Overview of Energy-Releasing Pathways

AP BiologyFall 2010

Heterotrophs: get energy by eating plants and one another

Autotrophs: get energy from the sun

ATP is the prime energy carrier for all cells, both autotrophic and heterotrophic

Anaerobic: reactions that do not use free oxygen

Anaerobic respiration and fermentation can release small quantities of energy without the use of oxygen First energy-releasing metabolic pathways Skeletal muscles use fermentation

Aerobic: reactions that use free oxygen

Aerobic respiration is the main energy-releasing pathway leading to ATP formation in eukaryotes Occurs in mitochondria

Every cell begins its energy-releasing pathways with glycolysis, which occurs in the cytoplasm and produces two molecules of pyruvate

Fermentation produces a net yield of two ATPs

Aerobic respiration yields 36 ATPs

Aerobic respiration gets the most ATP for each glucose molecule “The most bang for your buck”

The aerobic route is summarized: C6H12O6 + O2 CO2 + H2O

Three series of reactions are required for aerobic respiration

1.Glycolysis: the breakdown of glucose to pyruvate; small amounts of ATP are generated

2.Krebs cycle: degrades pyruvate to carbon dioxide and water, ATP is produced, and NAD and FAD accept H+ ions and electrons to be carried to the electron transfer chain

3. Electron transfer phosphorylation: processes the H+ ions and electrons to generate high yields of ATP; oxygen is the final electron acceptor

Coenzymes: NAD+ (nicotinamide adenine dinucleotide) FAD (flavin adenine dinucleotide)

Both accept electrons and hydrogen derived from intermediates that form during glucose breakdown

When two coenzymes are carrying electrons and hydrogen, in reduced form NADH and FADH2

1. What are NAD+ and FAD?2. What is the formula for aerobic

respiration?3. What are the three stages of aerobic

respiration?4. How much energy does fermentation

and anaerobic respiration produce? Do they use oxygen?

1. They are coenzymes that both accept electrons and hydrogen derived from intermediates that form during glucose breakdown.

2. The formula for aerobic respiration is: C6H12O6 + O2 CO2 + H2O

3. The three stages of aerobic respiration are: Glycolysis, Krebs cycle, electron transfer phosphorlation.

4. Fermentation and anaerobic respiration produces small amounts of energy and does not require oxygen.