exchange Flashcards
SA:V ratio
for exchange to be efficient the surface area of an organism must be large compared to its volume
as the object gets larger the smaller its SA:V ratio e.g an elephant has an extremely lower SA:V ratio compared to an amoeba
SA:V ratio should be shown as x:1
Fick’s law
diffusion rate= (Sa× conc gradient)/diffusion distance
from this we can see rate of diffusion is lower in larger organisms, so they have evolved specialised exchange systems e.g. lungs that have larger SA: V
enables efficient diffusionb
SA and Metabolic rate
smaller organisms have larger SA:V
so they lose more heat as a drawback
to compensate they increase metabolic activity through thongs like respiration
one of the byproducts of metabolism is heat allowing them to maintain body temp
as SA:V ratio increases so does metabolic rate
single called organisms
Oxygen is required to produce ATP during Aerobic respiration
Carbon dioxide is produced as waste during this
all organisms rely on diffusion to exchange O2 and CO2 which move down conc gradients
single celled and some small organisms have large enough SA:V ratio to meet gas exchange needs by diffusion across cell surface membrane
have short diffusion distance- Ficks law means this results in faster rate of diffusion
specialised gas exchange
large organisms can’t rely on diffusion through surface alone to meet O2 demands
diffusion would be too slow and diffusion pathway too long
so they have specialised gas exchange surfaces for faster rate of diffusion of gases
what makes a good gas exchange surface
Large SA
large conc gradient
thin exchange surface so short diffusion distance
gas exchange in insects
system called tracheal system
movement of 02 in-
oxygen enters through spiracles into tracheae
spiracles close
o2 diffuses through tracheae into tracheoles where gar exchange occurs
o2 delivered directly to tissue
tissue respire using 02 reducing conc at the tissue
O2 move from higher to lower conc so move from tracheae to tissue
lowers O2 conc in tracheae so O2 moves in through spiracles
respiration produces CO2 increasing conc in tissue
CO2 moves from higher to lower conc so from tissue to tracheae
CO2 then moves from high conc in tracheae to lower conc outside via spiracles
Tracheal system adaptations
chitin keeps the tracheae open
tracheoles-
highly branched providing a large surface area for faster diffusion
their walls are thin shorter diffusion distance
supply tissue so diffusion is direct into cells
walls are permeable to O2
abdominal pumping- flex abdomen mataining conc gradient for O and CO2
insects have small air sacs in their trachea, muscles around trachea contract and pump the air in the sacs deeper into tracheoles
Insects- features to reduce water loss
rigid outer skeleton- waterproof exoskeleton, impermeable
spirituals close
small hairs around spiricals trap water to reduce water potential gradient
Gas exchange in fish
Gills are gas exchange organ each fish has 4 gills on side of head
movement of oxygen into fish-
water carrying O2(30% less than air) moves in through mouth and out through gills
gills have finger like projections- gill filaments (attached to gill arch)
each filament has many lamellae
lamellae contains capillaries and are site of gas exchange
water carrying O2 passes through lamellae and most O2 is removed entering capillaries
finally water containing little 02 leaves through gill openings
Adaptation for efficient gas exchange- gills
lamellae- large surface area
lamellae contains capillaries- short diffusion distance
lamellae have thin epithelium- short diffusion distance between water and blood
countercurrent flow- water and blood flow in opp directions
diffusion gradient always maintained
along entire lenght of gill lamellae
water always has higher O conc than blood so O2 always moves in
gas exchange- dicotyledonous plants
flowing plants
leaves are gas exchange organs
movement of CO2 (for photosynthesis) into plants-
CO2 enters via stomata which are opened by guard cells
diffuses into air spaces of spongy mesophyll down conc gradient
Palisade mesophyll have lower conc of CO2 owing to photosynthesis so moves into air spaces down conc gradient
O2 moves in opp direction (into atmosphere via stomata)down conc gradient as it is a byproduct of photosynthesis
leaf adaptations for efficient gad exchange
They are flat- large SA:V ratio
contain many stomata- allow air to move in and out of leaf
air spaces in spongy mesophyll- short diffusion pathway
adaptation of leaf ti reduce water loss
guard cells close stomata at night- as less Co2 needed at this time as no photosynthesis
