Metabolic Biochem 1,2

Question 1

Enzyme types

Answer 1

Aminotransferase- transfer amino acids
Dehydrogenase- removes hydrogen, electron carrier
Isomerase- convert one isomer to another
Kinase- transfer phosphate from one group to another
Lipase- breaks down lipid
Mutase- transfer phosphate to a different c in same substrate
Phosphorylase- adds phosphate from free
Reductase- electron transfer without hydrogen

Question 2

Key intermediates- glucose-6-phosphate

Answer 2

Has 4 major gates

• convert to fructose-6-phosphate
• convert to glucose
• convert to/ from glycogen
• pentose phosphate pathway (building block for RNA)- also make NADP form fag

Question 3

Key intermediates- pyruvate

Answer 3

Has 5 major fates:

• lactate
• alanine
• enter mitochondrial membrane to form Acetyl coA
• mitochondrial membrane to form oxaloacetate
• ethanol

Question 4

Key intermediates- Acetyl CoA

Answer 4

Has 6 major fates:

• in mitochondrial matrix
• citrate
• ketone bodies
• fatty acids
• ketogenic AAs
• citrate exit mitochondria - Acetyl coA- FAs or cholesterol

Question 5

Key intermediates- oxaloacetate

Answer 5

4 major functions

• citrate in m.m to produce malate, pyruvate then produced PEP
• can produce ASP
• can produce a Malays

Question 6

Compartmentalisation: Cystolic pathways and key intermediates

Answer 6

- cytosol 
Glucogenesis
Glucogenolysis 
Glycolysis 
Gluconeogenesis
Lactate alanine etc 
- mitochondria
ETC 
Urea cycle - 1/2 cytosol 
TCA cycle

Question 7

Metabolism of a sprinter

Answer 7

100m
Approx 10 secs
Total ATP used: 1.5mol
Metabolic fuels used: muscle ATP, creatine phosphate and muscle glycogen
Average velocity of ATP production: 39-73mmol/sec
Major pathways for energy production: glycogenolysis anaerobic glycolysis
Major metabolic products: increased lactate and decreased blood pH

Question 8

Metabolism of a marathon runner

Answer 8

42.2km
2-21/2 hours
Total ATP required: 150mol
Major metabolic fuels used: glycogen and fatty acids
Average velocity of ATP production: 6.2-16.7 mmol/sec
Major pathways of energy production: glycogenolysis and fatty acid oxidation
Major metabolic products: CO2, H2O and heat

Question 9

Metabolism of an ironman triathlete

Answer 9

226.3km
8-10 hours
Total ATP required: 600-800mol
Major metabolic fuels used: glycogen, fatty acids, ketone bodies, amino acids - can deplete up to 25% of muscle protein during an ironman event
Average velocity of ATP production: 6-10mmol/ sec
Major pathways for energy production: glycogenolysis and FA, KB, and AA oxidation
Major metabolic products: CO2, H2O and heat

Question 10

Allosteric regulation

Answer 10

Of or involving a change in he shape and activity of an enzyme that results from the binding of a regulatory molecule at a site other than the active site

Question 11

Allosteric regulation in glycolysis- hexokinase

Answer 11

Km (glucose)= 0.1mM
Hexokinase inhibited by own product- to ensure it maintains same level of blood sugar
Glucokinase is not regulatory enzyme, it is regulated by direct blood glucose levels (meals)

Question 12

Allosteric regulation in glycolysis- phsophofructokinase

Answer 12

Activates AMP2, ADP3, F-2-6-bisP to active to increase ATP
Inhibits- ATP, Invreased H+, cottage to stop energy production, also don’t want cells to become acidic. High citrate in cells indicates efficient glucose in cell.
Bind to allosteric site which makes cell relaxed when not bound- tense.
Low ATP - higher binding affinity
Sigmoidality- allosteric regulation
To the right- allosteric regulation

Question 13

Allosteric regulation in glycolysis - pyruvate kinase

Answer 13

Liver -LPK- muscle- MPK
Activates F-1-6-bisP- upstream product, returns and activates
Inhibits ATP5, alanine. ATP product of late reaction, prevents too much ATP

Question 14

Tissue Specificity - brain

Answer 14

Brain: fuel source- glucose- brain can adapt to ketone bodies during starvation (>3 days) and danger occurs when glucose <2.2mM. Does not store, relies on constant supply of blood glucose via GLUT3 Km- 1.0mM.
In resting conditions- brain consumes 60% of total glucose- 120g/day (1.76MJ) in resting state.

Question 15

Tissue specificity - adipose and liver

Answer 15

Adipose
Fuel sources: required glucose to perform major task of synthesising and storing triacylglycerol, which is mobilised during fasting.
Fuel stores: in a 70kg person, adipose stores >80% of total available energy
Resting conditions: Highly active during starvation (decreased insultin activates hormone sensitive lipase which breaks down TAH)

Question 16

Tissue specificity- skeletal muscle

Answer 16

Skeletal muscle:
Fuel source- glucose, FA, KB
Fuel stores- muscle stores 75% of glycogen and can represent 1% of muscle weight after a meal.
Resting conditions- muscle utilised FAs as the major fuel in the resting state but uses glucose during exercise. Heart muscle also uses FAs, but oxidised KBs (primarily acetoacetate) in preference to glucose muscle and liver metabolites connected by cori and Ala cycles

Question 17

Tissue specificity- liver

Answer 17

Liver
Fuel sources: can utilise glucose, fatty acids, ketone bodies and amino acids. But prefers alpha keto acids derived from the degradation of amino acids in preference to glucose
Fuel stores- liver stores 1/4 of total body glycogen. Uses lactate and alanine from muscle, glycerol from adipose and glucogenic amino acids from diet to make approx 200g of glucose per day via gluconeogenesis
Resting conditions- highly active during starvation making glucose via GNG to maintain blood glucose primarily for the brain, RBCs and retina. Also oxidises FAs for energy and formation of KBs for the brain, heart muscle and other tissues.
Other functions- synthesises TAGs, PLs and cholesterol and secretes VLDL for lipoprotein transport and synthesises heme.