Unit 2 Biology Review: Cell Membranes, Transport, Enzymes, Photosynthesis, and Cellular Respiration

Comprehensive practice vocabulary flashcards covering key definitions, structural components, and biological processes from Unit 2 Concept Review: cell membrane structure, passive and active transport, bulk transport, ATP energetics, enzymes, photosynthesis, and cellular respiration.

Fluid Mosaic Model

A model describing the plasma membrane structure as a mosaic of components, including phospholipids, cholesterol, proteins, and carbohydrates.

Amphipathic Molecule

A molecule possessing both hydrophilic (water-loving) and hydrophobic (water-fearing) regions, often described as 'dual loving,' such as a phospholipid.

Integral Membrane Protein

A protein that integrates completely into the structure of the cell membrane, spanning across the hydrophobic core of the phospholipid bilayer.

Peripheral Membrane Protein

A protein attached to the exterior or interior surfaces of the plasma membrane rather than embedded in the phospholipid bilayer.

Glycolipid

A lipid molecule that has a carbohydrate chain covalently attached, extending toward the extracellular surface for recognition and signaling.

Cholesterol (Membrane Function)

A lipid component of the plasma membrane that dampens and modulates the effects of temperature on membrane fluidity.

Selectively Permeable

A characteristic of biological membranes that allows only certain substances to pass through while preventing the passage of others.

Passive Transport

The movement of substances across a cell membrane from an area of higher concentration to an area of lower concentration without requiring cellular energy.

Concentration Gradient

A difference in the concentration of a chemical substance across a space or membrane, representing a form of potential energy.

Facilitated Transport

A type of passive transport in which substances diffuse down their concentration gradient across the membrane with the assistance of channel or carrier proteins.

Aquaporin

A specialized channel protein that facilitates the rapid passage and movement of water molecules across the cell membrane.

Osmosis

The net movement or diffusion of water molecules through a semipermeable membrane from an area of lower solute concentration to higher solute concentration.

Osmolarity

A measure of the total concentration of solute particles present in a given volume of solution.

Hypotonic Solution

A solution that has a lower solute concentration compared to the inside of the cell, causing net water movement into the cell.

Hypertonic Solution

A solution that has a higher solute concentration compared to the inside of the cell, resulting in net water movement out of the cell.

Isotonic Solution

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

Active Transport

The energy-requiring movement of substances across a cell membrane against their concentration or electrochemical gradient, typically powered by ATP.

Electrochemical Gradient

The combined gradient of concentration and electrical charge that affects an ion's movement across a cell membrane.

Sodium-Potassium Pump

An active transport carrier protein that pumps $Na^+$ out of the cell and $K^+$ into the cell, creating a charge imbalance that maintains membrane potential.

Endocytosis

A bulk transport process in which a cell takes in macromolecules or large particles by engulfing them in an invagination of the plasma membrane.

Phagocytosis

A form of bulk transport or endocytosis ('cellular eating') where large particles are taken in, often involving clathrin-coated vesicles.

Pinocytosis

A form of endocytosis ('cellular drinking') where extracellular fluids and dissolved solutes are taken into the cell via small vesicles.

Receptor-Mediated Endocytosis

A targeted bulk transport mechanism where specific extracellular substances bind to membrane receptor proteins before being internalized into coated pits.

Exocytosis

A bulk transport mechanism in which intracellular vesicles fuse with the plasma membrane to secrete substances and waste outside the cell.

Adenosine Triphosphate (ATP)

The primary energy-transfer molecule in living cells, composed of an adenine base, a ribose sugar, and three linked phosphate groups.

Catalyst (Enzyme)

A biological catalyst that accelerates chemical reactions in a cell by lowering activation energy, without being consumed or permanently altered in the reaction.

Activation Energy

The initial investment of energy required to start a chemical reaction, which enzymes lower to accelerate reaction rates.

Thylakoid

A flattened, membrane-bound sac inside chloroplasts containing chlorophyll, where the light-dependent reactions of photosynthesis take place.

Grana

Stacks of disc-shaped thylakoids located within the chloroplast.

Stroma

The fluid-filled internal space surrounding the thylakoids in chloroplasts, where the Calvin cycle (light-independent reactions) occurs.

Chlorophyll

The primary photosynthetic pigment in plants that absorbs solar energy and reflects green light, causing plant tissue to appear green.

Carotenoids

Accessory photosynthetic pigments that absorb light energy in wavelengths not captured efficiently by chlorophyll.

Light-Dependent Reactions

The stage of photosynthesis occurring in thylakoids that uses sunlight and $H_2O$ to generate chemical energy in the form of ATP and NADPH, releasing $O_2$ as a byproduct.

Calvin Cycle

The light-independent stage of photosynthesis occurring in the stroma, using $CO_2$, ATP, and NADPH to synthesize carbohydrate molecules such as G3P.

Cellular Respiration

The biochemical process by which cells break down organic compounds, particularly glucose, to harvest energy and produce ATP.

Glycolysis

The anaerobic first stage of cellular respiration occurring in the cytoplasm, breaking down one molecule of glucose into two molecules of pyruvate with a net gain of 2 ATP and 2 NADH.

Cristae

Folds of the inner mitochondrial membrane that provide an increased surface area for the complexes of the electron transport chain.

Mitochondrial Matrix

The gel-like internal fluid of the mitochondrion containing enzymes where the preparatory stage and the citric acid cycle take place.

Citric Acid Cycle

The aerobic mitochondrial stage of cellular respiration that completes the oxidation of acetyl-CoA, producing $CO_2$, ATP, NADH, and $FADH_2$.

Electron Transport Chain (ETC)

A sequence of electron carrier proteins located along the cristae of mitochondria that transfers electrons from NADH and $FADH_2$ to $O_2$, creating a proton gradient that drives ATP synthesis.

Fermentation

An anaerobic pathway occurring in the cytoplasm that allows cells to generate ATP through glycolysis when oxygen is absent.