Exam 2 Study Guide Flashcards

A collection of vocabulary flashcards covering transmembrane gradients, cellular metabolism, enzymatic regulation, cellular respiration (aerobic and anaerobic), and stages of photosynthesis including C3, C4, and CAM pathways.

Transmembrane Gradient

Higher concentration of a solute on one side of the plasma membrane than the other.

Electrochemical Gradient

A dual gradient containing both an electrical gradient (charge difference) and a chemical gradient (concentration difference).

Tonicity

How an extracellular solution affects a cell's volume via osmosis.

Osmosis

Diffusion of water through a selectively permeable membrane.

Isotonic

A type of tonicity with equal solute concentrations where the cell maintains a normal shape.

Hypertonic

A type of tonicity with a higher concentration of solute outside the cell; results in water exiting the cell, causing animal cells to shrink and plant cell plasma membranes to pull away from the cell wall.

Hypotonic

A type of tonicity with lower solute concentration outside the cell; results in water entering the cell, causing Osmotic Lysis (swelling/bursting) in animals and a Turgid state in plants.

Membrane Channels

Form an open passageway for direct/rapid diffusion of specific solutes across the membrane; can be open or closed.

Carriers (Transporters)

Proteins that bind solute in a specific hydrophilic pocket, undergo a conformational change, and release the solute on the opposite side.

Conformational Change

A change in the shape of a macromolecule.

Active Transport

Moves solute against their gradient (LOW to HIGH); it is energetically unfavorable and requires work.

Primary Active Transport

Uses a pump that directly hydrolyzes ATP to move a solute AGAINST its gradient.

Secondary Active Transport

Uses a pre-existing electrochemical gradient (created by primary active transport) to DRIVE the cotransport of another solute.

Cotransport

Occurs when active transport of a solute indirectly drives the transport of other substances.

Exocytosis

Process where cargo is packed into a vesicle by the Golgi Apparatus, the protein coat sheds, and the vesicle fuses with the plasma membrane to release cargo.

Endocytosis

The process of bringing substances into the cell, divided into Phagocytosis, Pinocytosis, and Receptor-Mediated Endocytosis.

Phagocytosis

Known as "cell eating"; pseudopodia engulf large particles or microorganisms into a large food vacuole (phagosome).

Pinocytosis

Known as "cell drinking"; the non-specific internalization of extracellular fluid and dissolved solutes into small vesicles.

Receptor-Mediated Endocytosis

Process where cargo binds to highly specific cell-surface receptors, leading to the formation of a coated vesicle and internalization.

Kinetic Energy

Energy associated with movement; includes thermal, motion, light, and sound.

Potential Energy

Energy due to structure, position, or location; includes gravitational energy and chemical energy stored in molecular bonds.

First Law of Thermodynamics

Energy cannot be created or destroyed.

Nonpolar Bonds

Bonds with equal electron sharing where electrons are far from the nuclei; they are the longest, weakest, and have the highest potential energy.

Polar Bonds

Bonds with unequal electron sharing where electrons are closer to electronegative nuclei; they are the shortest, strongest, and have the lowest potential energy.

Enthalpy (H)

The total heat content of a system, accounting for internal potential energy within molecular bonds and the effect on pressure and volume.

Endothermic

A reaction where $\text{ΔH} > 0$; heat is taken up by the system FROM the surroundings, and products have higher potential energy than reactants.

Exothermic

A reaction where $\text{ΔH} < 0$; heat energy is RELEASED into the surroundings, and products have LOWER potential energy than reactants.

Entropy (S)

A measure of a system's molecular disorder or randomness.

Gibbs Free Energy

A calculation that combines enthalpy, entropy, and absolute temperature (K) to determine whether a reaction can proceed.

Spontaneous Reactions

Thermodynamically favored reactions where $\text{ΔG} < 0$. This does NOT mean they happen quickly.

Exergonic Reactions

Chemical reactions that release free energy into the system and naturally favor product formation.

Nonspontaneous Reactions

Thermodynamically unfavorable reactions where $\text{ΔG} > 0$, requiring a constant input of free energy to occur.

