BIOL 1308: Unit 2 Study Guide - Cellular Energy, Respiration, Photosynthesis, and the Cell Cycle

Comprehensive vocabulary flashcards covering bioenergetics, enzyme kinetics, cellular respiration, photosynthesis, and cell cycle regulation from the BIOL 1308 Unit 2 lecture notes.

Endergonic Reactions

Chemical reactions that require an input of energy to proceed and store energy within ordered molecular structures ("Energy Enters").

Endergonic Reaction Coordinate Diagram

A potential energy diagram showing that the products exist at a higher potential energy level than the reactants, requiring a net input of energy.

Exergonic Reactions

Chemical reactions that spontaneously release energy into the environment when they take place ("Energy Exits").

Exergonic Reaction Coordinate Diagram

A potential energy diagram showing that the reactants possess higher potential energy than the products, releasing a net quantity of energy.

Energetic Coupling

A cellular mechanism that occurs when the energy released from an exergonic pathway is directly harnessed to drive an endergonic pathway.

Catabolic Pathways

Metabolic pathways that break down complex organic molecules into simpler components.

Anabolic Pathways

Biosynthetic metabolic pathways that assemble large macromolecules from smaller building blocks.

Oxidation

The loss of electrons from a molecule, typically identified in biological systems by the removal of hydrogen atoms ("removing Hs").

Reduction

The gain of electrons and potential energy by a molecule, typically identified in biological systems by the addition of hydrogen atoms ("adding Hs").

Feedback Inhibition

A metabolic regulatory mechanism in which the final end-product of a multi-enzyme pathway binds as a non-competitive inhibitor to an early pathway enzyme, shutting it down when product levels accumulate.

First Law of Thermodynamics

The thermodynamic principle stating that energy cannot be created or destroyed, only converted or transformed from one form to another.

Second Law of Thermodynamics

The principle stating that energy transformations cannot occur without a loss of usable energy to the surroundings in the form of heat.

Activation Energy

The minimum initial input of energy required to start a chemical reaction.

Enzymatic Catalysis Reaction Profile

An energy coordinate diagram depicting activation energy without an enzyme ($a$), lowered activation energy in the presence of an enzyme ($b$), and the unchanged net energy difference between reactants and products ($c$).

Active Site

The specific pocket on an enzyme where starting reactant molecules (substrates) bind tightly to undergo chemical modification.

Enzyme-Substrate Complex Formation

The catalytic sequence in which a substrate enters an enzyme's active site, forms a temporary complex, and is converted into distinct products, leaving the enzyme unaltered.

Competitive Inhibition

A form of enzyme regulation where an inhibitory molecule binds directly to the active site, physically obstructing the substrate from entering.

Non-Competitive Inhibition

A form of enzyme regulation where an inhibitor binds to a separate allosteric site, altering the enzyme's conformation and deforming the active site.

Facultative Anaerobes

Organisms capable of switching between aerobic cellular respiration and fermentation depending on the availability of oxygen in their environment.

Autotrophs

"Self-feeders" that synthesize their own organic molecules from inorganic substances without consuming other living organisms.

Heterotrophs

"Different-feeders" that cannot synthesize their own food and must consume or absorb nutrients from external sources.

Glycolysis

The initial stage of cellular respiration occurring in the cytosol, converting one $6\text{-carbon}$ glucose into two $3\text{-carbon}$ pyruvates while yielding a net of $2\text{ ATP}$, $2\text{ NADH}$, and $2\text{ }H_2O$.

Phosphofructokinase (PFK)

The key regulatory enzyme at Step 3 of glycolysis that is allosterically inhibited when cellular $ATP$ levels are high.

Pyruvate Oxidation

The second stage of cellular respiration in the mitochondrial matrix where each pyruvate is cleaved into a $2\text{-carbon}$ acetyl group attached to Coenzyme A, yielding $2\text{ Acetyl-CoA}$, $2\text{ NADH}$, and $2\text{ }CO_2$ per glucose.

Citric Acid Cycle (Krebs Cycle)

An $8\text{-step}$ cyclical matrix pathway that fuses Acetyl-CoA to oxaloacetate, producing $6\text{ NADH}$, $2\text{ }FADH_2$, $2\text{ ATP}$, and $4\text{ }CO_2$ per glucose molecule.

Electron Transport Chain (ETC)

A series of inner mitochondrial membrane protein complexes ($\text{I, II, III, IV}$) that transfer electrons via redox reactions to actively pump $H^+$ out of the matrix and form a proton gradient.

Chemiosmosis

The diffusion of protons back into the mitochondrial matrix through the rotary channel of ATP Synthase, driving the mechanical formation of $ATP$ from $ADP$ and inorganic phosphate.

Anaerobic Respiration

A form of cellular respiration using a complete respiratory pathway (glycolysis, citric acid cycle, ETC) that utilizes an alternative electron acceptor such as $NO_3^-$ or $SO_4^{2-}$ instead of oxygen.

Fermentation

An anaerobic metabolic pathway that transfers electrons from $NADH$ to an organic byproduct to regenerate $NAD^+$, allowing glycolysis to continue producing $2\text{ ATP}$.

Lactic Acid Fermentation

A pathway in human muscle cells and certain bacteria where pyruvate is directly reduced by $NADH$ to form lactate and regenerate $NAD^+$.

Alcohol Fermentation

A pathway in yeast wherein pyruvate is cleaved into acetaldehyde (releasing $CO_2$), which is then reduced by $NADH$ to produce ethanol and regenerate $NAD^+$.

Photosystem II (PSII)

A protein-pigment complex in the thylakoid membrane that absorbs light energy to excite electrons and oxidizes water ($H_2O \rightarrow H^+ + O_2$), generating oxygen gas.

Photosystem I (PSI)

A thylakoid membrane complex that re-energizes electrons using light energy to drive the production of $NADPH$.

Calvin Cycle

The light-independent pathway occurring in the chloroplast stroma that fixes $CO_2$ using $ATP$ and $NADPH$ to synthesize glyceraldehyde-3-phosphate (G3P).

Rubisco

Ribulose 1,5-bisphosphate carboxylase/oxygenase; the stroma enzyme that catalyzes the attachment of $CO_2$ to ribulose 1,5-bisphosphate ($RuBP$) during carbon fixation.

Stomata

Microscopic pores on the leaf epidermis that allow $CO_2$ gas to enter the plant while permitting $O_2$ and water vapor to exit.

Thylakoids

Flattened, fluid-filled membranous sacs within chloroplasts arranged in stacks called grana, housing chlorophyll pigments and light-reaction complexes.

Stroma

The thick fluid-filled interior compartment of the chloroplast surrounding the thylakoids where the Calvin cycle reactions occur.

Homologous Chromosomes

A matched pair of chromosomes (one maternal, one paternal) sharing the same size, centromere position, and gene loci.

Sister Chromatids

Identical copies of a replicated chromosome joined together tightly at their centromere until pulled apart during cell division.

G1 Checkpoint (Restriction Point)

A primary cell cycle regulatory checkpoint that assesses cell size, nutrients, growth signals, and DNA damage (via proteins such as p53) before committing to DNA replication.

Proto-oncogenes

Normal genes that stimulate cell growth and division under tight regulatory control, which can become oncogenes when mutated.

Tumor Suppressor Genes

Genes that code for proteins that normally slow down cell division, repair damaged DNA, or induce apoptosis to prevent cancer formation.