Lecture 2: Metabolic Pathways

Question 1

Conversion factor between mmol/L and mg/dL

Answer 1

18* mmol/L = mg/dL

Question 2

How long could an average man survive

Answer 2

~98 Days

Question 3

Glucose Range

Answer 3

4. 6 ( 83) Insulin secretion decreases

5. 5 (99) Insulin secretion increases

Question 4

Brain Glucose Usage

Answer 4

Glucose is the fuel for the human brain
2/3 utilization of glucose goes to the brain
Fatty acids can be used in the brain
After 10+ days, the brain can replace 50% of glucose intake with ketone bodies

Question 5

Liver/Kidney

Answer 5

The only organs that secrete glucose into the bloodstream

Question 6

Glucose Carbon Source

Answer 6

Glucose and ATP are central metabolic molecules

• Minimal metabolic map shows that glucose is the central molecule
• Embden- Meyerhof (EM Pathway)- Commonly known as glycolysis pathway
• Entner- Doudoroff (ED Pathway)- some bacteria can use alternate pathway that arose through convergent evolution

Question 7

Blood Energy Stores

Answer 7

20 g
40 min- still
15 min- walking
4 min- marathon

Question 8

Liver Glycogen Store

Answer 8

80 g
3.5 hours- still
70 min- walking
18 min- marathon

Question 9

Muscle Glycogen Store

Answer 9

350 g
14 hours- still
5 hours- walking
70 minutes- marathon

Question 10

Body Protein

Answer 10

6000 g
15 days still
5 days walking
1.3 days- marathon

Question 11

Fat

Answer 11

9000-15000
34 days- still
11 days- walking
3 days- marathon

Question 12

Glycogen

Answer 12

Increased glucose –> insulin –> Glycogen synthase
- Polymer of glucose molecules branched together
Primarily stored in the liver and muscle, for quick energy reserves
Glycogen synthase in endergonic
Glycogenolysis- The breakdown of glycogen, is exergonic
Glycogenin- Enzyme that catalyzes glycogen synthesis by attaching a glucose molecule to itself

Question 13

Glycogen Enzymes Phosphorylation

Answer 13

Glycogen Synthase Phosphorylation= INACTIVE

Glycogenolysis Phosphorylation= ACTIVE

Question 14

Carb Loading

Answer 14

• Increasing the glycogen stores in the muscle and liver
• Liver increases general stores of energy to decrease fatigue effects
• Muscle can expend more energy

Question 15

Gluconeogenesis

Answer 15

Pyruvate- Glucose
Stimulated by Glucagon
Allows blood glucose to be normal during fasting because glycogen stores are more short term
Amino acids enter through oxoaloacetate
- Fructose enters as DHAP + gluceraldehyde
- Galactose enters near the top as G6P

Question 16

G6P Fates

Answer 16

1. Dephosphorylated and released back into the blood
2. Enters glycolysis to form pyruvate
3. Pentose Phosphate Pathway- for NADPH generation
4. Lipid Synthesis- converted into precursor for the reaction

Question 17

Timeline of Starvation**

Answer 17

Hours
Glycogen breakdown
Gluconeogenesis
Day
Flux of gluconeogenic pathway increased in the brain
Fatty acid breakdown for all other metabolic needs to spare glucose for the brain
Days
Fatty acid breakdown- Triglycerols in the fatty acid tissue
Protein Breakdown- spared as long as possible to preserve motility

Question 18

Cancer and Glycolysis

Answer 18

All cancers have increased rate of glycolysis

PET scans used to track 18F deoxyglucose for tumors

Question 19

Pasteur Effect

Answer 19

Decrease in glycolysis in the presence of oxygen, ATP is inhibitor of glycolytic rate- serves as checkpoint for metabolism

Question 20

Warburg Effect

Answer 20

Cancer cells with undergo lactic acid fermentation even in the presence of oxygen
Theory 1: ATP is not the limiting factor in cancerous cells, biomass for division is. Glucose diverted to provide carbons for biomass, so cancer cells can continue dividing
Theory 2: Trying to limit the amount of superoxide components from oxidative phosphorylation