Bioenergetics Flashcards

A set of 50 vocabulary flashcards covering bioenergetics, redox reactions, ATP structure, metabolism, photosynthesis, and cellular respiration.

Bioenergetics

The transformation and management of energy in living organisms that makes life possible.

Energy

The capacity required to perform heavy labor and exercise, as well as both the synthesis and breakdown of molecules.

Oxidation

The removal of an electron from a compound.

Reduction

The addition of an electron to a compound.

Redox Reactions

Chemical reactions involving oxidation-reduction, where electrons are transferred from a reducing agent to an oxidizing agent.

Reducing Agent

The electron donor in a redox reaction that loses electrons and becomes oxidized.

Oxidizing Agent

The electron acceptor in a redox reaction that gains electrons and becomes reduced.

ATP (Adenosine Triphosphate)

The energy currency of the cell consisting of an adenine base, a ribose sugar, and three phosphate groups.

Adenine

A nitrogenous base component attached to ribose in an ATP molecule.

Ribose

A 5-carbon sugar component that links the adenine base to the phosphate groups in ATP.

Phosphoanhydride Bonds

High-energy chemical bonds connecting the adjacent phosphate groups of an ATP molecule.

Hydrolysis of ATP

A reversible reaction where water splits ATP, breaking a terminal high-energy phosphate bond to produce $ADP$, an inorganic phosphate ion ($P_i$), and free energy.

ADP (Adenosine Diphosphate)

The molecule formed when ATP loses its terminal phosphate group during energy release.

Inorganic Phosphate ($P_i$)

The free phosphate group released upon ATP hydrolysis, which often binds to and activates another molecule.

Phosphorylation

The addition of a phosphate group to a protein or molecule, often inducing a conformational change or activating it.

Dephosphorylation

The removal of a phosphate group from a protein or molecule, returning it to its original conformation.

Sodium-Potassium Pump Cycle

An active transport process where ATP phosphorylates a membrane carrier to pump $Na^+$ out and dephosphorylation allows $K^+$ to diffuse into the cell.

Metabolism

The sum of all the chemical activities taking place within an organism.

Catabolism

The metabolic pathway in which larger molecules are broken down into smaller ones, releasing energy that may be temporarily stored as ATP.

Anabolism

The metabolic pathway in which complex molecules are synthesized from simpler substances, absorbing energy and storing it in chemical bonds.

Acetyl-CoA

A crucial intermediate molecule in carbohydrate and lipid metabolism that delivers acetyl groups to the Krebs cycle for oxidation.

Photosynthesis

An anabolic process by which plants, algae, and some bacteria convert light energy, carbon dioxide, and water into organic sugars and oxygen.

Chloroplast

A double-membrane organelle containing thylakoids, grana, and stroma that serves as the site of photosynthesis.

Thylakoid

Disc-shaped membrane-bound structures inside chloroplasts where chlorophyll pigments absorb light and light-dependent reactions occur.

Stroma

The fluid-filled intracellular space of the chloroplast surrounding the thylakoid stacks where light-independent reactions take place.

Granum

A stacked structure composed of multiple disc-shaped thylakoids within a chloroplast.

Chlorophyll

The primary light-absorbing pigment in photosynthetic organisms that becomes energized upon absorbing solar energy.

General Formula of Photosynthesis

The chemical equation represented by $6\,CO_2 + 12\,H_2O \rightarrow C_6H_{12}O_6 + 6\,O_2 + 6\,H_2O$ driven by light, pigments, and enzymes.

Light-Dependent Reactions

Photosynthetic processes occurring in the thylakoid membrane that convert light and water into stored chemical energy ($ATP$ and $NADPH$), producing oxygen.

Thylakoid Lumen

The inner space of the thylakoid where water splitting occurs and protons accumulate to build a gradient during light reactions.

Light-Independent Reactions (Calvin Cycle)

Photosynthetic processes occurring in the stroma that use $ATP$ and $NADPH$ to convert carbon dioxide into glucose.

Photosystem II (PSII / P680)

A membrane protein complex absorbing light at $680\,nm$ that initiates photosynthetic electron transport and splits water molecules.

Photosystem I (PSI / P700)

A membrane protein complex absorbing light at $700\,nm$ that uses excited electrons to aid in reducing $NADP^+$ to $NADPH$.

Plastoquinone (PQ)

An electron carrier in the thylakoid membrane that transfers electrons from PSII to the cytochrome $b_6f$ complex.

Cytochrome $b_6f$ Complex

A protein complex in photosynthetic electron transport that transfers electrons and pumps protons ($H^+$) into the thylakoid lumen.

Plastocyanin (PC)

A mobile electron carrier protein that transports electrons from cytochrome $b_6f$ to PSI.

Ferredoxin (Fd)

An iron-sulfur protein that carries electrons from PSI to FNR during the light reactions.

Ferredoxin-NADP Reductase (FNR)

An enzyme that receives electrons from ferredoxin to synthesize $NADPH$ from $NADP^+$ and $H^+$.

ATP Synthase

A complex membrane enzyme that uses the kinetic energy of a proton gradient to synthesize $ATP$ from $ADP$ and $P_i$.

Carbon Fixation

The first stage of the Calvin Cycle where $CO_2$ from the atmosphere is attached to a 5-carbon compound (RuBP) by the enzyme Rubisco.

RuBP (Ribulose 1,5-bisphosphate)

A 5-carbon compound in the stroma that combines with carbon dioxide at the beginning of the Calvin Cycle.

Rubisco

The enzyme that catalyzes the combination of carbon dioxide with RuBP during carbon fixation.

3-PGA (3-Phosphoglycerate)

A 3-carbon intermediate molecule produced during the carbon fixation stage of the Calvin Cycle.

G3P (Glyceraldehyde 3-phosphate)

A 3-carbon sugar produced during the reduction stage of the Calvin Cycle, used to assemble glucose and regenerate RuBP.

Cellular Respiration

A catabolic pathway described by $C_6H_{12}O_6 + 6\,O_2 \rightarrow 6\,CO_2 + 6\,H_2O + ATP$, where organisms extract energy from organic fuel.

Glycolysis

The first stage of cellular respiration occurring in the cytosol where glucose is split into 2 pyruvate molecules, producing net $2\,ATP$ and $2\,NADH$.

Krebs Cycle

The second stage of cellular respiration in the mitochondrion where acetyl-CoA is oxidized, producing $2\,ATP$, $6\,NADH$, and $2\,FADH_2$.

Electron Transport Chain and Oxidative Phosphorylation

The final stage of cellular respiration in the mitochondrion that uses electrons from $NADH$ and $FADH_2$ to generate about $34\,ATP$.

Substrate-Level Phosphorylation

A direct method of generating $ATP$ during glycolysis ($2\,ATP$) and the Krebs cycle ($2\,ATP$).

Proton Gradient ($H^+$ Gradient)

An accumulation of hydrogen ions across a membrane established by electron transfer energy, driving ATP synthesis for cellular work.