Cell Surface Membrane

Question 1

Name the 10 components of a cell surface membrane

Answer 1

• phospholipid
• glycoproteins
• Glycolipids
• channel proteins
• carrier proteins
• cholesterol
• receptor sites
• enzymes and coenzymes
• intrinsic proteins
• extrinsic proteins

Question 2

Function and examples of an intrinsic protein

Answer 2

span the entire membrane 
4 functions
1) act as channels 
2) transporters
3)receptors
4) enzymes 

Examples
Carrier protein
Channel protein
Glycoproteins

Question 3

Function and example of extrinsic protein

Answer 3

Peripheral protein which are present in one side of the phospholipid bilayer

Example
Peripheral proteins

Question 4

Phospholipid

Answer 4

Hydrophobic head (which is polar) and hydrophilic tail (which is non polar)
Many phospholipids form a bilayer. The tails are touching and the heads are facing outwards

Question 5

Channel proteins

Answer 5

• intrinsic protein
• provide a hydrophilic channel that allows passive movement e.g. diffusion
• movement of polar molecules and ions down the concentration gradient

Question 6

Glycoproteins

Answer 6

• carbohydrate branching off a protein
• acts as a recognition site for chemicals (receives signals)
• stabilises membrane
• play a role in cell adhesion

Question 7

Glycolipids

Answer 7

• Lipids attaches to carbohydrate/sugar chains
• called cell markers ANTIGENS (act as an ID card)
• can be recognised by the immune system as self or foreign

Question 8

Carrier proteins

Answer 8

• important in passive transport and active transport
• intrinsic protein
• changes shape to allow molecules in

Question 9

Cholesterol

Answer 9

• provide structure for the membrane
• sit between the phospholipids
• steroid molecule
• can reduce permeability and fluidity if there are lots

Question 10

Enzymes and coenzymes

Answer 10

• for reaction that take place in the membrane

Question 11

Intrinsic protein

Answer 11

• span the entire membrane
• sit in the later writhing the phospholipids
• have 4 main functions
  1) act as channels
  2) transporters
  3) receptors
  4) enzymes

Question 12

Extrinsic proteins

Answer 12

• also known as peripheral proteins
• present on one side of the bilayer
• normally have hydrophilic r - groups on their outer surface
• some move between layers
• cell signalling
• cell recognition
• receptor for other molecules e.g. hormones

Question 13

What is the cell surface membrane structure described as

Answer 13

Fluid mosaic structure

Question 14

Functions of the cell surface membrane

Answer 14

• barrier between cell, outside environment and organelles
• allow recognition by other cells (antigens, cells of the immune system)
• sites of cell communication

Question 15

Cell signalling

Answer 15

When cells communicate with messenger molecules

• one cell releases a messenger molecule
• this molecule travels (e.g. in the bloodstream) to another cell
• this messenger molecule binds to a receptor on the cells surface membrane of the target cell

Question 16

Functions of membranes within the cell

Answer 16

• keeping all cellular components inside the cell (at as a barrier)
• can form vesicles to move in and out of the cell
• isolating organelles from the rest of the cytoplasm , allowing cellular processes to happen separately
• a site for biochemical reactions
• allowing a cell to change shape

Question 17

What is an eyepiece graticule

Answer 17

• used when you want to measure the size of a specimen
• fitted onto the eyepiece
• has numbers but no units
• remains constant so must be calibrated for each objective lens

Question 18

How to calibrate an eyepiece graticule

Answer 18

1) place the eyepiece graticule in the eyepiece, and place the stage micrometer on the stage
2) Align the 0 point of the eyepiece graticule with the 0 point of the stage micrometer
3) scan along until you find when the scale line up again
4) count how many eyepiece units are equal to the number of stage micrometer units

Question 19

Stage micrometer

Answer 19

• glass slide that is placed on the stage
• it is etched with an accurate scale (usually 1mm with 100 divisions)
• it is used to work lout the value of each eyepiece graticule division at a particular magnification