Chapter 7 Flashcards

Terms Definitions
Name the four major large molecules of all living things
Lipids, Proteins, Carbohydrates, Nucleic Acids
Explain what is meant when we say a molecule is amphipathic
it means the molecule has a hydrophobic and a hydrohilic region
describe the Davson-Danielli model of membranse structure. what were 2 problems with it?
a phospholip bilayer between 2 layers of protien. problem 1: generalization that all membranes of the cells were identical. Prolem 2: protein placement was wrong
who proposed the fluid mosaic model? when? describe
S.J. Singer and G. Ncholson proposed in in 1972. this model prposes that membrane proteins are dispersed, individaully inserted into the phospholipid bilayer with their hydrophilic regiona protruding
what is membrane fluidity? descirbe movements seen in the fluid
it means that membranes are not locked in place, they can move because of weak bonds it experiences. the movements are lateral
describe how decreasing temperature affects membrane fluidity
the phopholipids pack together and the mebrane solidifies
describe how phospholipids with unsaturated hydrocarbon chains affects membrane fluidity
remains fluid to a lower temperature
describe how cholestorol affects membrane fluidity
makes membranes less fluid at higer temperatures
describe integral protiens
penetrate the hydrophobic core of the lipid bilayer
describe peripheral proteins
not appended in the lipid bilayer, appendages loosely bound to the surface of the membrace
major functions:transport
a protein can provide a hydrophilic channel across the membrane or it can move substances from one side to the other by changing shape
major functions: enzymatic activity
a protein in the membrane can be an enzume with its active site, several of the enzymes can form a team that carries out steps of a metablic pathway
major functions: signal transduction
a membane protein may have a binding site with a shape of a chemcial messenger. external messengers can cause a shape change in the messenger protein
major functions: cell-cell recognition
some glycoproteins serve as indentification tags recognized by membrane proteins of other cells
major functions:intercellular joining
membrane proteins of adjacent cells may hook together at junctions
major functions: attachment to cytoskeleton and ECM
microfilaments or other parts of cytoskeleton may be noncovalently bound to a membrane proteins. proteins bounded to ECM molecules can coordinate cellular changes
distinguish between glycolipids and glycoproteins
a glycolipid is a lipid attached to carbohydrates while glycoproteins are pretiens attached to carbohydrates
distinguish between channel proteins and carrier proteins
channell proteins provide a channell that certain molecules or ions can use. carrier proteins change shapes to allow passengers to pass through
are transport proteins specific?
they are specific for the substance it translocates
what are aquaporins
a channel protein in the plasma membrane of cells that specifically facilitates osmosis
crossing the membrane: CO2
dissolve in lipid bilayer and cross with the help of membrane proteins
crossing the membrane: glucose
use carrier proteins, hold onto their passengers and change shape to pass through the membrane
crossing the membrane: H+
pass through a hydrophillic channell
crossing the membrane: O2
dissolve in lipid bilayer and cross with the help of membrane proteins
crossing the membrane: H2O
water molecules pass through aquaporins at the rate o about 3 billion a second
define diffusion
the movement of molecules so that they spread evenly in the available space
defince concetration gradient
the region along which the density of a chemical substance
define passive transport
the diffusion of a substance across a biologcal membrane
define osmosis
passive transport of water
define isotonic
reffering to a solution that has no effect on water
define hypotinic
reffering to a solution that will make the cell lose water
define hypertonic
reffering to a solution that will make the cell gain water
define turgid
swollen or distended
define flaccid
limp
define plasmolysis
when the cytoplasm shrivels and the plasma membrane pulls away from the cell wall, occurs when the cells lose too much water
what is facilitated diffusion
it is the spontaneous pasage of molecules or ions through a biological membrane with the asistance of specific proteins. it is passive transport
why dont plant cells burst in hypertonic solutions?
because the cell wall holds it in place
waht is active transport?
it is the movement of substances across a cell membrane with a release of energy. it goes against the concentration gradient. carrier proteins are involved. ATP supplies the power for this proccess
what is membrane potential
it is the coltage across a membrane. the outside of the membrane is positive. the inside is negative
what are the 2 forces that drive difusion of ions across the membrane
electirical and chemical forces. the combination of them is called electrohemical gradient
what is cotransport
it is the coupleing of the downhill diffusion of one substance with the uphill transport of another against its concentration gradient
define endocytosis
cellular uptake of biological molecules and particle matter via formation of new vesicles
define phagocytosis
type of endocytosis, large molecules are taken up by the cekk
define pinocytosis
type of endocytosis, cell ingests extracellular fluid and its dissolved solutes
define exocytosis
opposite of endocytosis
define receptor-mediated enocytosis
movement of specific molecules into a cell by the inward budding of membranous vesciles
what is a ligand
it is a molecule that binds specifically to another molecule, usually a large one
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