lab pt 7

What is fermentation?

A metabolic process that breaks down carbohydrates without using an electron transport chain.

Does fermentation require oxygen?

No. Fermentation does not require oxygen.

What is the main purpose of fermentation?

To regenerate NAD⁺ so glycolysis can continue producing ATP.

What are carbohydrates (CHO)?

Organic compounds containing carbon, hydrogen, and oxygen that can be used as energy sources.

What are possible products of carbohydrate fermentation?

Organic acids, gases, alcohols, and other organic compounds.

What acids can bacteria produce through fermentation?

Lactic acid, acetic acid, and other organic acids.

What gases can be produced during carbohydrate fermentation?

Carbon dioxide and hydrogen.

How is acid production detected during fermentation?

Using a pH indicator that changes color when the environment becomes acidic.

What is a Durham tube and how does it detect gas?

A small inverted tube inside broth that collects gas produced by bacteria as a visible bubble.

What does a positive fermentation test look like?

A color change indicating acid production; a bubble in the Durham tube indicates gas production.

What does a negative fermentation test look like?

No evidence of fermentation, such as no acid-related color change or gas production.

What is respiration?

A metabolic process that uses an electron transport chain to generate ATP.

What is aerobic respiration?

Respiration that uses oxygen as the final electron acceptor.

Can eukaryotic cells and bacteria perform aerobic respiration?

Yes. Eukaryotes use mitochondria; bacteria use their cell membrane-associated electron transport chains.

What are the waste products of aerobic respiration?

Carbon dioxide and water.

What happens to glucose during aerobic respiration?

It is broken down and oxidized, releasing energy used to produce ATP.

What is anaerobic respiration?

Respiration using an electron transport chain with a final electron acceptor other than oxygen.

What are examples of alternative final electron acceptors in anaerobic respiration?

Nitrate, sulfate, and carbon dioxide.

What is the difference between aerobic and anaerobic respiration?

Aerobic uses oxygen as the final electron acceptor; anaerobic uses another molecule.

What is glycolysis?

The breakdown of glucose into two molecules of pyruvate.

Does glycolysis require oxygen?

No. Glycolysis can occur with or without oxygen.

How does anaerobic respiration differ from fermentation?

Anaerobic respiration uses an electron transport chain and an alternative final electron acceptor; fermentation does not use an electron transport chain.

What is selective media?

Media that favor certain microorganisms while inhibiting others.

What is differential media?

Media that distinguish microorganisms based on visible biochemical or metabolic differences.

Can media be both selective and differential?

Yes. Some media inhibit certain bacteria while distinguishing between those that grow.

What is MacConkey agar and why is it selective?

A selective and differential medium; bile salts and crystal violet inhibit most Gram-positive bacteria.

Why is MacConkey agar differential?

It distinguishes lactose fermenters from non-lactose fermenters using a pH indicator.

What are the results of lactose fermentation on MacConkey agar?

Lactose fermenters: pink/red colonies. Non-lactose fermenters: colorless or pale colonies.

What is mannitol salt agar (MSA) and why is it selective?

A medium with high salt concentration that favors salt-tolerant bacteria, especially staphylococci.

Why is MSA differential?

It distinguishes bacteria that ferment mannitol from those that do not.