Lect 10 Integration of Metabolism

Question 1

Preferred Energy Sources of Different Cell Types:

RBC

Brain

Adipose

Liver

Muscle

Answer 1

RBC: Glucose

Brain: Glucose and Ketones

Adipose: Glucose and FA

Liver: FA (B-oxidation)

Muscles: Glucose, FA, AA

Question 2

What is Adipose Tissue’s function?

How do FAs travel in the blood?

Answer 2

Synthesizes/Store TAGs (insulin)

Release FA and glycerol (glucagon/epi)

FA attached to Albumin in Blood

Question 3

How much oxygen does the brain utilize?

Answer 3

20% total O₂ consumed by resting human (2% of body mass)

Question 4

How does the Heart generate energy?

What does it use?

What will lack of O₂ cause?

Answer 4

• Exclusively aerobic
• Uses: Glucose, Lactate, FA, Ketones Bodies
  
  • No glycogen stores
• Lack of O₂ leads to tissue death (MI)

Question 5

How does Skeletal Muscle produce energy?

Can it export glucose?

What else will it use if lack of glucose?

Answer 5

• Glycogen (75% of body’s stores) broken down to G6P for glycolysis
• Lacks G6 Phosphatase, so muscle cannot export
• FA and Ketone bodies

Question 6

What is the ATP/PCr Energy System

What enzyme catalyzes ATP production?

Answer 6

• Quick exhaustion of ATP stores (1-2 sec)
• Metabolism of phosphocreatine –> creatine via phosphocreatine kinase produces ATP
  
  • PCr stored in muscle to quickly regenerate ATP from ADP

Question 7

What is the Anaerobic Glycolysis Energy System

What forms in the absence of O₂?

How is it recycled?

Answer 7

• Oxidation of glucose or glycogen (glycogenolysis)
• Lactate formation
  
  • Glycogen –> G6P –> Pyruvate –> Lactate
• Cori Cycle: Lactate sent to liver to regenerate glucose

Question 8

What is Oxidative Phosphorylation?

Why does proton pumping occur?

What produces ATP?

Answer 8

• Production of energy from oxidation of coenzymes NADH/FADH2 (2.5/1.5) in the ETC
• To establish PMF
• ATP Synthase

Question 9

Energy charge of a cell defined as the ratio of _

Answer 9

ATP to ADP

Question 10

Reducing power of a cell is defined as the ratio of _

Answer 10

NADH to NAD+

Question 11

What is secreted by SI in response to meal to signal satiation?

Short term or long term?

Answer 11

• Cholecystokinin (CCK) –> Blood –> GPCR peripheral neurons in Brain
  
  • Postprandial Signal: Decrease Food Intake / BW
• Glucagon-Like Peptide 1 (GLP-1) –> Brain and Pancreas
  
  • Increase insulin secretion and biosynthesis
• Short Term Signals

Question 12

What is Ghrelin and where is it secreted from?

Where does it act on?

Answer 12

Peptide secreted from stomach

Acts on Hypothalamus to stimulate appetite

Question 13

What two signal molecules regulate Energy Homeostasis?

Where are they secreted from?

Answer 13

• Leptin: secreted by adipocytes (reports on status of TAG stores)
• Insulin: secreted by B-cells (reports on status of blood glucose)

Question 14

What is the Overall Energy Sensor in the Cell?

When is it active/inactive?

Competition between what 2 substrates determines activity?

Answer 14

AMP-Activated Protein Kinase (AMPK)

ATP is High: AMPK inactive

ATP is Low: AMPK allosterically activated and phosphorylates targets controlling cellular energy production/consumption

Competition between ATP and AMP for AMPK allosteric sites determines activity of AMPK