Plasma of membrane and movement of substances

Question 1

what does the plasma membrane do?

Answer 1

Controls movement of substances between the extracellular and intracellular fluid.
Maintains environment fo cell.
Controls transport.
Involved in recognition.

Question 2

fluid mosaic model definition?

Answer 2

Two layers of phospholipids

Has other components dotted throughout.

Question 3

what is the structure of the phospholipid bilayer?

Answer 3

Hydrophilic head that contains phosphate group and glycerol
Hydrophobic fatty acid tails (saturated- straight or unsaturated- bent)
Tails point in together, away from water

Question 4

what does the fluidity of the membrane mean?

Answer 4

components are free to move

Question 5

what does fluidity affect?

Answer 5

Permeability

Moving proteins affect where they can carry out their function

Question 6

what affects fluidity?

Answer 6

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

Question 7

what is the mosaic nature?

Answer 7

Where the proteins are located changes the mosaic pattern

Question 8

how are the membrane proteins located (mosaic nature)?

Answer 8

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

Question 9

what are the two types of membrane proteins? and a description of each?

Answer 9

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

Question 10

carbohydrates in the membrane? what do they form? where are they? what are the involved in?

Answer 10

Form glycoproteins (join to proteins) or glycolipids (join to phospholipids)
Outer surface
Recognition between cells
Adhesion between cells
Recognition of antibodies, hormones and viruses

Question 11

membranes in organelles?

Answer 11

Similar to plasma membrane, allowing the to fuse (vesicles and passing materials from one organelle to another)

Question 12

what is compartmentalisation? what does it allow?

Answer 12

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).

Question 13

chemical properties of oxygen and carbon dioxide? permeability?

Answer 13

small, uncharged

permeable

Question 14

chemical properties of steroids, alcohol and chloroform? permeability?

Answer 14

lipid-soluble, non-polar

permeable

Question 15

chemical properties of water and urea? permeability?

Answer 15

small, polar

permeable or selectively permeable

Question 16

chemical properties of potassium ions, sodium ions and chloride ions? permeability?

Answer 16

small ions

non-permeable

Question 17

amino acid, glucose chemical properties? permeability?

Answer 17

large, polar, water-soluble

non-permeable

Question 18

permeability of hydrophobic and hydrophilic substances?

Answer 18

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

Question 19

what does passive transport involved? what are the types?

Answer 19

no energy

diffusion
osmosis
facilitated diffusion

Question 20

what is diffusion?

Answer 20

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

Question 21

what is osmosis? what force moved it?

Answer 21

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.

Question 22

isotonic solution?

Answer 22

equal concentrations of solutes.

Question 23

hypertonic solution?

Answer 23

the solution with the higher concentration of solute.

Question 24

hypotonic solution?

Answer 24

the solution with the lower concentration of solute (more water).

Question 25

crenated?

Answer 25

shrivelled animal cells

Question 26

lysed?

Answer 26

burst animal cell

Question 27

plasmolyse?

Answer 27

cytoplasm shrinks from cell wall in a plant

process of losing water

Question 28

flaccid?

Answer 28

cytoplasm shrinks from cell wall in a plant

Question 29

turgid?

Answer 29

fat, full plant cell

Question 30

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?

Answer 30

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.

Question 31

what are the 3 factors that affect rate of diffusion?

Answer 31

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

Question 32

what is active transport? what are the types? what are the 3 elements?

Answer 32

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

Question 33

what is bulk transport?

Answer 33

Large molecules (proteins etc.), wastes etc ate moved this way
Needs energy

Question 34

how is proteins synthesised and then exported?

Answer 34

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

Question 35

what is endocytosis and what are the three types?

Answer 35

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.