Lecture 29

Question 1

How is energy used during exercise?

Answer 1

The stored energy sources are used sequentially: stored high-energy phosphate bonds (ATP, creatine phosphate) followed by glycogen, circulating glucose, and circulating FFAs

Question 2

How does the metabolic response to exercise resemble to response to fasting?

Answer 2

Mobilization and generation of fuels for oxidation are dominant factors

Question 3

In what ways can carbohydrates be used in an absorptive state?

Answer 3

Absorbed as glucose
1. Used immediately for energy through aerobic pathways
2. Used for lipoprotein synthesis in liver
3. Stored as glycogen in liver and muscle
4. Excess converted to fat and stored in adipose tissue (glucose -> pyruvate -> acetyl CoA -> fatty acids)

Question 4

In what ways can proteins be used in an absorptive state?

Answer 4

Absorbed primarily as amino acids
1. Most amino acids go to tissues for protein synthesis
2. If needed for energy, amino acids converted in liver to intermediates for aerobic metabolism
3. Excess converted to fat and stored in adipose tissue (amino acids -> acetyl CoA -> fatty acids)

Question 5

In what ways can fats be used in an absorptive state?

Answer 5

Absorbed primarily as triglycerides
1. Stored as fats in liver and adipose tissue

Question 6

Lipogenesis

Answer 6

Free fatty acid pool -> fat stores

Question 7

Lipolysis

Answer 7

Fat stores -> free fatty acid pool

Question 8

Lipogenesis

Answer 8

Excess glucose -> fat stores

Question 9

Glycogenesis

Answer 9

Glucose pool -> glycogen stores

Question 10

Glycogen stores

Answer 10

~100g of glycogen in liver
~200g of glycogen in skeletal muscle

Question 11

Glycogenolysis

Answer 11

Glycogen -> Glucose pool

Question 12

Protein Synthesis

Answer 12

Amino acid pool -> body protein

Question 13

Gluconeogenesis

Answer 13

Amino acid pool -> Glucose pool

Question 14

Glucose Sparing

Answer 14

• Release of energy during the interdigestive period or an extended fasting (fat utilization)
• During fasting, both skeletal muscle and adipose tissue contribute directly to circulating blood glucose through the release of gluconeogenic substrates (lactate, amino acids, glycerol) and indirectly through the release of free fatty acids (FFA) -> allow skeletal muscle and other tissues to consume less glucose
• Release of FFAs and ketogenic amino acids supports ketogenesis by liver
• Ketone bodies thus produced can be utilized for ATP production (brain)

Question 15

Ketogenesis

Answer 15

Ketogenic amino acids converted to acetyl CoA

Question 16

What are skeletal muscle and adipose tissue promoted by?

Answer 16

Glucagon or epinephrine/norepinephrine or both

Question 17

What receptor transports glucose out of liver cells?

Answer 17

GLUT2

Question 18

What receptor transports glucose into the brain?

Answer 18

Glucose -> GLUT3 -> ATP

Question 19

How to islets influence eachother?

Answer 19

Paracrine and autocrine communication

Question 20

Alpha cells

Answer 20

Secrete glucagon

Question 21

Glucagon

Answer 21

Increases glucose blood levels

Question 22

Beta cells

Answer 22

Secrete insulin

Question 23

Insulin

Answer 23

Increases transport of glucose into cells (ex: hepatocytes and skeletal and cardiac muscle cells)

Question 24

Delta cells

Answer 24

Secrete gastrin and somatostatin

Question 25

Gastrin

Answer 25

Stimulates production of HCl by parietal cells in the stomach

Question 26

Somatostatin

Answer 26

Inhibits the release of insulin and glucagon, and the secretion of HCl by parietal cells

Question 27

Delta-1 Cells (D1)

Answer 27

Produce vasoactive intestinal polypeptide (VIP)

Question 28

Vasoactive Intestinal Polypeptide (VIP)

Answer 28

Induces glycogenolysis and hyperglycemia and stimulates GI fluid secretion

Question 29

PP Cells

Answer 29

(gamma or F) produce pancreatic polypeptide

Question 30

Pancreatic Polypeptide

Answer 30

Inhibits the secretion of somatostatin and the CCK-stimulated secretion of pancreatic enzymes

Question 31

Islet of Langerhans

Answer 31

• Display alpha and beta cells in relationship with each other throughout the cluster
• Beta cells are coupled electrically to other beta cells (but not to other cell types)
• Each islet consists of 2000 to 3000 cells surrounded by a network of fenestrated capillaries and supported by reticular fibers

Question 32

Insuloacinar Portal System

Answer 32

• Vascular component
• Enables a local action of insular hormone on the exocrine pancreas