General Biology Review: Cell Transport, Biomolecules, Enzymes, ATP, and Photosynthesis

Comprehensive vocabulary flashcards covering cell membrane transport, biomolecules, enzyme kinetics, cellular energy (ATP/ADP), and photosynthetic pathways.

Selective Permeability

The property of the cell membrane that allows some substances to cross more easily than others, enabling the cell to regulate its internal conditions.

Fluid Mosaic Model

A model describing the cell membrane as a flexible phospholipid bilayer containing various proteins and other molecules that can move laterally within the layer.

Membrane Cholesterol

A steroid lipid found in many animal cell membranes that helps regulate fluidity and stability by preventing phospholipids from packing too tightly or moving too freely.

Homeostasis

The maintenance of relatively stable internal conditions within a cell or organism despite changes in the surrounding external environment.

Passive Transport

The movement of substances across a cell membrane down their concentration gradient without the direct expenditure of cellular energy ($\text{ATP}$).

Facilitated Diffusion

A form of passive transport that moves substances down their concentration gradient through channel proteins or carrier proteins that span the membrane.

Osmosis

The net movement of water across a selectively permeable membrane toward the region with a higher effective solute concentration.

Hypotonic Solution

A solution having a lower solute concentration than the inside of a cell, causing water to enter and potentially swell an animal cell.

Hypertonic Solution

A solution having a higher solute concentration than the inside of a cell, causing net water loss and cell shrinkage.

Plasmolysis

The condition in plant cells where excessive water loss causes the plasma membrane to pull away from the rigid cell wall.

Active Transport

The energy-requiring movement of substances across a membrane against their concentration or electrochemical gradient using specialized carrier proteins or pumps.

Sodium-Potassium Pump

An active transport carrier protein in animal cells that consumes $\text{ATP}$ to maintain steep concentration gradients of sodium and potassium ions across the membrane.

Endocytosis

A bulk transport process in which the cell membrane invaginates around external material to form an intracellular vesicle.

Exocytosis

A bulk transport mechanism where an intracellular vesicle fuses with the cell membrane to discharge its contents outside the cell.

Phagocytosis

A specialized form of endocytosis that involves the cellular uptake and engulfment of relatively large solid particles.

Pinocytosis

A type of endocytosis where the cell non-specifically samples fluid and dissolved solutes from the extracellular environment.

Receptor-Mediated Endocytosis

A targeted bulk transport mechanism that utilizes specific membrane receptor proteins to bind and ingest selected molecules.

Monomer

A small molecular subunit that can covalently link with other similar subunits to form larger, complex macromolecules.

Polymer

A large biomolecule composed of repeating or linked smaller monomer units bonded together.

Glycogen

A heavily branched storage polysaccharide composed of glucose units, found primarily in animal liver and muscle tissue as well as fungi.

Cellulose

A structural polysaccharide forming plant cell walls that cannot be digested by human digestive enzymes and serves as dietary fiber.

Chitin

A tough structural polysaccharide that provides rigidity and protection in fungal cell walls and arthropod exoskeletons.

Triglycerides

A major class of storage lipids composed of a single glycerol backbone attached to three fatty acid chains.

Saturated Fatty Acid

A fatty acid hydrocarbon chain containing only single carbon-carbon bonds, maximizing hydrogen atoms and packing tightly together.

Unsaturated Fatty Acid

A fatty acid containing one or more carbon-carbon double bonds, which introduces bends or kinks that reduce packing density.

Peptide Bond

The covalent chemical bond formed between the amino group of one amino acid and the carboxyl group of another during protein synthesis.

Quaternary Protein Structure

The highest level of protein structure, resulting from the spatial association and assembly of two or more distinct polypeptide chains.

Nucleotide

The monomer building block of nucleic acids, consisting of a nitrogen-containing base, a five-carbon sugar, and a phosphate group.

Enzyme

A biological catalyst (most often a protein) that speeds up chemical reactions by lowering the activation energy without being consumed.

Activation Energy

The threshold input of energy required to bring reactants to a transition state so that a chemical reaction can proceed.

Active Site

The specific region or pocket of an enzyme molecule that binds the substrate and carries out catalysis.

