Bacterial Metabolism

Flashcards covering key concepts from carbohydrate catabolism in microbes, including glycolysis, energy carriers, ATP formation, respiration types, and fermentation as described in the notes.

What mnemonic is used to remember that oxidation is the loss of electrons and reduction is the gain of electrons?

Oil Rig: Oxidation = loss of electrons; Reduction = gain of electrons.

What are energy carriers and give examples mentioned?

Molecules that shuttle high-energy electrons; examples include NAD+, NADH, NADP+, NADPH, FAD, and FADH2 (often B vitamin derivatives).

Where is energy stored in biological systems and in what two forms?

Energy is stored in ATP bonds and in electron carriers (e.g., NADH, NADPH, FADH2) that carry electrons.

What is the energy currency of the cell and how many high-energy phosphate bonds does ATP have according to the notes?

ATP is the energy currency; it has two high-energy phosphate bonds (the addition of a third phosphate forms ATP from ADP).

What is substrate-level phosphorylation?

Direct transfer of a phosphate group from a substrate to ADP to form ATP.

Where does glycolysis occur in bacteria, and does it require oxygen?

Glycolysis occurs in the cytoplasm and does not require oxygen (not oxygen dependent).

What are the inputs and outputs of glycolysis per glucose molecule, including net gain?

Inputs: one glucose, two ATP spent, NAD+. Outputs: two pyruvate, four ATP formed, two NADH; net gain is two ATP and two NADH (since two ATP were invested).

What are the two stages of glycolysis and the key intermediate?

Energy investment phase and energy payoff phase; key intermediate is glyceraldehyde-3-phosphate (G3P).

What is the most common glycolysis pathway called?

EMP pathway (Embden-Meyerhof-Parnas).

What happens during the transition reaction in terms of substrates and products?

Pyruvate is converted to acetyl-CoA, producing NADH; links glycolysis to the Krebs cycle; occurs in the cytoplasm for bacteria.

What are the outputs of the Krebs cycle after acetyl-CoA enters?

ATP (via substrate-level phosphorylation), NADH, FADH2, CO2, and water; multiple electron carriers produced.

What is the role of the electron transport chain and what is chemiosmosis?

ETC transfers electrons along a chain, pumping protons to create a proton gradient; chemiosmosis uses this gradient to power ATP synthase to make ATP.

Name the two key enzymes in the electron transport chain that you should know.

Cytochrome oxidase and ATP synthase.

What is the final electron acceptor in aerobic respiration?

Oxygen.

Why can some organisms not perform aerobic respiration even if oxygen is present?

If they lack cytochrome oxidase, lack enzymes to neutralize reactive oxygen species (e.g., catalase), or there is no oxygen.

What are facultative anaerobes and obligate anaerobes? Give examples.

Facultative anaerobes can grow with or without oxygen (e.g., E. coli); obligate anaerobes cannot tolerate oxygen and lack enzymes like cytochrome oxidase and catalase (e.g., Clostridium tetanus).

What is anaerobic respiration and how does energy yield compare to aerobic respiration?

Final electron acceptors are inorganic molecules (nitrate, sulfate, fumarate); yields about 20 ATP, less than the ~36 ATP of aerobic respiration.

What happens during fermentation and what is its purpose?

When no final electron acceptor is available, fermentation recycles NADH by converting pyruvate to lactic acid or acetaldehyde to ethanol; yields about 2 ATP and no more energy beyond that.

What are the two main fermentation end products described?

Lactic acid (from pyruvate) and ethanol (from acetaldehyde/acetyl-CoA).

What is the purpose of fermentation beyond energy production?

To recycle NADH back to NAD+ so glycolysis can continue.

What is the difference between substrate-level phosphorylation and oxidative phosphorylation?

Substrate-level phosphorylation directly transfers a phosphate to ADP to make ATP (does not require oxygen); oxidative phosphorylation uses a proton gradient and ATP synthase to make ATP and requires oxygen.

What is the proton motive force?

The energy stored in the proton (H+) gradient across a membrane that drives ATP synthesis via ATP synthase.

Which organism example demonstrates switching between aerobic and anaerobic respiration and what is it called?

Escherichia coli demonstrates facultative anaerobic metabolism, switching between aerobic and anaerobic respiration depending on oxygen availability.

What is the difference in oxygen dependency between glycolysis and the subsequent steps like Krebs cycle and electron transport chain?

Glycolysis is oxygen-independent; Krebs cycle and electron transport/oxidative phosphorylation generally require oxygen or an available final electron acceptor (aerobic) or alternative acceptors (anaerobic).