Chapter 22: Mammalian Fuel Metabolism

Question 1

How do organisms coordinate their metabolic processes?

Answer 1

So opposing pathways do not operate simultaneously. And so organism can respond to changing external conditions like nutrient availability.

Question 2

What is the interconnectedness of various tissues ensured by?

Answer 2

Neuronal circuits and hormomes.

Question 3

Overview of metabolism:

Answer 3

Question 4

What organ carries out all metabolic pathways?

Answer 4

Liver

Question 5

Most to least metabolically active tissues:

Answer 5

Liver > Adipose Tissue > Muscle Tissue

Question 6

How much glucose does the brain require?

Answer 6

~ 20% of O2 and ~20% of glucose

Question 7

What does the brain use O2 and glucose for?

Answer 7

Aerobic energy powers the Na+K+ ATPase that maintains membrane potentials to conduct nerve impulse transmission.

Question 8

The brain does not store _____ well.

Answer 8

Glycogen

Question 9

_____ and ______ function to support nerve cells.

Answer 9

Astrocytes, Oligodendrocytes

*Carry out anaerobic metabolism and can supply lactate to nerve cells for further break down.

Question 10

How much glycogen do muscles store?

Answer 10

1-2% of its mass is glycogen.

Question 11

If fatty acids are a more energy-dense fuel, then why is it not preffered?

Answer 11

Glucose is easier to burn and can burn aerobically or anaerobically. Fatty acids can ONLY be burned under aerobic conditions.

Question 12

In what conditions is muscle contraction anaerobic?

Answer 12

High exertion. At rest muscle consumes ~30% O2.

Question 13

How does muscle respiration rate change?

Answer 13

Under strenuous exercise, it will increase by 25% or more and ATP hydrolysis can increase even more.

Question 14

How can ATP be regenerated for muscles?

Answer 14

Phosphocreatine, but only lasts for about 4 seconds. Then the muscle switches to anaerobic metabolism.

Question 15

The heart cells have how many mitochondria?

Answer 15

~40% of cytoplasm is mitochondria in cardiomyocytes (cardiac muscle cells) .

Question 16

What is the resting hearts fuel of choice?

Answer 16

Fatty acids, but will switch to glucose as heart rate increases.

Question 17

The heart has a ____ supply of glycogen.

Answer 17

limited

Question 18

What are the fuels that the heart uses?

Answer 18

Fatty acids

Ketone Bodies

Glucose

Pyruvate

Lactate

Question 19

What is the function of adipose tissue?

Answer 19

To store and release fatty acids as needed for fuel as well as to secrete hormones involved in regulating metabolism.

Question 20

Where is adipose tissue found?

Answer 20

Found under the skin, abdominal cavity, skeletal muscles.

Question 21

How long can fat storage provide fuel for?

Answer 21

Average person ~ 3 months

Question 22

Adipocytes require most of their fat through?

Answer 22

Circulating lipoproteins.

Question 23

How can adipocytes hydrolyze triacylglycerols?

Answer 23

They do so when glucose levels are low and hormones regulating this process are abundant.

Question 24

When are fatty acids released into the bloodstream to be metabolized?

Answer 24

When glycerol-3-phosphate levels are low.

Question 25

Where do all the nutrients absorbed by small intenstines go?

Answer 25

Directly into the liver by the portal vein (except for fatty acids)

Question 26

What can liver synthesize or degrade?

Answer 26

Triacylglycerols

Question 27

The liver acts as a ______

Answer 27

blood glucose buffer

Question 28

What does the kidney mainly do?

Answer 28

Filters urea and other waste products from the blood while recovering important metabolites like glucose.

Question 29

How does the kidney maintain blood pH?

Answer 29

Regenerating depleted blood buffers like HCO3- and excreting excess H+ together with the conjugate bases of excess metabolic acids. Such as ketone bodies acetoacetone and B-hydroxybutarate.

Question 30

How does kidney work in deamination reactions?

Answer 30

Excretes excess H+ in the form of NH4+

Question 31

During starvation, how does kidney do its job?

Answer 31

Can synthesis glucose through gluconeogenesis, supplying 50% of the body's glucose needs.

Question 32

Blood transports metabolites in interorgan metabolic pathways (diagram):

Answer 32

Question 33

What do hormones do?

Answer 33

Enable body to maintain metabolic homeostasis.

Question 34

When is insulin released?

Answer 34

Released by pancreas when glucose is consumed.

Question 35

What does insulin do?

Answer 35

Promotes fuel storage in muscle and adipose tissue. Blocks gluconeogenesis and glycogenolysis.

Question 36

What does glucagon do?

Answer 36

Stimulates fatty acid mobilization from adipose tissue by activating hormone-sensitive lipase.

Question 37

What doe catecholamines do?

Answer 37

Mobilize fatty acids and promote break down of glucose. Catecholamines - epinephrine, norepinephrine, and dopamine

Question 38

Overview of hormone actions:

Answer 38

Question 39

Roles of AMP-dependent protein kinase (4):

Answer 39

1. activates glycolysis in ischemic cardiac muscle 2. inhibits lipogenesis and gluconeogenesis in liver 3. promotes fatty acids oxidation and glucose uptake in skeletal muscle 4. inhibits lipolysis in adipocytes

Question 40

Adiponectin is a hormone that does what?

Answer 40

Secreted by adipocytes that helps to regulate metabolism. Regulates AMPK activity.

Question 41

What is the satiety hormone?

Answer 41

Leptin

Question 42

What hormones are the short term regulators of appetite?

Answer 42

Ghrelin and PYY 3-36

Question 43

How are calories utilized?

Answer 43

Performance of work or release of heat.

Question 44

Type 1 diabetes:

Answer 44

Insulin-dependent, juvenile-onset

Question 45

Type 2 diabetes:

Answer 45

Non-insulin-dependent, maturity-onset

Question 46

What is insulin-dependent diabetes caused by?

Answer 46

Deficiency of pancreatic b cells.

Question 47

Cancer cells have a high rate of?

Answer 47

Glucose metabolism through aerobic glycolysis.

Question 48

____, ______, and _____ supports the rapid growth and proliferation of cancer cells.

Answer 48

Glucose Amino acids Glutamine

Question 49

_____ and _____ metabolism support anabolic processes.

Answer 49

Glutamine Glutamate