2.6 Integration of metabolism

Question 1

What are the energy sources of the brain

Answer 1

ketone bodies and glucose

Question 2

why can the brain not metabolise fatty acids

Answer 2

won’t pass the blood brain barrier

Question 3

What does hypoglycemia cause for the brain

Answer 3

faintness and coma

Question 4

what does hyperglycemia cause for the brain

Answer 4

‘irreversible damage ‘

Question 5

what can the brain use a partial substitute for glucose

Answer 5

beta hydroxybutyrate and other ketone bodies

Question 6

In light contraction how are the energy requirements of skeletal muscles met

Answer 6

by oxidative phosphorylation

Question 7

In vigorous contraction how are the energy requirements of skeletal muscles met

Answer 7

by lactate production and glycogen formation

Question 8

what percentage of body mass do skeletal muscles make up

Answer 8

40%

Question 9

What can the heart metabolise

Answer 9

basically anything

fatty acids, ketone bodies, glucose

Question 10

What are some metabolic processes that happens in the liver

Answer 10

gluconeogenesis
beta oxidation
fatty acid synthesis (also happens in lactating breast and adipose tissue and cancer cells )
ketone body production

Question 11

What concentration does the liver keep blood glucose at

Answer 11

4 - 5.5 mM

Question 12

What can excess glucose - 6 phosphate be used for

Answer 12

1) glycogen store

2) formation of pentose phosphates that can form nucleotides

Question 13

How is NADPH produced and in what pathway is it used

Answer 13

from glucose 6 phosphate and used in the cholesterol pathway ( 3 HMG CoA )

Question 14

What are the uses of acetyl CoA

Answer 14

1) combines with oxaolacetate to form citrate in the krebs cycle
2) combines with another acetyl CoA to form acetoacetyl CoA, which can be used to form ketone bodies ( acetoacetate, acetone, 3 hydroxybutyrate)
3) forms cholesterol by HMG CoA reductase of HMG which is formed from acetoacetyl CoA

Question 15

What happens if glucose concentration falls below a certain amount

Answer 15

If falls below 3mM, enters hypoglycemic coma

Question 16

What are the 4 ways that the body can prevent going into a hypoglycemic coma

Answer 16

1) release of Free fatty acids from adipose tissue
2) making ketone bodies
3) break down of glycogen in the liver
4) gluconeogenesis

Question 17

Describe gluconeogenesis’ bypass reactions

Answer 17

formation of glucose in starving conditions
4 bypass reactions:
pyruvate forms oxaloacetate (enzyme: pyruvate carboxylase)
oxaloacetate forms phosphophenolpyruvate (enzyme: phosphophenolpyruvate carboxykinase)
Fructose 1,6 bisphosphate to fructose 1 phosphate (fructose 1,6 bisphospohatase)
glucose 6 phosphate to glucose (glucose 6 phosphatase)

Question 18

why are bypass reactions required

Answer 18

to make a favourable negative gibbs free energy.

the straight reversal of this process would be +90kj/mol whereas witht the bypass reactions it is -38kj/mol

Question 19

What non carbohydrate molecules can enter gluconeogenesis

Answer 19

1) glycerol forms dihydroxyacetone phosphate
2) amino acids form oxaloacetate (aspartate)
3) amino acids form pyruvate (alanine, serine, and cysteine)
4) lactate forms pyruvate

Question 20

Deamination of all 20 amino acids lead to which products

Answer 20

1) acetyl CoA
2) Acetoacetyl CoA
3) fumerate
4) succinyl CoA
5) Alpha keto glutarate
6) oxaloacetate
7) pyruvate

Question 21

Describe the metabolic processes that occur during exercise (aerobic)

Answer 21

1) contractions mean increased demand for ATP
2) contractions increase glucose transport
3) muscle glycolysis increases
4) gluconeogenesis in liver
5) fatty acids increase
3,4,5 happen as a result of adrenalin

Question 22

Describe the metabolic processes that occur during exercise (anerobic)

Answer 22

1) muscle contractions increase demand for ATP
2) Muscle produces lactate
3) Lactate is transported to the liver, where it is converted to pyruvate and used in gluconeogenesis
4) glycogen is broken down in the muscles to glucose

Question 23

outline the differences between hexokinase in the liver and the blood

Answer 23

The muscles have hexokinase 1 whereas the liver has hexokinase 4
hexokinase 1 has a lower Km and so has a greater affinity to glucose
hexokinase 1 can be more readily inhibited by glucose 6 phosphate
In anerobic conditions hexokinase 1 is inhibited

Question 24

What does adrenalin do

Answer 24

strong and fast metabolic effects

to mobilise glucose for ‘fight or flight’

Question 25

what do glucocorticoids do

Answer 25

steroid hormones that increase synthesis of of metabolic enzymes concerned with glucose availability

Question 26

What does insulin do

Answer 26

secreted in high blood glucose levels
stimulates uptake of glucose by cells and
storage as glycogen and fat

Question 27

What does glucagon do

Answer 27

production of glucose by gluconeogenesis

breakdown of glycogen and fat

Question 28

What happens on having a meal

Answer 28

1) blood glucose levels rise
2) insulin secreted
3) triglycerides synthesized in adipose tissue
4) uptake of glucose by muscle cells
5) uptake of glucose by liver to be stored as glycogen or to undergo glycolysis (as acetyl CoA can be used to make fatty acids)

Question 29

What happens after prolonged fasting

Answer 29

1) glucagon: insulin ratio increases
2) adipose tissue breaks down triglycerides to fatty acid and glycerol (used to form DHAP in glycolysis )
3) break down of proteins to substrates used in the TCA cycle
4) formation of ketone bodies to use as energy source for brain

Question 30

What are the 2 types of diabetes

Answer 30

1) Type 1 DM - inability to secrete insulin

2) type 2 DM - insensitive to insulin

Question 31

What are 4 complications of diabetes

Answer 31

1) hyperglycemia ( increased glucagon levels relative to insulin so more glucose in blood )
2) hypoglycemia ( if injects too much insulin )
3) ketoacidosis ( if makes too many ketone bodies in ‘starvation conditions’ )
4) increased levels of fatty acids + lipoproteins means cardiovascular implications