Equilibrium

State where $\text{ΔG} = 0$ and the forward and reverse reaction rates are perfectly balanced.

Energetic Coupling

A process where energy released from an exergonic reaction (commonly hydrolysis of ATP) is used to drive an endergonic reaction.

ATP (Adenosine Triphosphate)

The primary chemical energy currency used for energetic coupling.

Hydrolysis of ATP

The conversion of ATP to ADP and $\text{Pi}$ through water cleaving the covalent bond of the outermost organic phosphate group.

Substrate-Level Phosphorylation

Direct ATP synthesis where an enzyme cleaves a phosphate group off a high-energy organic substrate molecule and adds it to ADP.

Oxidative Phosphorylation

Indirect ATP synthesis using an electron transport chain (ETC) to build a proton gradient that drives ATP Synthase to create ATP.

Phosphorylation

The use of a kinase and ATP to add a phosphate group to a target molecule, increasing its potential energy or altering its shape.

Substrate

The reactant on which an enzyme works.

Activation Energy

The initial kinetic energy barrier required to stretch and strain chemical bonds to reach an unstable transition state.

Enzymatic Catalysis

The process where enzymes speed up reactions by binding substrates at the active site via induced fit, lowering the activation energy.

Cofactors

Reversible inorganic mineral ions that stabilize electron charges in the active site.

Coenzymes

Organic molecules that physically carry functional groups or electrons for an enzyme.

Prosthetic Groups

Non-amino acid structural molecules that are permanently covalently bound directly to an enzyme.

Vmax

The absolute maximum velocity a reaction can reach when every available active site is completely saturated.

Competitive Inhibition

Occurs when a structural mimic of a substrate binds directly to the active site, physically blocking the real substrate.

Allosteric (Noncompetitive) Inhibition

Occurs when an inhibitor binds to an allosteric site (separate regulatory pocket), causing a shape change that deforms the active site.

Metabolic Pathways

Interconnected, step-by-step chemical assembly lines where the product of one enzyme becomes the substrate for the next.

Catabolic Pathways

Exergonic pathways that break down complex organic molecules into simpler pieces, releasing energy to synthesize ATP and reduce electron carriers.

Anabolic Pathways (Biosynthetic Pathways)

Endergonic pathways that assemble large macromolecules from small building blocks, consuming cellular ATP and electron carriers.

Redox Reactions

Coupled chemical processes that transfer high-energy electrons between molecules (Reduction and Oxidation).

Oxidation

The exergonic loss of electrons; for example, when carbon in glucose loses electrons by removing hydrogens.

Reduction

The endergonic gain of electrons and potential energy; for example, when oxygen gains electrons by adding hydrogen.

Biological Electron Carriers

Specialized coenzymes like $\text{NAD}^{+}$ and FAD that act as temporary high-energy electron shuttles.

Feedback Inhibition

A metabolic regulation loop where the final end-product of a pathway acts as an allosteric inhibitor against the beginning enzymes.

Cellular Respiration Reaction

$$\text{C}_{6}\text{H}_{12}\text{O}_{6} + 6\text{O}_{2} \rightarrow 6\text{CO}_{2} + 6\text{H}_{2}\text{O} + \text{Energy (30-32 ATP)}$$

Glycolysis

Occurs in the cytosol; takes glucose as input and produces 2 pyruvate, a net of 2 ATP, and 2 NADH.

Phosphofructokinase

The rate-limiting enzyme in glycolysis.

Pyruvate Oxidation

Occurs in the mitochondrial matrix; takes 2 pyruvate and produces 2 NADH, 2 $\text{CO}_{2}$, and 2 Acetyl-CoA.

Citric Acid Cycle

An 8-step cyclical pathway in the mitochondrial matrix that releases 4 $\text{CO}_{2}$ and produces 6 NADH, 2 $\text{FADH}_{2}$, and 2 ATP per 2 Acetyl-CoA.

