module 2.5 mr hill Flashcards
what are the 5 reasons why plasma membranes are essential
1-partially permeable (to allow particles to pass)
2-signalling to other cells
3-compartmenalizing organelles (forms a boundary of an organelle)
4-allows electrical signals to pass
5-provide attachment sites for enzymes etc…
draw the most basic structure ever of a plasma membrane
========== (double membrane)
what is the plasma membrane made out of
phospholipids
what is the glycocalyx
the combined layer of glycolipids and glycoproteins - carbohydrate groups on the exterior
what are glycoproteins
proteins with carbohydrates attached
what are glycolipids
lipids with carbohydrates attached
-phospholipid or lipid with chains of carbohydrate molecules
what is the plasma membrane held together by and what does this allow for
held by cholesterol-> maintains membrane fluidity
what are the 6 factors that affect rate of diffusion
temp, distance travelled, pressure, ph, conc., sa
what is equilibrium?
situations where concentrations are balanced and no net movement.
what’s a biological example of diffusion
gas exchange
what is diffusion
the net movement of molecules/substances from a high conc to a low conc down a concentration gradient
what can rapidly diffuse across a cell membrane
small non-polar molecules e.g C02 and O2
talk about facilitated diffusion
- charged particles (ions) cannot diffuse across a membrane, even if they are very small.
-if the molecule is to large or charged to diffuse across on its own…
it can diffuse if there is a specific transport protein (channel)
-with an addition of a protein that helps it out if the molecule is large, charged or both.
what are the two types of proteins (pm)
channel proteins and carrier proteins
channel proteins -state 2 points abt them
- form pores in the membrane
- many only let 1 type of molecule through
carrier proteins -state 2 points abt them
- molecules fit in at membrane +specific molecule fits into carrier e.g glucose
- protein changes shape to pass molecule through
solute?
any substance dissolved in a solvent
solvent?
any fluid which can dissolve a solute
solution?
A liquid that consists of a dissolved solute in a solvent
what’s osmosis
osmosis is the net movement/diffusion of water. it is the movement of water molecules from a region of high water potential to a region of low water potential, through a partially- permeable membrane.
water potential?
the tendency for water to move(diffuse). unit= kPa
hypotonic?
higher water potential outside the cell (water moves in)
hypertonic?
lower water potential outside the cell (water moves out the cell)
what happens when water moves into plant cell via osmosis
membrane pushes against wall.
TURGID
what happens when water moves into animal cell via osmosis
animal cell bursts open
CYTOLISED
what happens when water moves out plant cell
cell membrane pulls away from cell wall as water leaves.
the cell is PLASMOLYSED
-the tissue becomes FLACID
what happens when water moves out animal cell
animal cell shrinks and appears wrinkled
the cell is CRENATED
what is active transport used to do
used to move molecules and ions across a membrane against their concentration gradient
what does active transport require
- transport proteins( carrier proteins) (which require ATP to function)
what do transport proteins use ATP to make
to make a conformational change (change shape) to allow molecules to pass.
what 4 processes is active transport used in
- uptake of glucose and amino acids in the small intestine
- absorption of mineral ions by plant roots
- excretion of hydrogen ions and urea by kidneys
- excretion of sodium and potassium ions in neurones and muscle cells
what do cells that undertake active transport on a large scale have a lot of
many mitochondria
when is bulk transport used
when extremely large substances need to be moved across a cell membrane
what are the 2 types of bulk transport and what do they involve
endocytosis and exocytosis (both involve changes to membrane shape)
what is exocytosis
movement of volume out of cell
-vesicles fuse with plasma membrane and contents are released
what is endocytosis
bulk transport of material into a cell
what are the two processes within endocytosis
phagocytosis and pinocytosis
endocytosis: what’s phagocytosis
engulfing of SOLIDS
uses pseudopodia to surround and engulf target
endocytosis: what’s pinocytosis
- engulfing of LIQUIDS
what are examples of proteins that could be attached to carrier proteins
function as:
- enzymes
- antigens
- receptor sites for complimentary shaped signalling chemicals such as hormones
in neurones (nerve cells), what do the channel proteins and carrier proteins allow for
-entry and exit of ions to bring about the conduction of electrical impulses along their length.
what is the myelin sheath wrapped around in a neurone
its wrapped around the axon
what does the plasma membrane of white blood cells contain
special protein receptors that enable them to recognise the antigens on foreign cells.
what do root hair cells have many of
- many carrier proteins to actively transport nitrate ions from soil to roots
can fat-soluble molecules such as steroid hormones diffuse across the lipid bilayer
-yes as they can dissolve in the lipid bilayer (dont need a channel protein)
what specific water channels allow water to move across cell membrane
-specific channel proteins called aquaporins
how is conc across a cell membrane obtained?
- many molecules entering the cells then pass into organelles and are used for metabolic reactions
(o2 for mitochondria and co2 for chloroplasts)
5 factors that affect rate of simple diffusion
- temperature ( more k energy)
- diffusion distance (thicker membrane=slower)
- sa (more diffusion can take place across a larger sa)
- size of diffusing molecules
- conc gradient
how is glucose moved through phospholipid bilayer
via a transmembrane carrier protein (its a large molecule)
what do neurone plasma membranes have many channels specific for
-sodium ions or potassium ions
what do epithelial cells have many channels specific for
-chloride ions
