AP BIO UNIT 2

Cell Theory

All living things are made of cells; cells are the basic unit of life; all cells come from preexisting cells.

Prokaryotic Cell

Cell without a nucleus or membrane-bound organelles.

Eukaryotic Cell

Cell with a nucleus and membrane-bound organelles.

Nucleus

Contains DNA and controls gene expression.

Nuclear Envelope

Double membrane surrounding the nucleus; contains nuclear pores.

Nucleolus

Produces rRNA and assembles ribosomal subunits.

Ribosome

Makes proteins by translating mRNA.

Rough ER

Makes and begins processing proteins for secretion and membranes.

Smooth ER

Makes lipids, detoxifies chemicals, and stores calcium.

Golgi Apparatus

Modifies, sorts, and packages proteins and lipids.

Lysosome

Contains enzymes that digest macromolecules and worn-out cell parts.

Vacuole

Stores water, nutrients, and waste; the plant central vacuole maintains turgor.

Mitochondrion

Produces most ATP through cellular respiration.

Chloroplast

Performs photosynthesis in plants and algae.

Cytoskeleton

Protein-fiber network that supports cell shape, movement, and transport.

Microtubules

Cytoskeleton fibers involved in intracellular transport, cell division, cilia, and flagella.

Microfilaments

Actin fibers involved in cell movement, contraction, and shape changes.

Intermediate Filaments

Provide mechanical strength and help cells resist tension.

Cell Wall

Rigid outer layer that supports and protects plant cells.

Extracellular Matrix (ECM)

Network outside animal cells that provides support, attachment, and signaling.

Collagen

ECM protein that provides strength.

Integrin

Membrane protein that connects the ECM to the cytoskeleton.

Plasmodesmata

Channels through plant cell walls that connect neighboring cells.

Tight Junctions

Seal neighboring animal cells to prevent leakage between them.

Desmosomes

Anchor neighboring animal cells together and resist mechanical stress.

Gap Junctions

Channels that allow ions and small molecules to pass between animal cells.

Fluid Mosaic Model

Model describing a fluid phospholipid bilayer with embedded proteins and other molecules.

Phospholipid

Molecule with a hydrophilic head and hydrophobic fatty-acid tails.

Hydrophilic

Attracted to water; usually polar or charged.

Hydrophobic

Repelled by water; usually nonpolar.

Phospholipid Bilayer

Double layer of phospholipids forming the basic structure of cell membranes.

Amphipathic

Having both hydrophilic and hydrophobic regions.

Integral Membrane Protein

Protein embedded in the membrane; some span the entire bilayer.

Peripheral Membrane Protein

Protein attached to the surface of the membrane.

Cholesterol

Helps regulate membrane fluidity and stability in animal cells.

Glycoprotein

Protein with attached carbohydrate used in cell recognition and signaling.

Glycolipid

Lipid with attached carbohydrate involved in cell recognition.

Selective Permeability

Allows some substances to cross a membrane more easily than others.

Membrane Fluidity

Ability of membrane components to move laterally within the membrane.

Saturated Fatty Acid

Fatty acid without double bonds; straight tails pack tightly.

Unsaturated Fatty Acid

Fatty acid with double bonds that create kinks and prevent tight packing.

Membrane Adaptation to Cold

More unsaturated fatty acids help keep membranes fluid.

Membrane Adaptation to Heat

More saturated fatty acids help prevent membranes from becoming too fluid.

Diffusion

Net movement of particles from higher concentration to lower concentration.

Concentration Gradient

Difference in a substance's concentration between two regions.

Passive Transport

Movement down a gradient without direct energy input from the cell.

Simple Diffusion

Movement directly through the phospholipid bilayer without a transport protein.

Facilitated Diffusion

Passive movement across a membrane through a channel or carrier protein.

Channel Protein

Membrane protein that forms a passageway for specific substances.

Carrier Protein

Membrane protein that binds a substance and changes shape to transport it.

Aquaporin

Channel protein that allows water to cross a membrane quickly.

Osmosis

Net movement of water across a selectively permeable membrane toward lower water potential.

Water Potential (Ψ)

Potential energy of water that predicts the direction water moves.

