Lecture Slides Ch.5-8 Exam Review: Cell Transport, Metabolism, Photosynthesis, and Cellular Respiration

Comprehensive vocabulary flashcards covering cell transport, bioenergetics and enzyme kinetics, photosynthesis, and cellular respiration review topics from Chapters 5 through 8.

Selective Permeability

The property of the plasma membrane that allows certain substances to cross more easily than others while blocking the passage of other molecules.

Fluid Mosaic Model

The structural model of the cell membrane describing it as a dynamic mosaic of diverse protein molecules embedded in or attached to a fluid bilayer of phospholipids.

Phospholipid

An amphipathic lipid molecule consisting of a hydrophilic glycerol-and-phosphate head and two hydrophobic fatty acid tails, forming the structural foundation of biological membranes.

Osmosis

The passive diffusion of free water across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Hypertonic Solution

An extracellular environment with a higher solute concentration than the cell's interior, causing water to leave the cell and resulting in cell shrinkage or crenation.

Hypotonic Solution

An extracellular environment with a lower solute concentration than the cell's cytoplasm; placing red blood cells (RBCs) into pure water causes water influx, swelling, and lysis.

Isotonic Solution

A solution whose solute concentration is equal to that of the inside of the cell, resulting in no net movement of water across the plasma membrane.

Channel Proteins

Transmembrane transport proteins that provide hydrophilic tunnels allowing specific polar molecules or ions (such as water through aquaporins) to pass rapidly through the hydrophobic bilayer.

Facilitated Transport

A type of passive transport where polar molecules and ions move down their concentration gradient with the assistance of transmembrane channel or carrier proteins without requiring energy.

Active Transport

The movement of a substance across a biological membrane against its concentration or electrochemical gradient, requiring transport proteins and the expenditure of cellular energy ($\text{ATP}$).

Sodium-Potassium Pump

An electrogenic active transport protein that uses the hydrolysis of one $\text{ATP}$ molecule to pump three sodium ions ($3\,Na^+$) out of the cell and two potassium ions ($2\,K^+$) into the cell.

Bulk Transport

The active mechanism by which large particles or macromolecules are transported across the plasma membrane packaged inside vesicles.

Exocytosis

A form of bulk transport in which intracellular vesicles fuse with the plasma membrane to discharge their contents (such as hormones or neurotransmitters) into the extracellular space.

Endocytosis

A cellular bulk transport process in which the plasma membrane invaginates and pinches inward to form new vesicles, engulfing external matter into the cell.

Metabolism

The totality of an organism's chemical reactions, consisting of anabolic and catabolic pathways that manage the energy and material resources of the cell.

Anabolic Pathway

A metabolic pathway that consumes energy to synthesize complex molecules from simpler ones, such as building sugars during photosynthesis.

Catabolic Pathway

A metabolic pathway that releases energy by breaking down complex molecules into simpler compounds, such as the degradation of glucose during cellular respiration.

Kinetic Energy

The form of energy associated with the relative motion of objects, molecules, or particles.

Potential Energy

The stored energy that matter possesses because of its location, arrangement, or spatial position, including the chemical energy stored in molecular bonds.

Gibbs Free Energy Formula

The thermodynamic equation $\Delta G = \Delta H - T\Delta S$ that measures the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system.

Negative Gibbs Free Energy ($-\Delta G$)

A thermodynamic condition indicating that a reaction is exergonic, releases free energy into the surroundings, and can proceed spontaneously.

Positive Gibbs Free Energy ($+\Delta G$)

A thermodynamic condition indicating that a reaction is endergonic, requires a net input of free energy, and is non-spontaneous.

Activation Energy

The initial amount of energy needed to start a chemical reaction by contorting the reactant molecules so that their chemical bonds can break.

Enzyme

A biological macromolecule (typically a protein) that acts as a catalyst, speeding up a specific chemical reaction by lowering its activation energy barrier without being consumed.

Induced Fit

The conformational change in the shape of an enzyme's active site that occurs upon substrate binding to envelop the substrate more snugly and optimize catalysis.

Competitive Inhibitor

A molecule that reduces enzyme activity by binding directly to the enzyme's active site, competing with the substrate for access.

Allosteric Inhibition

The non-competitive reduction of enzyme activity that occurs when an inhibitor binds to a regulatory site outside the active site, inducing a conformational change that lowers catalytic efficiency.

Feedback Inhibition

A regulatory mechanism in which the final end product of a metabolic pathway allosterically inhibits an enzyme that acts early in the pathway, preventing overaccumulation of the product.

