Lecture 14 — Introduction to Metabolism

What is metabolism?

Sum of all chemical reactions in a cell.

What is a metabolic pathway?

Linked series of enzyme-catalyzed reactions.

What is catabolism?

Breakdown of molecules that releases energy.

What is anabolism?

Building molecules using energy.

How are catabolism and anabolism connected?

Catabolism supplies energy and building blocks for anabolism.

Is transcription anabolic or catabolic?

Anabolic because nucleotides are joined to build RNA.

What is free energy?

Energy available to perform work.

What is an energetically favorable reaction?

Reaction that releases free energy.

What is an energetically unfavorable reaction?

Reaction requiring energy input.

What is the first law of thermodynamics?

Energy cannot be created or destroyed, only converted.

What is the second law of thermodynamics?

Entropy of the universe tends to increase.

What is entropy?

Degree of disorder.

Do reactions that increase entropy tend to be favorable or unfavorable?

Energetically favorable.

Why does maintaining cellular order require energy?

Creating/maintaining order decreases entropy locally.

What is oxidation?

Loss of electrons.

What is reduction?

Gain of electrons.

What does LEO GER mean?

Lose Electrons Oxidize; Gain Electrons Reduce.

If a molecule gains hydrogen/electrons, is it oxidized or reduced?

Reduced.

If a molecule loses hydrogen/electrons, is it oxidized or reduced?

Oxidized.

Do oxidation and reduction happen together?

Yes.

When NAD+ gains electrons, what does it become?

NADH.

When FAD gains electrons/hydrogen, what does it become?

FADH2.

What is activation energy?

Initial energy required for a chemical reaction.

Do favorable reactions still have activation energy?

Yes.

Why do energetically favorable reactions need enzymes?

Without enzymes, activation energy can make them occur too slowly.

What do enzymes do to activation energy?

Lower it.

Do enzymes change whether a reaction is energetically favorable?

No.

Are enzymes consumed during a reaction?

No.

What is an activated carrier molecule?

Molecule that stores/transfers energy or chemical groups.

What does ATP commonly carry?

A high-energy phosphate group.

What do NADH and FADH2 carry?

High-energy electrons and hydrogen.

What does acetyl CoA carry?

An acetyl group.

What is the purpose of cellular respiration?

Extract energy from organic molecules to produce ATP.

What is step 1 of cellular respiration?

Glycolysis.

What happens in glycolysis?

Glucose is broken down to pyruvate.

What is step 2 of cellular respiration?

Pyruvate oxidation.

What happens during pyruvate oxidation?

Pyruvate is oxidized to form acetyl CoA.

What is step 3 of cellular respiration?

Citric acid cycle.

What happens in the citric acid cycle?

Acetyl CoA is oxidized to CO2 and energy carriers are produced.

What is step 4 of cellular respiration?

Oxidative phosphorylation.

What happens during oxidative phosphorylation?

Energy from carriers is used to make ATP.

What are the four stages in order?

Glycolysis → pyruvate oxidation → citric acid cycle → oxidative phosphorylation.

Why does cellular respiration break glucose down through many reactions?

Energy can be released gradually and captured efficiently in carrier molecules.

What does aerobic mean?

Occurs with/uses oxygen.

What does anaerobic mean?

Occurs without oxygen.