Water Potential Equation

Ψ = Ψs + Ψp.

Solute Potential (Ψs)

Component of water potential affected by solute concentration; usually zero or negative.

Pressure Potential (Ψp)

Component of water potential caused by physical pressure.

Solute Potential Equation

Ψs = −iCRT; i is ionization constant, C is molarity, R is pressure constant, and T is kelvin temperature.

Water Movement

Water moves from higher water potential to lower water potential.

Hypotonic Solution

Solution outside the cell has lower solute concentration; water tends to enter the cell.

Isotonic Solution

Solution causes no net water movement and no sustained change in cell volume.

Hypertonic Solution

Solution outside the cell has higher effective solute concentration; water tends to leave the cell.

Hypoosmotic Solution

Solution has lower total solute concentration than the comparison solution.

Isoosmotic Solution

Solutions have equal total solute concentrations.

Hyperosmotic Solution

Solution has higher total solute concentration than the comparison solution.

Turgor Pressure

Pressure of cell contents against the plant cell wall due to water entering.

Turgid Plant Cell

Firm plant cell with high turgor pressure.

Flaccid Plant Cell

Limp plant cell with low turgor pressure.

Plasmolysis

Plant cell contents shrink away from the cell wall as water leaves.

Lysis

Bursting of a cell due to excessive water entry.

Animal Cell in Hypotonic Solution

Water enters; cell swells and may burst.

Animal Cell in Isotonic Solution

No net water movement; cell maintains its usual volume.

Animal Cell in Hypertonic Solution

Water leaves; cell shrivels.

Plant Cell in Hypotonic Solution

Water enters; cell becomes turgid.

Plant Cell in Isotonic Solution

Cell loses turgor and becomes flaccid.

Plant Cell in Hypertonic Solution

Water leaves; plasmolysis occurs.

Active Transport

Movement of substances against a concentration or electrochemical gradient using energy.

ATP Hydrolysis

Breakdown of ATP that releases usable energy for cellular work.

Protein Pump

Membrane protein that uses energy to move substances against their gradients.

Sodium-Potassium Pump

Uses one ATP to move 3 Na+ out and 2 K+ into an animal cell.

Proton Pump

Uses energy to move H+ across a membrane, creating a proton gradient.

Electrochemical Gradient

Combined effect of an ion's concentration difference and electrical charge difference.

Membrane Potential

Difference in electrical charge across a cell membrane.

Cotransport

Uses the gradient of one substance to drive the transport of another substance.

Sodium-Glucose Cotransporter

Uses Na+ moving down its gradient to help move glucose against its gradient.

Bulk Transport

Movement of large particles or quantities of material using membrane-bound vesicles.

Vesicle

Small membrane-bound sac that transports or stores substances.

Endocytosis

Cell takes in substances by forming a vesicle from its plasma membrane.

Exocytosis

Vesicle fuses with the plasma membrane and releases substances outside the cell.

Phagocytosis

Type of endocytosis that takes in large particles or whole cells.

Pinocytosis

Type of endocytosis that takes in extracellular fluid and dissolved substances.

Receptor-Mediated Endocytosis

Selective uptake of substances that bind to specific membrane receptors.

Endomembrane System

Network including the nuclear envelope, ER, Golgi, lysosomes, vesicles, and plasma membrane.

Protein Secretion Pathway

Ribosome on rough ER makes protein; ER and Golgi process it; vesicle carries it to the membrane for exocytosis.

Simple vs. Facilitated Diffusion

Simple diffusion crosses the bilayer directly; facilitated diffusion requires a transport protein. Both are passive.

Osmosis vs. Diffusion

Osmosis is specifically water movement across a selectively permeable membrane; diffusion applies to particles generally.

Osmosis vs. Tonicity

Osmosis is water movement; tonicity predicts a solution's effect on cell volume.

Which Molecules Cross the Bilayer Easily?

Small nonpolar molecules such as O2 and CO2.

Why Is Active Transport Important?

It maintains concentration gradients needed for cell function.

How Do Organelles Work Together to Secrete a Protein?

Rough ER makes it; transport vesicle carries it to Golgi; Golgi modifies and packages it; vesicle releases it by exocytosis.