Chapter 5 Flashcards
Fluid-Mosaic Model
Fluid: phospholipid
Proteins: Mosaic
Model that explains structure and function of cell membrane
Membrane fluidity
cholesterol and carbohydrates (glycoprotein/glycolipid)
Membrane phospholipids
Glycerol, phosphate, fatty acids(2), hydrophobic (non polar, tails) and hydrophilic (polar, head)
amphipathic
on the same molecule
phospholipid head
hydrophilic, head
phospholipid tails
hydrophobic, tails
membrane proteins
proteins on plasma membrane
Integral protein
Penetrate membrane, transmembrane, hydrophobic (alpha helices), hydrophilic channels(beta barrels)
membrane protein
Peripheral
Attached to one layer
outside -> extracellular matrix
inside -> Cytoskeleton
Interact with integrals
membrane protein
Transporters
channels: (doorway into cell)
movement of ion/molecule
may be voltage or ligand gated (open and close)
membrane protein
Carrier: Interact with specific molecules, binds and allows transport, may involve ATP
membrane protein
Channel transporter
doorway into cell
movement of ion/molecule
may be voltage or ligand gated (open and close)
membrane protein
Carrier transporter
Interacts with specific molecules, binds and allows transport, may involve ATP
membrane protein
Enzyme membrane protein
Integral/peripheral
catalyze rxn.s on plasma membrane
membrane protein
Signal transduction (indirect)
receptor protein, specific signal molecule
binding -> confirmation of change
transmit signal and propagate through cell
membrane protein
Cell recognition
Glycoproteins, recognized by plasma membrane, temporary close interaction
membrane protein
Embedded proteins
fully embedded into phospholipid bilayer
Intracellular junctions
Close plasma membrane to plasma membrane connections
protein 1-> protein2
longer lasting communication
tissue formation
Intra/extra cellular protein interactions
connection to extracellular matrix/ cytoskeleton
maintain cell shape and function
stabilize protein location
transmit signal out -> in
Cholesterol
embedded in membrane, membrane fluidity ( we want cholesterol )
“goldilocks”
High temp cholesterol
fluid plasma membrane
Low temp cholesterol
viscous plasma membrane
Carbohydrates
chain/branching outside of cell
bound to glycoproteins/lipids,
cell-cell recognition
Permeability of Plasma membrane
Selectively (semi) permeable
Free movement across PM
Passive diffusion, with channel, with carrier
Passive diffusion
nonpolar molecules (nonpolar tails), gases, glycerol, free
movement through PM channel
Aquaporins, free
movement through PM carrier
Glucose, free
“fee” required movement across PM
active transport, cost ATP, charged particles, large molecules
simple chemical diffusion
concentration gradient present, down concentration gradient
high -> low
outside -> inside
until equilibrated
Spontaneous diffusion
No energy required, solute or solvent, often water
Passive transport
Across PM
Diffusion of water
High -> low
across PM
PM -> selective
spontaneous, passive (no energy)
Osmotic pressure
Created by H2O differences, pressure required to prevent osmosis
Tonicity
relative amount of solute in a solution
Hypertonic
large amount of solute
Hypotonic
small/no amount of solute
Isotonic
no gradient (= amount solute concentration)
Animal cell hypotonic
cytolysis (cell bursts)
Animal cell isotonic
:-)
Animal cell hypertonic
crenation (cells shrink)
Plant cell hypotonic
:-)
Plant cell isotonic
small shrinkage
Plant cell hypertonic
Plasmolysis (contraction of protoplast from cell wall)
turgor pressure
force that pushes plasma membrane of cell against cell wall
Facilitated diffusion
protein assisted diffusion, down concentration gradient
high to low until equilibrated
outside to inside
no energy needed
Active transport
Costs energy to move across plasma membrane
Primary active transport
against concentration gradient
low to high
inside to outside
moving ions
energy required
carrier proteins
(uniport, symport, antiport)
Uniporter
movement of single molecule across membrane
active transport
Symporter
movement of two or more molecules across membrane in the same direction
active transport
Antiporter
movement of two or more molecules across membrane in separate directions
active transport
Secondary active transport
Cotransport (symports)
Movement of one facilitates movement of the 2nd
against concentration gradient
more bang for buck (only pay for one)
Na+ pump (fuels glucose movement and cell uptake of glucose)
Proton pump (fuels diffusion of H+ and sucrose movement)
Difference between primary and secondary active transport
primary requires ATP (or chem energy)
secondary uses electrochemical gradient (created by active transport) to fuel movement of molecules
Bulk transport
membrane assisted
continuous (same rate in and out)
Endocytosis
Bringing into cell
Phagocytosis
“cell eating”
large macromolecules/whole organisms
Exocytosis
Secretion outside of cell
Pinocytosis
“cell drinking”
small molecules
microvilli of small intestine
Transport vesicle
- from golgi apparatus
- along microtubule
- travels to PM
- fuses and releases contents outside
- becomes part of PM
replenishes/balanced by endocytosis [create vesicle]
