2.1.5 bio Membranes

Question 1

Describe the key features of the fluid moasic model

Answer 1

Made up of phospholipid bilayer, individual bilayer able to move freely relative to one another. Proteins and other molecules embedded in the phospholipid bilayer, which vary in shape,size,pattern throughout the membrane

Question 2

Describe the function of glycoproteins as a component of the cell membrane

Answer 2

To act as receptor molecules, which bind to particular substances at the cell surface. Important in cell to cell recogniton

Question 3

State the organelle that synthesises the lipids that form plasma membrane of the cell

Answer 3

SER

Question 4

How are cholestrol molecules critical in maintaing the right fluidity of the plasma membrane

Answer 4

They sit between the phospholipid molecules of the plasma membrane. Prevents phospholipids from grouping together too closely together, not too stiff. Prevents plasma membrane from becoming too fluid by interacting with the fatty acid tails of the phospholipid

Question 5

Describe how the proportion of saturated and unsaturated fatty acids in membrane can affect fluidity

Answer 5

Higher proportion of unsaturated fatty acids will mean higher fluidity. Faty acid tails have a kink, preventing lipids from packing closely togther, which would reduce fluidity

Question 6

How can you investigate permeability

Answer 6

Using beetroots and solvents

1) make serial dilutions of solvent via stock soloution
2) add beetroot cell membrane to different dilution
3) measure pigment released into soloution from cells using colorimeter calibrated w water

Question 7

The higher concentrations of solvent led to greater light absoprtion through the test tube solution. Explain why this occured

Answer 7

Higher solvenr concentration, more membranes were disrupted and no longer acted as barrier to pigments diffusing out of cells into solution. Solution w more pigment absorbed more light in the colormeter

Question 8

State the independent and dependent variable when investigating membrane permeability

Answer 8

Independent- solvent conc

Dependent - light absorption/transmission in colormeter

Question 9

Explain why ions cannot cross the phospholipid bilayer by diffusion and must cross using a protein channel

Answer 9

They are charged and will be replled by the hydrophobic fatty acid tails
Use protein channels so they do not interacct with any hydrophobic molecules and cam remain in a hydrophillic/ aqeuous enviornment

Question 10

Explain the two factors that can affect the rate of diffusion

Answer 10

Larger conc gradient

Increasing SA

Question 11

What is facilitated diffusion

Answer 11

Large,polar or charged molecules pass the membrane using protein carriers or channels

Question 12

Explain how FD is used in the uptake of glucose in muscle cells

Answer 12

Large,water soluble molecule, doesnt pass through lipid cell membrane. Only possible through special channels with the aid of a specfic carrier molecule

Question 13

Explain how protein channels are specilised for ion transport across membranes

Answer 13

Ions are charged and cant cross the lipid soluble enviornment
Water soluble and can pass through protein channels, which have an aqueous pore connecting each side of the membrane
AA lining the pore can also be charged to attract ion in the channel

Question 14

What happenes to WP when solutes are dissolved

Answer 14

WP decreases when solutes are dissolved in the solvent

Question 15

Explain why worms lose mass when places in a solution of salt water

Answer 15

Movement of water to the env. Via osmosis

Solute concnetration inside the worm cells is lower than enviornment, net movement

Question 16

Explain why plant cells dont burst when placed in a hypotonic solutions

Answer 16

Water molecules enter the plant cell, swell, plant cells have strong cell wall,prevent cell from bursting

Question 17

Describe two differences between diffusion and AT

Answer 17

Metabolic energy in the form of ATP is required to fuel AT, passive diffusion does not require energy to take place

Question 18

Explain why different carrier proteins are required for AT of various moledules

Answer 18

Different ion or molecules have different binding properties, different carrier proteins are needed as each protein has specfic AA and tertiary structure to bind and carry particular molecules

Question 19

State the process of active transport

Answer 19

1) particle binds carrier protein with a specfic tertiary structure
2) ATP binds to protein and hydrolysed to ADP + pi, releasing energy
3) Protein changes shape and carries particle to otheside of the membrane
4) process can be repeated as new ATP molecules replaces ADP+pi and protein regains original shape

Question 20

Name and describe 2 processes by which large moledules are transported across the cell membrane

Answer 20

Endocytosis ans exocytosis. Materials are taken up membrane bound vesicles and taken into the cell by endocytosis or are released from the cell by exocytosis

Question 21

State examples of exocytosis ans endocytosis that take place in the human body

Answer 21

Phagocytosis - example of endocytosis carried out by WBC

Synaptic transmission, exocytosis

Question 22

Which bulk transport process would be most assoicated with an endocrine gland

Answer 22

Exocytosis

Question 23

What is the outline of endocytosis

Answer 23

The membrane encloses particles to form a vesicle

Question 24

Outline the basics of exocytosis

Answer 24

Internal vesicle fuse with the membrane to release particles to the extraceullar particl