Electron Transport Chain (ETC)

Multi-protein complexes (I, II, III, IV) in the inner mitochondrial membrane that use electron energy to pump $\text{H}^{+}$ ions into the intermembrane space.

Terminal Electron Acceptor

$\text{O}_{2}$; it sits at the bottom of the ETC, pulling electrons through and binding to protons to form $\text{H}_{2}\text{O}$.

ATP Synthase Complex

A complex where the physical flow of protons causes subunits to spin, creating rotational kinetic energy that forces the synthesis of ATP from ADP and $\text{Pi}$.

Anaerobic Respiration

Used by certain prokaryotes in low-oxygen environments; uses a highly electronegative molecule like Nitrate or Sulfate as the terminal electron acceptor.

Fermentation

A process consisting of glycolysis only; it lacks a terminal electron acceptor for the ETC and regens oxidized $\text{NAD}^{+}$ by dumping electrons into an organic waste molecule.

Lactic Acid Fermentation

Occurs in human muscle cells; pyruvate directly accepts electrons from NADH to produce Lactate and recycle $\text{NAD}^{+}$.

Alcohol Fermentation

Occurs in yeast; pyruvate is converted to Acetaldehyde, which accepts electrons from NADH to produce Ethanol and recycle $\text{NAD}^{+}$.

Photoautotrophs

A subtype of autotroph (green plants, algae, cyanobacteria) that uses sunlight to manufacture carbohydrates.

Photosynthesis Equation

$$\text{CO}_{2} + \text{H}_{2}\text{O} + \text{Light energy} \rightarrow (\text{CH}_{2}\text{O})_{n} + \text{O}_{2}$$

Light Reactions

Occur in the thylakoid membrane; use light and $\text{H}_{2}\text{O}$ to produce ATP, NADPH, and $\text{O}_{2}$.

Calvin Cycle

Occurs in the stroma; uses $\text{CO}_{2}$, ATP, and NADPH to produce carbohydrates.

Stomata

Pores on the leaf surface flanked by guard cells through which $\text{CO}_{2}$ enters and $\text{O}_{2}$ and water vapor exit.

Thylakoids

Third membrane in chloroplasts forming flattened, fluid-filled sacs that house chlorophyll pigments and the ETC.

Granum

A stack of thylakoids; plural is grana.

Chlorophylls

Light-absorbing pigments containing a porphyrin ring with a Magnesium ion ($\text{Mg}^{2+}$) at the center.

Carotenoids / Xanthophylls

Pigments that absorb wavelengths chlorophyll cannot and act as antioxidants to protect chlorophyll from free radical damage.

Absorption Spectrum

The specific wavelengths absorbed by an individual pigment.

Action Spectrum

The overall rate of photosynthesis by the whole plant at different wavelengths.

Photophosphorylation

The process in light reactions where ATP synthase produces ATP in the stroma, driven by the $\text{H}^{+}$ gradient created by splitting water and ETC pumping.

Cyclic Electron Flow

Occurs when a plant needs extra ATP but no NADPH; electrons from PSI cycle back through the cytochrome complex to power the $\text{H}^{+}$ pump.

Rubisco

The enzyme that catalyzes carbon fixation by combining $\text{CO}_{2}$ with the 5-carbon sugar RuBP.

G3P (Glyceraldehyde-3-phosphate)

The direct carbohydrate product of the Calvin Cycle.

Photorespiration

A wasteful reaction where rubisco attaches oxygen instead of carbon dioxide to RuBP, occurring when internal leaf conditions have low $\text{CO}_{2}$ and high $\text{O}_{2}$.

C3 Plants

Plants that fix $\text{CO}_{2}$ directly into 3PG using rubisco inside mesophyll cells; they suffer heavily from photorespiration in hot/dry conditions.

C4 Plants

Plants that bypass photorespiration by physically separating CO2 capture (in mesophyll cells using PEP carboxylase) and the Calvin Cycle (in bundle-sheath cells).

CAM Plants

Plants that use temporal separation to bypass photorespiration; they open stomata at night to fix $\text{CO}_{2}$ into organic acids and close them during the day to feed the Calvin Cycle.