AP Biology Chp. 36 Pearson

Different sides of protein anchors

*hydrophobic side* anchors proteins in the membrane *hydrophilic side* extends into cytosol & extracellular matrix

List six functions of membrane proteins

*transport* proteins span membrane & transport w/ hydrophilic channels or by changing shape *enzymatic activity* built into membrane, enzyme w/ active site exposed & substances in adj. solution can form metabolic pathway *signal transduction* binding site for chemical messenger that gives signals to cell *cell-cell recognition* glycoproteins serve as ID *intercellular joining* membrane proteins of adj. cells hook together forming gap or tight junctions *attaching to cytoskeleton & ECM*

Transport protein

A membrane protein, specifically a transport protein, that has a hydrophilic channel that certain molecules or atomic ions use as a tunnel.

How does water move?

From areas of higher water potential to areas of lower water potential (moves to more negative potential) Pure water has a potential of 0

Sodium-potassium pump

a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell.

Phagocytosis

a cell engulfs a particle by extending a pseudopodia around it and packaging it in a vacuole

Lysed

a cell that has burst from H2O on the inside

Selective permeable membrane

a membrane that allows some substances to cross it more easily than others

Turgid

a really tight cell wall, the pressure causes plants to stand up

Concentration gradient

a region along which the density of a chemical substance increases or decreases

Cotransport

a transport protein couples with the "downhill" diffusion of the solute to the "uphill" transport of a second substance against its own concentration gradient

Proton pump

actively transports protons (hydrogen ions) out of the cell

Ligand

any molecule that binds specifically to a receptor site on another molecule

How does cholesterol affect membrane fluidity?

at high temperature cholesterol makes the membrane less fluid by restoring phospholipid movement. It also lowers the temperature for the membrane to solidify

Flacid

balanced with less pressure

Plasmolyzed

cell lost so much H2O that cell membrane shrinks away from the cell wall

Water balance difference for cells with and without cell walls.

cells with cell walls have isotonic environment; there is no net movement of cells across the plasma membrane. Cells without cell walls can't tolerate excessive loss or uptake of water

Ion channels

channel proteins that transport ions

Pressure potential

determined by pressure exerted on cell wall, pushing force, positive #

Solute potential

determined by solute concentration (force of osmosis) pulling force, negative #

Isotonic

equal concentrations on both sides

Passive transport

high to low concentration, no ATP from the cell required

Hypertonic

higher concentration of solute

Gated channels

ion channels that open or close in response to stimulus

Why is selective permeability important for cells?

it allows cells to live by maintaining homeostasis and prevents harmful chemicals from entering and good ones from leaving

How does increasing the number of saturated hydrocarbon tails affect membrane fluidity?

it makes the membrane less fluid because they are closely packed together

Active transport

low to high concentration, requires ATP

Hypotonic

lower concentration of solute

How does decreasing temperature affect membrane fluidity?

membrane remains fluid until the phospholipids settle into a closely packed arrangement and the membrane soldifies

Membrane sidedness

membranes have distinct inside and outside faces, the lipid bilayers differ in composition and each protein has directional orientation in the membrane

Membrane carbohydrates

play a key role in cell-cell recognition, important in organ and tissue development, and basis for rejection of foreign cells by immune cells

Aquaporins

protein channels allowing the rapid flow of water across the cell membrane

How are ligands related to receptor-mediated endocytosis

provides the receptor sites for ligands and allows the cell to acquire bulk quantities of a specific substance

Receptor-mediated endocytosis

specialized type of pinocytosis that lets the cell acquire bulk quantities of specific substances using proteins with receptor sites in the plasma membrane

Pinocytosis

the cell continuously "gulps" droplets of extracellular fluid into tiny vesicles formed by infolding the plasma membrane

Electrochemical gradient

the combination of chemical and electric forces acting on an ion

Osmosis

the diffusion of free water across a selectively permeable membrane (high to low)

Water potential

the force responsible for movement of water in a system, equal to solute potential + pressure potential

How does free water concentration drive osmosis?

the free water concentration controls where the water goes because it moves to lower concentrations of free water, causing it to pass into the cells and through the cell membrane

How do phospholipids with unsaturated hydrocarbon chains affect membrane fluidity?

the kinks in the tails of unsaturated hydrocarbons don't allow them to pack together as closely as saturated fats, making them more fluid

Diffusion

the movement of particles of any substance so that they spread out into the available space

Membrane potential

the voltage across a membrane (ranging from -50 to -200 millivolts)

How do glycoproteins and glycolipids help in cell to cell recognition?

they bind with other cells' molecules on the plasma membrane

Facilitated diffusion

when polar molecules and ions impeded by the lipid bilayer diffuse passively with the help of transport proteins, a from of passive transport (no ATP from cell)