W4 Cellular energetics/Lec 6

Question 1

What is meant by catabolism?

Answer 1

Breaking down.
Large food molecules are broken down into smaller molecules (monomers)

Question 2

What is meant by anabolism?

Answer 2

Building up.

Question 3

What is cellular respiration?

Answer 3

A process that breaks down sugars and other metabolites to CO2 and water. Converts the energy released from food into the build-up of ATP.

Question 4

What is ATP used in the cell for?

Answer 4

• An energy currency used to drive a variety of chemical reactions in cells (also GTP)
• Hydrolysis of high-energy phosphate bonds release energy to fuel cellular processes/reactions

Question 5

Can ATP be recycled?

Answer 5

ATP can be converted into ADP and recycled back (same for GTP/GDP)
Cells break phosphate bonds of ATP to supply energy

Question 6

What are the most common electron carriers? (coenzymes)

Answer 6

• NAD+ and FAD

Question 7

What do coenzymes do during cellular respiration?
What are they reduced into?
What do they transfer?

Answer 7

They act as oxidising agents and are reduced into NADH and FADH2
Their reduced forms transfer protons and electrons to other molecules and represent stored energy used to synthesise ATP

Question 8

What are the 4 stages of aerobic respiration?

Answer 8

Glycolysis
Link reaction (Pyruvate oxidation to form acetyl-CoA)
Krebs/ Citric acid cycle
Oxidative Phosphorylation

Question 9

Where does Glycolysis occur?

Answer 9

In the cytoplasm

Question 10

Where does the Link reaction, Krebs cycle and Oxidative phosphorylation occur?

Answer 10

In the mitochondrial matrix

Question 11

What happens during Glycolysis?

Answer 11

The “Splitting of Glucose”
Glucose is broken down into 2 molecules of pyruvate
Generating 2 ATP and 2 NADH
Consists of 10 different reactions with 10 enzymes

Question 11

Does Glycolysis require oxygen?

Answer 11

No. It is an anaerobic process

Question 12

What happens to Pyruvate under anaerobic conditions?
What is restored?

Answer 12

Remains in cytosol (in the cytoplasm) and undergoes fermentation (Lactate or Ethanol production)
No energy production occurs but it restores the NAD+ consumed in glycolysis so it can continue

Question 13

What happens to Pyruvate under aerobic conditions

Answer 13

Transported into the mitochondria for aerobic respiration to continue

Question 14

What could also happen to Pyruvate to resynthesise glucose

Answer 14

Gluconeogenesis- An anabolic pathway to synthesise glucose (reverse to glycolysis).
Can occur when glycogen store starts to deplete

Question 15

What happens during lactate fermentation?

Answer 15

Pyruvate is reduced to lactic acid. Occurs in muscle cells (human) when oxygen is not adequate (physical activities)
Lactic acid can build up causing cramps

Question 16

What happens in ethanol fermentation?
What cells does it occur in?
Used to produce what?

Answer 16

Pyruvate is reduced to ethanol & CO2.
Occurs in bacteria and heat cells (NOT HUMAN)
Used to produce alcoholic spirits, bread

Question 17

Mitochondria function

Answer 17

Contains enzymes responsible for ATP production (Krebs cycle, oxidative phosphorylation)

Question 18

What happens during the link reaction (pyruvate oxidation)

Answer 18

Links glycolysis to Krebs cycle
In presence of O2, pyruvate produced by glycolysis is actively pumped into the mitochondrial matrix
Pyruvate converted to a 2 carbon acetyl group (acetate)
Attaches to Coenzyme A to form Acetyl Co-A
Electron picked up by NAD+ to form NADH
CO2 released outside the mitochondria

Question 19

What happens during the Citric Acid (Krebs) Cycle?

Where does it occur?

What is the net gain?

Answer 19

-Occurs in the mitochondrial matrix
-Consists of a cycle 8 reactions.
-Acetyl CoA is added to oxaloacetate (4C) forming citric acid. In each cycle:
- The acetyl group of acetyl CoA is fully oxidised into CO2 and water
- Oxaloacetate is regenerated
- 2 turns for one glucose molecule (1 glucose generates 2 pyruvate/acetyl CoA

Net result: 4 CO2, 2 GTP, 6 NADH, 2 FADH2

Question 20

What are the 2 stages of Oxidative Phosphorylation?

Answer 20

Electron transport chain and Chemiosmosis

Question 21

What happens during Chemiosmosis?

Answer 21

Electrons are pumped from the matrix to the inter membrane space, generating a proton gradient across the inner membrane (chemiosmosis)
ADP is pumped into the matrix and ATP is pumped out by an antiport process

Question 22

What happens during the Electron Transport Chain?

Answer 22

NADH and FADH2 transfer their high-energy electrons to the the electron transport chain.
Passage of electrons through the complex
Electrons drop in free energy as they go through the chain and are passed to O2 that combine with protons forming H2O

Question 23

Which molecule enters the citric acid cycle?

Answer 23

Acetyl CoA

Question 24

What process converts glucose into 2 molecules of pyruvate?

Answer 24

Glycolysis

Question 25

How many ATP molecules are generated in glucose catabolism?

Answer 25

30-32 Net yield