biolgical membranes

Question 1

what does the cell surface membrane consist off

Answer 1

the phospholipid bilayer

Question 2

what are the two types of transport proteins

Answer 2

carrier and channel proteins

Question 3

what are intrinsic proteins

Answer 3

proteins, that are fully embedded in the membrane from one side to the other.

Question 4

why do intrinsic proteins, have hydrophobic amino acids on the outside surface on the protein

Answer 4

so that they can interact with the hydrophobic fatty acid trails in the phospholipid bilayer

Question 5

name 2 intrinsic proteins

Answer 5

channel proteins and carrier proteins

Question 6

what do channel proteins do

Answer 6

they allow water soluble molecules and ions to diffuse through

Question 7

what do carrier proteins do

Answer 7

they can change (adapted) their shape or position, to transfer molecules or ions form one side of the membrane to the other

Question 8

what are extrinsic proteins

Answer 8

they do not span the membrane, instead they are found on one side of the membrane, sometimes they may be attached to intrinsic proteins

Question 9

what are some of the functions of extrinsic proteins

Answer 9

• structural role
• act as enzymes
• may be receptors, for other molecules (such as hormones)

Question 10

what is the role of glycoproteins

Answer 10

• allow cells to attach to each other
• play a role in the immune presenting antigens to T cells
• act as receptors for hormones

Question 11

what is the role of glycolipids

Answer 11

• 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

Question 12

what are glycoproteins

Answer 12

proteins with a chain or carbohydrate molecules attached

Question 13

what are glycolipids

Answer 13

lipids or phospholipids with a chain or carbohydrate molecules attached

Question 14

what is the role of cholesterol in the cell membrane

Answer 14

to regulate membrane fluidity and mechanical strength

Question 15

what is the fluid mosaic model

Answer 15

fluid; the components , can move around within the cell membrane, a mosaic of proteins, model; a way of visualising something you can’t see

Question 16

what is the meaning of hydrophilic

Answer 16

water loving

Question 17

what is the meaning of hydrophobic

Answer 17

water hating

Question 18

what is glycocalyx

Answer 18

carbohydrate groups, on the exterior of the membrane

Question 19

what is diffusion

Answer 19

the net movement, of particles from an area of higher concentration to an area of lower concentration (down their concentration gradient).

Question 20

why is diffusion a passive process

Answer 20

because it does not require ATP (energy)

Question 21

what is meant, by concentration gradient

Answer 21

a steep concentration gradient, involves a large difference in concentration (from high to low), thus causing rapid diffusion

Question 22

define the term facilitated diffusion

Answer 22

the net movement of particles, down their concentration gradient across a partially permeable cell membrane, via carrier or channel proteins.

Question 23

what does metabolic energy mean

Answer 23

the energy, that is released by respiration

Question 24

what are the factors, that influence the rate of diffusion in and out of the cells (state 6)

Answer 24

• the concentration gradient
• particle charge / size
• temperature
• surface area
• distance
• channels / carriers ( facilitated diffusion)

Question 25

what is the key thing to remember about carrier proteins

Answer 25

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

Question 26

what is the key thing to remember about channel proteins

Answer 26

• 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.

Question 27

what is osmosis

Answer 27

the net movement of water, from an area of higher water potential to an area of lower water potential across a partially permeable membrane

Question 28

what are phospholipids

Answer 28

main fabric of the membrane, they act as a barrier to most molecules

Question 29

what is facilitated diffusion used for

Answer 29

• 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.

Question 30

how could a cell control which substances can or can’t enter using channel and carrier proteins

Answer 30

• 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.

Question 31

effect of temperature on diffusion distance

Answer 31

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.

Question 32

effect of concentration gradient on diffusion

Answer 32

• 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.

Question 33

effects of distance on diffusion

Answer 33

• 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.

Question 34

effect of surface area on diffusion

Answer 34

• the greater the surface area, the higher the number of particles, that can diffuse across the membrane.

Question 35

what is Fick’s law

Answer 35

surface area x difference in concentration/ thickness of exchange surface.`

Question 36

what can we use as a practical example, of a partially permeable membrane

Answer 36

visking tubing

Question 37

what is water potential

Answer 37

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

Question 38

what do we measure water potential in

Answer 38

kPa

Question 39

what is active transport

Answer 39

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)

Question 40

what is bulk transport

Answer 40

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.

Question 41

how do carrier proteins, work in active transport

Answer 41

• specific shape for the molecule to be transported
• binding site for ATP
• energy, changes the protein’s conformation