Cellular Respiration Notes

Cellular Respiration

Introduction

• Cellular respiration explains how the body creates energy out of food, especially carbohydrates.

Glycolysis

• Glycolysis is the first step and involves "cutting the sugar in half."
• When carbohydrates break down, they turn into glucose, the sugar we're focused on.
• Glucose can be broken down into different things, depending on the reaction or where it's needed in the body.
• If not used immediately, glucose is stored as glycogen.
• Glycolysis is a catabolic process where glucose is broken down into pyruvate.
• ATP is also produced during glycolysis.
• Glycolysis happens in the cytoplasm (the squishy part of the cell). So this process doesn't happen inside the mitochondria.
• The products are two ATPs, two pyruvates, and some NADH (electron carriers).

Pyruvate Oxidation

• Pyruvate oxidation is the second stage of cellular respiration.
• The pyruvate formed from glycolysis enters the mitochondria.
• Each pyruvate loses one carbon and turns into acetyl coenzyme A.
• Pyruvate oxidation involves oxidation, meaning it loses an electron.
• Pyruvate is converted to acetyl coenzyme A by losing a carbon, producing reduced electron carriers (CO_2).
• Reduced electron carriers pick up electrons during both glycolysis and pyruvate oxidation.
• They act like "magnets" or a "bus," collecting electrons along the way to the electron transport chain.

Citric Acid Cycle (Krebs Cycle)

• Acetyl coenzyme A powers the turning of the citric acid cycle.
• Acetyl coenzyme A enters the cycle and is broken down.
• With each spin of the cycle, more carbon dioxide (CO_2) and ATP are produced.
• The cycle spins twice to produce 2 (CO_2) and two ATPs.
• The citric acid cycle also produces more reduced electron carriers NADH and FADH2, which keep picking up electrons.

Oxidative Phosphorylation and Electron Transport Chain

• Oxidative phosphorylation is the final step where most ATP is made.
• NADH and FADH2 drop off their electrons at the electron transport chain.
• In the electron transport chain, NADH and FADH2 become oxidized to NAD+ and FAD+ as they drop off their picked-up electrons.
• Through redox reactions electrons transfer to other carriers, pumping protons across the wall.