cell membranes Flashcards
do channel proteins have a specific binding site?
no
what makes a channel protein specific to what it is transporting?
- the specificity of the channel protein is that the narrowest part of the channel protein will only allow molecules of a particular size and charge to pass
what makes a carrier protein specific to what it is transporting?
- it is due to the specific binding sites
what type of proteins are channel and carrier proteins?
- intrinsic/transmembrane proteins
what type of solutes can carrier proteins transfer across the membrane vs channel proteins?
- carrier proteins can transport non-polar and polar molecules
- channel proteins have a hydrophilic core so can only transport small, polar molecules
how do carrier proteins actively transport solutes?
- the solute binds to its complementary binding site on the carrier protein
- ATP binds to the protein and hydrolyses into ATP and phosphate
- binding of the phosphate molecule causes the protein to change shape in that the solute is facing the side it needs to be transported
- solute is released
- phosphate unbinds and combines with ADP to reform ATP
- protein returns back to its original shape
- this changes the shape of the protein in the the bound solute is now facing where it needs to be transported
- the solute is released and the protein returns to its original shape
what is the function of glycoproteins?
- gives the cell adhesive properties
- acts as receptors so important for cell signalling
what is the function of glycolipids?
- acts as an antigen so important for cell recognition
- also can act as a receptor for cell signalling
is cholesterol polar or non-polar and how is it bound in the phospholipid bilayer?
- cholesterol is a non polar molecule because most of the structure is the double carbon ring and only a small part of the molecule is the hydroxyl group
how does cholesterol travel in the blood?
- via high density and low density lipoproteins
what factors can affect the permeability of membranes?
- temperature
- solvents
how does increasing the temperature affect the membrane structure?
- proteins are denatured at higher temperatures
- phospholipids gain more kinetic energy and they vibrate and move more
- the gaps between the phospholipids increase
- the BILAYER becomes more fluid
- permeability of membrane increases
- the increase in fluidity can be reversed but the denaturation of the proteins can’t be reversed
How will the increase in fluidity affect membrane permeability?
- it will allow polar molecules to now pass through as the gaps between the phospholipids are larger
What are some functions of cell membranes within the cell?
- compartmentalisation/ keeping the organelle contents away from the aqueous cytoplasm
- control what substances enter and leave organelles
- provides surfaces for attachment of enzymes and ribosomes
- provides conditions for specific reactions like photosynthesis happens in the chloroplasts?
- concentration gradients can be maintained for specific reactions like oxidative phosphorylation
What are some functions of the cell membrane?
- cell communication
- separates cell contents from aqueous environment
- ## controls what enters and exist the cell
