Week 7 - CHO & Indirect Calorimetry Flashcards
Storage of CHO
Blood glucose — Normal conc. 3-5mmol/L (euglycemia)
Liver glycogen — Approx 100g.
Muscle glycogen — 400-500g.
What are blood glucose levels regulated by?
Hormones + a primary cerebral fuel.
Define glycogenesis
Formation of glycogen from sugar mol.
Define gluconeogenesis
Formation of glycogen from aa, fats + other non-CHO
Define glycogenolysis
Breakdown of glycogen into glucose to use for energy transfer
What enzyme catalyses the breakdown of glycogen
Glycogen phosphorylase
What are the 3 stages in which energy is extracted from CHO
Glycolysis
TCA/Krebs cycle
Oxidative phosphorylation/ETC
Glycolysis
Oxidation of glucose/glycogen.
In cytoplasm
Produces lactate or pyruvate
General formula for CHO
Cn(H20)n
What is the primary regulator for the speed of glycolysis
Phosphofructokinase
Glycolysis
Step 1
Glucose + ATP – hexokinase –> Glucose-6-phosphate + ADP
Glycolysis
Step 2
Glucose-6-phosphate – phosphoglucose isomerase –> fructose-6-phosphate
Glycolysis
Step 3
Fructose-6-phosphate + ATP – (PFK) –> fructose 1,6-biphosphate + ADP
Glycolysis
Step 4
Fructose 1,6-biphosphate – aldolase –> dihydroxyacetone phosphate + glyceraldehyde 3-phosphate
Glycolysis
Step 5
Dihydroxyacetone P – triose P isomerase –> glyceraldehyde 3-P
Glycolysis
Step 6
Glyceraldehyde 3-phosphate + NAD+ + Pi — glyceraldehyde 3-phosphate dehydrogenase –> 1,3-biphosphoglycerate + NADH + H+
Glycolysis
Step 7
1,3 biphosphoglycerate + ADP – phosphoglycerate kinase – > 3-phosphoglycerate + ATP
Which is the stage where ATP is first generated in glycolysis
Step 7
1,3 biphosphoglycerate + ADP – phosphoglycerate kinase – > 3-phosphoglycerate + ATP
What might slow the rate of glycolysis in step 6?
‘Bottleneck’
If metabolic rate is very high, NAD+ can become saturated w/ H+, so that there’s not enough free NAD+ available.
Glycolysis
Step 8
3-phosphoglycerate – phosphoglycerate mutase –> 2-phosphoglycerate
Glycolysis
Step 9
2-phosphoglycerate – enolase –> phosphoenylpyruvate + H20
Glycolysis
Step 10
Phosphoenylpryuvate + ADP + H+ – pyruvate kinase –> pyruvate + ATP
What is the step that generates the 2nd ATP?
Step 10
Phosphoenylpryuvate + ADP + H+ – pyruvate kinase –> pyruvate + ATP
What are the rate limiting steps in glycolysis
PFK in step 3
NAD+ in step 6
Which are the ATP generating steps in glycolysis
7 + 10
What is the principle of bomb calorimetry
To burn something in an O2 atmosphere placed inside a bucket of H20 so that temp changes of the H20 due to combustion can be measured.
– Can then determine how much energy was released.
Steps to bomb calorimetry
Step 1 - Weigh sample ( use dextrose tablet )
Step 2 - Place sample in bomb. In a combustion cup sitting on electrodes.
Bomb is fired using fuse wires. — Make sure these touch the sample but NOT the cup.
Step 3 - Pressurise bomb w/ O2. - Aim for 30 atmospheres.
Step 4 - Place H20 in calorimeter after which infra-red will reflect back into H20.
Step 5 - Place H20 bucket on scale + press tare to get 0.
Step 6 - Weigh 2kg of H20.
Step 7 - Put everything together — Calorimeter in insulated bucket.
Step 8 - Leave device for about 5 mins, until steady temp is reached.
How often should you record temp in bomb calorimetry
Every 30secs
What is indirect calorimetry
When GE measurements are used to estimate the type + rate of substrate utilisation + energy metabolism.
What is the role of NAD/NADH in the lead up to the TCA/Krebs/Cyclic cycle
To convert pyruvate (from step 10 of glycolysis) to lactate or Coenzyme A
Pyruvate –> lactate in lead up to Krebs cycle
Which enzyme + what’s the result
LACTATE DEHYDROGENASE
NADH becomes NAD+
NAD+ travels to step 6 glycolysis
Pyruvate –> acetyl CoA
Enzyme?
Result?
DEHYDROGENASE complex of CoA + pyruvate.
NAD+ accepts some H+ from pyruvate to prod. Acetyl-CoA —> NADH + H+
—— NADH is transported to mit. where H+ + e- can be used in the ETC.
Acetyl-CoA enters TCA cycle
Why produce lactate?
What levels are NADH + NAD+ at a high metabolic rate?
Quick fix to keep a high glycolytic rate.
Rate of glycolysis is very fast.
But TCA + ETC are slower.
High metabolic rate = Availability of NADH is high vs. NAD+ is low. — Can be a problems for step 6 of glycolysis. So in order to maintain this step, the metabolic env. In the cell during high level of activity favours pyruvate —> lactate + NAD+ prod will help maintain glycolytic rate.
When is pyruvate converted to Acetyl-CoA?
When metabolic rate is low + there’s LOTS of O2 + NAD+.
Cytosol
Part of the mitochondria where glycolysis occurs
Properties of co-enzymes
Less specific than enzymes
Act as co-binders
Temporary carriers
Reversible e- + H+ acceptors
i.e NAD+ & FAD
How many steps are there in the TCA cycle
8
What is the main purpose of the TCA cycle
Oxidise acetyl groups + strip off their e-.
GTP
Guanosine triphosphate
Quickly converted to ATP by transferring the 3 P groups into adenosine sugar instead of guanosine.
What is the energy transfer of the TCA cycle from 1 glucose mol.
6 NADH
2 FADH(2)
2 GTP
32 H
List the TCA cycle intermediaries
Citrate
Isocitrate
alpha-ketoglutarate
Succinyl-CoA
Succinate
Fumarate
Malate
Oxaloacetate
What are the key steps in the TCA cycle
- Oxaloacetate + Acetyl Co-A –> 6-C mol = citrate.
3+4. CO2 + NADH + H+ produced.
- 1 GTP prod.
- FADH(2) prod.
- NADH prod + oxaloacetate regenerated.
