Cell Membranes- Topic 2B Flashcards
(50 cards)
What molecules can be found in a plasma membrane?
Phospholipids Proteins (carrier and channel) Cholesterol Glycolipids Glycoproteins
Name the functions of a cholesterol molecule in a membrane?
Reduces lateral movement of other molecules (phospholipids)
Makes membrane less fluid @ high temps
Prevents leakage of water and dissolved ions from the cell.
Name the functions of glycolipids
Act as recognition sites
Help maintain the stability of the membrane
Help cells to attach to one another and so form tissues.
The functions of glycoproteins in the membrane are…
Act as recognition sites
Help cells to attach to one another and so form tissues
Allows cells to recognise one another
Name the functions of proteins in the membrane
Provide structural support
Act as channels for transporting substances
Forms cell-surface receptors for identifying cells
Help cells adhere together
Act as receptors e.g hormones
Only what type of substances can be transported across the membrane?
Water-soluble substances
How does a colorimeter work?
Uses the light passed through the liquid & measures the amount of light that has been absorbed.
What two things could be your independent variable?
The concentration of solvent
The temperature of the water baths.
How can you remove any pigment released from cutting the beetroot?
Rinse the pieces after cutting them.
On a graph which axis do you plot which variables on?
The “independent variable” goes on the x axis
The “dependent variable” goes on the y axis
Define diffusion:
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration
Why would larger molecules take a while to diffuse through the bilayer?
Because they are so big
Other than large particles, what other molecules would diffuse slowly?
Ions and polar molecules because they’re water soluble and the centre of the bilayer is HYDROPHOBIC
What is different about facilitated diffusion?
Large or charged particles diffuse through carrier proteins or channel proteins
What type of process can diffusion and facilitated diffusion be classed as?
Passive processes- they don’t use energy.
Carrier proteins move ….. ……… across membranes
Carrier proteins move large molecules across membranes
Channel proteins form pores in the membranes for ……. ……… to diffuse through.
Channel proteins form pores in the membrane for charges particles to diffuse through.
What factors does the rate of (simple) diffusion depend on?
Concentration gradient
The thickness of the exchange surface
The surface area (microvilli in epithelial cells)
What factors does facilitated diffusion depend on?
The concentration gradient
The number of channel or carrier proteins
Define Osmosis
The diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential
What is water potential?
The potential of water molecules to diffuse out of or into a solution
Pure water has the ……. water potential. This means ALL solutions have a ……. water potential than pure water.
Pure water has the highest water potential. All solutions have a lower water potential than pure water
If two solutions have the same water potential, what are they said to be?
ISOTONIC
List the factors affecting the rate of osmosis?
The water potential gradient
The thickness of the exchange surface
The surface area of exchange surface
