Control of Enzyme Activity and Basic Metabolism

What inhibits a pathway in feedback inhibition?

The product

define: Competitive inhibition

An inhibitor competes with the substrate for binding to the active site.

what inhibition increases the amount of substrate needed to achieve maximum rate of catalysis?

competitive

what type of inhibition does NOT change the maximum possible rate of the enzyme's catalysis?

competitive

How can you overcome competitive inhibition?

Providing more substrate.

define: Non-competitive inhibition

An inhibitor binds to an allosteric site on the enzyme to deactivate it.

what happens with the substrate in non-competitive inhibition?

substrate still have access the active site, but the enzyme is no longer able to catalyze the reaction as long as the inhibitor remains bound.

What are the two major parts of metabolism

Catabolism and anabolism.

What is catabolism?

Breaking molecules down to release energy.

What is anabolism?

Using energy to build molecules for storage.

What is another name for metabolism?

Cellular respiration.

What are the steps of anaerobic metabolism?

Glycolysis → Fermentation (alcohol or lactic acid).

What are the four steps of aerobic metabolism?

Glycolysis → Oxidative decarboxylation → Krebs cycle → Electron transport chain.

How much ATP is produced from aerobic metabolism of one glucose molecule?

About 30 ATP.

How much ATP is produced from anaerobic metabolism of one glucose molecule?

2 net ATP.

What is the overall equation for aerobic metabolism of glucose?

C6​H12​O6​+6O2​→6CO2​+6H2​O

In aerobic respiration, where does the oxygen in water come from?

Molecular oxygen (O₂) that is breathed in.

In aerobic respiration, where do the carbons from glucose end up?

Carbon dioxide (CO₂).

What happens to glucose during aerobic metabolism?

It is completely oxidized to CO₂.

What happens to oxygen during aerobic metabolism?

O₂ is completely reduced to H₂O.

Why is energy released during aerobic metabolism?

Electrons pass from glucose to oxygen through redox reactions.

What is glycolysis?

Conversion of glucose (6C) into 2 pyruvate molecules (3C each).

Where does glycolysis occur?

Cytosol

How much ATP does glycolysis produce?

2 net ATP per glucose.

How many NADH molecules are produced in glycolysis?

2 NADH per glucose.

Does glycolysis occur under aerobic or anaerobic conditions?

Both.

What inhibits glycolysis?

ATP.

Where does oxidative decarboxylation occur?

Mitochondrial matrix.

What does oxidative decarboxylation convert pyruvate into?

Acetyl-CoA.

How many carbons are removed during oxidative decarboxylation?

One carbon is removed from pyruvate (3C → 2C acetyl group).

How much NADH is produced during oxidative decarboxylation?

NADH per pyruvate.

Does oxidative decarboxylation require oxygen?

Yes.

What is the purpose of fermentation?

To regenerate NAD⁺ for glycolysis.

Where does fermentation occur?

Cytosol

What happens to pyruvate during lactic acid fermentation?

Pyruvate is reduced to lactate.

What happens to pyruvate during alcohol fermentation?

Pyruvate is reduced to ethanol.

What molecule is oxidized during fermentation?

NADH → NAD⁺.

Which organisms commonly perform alcohol fermentation?

Bacteria and yeast.

Which organisms perform lactic acid fermentation?

Humans.

What are other names for the Krebs cycle?

TCA cycle, citric acid cycle, tricarboxylic acid cycle.

Where does the Krebs cycle occur?

Mitochondrial matrix.

What molecule enters the Krebs cycle?

Acetyl-CoA.

How many NADH molecules are produced per acetyl-CoA in the Krebs cycle?

3 NADH.

How many FADH₂ molecules are produced per acetyl-CoA in the Krebs cycle?

1 FADH₂.

How much ATP (or GTP) is produced per acetyl-CoA in the Krebs cycle?

1 ATP (or GTP).

What inhibits the Krebs cycle?

ATP and NADH.

Where does the electron transport chain occur?

Inner mitochondrial membrane (cristae).

What is the main function of the ETC?

To transfer electrons and generate a proton gradient for ATP production

What molecule is oxidized in the ETC?

NADH.

What molecule is reduced in the ETC?

O₂ → H₂O.

Why does NADH produce more ATP than FADH₂?

NADH enters the ETC at a higher-energy point.

Where does FADH₂ enter the ETC?

At Coenzyme Q (skips FMN).

What enzyme uses the proton gradient to make ATP?

ATP synthase.

What is oxidative phosphorylation?

ATP production driven by the proton gradient created by the ETC.

Where is the proton concentration highest in mitochondria during ETC activity?

Intermembrane space.

What drives protons back into the mitochondrial matrix?

The proton gradient.

What poisons inhibit the ETC?

Cyanide, azide, and carbon monoxide.

Where does β-oxidation occur?

Mitochondrial matrix.

What enzyme breaks down fats into fatty acids?

Lipases.

What does triacylglycerol break down into?

Glycerol and free fatty acids.

What is β-oxidation?

Breakdown of fatty acids into acetyl-CoA units.

How many carbons are removed at a time during β-oxidation?

Two carbons.

What products are generated during β-oxidation?

Acetyl-CoA, NADH, and FADH₂.

Why are fats considered energy-rich?

They produce the most energy per gram.

What breaks proteins down into amino acids?

Peptidases.

What happens to the nitrogen from amino acids in humans?

Converted to urea.

What do birds and reptiles convert nitrogen into?

Uric acid.

What can the carbon skeletons of amino acids become?

Pyruvate, acetyl-CoA, oxaloacetate, or other metabolic intermediates.