AP Biology Unit 2: Cell Structure & Function Vocabulary

Vocabulary flashcards generated from AP Biology Unit 2 notes, covering cell structure, organelle functions, membrane transport, evolutionary theories, and osmotic relationships.

Prokaryotic Cell

A single-celled organism, such as bacteria or archaea, characterized by having no nucleus, DNA localized in an unbound nucleoid region, a single circular chromosome, and no membrane-bound organelles.

Eukaryotic Cell

A complex cell type containing membrane-bound organelles that compartmentalize cellular functions, multiple linear chromosomes contained within a membrane-bound nucleus, and the capacity to form unicellular or multicellular organisms.

Nucleoid

The unbound region inside a prokaryotic cell that contains its single circular chromosome.

Surface Area-to-Volume Ratio (SA:V)

The mathematical relationship between a cell's outer plasma membrane surface area and its internal volume; a higher ratio increases the efficiency of diffusion and material exchange with the environment.

Cristae

Infoldings of the inner mitochondrial membrane that maximize surface area for enzymes synthesizing ATP during cellular respiration.

Nucleus

The organelle in eukaryotic cells enclosed by a double membrane (nuclear envelope) that stores the majority of the cell's genetic material (DNA).

Chromatin

The loose, uncoiled complex of DNA and histone proteins present in eukaryotic cells during interphase before condensing into distinct chromosomes.

Nuclear Envelope

A double membrane structure consisting of two lipid bilayers perforated by pore complexes that encloses the nucleus and regulates molecular transport between the nucleus and cytoplasm.

Nuclear Lamina

A netlike array of protein filaments lining the inner surface of the nuclear envelope that maintains the structural shape of the nucleus.

Nucleolus

A specialized structure located within the nucleus responsible for the synthesis of ribosomal RNA (rRNA).

Ribosomes

Non-membrane-bound complexes composed of ribosomal RNA (rRNA) and protein found in all cells that carry out protein synthesis.

Free Ribosomes

Ribosomes suspended in the cytosol that synthesize proteins intended for functioning inside the cytosol.

Bound Ribosomes

Ribosomes attached to the exterior of the rough endoplasmic reticulum that synthesize proteins destined for insertion into membranes, organelle packaging, or secretion outside the cell.

Mitochondria

Double-membrane-bound eukaryotic organelles where cellular respiration takes place, using oxygen to convert chemical energy from fuels into ATP.

Chloroplasts

Double-membrane photosynthetic organelles found in plant and algal cells that convert solar light energy into chemical energy stored in sugar molecules.

Thylakoids

Flattened membranous sacs inside chloroplasts stacked into grana that contain chlorophyll and carry out photosynthetic light conversion.

Stroma

The fluid contained within the inner membrane of a chloroplast surrounding the thylakoid membrane system.

Infolding Hypothesis

The evolutionary hypothesis stating that internal eukaryotic membranes (including the nucleus, ER, and Golgi) originated from inward foldings of the ancestral prokaryotic plasma membrane around genetic material.

Endosymbiotic Theory

The evolutionary theory asserting that eukaryotic energy-converting organelles (mitochondria and chloroplasts) originated when an ancestral host eukaryotic cell engulfed free-living aerobic and photosynthetic prokaryotes.

Endomembrane System

A group of membrane-bound organelles in eukaryotic cells (including the nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane) that work together to synthesize, modify, package, and transport cellular products.

Smooth Endoplasmic Reticulum

A region of the endoplasmic reticulum lacking ribosomes that synthesizes lipids, metabolizes carbohydrates, detoxifies drugs and poisons, and stores calcium ions.

Rough Endoplasmic Reticulum

A region of the endoplasmic reticulum studded with bound ribosomes that folds and processes proteins, initiates protein glycosylation, and manufactures membrane components.

Protein Glycosylation

A post-translational modification beginning in the rough ER where carbohydrate chains are covalently linked to proteins to create glycoproteins.

Golgi Apparatus

An organelle composed of flattened membranous sacs (cisternae) that chemically modifies, sorts, adds carbohydrate identification tags, and packages proteins from the ER into transport vesicles.

Cis Face

The receiving face of the Golgi apparatus located near the endoplasmic reticulum that receives transport vesicles.

Trans Face

The shipping face of the Golgi apparatus that pinches off vesicles to dispatch molecules to other sites or the plasma membrane.

Lysosome

A membranous sac filled with hydrolytic digestive enzymes maintained at an acidic pH that degrades macromolecules, foreign particles, and worn-out organelles.

Autophagy

The metabolic process in which a lysosome fuses with damaged cellular organelles or macromolecules to recycle their chemical components.

Apoptosis

Programmed cell death occurring when lysosomal membranes rupture, releasing hydrolytic enzymes into the cytosol to systematically degrade a damaged or mutated cell.

Central Vacuole

A large organelle found in mature plant cells that stores water, nutrients, and ions while generating turgor pressure against the cell wall.

Fluid Mosaic Model

A structural model describing the plasma membrane as a flexible two-dimensional fluid matrix composed of phospholipids, embedded proteins, cholesterol, and carbohydrates moving laterally.

Amphipathic

Describing a molecule that contains both hydrophilic (polar) and hydrophobic (nonpolar) regions, such as phospholipids and integral membrane proteins.

Integral Proteins

Transmembrane proteins that penetrate and span the hydrophobic core of the plasma membrane lipid bilayer.

Peripheral Proteins

Non-amphipathic membrane proteins loosely attached to the exterior or interior surface of the plasma membrane via hydrophilic interactions.

Aquaporins

Specialized transmembrane channel proteins that facilitate the rapid bulk diffusion of water molecules across the cell membrane.

Passive Transport

The movement of substances across a biological membrane down their concentration gradient (from high to low concentration) without direct expenditure of metabolic energy (ATP).

Facilitated Diffusion

The passive transport of molecules or ions across a membrane down their concentration gradient assisted by specific transmembrane channel or carrier proteins.

Osmosis

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

Tonicity

The ability of an extracellular solution to cause a cell to gain or lose water by osmotic flow.

Hypertonic Solution

A solution with a higher concentration of solutes compared to the inside of a cell, causing water to leave the cell via osmosis.

Hypotonic Solution

A solution with a lower concentration of solutes compared to the inside of a cell, causing water to enter the cell via osmosis.

Isotonic Solution

A solution containing an equal concentration of solutes compared to the interior of a cell, resulting in no net movement of water across the membrane.

Plasmolysis

A process in plant cells placed in a hypertonic environment where the cytoplasm loses water and shrinks, causing the plasma membrane to pull away from the cell wall.

Turgor Pressure

The hydrostatic force exerted by the fluid inside the central vacuole pushing outward against the rigid cell wall of a plant cell.

Water Potential ($\Psi$)

A physical quantity measured in bars that quantifies the tendency of water molecules to move from one area to another based on solute concentration and physical pressure.

Solute Potential Formula

The formula used to calculate solute potential: $\Psi_s = -iCRT$, where $i$ is the ionization constant, $C$ is molar concentration in $\text{moles/liter}$, $R$ is the pressure constant ($0.0831\,\text{L}\cdot\text{bar}/\text{mol}\cdot\text{K}$), and $T$ is absolute temperature in Kelvin ($\text{K} = {^\circ}\text{C} + 273$).