Cellular Respiration

Question of the Day How are the products of photosynthesis related to cellular respiration? What organisms undergo cellular respiration? Products of photosynthesis are the reactants in cellular respiration. All organisms, including photosynthetic organisms, undergo cellular respiration.

Overview of Cellular Respiration Stage 1 - Glycolysis Glucose  Pyruvate Producing NADH and ATP on the side Stage 2 – Respiration Requires oxygen to be present Aerobic respiration: Take pyruvate and NADH  ton of ATP Occurs in mitochondria of eukaryotic cells Occurs in cell membrane in prokaryotic cells Anaerobic Respiration: no oxygen needed Pyruvate  lactate or ethanol and CO2

Glycolysis An enzyme-assisted anaerobic process that breaks down one six-carbon molecule of glucose to two 3-carbon pyruvates Pyruvate: Ion of a 3-carbon organic acid (pyruvic acid) Energy Glucose breaks down Hydrogens are transferred to NAD+ NADH electron carrier formed

Glycolysis Steps Phosphate groups from two ATP molecules are transferred to a glucose molecule. The resulting 6 carbon compound is broken down to two 3 carbon compounds, each with a phosphate group. 2 NADH molecules are produced, and one more phosphate group is transferred to each 2 carbon compound. Each 3 carbon compound is converted to a 3 carbon pyruvate, producing four ATP molecules in the process

Glycolysis Energy Summary Uses 2 ATP Produces 4 ATP Total gain 2 ATP

Aerobic Respiration Pyruvate enters mitochondria  Acetyl Pyruvate = 3 Carbons  Acetyl = 2 Carbons Products of Conversion = CO2, NADH, Acetyl group Acetyl Group + coenzyme = compound Acetyl CoA Krebs cycle Enzyme-assisted chemical reactions in which acetyl-CoA enters

Krebs Cycle Stages Acetyl CoA + 4C compound  6C compound releasing coenzyme A CO2 released from 6C compound  5C compound. Electrons transferred to NAD+  NADH CO2 released from 5C compound  4C compound, also creating ATP and NADH 4C reconfigured releasing. Electrons transferred to FAD  FADH2 4C reconfigured  original cycle starter. NADH produced.

Krebs Cycle Summary NADH and FADH2 contain the energy from glucose and pyruvate Electron Carriers 4 carbon compound recycled Acetyl CoA can re-enter the cycle

Electron Transport Chain Inner membrane of mitochondria NADH and FADH2 contribute electrons “passed like a ball down a line of people” Energy used to pump H+ ions out of inner compartment of mitochondria Concentration gradient formed Ions diffuse back in through carrier protein Carrier protein adds phosphates to ADP = ATP Oxygen molecules form with Hydrogens = Water Oxygen is the final electron acceptor

Anaerobic Respiration When no oxygen is present we have no final electron acceptor Instead the electrons from NADH are transferred to pyruvate (taken from glycolysis) NAD+ recycled, ATP made Organic hydrogen acceptor used instead of Oxygen Fermentation

Types of fermentation in Anaerobic Respiration Lactic Acid Fermentation Used by some bacteria and fungi to make foods like yogurt and cheeses 3C pyruvate  Lactate ion used from organic lactic acid Lets glycolysis continued making ATP as long as the supply of glucose remains. Alcoholic Fermentation Yeast used to make wine and beer 3C pyruvate  2C compound releasing CO2 Electrons NADH + 2C compound  ethanol