C5 Plasma membrane Flashcards
If you place an animal cell in a sugar concentrated solution what happens ?
CRENATED
shrinks . water moves out down water potential gradient
If you place an animal cell in pure water what happens
CYTOLYSED
burst - water moves in down the water potential gradient
If you place a plant cell in a concentrated sugar solution what happens?
PLASMOLYSED
cell membrane pulls away - water leave the cell down the water potential gradient
if you place a plant cell in pure water what happens
The cell becomes turgid and the cellulose cell wall swells
water moves into the cell down the water potential gradient
how do small non polar substances pass into the plasma membrane
diffuse (through membrane / phospholipid bilayer);
how do large substances pass into the plasma membrane
transport / carrier, proteins;
active transport
endocytosis / phagocytosis / described;
how do polar substances enter the plasma membrane
through, pore / channel, proteins;
(using), transport / carrier, proteins;
general – must be used in correct context, each once only
ref to facilitated diffusion;
Outline the roles of membranes at the surface of cells and within cells (9)
at surface
separate cell from environment;
control, entry/exit (of molecules/ions/suitable substance);
A selective/partial R semi-permeable
use of phospholipid layer (in allowing or preventing passage) of
suitable example;
reference to facilitated diffusion;
reference to active uptake; R channel protein
reference phagocytosis/pinocytosis/endocytosis/exocytosis;
cell recognition/cell surface antigens;
cell to cell attachment;
receptor (for hormones/neurotransmitters etc.);
microvilli increase surface area of cell
enzyme attachment
within a cell
compartmentalise/surrounds organelles;
prevents disruption of, reactions/process; A reaction more efficient
e.g. reaction/process, and organelle;
reactions take place on membranes; A named example of membrane
enzymes attached to membranes; A named example
isolates/separates, DNA/nucleus;
(nuclear pore) permits RNA to leave nucleus;
(forms) ER/(Golgi) vesicles/lysosomes/other named organelle;
(not the same e.g. as W3 or W6)
attachment of ribosomes;
intracellular transport;
protects cells from contents of lysosomes;
(tonoplast) surrounds/controls content of, vacuole;
increases (internal) surface area of organelle
attachment of pigments
formation of mesosomes
site of chemical reactions
within an organelle
Allows for concentration gradients to be established and maintained
embedding of enzymes into the membrane
What’s the main role of plasma membranes
allow the transfer of substances in and out of a cell
What is cell signalling
Communication between cells
to work together
to trigger a response
Why do phospholipids arrange themselves in a bilayer at the cell surface
Hydrophilic heads are pointed outwards towards the water
Hydrophobic tails are pointed inwards.
There’s water outside the cell in the extracellular fluid and inside the cell in the cytoplasm
What are the functions of glycolipids/glycoproteins
Cell recognition
cell signalling
act as antigens
act as a receptor
allow cells to bind - adhesion
Describe the movement of substances across the cell membrane - how’s its affected by the structure
Small non polar ions can diffuse
Carrier proteins -active transport OR facilitated diffusion large polar substances ( changes shape depending on substance entering)
Channel proteins - Facilitated diffusion of polar substances
Cholesterol - regulate fluidity
More extrinsic proteins the more movement.
Surface area of the membrane determined the movement
What 3 factors affect the permeability of a membrane
Heat
Ethanol
Detergents
How does an increase in heat affect the permeability of the membrane
Increased temperature = more kinetic energy within phospholipids
Causes gaps to appear = more permeable
if the temperatures too high then proteins in the membrane will denature= increasing permeability
