BIOL 307 - Energy Generation

What are the three major ways bacteria can generate energy?

Aerobic respiration, anaerobic respiration, and fermentation.

What is aerobic respiration?

A form of respiration in which oxygen (O₂) is the final electron acceptor.

What is anaerobic respiration?

A form of respiration in which the final electron acceptor is NOT oxygen.

What can serve as the final electron acceptor during anaerobic respiration?

Nitrogen compounds, sulfate, ferric iron, or CO₂.

What is fermentation?

A partial breakdown of glucose that produces acids, alcohols, and/or gas.

What is the key difference between anaerobic respiration and fermentation?

Anaerobic respiration uses an electron transport chain (ETC) and a final electron acceptor other than O₂. Fermentation does not use an ETC and partially breaks down glucose.

How can you distinguish aerobic respiration from anaerobic respiration?

Aerobic respiration uses O₂ as the final electron acceptor, while anaerobic respiration uses a final electron acceptor other than O₂.

How can you distinguish anaerobic respiration from fermentation?

Anaerobic respiration uses an ETC and a terminal electron acceptor. Fermentation involves partial glucose breakdown and produces acids, alcohols, and/or gases.

What happens to carbon during glycolysis?

Glucose is broken down into smaller carbon-containing molecules, ultimately producing pyruvate.

What happens to carbon during the TCA cycle?

Carbon compounds are further broken down, releasing CO₂ and transferring energy to electron carriers.

What happens to electrons during catabolism?

Electrons are removed from energy-rich molecules and transferred to electron carriers such as NAD⁺, producing NADH.

Why are NAD⁺ and NADH important in metabolism?

NAD⁺ accepts electrons to become NADH. NADH carries high-energy electrons to later reactions.

Why must NAD⁺ be regenerated?

Cells need NAD⁺ available to continue accepting electrons during metabolic reactions. Without NAD⁺, important catabolic reactions cannot continue.

How is NAD⁺ regenerated differently during respiration and fermentation?

Respiration transfers electrons through an ETC to a final electron acceptor. Fermentation transfers electrons to organic molecules produced during metabolism.

What is an electron transport chain (ETC)?

A series of electron-transfer reactions that uses electron energy to generate a proton motive force.

How does the ETC help generate ATP?

Electron movement through the ETC creates a proton motive force that can drive ATP production.

What is oxidative ATP production?

ATP production using the proton motive force generated by the electron transport chain.

What is substrate-level ATP production?

ATP is directly synthesized using an energy-rich intermediate.

Which energy-generating strategies use an ETC?

Aerobic respiration and anaerobic respiration.

Which process is characterized by partial breakdown of glucose into acids, alcohols, and/or gas?

Fermentation.

Why don't all bacteria use the same metabolic pathways?

Bacteria have different enzymes and metabolic pathways, allowing them to use different substrates, produce different end products, and grow under different conditions.

Why might bacteria use different metabolic strategies depending on their environment?

Environmental conditions, such as oxygen availability and available nutrients, affect which metabolic pathways a bacterium can use.

What is a metabolic phenotype?

A measurable characteristic resulting from an organism's metabolic capabilities, such as which substrates it uses or which end products it produces.

How can metabolic phenotypes be used to identify bacteria?

Different bacteria have different enzymes and pathways, so they may use different substrates or produce different end products. These differences can distinguish organisms.

Isolate A ferments glucose → acid + gas. What does this tell you?

Isolate A has metabolic pathways that allow it to ferment glucose and produce both acid and gas.

Isolate B ferments glucose → acid but does not ferment lactose. What does this tell you?

Isolate B can ferment glucose but lacks the metabolic capability needed to ferment lactose.

A bacterium dies when exposed to atmospheric O₂. Why is this important when studying the bacterium?

Oxygen physiology affects where the organism can grow, how specimens should be handled, and how it can be cultured.

Why is bacterial metabolism important for human health?

Metabolism helps determine where bacteria can live, how they can be identified, and which bacterial pathways or enzymes might be targeted for treatment.

Why could a bacterial metabolic pathway that is absent from human cells be a useful antimicrobial target?

It could provide a selective target because the pathway is present in the bacteria but absent from human cells.