2.3.1: Membrane structure

Question 1

What is the general structure of a cell surface membrane

Answer 1

phospholipid bilayer - hydrophilic phosphate head, hydrophobic fatty acid tails - intrinsic protein, extrinsic protein, cholesterol, glycoprotein

Question 2

how do phospholipids arrange themselves when they are surrounded by water

Answer 2

micelle

Question 3

how do phospholipids arrange themselves when there is water on two sides

Answer 3

bilayer

Question 4

state the polarity of the phosphate head and fatty acid tails

Answer 4

phosphate head = polar molecule
fatty acid tails = non polar

Question 5

what is a glycolipid

Answer 5

a phospholipid with a carbohydrate chain attached

Question 6

what is an intrinsic protein

Answer 6

they span the entire phospholipid bilayer, most function as carrier or channel proteins

Question 7

What does a channel protein do

Answer 7

facilitated diffusion of ions, have the ability to open and close - selectively permeable membrane

Question 8

what does a carrier protein do

Answer 8

facilitated diffusion of polar molecules, active transport of both polar molecules and ions, ability to change shape for the transportation of a molecule

Question 9

what lining do all transport proteins have (channel and carrier)

Answer 9

hydrophilic lining

Question 10

what are the three cotransport proteins

Answer 10

uniport, symport, antiport

Question 11

what does a uniport do

Answer 11

transports proteins that passively transport one specific ion or one specific polar molecule down the concentration gradient

Question 12

what does a symport do

Answer 12

actively transports two different substances at the same time in the same direction

Question 13

what does an antiport do

Answer 13

actively transports two different substances at the same time in opposite directions

Question 14

what are extrinsic proteins

Answer 14

proteins in (extracellular surface) or on (cytosolic surface) one surface of the cell membrane

Question 15

what is the function of an extrinsic protein on extracellular surface

Answer 15

receptors for hormones or role in cell recognition

Question 16

what is the function of an extrinsic protein on cytosolic surface

Answer 16

involved in cell signaling or chemical reactions

Question 17

what are the factors that increase membrane fluidity

Answer 17

temperature increase -> increase in kinetic energy -> increased fluidity in membrane
cholesterol
organic solvents like ethanol dissolves the lipids causing a puncture in the membrane

Question 18

what is cholesterol and how does it affect membrane fluidity

Answer 18

it is a type of lipid, an increase = reduce of fluidity of membrane -> reducing permeability of the membrane

Question 19

why do we need cholesterol in the membrane of our cells

Answer 19

to reduce membrane fluidity to stop our cells from being too fluid as the cells would burst open

Question 20

what is the role of phospholipids

Answer 20

act as a barrier to most molecules

Question 21

what is the role of intrinsic proteins

Answer 21

transport molecules across the membrane or catalyse reactions

Question 22

what is the role of glycoproteins and glycolipids

Answer 22

involved in cell recognition, cell signalling and cell attachment

Question 23

Describe what is meant by the fluid mosaic model in relation to the structure of the cell membrane

Answer 23

·proteins are scattered throughout the phospholipids - looking like a mosaic, proteins dotted throughout the membrane
·each of the components of the membrane can all move in relation to each other - fluid

Question 24

what model is the structure of the cell membrane widely referenced to as

Answer 24

the fluid mosaic model