BCHM 4115 - Lectures 22-26

Explain the purpose of a hydride shift catalyzed by alcohol dehydrogenase.

Answer explanation

In catabolic reactions, a hydride ion (H⁻), which is a proton with two electrons, is transferred from a reduced substrate to NAD⁺. This hydride shift reduces NAD⁺ to NADH, a high-energy electron carrier. A second proton (H⁺) is also released into the surrounding solution. The NADH produced then carries these electrons to the electron transport chain, where they are donated (NADH is now oxidized to NAD⁺ to help generate ATP through oxidative phosphorylation.

Tags

NGSS.HS-PS1-4

What is the difference between anabolism and catabolism?

Answer explanation

Essentially, when catabolism breaks down complex molecules, electrons are released, whereas in anabolism, electrons are required to build these complex biomolecules.

Tags

NGSS.HS-LS2-3

NGSS.HS-LS2-5

What are the three regulatory enzymes in glycolysis?

Answer explanation

1. 1. Hexokinase

2. 2. Phosphofructokinase

3. 3. Pyruvate kinase

List three ways in which signal transduction receptors respond to hormone ligand binding?

Answer explanation

1. Via...

1. 1. G-protein coupled receptors

2. 2. Single transmembrane segment catalytic receptors

3. 3. Oligomeric Ion channels

Tags

NGSS.HS-LS1-3

Which of the following is NOT an example of a steroid hormone?

• insulin

• testosterone

• progesterone

• estrogen

Answer explanation

Insulin is a peptide hormone, as well as glucagon. Make sure you know the three main classes of hormones, and be able to categorize the examples presented on this slide.

_ heads "walk" along an actin filament, using ATP for energy.

Answer explanation

Muscle contraction is powered by the interaction between myosin and actin, where myosin "walks" along actin filaments in a repeated cycle. The myosin head binds ATP, which temporarily detaches it from the actin filament. It then rebinds in a new position, and the release of a phosphate from ATP triggers a "power stroke" that moves the actin filament. ADP is then released, and the process is repeated again.

What are the two sugars that can enter the glycolytic pathway ahead of PFK.

Answer explanation

Mannose and galactose.

The enzyme _ reduces pyruvate to lactate in lactic acid fermentation.

Answer explanation

What do the large negative ΔG values indicate at the three regulatory steps of glycolysis?

Answer explanation

The enzymes hexokinase, phosphofructokinase, and pyruvate kinase catalyze the regulatory steps of glycolysis and exhibit large negative ΔG values. This means these reactions are highly exergonic and strongly favorable under cellular conditions, driving the pathway irreversibly in the direction of pyruvate formation. Because these steps are essentially non-reversible, gluconeogenesis (the reverse pathway) requires different enzymes to bypass these energetically downhill reactions (specifically at steps 1, 3, and 10 of glycolysis).

Tags

NGSS.HS-LS1-7

NGSS.HS-PS1-4

In general, what is the does the Schiff base mechanism do in the glycolytic pathway?

Answer explanation

In the glycolytic pathway, the Schiff base mechanism helps catalyze the cleavage of fructose-1,6-bisphosphate into two 3-carbon molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P) via the enzyme fructose bisphosphate aldolase. It forms a covalent bond between the lysine residue in the enzyme's active site and the substrate, F-1,6-BP, stabilizing the intermediate. This makes the bond between carbon atoms easier to break, allowing the reaction to proceed efficiently.