Chemiosmosis

- electrons are moved up and down an electron transport system

- energy that is given off by their movement is used to pump protons to one side of the membrane

- an electrochemical gradient builds up and the protons want to come back across the membrane

- the protons are allowed back across

Redox Reactions

- short for oxidization/reduction reactions

- when a molecule loses an electron, it just got oxidized

- when a molecule gains an electron, it just got reduced

- one cannot occur without the other happening simultaneously

- if you set up a string of these reactions, it is called an electron transport system

Important molecules

H+ = proton

NADH - electron and hydrogen carrier (taxi cab)

• When the “taxi” is empty = NAD+

• When the “taxi” is full = NADH

FADH2 - electron and hydrogen carrier (taxi cab)

• When the “taxi” is empty = FAD+

• When the “taxi” is full = FADH2

Glycolysis

• Evolved around 3.8 billion years ago

• Anaerobic

• Purpose was to create ATP

• Occurs in the cytoplasm of all living cells

• 10 steps, each requiring a different enzyme

• Produces ATP by substrate-level phosphorylation

• ADP gets a P from a phosphate-bearing intermediate

Krebs Cycle

• Begins with the oxidation of pyruvate

• Oxidative decarboxylation - every time this occurs, a CO2 is produced, as well as an NADH

• Is a cycle, so intermediates are regenerated.

Electron transport phosphorylation

• Chemiosmosis occurs!

• Most of the ATP is made here.

• Electron and H+ carriers “drive” electrons and H+ to the electron transport system.

• Electrons are passed down the electron transport chain, and H+ are pumped into the intermembrane space. They build up there, and come back into the matrix via ATP synthase. ATP is made.

• Oxygen is the final electron acceptor. It accepts electrons and H+ and 6 H2Os are produced.

Fermentation

• Harvests chemical energy without using either oxygen or an electron transport system

• An extension of glycolysis that allows continuous generation of ATP by the substrate-level phosphorylation of glycolysis

• Under aerobic conditions, NAD+ is recycled from NADH by the transfer of electrons to the electron transport system.

• An anaerobic alternative is to transfer electrons from NADH to pyruvate, the end product of glycolysis.

Alcohol Fermentation

• Pyruvate is converted to ethanol in 2 steps.

• The first step releases carbon dioxide from the pyruvate, which is converted to the 2 C acetate.

• In the second step, acetate is reduced by NADH to form ethanol.

• This regenerates the supply of NAD+ needed for glycolysis.

• Bacteria and yeast (beer, wine, etc.)

Lactic Acid Fermentation

• Pyruvate is reduced directly by NADH to form lactate as an end product, with no release of CO2.

• Fungi, bacteria (cheese, yogurt)
• Human muscle cells make ATP by lactic acid fermentation when oxygen is scarce.

What gas is NEEDED for cellular respiration?

Oxygen

What gas is PRODUCED during cellular respiration?

Carbon Dioxide

Reactants

-Glucose

-oxygen

Summary Equation

C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + ATP

Reactants Products