Summary of Metabolism

Question 1

Each metabolic fuel has 3 forms. What are they?

Answer 1

1. Storage form
2. Transport form
3. Interacellular metabolite form

Question 2

When fatty acid oxidation is excessive, the excess acetyl-CoA is converted into

Answer 2

ketone bodies

Question 3

Carbohydrates and proteins can be converted to lipids. T/F

Answer 3

True

Question 4

Carbohydrates can be used for the synthesis of non essential amino acids.T/F

Answer 4

True

Question 5

Acetyl-CoA can not be converted into ….. and so it can not be used for gluconeogenesis or protein synthesis

Answer 5

pyruvate

* The enzyme pyruvate dehydrogenase catalyzes an irreversible reaction with no opposite enzymes in humans to reverse it.

Question 6

The shifting between the storage and transport form, as well as the type of the fuel being metabolized is well under the control of …….

Answer 6

ratio of insulin/glucagon

Question 7

Insulin action is opposed by ….., ….., ….. & …..

Answer 7

glucagon, cortisol, growth hormone & epinephrine

Question 8

The major targets for insulin action are …., …. & ….

Answer 8

liver, muscle & adipose tissue

Question 9

After the glycogen reserves are filled, liver converts excess glucose to …… .

Answer 9

Fatty acids

* Insulin promotes fatty acids and protein synthesis

Question 10

HMP shunt activity varies with the body’s need for …..

Answer 10

NADPH for fatty acids and cholesterol synthesis

Question 11

Glucagon and epinephrine activity ….. during overnight fast, and HMP shunt activity is …..

Answer 11

increased, decreased

Question 12

During overnight fast, gluconeogenesis response is …… than glycogenolysis under glucagon activity

Answer 12

slower

Question 13

During fasting, amino acids provides the …… while fatty acids provide ….. necessary for gluconeogenesis

Answer 13

carbon skeleton, ATP

Question 14

During prolonged fasting, levels of …… & ….. are increased

Answer 14

ketones & fatty acids

* This is in response to elevated levels of glucagon and epinephrine

Question 15

During prolonged fasting, the brain adapts to using …. for energy, while the muscles use ……. . This shifting in form of energy used is to conserve protein

Answer 15

ketones

fatty acids

Question 16

Protein has no transport form. T/F

Answer 16

False

it has not “storage” form, because each protein has a specific function in the cell

Question 17

HMP shunt activity is …….. during prolonged starvation state

Answer 17

non existent

Question 18

What are the cells that depend entirely on glucose for energy?

Answer 18

RBCs and renal medullary cells, because they lack mitochondria

Question 19

Complete combustion of fat produce ……

Answer 19

9 kcal/g

* Fats produce much more energy than other sources of energy

Question 20

Most carbohydrates are stored as ….. in the body. A small fraction of the total carbs is found free

Answer 20

glycogen

Question 21

Why protein sparing is important during periods of starving or prolonged fasting?

Answer 21

Because degradation of more than one third of total body protein is incompatible with life

Question 22

The utilization of fuel depends on ….. & ……

Answer 22

1. tissue studied

2. metabolic state

Question 23

Gluconeogenesis, lipolysis & proteolysis are all activated during …… . The decrease in proteolysis and carbohydrate utilization is due to ……

Answer 23

fasting state

accumulation of Acetyl-CoA, which leads to inhibition of pyruvate dehydrogenase

Question 24

The main fuel for muscles is …. & ….. in the well fed state

Answer 24

glucose & fatty acids

* Skeletal muscles are the body’s major energy consumer

Question 25

Lactate accumulates when ....... during intense muscle contraction

Answer 25

pyruvate production exceeds the TCA cycle to carry out terminal oxidation

Question 26

In the fasting state, muscles use .... & ...... while sparing glucose for the brain and the RBC

Answer 26

fatty acids and ketone bodies

Question 27

Why the cardiac muscle has much higher oxidative capacity than skeletal muscles?

