Fermentation and Krebs Cycle Lecture 24 BIO !!!

When do pyruvate undergo fermentation?

In the absence of oxygen

What is Alcoholic Fermentation?

Carried out by organisms such as yeast, converts glucose into Ethanol, Carbon Dioxide, and NAD+

What is Lactic Acid Fermentation?

Occurs in muscle cells when experiencing an oxygen deficit to continue to produce energy.

Results in Lactate and NAD+

Can also be used by bacteria as a way to produce energy.

What is the preliminary step of respiration?

Pyruvate oxidation

Where does Pyruvate move from?

from the cytoplasm where it was produced, across the outer and inner membranes of the mitochondrion into the mitochondrial matrix.

What is Pyruvate oxidized to?

Acetyl-CoA

Where does the krebs cycle take place?

Mitochondrial matrix of eukaryotic cells and in the cytoplasm of prokaryotic cells.

What happens in Krebs cycle step 1?

Acetyl-CoA joins with a four-carbon molecule, oxaloacetate, releasing the CoA group and forming a six-carbon molecule called citrate.

What happens in Krebs cycle step 2?

Citrate is converted into its isomer, isocitrate.

Two-step process, involving the removal and then the addition of a water molecule.

What happens in Krebs cycle step 3?

Isocitrate is oxidized and releases a molecule of carbon dioxide, leaving behind a five-carbon molecule, 𝛼-ketoglutarate.

During this step, NAD+ is reduced to form NADH.

The enzyme catalyzing this step, isocitrate dehydrogenase, is important in regulating the speed of the Krebs cycle.

What happens in Krebs cycle step 4?

𝛼-ketoglutarate is oxidized, reducing NAD+ to NADH and releasing a molecule of carbon dioxide in the process.

The remaining four-carbon molecule picks up Coenzyme A, forming the unstable compound succinyl-CoA.

What happens in Krebs cycle step 5?

The CoA of succinyl-CoA is replaced by a phosphate group, which is then transferred to ADP to make ATP.

What is the four-carbon molecule produced in the Krebs cycle step 5 called?

Succinate

What happens in Krebs cycle step 6?

Succinate is oxidized, forming another four-carbon molecule called fumarate.

In this reaction, two hydrogen atoms with their electrons are transferred to FAD, producing FADH2.

Why is the enzyme that carries out step 6 of the Krebs cycle embedded in the inner membrane of the mitochondrion?

So that FADH2 can transfer its electron directly into the electron transport chain.

What happens in Krebs cycle step 7?

Water is added to the four-carbon molecule fumarate, converting it into another four-carbon molecule called malate.

What happens in Krebs cycle step 8?

Oxaloacetate, the starting four-carbon compound, is regenerated by oxidation of malate.

Another molecule of NAD+ is reduced to NADH in the process

What is produced in one turn of the Krebs cycle?

Releases 2 CO2

Produces: 3 NADH, 1 FADH2 and 1 ATP

How many cycles of the Krebs cycle for each molecule of glucose?

Twice for each molecule of glucose that enters cellular respiration because there are two pyruvates thus, two acetyl CoAs made per glucose.

What is overall result of Acetyl-CoA formation and the Krebs cycle?

6 CO2 (2 from pyruvate oxidation, 4 from Krebs cycle)

2 ATP

8 NADH+ H+ (2 from pyruvate oxidation, 6 from Krebs cycle)

2 FADH2

The Krebs cycle produces a lot of ATP indirectly by?

The NADH and FADH2 it generates which later drives the synthesis of ATP molecules through oxidative phosphorylation in the ETC.