Biology 101 - Cellular Respiration

Flashcards about Cellular Respiration

Cellular Respiration

A cellular process that breaks down nutrient molecules produced by photosynthesizers with the associated production of ATP. It consumes oxygen and produces carbon dioxide (CO2).

Oxidation and Reduction in Cellular Respiration

Electrons are removed from glucose and transferred to oxygen.

Electron shuttle busses

Specialized carriers ultimately transferring electrons to the cell’s “terminal electron carrier”. Examples include NAD+/NADH and FAD/FADH2.

NAD+ (nicotinamide adenine dinucleotide)

As a coenzyme of oxidation-reduction, it is Oxidized when it gives up electrons, and Reduced when it accepts electrons. Each molecule is used over and over again.

FAD (flavin adenine dinucleotide)

Also a coenzyme of oxidation-reduction that is Sometimes used instead of NAD+. It Accepts two electrons and two hydrogen ions (H+) to become FADH2.

Glycolysis

The breakdown of glucose into two molecules of pyruvate, occurring in the cytoplasm and forming ATP. It does not utilize oxygen (anaerobic).

Preparatory (prep) reaction

Both molecules of pyruvate are oxidized and enter the matrix of the mitochondria. Electron energy is stored in NADH. Two carbons are released as CO2 (one from each pyruvate).

Citric acid cycle

Occurs in the matrix of the mitochondrion and produces NADH and FADH2. A series of reactions releases 4 carbons as CO2. Turns twice per glucose molecule (once for each pyruvate). Produces two immediate ATP molecules per glucose molecule.

Electron transport chain (ETC)

A series of carriers on the cristae of the mitochondria. It Extracts energy from NADH and FADH2, passes electrons from higher to lower energy states, and produces 32 or 34 molecules of ATP by chemiosmosis.

Energy-Investment Step of Glycolysis

Two ATP are used to activate glucose, and glucose splits into two G3P molecules.

Energy-Harvesting Steps of Glycolysis

Oxidation of G3P occurs by removal of electrons and hydrogen ions. Two electrons and one hydrogen ion are accepted by NAD+ resulting in two NADH. Four ATP are produced by substrate-level ATP synthesis.

Fermentation Process

Reduces pyruvate to either lactate or alcohol and CO2. NADH transfers its electrons to pyruvate.

Alcoholic fermentation

Carried out by yeasts, produces carbon dioxide and ethyl alcohol, and is used in the production of alcoholic spirits and breads.

Lactic acid fermentation

Carried out by certain bacteria and fungi, produces lactic acid (lactate), and is used commercially in the production of cheese, yogurt, and sauerkraut.

Preparatory (prep) Reaction Details

End product of glycolysis, pyruvate, enters the mitochondrial matrix and is converted to a 2-carbon acetyl group. Attached to Coenzyme A to form acetyl-CoA. Electrons picked up (as hydrogen atom) by NAD+, producing NADH. CO2 is released.

Citric Acid Cycle Process

Begins with the addition of a C2 acetyl group (from acetyl-CoA) to a C4 molecule (oxaloacetate), forming a C6 molecule (citric acid). NADH and FADH2 capture energy-rich electrons, and ATP is formed by substrate-level phosphorylation.

Electron Transport Chain Carrier Molecules

Pass energy-rich electrons successively from one to another through Complex arrays of protein and cytochrome and Proteins with heme groups with central iron atoms.

Energy Yield from Electron Transport Chain

Electrons from NADH deliver enough energy to make 3 ATPs, while Those from FADH2 have only enough for 2 ATPs. “Spent” hydrogens combine with oxygen.

Chemiosmosis

The electron transport chain complexes pump H+ from the matrix into the intermembrane space of the mitochondrion. ATP synthase allows H+ to flow down its gradient. The flow of H+ drives the synthesis of ATP from ADP and inorganic phosphate by ATP synthase.

Catabolism

Glucose is broken down in cellular respiration, Fats break down into glycerol and three fatty acids, and Amino acids break down into carbon chains and amino groups.

Deamination

Removal of NH2 that occurs in the liver and results in poisonous ammonia (NH3) that is quickly converted to urea.

Anabolism: Carbohydrates

Start with acetyl-CoA and basically reverse glycolysis (but different pathway).

Anabolism: Fats

G3P converted to glycerol, and Acetyl groups are connected in pairs to form fatty acids.

Anabolism: Proteins

They are made up of combinations of 20 different amino acids. Some (11) can be synthesized by adult humans, but others (9) cannot and are considered Essential amino acids that Must be present in the diet.

Electron Transport Chain Energy Source

Electrons passed to ETC were energized by the sun in photosynthesis, while in mitochondria electrons, energized electrons were removed from glucose.