chapter 5 study questions

what does a diuretic do?

it incr your urine volume by incr the amt of water in your urine. ADH decreases the amt of water in your urine, bc more water is reabsorbed by your kidneys

what allows facilitated diffusion to occur?

channel proteins and carrier proteins

what is phagocytosis?

ingesting large solid particles folds of plasma membrane enclose the cell or particle, forming a vacuole, which may fuse with lysosomes, degrading ingested material

what are transmembrane proteins?

integral proteins that extend completely through the membrane

what the difference btwn intercellular and intracellular?

inter = btwn cells intra = within cells

what would happen if a plant cell were placed in an isotonic solution? a hypertonic environment? a hypotonic environment? how would you modify your predictions for an animal cell?

isotonic conditions result in no change in plant or animal cells. under hypertonic conditions plant cells undergo plasmolysis due to water loss; they become turgid under hypotonic conditions. hypertonic conditions cause animal cells to shrink; under hypotonic conditions they swell and may possibly burst

what does it mean for a biological membrane to be selectively permeable?

it allows some, but not all substances to pass through it

what is the function of a plasma membrane?

it separates the cell from the outside world; regulates passage of materials in and out of the cell; helps maintain homeostasis

what allows phospholipids to associate with water more easily as a bilayer?

its cylindrical shape

what does membrane fluidity depend on?

its lipid composition

what substances are membranes impermeable to?

large polar molecules, ion/electrically charged molecules

what are peripheral membrane proteins?

located on inner or outer surface of plasma membrane, bound to exposed regions of integral proteins

hypotonic solution

lower conc of solutes outside the cell *cell swells

describe the hydrophobic region of a phospholipid.

made up of 2 fatty acid chains; nonpolar

which component of the endomembrane system is most associated with the breakdown of fatty acids?

peroxisome

how are the processes of phagocytosis and pinocytosis different?

phagocytosis moves large solid particles across the membrane; pinocytosis moves dissolved molecules.

what molecules are responsible for the physical properties of a cell membrane?

phospholipids and sterols are the primary determinants of membrane lipid bilayer fluidity

what happens to cells when they are placed in a hypertonic solution?

plant cells = plasmolysis animal cells = crenation

what happens to cells when they are placed in a hypotonic solution?

plant cells = turgor pressure animal cells = hemolysis

which cell junctions occur btwn plant cells?

plasmodesmata

what is the job of cholesterol molecules in membranes?

"fluidity buffers" - keep hydrocarbon chains fluid at low temp and stabilize them at high temp

what is the purpose of electrochemical gradients?

(for ions) store energy that is used to drive other transport systems; the basis of major energy conversion systems in cells

what are some advantages of an endomembrane system?

- separation of potentially dangerous cmpds from the rest of the cell - optimized pH for select rxns - optimized rxn conditions for select rxns - concentration of enzymes and reactants for select rxns

what are the functions of cell membranes?

- serve as a boundary - serve as a work surface - allow for energy storage

what are gap junctions?

- allow communication btwn cells - composed of connexin proteins molecules that are grouped to form a cylinder that spans the plasma membrane. connexin cylinders on adjacent cells join, forming a single channel connecting two cells' cytoplasm - cells control passage of materials through gap junctions by opening/closing the channels

what are the functions of membrane proteins?

- anchor the cell to its substrate - transport molecules across the membrane - catalyze enzymatic rxns near the cell surface - receive info from other cells in the form of chem or electrical signals - serve as an identification tag

describe adhering junctions

- cement cells together

what are tight junctions?

- connections btwn cell membranes that are so tight, no space remains btwn the cells

what is plasmodesmata?

- connections btwn plant cell walls that are functionally equivalent to gap junctions - channels that pass through the cell walls and plasma membranes of adjacent plant cells

what are three important characteristics of lipid bilayers?

- flexible: allows cell membranes to change shape without breaking - self-sealing: spontaneously round up to form closed vesicles - can fuse with other bilayers: allows vesicles to transfer materials from one compartment to another, or secrete a product from the cell

describe desmosomes.

- points of attachment that hold cells together at one spot - allows cells to form strong sheets, substances still pass freely btwn plasma membranes - consist of regions of dense material and protein filaments that cross intercellular space btwn membranes - anchored to intermediate filaments inside the cells, which distributes mechanical stress

describe the behavior of phospholipid bilayers?

- they behave like liquid crystals - form an ordered array but are in constant motion - phospholipid molecules are free to rotate and can move laterally within their single layer - molecules embedded in the membrane can move along the plane of the membrane, producing an ever-changing configuration

what are some examples of passive transport across the cell membrane?

- water moving across the membrane independently of an aquaporin - water moving across the membrane through aquaporins

describe ABC transporters

ATP Binding Cassette; use energy donated by ATP to transport certain ions, sugars, and polypeptides

give an example of indirect active transport.

Na/glucose cotransporter uses the concentration gradient for Na+ formed by the Na/K pump to transport Na+ downhill, as glucose is cotransported uphill. the cotransporter has to bind both Na+ and glucose in order to function

what best describes a semi-permeable membrane?

a membrane through which some, but not all, substances can move

what is active transport?

a system (aka a transmembrane protein) across the cell membrane that pumps materials from a region of low concentration to a region of high concentration

what is the immediate energy source for active transport?

active transport requires a source of metabolic energy, such as ATP.

what are phospholipids?

amphipathic molecules w/ distinct hydrophobic and hydrophilic regions

what are integral membrane proteins?

amphipathic proteins firmly bound to the membrane

which cell junctions occur btwn animal cells?

anchoring, tight, gap

what are the four types of cell junctions?

anchoring, tight, gap, and plasmodesmata

how are proteins oriented across the bilayer

asymmetrically

why are membranes important to cells?

