U3L2: Glycolysis, Pyruvate Oxidation & Krebs cycle

Question 1

What is aerobic cellular respiration?

Answer 1

A process that uses oxygen to get energy from organic compounds —> catabolic pathways that break down energy-rich compounds to create ATP
(C6H12O6 + 6O2 –> 6H2O + 6CO2 + Energy)

Question 2

What are obligate aerobes?

Answer 2

Organisms that need oxygen to survive.

Question 3

What are Facultative aerobes?

Answer 3

use O2, but also have anaerobic methods to produce energy.

Question 4

What are Obligate anaerobes?

Answer 4

Organisms that cannot survive in oxygen

Question 5

What are Facultative anaerobes?

Answer 5

An organism that can live with or w/o oxygen

Question 6

How many stages in AR? What are they called?

Answer 6

4 stages:
1) Glycolysis
2) pyruvate oxidation
3) citric acid cycle (krebs)
4) electron transport chain

Question 7

What two ways can be used to create ATP in AR?

Answer 7

1) Substrate-level phosphorylation
2) Oxidative-phosphorylation

Question 8

What is Substrate-level phosphorylation ?

Answer 8

Forms ATP directly in an enzyme-catalyzed rxn through the transfer of a phosphate group from one molecule to a ADP molecule –> occurs in glycolysis and krebs cycle

Question 9

What is Oxidative-phosphorylation?

Answer 9

Forms ATP indirectly through a series of redox rxns involving a final electron acceptor (NADH or FADH2) —> occurs in ETC

Question 10

Where does glycolysis occur and how many phases does it have

Answer 10

In the cytoplasm, has 2 phases —> the initial energy investment phase and energy payoff phase.

Question 11

Explain what happens during glycolysis (no O2 involved –> j movement of hydrogen)

Answer 11

1) Glucose gets phosphorylated (receives phosphate group to form Glucose-6-Phosphate)
2) rxns 2 - 9 occur
3) Enzymes break down the glucose molecules w/6 carbons to produce 2 molecules of 3 carbon pyruvate.
END OF GLYCOLYSIS: left w/ 2 molecules of ATP (produced using substrate-lvl phosphorylation), 2 molecules of NADH+, and 2 molecules of pyruvate (less PE then PE in glucose molecule since some glucose is oxidized).

Question 12

What is the end net eqn after glycolysis?

Answer 12

Glucose + 2 ADP + 2 Pi + 2 NAD+ -🡪 2 pyruvate + 2 ATP + 2 NADH + 2 H+

Question 13

Where does pyruvate oxidation occur?

Answer 13

The mitochondrial matrix

Question 14

Explain what happens during pyruvate oxidation (if there is O2 —> aerobic respiration)

Answer 14

1) A carboxyl group is ripped off of pyruvate and released as a molecule of carbon dioxide, leaving behind a two-carbon molecule.
2) The two-carbon molecule is oxidized, and the electrons lost in the oxidation are picked up by NAD to form NADH.
3) The oxidized two-carbon molecule—an acetyl group—is attached to Coenzyme A (CoA) to form acetyl CoA.
FINAL RESULT:
Produced 2 molecules of NADH (from the oxidation of acetyl), 2 Acetyl-CoA (from the OG 2 molecules of pyruvate), 2 CO2 molecules (from the carboxyl grp on the pyruvate), 2 hydrogens and synthesizes FADH2. Uses substrate lvl phosphorylation.

Question 15

What is the end net eqn after pyruvate oxidation?

Answer 15

2 pyruvate + 2 NAD+ + 2CoA 🡪 2 acetyl-CoA + 2 NADH + 2H+ + 2CO2

Question 16

Where does the citric acid cycle occur?

Answer 16

Mitochondrial matrix + inner mitochondrial membrane

Question 17

What happens during the citric acid cycle?

Answer 17

1) Acetyl-CoA continues in the mitochondrial matrix and is oxidized to CO2.
2) during step 3, a molecule of carbon dioxide is released and NAD+ is reduced to NADH+.
3) During step 4, a molecule of carbon dioxide is released and NAD+ is reduced to NADH+.
4) in step 5, one molecule of ATP is produced using substrate lvl phosphorylation.
5) in step 6, FAD is reduced to produce FADH2
6) in step 8, another molecule of NAD is reduced to NADH.
CYCLE REPEAT TWICE
FINAL RESULT: 2ATP, 6NADH, 2FADH2, 4CO2 (by-product)

Question 18

So, what is everything produced after glycolysis, pyruvate oxidation and the citric cycle?

Answer 18

4 ATP (2 from glycolysis, 2 from TCA)
10 NADH molecules (2 from glycolysis, 2 from pyruvate oxidation, 6 from TCA)
2 FADH2 molecules (from TCA)

Question 19

How does Anaerobic Respiration work?
(Catabolic)

Answer 19

Similar to aerobic respiration in using electron transferring steps, but it uses inorganic molecules other then oxygen as the final oxidizing agent. The overall process produces less ATP than aerobic respiration and waste prdts build up in the extracellular space.

Question 20

How does fermentation work? (catabolic)

Answer 20

Does not use an electron transport system, it relies on an organic comp to act as the final oxidizing agent to create ATP.
(C6H12O6—-> 2 CH3CH2OH + 2 CO2)

Question 21

Explain Lactic acid fermentation

Answer 21

In lactic acid fermentation,
NADH transfers its electrons directly to pyruvate, generating lactate as a byproduct (in muscle cells and bacteria to make yogurt). This regenerates or “recycles” NAD+ so that glycolysis can continue. Glycolysis produces ATP.

Question 22

Explain Alcoholic fermentation

Answer 22

1) a carboxyl group is removed from pyruvate and released in as carbon dioxide, producing a two-carbon molecule called acetaldehyde.
2) In the second step,
NADH passes its electrons to acetaldehyde, regenerating
NAD and forming ethanol.
*** Happens twice so end prdt is 2 ethanol molecules **
(Pyruvate —-> CO2 + acetaldehyde —> ethanol + NAD)