Glucose Metabolism

Question 1

Starch

Answer 1

amylose (a’1-4) and amylopectin (a’1-4, a’1-6 = branched)

Question 2

Amylases

Answer 2

~ break (a’1-4) bond
alpha-amylase = pancreatic juice
salivary amylase = mouth

Question 3

Amylose + a’-amylase

Answer 3

maltotriose + maltose

Question 4

Amylopectin + a’-amylase

Answer 4

maltotriose + alpha-limit dextrins

Question 5

Bolus

Answer 5

food that has been chewed and mixed in the mouth with saliva

Question 6

(a’1-6) glucosidase

Answer 6

~ enzyme produced in intestinal vili

~ breaks down a’-limit dextrins

Question 7

Maltase

Answer 7

~ enzyme produced in intestinal vili

~ breaks down maltotriose + maltose

Question 8

Sucrase + Lactase

Answer 8

~ enzyme produced in intestinal vili
~ sucrase breaks down fruit and table sugar
~ lactase breaks down milk sugar

Question 9

Monosaccharides…

Answer 9

~ are absorbed by enterocytes of intestinal mucosa

~ are polar + hydrophilic –> need specific transport proteins to enter the cell

Question 10

GLUT1

Answer 10

active co-transport of glucose and Na+ into the enterocyte

Question 11

GLUT5

Answer 11

facilitated diffusion of fructose into enterocyte

Question 12

GLUT2

Answer 12

facilitated diffusion of glucose and fructose out of enterocyte and into interstitial space

Question 13

Glucose + the liver

Answer 13

~ maintains glucose homeostasis
~ takes in glucose using GLUT2
~ glucokinase phosphorylates glucose, trapping it in the hepatocyte –> either respired or converted to glycogen (stored)

Question 14

GLUT2 + the liver

Answer 14

~ it has a low affinity for glucose

~ only works due to high capacity for uptake when glucose lvls are high

Question 15

Glucose phosphorylation

Answer 15

~ creates glucose-6-phosphate

~ done by glucokinase and hexokinase (isoenzymes)

Question 16

Glucokinase

Answer 16

~ liver
~ low affinity
~ high capacity
~ more efficient if glucose lvl are high
~ good for storage

Question 17

Hexokinase

Answer 17

~ muscles and other tissues
~ high affinity
~ more efficient at lower glucose conc.
~ good for immediate need

Question 18

Isoenzyme

Answer 18

multiple forms of the same enzyme that catalyse the same reaction, they have diff chemical and physical properties

Question 19

Glycolysis regulation methods

Answer 19

1. enzyme kinetics/isoenzymes
2. enzyme distribution + diff cell/tissue types
3. allosteric control
4. hormonal regulation/reversible phosphorylation

Question 20

Glycogen (5)

Answer 20

~ a'(1-40 and a'(1-6) = branched
~ protein core = glycogenin
~ helical structure
~ semi soluble as low osmotic pot. --> no bursting pot.
~ made from glucose-6-phosphate