Text book Biological membranes Flashcards
Hydrophilic amino acids
So that the hydrophilic amino acids are in contact with the polar water that is in the channels, allowing soluble materials to pass through
Neurone axon vs mylein sheath
more protein in the neurone axon membrane than in the myeline sheath. Axons require carrier proteins in order that passage of ions into and out of cells can transmit electrical impulses, whereas the myelin sheath is insulating.
passive
It is not using cellular/metabolic/ATP energy/energy from respira
Affect the rate of osmosis
Size of molecule – osmosis applies only to water, and the size of water molecules is constant
Surface area of membrane – the greater the surface area, the more water molecules can pass across
Thickness of membrane – the thicker the membrane (such as in the case of a double membrane/envelope of some organelles), the slower the rate of osmosis
Affects the rate of diffusion
Concentration gradient – the steeper it is the faster the diffusion
Diffusion distance/thickness of membrane – the greater the distance/thicker the membrane, the slower the rate of diffusion
Surface area – the greater it is, the faster the rate of diffusion Size of molecule – smaller molecules diffuse faster
Temperature – increased temperature increases the rate of diffusion, as molecules have more kinetic energy.
How does the cellulose cell wall stop it from bursting
plant cell wall is rigid and strong – when turgid the cell wall exerts force on the cell wall and stops it from undergoing further osmosis
Definitions of:
Plasmolysis/crenation/lysis/turgid/flaccid
Plasmolysis – shrinkage of the plant cell due to loss of water by osmosis
Crenation – shrinkage of animal cell due to loss of water from osmosis
lysis – bursting of the animal cell due to uptake of too much water
Turgid – bloated cell
Flaccid plant tissue in which plant cells are plasmolylsed
How do potassium and chloride ions pass from the cytoplasm into the vacuole
7) Potassium ions by diffusion down the concentration gradient; probably facilitated diffusion through channel protein in tonoplast membrane (membrane enclosing vacuole). Chloride ions by active transport; against concentration gradient; use of protein carriers in tonoplast/vacuole membrane
How species such as algae are able to survive in strong sugar solutions?
Such algae actively transport in salts/ions; to reduce their water potential; so there is no gradient across their membranes and no loss of water from cytoplasm/vacuole
What influences a molecules ability to pass through the plasma membrane
Size; lipid solubility; polarity/charge distribution
Why transport across a membrane is so important
To remove toxic waste from metabolism;
to obtain oxygen for aerobic respiration;
to obtain amino acids for making proteins;
to obtain glucose for respiration;
to obtain lipids for making membranes;
to obtain vitamins/minerals.
