module 2 - 2.1.5- biological membranes

Question 1

what do membranes separate?

Answer 1

the contents of the cell from their environment

Question 2

what’s compartmentalisation?

Answer 2

the formation of separate membrane-bound areas

Question 3

what forms membranes?

Answer 3

they are formed from phospholipid bilayers

Question 4

how’s a hydrophobic core formed in a membrane?

Answer 4

• the hydrophilic phosphate heads of the phospholipids from both the inner and outer layer of the membrane sandwich the fatty acid tails of the phospholipids

Question 5

why are phospholipid bilayers suited to being membranes?

Answer 5

as the outer surface of the hydrophilic phosphate heads can interact with water

Question 6

what allowed the membrane to be seen for the first time?

Answer 6

1. electron microscope
   =allows images with high mag and res

Question 7

what was the theory on membranes in the 50’s?

Answer 7

= they were made of lipid layers
=this was thought because membranes on microscopes were seen as two black lines

Question 8

who produced the fluid mosaic model and what is it ?

Answer 8

=Singer and Nicoloson
=they built on the lipid bilayer model and proposed that protiens occupy various positions in the membrane

Question 9

why is the fluid mosaic model called that?

Answer 9

= the phospholipids are allowed to move in the layer relative to each other
=this gives the membrane flexibility

Question 10

why are components of the membrane important?

Answer 10

they all play an important role in the functions of the membrane

Question 11

what are the two types of membrane proteins?

Answer 11

intrinsic and extrinsic

Question 12

what type of proteins are intrinsic proteins?

Answer 12

transmembrane proteins

Question 13

how do intrinsic proteins stay in place in the membrane?

Answer 13

1. they have amino acids with hydrophobic R groups on their external surfaces
   2.these interact with the hydrophobic core of the membrane
2. this keeps them in place

Question 14

Example of two types of intrinsic proteins?

Answer 14

1. channel proteins
2. carrier proteins

Question 15

what are channel proteins?

Answer 15

they provide a hydrophilic channel that allows passive movement of polar molecules down a concentration gradient through a membrane

Question 16

what are carrier proteins?

Question 17

whats passive transport?

Answer 17

down a concentration gradient

Question 18

What type of protein is a glycoprotein?

Answer 18

intrinsic

Question 19

Where are glycoproteins located?

Answer 19

they are embedded into the cell surface membrane with attached carb chains of different lengths

Question 20

what are the main roles of glycoproteins?

Answer 20

1. play a role if cell adhesion
   2.receptors for chemical signals

Question 21

Examples of cell signalling?

Answer 21

1. receptors for neurotransmitters
   2.recpeptors for peptide hormones

Question 22

what are glycolipids?

Answer 22

1. similar to glycoproteins
   2.they are lipids with attached carb chains
   3.they are called cell markers/antigens

Question 23

what type of protein is an extrinsic protein?

Answer 23

peripheral protein

Question 24

where are extrinsic proteins located?

Question 25

whats the structure of an extrinsic protein?

Answer 25

hydrophilic R groups on their outer layer interact with phospholipid heads

Question 26

whats the structure of cholesterol?

Answer 26

• it is a lipid
  -it has a hydrophilic end and a hydrophobic end

Question 27

whats the role of cholesterol?

Answer 27

regulated fluidity of membranes

Question 28

how does cholesterol molecules add stability to membranes?

Answer 28

• they are positioned between phospholipids in the bilayer
  -the hydrophilic ends interacting with the heads and hydrophobic ends interacting with the tails pulling them together
  -this adds stability to the membrane

Question 29

What happens to membranes when temperatures are increased?

Answer 29

1.phospholipids in the membrane will gain KE and start to move more
2.this makes the membrane more fluid and lose structure
3.this increases the permeability of the membrane allowing more particles to pass through
4.carrier and channel proteins will denature in the membrane they are involved with movement across the membrane so as they denature the membrane permeability will be impacted

Question 30

definition of diffusion?

Answer 30

The net movement of particles from an area of a high concentration to an area of a low concentration

Question 31

what factors affect simple diffusion?

Answer 31

1.temperature
2.concentration difference

Question 32

how does temperature affect the rate of diffusion?

Answer 32

the higher the temperature the higher the rate of diffusion
=as the particles have more kinetic energy

Question 33

how does concentration difference affect the rate of diffusion?

Question 34

what do particles have to pass through in diffusion?

Answer 34

phospholipid bilayer

Question 35

what factors affect the rate of which molecules and ions diffuse across a membrane?

Answer 35

1.surface area= the larger the surface area the higher the rate of diffusion
2.thickness of membrane= the thinner the membrane the higher the rate of diffusion

Question 36

what’s facilitated diffusion?

Answer 36

diffusion across a membrane through protein channels and carrier proteins

Question 37

in facilitated diffusion is the movement of particles up or down a concentration gradient?

Answer 37

down

Question 38

how does the number of protein channels impact the rate of facilitated diffusion?

Answer 38

the more protein channels the higher rate of diffusion

Question 39

what are carrier proteins?

Answer 39

they move large molecules down the concentration gradient
1.large molecule attaches
2.protein changes shape
3.released on the other side of the membrane

Question 40

the definition of active transport?

Answer 40

the movement of molecules/ions in or out of a cell from a low concentration to a higher concentration

Question 41

what does active transport require to happen?

Answer 41

ATP
carrier proteins

Question 42

Whats the process of active transport?

Answer 42

1,the molecule binds to the receptor in the channel of the carrier protein outside the cell
2,inside the cell ATP binds to the carrier protein and is hydrolysed into ADP and a phosphate
3, phosphate and carrier protein binds this changes the shape of the protein opening up the cell
4,the molecule is released
5,phosphate molecule is released and binds to ADP again forming ATP

Question 43

why is bulk transport needed?

Answer 43

enzymes, hormones and bacteria are too large to move through channels and protein carriers so they are moved by bulk transport

Question 44

where does endocytosis move material?

Answer 44

into the cell

Question 45

whats the process of endocytosis?

Answer 45

1. cell surface membrane bends inwards when it comes into contact with the material
   2.the membrane keeps bending till the membrane fuses and forms a vesicle
2. the vesicle pinches off and moves into the cytoplasm

Question 46

where does exocytosis take material?

Answer 46

outside the cell

Question 47

whats the process of exocytosis?

Answer 47

1. vesicle forms at golgi apparatus
   2,vescile moves to the cell surface membrane and fuses with it
   3, the contents of the vesicle is then released outside the cell

Question 48

what processes need ATP in the transport of materials?

Answer 48

active transport
endocytosis
exocytosis

Question 49

Why is ATP needed in exo/endocytosis?

Answer 49

for the movement of the vesicle along the cytoskeleton

Question 50

definition of osmosis?

Answer 50

the movement of water molecules across a partially permeable membrane from a high to lower concentration