6. ATP yield

Question 1

GE of glucose = (kj) ?

Answer 1

2816

Question 2

Formation of ATP by substrate-level phosphorylation: direct. How is this performed? What enzyme is responsible for this?

Answer 2

For example: Glycolysis

• Phosphate is added to ADP > ATP
• Molecule of conversion now has one phosphate less
• Enzyme able to perform direct substrate phosphorylation = kinase

Question 3

Indirect formation of ATP: oxidation
Three ways this can happen?

Answer 3

1. Reaction with oxygen
2. Withdrawal of electrons
3. Dehydrogenation (reducing & oxidizing: NAD
   -> NADH)

Question 4

For everything that becomes oxidated, something else becomes reduced.
Oxidation = ?
Reduction = ?

Answer 4

Oxidation = loss of electrons
Reduction = gain of electrons

An oxidizing agent is a substance that causes oxidation by accepting electrons; therefore, it gets reduced. A reducing agent is a substance that causes reduction by losing electrons; therefore it gets oxidized.

Question 5

Inner vs outer membrane mitochondria in terms of permeability?

Answer 5

Outer membrane mitochondria: partially permeable
Inner membrane: very impermeable

Question 6

What compartmentalizes mitochondria?

Answer 6

• Cristae and matrix compartmentalize mitochondrion space

Question 7

How is oxidative phosphorylation performed?

Answer 7

1. Nutrients provide high energy electrons in the form of NADH
2. NADH = used by membrane protein complexes to pump protons from matrix to intermembrane space
3. Proton gradient to matrix
4. When they re-enter matrix through ATP synthase, ATP is catabolized.

O2 is the terminal electron aceptor: protons carry through the membrane when they meet oxygen. Water is made.

Question 8

Oxidative phosphorylation:
Takes place where? What does it regenerate?

Answer 8

Cristae in mitochondria. Proteins located in the inner mitochondrial membrane.
Regenerates NADH and FADH by oxidation and phosphorylation of ADP > ATP

Question 9

Why is NADHc that has to enter mitochondria worth less ATP?

Answer 9

Takes some ATP to let NADH enter mitochondria. Is now worth 1.5 ATP.

Question 10

Energy transfer by oxidation: who is the acceptor and who is the donor?

Answer 10

Substrate: electron or H-donor
Oxygen: electron or H-acceptor

Question 11

What is respirometry?

Answer 11

measuring oxygen consumption and thereby mitochondrial activity.

Question 12

How is ROS formed during oxidative phosphorylation?

Answer 12

Electrons are very unstable. Sometimes, during oxidative phosphorylation, electrons can escape the respiratory chain/proteins to yield O2. Results in ROS. One radical every 25 molecules O2 reduced

Question 13

Uncoupling proteins: what do they do?

Answer 13

They make sure there is no ATP synthesized by interfering in the ox. phosph.

E.g. DiNitroPhenol: binds to membrane and takes up H+ meant for the ATP synthase. Releases it back to the mitochondrial matrix. Very toxic, for heat production instead of energy storage (losing weight)

Question 14

Are uncoupling proteins naturally present in the body? If so, where?

Answer 14

 Brown adipose tissue
 Muscle and other tissues

Important to keep your temperature stable. Heat production to maintain body temperature: non-shivering thermogenesis. Also important in body weight regulation.

Question 15

The glycerophophate shuttle: what does it do? How much ATP?

Answer 15

Transport of reducing equivalents (NADH) from cytoplasm into the mitochondrion by the glycerophosphate shuttle

This ‘shuttle’ has a specific transporter on the membrane. When NADH in the cytosol needs to enter the mitochondrial matrix, you will always lose 1 ATP (2.5 – 1 = 1.5 ATP). This happens because it is converted to FADH2.

Question 16

So, what may the mitochondrial electron transport chain produce?

Answer 16

• ROS
• ATP from ATP
• Heat
• (water)

Question 17

isolated mitochondria are incubated with 10 mol (cytoplasmic) NADH. How many mol of ATP will be formed?

Answer 17

1.5 x 10 = 15 mol ATP

1 mol NADHc = 1.5 ATP

Question 18

What If you use a homogenate of mitochondria

Answer 18

homogenate = crushed mito’s, so not intact. Nothing happens.

