BIOL 201 - Exam 2 (CHP 7)

Selective permeability

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

Phospholipid bilayer

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

Phospholipid

Amphipathic lipid with a hydrophilic head and two hydrophobic fatty acid tails.

Amphipathic

Having both hydrophilic and hydrophobic regions.

Hydrophilic

Water-attracting; interacts with water.

Hydrophobic

Water-repelling; does not interact favorably with water.

Fluid mosaic model

Membrane is a fluid phospholipid bilayer with various proteins embedded in it.

Cholesterol

Helps regulate membrane fluidity and stability in animal cells.

Membrane fluidity

Ability of membrane lipids and some proteins to move within the bilayer.

Integral proteins

Proteins embedded in the lipid bilayer, they penetrate hydrophobic core

Peripheral proteins

Proteins that are bound to surface of membrane.

Transmembrane proteins

Integral proteins that span completely across the membrane.

Transport proteins

Allow passage of hydrophilic substances across the membrane

Channel proteins (aquaporins)

Facilitate passage of water

Carrier proteins

bind to molecules & change shape to shuttle them across membrane

Aquaporins

Channel proteins that facilitate the movement of water across the membrane.

Gated channels

Ion channels that open or close in response to a stimulus.

Glycoproteins

Carbohydrate chain connected to proteins. Helps cell recognition

Glycolipids

Carbohydrate chain attached to a lipid. Helps with cell recognition

Diffusion

Net movement of molecules from an area of higher concentration to lower concentration.

Concentration gradient

Difference in the concentration of a substance between two areas.

Down the concentration gradient

Movement from high to low concentration.

Dynamic equilibrium

Molecules continue moving in both directions equally, with no net movement.

Passive transport

Movement of substances down their concentration gradient without cellular energy.

Simple diffusion

Movement of substances directly through the membrane without transport proteins or ATP.

Facilitated diffusion

Passive movement of substances down their gradient using channel or carrier proteins.

Osmosis

Diffusion of water across a selectively permeable membrane.

Tonicity

Ability of a surrounding solution to cause a cell to gain or lose water.

Hypertonic solution

Higher solute concentration than the cell; water moves out of the cell.

Hypotonic solution

Lower solute concentration than the cell; water moves into the cell.

Isotonic solution

Equal solute concentration; no net water movement.

Lysis

Bursting of an animal cell due to excessive water entering.

Shriveled cell

Animal cell that has lost water in a hypertonic solution.

Turgid

Firm plant cell swollen with water in a hypotonic environment.

Flaccid

Limp plant cell with reduced turgor pressure, commonly in an isotonic solution.

Plasmolysis

Plant cell membrane pulling away from the cell wall due to water loss.

Osmoregulation

Control of water balance within a cell or organism.

Contractile vacuole

Organelle that collects and expels excess water from certain protists.

Active transport

Movement of substances against their concentration gradient using energy.

Against the concentration gradient

Movement from low to high concentration.

ATP

Molecule that supplies energy for many cellular processes, including active transport.

Sodium-potassium pump

Membrane protein that uses ATP to move 3 Na+ out and 2 K+ into the cell.

Cotransport

Transport of one solute using energy stored in the gradient of another solute.

Proton pump

Transport protein that uses energy to move H+ ions across a membrane.

Bulk transport

Movement of large materials across the membrane using vesicles. requires energy

Vesicle

Small membrane-bound sac used to transport or store substances.

Exocytosis

Vesicles fuse with the plasma membrane and release materials outside the cell.

Endocytosis

Cell takes in substances by forming vesicles from its plasma membrane.

Phagocytosis

Cellular eating; cell engulfs large solid particles into vesicles.

Pinocytosis

Cellular drinking; cell takes in extracellular fluid and dissolved substances.

Receptor-mediated endocytosis

Selective uptake of molecules that bind to specific membrane receptors.

Ligand

Molecule that binds specifically to a receptor.

Passive vs. active transport

Passive: down gradient, no cellular ATP. Active: against gradient, requires energy.

Simple vs. facilitated diffusion

Simple: no protein needed. Facilitated: transport protein required.

Channel vs. carrier protein

Channel: passageway. Carrier: binds substance and changes shape.

Hypertonic vs. hypotonic

Hypertonic: water leaves cell. Hypotonic: water enters cell.

Exocytosis vs. endocytosis

Exocytosis: out. Endocytosis: in.

Phagocytosis vs. pinocytosis

Phagocytosis: large particles. Pinocytosis: extracellular fluid.

Saturated vs. unsaturated fatty acids

Saturated tails pack tightly; unsaturated tails have kinks and increase fluidity.