Cellular Energetics, Metabolism, and Respiration

Vocabulary flashcards covering bioenergetics, thermodynamics, ATP reactions, enzyme inhibition, glycolysis, and respiration pathways.

ADP

Adenosine diphosphate; a lower energy molecule consisting of an adenine base, a ribose sugar, and two phosphate groups.

Anabolic

A metabolic pathway that requires the consumption of energy to build complex molecules from simpler ones (e.g., photosynthesis, where glucose is created).

Anabolism

A process that combines small, simpler molecules into larger complex structures and consumes energy.

Anaerobic Respiration

Fermentation; the process of breaking down glucose partially without oxygen, taking place only in the cytoplasm (occurs in human muscle cells).

ATP

Adenosine triphosphate; a molecule composed of adenine (nitrogenous base), ribose (five-carbon sugar), and a phosphate group chain of $3$. Cells use $10,000,000$ molecules of ATP per second.

Aerobic Respiration

The default metabolic pathway that requires oxygen, taking place in the mitochondria and cytoplasm to break down glucose into usable energy, producing $36$ ATP ($\text{Glucose} + \text{oxygen} \rightarrow \text{carbon dioxide}$; includes glycolysis).

Autotrophs

Self-feeders that produce their own food (e.g., plants).

Allosteric Inhibition

Inhibition occurring when an inhibitor binds to an enzyme, inducing a conformational change that reduces enzyme activity.

Bioenergetics

The flow of energy through life, based on the principle that life is built on chemical reactions.

Carbon Dioxide

$CO_2$; a product of aerobic respiration and alcoholic fermentation.

Catabolic

A pathway where complex molecules release energy as they break down into simpler ones (e.g., cellular respiration, where glucose is broken down).

Catabolism

The metabolic breakdown of large complex molecules into smaller usable units, releasing energy.

Cellular Respiration

A catabolic, oxygen-requiring process that uses energy to produce ATP, $CO_2$, and water, existing in two forms: anaerobic and aerobic.

Citric Acid Cycle

A closed loop metabolic cycle that takes place in the mitochondria of eukaryotic cells.

Competitive Inhibition

Inhibition in which an inhibitor molecule binds directly to the active site and blocks the substrate, competing with the substrate for binding.

Dehydration

An endergonic reaction where water is removed and phosphate is added, resulting in energy being absorbed.

Endergonic Reaction

A chemical reaction that absorbs energy (e.g., photosynthesis).

Exergonic Reaction

A chemical reaction that releases energy (e.g., cellular respiration).

Energy

The ability to do work.

Energy Release

The reaction $ATP \rightarrow ADP$, which releases energy from chemical bonds.

Energy Storage

The reaction $ADP \rightarrow ATP$, storing energy in chemical bonds.

Enzymes

Molecules that catalyze biochemical reactions and speed up reactions; most are proteins.

Fermentation Alcoholic

A fermentation process used by unicellular yeast and bacteria that produces alcohol and $CO_2$.

Fermentation Lactic Acid

A fermentation process used by animals and some bacteria (both multicellular and unicellular), summarized as: $\text{Pyruvic acid} + NADH \rightarrow \text{lactic acid} + NAD^+$.

Glucose

$C_6H_{12}O_6$; a simple sugar broken down during cellular metabolism.

Glycolysis

"Sugar cutting"; the first step in the breakdown of glucose into three-carbon molecules to extract energy for cellular metabolism, occurring in the cytoplasm to produce pyruvate and pyruvic acid with a net gain of $2$ ATP.

Heterotrophs

"Other feeders" that consume food (e.g., animals).

Hydrolysis

An exergonic reaction that breaks bonds of ATP to release energy, in which water is added and phosphate is removed.

Kinetic Energy

The energy of motion (e.g., light and heat).

Metabolism

The sum total of all chemical reactions that take place inside cells.

NAD

An electron carrier analogized to a drained battery; very powerful but highly specific.

NADH

A high-energy molecule specific to and utilized during aerobic respiration; analogized to a charged battery that powers specific proteins in mitochondria to make large amounts of ATP.

Noncompetitive Inhibition

An inhibition mechanism where an inhibitor molecule binds to the enzyme at an allosteric site ("allosteric sit"), preventing substrate binding to the active site.

Oxygen Gas

$O_2$; required for aerobic cellular respiration.

Oxygen Phosphorylation

The production of ATP driven by the transfer of electrons down the electron transport chain to create a proton gradient.

Potential Energy

Energy of position, stored in chemical bonds.

Pyruvate

A central hub in cellular metabolism that participates in both anaerobic and aerobic respiration.

Substrate

A molecule on which an enzyme acts.

Thermodynamics

The study of the relationships between heat, energy, and work.

Exothermic / Exergonic Reaction

A catabolic reaction characterized by an initial activation energy requirement followed by the release of energy from chemical bonds to do work, resulting in products with lower energy than reactants.

Endergonic Reaction

An anabolic reaction that requires an energy input and absorbs energy into chemical bonds, resulting in products with higher energy than reactants.