CELS 191 Lecture 3 Flashcards
what must a cell do
manufacture cellular materials
obtain raw materials
remove waste
generate the required energy
control all of the above
how does the cells interaction with the environment limit the maximum size of a cell
because a smaller cell has a a greater surface area to volume ratio than a larger cell. therefore is the cell is too big there’s not enough surface area to bring in/take out molecules
why must a membrane be fluid
fluidity of a membrane affects both its permeability and the ability of membrane proteins to move to there their function is needed
what are the factors that affect membrane fluidity
saturation
temperature
cholesterol
how does saturation affect membrane fluidity
if the carbons in the lipids tails of the membrane are saturated there are no double bonds so all the tails can pack tightly together. this means less fluidity. if the lipids are unsaturated there are double bonds that cause kinks in the lipid tails and prevent them from packing too close together. this allows for more movement and increased fluidity
how does temperature affect membrane fluidity
high temperature cause more fluidity, where as lower temperatures reduce fluidity
how does cholesterol affect membrane fluidity
at relativity high temperatures cholesterol makes the membrane less fluid by restraining phospholipid movement. however because cholesterol also hinders the close packing of phospholipids, it lowers the temperature required for the membrane to solidify.
what are the functions of membrane proteins
signal transduction
cell-cell recognition
intercellular joining
linking cytoskeleton and ECM
membrane transport
what is diffusion
membranes are permeable to lipid soluble (hydrophobic) molecules. this is passive transport do molecules move down their concentration gradient
what is facilitated diffusion
The movement of hydrophilic molecules requires membrane proteins called carrier and channels. carriers undergo a shape change to help guide the molecule whereas channels allow the molecule to pass straight through a channel
what is osmosis
a type of diffusion which occurs when water moves down its concentration gradient across the cell membrane
what type of channel is needed for osmosis
aquaporins
what is osmoregulation
cells moving water across the semipermeable membrane to prevent swelling or shrinking under various conditions
what is active transport
the movements of substances against their concentration gradients with the help of carriers which require ATP
what is co-transport
a type of indirect active transport in which one substance is pumped across the membrane (against its concentration gradient so ATP is required). this substance then wants to move back down its concentration gradient. in order to move back down its concentration gradient it has to pair up with another molecule and go through a transport protein.. the molecule that it pairs up with however is moving against its concentration gradient but because it is attached to the initial molecule it is able to move up the concentration gradient without needing ATP.
