biolgical membranes Flashcards
what does the cell surface membrane consist off
the phospholipid bilayer
what are the two types of transport proteins
carrier and channel proteins
what are intrinsic proteins
proteins, that are fully embedded in the membrane from one side to the other.
why do intrinsic proteins, have hydrophobic amino acids on the outside surface on the protein
so that they can interact with the hydrophobic fatty acid trails in the phospholipid bilayer
name 2 intrinsic proteins
channel proteins and carrier proteins
what do channel proteins do
they allow water soluble molecules and ions to diffuse through
what do carrier proteins do
they can change (adapted) their shape or position, to transfer molecules or ions form one side of the membrane to the other
what are extrinsic proteins
they do not span the membrane, instead they are found on one side of the membrane, sometimes they may be attached to intrinsic proteins
what are some of the functions of extrinsic proteins
- structural role
- act as enzymes
- may be receptors, for other molecules (such as hormones)
what is the role of glycoproteins
- allow cells to attach to each other
- play a role in the immune presenting antigens to T cells
- act as receptors for hormones
what is the role of glycolipids
- often used, when cells come in contact with each other
- the glycolipids on one cell, can be recognised by the glycolipids of another cell
- they can also act as antigens
what are glycoproteins
proteins with a chain or carbohydrate molecules attached
what are glycolipids
lipids or phospholipids with a chain or carbohydrate molecules attached
what is the role of cholesterol in the cell membrane
to regulate membrane fluidity and mechanical strength
what is the fluid mosaic model
fluid; the components , can move around within the cell membrane, a mosaic of proteins, model; a way of visualising something you can’t see
what is the meaning of hydrophilic
water loving
what is the meaning of hydrophobic
water hating
what is glycocalyx
carbohydrate groups, on the exterior of the membrane
what is diffusion
the net movement, of particles from an area of higher concentration to an area of lower concentration (down their concentration gradient).
why is diffusion a passive process
because it does not require ATP (energy)
what is meant, by concentration gradient
a steep concentration gradient, involves a large difference in concentration (from high to low), thus causing rapid diffusion
define the term facilitated diffusion
the net movement of particles, down their concentration gradient across a partially permeable cell membrane, via carrier or channel proteins.
what does metabolic energy mean
the energy, that is released by respiration
what are the factors, that influence the rate of diffusion in and out of the cells (state 6)
- the concentration gradient
- particle charge / size
- temperature
- surface area
- distance
- channels / carriers ( facilitated diffusion)
what is the key thing to remember about carrier proteins
they have a binding site, for a specific chemical, when the chemical binds, it causes the tertiary structure of the protein to change, this change brings the chemical across the membrane, then they are released
what is the key thing to remember about channel proteins
- they are selective, as to which chemicals can pass through them
- some proteins channels are always open, some are only open due to a certain trigger.
what is osmosis
the net movement of water, from an area of higher water potential to an area of lower water potential across a partially permeable membrane
what are phospholipids
main fabric of the membrane, they act as a barrier to most molecules
what is facilitated diffusion used for
- to transport large and polar molecules, or charged molecules across the cell membrane#
- this is necessary because polar and charged molecules, cannot interact with the hydrophobic phospholipid tails in the bilayer.
how could a cell control which substances can or can’t enter using channel and carrier proteins
- different channel or carrier proteins, are specific to certain membranes. meaning that only certain molecules, can go through certain membranes, due to the fact that they are specific to each other.
effect of temperature on diffusion distance
diffusion, occurs due to the random movement of particles, resulting in a net movement from high to low concentration. When the temperature increases, particles have more kinetic energy, so they move and collide at a faster rate. Therefore the rate of diffusion increases.
effect of concentration gradient on diffusion
- the steeper the conc gradient, the greater the difference in conc of particles between two areas.
- the net movement of particles, from area to the other, will therefore be larger in a given amount of time (faster diffusion rate)
- if conc gradient, is not maintained, then equilibrium is reached and diffusion stops.
effects of distance on diffusion
- very thin specialised cells, to increase diffusion rate.
- e.g. the alveoli, is lined with squamous cells, allowing for a fast exchange rate, between the capillaries.
effect of surface area on diffusion
- the greater the surface area, the higher the number of particles, that can diffuse across the membrane.
what is Fick’s law
surface area x difference in concentration/ thickness of exchange surface.`
what can we use as a practical example, of a partially permeable membrane
visking tubing
what is water potential
water potential, is a measure of the tendency of water molecules, to move from one area to another area and describes the pressure created by these water molecules; the more dilute a solution, the higher (less negative) the water potential
what do we measure water potential in
kPa
what is active transport
Active transport is the movement of molecules across a biological membrane from an area of lower concentration to an area of higher concentration, against the concentration gradient, with the assistance of energy (ATP)
what is bulk transport
active transport, for big molecules (requires ATP). in addition, it causes the membrane to change shape in order to engulf and release the molecule that it is transporting.
how do carrier proteins, work in active transport
- specific shape for the molecule to be transported
- binding site for ATP
- energy, changes the protein’s conformation
