Biol 253 Exam 1 questions with complete solutions

Biol 253 Exam 1 questions with
complete solutions


universal function of membranes - answer-to act as a selective barrier to the passage of
v v v v v v v v v v v v v v


molecules
v




functions of plasma membranes - answer-1. regulate passage of substances in and out
v v v v v v v v v v v v


vof cells and between cell organelles and cytosol
v v v v v v v


2. detect chemical messengers arriving at the cell surface
v v v v v v v v


3. link adjacent cells together by membrane junctions
v v v v v v v


4. anchor cells to the extracellular matrix
v v v v v v




integral membrane protein - answer-closely associated with membrane lipids
v v v v v v v v




can't be extracted from the membrane without disrupting the lipid bilayer
v v v v v v v v v v




amphipathic (polar out, nonpolar in) v v v v




some can move laterally but others can't because they are linked to peripheral proteins
v v v v v v v v v v v v v




transmembrane proteins - answer-Integral proteins that span the membrane.
v v v v v v v v




peripheral membrane proteins - answer-located on membrane surface and are bound to
v v v v v v v v v v v


the polar regions of integral proteins
v v v v v v




not amphipathic
v




glycoalyx - answer-layer of sticky carbohydrates covering plasma membrane, provides
v v v v v v v v v


strength, attachment and cell cell recognition, anchored to the plasma membrane by
v v v v v v v v v v v v


carbohydrates bonded to proteins and lipids in the membrane
v v v v v v v v v




fluid mosaic model - answer-model that describes the arrangement and movement of
v v v v v v v v v v v


vthe molecules that make up a cell membrane
v v v v v v v




lipid rafts - answer-cholesterol-rich regions of reduced membrane fluidity that are
v v v v v v v v v v


vbelieved to serve as organizing centers for the generation of complex intracellular
v v v v v v v v v v v


vsignals

integrins - answer-A transmembrane protein that interconnects the extracellular matrix
v v v v v v v v v


vand the cytoskeleton.
v v

,Desmosomes - answer-Anchoring junctions that prevent cells from being pulled apart v v v v v v v v v v




Cadherins - answer-proteins that extend from the cell into the extracellular space, where
v v v v v v v v v v v v


they link up and bind with cadherins from an adjacent cell
v v v v v v v v v v v




tight junction - answer-junction that forms between two adjacent plasma membranes to
v v v v v v v v v v v


vremove extracellular space between them v v v v




occurs in a band around the entire circumference of the cell
v v v v v v v v v v




gap junctions - answer-protein channels that link the cytosols of adjacent cells
v v v v v v v v v v v
v


limits what can pass between the cytosols of the connected cells to small molecules and
v v v v v v v v v v v v v v


vions

simple diffusion - answer-movement of a solute from an area of high concentration to an
v v v v v v v v v v v v v v


area of low concentration
v v v v




flux - answer-the amount of material crossing a surface in a unit of time
v v v v v v v v v v v v v




net flux - answer-difference between two one-way fluxes
v v v v v v v




determines net gain for compartment 2 and net loss for compartment 1 v v v v v v v v v v v




always greater from regions of higher conc. to lower conc.
v v v v v v v v v




diffusion equilibrium - answer-state during which diffusion fluxes in opposite directions
v v v v v v v v v v


are equal; that is, the net flux equals zero
v v v v v v v v v




factors that affect net flux - answer-1. temperature: higher temp = faster net flux
v v v v v v v v v v v v v


2. mass of molecule: larger molecule = slower net flux
v v v v v v v v v


3. surface area: greater surface area = faster net flux
v v v v v v v v v


4. medium: air = faster net flux
v v v v v v




Fick's Law of Diffusion - answer-J = PA(Co-Ci)
v v v v v v v




J= rate of diffusion/magnitude of net fluc
v v v v v v




Co= conc. outside cell
v v v




Ci= conc. inside cell
v v v




A = surface area of membrane
v v v v v




P= membrane permeability coefficient (larger = faster net flux)
v v v v v v v v

, ion channels - answer-allow the passage of ions across the membrane
v v v v v v v v v v




small size prevents larger molecules from entering or leaving
v v v v v v v v




show selectivity for type of ions that can pass through
v v v v v v v v v




membrane potential - answer-the electrical charge across a cell membrane
v v v v v v v v v




provides electrical force that can influence the movement of ions through their channels
v v v v v v v v v v v v


across the plasma membrane
v v v v




electrochemical gradient - answer-The combination of forces that acts on membrane v v v v v v v v v v


potential.
v




channel gating - answer-process of opening and closing ion channels
v v v v v v v v v




factors that alter channel protein conformations - answer-1. binding of specific molecules
v v v v v v v v v v v


vto channel proteins
v v v


2. changes in membrane potential
v v v v


3. physically deforming the membrane
v v v v




ligand-gated ion channel - answer-changes shape in response to a signaling molecule
v v v v v v v v v v v


v(ligand), allowing or blocking the flow of specific ions
v v v v v v v v




voltage-gated ion channels - answer-Channels that open or close in response to a
v v v v v v v v v v v v


change in the membrane potential.
v v v v v




mechanically gated ion channels - answer-opened or closed by deformation or stretch of
v v v v v v v v v v v v


the plasma membrane
v v v




transporters - answer-integral membrane proteins that mediate passage of molecules
v v v v v v v v v


vthrough membrane v




mediated transport - answer-movement of molecules across membrane by binding to
v v v v v v v v v v


protein transporter
v v




factors that determine solute flux through mediated-transport system - answer-1. solute
v v v v v v v v v v


vconcentration
2. affinity of transporters for solute
v v v v v


3. number of transporters in membrane
v v v v v


4. rate at which conformational change in transport protein occurs
v v v v v v v v v




facilitated diffusion - answer-the movement of specific molecules across a cell
v v v v v v v v v v


vmembrane through protein channels v v v v




high to low v v