Cellular Respiration: A Review Waiz and Lindsay

What is Cellular Respiration? Process of converting glucose and oxygen to water, carbon dioxide, and ATP Involves 3 stages: Glycolysis Krebs/Citric Acid Cycle Oxidative Phosphorylation

Adenosine Triphosphate (ATP) Cellular energy molecule The covalent bonds between phosphate groups stores energy Short term In cellular respiration, ADP is converted to ATP

Glycolysis

Glycolysis Literally means “splitting of sugar” Breakdown of a glucose molecule into two pyruvate molecules Occurs in the cytoplasm

Glycolysis Two phases: Energy investment phase Energy payoff phase Glycolysis occurs whether or not O2 is present All cells carry out glycolysis

Glycolysis Uses 2 ATP to split glucose molecule Net: 2 Pyruvates 2 H2O 2 NADH (electron carrier) 2 H+ Utilizes substrate-level phosphorylation

Glycolysis (Intermediate Step) To finish off, one carbon is removed from each of the two pyruvate molecules, resulting in two CO2 molecules being released Electrons are stripped, forming NADH Coenzyme A attaches to the two-carbon molecule, forming Acetyl CoA

Intermediate Step

Krebs/Citric Acid Cycle

Big Picture Occurs in the mitochondrial matrix Releases the remaining carbons from the remnant glucose Transfers the energy to NAD, FAD, and ADP Electrons extracted carried into ETC

Kreb’s Output For each acetyl CoA that enters the citric acid cycle, two carbon dioxide molecules are released in reactions that are coupled with the production of NADH molecules from the reduction of NAD+ molecules. Two FADH2 (another electron carrier) molecules and 2 ATP are made as well.

Electron Transport Chain & Chemiosmosis

ETC Reduced electron carriers (NADH and FADH2) give electrons to molecules near the beginning of the transport chain and turn back into NAD+, and FAD Electrons are passed down the chain, with each protein using energy from them to pull a proton against a concentration gradient Oxygen splits and combines with H+ to form water

Chemiosmosis Movement of ions down the concentration gradient Protons move through ATP synthase, phosphorylating ADP

Important Facts Not all cells need to use (or can’t use) the entire process of cellular respiration and some don’t even need it at all. These cells can use a combination of glycolysis and fermentation instead, which is utilized in the food industry in the form of lactic acid fermentation and alcoholic fermentation. Can anyone name three fermented foods?

fermentation

Total ATP Produced 30-38 ATP

Review