bc separating a cell from its external environment is essential to origin of life

in what ways are exocytosis and endocytosis similar?

both exocytosis and endocytosis move materials across the plasma membrane by vesicular transport mechanisms.

what are the two main types of transport proteins?

carrier proteins & channel proteins

what is indirect active transport?

concentration gradient provides energy for the cotransport of some other substance

what are the two types of anchoring junctions?

desmosomes & adhering junctions

what is the immediate energy source for cotransport?

in cotransport, the transport of a substance down its concentration gradient provides the energy to drive the transport of the other substance against its concentration gradient.

describe the hydrophilic region of a phospholipid.

fatty acid tails bonded via a glycerol molecule to a negatively charged, hydrophilic phosphate group, linked to a polar, hydrophilic organic group; polar

describe channel proteins

form water filled pores in the membrane to transport H2O and specific types of ions

what substances are membranes permeable to?

gases, hydrophobic/nonpolar molecules, small polar molecules

what are aquaporins?

gated water channels that allow rapid transport of H2O through the plasma membrane

hypertonic solution

higher conc of solutes outside the cell *cell shrinks

the phospholipid bilayer is composed of phospholipids with ___ heads and ___ tails.

hydrophilic; hydrophobic

what are cadherins?

important protein cmpds of anchoring junctions

how do proteins function in transporting materials into the cell?

materials move across bilayers through transmembrane proteins that form highly selective channels or pumps for different types of molecules.

what takes place primarily in the rough ER?

modification of secreted proteins

the plasma membrane is considered a fluid mosaic bc it permits incorporated molecules such as receptors and transport proteins to ___.

move around laterally within the membrane

how do cotransport systems indirectly provide energy for active transport?

movement of one solute down its concentration gradient provides energy for transport of some other solute up its concentration gradient

what is simple diffusion?

movement of small, non polar solute molecules directly through the membrane and down the cone gradient

what is diffusion?

net movement of particles from an area of high concentration to low concentration *moves solutes towards a state of dynamic equilibrium

isotonic solution

no net movement of H2O molecules btwn cell and surrounding fluid

what is facilitated diffusion?

occurs when a specific transport protein makes the membrane permeable to a specific ion or polar molecule

describe the transport of uniporters.

one substance, one direction ex: proton pumps

what happens in dynamic equilibrium?

particles are uniformly distributed and there is no net change in the system

what are transport proteins?

proteins responsible for moving ions, amino acids, sugars, and other needed polar molecules through membranes

what is a cell?

smallest unit that can carry out all activities associated with life; building blocks of complex multicellular organisms

what happens to solvent is solute incr?

solvent decr *and vice versa

what roles do membrane proteins play in cell interactions?

some membrane proteins respond to extracellular signal molecules. extracellular parts of some transmembrane proteins can bind or link to proteins on the surface of neighboring cells.

what is receptor-mediated endocytosis?

specific molecules combine with receptor proteins in the plasma

what type of structures do amphipathic molecules with different shapes form in water?

spherical

what are anchoring junctions?

strong junctions that tightly bind adjacent epithelial cells, such as those found in the outer later of mammalian skin

what is the pathway used by cells to place carbohydrates on plasma membrane proteins?

sugars added to protein in ER lumen ➝ glycoprotein transported to Golgi complex, where it is further modified ➝ glycoprotein transported to plasma membrane ➝ transport vesicle fuses with plasma membrane ➝ inside layer of transport vesicle becomes outer layer of plasma membrane

what carrier proteins are cotransporters?

symporters and antiporters

what is pinocytosis?

taking in dissolved materials droplets of fluid are trapped by folds in the plasma membrane, which pinch off into the cytosol as vesicles, becoming smaller in liquid

what is the osmotic pressure of a solution?

the amt of pressure exerted on the side of the membrane containing the higher concentration of solute that prevents the diffusion of water from the side containing the lower solute conc *solute (solid) + solvent (water) = 100% of a solution

what is required for active transport to occur?

the cell has to expend energy

what is endocytosis?

the cell imports materials by phagocytosis, pinocytosis, and receptor-mediated endocytosis

what is osmosis?

the diffusion of water

what is the immediate source of energy for simple diffusion? for facilitated diffusion?

the energy source for diffusion and facilitated diffusion is a chemical concentration gradient.

what part of the phospholipid faces the cytosol inside a cell?

the hydrophillic head

what is passive transport?

the movement of materials across the cell membrane without using cellular energy

in what direction is there a net movement of particles along their concentration gradient? would your answers be different for facilitated diffusion compared with simple diffusion?

the net movement of particles in a concentration gradient is from a region of high concentration to low concentration. simple diffusion and facilitated diffusion do not differ in the direction of net particle movement.

describe carrier proteins

they bind the ion or molecule and change shape, moving the moleucle across the membrane

what are cell junctions?

they connect cells that... - form strong connections with one another - prevent the passage of materials - establish rapid communication btwn adjacent cells

what is carrier mediated transport?

transfer of solutes by carrier proteins located within the membrane *two forms: one is active transport and the other is passive

what are porins?

transmembrane channel proteins that allow solutes or water to pass through membranes

ions and polar molecules can cross the plasma membrane in regions where the membrane has incorporated ___.

transport proteins

true or false: prokaryotes, algae, plants, and fungi can withstand hypotonic solutions

true bc all have rigid cell walls

describe the transport of symporters.

two substances, one (the same) direction ex: cotransported sodium and glucose

describe the transport of antiporters.

two substances, opposite directions ex: sodium-potassium pumps

what are the three types of carrier proteins?

uriporters, symporters, and antiporters

what is excocytosis?

when vesicles export large molecules by the fusion of a vesicle with the plasma membrane