lecture 6 Flashcards
what is the structure of the cell membrane
fluid mosaic model, its a fluid mosaic of lipids with proteins embedded, and membrane is asymmetrical
what evidences supports fluid mosaic model
membranes are not rigid, consist of fluid lipid bilayer in which proteins embedded and float freely, and human and mouse cell experiment
why is the membrane asymmetric
proteins on one half are structurally and functionally distinct from other half
what is the lipid composition of cell membrane
phospholipid is most dominant, head group has glycerol linked to types of alcohol or amino acid phosphate group, tail has two long chains of hydrocarbon fatty acid
what is a fatty acid
a carboxylic acid with long chain of hydrocarbon, and an even number from 4- 28
what makes phospholipids amphipathic molecules
hydrophilic (“water-loving”) or polar end and a hydrophobic (“water-fearing”) or nonpolar end
how do you maintain a proper fluidity
depends on lipid density, composition and temp.
how do you adjust fatty acid composition
change with temperature
what influences membrane fluidity
cholesterol is essential structural components of animal cell membrane, it acts as membrane buffer
what are the two distinct categories of membrane proteins
-integral membrane proteins
-peripheral membrane proteins
glycolipids
-cell-cell interactions
-immune response
-blood types
what are cell-cell interactions
the direct interactions between cell surfaces that play a crucial role in the development and function of multicellular organisms.
what is immune responses
function in interaction between leukocytes and endothelial cells in inflammation
what is blood type
four main blood type determined by oligosaccharide attached to specific glycolipid on surface of red blood cell
what is the key function of membrane protein
transport, signal transduction, enzymatic activity, and attachment/ Recognition
how do we know protein are inserted into membrane?
integral membrane protein are embedded in phospholipid bilayer
-are transmembrane proteins composed of nonpolar amino acids usually coiled into alpha helices held by covalent bonds
peripheral membrane proteins
most located on cytoplasmic side of membrane, made up of polar and nonpolar amino acids, and held together by noncovalent bonds like hydrogen and ionic bonds
membranes are semipermeable
permeable to non-polar or hydrophobic molecules, impermeable to large and polar molecules
what does permeability depend on
solubility, charge, and solute size
how do molecules move through membranes
diffusion and osmosis
what is diffusion
movement of molecules from high concentration to lower concentration
what is osmosis
diffusion of solvents through semipermeable membrane
what are the two types of membrane transport
-active and passive transport
what is passive transport
-doesn’t require energy
-high concentration to low concentration
what is active transport
-low-concentration to high concentration
-requires direct/indirect input of ATP
what two types of diffusion does passive transport break down into
-simple and facilitated diffusion
what is simple transport
-substances pass through phospholipids
-rate of diffusion depends on concentration difference
what is facilitated diffusion
spontaneous, and ions cross biological membrane
what are properties of facilitated diffusion
-follow concentration gradients
-high diffusion rate
-limited binding capacity
-high substrate specificity
what are three main examples of facilitated diffusion
channel proteins=aquaporin
ion channel protein= K+ voltage-gated channel
carrier protein= glocuse transporter
how does water move through the membrane
by osmosis which is a passive passage
what is tonicity
it is an example of membrane passage by osmosis
tonicity (flow of water in and out of cell) has three groups, what are they
hypotonic, isotonic, and hypertonic
what is a hypertonic solution
osmotic flow out of the cell
what is hypotonic solution
osmotic flow into cell
what is isotonic solution
no osmotic flow
what are channel proteins: aquaporin (ex. of facilitated diffusion)
integral membrane protein that forms pore in membrane
what are ion channel protein: ion voltage-gate channel (ex. facilitated diffusion)
switches between open and closed and intermediate states, this involves changing 3-D shape
what are carrier proteins
bind to specific single solute and transport across lipid bilayer
what are carrier proteins
bind to specific single solute and transport across lipid bilayer
active transport has two types
-primary active tranport
-secondary active transport
what is primary active transport
-moves positively charge ions
-Na+/K+ pump
-h+ pumps
-ca2+ pumps
what do Na+-K+ pumps do
regulate cellular volume
-help maintain right concentration of ions (cell swell automatically activates pump)
what is membrane potential
difference in ion concentration creates difference of charge between exterior and interior part of membrane
what are a secondary source of energy
electrical gradient
what are a secondary source of energy
electrical gradient
what are electrical gradients
provide energy to transport glucose, amino acid, and other nutrients, known as secondary active transport
what are the two forms of secondary active transport
sodium-calcium exchanger, and sodium-hydrogen antiporter
what are sodium-hydrogen antiporter
transport Na+ into cell and H+ out
what is sodium-calcium exchanger
uses energy stored in electrochemical gradient of Na+ by allowing it to flow down gradient across plasma membrane exchange for calcium out of cell
what are the three main functions of Na+-K+ pump
- maintain isotonicity cell volume by pumping out calcium
-create a difference in charge between exterior and interior
-create electrochemical gradient to provide energy to move molecules against concentration gradient
what transports larger substance
exocytosis
what is exocytosis
energy-dependent process which large molecule bulks transported out of cell
what are 3 main function of endocytosis
-pinocytosis
-receptor mediated endocytosis
-phagocytosis
what is pinocytosis (endocytosis)
extracellular fluid and molecules within it
what are receptor-mediated endocytosis
small vesicles coated with cytosolic protein
what are phagocytosis
bind and internalize large particles
how is tissue stability acheived
cell junctions and extracellular matrix
what are tight junctions (impermeable and tissue stability)
rows of transmembrane proteins that bind to corresponding membrane protein of adjacent cell
what are tight junctions (impermeable and tissue stability)
rows of transmembrane proteins that bind to corresponding membrane protein of adjacent cell
what is a gap junction
intercellular channels directly communicate cytoplasm of two cells, allowing passage (ions+small molecules)
what is anchoring junction
link of cytoskeleton with extracellular matr
what is anchoring junction
link of cytoskeleton with extracellular matr
what stages do membrane receptors link extracellular signals with cellular responses
-reception
- transduction
-response
what is kinases
adds chemical called phosphates to other molecules
