cell membranes

Question 1

why is compartmentalisation important

Answer 1

metabolism includes many incompatible reactions

Question 2

define compartmentalisation

Answer 2

formation of separate membrane-bound areas in a cell

Question 3

role of plasma membrane

Answer 3

separates the contents of the cell from its outside environment
partially permeable - only some substances can cross the membrane
attachment for cytoskeleton in some organisms - can help support the cell and maintaining its shape
site of some chemical reactions
site of cell signalling

Question 4

define cell signalling

Answer 4

communication between cells and cell recognition
molecule released by one cell, attaches to another, causes a response

Question 5

structure of plasma membrane

Answer 5

7-10 nm thickness

Question 6

what are the components of a membrane

Answer 6

phospholipid bilayer
glycoprotein
glycolipid
cholesterol
proteins molecules [intrinsic and extrinsic]

Question 7

structure of phospholipid bilayer

Answer 7

hydrophilic phosphate heads of the phospholipid form the inner and outer surface of the membrane, positively charged, head polar, attracted to water molecules in their environment
hydrophobic fatty acid tails face inwards away from the outer surface, uncharged, non-polar, repelled by water, consists of saturated fatty acids and unsaturated fatty acids
amiphipathic

Question 8

define amphipathic

Answer 8

contains both hydrophilic heads and hydrophobic tails

Question 9

label a phospholipid

Answer 9

Question 10

how are micelles formed

Answer 10

formed when phospholipids submerged in water

Question 11

what are cholesterol

Answer 11

a type of liquid
present in all eukaryotic cell membranes
amphipathic
flattened shape, fit between phospholipid

Question 12

function of cholesterol

Answer 12

bind to the hydrophobic tails on the phospholipids, causing them to pack more closely together
makes membrane more rigid and less fluid, provides stability
at low temp, keeps membranes fluid

Question 13

function of intrinsic proteins

Answer 13

span the width of membrane - transmembrane
transport water soluble charged particles

Question 14

example of intrinsic proteins

Answer 14

channel proteins
carrier proteins
glycoproteins [if a carbohydrate chain is attached]

Question 15

function of extrinsic proteins

Answer 15

interact with phospholipid heads

Question 16

where are extrinsic proteins

Answer 16

partly embedded or lying on the surface
present in either side of the bilayer
have hydrophilic R-groups on their surface to interact with phospholipid heads

Question 17

what are channel proteins

Answer 17

a hydrophilic passageway for water and charged substances to passively diffuse down a concentration gradient

Question 18

what are carrier proteins

Answer 18

change shape to move substances from one side of the membrane to the other
can be down a concentration gradient or against

Question 19

what are glycoproteins

Answer 19

intrinsic proteins with a branching carbohydrate portion of a protein

Question 20

function of glycoproteins

Answer 20

involved in cell adhesion
act as receptors for chemical signals
drugs bind to cell receptors, trigger response, direct/cascade

Question 21

what are glycolipids

Answer 21

lipids attached carbohydrate chains

Question 22

function of glycolipids

Answer 22

antigens, recognised by cells of immune system as self or non-self
stabilise membrane by forming hydrogen bonds with surrounding water molecules

Question 23

what is glycocalyx

Answer 23

a glycoprotein and glycolipid covering that surrounds the cell surface membrane
allows cell recognition