Plasma of membrane and movement of substances Flashcards
what does the plasma membrane do?
Controls movement of substances between the extracellular and intracellular fluid.
Maintains environment fo cell.
Controls transport.
Involved in recognition.
fluid mosaic model definition?
Two layers of phospholipids
Has other components dotted throughout.
what is the structure of the phospholipid bilayer?
Hydrophilic head that contains phosphate group and glycerol
Hydrophobic fatty acid tails (saturated- straight or unsaturated- bent)
Tails point in together, away from water
what does the fluidity of the membrane mean?
components are free to move
what does fluidity affect?
Permeability
Moving proteins affect where they can carry out their function
what affects fluidity?
Phospholipid composition and structure
Saturated fatty acid tails- less fluid. Being straight allows more to pack in
Temperature
Temperature increases, fluidity increases as phospholipids become less closely packed
as it decreases, saturated fatty acids solidity- less so if there are unsaturated ones as the kinks keep them apart
Cholesterol
Prevents phospholipids from packing too close together
At high temperatures, it restricts movement, decreasing fluidity
At lower temperatures it prevents them from getting too close and solidifying
what is the mosaic nature?
Where the proteins are located changes the mosaic pattern
how are the membrane proteins located (mosaic nature)?
Clusters in groups in order to carry out similar functions or be part of a biochemical pathway (long chains of chemical reactions)
Distributed randomly
Can be free to move (not attached to molecules)
Can be attached to the cytoskeleton on the interior or extracellular matrix (structure that gives support to surrounding cells) so that movement is restricted to certain locations
what are the two types of membrane proteins? and a description of each?
Integral proteins:
permanent and span both layers of the bilayer (transmembrane)
Hydrophobic region is with the tails (attract each other)
Hydrophilic exterior may form water-filled channels through which various materials may be moved
Act as transport channels
Function as enzymes
Involved in signal transduction
Function in cell to cell recognition
Connects cells to other cells
Act as attachments to the extracellular matrix and cytoskeleton
Peripheral proteins:
Temporary
Not embedded
Bind to integral proteins or penetrate into the surface of the membrane
Function as enzymes, receptors, structural attachment points of cellular recognition sites
carbohydrates in the membrane? what do they form? where are they? what are the involved in?
Form glycoproteins (join to proteins) or glycolipids (join to phospholipids)
Outer surface
Recognition between cells
Adhesion between cells
Recognition of antibodies, hormones and viruses
membranes in organelles?
Similar to plasma membrane, allowing the to fuse (vesicles and passing materials from one organelle to another)
what is compartmentalisation? what does it allow?
Optimises efficiency by grouping enzymes and reactants in high concentrations and in the right conditions
Enables many reactions o occur at once
Decreases vulnerability to environmental change (organelles are less affected than cytosol).
chemical properties of oxygen and carbon dioxide? permeability?
small, uncharged
permeable
chemical properties of steroids, alcohol and chloroform? permeability?
lipid-soluble, non-polar
permeable
chemical properties of water and urea? permeability?
small, polar
permeable or selectively permeable
chemical properties of potassium ions, sodium ions and chloride ions? permeability?
small ions
non-permeable
amino acid, glucose chemical properties? permeability?
large, polar, water-soluble
non-permeable
permeability of hydrophobic and hydrophilic substances?
Most hydrophobic molecules can dissolve in the interior of the lipid bilayer of the plasma membrane and move through.
Water soluble substances and ions cannot penetrate as they have large shell of water
what does passive transport involved? what are the types?
no energy
diffusion
osmosis
facilitated diffusion
what is diffusion?
Solute particles move from an area of high concentration to an area of low concentration, down a concentration gradient.
Substances must be permeable
Net movement as they move in both directions
Eventually creates equal environments
what is osmosis? what force moved it?
The net diffusion of water through a semipermeable membrane from a diluted solution to a concentrated solution down water’s concentration gradient (osmotic gradient)
Moved by osmotic pressure.
isotonic solution?
equal concentrations of solutes.
hypertonic solution?
the solution with the higher concentration of solute.
hypotonic solution?
the solution with the lower concentration of solute (more water).
crenated?
shrivelled animal cells
lysed?
burst animal cell
plasmolyse?
cytoplasm shrinks from cell wall in a plant
process of losing water
flaccid?
cytoplasm shrinks from cell wall in a plant
turgid?
fat, full plant cell
what is facilitated diffusion? how rapid is it? what can happen to the transport proteins involved? how may transport be inhibited? is energy needed? what does it allow to move? what are the proteins involved?
Membrane transport proteins are specific for certain particles, so transport is selective
More rapid than simple diffusion
Transport proteins can be saturated (fully occupied) as concentration of a substance increases
The transport of one particle may be inhibited by the presence of another that uses the same protein
No energy is required- downhill gradient
Allow polar molecules and ions to move
Channel proteins: pores that open and close for specific molecules.
Carrier proteins: bind to specific molecules being transport, changing its shape.
what are the 3 factors that affect rate of diffusion?
concentration: greater the concentration gradient difference, the faster
Temperature: higher the temperature, the higher the rate of diffusion (molecules move faster)
Particle size: small particles diffuse faster
what is active transport? what are the types? what are the 3 elements?
Needs energy
Against the gradient
Selectivity: some substances are transported and others are not
saturation: no increase in the rate of transfer when all transport proteins are open
Competitive inhibition: one substance can inhibit the transport of another that uses the same protein
bulk transport
what is bulk transport?
Large molecules (proteins etc.), wastes etc ate moved this way Needs energy
how is proteins synthesised and then exported?
Secretory proteins are proteins that are exported by exocytosis.
They must be synthesised and modified first
Ribosomes and the endoplasmic reticulum
Produced by ribosome, polypeptide chain is inserted into the lumen (fluid-filled space between RER membranes) through a pore.
Transported in tubules of RER where it is modified
At the end, they are wrapped in membranes to form vesicles (ones that move are called transport vesicles)
RER also produced transmembrane proteins
Golgi apparatus
Transport vesicles from RER fuse with cis face (near ER)
Protein moves from one cisternae to the next by vesicles
Is is modified as it goes
May add sugars to make carbohydrates etc.
Secretory vesicles take the finished product from the trans face to the plasma membrane
May be stored in the Golgi until secretion is needed
Exocytosis
Secretory vesicle fuses with the membrane
The contents are released out of the cell
The vesicle becomes a part of the membrane
Membrane is constantly using vesicles from exocytosis and making new ones for endocytosis
Exocytosis also releases waste from lysosomes
what is endocytosis and what are the three types?
Takes materials in by forming vesicles
Membrane sinks inwards to form a pocket and then it pinches off to form a vesicle
Phagocytosis: engulfs a solid by wrapping pseudopodia around it forming a phagosome. The material wi;; be digested with a lysosome.
Pinocytosis: engulfs liquids that contain dissolved molecules.
Receptor-mediated endocytosis: a type of pinocytosis that engulfs specific substances. Protein receptors located on the surface of the plasma membrane respond to particular molecules binding to the molecule and then triggering the engulfment of the substance into the cell.
