topic 2 Flashcards
properties of GE surfaces
high SA:V ratio
short diffusion pathway
steep conc gradient
- good bloody supply
ficks law
rate of diffusion proportional to
( SA x conc diff)/ thickness of membrane
role of lungs
maximise gas exchange
minimise water loss across exchange surface
located in thorax
trachea
allows air to travel to lungs
c shaped rings of cartilage to keep it open
layer of mucus lining- traps dust and pathogens
cilia
tiny hairs
found lining airways
waft mucus to top of trachea
bronchi
similar structure to trachea
thinner walls and smaller diameter
full circle cartilage rings (not C shaped)
bronchioles
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
alveoli
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
features of membranes
partially permeable
can be crossed by diffusion or AT
contain receptor proteins
phospholipids
glycerol, phosphate group(hydrophilic), two fatty acid tails (hydrophobic)
polar head, two non polar tails
proteins
involved in cell transport and communication
intrinsic (integral)
or extrinsic (peripheral)
cholesterol
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
glycolipids /proteins
protein/lipid with carbohydrate attached
aid cell-to-cell communication
bind with substances at cell surface
act as cell markers or antigens for recognition
fluid mosaic
scattered pattern of components within bilayeer
components can move around within the bilayer by diffusion- fluid
partially permeable
small, non-polar molecules can pass through gaps between the phospholipids
large, polar molecules must use channel proteins/ carrier proteins
diffusion
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
factors affecting diffusion
conc grad
temp
sa
properties of substance
facilitated diffusion
large, polar molecules/ ions cannot diffuse directly
channel/ carrier proteins enable FD
highly specific- only allow one type of molecule/ ion to pass through
channel proteins
pores- extend from one side of membrane to other
allow charged substances through
most are ‘gated’
controls exchange of ions
fixed shape
carrier proteins
switch between two shapes
binding site opens then opens to other side
movement of substances down conc grad
Active transport
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
types of active transport
reabsorption
absorption
loading sugar into phloem
loading inorganic ions into root hair cells
endocytosis
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
exocytosis
secretion
vesicles containing substance pinch off from sacs of golgi apparatus
vesicles fuse with cell surface membrane
ACTIVE PROCESS
osmosis
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
‘free’ water molecules
when not surrounding substances in a solution
in osmosis water mols move from more free water mols to less free water mols
importance of osmosis
affects cells of living organisms
lose or take on water depending on no of free water mols in surroundings compared to cytoplasm
