Fuel in early/late starvation

Question 1

General strategy of Glucose (3Gs)

Answer 1

• glucose conversation
• glucose recycling
• glucose formation

Question 2

In the first few hours of starvation what occurs?

Answer 2

So body utilises glucose (BG goes down) however to prevent hypoglycaemia.

Glycogen –> glucose (liver)

Question 3

What is G6Pase

Answer 3

only in liver
traps P in cell
breaks down glycogen

Question 4

The steps of phosphorylase activation by glucose

Answer 4

• Alpha cells will secrete glycogen which will bind to receptor and cause the formation of CAMP (from ATP)
• this stimulates the protein kinase
• Protein Kinase A is an enzyme which is in the phosphorylase cascade (phosphorylate each other and become active)
• then break down glycogen

Question 5

is the amount of ATP being used a big deal

Answer 5

no as the ATP being used for the cAMP is very tiny and doesn’t affect [ATP]

Question 6

does muscle contribute

Answer 6

does not breakdown glycogen much in starvation

does not have G6Pase thus can’t convert G6P into glucose

Question 7

White Adipose Tissue Lipolysis

Answer 7

glucagon –> inc. cAMP –> activity of PKA –> Hormone Sensitive lipase (HLS- activated) as well as perlipin (allows the activated HSL to interact with fat) –> lots of fatty acids released into bloodstream

Question 8

what happens fatty acids released out

Answer 8

a glycerol and 3 fatty acids

Question 9

what happens to pyruvate if not oxidised to acetyl CoA

Answer 9

converted into lactate by LDH –> then be taken up by liver and remade into glucose by glucogenesis (recycling)

Question 10

Cori-cycle

Answer 10

o Muscle glucose  pyruvate  lactate  liver  glucose (via gluconeogenesis)  glucose to the blood again

Question 11

later starvation - glucose

Answer 11

glycerol (from lipolysis) is the only source of formation of glucose

Question 12

what happens when insulin drops

Answer 12

protein breakdown (esp in muscles)
AA in circulation, C backbones can be made into glucose, can be done by going into liver

Question 13

processign AA

Answer 13

keto-acids used to form glucose

Amine groups on AA are toxic, thus needs to be removed in a particular manner

Question 14

Fate of NH2

Answer 14

AA –> Amine group + glutamate. Those AA get fixed by an enzyme named carbomoly phosphate
The fixed AA is released - lots of energy

Question 15

three rate limiting steps bypassed

Answer 15

• hexokinase (glucose trap)
• phosphofructokinase (limit step)
• pyruvate kinase (final and energy releasing step)

Question 16

substrates involved in gluconeogenesis

Answer 16

• lactate
• glycerol
• AA carbon skeletons

Question 17

AA skeletons pathways

Answer 17

some AA backbone can be made into glucose, while some can’t as they are made into acetyl CoA

Question 18

Acetyoacetyl

Answer 18

• easily soluble

- can get into any tissue mitochondria and then produce fuel via krebs cycle

Question 19

fate of acetoacetate

Answer 19

interconversion to B-hydroxybutryate - both taken into tissues

then split in mitochondria to acetly-CoA (instant source of fuel and Acetyl-CoA inhibits PDH)

Question 20

disadvantages of ketones

Answer 20

• can be lost in urine
• spontaneously decarboxylate to form acetone (sweat and exhale it) All 4 carbon atoms are lost for fuel oxidation thus can’t be used to generate ATP
• unstable

Question 21

pathway of nitrogen

• balance
• cycle

Answer 21

nitrogen is to be balanced

most of nitrogen which cycled and broken down will go out as urea