Transport across cell membranes Flashcards
Define Diffusion
The movement of molecules from a higher concentration to an area of lower concentration. It is a passive process
what are the functions of cell surface membranes
- controls what enters & leaves cells
- partially permeable
- substances move across by diffusion, osmosis and active transport
- allows cell communication
explain the function of phospholipids
phospholipids make up the phospholipid bi layer
explain the function of glycoproteins
glycoproteins are made up of extrinsic proteins and a carbohydrate branch, used for signalling
explain the function of glycolipids
made up of a phospholipid and a carbohydrate branch
explain the function of cholesterol
cholesterol gives the membrane stability/ keeps it rigid, despite the other components moving around
explain the function of protein channels
protein channels allow large, charged, polar molecules into the cell
Learn-
The basic structure of all cell membranes, including cell-surface membranes and the membranes around the cell organelles of eukaryotes, is the same.
The basic structure of all cell membranes, including cell-surface membranes and the membranes around the cell organelles of eukaryotes, is the same.
explain simple diffusion
Simple diffusion is a type of passive transport which is simply the unassisted movement from an area of high concentration to an area of low concentration
explain facilitated diffusion
Facilitated diffusion is a type of passive transport. Facilitated diffusion is like normal diffusion, except that it happens through special protein channels and carrier proteins.
explain active transport
the movement of molecules from a low concentration to a high concentration using energy from ATP & carrier molecules
What is Fick’s law
surface area x steepness
rate of diffusion= —————————————–
thickness of membrane
explain co-transport
the coupled transport of chemical substances across a cell membrane in which the energy required to move a substance against a concentration gradient
what factors affect rate of transfer across membrane
- surface area
- temperature
- diffusion distance
- number of channel proteins
- steepness of gradient
is -5kPa more or less concentrated than -70kPa
-5kPa is a dilute solution, but -70kPa is a highly concentrated solution
what happens when diffusion reaches equilibrium
the substances move back and forth across the membrane keeping the concentrations equal
why can’t water soluble molecules move through the phospholipid bi layer
the hydrophobic fatty acid tails
what’s the formula for surface area
L x H x faces
Is sodium in high or low concentration in the lumen
high concentration
is sodium in high or low concentration in the epithelial cell
low concentration
is sodium in high or low concentration in the bloodstream
low concentration
is glucose in high or low concentration in the epithelial cell
high glucose concentration
is glucose in high or low concentration in the bloodstream
low concentration
explain the movement of sodium from the lumen to the bloodstream
A low concentration of sodium is maintained in the epith
explain the movement of sodium from the lumen to the bloodstream
A low concentration of sodium is maintained in the epithelial cell by actively transporting it out of the cell and into the blood stream through a sodium potassium pump. This means that sodium can move with the concentration gradient into the epithelial cell, co-transporting glucose with it
explain the movement of glucose from the lumen to the bloodstream
Glucose is in low concentration in the lumen. Glucose moves into the epithelial cell, where it is in high concentration, through co-transportation with sodium. It leaves the cell through facilitated diffusion
how do ice crystals affect membrane permeability
ice crystals pierce the membrane and when they melt leave gaps for molecules to enter the cell
how do high temperatures affect membrane permeability
high temperatures cause the proteins to denature and
Define dynamic Equilibrium
Diffusion never completely stops but when it reaches equilibrium the molecules move back and forth, as there is no concentration gradient
Describe the relationship between size and surface area to volume ratio
As an object gets smaller the surface area to volume ratio gets bigger.
How does surface area to volume ratio affect diffusion
The larger the surface area to volume ration the greater the diffusion levels
