Module 10: Metabolism

Question 1

Glucose

Answer 1

Glucose is broken down to pyruvate through glycolysis, then to acetylCoA via the PDH reaction, then to carbon dioxide through the citric acid cycle.
The reducing equivalents, NADH and FADH2, that are generated from these processes are then converted to ATP through ETC and OxPhos

Question 2

Fats

Answer 2

Fats are broken down from triacylglycerols to free glycerol and fatty acids.
The glycerol feeds into glycolysis, while the fatty acids will be broken down to acetylCoA through beta oxidation.
The acetylCoA feeds into CAC
Reducing equivalents generated from beta-oxidation and CAC are converted to ATP through ETC and OxPhos

Question 3

Proteins

Answer 3

Proteins are broken down to their individual amino acids

Question 4

Preferred fuels

Answer 4

Brain prefers glucose
Muscle
- at rest, burn fatty acids
- during exercise, switch to more glucose
Heart prefers fatty acids (receives through circulation)
Adipose tissue prefers fatty acids
Liver uses any of the three macronutrients

Question 5

Liver storage and function

Answer 5

store glucose as glycogen for the entire body
process all of the fats that are ingested after a meal - repackages it as chylomicrons and sends it out into the circulation for other tissues to pick up as a fuel

Question 6

Adipose storage

Answer 6

Most of our fats are stored in our adipose tissue for longer term storage

Question 7

Skeletal muscle storage

Answer 7

has its own carbohydrate reserves as glycogen and a very small amount of triacylglycerols as well

Question 8

At rest/very low exercise intensities

Answer 8

Production of ATP from fat is able to meet ATP demands

fats are delivered to the muscle via the bloodstream from the adipose tissue as a constant supply

Question 9

Increase in exercise intensity

Answer 9

body begins to rely more heavily on the oxidation of glucose

body relies on a blend of fat and carbohydrate degradation
- fatty acids continue to be supplied via the bloodstream, while the glucose being provided through the bloodstream, originating from the liver

Question 10

High exercise intensity

Answer 10

breakdown of glucose through glycolysis provides the greatest proportion of ATP along with a high energy phosphate compound called creatine phosphate

muscle turns to its own local and immediate stores of glycogen for a rapid supply of glucose

Question 11

Creatine phosphate

Answer 11

High energy phosphate compound that serves as an energy buffer inside of the cell
Readily available to buffer ATP levels as they drop during the onset of exercise or during very high intensity exercise

Creatine is made in our body and consumed when we eat meat

Question 12

Creatine kinase

Answer 12

catalyzes the transfer of a phosphate group from creatine phosphate to ADP to replenish ATP levels when they drop

Question 13

Lactate Production During Exercise

Answer 13

As exercise intensity increases, we shift from a reliance on fat oxidation to a greater reliance on glycolysis of glucose
Downside: lactate is generated as a bi-product of metabolism when the NAD+ must be regenerated in order to allow glycolysis to continue
Lactate results in muscle fatigue and cramping and reduces our ability to continue to exercise at a high level of intensity

Question 14

Immediately Post-prandially (after a meal)

Answer 14

elevated glucose=insulin release from pancreas
signals the uptake of glucose into the tissues, namely muscle and liver
glucose is stored away as glycogen

Question 15

A few hours post-prandially (after a meal)

Answer 15

blood glucose levels begin to drop=glucagon released

stimulates glycogen breakdown in the liver to maintain a constant supply of glucose in the bloodstream

Question 16

Type II diabetes

Answer 16

dysfunction in insulin signaling

regular exercise can help maintain healthy glucose levels and aid in prevention

Question 17

Starvation

Answer 17

any longer than 1/2 day, liver glycogen stores depleted
fat stores in adipose tissue–>FAs taken up from bloodstream by liver –>converted to ketone bodies

after fat reserves depleted, last and not preferred avenue is protein
Protein reserves in muscle can be broken down to its amino acid components: glucogenic amino acids converted to glucose and ketogenic amino acids converted to ketone bodies

Question 18

Glucagon (TB)

Answer 18

stim breakdown of liver glycogen by activating glycogen phosphate and inactivating glycogen synthase
inhibit pyruvate kinase
activate TAG breakdown

Question 19

Epinephrine/Norepinephrine

Answer 19

released from adrenal medulla
dilate resp passages to increase O2 uptake, heart rate and BP
acts primarily on muscle, adipose, liver tissue
activates glycogen phosphorylase and inactivates glycogen synthase
stim glucagon/inhibit insulin
promote anaerobic breakdown of muscle glycogen by lactic acid fermentation

Question 20

Cortisol

Answer 20

released from adrenal cortex in stress
acts on muscle, adipose, liver tissue
slow-acting
increase FA release from stored TAGs 
stim breakdown of nonessential muscle pr-
export aa to liver
promotes gluconeogenesis