BIOL235_Chap3 Flashcards
cells
are the basic, living, structural, and functional units of the body
plasma membrane
forms the cell’s flexible outer surface, seperating the cell’s internal environment from its external environment
cytoplasm
consists of all cellular contents betw plasma membrane and nucleus
cytosol + organelles
cytosol
fluid portion of the cytoplasm = intracellular fluid
nucleus
large organelle that houses most of cell’s dna
3 main parts of a cell
plasma membrane
cytoplasm
nucleus
what does the plasma membrane do?
it provides a flexible yet sturdy barrier that sourrouands and contains the cytoplasm of a cell
fluid mosaic model
model of a cell that says the molecular arrangement of the plasma membrane resembes a continually moving sea of fluid lipids that contains a mosaic fo many diff proteins
lipid bilayer
the basic structural framework of the plasma membrane
2 back-to-back layers made up of 3 lipid molecules (phospholipids, cholesterol, glycolipids)
3 lipid molecules making up the lipid bilayer
phospholipids
cholesterol
glycolipids
phospholipids
lipids that contain phosphorus
cholesterol
carbohydrate important for cell shape
inside plasma membrane
steroid with an attached OH group
glycolipids
lipids with attached carbohydrate groups
integral proteins
proteins that extend into or thru the lipid bilayer and are firmly embedded in it
most are transmembrane proteins
most are also glycoproteins
transmembrane proteins
proteins that span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid
peripheral proteins
proteins that are not firmly embedded in the membrane. they are attached to the polar heads of membrane lipids or to integral proteins at the inner or outer surface of the membrane
glycoproteins
proteins with carbohydrate groups attached to the ends that protrude into the extracellular fluid
glycocalyx
an extensive sugary coat formed by carbohydrate portions of glycolipids and glycoproteins
6 membrane’s functions
- ion channels (integral)
- carrier (integral)
- receptor (integral)
- enzyme (integral + peripheral)
- linker (integral + peripheral)
6 cell identity marker (glycoprotein)
ion channels
pores or holes that specific ions can flow thru to get into or out of the cell
most are selective
formed by integral proteins
carriers
integral proteins that act as transporters and selectively move a polar substance or ion from one side of membrane to other
integral proteins
receptors
integral proteins that serve as cellular recognition sites where each type of recepor recognizes + binds a specific molec
integral
enzymes
integral or peripheral proteins that catalyze specific chemical reactions at the inside or outside surface of the cell
integral or peripheral
linkers
integral or peripheral proteins that anchor proteins in the plasma membranes of neighboring cells to one another or to protein filaments inside + outside the cell
integral or peripheral
cell-identity markers
membrane glycoproteins and glycolipids that enable a cell to recognize other cells of the same kind during tissue formation or recognize + respond to potentially dangerous foreign cells
glycoproteins
membranes are
fluid structures
selective permeability
a property of plasma membranes that permits some substances to pass thru it more readily than others
concentration gradient
a difference in concentration of a chemical from one place to antoher
electrical gradient
difference in electrical charges betw two regions
membrane potential
membrane potential
a name for electrical gradient bec it occurs across plasma membrane
electrochemical gradient
the combined influence of the concentration gradient + electrical gradient on movement of a particular ion
passive processes
process where a substance moves down its concentration or electrical gradient to cross membrane using its own kinetic energy
active process
process where cellular energy is used to drive the substance “uphill” against its concentration or electrical gradient
vesicles
tiny spherical membrane sacs that can help substances enter or leave cells through active process
diffusion
a passive process in whihc random mixing of particles in a solution occurs because of the particles’ kinetic enrgy
both solutes + solvent and liquid undergo diffusion
5 factors influencing diffusion rate
- steepness of the concentration gradient
- temperature
- mass of diffusing substance
- surface area
- diffusion distance
steepness of concentration gradient influence on diffusion rate
the greater the difference in concentration betw 2 sides of membrane, the higher the rate of diffusion
temperature influence on diffusion rate
the higher the temp, the faster the rate of diffusion
mass of the diffusing substance influence on diffusion rate
the larger the mass of the diffusing particle, the slower its diffusion rate
surface area influence on diffusion rate
the greater the distance over which diffusion must occur, the longer it takes
simple diffusion
a passive process where substances move freely thru the lipid bilayer of the plasma membranes of cells without the help of membrane transport proteins
facilitated diffusion
process where an integral membrane protein assists a specific substance across the membrane (channel or carrier)
channel-mediated facilitated diffusion
a solute moves down its concentration gradient across the lipid bilayer thru a membrane channel
mostly ion channels
gated channel
when part of the channel protein acts as a plug or gate, changing shape in one way to open the pore and in another way to close it
carrier-mediated facilitated diffusion
where a carrier moves a solute down its concentration gradient across the plasma membrane
passive process
transport maximum
number of carriers available in a plasma membrane resulting in an upper limit for how much solute can be transported in carrier-mediated facilitated diffusion
osmosis
type of diffusion where there is a net movement of solvent thru a selectively permeable membrane
water moves from lower so solute conc to higher
aquaporins
integral membrane proteins that function as water channels
play critical role in controlling water content of cells
hydrostatic pressure
pressure exerted by a liquid on the membrane that results when osmosis of water occurs such that 1 side has more water than the other
osmotic pressure
pressure that is proportional to the concentration of solute particles that cannot cross the membrane
the higher the solute conc, the higher the solutions osmotic pressure
tonicity
measure of the solutions ability to change the volume of cells by altering their water content
isotonic solution
any solution in which a cell maintains its normal shape and volume
hypotonic solution
a solution that has a lower conc of solutes that the cytosol inside the red blood cells
hemolysis
rupture of red blood cells due to water molecs entering cells faster than leaving and leading to RBC swell and burst in hypotonic solutiosn
hypertonic solution
solution that has a higher conc of solutes than cytosol inside RBC
leads to crenation
crenation
shrinkage of cells due to hypertonic solution, where water leaves cells faster than it enters
active transport
an active process because energy is required for carrier proteins to move solutes across membrane agains a conc gradient.
primary active transport
active transport where energy derived from hydrolysis of ATP changes the shape of a carrier protein which pumps a substance across a plasma membrane against its concentration gradient.
pumps
carrier proteins that mediate primary active transport
sodium-potassium pump
carrier protein that is most prevalent primary active transport mechanism and expels sodium ions from cells and brings potassium ions in
Na+-K+ ATPase
sodium-potassium pump
secondary active transport
active transport where the energy stored in a Na+ or H+ concentration gradient is used to drive other substances across the membrane against their own conc gradients
process of secondary active transport
a carrier protein simultaneously binds to Na+ and another substances and then changes its shape so that both substances cross the membrane at the same time
symporters
transporters that move 2 substances in the same direction
antiporters
transporters that move 2 substances in opposite directiosn across the membrane
vesicle
intracellular cell movement
small spherical sac
transports a variety of substances from one structure to anther within cells
also import/release materials into intracellular fluid
endocytosis
vesicle transport where materials move into a cell in a vesicle formed from the plasma membrane
exocytosis
vesicle transport where materials move out of a cell by the fusion with he plasma membrane of vesicles formed inside the cell
edocytosis + exocytosis both require…
energy supplied by ATP
6 steps of receptor-mediated endocytosis
- binding
- vesicle formation
- uncoating
- fusion with endosome
- recycling of receptors to plasma membrane
- degradation in lysosomes