytoplasm of the enterocyte

Answer 22

uses GLUT5 to cross the apical membrane (facilitated diffusion)

Question 23

How do glucose and galactose exit the enterocyte to get into the blood stream

Answer 23

uses GLUT2 to exit via the basolateral membrane

facilitated diffusion

Question 24

How does fructose exit the enterocyte to get into the blood stream

Answer 24

uses GLUT2 to exit via the basolateral membrane

facilitated diffusion

Question 25

How does the sodium-glucose co-transporter (SGLT1) work

Answer 25

1. NaK pump on the basal membrane pumps 2K in and 3Na out
2. Does this via energy from hydrolysis of ATP
3. This ATPase maintains small -ve electric potential in cell
4. Electrogenic and osmotic Na+ gradient (from NaK pump and ATPase) in the cell used to transport monosaccharides out

Question 26

Protein definition

Answer 26

polymers of amino acids linked together by peptide bonds - can vary in length

Question 27

Peptides definition

Answer 27

small proteins, 3-10 amino acids in length

Question 28

addition of CHO to a protein creates

Answer 28

glycoprotein

Question 29

addition of a lipid to a protein creates

Answer 29

lipoprotein

Question 30

proteases

Answer 30

enzymes which hydrolyse peptide bonds and reduce proteins into amino acids

Question 31

peptidases

Answer 31

enzymes which hydrolyse peptide bonds and reduce peptides into amino acids

Question 32

How do amino acids enter into enterocytes

Answer 32

enter at the apical membrane along with Na+ using co-transpoters (SAAT1)

Question 33

How do amino acids exit the enterocyte and get into the blood stream

Answer 33

enter the circulation via selective channels in the basolateral membrane