Carbohydrate Metabolism

Question 1

Glycolysis
Purpose:
Place:
Rate-limiting step:
Regulation:
Checkpoints:

Answer 1

Purpose: create energy from glucose
Place: cytosol of all cells (brain and RBC especially dependent–> only source of energy)
raw materials: glucose (either organically or de novo from gluconeogenesis), fructose, other monosaccharides
Rate-limiting step: PFK-1
Regulation: inhibited by: ATP, glucagon stimulated by: AMP, Insulin, Glucose
checkpoints: glucokinase/hexokinase, PFK1, pyruvate Kinase

Question 2

Glut 1

Answer 2

Location: ubiqutious (erythrocytes, brain, cornea, placenta, cancer)
Regulation: unregulated
Affinity: high–> brain

Question 3

Glut2

Answer 3

Location: liver & pancreas
Regulation: unregulated
Affinity: low (abundance)

Question 4

Glut3

Answer 4

Location: neurons
Regulation: unregulated
Affinity: High (again, brain cells)

Question 5

Glut4

Answer 5

Location: skeletal muscle, adipose tissue, heart
Regulation: Regulated by insulin
Affinity: medium-ish

Question 6

glucokinase

Answer 6

localization: liver, pancreas
Km: high
Vm: high
Substrate: glucose only
G6P Inhibition? no

Question 7

hexokinase

Answer 7

localization: all cells
Km: low
Vmax: low
substrate: glucose & co
G6P inhibition: yes

Question 8

Regulation of PFK-1

Answer 8

stimulated by: Insulin

Inhibited by: glucagon

Question 9

Pyruvate Kinase

Answer 9

stimulated: insulin and fructose 1, 6-bisphosphatase
inhibited: ATP, alanine, glucagon

Question 10

Diabetes

Answer 10

Hyperglycemia
Type 1: cannot make insulin because no pancreatic beta cells
type 2: insulin resistance (loss of function)

Question 11

hemolytic anemia

Answer 11

many different causes

premature destruction of red blood cells

Question 12

gluconeogenesis
Purpose:
Place:
Rate-limiting step:
Regulation:
Checkpoints:

Answer 12

Purpose: making glucose from carbs/non-carbs when glucose and glycogen are used up
Place: liver, kidney, small intestine
raw materials: lactate, amino acids, glycerol
Rate-limiting step: fructose 1,6-bisphosphatase
Regulation: inhibited by: ADP, AMP, Fructose 2-6 Bisphosphatase, stimulated by glucagon, citrate, cortisol, thryoxine, acetyl coA
**bypasses irreversible steps of glycolysis

Question 13

Cori Cycle

Answer 13

links lactate made after pyruvate to gluconeogensis in liver

Question 14

Fanconi-Bickel syndrome

Answer 14

mutation in Glut2
cannot take up glucose, fructose, galactose
clinical manifestations: failure to thrive, big liver, kidney dysfunction, bloating

Question 15

Pentose Phosphate Pathway
Purpose:
Place:
Rate-limiting step:
Regulation:
Checkpoints/Other:

Answer 15

Purpose: makes glucose for DNA/RNA formation
Place: cytosol
Rate-limiting step: G6P dehydrogenase
Regulation: high demand of ribose 5P (dividng cells) or NADPH (gluconeogenesis)