First Law of Thermodynamics

The principle of conservation of energy stating that energy can be transferred and transformed, but it cannot be created or destroyed.

Second Law of Thermodynamics

The physical law stating that every spontaneous energy transfer or transformation increases the entropy (disorder) of the universe.

Photosynthesis

The anabolic process occurring in chloroplasts that converts solar energy into chemical energy stored in carbohydrates, represented by $6CO_2 + 6H_2O + \text{light} \rightarrow C_6H_{12}O_6 + 6O_2$.

Autotrophs

Self-feeding organisms that sustain themselves without consuming organic material from other living beings by producing organic molecules from inorganic substances like $CO_2$.

Chemoautotrophs

Organisms that synthesize organic molecules using chemical energy extracted from the oxidation of inorganic compounds (such as hydrogen sulfide) rather than sunlight.

Stomata

Microscopic pores on leaf surfaces flanked by guard cells that open and close to facilitate the exchange of $CO_2$ and $O_2$ while regulating transpiration of water.

Chlorophyll

The green photosynthetic pigment situated in thylakoid membranes that absorbs violet-blue and red light while transmitting and reflecting green light.

Thylakoid

A flattened, fluid-filled membranous sac inside chloroplasts whose membranes host the light-dependent reactions, chlorophyll pigments, and electron transport chains.

Light Reactions

The initial phase of photosynthesis occurring in the thylakoid membranes that splits $H_2O$, releases $O_2$, and converts solar energy into chemical energy in the form of $\text{ATP}$ and $\text{NADPH}$.

Calvin Cycle (Dark Reactions)

The light-independent metabolic pathway occurring in the chloroplast stroma that fixes carbon dioxide into carbohydrates using the $\text{ATP}$ and $\text{NADPH}$ generated by the light reactions.

Rubisco

The primary enzyme of the Calvin cycle (ribulose-1,5-bisphosphate carboxylase-oxygenase) that catalyzes the fixation of $CO_2$ onto ribulose bisphosphate (RuBP).

Glyceraldehyde-3-Phosphate (G3P)

The three-carbon carbohydrate that is the direct output of the Calvin cycle, requiring three complete turns of the cycle fixing three $CO_2$ molecules to produce one net molecule.

C3 Plants

Plants that fix carbon directly through rubisco into a three-carbon compound (3-PGA), showing reduced photosynthetic efficiency in hot, dry environments due to photorespiration.

C4 Plants

Plants that minimize photorespiration by spatially separating the initial fixation of carbon into a four-carbon compound in mesophyll cells from the Calvin cycle in bundle-sheath cells.

CAM Plants

Arid-adapted plants that temporally separate carbon fixation by opening their stomata at night to store carbon as organic acids, closing stomata during the day while running the Calvin cycle.

Cellular Respiration

The catabolic pathway by which organic molecules (primarily glucose) are broken down to generate $\text{ATP}$, represented by $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP}$.

Glycolysis

The anaerobic metabolic pathway occurring in the cytoplasm that splits one molecule of glucose into two pyruvate molecules, producing a net yield of $2\,\text{ATP}$ and $2\,\text{NADH}$.

Citric Acid Cycle (Krebs Cycle)

An eight-step cyclic pathway in the mitochondrial matrix that oxidizes acetyl-CoA, producing $CO_2$, $1\,\text{ATP}$ (or GTP), $3\,\text{NADH}$, and $1\,\text{FADH}_2$ per turn.

Substrate-Level Phosphorylation

The direct enzymatic formation of $\text{ATP}$ by transferring a phosphate group from an organic substrate intermediate to $\text{ADP}$, occurring during glycolysis and the citric acid cycle.

Oxidative Phosphorylation

The production of $\text{ATP}$ driven by the redox reactions of the electron transport chain and chemiosmosis across the inner mitochondrial membrane, requiring oxygen as the terminal electron acceptor.

Redox Reactions

Paired chemical reactions involving the transfer of electrons, where oxidation is the loss of electrons and reduction is the gain of electrons.

NADH and FADH2

Coenzyme electron carriers that become reduced by capturing high-energy electrons during cellular respiration and deliver them to the electron transport chain.

Alcohol Fermentation

An anaerobic catabolic pathway utilized by yeast in the absence of oxygen that converts pyruvate into ethanol and $CO_2$ to regenerate $NAD^+$ for glycolysis.

Glucose-6-Phosphate

The phosphorylated sugar intermediate produced in the first step of glycolysis whose accumulation exerts negative feedback inhibition on the enzyme hexokinase.