1.3

Question 1

Who proposed the fluid mosaic model

Answer 1

Singer and Nicolson in 1972

Question 2

What does the fluid mosaic suggest (2 marks)

Answer 2

biological membranes consist of phospholipid bilayers with proteins embedded in the bilayer, making the membrane look like a mosaic

Question 3

what is a triglyceride made up of

Answer 3

on glycerol and three fatty acids

Question 4

what is a phospholipid

Answer 4

a lipid where one of the fatty acids has been replaced by a phosphate group

Question 5

what is the phosphate head described to be

Answer 5

hydrophilic - water loving

Question 6

what are fatty acids described to be

Answer 6

hydrophobic because they are non-polar

Question 7

what is the structure of a phospholipid

Answer 7

two fatty acids, one glycerol and a phosphate head attached

Question 8

what do you call a molecule that is both hydrophilic and hydrophobic

Answer 8

amphipathic molecule

Question 9

Name 5 different types of proteins that occur in the membrane

Answer 9

Channel

carriers

receptors

recognition

enzymes

Question 10

What is a channel protein

Answer 10

a protein that has a pore channel that allows passive transport of substances between the inside and outside of the cell

Question 11

what is a carrier protein

Answer 11

proteins that bind to substances on one side of the membrane and then change shape to transport them to the other side

carrier proteins that use energy to change shape are termed protein pumps

Question 12

what is a recognition protein

Answer 12

a protein that helps the cell in differentiating between self and non self - important for immune response

Question 13

what is a receptor protein

Answer 13

proteins that span the whole membrane to relay information from the inside or outside of the cell

Question 14

what is an enzyme

Answer 14

proteins that enhance the rate of reactions that happen at the membrane level

Question 15

what two other things are part of the cell membrane

Answer 15

cholesterol and glycolipids

Question 16

what are glycolipids

Answer 16

a phospholipid and a carbohydrate attached together

they maintain structure of the cell membrane and

cells differentiating between self and non-self cells

Question 17

what is cholesterol

Answer 17

a steroid and is only found in animal cell membranes - vital for maintaining the structure of the cell membrane

Question 18

where are glycolipids and glycoproteins located on the cell membrane

Answer 18

on top of the phosphate heads

Question 19

where is cholesterol located in cell membranes

Answer 19

inside the cell membrane

Question 20

where are integral proteins located

Answer 20

throughout the entire membrane width

Question 21

where are peripheral proteins located

Answer 21

at the top or bottom

Question 22

what is cholesterol made up of

Answer 22

a non polar part comprising of four ring structures, a hydrocarbon tail and a polar hydroxyl group

Question 23

what type of molecule in terms of water is cholesterol

Answer 23

amphiphatic - allowing it to insert itself into cell membranes by interacting with phospholipids

Question 24

how does cholesterol control membrane fluidity and permeability

Answer 24

cholesterol restricts movement, reducing membrane fluidity,

at low temperatures, it also disrupts the regular packing of hydrocarbon tails, preventing solidification, enabling the membrane to be more fluid

also reduces permeability to hydrophilic molecules and ions such as sodium and hydrogen

Question 25

what molecules in cell membranes are amphiphatic

Answer 25

cholesterol, integral proteins and phospholipids

Question 26

What is the Davson-Danielli model

Answer 26

suggested that the ratio of lipid surface area to total cell was 2:1

and that the cell comprised of a lipid bilayer where two layers of polar lipid molecules arranged with their hydrophilic heads outward. the lipid bilayer was then sandwiches between two protein layers on either side of the membrane.

Question 27

what did Davson and Danielli to put forward their model

Answer 27

electron microscopy showed membranes as having three layers

two dark parallel lines with a lighter colored region in between

Question 28

what were the shortcomings of Davson-Danielli model

Answer 28

It assumed that all membranes had identical structures which did not explain how didfferent types of membranes could carry out different functions

proteins are amphiphatic though largely non-polar (hydrophobic) which would make it improve that they would be found in contact with the aqueous environment

Question 29

Where did Singer and Nicholson obtain their evidence

Answer 29

freeze fracture techniques confirmed that proteins are embedded in the membrane

showed an irregular rough surface inside the phospholipid bilayer

Question 30

What did MRIs show in the cell membrane

Answer 30

that proteins in the cell membranes could more around

Question 31

What protein demonstrated the bumps found on the fractures surface of the membrane

Answer 31

integral proteins

Question 32

Membrane proteins of hamster cells were marked with a blue dye and membrane proteins of human cells were marked with a green dye. What would be seen after the fusion of the cells?

Answer 32

blue and green markers dyes fully mixed because in the membrane, it acts liek a fluid

Question 33

which protein does cholesterol make sure is anchored to the membrane

Answer 33

peripheral

Question 34

what integral proteins span the membrane and allow for facilitated transport of materials

Answer 34

channel proteins

Question 35

what allowed scientist to falsify the damson and Danielle model

Answer 35

freeze etched electron micrographs and fluorescent markers

Question 36

Explain how the structure and properties of phospholipids help to maintain the structure of cell membranes. 9 marks

Answer 36

Hyrdophobic tails and hydrophyllic heads. One head and two fatty acids, head is made up of a glycerol and phosphate. These form a bilayer where the heads face outside and the tails face inside. The phospholipid is held together by hydrophobic interactions

Phospholipids allow for membrane fluidity, this is important to ensure the membrane remains stable. Phospholipids with short fatty acids and unsaturated have more fluidity which is important in breaking and remaking membranes