Glycolysis and Pyruvate Metabolism

Flashcards for reviewing Glycolysis II and the fate of Pyruvate

How does an apoenzyme become active?

By the binding of a coenzyme or cofactor to an enzyme

Where does a coenzyme or cofactor bind to on an enzyme?

The enzyme's active site.

Why is the coenzyme bound relatively tightly?

So that the particular group to be transferred is properly orientated to allow catalysis to occur.

Once bound to a chemical group, what happens to the structure of the coenzyme?

It changes

Why do coenzymes need to regenerate?

To participate in the reaction again.

What chemical process occurs in the 2nd step of the 6th step of glycolysis, using glyceraldehyde-3-phosphate dehydrogenase?

Oxidation of the thioether bond to form a thioester bond using NAD+ to perform the oxidation.

What is the role of thioester bond cleavage?

To supply energy to drive the endergonic phosphorylation reaction

What is released from the gylceraldehyde-3-phosphate dehydrogenase enzyme in step 3 of the 6th step of glycolysis

A 1,3-bisphophoglycerate

How can the continual supply of NAD+ be met under aerobic conditions?

By the oxidation of NADH in the electron transfer chain.

What happens to pyruvate under aerobic conditions?

Pyruvate can enter the mitochondria and be consumed in the tricarboxylic acid (TCA) cycle.

What must happen under anaerobic conditions?

The cell must still generate NAD+ from NADH.

What is an example of how NAD+ is generated from NADH under anaerobic conditions.

The conversation of pyruvate to lactate.

Why can't red blood cells use oxygen

Red blood cells lack mitochondria and can only use the lactic acid pathway

How many ATP molecules are produced under anaerobic conditions per glucose that is converted into lactate or alcohol

2

Where do Glycolysis, TCA cycle, ETC, and Fermentation occur in eukaryotic Cells?

Glycolysis and fermentation occur in the cytoplasm while the ETC occurs in the mitochondrial membrane and the TCA cycle occurs in the mitochondrial matrix

Where do Glycolysis, TCA cycle, ETC, and Fermentation occur in prokaryotic Cells?

Glycolysis, the TCA cycle and fermentation occur in the cytoplasm while the ETC occurs in the mitochondrial membrane

What is fermentation?

The production of lactic acid or ethanol under anaerobic conditions

In eukaryotes, where is the pyruvate dehydrogenase located?

The mitochondrial matrix

What are porins?

Proteins that allow small molecules like pyruvate to enter the intermembranous space.

What is the function of the pyruvate transporter (MPC)?

Transports pyruvate across the impermeable inner mitochondrial membrane.

How does a CoA function?

It reacts with carboxylic acids with thioesters, functioning as an acyl group carrier.

When there is excess glucose, how is coenzyme A used?

It is used in the cytosol for synthesis of fatty acids.

Describe a metabolic pathway.

A group of enzymes which are associated with others in a particular pathway to form multi-enzyme complexes.

Describe step 1 of the link reaction.

A carboxyl group is removed from pyruvate and released as a molecule of carbon dioxide, leaving behind acetate

Describe step 2 of the link reaction.

Acetate is oxidised, and the electrons lost in the oxidation are picked up by NAD+ to form NADH.

Describe step 3 of the link reaction.

The acetyl groups, are attached to Coenzyme A to form acetyl CoA.

Summarise pyruvate oxidation.

Two molecules of pyruvate are converted into two molecules of acetyl CoA, two carbons are released as carbon dioxide, and 2 NADH are generated from NAD+.

What is an apoenzyme

The protein part of an enzyme that binds to the cofactor to form a holoenzyme