AP Bio Unit 3: Cellular Energetics Flashcards

Flashcards on Cellular Energetics for AP Biology Exam

Enzymes

Usually proteins, some RNAs, catalyze reactions in cells by lowering activation energy, increasing reaction rates. Highly specific due to active site complementing substrate shape and charge. Function optimally under narrow conditions of pH, ionic concentration, and temperature.

Active Site

The specific region of an enzyme where the substrate binds and where catalysis occurs.

Substrate

The substance on which an enzyme acts.

Denaturation

A change in the shape of an enzyme, usually due to changes in pH, temperature, or ion concentration that lowers or completely negates enzyme function.

Reversible Denaturation

When restoration of optimal conditions restores the enzyme's function as it regains its optimal shape.

Irreversible Denaturation

When the enzyme shape is permanently changed and its catalytic ability is destroyed.

Competitive Inhibition

When a foreign molecule blocks the enzyme's active site, preventing the substrate from binding.

Non-Competitive Inhibition

When a foreign molecule binds at the allosteric site, causing a change in the shape of the active site, thus preventing substrate binding.

Allosteric Site

A region of an enzyme away from the active site where a molecule can bind and cause a change in the shape of the active site.

Metabolic Pathway

A linked series of enzyme-catalyzed chemical reactions occurring within a cell. Can be linear or cyclical.

Autotrophs

Organisms that can produce their own food.

Photoautotrophs

Organisms that use the energy in light to create organic compounds they need to survive through photosynthesis (e.g., plants and cyanobacteria).

Chemoautotrophs

Organisms that derive energy from chemosynthesis, oxidizing inorganic substances like iron, sulfur or hydrogen sulfide (some bacteria, some archaea).

Heterotrophs

Organisms that capture the energy present in organic compounds by other organisms. They get their energy and matter by metabolizing the organic compounds in organisms that they eat, absorb, or the remains of other organisms.

Exergonic Reaction

Reactions that release energy and increase entropy.

Endergonic Reaction

Reactions that require energy and decrease entropy.

ATP

Adenosine Triphosphate - powers work within cells, composed of ribose, adenine, and three phosphate groups. Cells make their own and use it to store and release energy.

Energy Coupling

The linking of an exergonic reaction to an endergonic reaction, driving the endergonic reaction forward.

Photosynthesis

The process by which photoautotrophs combine carbon dioxide and water, using light energy, to create carbohydrates, releasing oxygen as a waste product.

Light Reactions

The first phase of photosynthesis, which converts light energy into the chemical energy of ATP and NADPH. Occurs in the thylakoids; oxygen is a waste product.

Calvin Cycle

The second phase of photosynthesis, which converts the chemical energy of NADPH and ATP into carbohydrate by fixing carbon dioxide. Occurs in the stroma.

Chlorophyll

The pigment that absorbs light energy in photosynthesis. Absorbs most energy in the blue and red parts of the spectrum, but very little in the green part of the spectrum.

Absorption Spectrum

A plot showing the amount of light absorbed at different light wavelengths by a pigment.

Action Spectrum

A plot showing how various light wavelengths drive photosynthesis. Blue and red wavelengths drive the most photosynthesis and green drives very little.

Chloroplast

The organelle where photosynthesis takes place, containing an outer membrane, inner membrane, DNA, ribosomes, thylakoids (containing photosystems and chlorophyll), grana, and stroma.

Photosystems

Complex assemblies of proteins within the thylakoid membrane that have embedded chlorophyll molecules, which convert light energy into a flow of electrons.

ATP Synthase

An enzyme and channel in the thylakoid membrane through which protons diffuse, generating ATP from ADP and phosphate.

Z Scheme

A graphical representation of everything that happens in the light reactions of photosynthesis, showing electron energy on the Y axis.

Carbon Fixation

The phase of the Calvin Cycle in which carbon dioxide gas is brought into the biosphere and combined with RuBP.

RuBisCO

The enzyme that catalyzes the carbon fixation phase by combining carbon dioxide with RuBP, possibly the most abundant protein on earth.

G3P/PGAL

Glyceraldehyde-3-phosphate/phosphoglyceraldehyde - a three-carbon molecule produced during the energy investment and harvest phase of the Calvin cycle that can be harvested to build plants.

Cellular Respiration

The process of converting glucose and oxygen into carbon dioxide, water, and ATP.

Glycolysis

The breakdown of glucose, occurring in the cytoplasm; an anaerobic process that results in the production of ATP and NADH and the end product is pyruvate.

Link Reaction

The process that transports pyruvate into the mitochondrial matrix where enzymes convert it to acetyl CoA, releasing CO2 and reducing NAD+ to NADH.

Krebs Cycle

A cyclical series of reactions occurring in the mitochondrial matrix that generate NADH, FADH2, and ATP, releasing CO2 as a byproduct.

Electron Transport Chain (ETC)

A series of membrane-embedded proteins in the mitochondrial inner membrane through which electrons flow, creating an electrical current that powers proton pumps.

Oxidative Phosphorylation

The ATP production based on enzymes and proteins along the mitochondrial membrane using the intermembrane space to create a chemiosmotic gradient.

Aerobic Respiration

The complete respiration process; oxygen is required and involves glycolysis, Krebs cycle, and the electron transport chain; generates a large amount of ATP.

Anaerobic Respiration

Respiration occurring without oxygen; involves glycolysis followed by fermentation; generates a small amount of ATP.

Brown Fat Cells

Cells in newborn and hibernating mammals that are extremely dense with mitochondria that generate heat via thermogenin or UCP.

Thermogenin/UCP

A protein channel in the inner mitochondrial membrane that allows protons to diffuse back to the matrix from the intermembrane space without passing through ATP synthase, generating heat instead of ATP.

Fermentation

Glycolysis followed by reactions that regenerate NAD+.

Alcohol Fermentation

Ethanol fermentation that occurs in yeast; enzymes remove a carbon dioxide from pyruvic acid, producing acetaldehyde, which is then reduced to ethanol; NADH is oxidized to NAD+ allowing glycolysis to continue.

Lactic Acid Fermentation

Occurs in muscle tissue under anaerobic conditions; pyruvate is reduced to lactic acid, and NADH is oxidized to NAD+ allowing glycolysis to continue.