lecture 3 minus cell parts Flashcards
eukaryotic cells
cells that possess membranous organelles
makeup of the lipid bilayer (%)
75% phospholipids
20% cholesterol
5% glycoproteins
why must membranes be fluid?
- permits self healing
- allows for membrane growth
- permits fusion with other membranes
how is membrane fluidity regulated? (3)
- cells change the saturation of fatty acids
- saturated = straight
- unsaturated = “kinked”
- unsaturated allows for more space between fatty acids = more fluid - cells change cholesterol amount in membranes
- cholesterol acts as a fluidity buffer
- bulky molecule = increases fluidity
- planar nature of rings prevent movement = lower fluidity - temperature
- high temp - more fluid
why can only non polar molecules cross the membrane?
because non polar things are hydrophobic, things must be hydrophobic to cross
the membrane is impermeable to polar and charged things
integral membrane proteins
anchored to hydrophobic centre of membrane
assist in transport
integral membrane proteins
anchored to hydrophobic centre or membrane
assist in transport
transmembrane proteins
integral proteins that go all the way through
amphipathic
peripheral membrane proteins
bound to membrane by electrostatic interactions
hydrophilic
glycoproteins
membrane proteins bound to saccharides
only found on the outer side
glycocalyx
formed when the saccharides on glycoproteins and glycolipids join
receptors
bind specific molecules and send signals to the inside of the cell to change behavior
receptors
bind specific molecules and send signals to the inside of the cell to change behavior
linker proteins
connect cells and facilitate locomotion
cell identity markers
usually glycoproteins, help body cells or invaders identify cell types
passive transport
diffusion, osmosis
any type of transport that requires, no ATP
passive transport is driven by kinetic energy and concentration gradients
rate of diffusion is effected by: (2)
size of the particles
- bigger = slower
temperature
- high temp = faster molecules = more kinetic energy
diffusion
movement of particles down its concentration gradient
facilitated diffusion
the use of carrier proteins or ion channels (and aquaporins) to help substances cross the bilayer
this is how polar and charged substances can get through
ion channels
passage for facilitated diffusion
may be gated (require a signal before opening)
passive
can only transport one type or ion
carrier proteins
change shape to move solutes across membrane
specific to shape
passive
ex. used to bring glucose into the cell
aquaporins
channels to bring water into the cell
water can diffuse, but these are 50000 time faster
passive
active transport
transport needed to keep concentration gradients (CG) from diffusing
moves substances UP the CG
requires energy (ATP for primary, electrochemical potential for secondary)
how do cells maintain a negative membrane potential
sodium/potassium pump pumps Na out and K in in a 2:3 ratio, keeping the inside negative
primary active transport
moves solutes UP the CG using ATP hydrolysis
secondary active transport
uses electrochemical potential set up by primary active transport as energy
move two solutes at the same time
one solute flows down its CG and releases free energy for the second solute to move UP its CG
antiporters
when solutes in secondary active transport flow in opposite directions
symporters
when both solutes in secondary active transport flow in the same direction
endocytosis
movement into cells via a vesicle
active transport
exocytosis
movement out of cells via a vesicle
also called secretion in some cells
active transport