topic 2

Question 1

properties of GE surfaces

Answer 1

high SA:V ratio
short diffusion pathway
steep conc gradient
- good bloody supply

Question 2

ficks law

Answer 2

rate of diffusion proportional to
( SA x conc diff)/ thickness of membrane

Question 3

role of lungs

Answer 3

maximise gas exchange
minimise water loss across exchange surface
located in thorax

Question 4

trachea

Answer 4

allows air to travel to lungs
c shaped rings of cartilage to keep it open
layer of mucus lining- traps dust and pathogens

Question 5

cilia

Answer 5

tiny hairs
found lining airways
waft mucus to top of trachea

Question 6

bronchi

Answer 6

similar structure to trachea
thinner walls and smaller diameter
full circle cartilage rings (not C shaped)

Question 7

bronchioles

Answer 7

decrease in size closer to alveoli
larger have elastic fibres ands smooth muscle to adjust size of airway
smaller have no smooth muscle but do have EF

Question 8

alveoli

Answer 8

at end of bronchioles
wall= single layer of flattened/ squamous epithelium
thin and permeable for easy diffusion
surrounded by elastic fibres
lined by layer of moisture so gases can dissolve

Question 9

features of membranes

Answer 9

partially permeable
can be crossed by diffusion or AT
contain receptor proteins

Question 10

phospholipids

Answer 10

glycerol, phosphate group(hydrophilic), two fatty acid tails (hydrophobic)
polar head, two non polar tails

Question 11

proteins

Answer 11

involved in cell transport and communication
intrinsic (integral)
or extrinsic (peripheral)

Question 12

cholesterol

Answer 12

found between phospholipids
regulates membrane fluidity (esp at low temps)
stops phospholipid tails packing too closely together
stabilises membrane at higher temperatures
increases mechanical strength and stability of membranes

Question 13

glycolipids /proteins

Answer 13

protein/lipid with carbohydrate attached
aid cell-to-cell communication
bind with substances at cell surface
act as cell markers or antigens for recognition

Question 14

fluid mosaic

Answer 14

scattered pattern of components within bilayeer
components can move around within the bilayer by diffusion- fluid

Question 15

partially permeable

Answer 15

small, non-polar molecules can pass through gaps between the phospholipids
large, polar molecules must use channel proteins/ carrier proteins

Question 16

diffusion

Answer 16

net movement of a substance from an area of higher concentration to an area of lower concentration - down a conc grad
passive process
continues until equilibrium is reached

Question 17

factors affecting diffusion

Answer 17

conc grad
temp
sa
properties of substance

Question 18

facilitated diffusion

Answer 18

large, polar molecules/ ions cannot diffuse directly
channel/ carrier proteins enable FD
highly specific- only allow one type of molecule/ ion to pass through

Question 19

channel proteins

Answer 19

pores- extend from one side of membrane to other
allow charged substances through
most are ‘gated’
controls exchange of ions
fixed shape

Question 20

carrier proteins

Answer 20

switch between two shapes
binding site opens then opens to other side
movement of substances down conc grad

Question 21

AT

Answer 21

movement of molecules/ ions through cell membrane against conc grad
requires energy - ATP
requires carrier proteins
energy allows the CaP to change shape
ATP hydrolysed to release energy

Question 22

types of active transport

Answer 22

reabsorption
absorption
loading sugar into phloem
loading inorganic ions into root hair cells

Question 23

endocytosis

Answer 23

for molecules too large for travel via membrane proteins
cell surrounds substance with section of cell membrane- engulfs substance and forms temp vacuole
ACTIVE process

Question 24

exocytosis

Answer 24

secretion
vesicles containing substance pinch off from sacs of golgi apparatus
vesicles fuse with cell surface membrane
ACTIVE PROCESS

Question 25

osmosis

Answer 25

net movement of water molecules from a region of lower solute concentration to a region of higher solute concentration through a partially permeable membrane
water moving down concentration gradient

Question 26

‘free’ water molecules

Answer 26

when not surrounding substances in a solution
in osmosis water mols move from more free water mols to less free water mols

Question 27

importance of osmosis

Answer 27

affects cells of living organisms
lose or take on water depending on no of free water mols in surroundings compared to cytoplasm