Cell Membranes

Question 1

5 Roles of Membranes

Answer 1

Separate contents of cells from their environment.
Separate the different organelles from each other.
Facilitates the exchange of substances between the cell and its environment (Selective permeability)
Endocytosis and Exocytosis
Cell signalling using glycolipid.

Question 2

Compartmentalization

Answer 2

Formation of separate membrane-bound areas in a cell.
Separate contents of cells from their environment.
Separate the different organelles from each other.

Question 3

Pros of Compartmentalisation

Answer 3

Metabolic processes contain many different and mostly incompatible reactions that require unique conditions.
Compartmentalization allows for each unique condition required for cellular reactions.

Question 4

Partially Permeable

Answer 4

A membrane that allows some (selective) substances to cross but not others.

Question 5

Cell Signalling

Answer 5

A complex system of intercellular identification and communication.

Question 6

larger surface area increases or decreases rate of diffusion?

Answer 6

increases

Question 7

Larger concentration difference increases or decreases rate of diffusion?

Answer 7

increases

Question 8

larger distance for particles to travel increases or decreases rate of diffusion?

Answer 8

decreases

Question 9

What is Brownian motion?

Answer 9

The constant random motion of fluids

Question 10

Define diffusion

Answer 10

The NET movement of particles from where they are at a higher to where they are at a lower concentration

Question 11

lower temperature increases or decreases rate of diffusion? and why

Answer 11

lowers - at a lower temperature the lower the kinetic energy of particles, and therefore speed so it takes longer for particle to reach equilibrium. At higher temperatures vice versa

Question 12

A more permeable membrane increases or decreases rate of diffusion?

Answer 12

increases - easier for particles to get through

Question 13

Give an example in organisms where these factors are optimised for diffusion

Answer 13

The lungs - large surface area from alveolus and good blood supply form the pulmonary vein and artery, as well as many capillaries. Also high core body temperature.

Question 14

Define osmosis

Answer 14

the net movement of water from a solution of higher to lower water potential through a partially permeable membrane.

Question 15

What are the differences between osmosis and diffusion ?(2)

Answer 15

Only applies to water

Movement is only through a partially permeable membrane

Question 16

define water potential

Answer 16

the pressure exerted by water molecules

Question 17

how do solutes lower water potential?

Answer 17

water is attracted by solutes, therefore is less able to move and doesn’t exert as much pressure.

Question 18

How is water potential measured?

Answer 18

water potential is a arbitrary scale shown by Ψ. Within pure water it always equals 0, but if you lower the water pressure the water potential turns negative.

Question 19

Describe what happens to a hypotonic animal cell

Answer 19

A hypotonic ( low solute potential, high water potential) animal will swell and possibly burst this is known as lysed.

Question 20

Describe what happens to a hypotonic plant cell

Answer 20

A hypotonic ( low solute potential, high water potential) plant cell will swell up but not burst this is know as becoming turgid.

Question 21

Describe what a isotonic plant cell is like

Answer 21

An isotonic (equal solute and water potential) plant cell is flaccid. hehe.

Question 22

Describe a hypertonic animal cell

Answer 22

A hypertonic (higher solute potential, lower water potential) animal cell will become shrivelled.

Question 23

Describe a hypertonic plant cell.

Answer 23

A hypertonic plant cell will become plasmolyzed

Question 24

Describe simple diffusion, give examples

Answer 24

Passive movement of small, hydrophobic particles through the bilayer. O2, steroids

Question 25

describe facilitated diffusion. two types

Answer 25

1. passive movement of large molecules which bind to specific carrier(proteins), which then a conformational change occurs and the substance is released on the other side. 2 passive movement of charged or polar substances through a channel or pore protein e.g. ion.

Question 26

what are aquaporins?

Answer 26

channel proteins specifically for water

Question 27

facilitated diffusion proteins may also be selective or gated - what do these terms mean in relation to channel proteins

Answer 27

selective - only allow particular proteins

Gated - can be opened or closed

Question 28

lowkey wanna

Answer 28

die, smiley face.

Question 29

Describe osmosis

Answer 29

Passive Movement of water molecules down the water potential gradient, often through aquaporins.

Question 30

describe active transport

Answer 30

Specific substances bind to carrier, a conformational change occurs and the substance is released the other side. This is a active process (requires ATP) which goes against the concentration gradient and requires the aid of carrier proteins with complementary fit with associated molecules.

Question 31

What is cytosis

Answer 31

cytosis is a active process (requires ATP) which is the bulk transport of large materials across the cell surface membrane with the use of VESICLES.

Question 32

what is the difference between endocytosis and exocytosis

Answer 32

exo - exporting, secretion
endo - importing
both done with aid of vesicles

Question 33

What is phagocytosis?

Answer 33

The bulk uptake of solids by vesicle formation, e.g. ingestion of bacteria

Question 34

What is pinocytosis?

Answer 34

bulk uptake if fluids by vesicle formation e.g. lipid absorption by epithelial cells of small intestine

Question 35

why is the current model of membranes known as the ‘fluid mosaic model’

Answer 35

Fluid - its fluid, the phospholipids can move around.

mosaic - reminiscent of a mosaic with the proteins embedded in it.

Question 36

How does increased temperature impact membrane structure

Answer 36

Increased kinetic energy of phospholipids, increases average phospholipid separation, increases permeability of bilayer, bilayer may even melt, proteins by even denature affecting permeability.

Question 37

How does cholesterol effect membrane permeability?

Answer 37

membrane permeability increases with more cholesterol, as it breaks up the membrane. More cholesterol may be an adaption of organisms in low temperature environments.