Carbohydrate and glucose management

Question 1

Where in the body does degredation of carbohydrates start and which enzyme is responsible?

Answer 1

In the mouth: amylase

Question 2

What carbohydrate polymer cannot be degraded and what are these polymers called?

Answer 2

Cellulose for instance, this is a fiber

Question 3

How can fiber still be degraded?

Answer 3

By certain bacteria in the gut

Question 4

Is glucose transport and uptake active or passive?

Answer 4

Glucose in the gut is transported from a high to low concentration so this is active uptake and it costs ATP

Question 5

What is the problem in lactose intolerance?

Answer 5

You lack the enzyme lactasa, so you cannot break the bond between glucose and galactose.

Question 6

What causes bloating in lactose intolerant people

Answer 6

Bacteria in the intestinal lumen will break down the lactose, releasing gas and lactic acid

Question 7

What causes diarrhea in lactose intolerance

Answer 7

The increase in lactic acid increases the osmotic level, causing water to transport into the gut

Question 8

What is the difference between galactosemia and lactose intolerance?

Answer 8

Individuals with lactose intolerance cannot breakdown lactose into galacase and glucose but galactosemia is involved in further metabolizm of lactose: breaking down of galactose

Question 9

What is galactosemia?

Answer 9

A condition where galactose cannot be further metabolized leading to toxic levels of galactose 1-phosphate can cause serious damage

Question 10

What is fructosemia and when is not serious?

Answer 10

Lack of enzymes that can degrade fructose.
- if fructokinase is missing, the fructose cannot be converted but this can just end up in the urine
- if aldolase B is missing, fructose 1-P will build up inhibiting gluconeogenesis and glycogen degredation

Question 11

What 2 main organs store glycogen?

Answer 11

Muscle and liver

Question 12

What is the difference between glycogen storage in muscle and liver?

Answer 12

The liver can regulate blood glucose level with its glycogen stores: homeostasis. But the muscle uses the glycogen stores as energy for the muscle

Question 13

What enzyme is used for glycogen synthesis and which one for mobilization?

Answer 13

Glycogen synthase and glycogen phosphorylase

Question 14

Explain the glucose –> glycogen pathway using the main enzyme

Answer 14

Glucose –> glucose-6-P –> glucose 1-P –> UDP’s are formed by UDP-glucose-pyrophosphorylase by turing UTP into UDP –> glycogen synthase connects these UDP’s into glycogen

Question 15

Explain the glycogen –> glucose pathway using the main enzyme

Answer 15

Glycogen debranched –> Phasphates are added by Glycogen phosphorylase into glucose-1-P

Question 16

Why is glycogen branched?

Answer 16

So that glycogen phosphorylase can act on multiple sites at a time: Speed

Question 17

How is the uptake of glycogen regulated in muscle and liver

Answer 17

by insulin

Question 18

How is the release of glycogen regulated in muscle and liver

Answer 18

• liver: only needs to be released when body needs it, so responses to glucagon and epinephrine (during fight or flight)
• muscle: only responses to excercise, so also epinephrine or activity of muscle so Calcium release. but not glucagon

Question 19

What is protein kinase A

Answer 19

enzyme that phosphorylates other enzymes/molecules

Question 20

What is the effect of insulin on glycogen phosphorylase and glycogen synthase

Answer 20

Insulin present when glucose high, so insulin dephosphorylates glycogen phosphorylase (making it inactive) and dephosphorylates glycogen synthase (making it active)

Question 21

What do glucagon and epinephrine both activate and what is the result?

Answer 21

activation PKA –> phosphorylation of glycogen synthase (making it inactive) and glycogen phosphorylase (making it active)

Question 22

Is phosphorylated Glycogen synthase active?

Answer 22

no

Question 23

Is phosphorylated glycogen phosphorylase active?

Answer 23

yes

Question 24

What are the glucose regulations in muscle

Answer 24

• external: nerve impulses –> higher calcium –> activates “phosporylase kinase” –> phosphorylates “glucagon phosphorylase” (active) –> breakdown glucogan into glucose for muscle fuel
• internal: during muscle contraction ATP used generating AMP –> AMP binds to “glycogen phosphorylase” (active due to confirmational change)