AP®︎ Biology: Unit 2 Flashcards
Master key terms and definitions for Unit 2 of AP Biology – Cell Structure and Function to help you prep for quizzes and the AP exam.
Nucleus and Nuclear Envelope
The DNA-containing control center enclosed by a double membrane with pores continuous with the ER.
The DNA-containing control center enclosed by a double membrane with pores continuous with the ER.
Nonmembranous rRNA-protein complexes that translate mRNA sequences into polypeptides.
Free make cytosolic proteins; bound on rough ER make secreted or membrane proteins.
A network of membranes that modifies, packages, and transports proteins, lipids, and polysaccharides.
Small membrane sacs that move materials between organelles in the endomembrane system.
Prokaryotes lack membrane-bound organelles and a nucleus; eukaryotes contain both.
Plant cells have cell walls and chloroplasts; animal cells lack them and typically have centrioles.
The amount of membrane surface available for exchange relative to internal cell volume.
Sphere: SA 4πr², V 4/3πr³; cube: SA 6s², V s³; rectangular solid: SA 2lh+2lw+2wh, V lwh; cylinder: SA 2πr²+2πrl, V πr²l.
Find surface area and volume with the correct formula, then divide surface area by volume.
Higher ratios allow faster nutrient uptake, waste removal, and chemical exchange across membranes.
Folds increase surface area greatly without much increase in volume.
Thin extensions of root epidermal cells that increase surface area for water and mineral absorption.
Paired cells regulate stomatal openings, controlling gas exchange and water loss in leaves.
Intestinal lining cells have membrane projections that increase surface area for nutrient absorption.
Short hairlike cell projections that increase exposed surface and help move materials past cells.
Smaller bodies lose heat faster because they have more surface area relative to volume.
Smaller multicellular organisms usually use energy faster per gram than larger organisms.
As cells grow, volume increases faster than membrane area, limiting efficient material exchange.
Integral proteins penetrate the bilayer; peripheral proteins attach loosely to the membrane surface.
A steroid in animal membranes that stabilizes the bilayer and buffers fluidity changes.
Higher temperature and unsaturated tails increase fluidity; cholesterol buffers fluidity across temperatures.
Phospholipids have hydrophilic phosphate heads and hydrophobic fatty acid tails.
Embedded or attached proteins have hydrophobic regions in the bilayer and hydrophilic regions exposed to water.
Carbohydrate-tagged membrane molecules form an outer coat used for recognition, adhesion, and protection.
Fatty acid tails with double bonds create kinks that increase membrane fluidity.
Straight fatty acid tails pack tightly together and decrease membrane fluidity.
The selectively permeable boundary of the cell, consisting of a phospholipid bilayer with embedded components, that separates internal conditions from the external environment and regulates transport.
A double layer of amphipathic phospholipids with hydrophilic heads facing outward and hydrophobic tails inward, creating a hydrophobic interior that contributes to selective permeability.
A dynamic membrane model describing a fluid phospholipid bilayer with mobile embedded proteins and other components forming a flexible mosaic.
A rigid outer layer that supports cells, limits some substances, and prevents osmotic lysis.
A difference in a substance's concentration across space or across a membrane.
Small nonpolar cross freely; water crosses slowly or via aquaporins; large polar molecules and ions need proteins.
Rigid outer layer that provides support and filtering, while the plasma membrane remains the selective barrier.
Energy-requiring vesicle transport moves materials into cells by endocytosis and out by exocytosis.
The membrane property that allows some substances to cross more easily than others; small nonpolar molecules cross more readily than polar molecules and ions.
Membrane proteins such as channels, carriers, and pumps that move specific substances across the bilayer.
Passive movement of polar molecules or ions through membrane proteins down their concentration gradient.
Large polar molecules cannot pass easily through the bilayer and move through transport proteins.
Simple diffusion crosses the bilayer directly; facilitated diffusion uses proteins, but both move down gradients.
Membrane proteins that form hydrophilic pathways allowing specific ions or other hydrophilic substances to cross the membrane; channels function in passive transport.
Movement of substances across membranes down their concentration gradient without direct energy input.
