Lecture 9: Integration of Metabolism

Question 1

What is the only organ that can carry out all metabolic pathways?

Answer 1

Liver

Question 2

What are the 3 molecules that act as metabolic junction points?

Answer 2

1. glucose-6-phosphate
2. pyruvate
3. acetyl-CoA

Question 3

What can glucose-6-phosphate be broken into?

Answer 3

glycogen, pyruvate, ribose-5-phosphate

Question 4

What can pyruvate be broken into?

Answer 4

acetyl-CoA, lactate, alanine, OAA

Question 5

What can acetyl-CoA be broken into?

Answer 5

CO2 (completely), ketone bodies, fatty acids

Question 6

What are the preferred energy sources of:

1. RBCs
2. Brain
3. Adipose
4. Liver
5. Muscles

Answer 6

1. RBCs –> glucose
2. Brain –> glucose, ketone bodies
3. Adipose –> glucose, fatty acids
4. Liver –> fatty acids
5. Muscles –> glucose, fatty acids, amino acids

Question 7

What signals effect Adipose tissue in the Fed and Hunger/Exercise states?

Answer 7

Fed: Insulin (synth/store triglycerides)

H/E: glucagon/epinephrine (release FA and glycerol)

Question 8

How much O2 is consumed by the brain?

Answer 8

• 20% of consumed O2 in resting human (2% 0f body mass)

- brain uses ketone bodies after days of low glucose consumption (prevents protein breakdown)

Question 9

What enzyme does skeletal muscle lack that prevents glucose export?

Answer 9

glucose-6-phosphatase

Question 10

What energy system is used during immediate (0-30s), short-term (30-120s), and long-term (120s

Answer 10

immediate = ATP/PCr system

short-term = anaerobic glycolysis

long-term = oxidative system

Question 11

What is phosphagen and how does it work?

Answer 11

regeneration of ATP by phosphocreatine (very fast, low total energy)

• use: short burst, heavy activity; quick ATP exhaustioin
• phosphocreatine stored in muscle (quick ATP regeneration)

Question 12

What is Anaerobic Glycolysis and how does it work?

Answer 12

• oxidation of free blood glucose/glycogen
• leads to lactate formation (dec. power & muscle fatigue)
• glycogen –> G6P –> pyruvate –> lactate

Question 13

What is the Cori Cycle and what does it do?

Answer 13

• regenerates glucose from lactate

- liver uses lactate to produce glucose via gluconeogenesis

Question 14

What is Oxidative Phosphorylation and how does it work?

Answer 14

• produces energy from NADH and FADH2 oxidation

NADH - 2.5 ATP
FADH2 - 1.5 ATP

• ATP Synthase produces ATP

Question 15

ATP:ADP and NADH:NAD Ratios

Answer 15

• Energy Charge (ATP:ADP)
• Reducing Power (NADH:NAD)

ratios are INVERSE

• ATP lvls low = TCA Cycle upregulation (More NADH)
• ATP lvls high = TCA downregulated (Less NADH)

Question 16

Short Term Satiation Signals (Cholecystokinin, Glucagon-like Peptide 1, Ghrelin)

Answer 16

CCK - small intestine secreted; acts on brain
- increased satiety, dec. food intake/body weight

GLP-1 - L-cell secreted; acts on brain, pancreas

• inc. insulin sec/biosynthesis, satiety
• dec. food intake/body weight

Ghrelin - stomach secreted; acts on hypothalamus

• stimulate appetite
• inc. before meal, dec. after meal

Question 17

Leptin

Answer 17

• adipose tissue secreted in proportion to fat mass
• leptin receptor = hypothalamus
• regulate body weight (dec. food intake, inc. NRG use)

Question 18

Long Term Homeostasis Control (2 molecules)

Answer 18

• regulate energy homeostasis (hours or days)
• Leptin: adipocytes (triacylglycerol store status)
• Insulin: pancreas B cells (blood glucose status)

Question 19

What is AMPK and why is it important?

Answer 19

• AMP-activated protein kinase = cellular NRG sensor
• ATP HIGH –> AMPK is inactive
• ATP LOW –> AMPK allosterically activated
  
  • phosphorylates targets controlling cellular NRG production and consumption

ATP/AMP competition determines AMPK on/off