Question 19

What main event happens in the case of uncoupling of oxidative phosphorylation?

Answer 19

No ATP formed

Question 20

Krebs cycle: What is needed? Where is it located? Common pathway of what?

Answer 20

Acetyl-CoA: needed for the cycle. Can come from protein, glucose, fat. Will produce 2 CO2 and a lot of H+ carriers. Krebs cycle is fully in the matrix of the mitochondria.
> is the common pathway to oxidize carbohydrates, fat and protein
> Acetyl-CoA is the ONLY substrate (activated acetic acid)
> Carbohydrates, fat and protein have first to be converted to acetyl-CoA.

Question 21

At the krebs cycle, one … and four … reactions are happening

Answer 21

Four oxidation reactions
one substrate-level phosphorylation.

Question 22

Krebs cycle in terms of C-carbons?

Answer 22

4C OAA + 2C acetyl-CoA -> 6 Citrate

4C oxaloacetate
+ 2C Acetyl-CoA
6C Citrate
6C isocitrate
5C ketoglutarate
4C succinyl-CoA
4C succinate
4C fumarate
4C malate
4C oxaloacetate

Question 23

What is step 1 of the Krebs cycle? (You can use metabolic map). Energy ?

Answer 23

1. Condensation of acetyl CoA and oxaloacetate -> citrate (no energy requested/produced)

Question 24

What is step 2 of the Krebs cycle? (You can use metabolic map). Energy ?

Answer 24

2. Citrate converted into cis-aconitate into isocitrate (no energy requested/produced)

Question 25

What is step 3 of the Krebs cycle? (You can use metabolic map). Energy ?

Answer 25

3. First oxidation happening: decarboxylation (-CO2) and oxidation -> ketoglutarate. 2.5 ATP and one carbon released.

Question 26

What is step 4 of the Krebs cycle? (You can use metabolic map). Energy ?

Answer 26

4. Another oxidation: decarboxylation and oxidation -> succinyl CoA. 1 NADH and CO2 formed.

Question 27

What is step 5 of the Krebs cycle? (You can use metabolic map). Energy ?

Answer 27

5. Substrate-level phosphorylation. Production of GTP by succinyl CoA synthetase. (So, +1ATP)

All reactions in krebs cycle are reversible.

Question 28

What is step 6 of the Krebs cycle? (You can use metabolic map). Energy ?

Answer 28

6. Dehydrogenation -> carbon-carbon double bond. FADH formed, 1.5 ATP.

Question 29

What is step 7 of the Krebs cycle? (You can use metabolic map). Energy ?

Answer 29

7. Addition of water across the carbon-carbon double bond. No energy needed or produced. Malate formed.

Question 30

What is step 8 (final) of the Krebs cycle? (You can use metabolic map). Energy ?

Answer 30

8. Oxidation to reform oxaloacetate. Energy produced in the form of NADH.

Question 31

How much ATP is produced for each Acetyl-CoA entering the krebs cycle?

Answer 31

For every acetyl-CoA entering the cycle, 10 ATP is produced.

Question 32

What is the rate limiting enzyme of TCA cycle?

Answer 32

Citrate synthase. This enzyme converts OAA -> citrate.

Question 33

How is citrate synthase regulated?

Answer 33

Inhibited by high ratio’s of
ATP over ADP
Acetly-CoA over CoA
NADH over NAD+

And by high frquency of citrate and succinyl-CoA

Question 34

For each glucose, you will get … ATP from the krebs cycle, because ..

Answer 34

For each glucose, you will get 20 ATP from the cycle. Gluc = 6C -> 2x pyruvate = 3C, lose one C each. = 2x acetyl-CoA

Question 35

How can fat burn in the presence of carbohydrate?

Answer 35

> Lot of Acetyl-CoA from fat
Also need lot of oxaloacetate = made from pyruvate, originating from the glycolysis.

Only when a lot of acetyl-CoA is coming and the OAA pool needs to be refuelled

Question 36

When is the carbon of acetyl-CoA released in tje krebs cycle?

Answer 36

not released in the first cycle, but in the next.