Channel proteins that allow rapid movement of large quantities of water across cell membranes.
Hypotonic has lower solute, hypertonic has higher solute, and isotonic has equal solute relative to another solution.
The effect of dissolved solutes on water potential; it is always zero or negative.
Solute potential equals negative iCRT: Ψs = -iCRT.
The total concentration of dissolved solute particles in a solution.
The control of internal water balance and solute concentration to maintain homeostasis.
An organelle in many freshwater protists that pumps out excess water entering by osmosis.
The shrinking of a plant cell's membrane away from the wall after water loss.
Lysis is bursting from water gain; crenation is shrinking from water loss in animal cells.
The potential energy of water, equal to pressure potential plus solute potential.
Physical pressure raises water potential; in plants, this pressure against the wall is turgor.
Water moves from areas of higher water potential to lower water potential.
The passive diffusion of water across a selectively permeable membrane toward the side with higher solute concentration, or lower water potential.
The relative solute concentration of one solution compared with another across a selectively permeable membrane, determining water movement.
A difference in a substance's concentration across space or across a membrane that drives net movement from high to low concentration.
A large plant cell vacuole that stores water and other materials and helps maintain turgor pressure.
ATP is split into ADP and phosphate, releasing energy that powers membrane pumps.
Selective transmembrane proteins bind specific solutes and change shape to move them across membranes.
An enzyme that hydrolyzes ATP to provide energy for cellular processes such as ion pumping.
A combined difference in ion concentration and electrical charge across a membrane.
The voltage difference across a membrane caused by unequal ion distribution on each side.
Movement of substances across a membrane using energy, often ATP, against their concentration gradient.
An ATP-powered membrane protein (Na+/K+-ATPase) that pumps 3 Na+ out of the cell and 2 K+ into the cell against their gradients, helping maintain membrane potential.
The voltage difference across a membrane caused by an unequal distribution of electrical charge and ions on each side of the membrane.
A stack of membranous sacs that modifies, sorts, folds, and packages cellular products into vesicles.
A double-membraned organelle that carries out cellular respiration and produces most cellular ATP.
An acidic membrane-bound sac containing hydrolytic enzymes that digest macromolecules, waste, and worn-out cell parts and recycle cell components.
A membrane network in which rough ER synthesizes and processes proteins, while smooth ER synthesizes lipids, detoxifies, and stores calcium; it also helps transport materials within the cell.
A membrane-bound storage compartment for water, ions, nutrients, wastes, and other materials; in plants, the large central vacuole also helps maintain turgor pressure.
Prokaryotes lack most membrane-bound organelles and internal membrane compartments, while eukaryotes use membrane-bound organelles to separate specialized functions.
Specialized eukaryotic structures enclosed by membranes that isolate specific cellular processes, metabolic reactions, and conditions.
A double-membraned organelle with pores that stores DNA and separates transcription from translation.
A membrane-bound organelle that breaks down fatty acids and detoxifies harmful compounds using oxidative enzymes.
Specific membranes contain particular enzymes, receptors, and transport proteins matched to specialized functions.
The mitochondrion is a double-membraned organelle whose folded inner membrane, called cristae, increases surface area for ATP-producing reactions.
Organization of a cell into specialized regions, often membrane-bound, that separate reactions and can increase surface area for cellular processes.
Evolutionary process in which one free-living prokaryote began living inside another cell permanently.
Mitochondria and chloroplasts have double membranes, circular DNA, and prokaryote-like ribosomes.
Protein-lined openings in the nuclear envelope that regulate movement between nucleus and cytoplasm.
Organelles maintain distinct pH and ion conditions so specific enzymes work optimally.
Internal folding and extra membranes provide more space for enzymes and transport proteins.
Different reactions occur in different compartments, preventing interference between incompatible activities.
Non-membrane-bound areas in prokaryotes perform specific functions despite lacking true organelles.
RNA is translated while it is still being transcribed because no nucleus separates the processes.
A double-membraned photosynthetic organelle in plants and algae whose internal membranes carry out photosynthesis; it also contains circular DNA and prokaryote-like ribosomes.
