membrane Flashcards
what are the components of a cell membrane
phospholipid bilayer, proteins (integral and peripheral), carbohydrates (glycoprotein and glycolipid), cholesterol, extracellular and intercellular fluid.
what arrangement is the membrane and why
fluid mosaic model because the bilayer can shift position (fluidity) and is embedded with other molecules (mosaic)
hydrophilic and hydrophobic parts of the membrane
tails - phobic, heads - philic
what is the bilayer made of
lipids (fats)
what shapes have a larger SA:V
smaller and less spherical (flat)
what is the cell membrane made out of
phospholipid bilayer, integral and peripheral proteins, channel proteins, glyco protein and glycolipids ( with carbohydrates), cholesterol
what is a glycoprotein
the balls of carbohydrates are connected to a protein
what is a glycolipid
the balls of carbohydrates are connected to a head
inside and outside of cell
intercellular and extracellular fluid
4 functions of the plasma membrane
- allows substances in and out of the cell 2. provides a boundary around cell 3. prevents substances from entering the cell 4. holds all cell contents
diffusion definition
the passive movement of particles from an area with higher concentration to an area with lower concentration
when does diffusion stop
when equilibrium is reached after which no net movement will occur
4 things that effect diffusion rates
molecular size, presence of net charge, solubility in liquid solvents, direction of concentration gradient
how does molecular size impact diffusion
smaller molecules like water 3-5 atoms can easily pass through bigger like gluecose cannot
how does net charge impact diffusion
uncharged and non-polar can diffuse freely but charged cannot as heads stop them
how does solubility in lipid solvents impact diffusion
lipids and lipid soluble molecules can diffuse freely as they can combine with the tails
direction of concentration gradient impact diffusion
molecules that can diffuse will go down the concentration gradient
4 ways a substance can move across a membrane
simple diffusion and osmosis, facilitated diffusion, active transport and bulk transport
what is facilitated diffusion
still passive and occurs with large molecules like gluecose using a channel or carrier protein
what is osmosis
passive movement of water molecules from a higher water concentration and lower solute concentration to an area with a lower water and higher solute concentration across a semi-permeable membrane
when does osmosis stop
when equilibrium is reached and there will be no further NET movement
when a solution has a higher concentration of water
hypotonic
when a solution has a higher concentration of solutes
hypertonic
when a solution has a higher concentration of solutes
hypertonic
when water moves from the solution inot the cell
cytolysis
when a solution has a higher concentration of solutes than another
hypertonic
when water moves out of the cell inot the solution
plasmolysis
when the concentration of solutes is equal in the cell and solution
isotonic
animal and plant cells when a solution is hypotonic
lysed and turgid (normal)
animal and plant cells when a solution is hypertonic
shriveled and plasmolyzed
animal and plant cells when a solution is isotonic
normal and flaccid
active transport
movement of substances against the concentration gradient which requires the expenditure of energy in the form of ATP
how are substances transported in active transport
integral proteins which act as ‘carriers’ or ‘pumps’
why is active transport needed
when there are big differences between internal and external concentrations or charged particles because they cannot diffuse through the membrane
two types of bulk transport
exocytosis and endocytosis
exocytosis
proteins are modified and packaged into vesicles by the golgi body and are sent out of the cell
endocytosis
the vesticles are pinched of plasma membrane in either phagocytosis or pinocytosis
phagocytosis
when solid matter is englufed
pinocytosis
when substances engulfed are in solution
what molecules can diffuse directly across the membrane
allows for passive diffusion of hydrophobic or non-polar molecules. These are either small in size or lipid soluble and pass through the gaps between the phospholipids. eg water, oxygen, carbon-dioxide, urea, alcohol.
what substances cannot diffuse across the membrane freely
Water soluble, polar substances move across the membrane by diffusion or active transport, but this occurs through protein channels. eg amino acids, nucleic acids, carbohydrates, proteins and ions (see next slide)
what allows the membrane to have a fluid nature
the presence of cholersterol
what does cholersterol do in the membrane
Cholesterol also gives the membrane stability. It stops the membrane from being rigid when temperatures are low and from falling apart when temperatures are too high by reducing the permeability of small water-soluble molecules.
