Chapter 6: Cellular Energetics

Calvin-Benson Cycle

The dark reactions of photosynthesis, which use ATP and NADPH produced in the light-dependent reactions to convert CO2 into carbohydrates, also known as the Calvin-Benson Cycle.

CAM Plants

Plants that live in hot climates and have evolved to temporally separate carbon fixation and the Calvin cycle by opening their stomata at night and incorporating CO2 into organic acids, which are then broken down during the day while the light reactions run.

C4 Plants

Plants that have evolved a different leaf anatomy that allows them to perform CO2 fixation in a different part of the leaf from the rest of the Calvin cycle, preventing photorespiration and producing a four-carbon molecule as the first product of carbon fixation.

Aerobic Respiration

The process of breaking down glucose into ATP in the presence of oxygen, consisting of four stages: glycolysis, formation of acetyl-CoA, the Krebs cycle, and oxidative phosphorylation (the electron transport chain + chemiosmosis).

Glycolysis

The first stage of aerobic respiration, where glucose is broken down into two three-carbon molecules called pyruvic acid, resulting in the net production of two molecules of ATP and two molecules of NADH.

Formation of Acetyl-CoA

The second stage of aerobic respiration, where pyruvic acid is transported to the mitochondrion and converted to acetyl-coenzymeA (acetyl-CoA) and CO2 is released, producing two molecules of NADH.

Krebs Cycle

The third stage of aerobic respiration, also known as the citric acid cycle, where each molecule of acetyl-CoA combines with oxaloacetate to form citric acid, which is then converted to several other molecules, producing 1 ATP, 3 NADH, and 1 FADH2 per turn of the cycle.

Oxidative Phosphorylation

The fourth

Anaerobic Respiration

A type of respiration that occurs when oxygen is not available, causing the electron transport chain to stop working and the mitochondrial production of acetyl-CoA and the Krebs cycle to cease, but glycolysis can continue to run.

Fermentation

A process that occurs in emergencies when oxygen is not available, where pyruvate turns into either lactic acid or ethanol, which are toxic at high concentrations.

Yeast

A type of organism that undergoes fermentation and produces ethanol and carbon dioxide.

Lactic Acid

A byproduct of fermentation that is produced by some bacteria and muscle cells during anaerobic respiration.

Enzymes

Biological catalysts that speed up reactions by lowering activation energy and helping the transition state to form.

Catalyst

Something that speeds up a reaction.

Enzyme Specificity

Each enzyme catalyzes only one kind of reaction.

Substrate

The molecule targeted by an enzyme in an enzymatic reaction.

ATP

Adenosine Triphosphate, a molecule that provides energy for cellular processes.

Cellular Respiration

The process of breaking down sugar to produce ATP.

Autotrophs

Organisms that can produce their own food through photosynthesis.

Photosynthesis

The process by which autotrophs convert light energy into chemical energy in the form of sugar.

Heterotrophs

Organisms that obtain their food by consuming other organisms.

Glucose

A simple sugar that is an important source of energy for living organisms.