Week 7 - CHO & Indirect Calorimetry

Question 1

Storage of CHO

Answer 1

Blood glucose — Normal conc. 3-5mmol/L (euglycemia)

Liver glycogen — Approx 100g.

Muscle glycogen — 400-500g.

Question 2

What are blood glucose levels regulated by?

Answer 2

Hormones + a primary cerebral fuel.

Question 3

Define glycogenesis

Answer 3

Formation of glycogen from sugar mol.

Question 4

Define gluconeogenesis

Answer 4

Formation of glycogen from aa, fats + other non-CHO

Question 5

Define glycogenolysis

Answer 5

Breakdown of glycogen into glucose to use for energy transfer

Question 6

What enzyme catalyses the breakdown of glycogen

Answer 6

Glycogen phosphorylase

Question 7

What are the 3 stages in which energy is extracted from CHO

Answer 7

Glycolysis

TCA/Krebs cycle

Oxidative phosphorylation/ETC

Question 8

Glycolysis

Answer 8

Oxidation of glucose/glycogen.

In cytoplasm

Produces lactate or pyruvate

Question 9

General formula for CHO

Answer 9

Cn(H20)n

Question 10

What is the primary regulator for the speed of glycolysis

Answer 10

Phosphofructokinase

Question 11

Glycolysis

Step 1

Answer 11

Glucose + ATP – hexokinase –> Glucose-6-phosphate + ADP

Question 12

Glycolysis

Step 2

Answer 12

Glucose-6-phosphate – phosphoglucose isomerase –> fructose-6-phosphate

Question 13

Glycolysis

Step 3

Answer 13

Fructose-6-phosphate + ATP – (PFK) –> fructose 1,6-biphosphate + ADP

Question 14

Glycolysis

Step 4

Answer 14

Fructose 1,6-biphosphate – aldolase –> dihydroxyacetone phosphate + glyceraldehyde 3-phosphate

Question 15

Glycolysis

Step 5

Answer 15

Dihydroxyacetone P – triose P isomerase –> glyceraldehyde 3-P

Question 16

Glycolysis

Step 6

Answer 16

Glyceraldehyde 3-phosphate + NAD+ + Pi — glyceraldehyde 3-phosphate dehydrogenase –> 1,3-biphosphoglycerate + NADH + H+

Question 17

Glycolysis

Step 7

Answer 17

1,3 biphosphoglycerate + ADP – phosphoglycerate kinase – > 3-phosphoglycerate + ATP

Question 18

Which is the stage where ATP is first generated in glycolysis

Answer 18

Step 7

1,3 biphosphoglycerate + ADP – phosphoglycerate kinase – > 3-phosphoglycerate + ATP

Question 19

What might slow the rate of glycolysis in step 6?

Answer 19

‘Bottleneck’

If metabolic rate is very high, NAD+ can become saturated w/ H+, so that there’s not enough free NAD+ available.

Question 20

Glycolysis

Step 8

Answer 20

3-phosphoglycerate – phosphoglycerate mutase –> 2-phosphoglycerate

Question 21

Glycolysis

Step 9

Answer 21

2-phosphoglycerate – enolase –> phosphoenylpyruvate + H20

Question 22

Glycolysis

Step 10

Answer 22

Phosphoenylpryuvate + ADP + H+ – pyruvate kinase –> pyruvate + ATP

Question 23

What is the step that generates the 2nd ATP?

Answer 23

Step 10

Phosphoenylpryuvate + ADP + H+ – pyruvate kinase –> pyruvate + ATP

Question 24

What are the rate limiting steps in glycolysis

Answer 24

PFK in step 3

NAD+ in step 6

Question 25

Which are the ATP generating steps in glycolysis

Answer 25

7 + 10

Question 26

What is the principle of bomb calorimetry

Answer 26

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.

Question 27

Steps to bomb calorimetry

Answer 27

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.

Question 28

How often should you record temp in bomb calorimetry

Answer 28

Every 30secs

Question 29

What is indirect calorimetry

Answer 29

When GE measurements are used to estimate the type + rate of substrate utilisation + energy metabolism.

Question 30

What is the role of NAD/NADH in the lead up to the TCA/Krebs/Cyclic cycle

Answer 30

To convert pyruvate (from step 10 of glycolysis) to lactate or Coenzyme A

Question 31

Pyruvate --> lactate in lead up to Krebs cycle Which enzyme + what's the result

Answer 31

LACTATE DEHYDROGENASE NADH becomes NAD+ NAD+ travels to step 6 glycolysis

Question 32

Pyruvate --> acetyl CoA Enzyme? Result?

Answer 32

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

Question 33

Why produce lactate? What levels are NADH + NAD+ at a high metabolic rate?

Answer 33

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.

Question 34

When is pyruvate converted to Acetyl-CoA?

Answer 34

When metabolic rate is low + there’s LOTS of O2 + NAD+.

Question 35

Cytosol

Answer 35

Part of the mitochondria where glycolysis occurs

Question 36

Properties of co-enzymes

Answer 36

Less specific than enzymes Act as co-binders Temporary carriers Reversible e- + H+ acceptors i.e NAD+ & FAD

Question 37

How many steps are there in the TCA cycle

Answer 37

8

Question 38

What is the main purpose of the TCA cycle

Answer 38

Oxidise acetyl groups + strip off their e-.

Question 39

GTP

Answer 39

Guanosine triphosphate Quickly converted to ATP by transferring the 3 P groups into adenosine sugar instead of guanosine.

Question 40

What is the energy transfer of the TCA cycle from 1 glucose mol.

Answer 40

6 NADH 2 FADH(2) 2 GTP 32 H

Question 41

List the TCA cycle intermediaries

Answer 41

Citrate Isocitrate alpha-ketoglutarate Succinyl-CoA Succinate Fumarate Malate Oxaloacetate

Question 42

What are the key steps in the TCA cycle

Answer 42

1. Oxaloacetate + Acetyl Co-A --> 6-C mol = citrate. 3+4. CO2 + NADH + H+ produced. 5. 1 GTP prod. 6. FADH(2) prod. 8. NADH prod + oxaloacetate regenerated.