Metabolic Pathways

Glycolysis

Breaks one 6-carbon glucose into two 3-carbon pyruvate molecules; nets 2 ATP and 2 NADH.

PFK-1

Main regulated, committed-step enzyme of glycolysis.

Pyruvate

3-carbon product of glycolysis.

PDC

Pyruvate dehydrogenase complex; converts pyruvate into acetyl-CoA.

Acetyl-CoA

2-carbon molecule connecting carbohydrate and fat metabolism to the Krebs cycle.

Krebs cycle

Oxidizes acetyl-CoA-derived carbon and generates NADH and FADH2.

ETC

Electron transport chain; uses electrons from NADH and FADH2 to support ATP production.

Oxidative phosphorylation

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

NADH

Reduced electron carrier that donates electrons to the ETC.

FADH2

Reduced electron carrier that donates electrons to the ETC.

Fermentation

Regenerates NAD+ when the ETC cannot operate, allowing glycolysis to continue.

Cytosol

Where does glycolysis occur?

Matrix

Where does the Krebs cycle occur in eukaryotic cells?

Inner-membrane

Where does the ETC occur?

Pyruvate

What does glycolysis produce? (main 3-carbon product)

Acetyl-CoA

What molecule links pyruvate to the Krebs cycle?

NAD+

What carrier must fermentation regenerate for glycolysis?

Gluconeogenesis

Makes glucose from non-carbohydrate precursors.

Glycogenesis

Builds glycogen for glucose storage.

Glycogenolysis

Breaks down glycogen.

Glucokinase

Enzyme named in the lecture's glycolysis pathway; phosphorylates glucose.

Glucose-6-phosphatase

Enzyme that removes phosphate from glucose-6-phosphate to form free glucose.

Insulin

Hormone associated with high blood glucose and glucose storage.

Glucagon

Hormone associated with low blood glucose; promotes liver glucose release.

Gluconeogenesis

What pathway makes new glucose?

Glycogenolysis

What pathway breaks down stored glycogen?

Glycogenesis

What pathway stores glucose as glycogen?

ATP

What molecule inhibits PFK-1 when energy is abundant?

Pentose-phosphate pathway

Uses glucose-6-phosphate to generate NADPH and ribose-5-phosphate.

NADPH

Provides reducing power for fatty-acid synthesis and antioxidant defense.

Ribose-5-phosphate

5-carbon sugar used to build nucleotides.

PPP

What pathway produces NADPH and ribose-5-phosphate?

PPP

What pathway provides reducing power for fatty-acid synthesis?

Lipase

Enzyme that breaks triglycerides into glycerol and fatty acids.

Beta-oxidation

Breaks fatty acids into 2-carbon acetyl-CoA units and generates NADH and FADH2.

Fatty-acid synthesis

Builds fatty-acid chains in the cytosol using acetyl-CoA, malonyl-CoA, ATP, and NADPH.

Carnitine

Shuttle system involved in transporting long-chain fatty-acid groups into the mitochondrial matrix.

Matrix

Where does beta-oxidation occur?

Cytosol

Where does fatty-acid synthesis occur?

Acetyl-CoA

What 2-carbon molecule is released repeatedly during beta-oxidation?

Ketogenesis

Forms ketone bodies from acetyl-CoA, especially during prolonged starvation.

Glucogenic

Amino acid classification whose carbon skeleton can contribute to glucose production.

Ketogenic

Amino acid classification whose carbon skeleton can form acetyl-CoA or ketone-body precursors.

Ketogenesis

What pathway forms ketone bodies?

Acetyl-CoA

What molecule connects fatty-acid oxidation to ketogenesis?

Urea

What is the main nitrogen-containing waste product formed when excess amino-acid nitrogen is processed?