AP Biology Unit 2: Cell Structure and Function

Comprehensive vocabulary flashcards covering cell structure, membrane transport, organelle function, and cell compartmentalization based on Unit 2 AP Biology lecture notes.

Ribosomes

Non-membrane, subcellular structures composed of ribosomal RNA (rRNA) and protein that synthesize proteins according to messenger RNA (mRNA) sequences, reflecting common ancestry in all known life.

Endomembrane System

A group of membrane-bound organelles and subcellular components (endoplasmic reticulum, Golgi complex, lysosomes, vacuoles, transport vesicles, nuclear envelope, and plasma membrane) that work together to modify, package, and transport polysaccharides, lipids, and proteins intercellularly.

Rough Endoplasmic Reticulum (Rough ER)

A cellular structure associated with membrane-bound ribosomes that allows for the compartmentalization of cells and helps carry out protein synthesis.

Smooth Endoplasmic Reticulum (Smooth ER)

A membrane-bound organelle whose cellular functions include detoxification of cells and lipid synthesis.

Golgi Complex

A membrane-bound organelle consisting of a series of flattened membrane sacs responsible for correctly folding and chemically modifying newly synthesized cellular products and packaging proteins for trafficking.

Mitochondria

Double-membraned organelles involved in aerobic cellular respiration that possess a smooth outer membrane and a highly convoluted inner membrane forming folds to facilitate more efficient ATP synthesis.

Lysosomes

Membrane-enclosed sacs containing hydrolytic enzymes that digest material and play a key role in programmed cell death (apoptosis).

Vacuoles

Membrane-bound sacs that perform storage roles; in plant cells, a specialized large vacuole maintains turgor pressure through nutrient and water storage, whereas animal cells contain smaller, more numerous vacuoles.

Chloroplasts

Specialized double-membrane organelles found in plants and photosynthetic algae that serve as the site for photosynthesis.

Surface Area-to-Volume Ratio

A physical ratio that affects a cell's ability to exchange chemicals and energy with the environment; smaller cells exhibit a higher ratio, allowing for more efficient material exchange.

Fluid Mosaic Model

A model describing the plasma membrane framework composed of phospholipid molecules embedded with proteins, steroids (such as cholesterol), glycoproteins, and glycolipids that can move around within the membrane.

Phospholipids

Amphipathic molecules forming a membrane bilayer with polar hydrophilic phosphate heads oriented toward aqueous environments and nonpolar hydrophobic fatty acid regions facing inward.

Selective Permeability

The characteristic of the plasma membrane caused by its hydrophobic interior, allowing small nonpolar molecules ($N_2$, $O_2$, $CO_2$) to pass freely while restricting large polar molecules and ions.

Cell Wall

A structural boundary found in Bacteria, Archaea, Fungi, and plants that provides protection from osmotic lysis and acts as a permeability barrier for certain substances.

Passive Transport

The net movement of molecules from regions of high concentration to regions of low concentration across a membrane without the direct input of metabolic energy.

Active Transport

The movement of molecules or ions across a membrane that requires the direct input of metabolic energy (such as ATP), often moving substances from low to high concentration.

Endocytosis

An energy-requiring cellular transport process where the plasma membrane folds inward to form vesicles that engulf large molecules or particulate matter from the external environment.

Exocytosis

An energy-requiring cellular transport process where internal vesicles fuse with the plasma membrane to secrete large molecules out of the cell.

Facilitated Diffusion

Passive transport requiring embedded transport or channel proteins to enable the movement of charged ions (such as $Na^+$ and $K^+$) and polar substances across the membrane.

Aquaporins

Membrane channel proteins specialized for transporting large quantities of water ($H_2O$) across biological membranes.

Osmosis

The net diffusion of water across a membrane from regions of high water potential (low solute concentration/osmolarity) to regions of low water potential (high solute concentration/osmolarity).

Hypotonic

An external environment possessing a lower solute concentration (or lower osmolarity) compared to the internal environment of a cell.

Hypertonic

An external environment possessing a higher solute concentration (or higher osmolarity) compared to the internal environment of a cell.

Osmoregulation

A biological process that maintains water balance and allows organisms to control their internal solute composition and water potential.

$Na^+/K^+$ Pump

A membrane ATPase protein that uses metabolic energy (ATP) for the active transport of sodium ($Na^+$) and potassium ($K^+$) ions to establish and maintain electrochemical gradients.

Cell Compartmentalization

The use of internal membranes and membrane-bound organelles in eukaryotic cells to isolate specific enzymatic reactions, minimize competing interactions, and increase surface area for reactions.

Endosymbiosis

The evolutionary process by which membrane-bound eukaryotic organelles, such as mitochondria and chloroplasts, evolved from once free-living prokaryotic cells.