integration of metabolism

Question 1

where does the metabolism of fatty acids and carbohydrates occur

Answer 1

it occurs in different extents in different organs reflecting the metabolic needs and function of the tissue

Question 2

What does the brain use as its source of energy

Answer 2

under normal conditions- glucose and aerobic metabolism

Question 3

what does the brain use as a source of energy when the body is in resting state

Answer 3

When the body is the resting state, the brain has high respiratory rate, O2 consumption & uses about 60% of the available glucose

Cannot use fatty acids (fatty acids will not cross the blood brain barrier)

Therefore under conditions of starvation the brain will use Ketone bodies

Question 4

what does the skeletal muscle use as fuel under resting conditions

Answer 4

fatty acids

Question 5

what happens when the skeletal muscles start working

Answer 5

muscle will break down its own stores of glycogen to produce glucose-6-phosphate.

If the production of pyruvate exceeds the oxygen capacity of the muscle cell, then pyruvate is converted Into lactate.

Question 6

what is the purpose of the liver

Answer 6

ensures adequate supply of blood glucose for the brain, muscle and RBCs
it also converts excess fuel into fatty acids- fatty acids are transported from the liver for storage in adipose tissue

Question 7

during fasting what will the liver convert fatty acids into

Answer 7

acetoacetate and other ketone bodies

Question 8

what is the ratio in a well fed state

Answer 8

insulin : glucagon ratio is higher

Question 9

what is the ratio in a fasting state

Answer 9

glucagon : insulin ratio is higher

Question 10

what does adipose tissue rely on

Answer 10

Does not have a high energy requirement but
does rely on a supply of glucose for glycolysis.

Question 11

how is TAG produced in adipose tissue

Answer 11

Glycolysis will produce glycerol-3-phosphate
+ fatty acids to produce triacylglycerol (TAG)

Question 12

what is TAG production regulated by

Answer 12

hormonal signals

Question 13

where are GLUT proteins found

Answer 13

in the plasma membranes of various cells and are responsible for glucose uptake from blood stream

Question 14

where is GLUT 1 found

Answer 14

RBCs

Question 15

where is GLUT 2 found

Answer 15

liver

Question 16

where is GLUT 3 found

Answer 16

brain

Question 17

where is GLUT 4 found

Answer 17

adipose and muscle- mobilised to cell membrane by insulin

Question 18

what type of hormone is insulin

Answer 18

anabolic hormone and works to lower blood glucose concentration
it boosts protein synthesis, promotes glycolysis, increases the conversion of carbohydrates to fatty acid

Question 19

When are insulin levels high

Answer 19

when there is high blood glucose, amino acids, glucagon and gastrointestinal hormone levels

Question 20

when is insulin decreased

Answer 20

by fasting, exercise and adrenergic activity

Question 21

what is glucagon

Answer 21

a peptide hormone- 29 amino acids produced by the a-cells of the pancreas
Secreted in response to low blood glucose and high circulatory levels of gluconeogenic amino acids
Secretion inhibited by insulin and by high blood glucose conc

Question 22

what type of hormone is glucagon

Answer 22

a catabolic hormone - works to raise blood glucose concentration, Promotes glycogen breakdown
Stimulates fat breakdown - lipolysis.

Question 23

when is glucagon released

Answer 23

when there is low blood glucose & adrenaline

Question 24

what tissues does glucagon target

Answer 24

liver, fat cells, heart muscle

Question 25

what type of hormone is cortisol

Answer 25

a steroid hormone produced by the adrenal cortex and has increased secretion during stress and works to raise blood glucose concentration

Question 26

what does cortisol do when insulin concentration falls

Answer 26

it increases protein mobilisation via proteolysis

Question 27

what does the insulin : glucagon ratio determine

Answer 27

levels of circulating glucose

Question 28

what does the insulin : glucocorticoid ratio determine

Answer 28

determines the net protein turnover and availability of circulating amino acids

Question 29

what occurs in early starvation

Answer 29

Fatty acids cannot penetrate the Blood Brain Barrier

Brain and RBC use glucose derived mainly
from Amino Acids

The switching by Peripheral tissues to use fats as a source of energy conserves glucose for use by the brain and RBC’s

Question 30

what occurs in prolonged starvation

Answer 30

there is Excess Acetyl CoA and this produces ketone bodies
Ketone bodies are used as a fuel source by the brain to help preserve glucose for use by the RBC’s and suppress the loss of skeletal muscle protein

when fat stores depleted - No acetyl CoA, Gluconeogenesis ceases, Blood glucose rapidly drops, No fuel in blood (coma and death)