Induced-Fit Model

A model describing how an enzyme's active site alters its conformation slightly upon substrate binding to optimize catalysis.

Competitive Inhibition

A mechanism of enzyme regulation where an inhibitor directly competes with the native substrate for occupancy of the active site.

Noncompetitive Inhibition

Inhibition in which an inhibitor binds to a distinct site on an enzyme other than the active site, inducing a conformational change that lowers catalytic efficiency.

Denaturation

A destructive change in a protein's three-dimensional conformation caused by extreme temperatures or pH changes, rendering it nonfunctional.

Catalase

An enzyme present in plant and animal tissues (such as potatoes) that catalyzes the breakdown of toxic hydrogen peroxide into water and oxygen gas.

Adenosine Triphosphate (ATP)

The primary cellular energy carrier consisting of adenine, a ribose sugar, and three linked phosphate groups.

ATP Hydrolysis

The exergonic reaction represented by $\text{ATP} + \text{H}_2\text{O} \rightarrow \text{ADP} + \text{inorganic phosphate} + \text{usable free energy}$, used by cells to drive endergonic work.

Chemical Work

A category of cellular work driven by $\text{ATP}$, such as synthesizing proteins, $\text{DNA}$, and other complex polymers from smaller precursors.

Photosynthesis

The biological process converting light energy into stored chemical energy, summarized by the equation $6\text{CO}_2 + 6\text{H}_2\text{O} \xrightarrow{\text{light energy}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$.

Thylakoid

A flattened, membrane-bound sac inside a chloroplast containing chlorophyll and electron transport proteins; the site of the light-dependent reactions.

Granum

A stacked column of thylakoid membranes within the chloroplast stroma that maximizes surface area for photosynthetic reactions.

Chlorophyll

The primary green photosynthetic pigment that absorbs blue-violet and red wavelengths of visible light and reflects green light.

Photolysis

The enzymatic splitting of water molecules in Photosystem II that supplies replacement electrons and releases oxygen gas ($\text{O}_2$) as a by-product.

Photophosphorylation

The synthesis of $\text{ATP}$ from $\text{ADP}$ and inorganic phosphate driven by a proton gradient established across the thylakoid membrane during the light reactions.

Principle of Limiting Factors

The ecological and physiological law stating that the overall rate of a process is constrained by the essential variable that is in shortest supply.

Stomata

Microscopic pores on plant epidermal surfaces controlled by guard cells that permit $\text{CO}_2$ entry and regulate the release of water vapor and $\text{O}_2$.

CAM Plants

Plants adapted to arid conditions (such as cacti) that open stomata at night to fix $\text{CO}_2$ into organic acids and keep them closed during hot days to conserve water.

Photoautotroph

An organism, such as a green plant or photosynthetic bacterium, that synthesizes organic molecules from inorganic carbon sources utilizing light energy.

Calvin Cycle

The light-independent cyclic pathway occurring in the chloroplast stroma that incorporates inorganic $\text{CO}_2$ into organic triose phosphate sugars using $\text{ATP}$ and $\text{NADPH}$.

Rubisco

Ribulose-1,5-bisphosphate carboxylase/oxygenase; the key stroma enzyme that catalyzes the attachment of $\text{CO}_2$ to RuBP during carbon fixation.

Ribulose Bisphosphate (RuBP)

A five-carbon sugar molecule that serves as the carbon dioxide acceptor during the fixation phase of the Calvin cycle.

3-Phosphoglycerate (3-PGA)

The stable three-carbon organic intermediate formed when the unstable six-carbon compound produced by Rubisco splits during carbon fixation.

Glyceraldehyde-3-Phosphate (G3P)

A three-carbon sugar phosphate synthesized during the reduction stage of the Calvin cycle, used to regenerate RuBP and build glucose.

Calvin Cycle Net Stoichiometry

The energetic requirement to produce one net $\text{G3P}$ ($3\,\text{CO}_2$, $9\,\text{ATP}$, and $6\,\text{NADPH}$) or two net $\text{G3P}$ for one glucose ($6\,\text{CO}_2$, $18\,\text{ATP}$, and $12\,\text{NADPH}$).