Membranes + Transport Flashcards
What are the 3 main functions of a plasma membrane?
-control the transport of substances in and out of the cell.
-To act as a receptor site to recognise chemicals which need to enter the cell or organelle.
-To separate off the cell from the environment
What type of lipid is found in cell membranes?
Phospholipids
What does it look like when phospholipids are arranged in a bilayer?
.
Diffusion and osmosis are passive processes what does this mean
Do not require energy in the form of ATP
What is simple diffusion?
Where molecules that are small enough and/or non polar can diffuse rapidly across the phospholipid bilayer
What is the definition of diffusion?
Movement of substances from a region of their higher concentration to a ego on of their lower concentration- movement of molecules down a concentration gradient.
What is dynamic equilibrium?
Where the particles are evenly spread, although still moving
What factors affect the rate of diffusion?
-surface area
-thickness of exchange surface
-concentration gradient
-size of diffusing molecule
-temperature
-water solubility/polarity
What is facilitated diffusion?
helps molecules diffuse through the membranes. requires channel adn carrier proteins.
What does a graph for simple diffusion look like?
.
Why does the graph on facilitated diffusion level off?
As all of the carrier proteins are occupied at any one time. Number of carrier/channel proteins are limiting.
What is osmosis?
the movement of water molecules from an area of high water concentration to an area of low water concentration through a partially permeable membrane.
What is active transport?
-movement against a concentration gradient.
-requires energy
-needs specific protein caries/pumps
-moves charges polar molecules
-not passive
What is exocytosis?
Exporting material in vesicles
What does facilitated diffusion diffuse?
Moves charges/ polar/ hydrophobic substances (channels for ions; carriers for other.)
What is a hypotonic solution?
A dilute solution or pure water will have a higher concentration than the cell so water enters the cell by osmosis. the cell swells and eventually bursts (osmotic lysis)
Membranes are partially permeable what does this mean?
They do not let water-soluble, charges or polar substances pass through easily and this is why the cell-surface membrane acts as an effective barrier to separate the cell from its environment.
What does fluid mosaic mean?
Fluid- molecules can move around
Mosaic-different types of molecules
What is a glycolipid?
these are made up of a carbohydrate covalently bonded to a lipid.
What does a graph for facilitated diffusion look like?
.
What is endocytosis?
The process of importing material in vesicles.
What is a bilayer?
Acts as a barrier to polar/water-voluble/large molecules.
What is a glycoprotein?
Short branching carbohydrate chains attached to proteins in the membrane.
What is the function of a glycoprotein?
Acts as receptors for hormones and neurotransmitters or antigens
