the plasma membrane (week 11) Flashcards
(27 cards)
what is the plasma membrane
a selectively permeable barrier that surrounds the cell and controls what enters and exits
what is the function of the membrane
- organises the chemical activities of cells
- outer membrane: forms a boundary
- inner membrane: provides structural order
what is the plasma membrane made of?
a phospholipid bilayer with embedded proteins
what does semi-permeable mean?
only certain molecules can pass through the membrane.
selective permeability: the membrane’s ability to allow some substances across a space/membrane
which molecules pass easily through the plasma membrane?
small, uncharged molecules like oxygen and carbon dioxide
what is the fluid mosaic mdoel?
a model describing the flexible arrangement of phospholipids and proteins in the membrane
mix of molecules that move and rearrange themselves, like a mosaic
- fluid because most proteins and phospholipid molecules can move (laterally)
- fluid: the constant movement and flexibility of the phospholipids and proteins within the membrane
- mosaic: highlights the varity of molecules embedded within the lipid bilayer.
what are peripheral proteins?
proteins attached to the surface of the membrane
what are integral proteins?
proteins that span the entire membrane
what are lipid anchored proteins?
they are COVALENTLY attached to lipids, which are embedded in the membrane
what is the difference between glycoprotein and glycolipid?
glycoprotein: protein with carbohydrate attached
glycolipid: lipid with carbohydrate attached
what is diffusion?
the movement of particles from regions of high concentration to low concentration
- molecules become evenly spaced
what does diffusion rate depend on?
- concentration of molecules (higher = faster)
- size of molecules (smaller = faster)
- speed of molecular movement (temperature and state)
what is a concentration gradient
a difference in concentration of a substance across a space or membrane
what is osmosis?
the diffusion of water from an area of low solute concentration (high water concentration) to an area of high solute concentration (low water concentration) across a semipermeable membrane
what happens to a cell in a hypertonic solution
- water LEAVES the cell
- causes it to shrink, because the solution has a higher solute concentration than the cell
what happens to a cell in a hypotonic solution?
- water ENTERS the cell
- causes it to swell and potentially burst, because the solution has a lower solute concentration than the cell
what happens to a cell in a isotonic solution?
- water moves IN AND OUT at EQUAL rates
- cell stays the same size, because the solute concentration is equal inside and outside the cell
what is passive transport - (transport/diffusion)
no energy is required for particles to move in and out of the cell
what is facilitated transport - (transport/diffusion)
a type of passive transport (no energy required)
- embedded proteins act as tunnels for particles to move across membranes
what is active transport?
the movement of substances AGAINST a concentration gradient, requiring energy (ATP), and carrier proteins
- moving from low concentration to high concentration
what is the main difference between diffusion and active transport?
diffusion: passive and moves down the gradient
active: requires energy and moves against the gradient
what is endocytosis?
what are the three types?
a form of active transport:
- group of processes that bring macromolecules, large particles, small molecules, small cells, into eukaryotic cells
- three types: phagocytosis, pinocytosis, receptor-mediated
what is phagocytosis?
“cell eating”: the cell engulfs LARGE, SOLID particles, e.g bacteria, debris, into vesicles
- form of endocytosis, which is a form of active transport (requires energy)
what is pinocytosis?
“cell drinking”: the cell takes in SMALL droplets of LIQUID and dissolved substances into vesicles
- form of endocytosis, which is a form of active transport (requires energy)