Answer 27

Because of their higher number of mitochondria

Question 28

Cardiac muscle uses ........ & ...... during well fed state, and ...... & ...... during fasting state

Answer 28

glucose & fatty acids | fatty acids and ketones

Question 29

The brain relies primarily on ..... for energy, because ...... can not cross the BBB. During fasting state, the brain can use ..... for energy, although it supplies only 2/3 of the demand, the remaining one third is supplied by .....

Answer 29

glucose fatty acids ketone bodies glucose

Question 30

The renal cortex mainly uses .... for energy, while the medula uses ...... . However, they kidney can utilize all types or fuels for energy

Answer 30

fatty acids | glucose

Question 31

The two main energy roles for the liver is to ....... & ......

Answer 31

maintain level of blood glucose | synthesize ketones when excess fatty acids are being oxidized

Question 32

During well fed state, the liver derives most of its energy from oxidation of ....

Answer 32

excess amino acids

Question 33

Insulin stimulates the release of fatty acids from ..... & ..... by activating the enzyme .....

Answer 33

VLDL & chylomicrons | LipoprotienLipase

Question 34

During fasting, glucagon and epinephrine activate ....... to mobilize fatty acids from adipose tissue

Answer 34

hormone sensitive lipase

Question 35

....... is the only hormone in humans that promotes fuel storage.It is release from the pancreas is related to the elevated level of .......

Answer 35

Insulin | blood glucose

Question 36

What are the catabolic hormones?

Answer 36

glucagon, epinephrine, nor epinephrine, growth hormone, cortisol

Question 37

For hormones to generate signal in the cell, explain the steps that should occur

Answer 37

1. Hormone binds to membrane g protein coupled receptor. G protein is activated 2. The receptor communicates with adenylate cyclase through G protein (This protein uses GTP for energy to start communicating) 3. Adenylate cyclase causes increase in intracellular cAMP 4. cAMP activates protein kinase enzyme, which in turn phosphorylates the intracellular enzyme (activation may increase or decrease activity) 5. Removal of the phosphate group and restoration of the original state by protein phosphatase see P. 361

Question 38

The hormone receptor complex can bind to DNA ...... or ...... sequence with the result of increase or decrease mRNA synthesis

Answer 38

enhancer & silencer

Question 39

The enhancer region in the DNA has no effect alone unless it is bound to .....

Answer 39

hormone receptor complex | * this binding increases the rate of transcription

Question 40

What are the catabolic hormones that activate adenylate cyclase?

Answer 40

glucagon, epinephrine and nor epinephrine

Question 41

Glucagon release is stimulated by ....., it acts mainly on ..... to increase ..... & ...... and inhibit .....

Answer 41

low glucose, liver glycogenolysis, gluconeogenesis glycolysis see p. 363 table

Question 42

What are the effects of epinephrine and nor epinephrine on alpha & beta receptors?

Answer 42

1. Alpha: on the liver, activate second messengers (Ca, diacylglycerol) and stimulate other protein kinase, leading to glycogenolysis and gluconeogenesis 2. Beta: located on muscles, causes activation of adenylate cyclase and increasing cAMP levels. increasing glycogenolysis and lipolysis (in adipose tissue) * Catecholamines are released in response to hypoglycemia

Question 43

What is the effect of insulin on cAMP?

Answer 43

It causes activation of cAMP phosphodiesterase, which degrades cAMP and causing activation of protein phosphatase (this shifts equilibrium from the phospho to dephospho form of these enzyme)

Question 44

Glucagon and insulin have effect on mRNA synthesis. T/F??

Answer 44

True | They effect the rate of synthesis for the regulatory enzymes in gluconeogenesis and glycolysis

Question 45

Cortisol causes increased ......, ....... & .....

Answer 45

proteolysis (activated proteases), lipolysis ( activate hormone sensitive lipase), gluconeogenesis (increase PEPCK & FBPase)

Question 46

Thyroid hormones metabolic effects include ....., ....., ...... & ..... . They also have effect on the rate of gene expression

Answer 46

increase O2 consumption, hyperthermia, hyperglycemia, and decrease cholesterol

Question 47

The activity of cAMP is shut off by the enzyme .....

Answer 47

phosphodiesterase