upper + lower surfaces have waxy cubical
most stomata on lower epidermis as less sunlight and evaporation
air spaces are saturated with water vapour from xylem reducing WP gradient
Xerophytes
plants that like in dry/arrid areas
extra adaptation to reduce water loss
thick waxy cutical- increased diffusion distance so less transpiration
hair + stomata in pits + rolled leaves- trap water vapour reduce WP gradient
Spines not leaves- reduce SA:V ratio reducing transpiration
small leaves+ reduced stomata so reduced transpiration
Lung anatomy
Trachae(windpipe)- O2 from mouth to lungs
branches into
2 bronchi- O2 to right and left lung
branches into
brochioles- which at tips have air sacs called alveoli
this is where gas exchange occurs
Alveoli structure and adaptations
gives extremely large SA, total 70m² in adult
have rich blood supply ensures large conc gradient between gases in alveoli and capillaries
deoxygenated blood- lungs via pulmonary artery from heart
oxygenated blood- back to heart via pulmonary vein
gases separated from the blood by alveolar epithelium(1 cell thick-short diffusion path) and cappilary endothelium
permeable to gases
ventilation
resilt of diff in pressure between lungs and air outside body
inhalation- active
External intercostal muscles contract-pull ribcage up and out
diaphragm contracts and pulls down
thorax cavity increases in volume
pressure in the lungs lower than atmospheric pressure
air moves into lungs down pressure gradient
exhalation- passive
internal intercostal muscles contract external intercostal muscle relaxes
diaphragm relaxes moves up
thorax cavity volume decreases
pressure in lungs is greater than atmospheric pressure
air moves out down pressure gradient
pulmonary ventilation
pulmonary vent rate- total volume of air that moves into lungs in 1 min
tidal volume- volume of air taken in at each breath at rest
breathing rate-number of breaths taken in a min
pulmonary vent rate= tidal volume x breathing rate
dm³min‐¹ dm³ min-¹
what is a risk factor
risk factors are enviroment and genetic factors that can increase/decrease the risk of developing a disease
exposure or presence doesn’t grunted development if disease just increase risk
some do have possible causal relationships tho
risk factor will lead to disease
correlation doesn’t mean causation
risk factors for lung disease
smoking- 90% of suffers where heavy smokers
airpollution- pollutant particulates and gases
genetic makeup-geneticaly more likely
infections-increased chance if u get regular chest infections
occupation- working with harmful chemicals gases and dust
to prove cause nit just correlation we must:
establish hypothesis and try explain correlation
design and perfom experiments to test hypothesis
establish causal link and formulate theories to explain it
linear vs non linear relationship
if as you increase the factor there is a portional increase or decrease in outcome you are measuring we same there is a linear relationship
faster or slower and it is non linear/not proportional
this is one way to test if risk factor causes outcome
correlation
one way to asses contribution of risk factor to outcome
plot scatter graph to see correlation
rhe direction of scatter indicates positive, negative or non correlation
CORRELATION DOESN’T MEAN CAUSATION
Probability(P) Values
use statistical test to calc P values
this determines if there is a true effect or whether effect is due to random chance
true effect has a p value less than 0.05
there is a less than 5% chance that correlation/difference us due to chance
there is a significant difference/correlation
use difference when discussing means and correlation when comparing 2 continuous variables
statistical tests
T test-
when comparing the difference between 2 means from diff groups
p value less than 0.05 then sig dif between means
correlation coefficient-
When assessing the strength of relationship between 2 continuous variables
p value less than 0.05 then sig correlation between variables
Chi squared- when comparing the observed vs expected categorical data
is p value is less than 0.05 then sig dif between observed and expected
if above 0.05 then no sig difference same for all the others
correlation coefficient
correlation Coefficient provides and R value
indicates significance of correlation
ranges from +1 to -1
R values closer to +1 mean strong positive
0 means no correlation
-1 mean strong negative correlation
Writing out hypothesis
either null or alternative
words differ depending on statistics test used
alternative means there is a significant distance between measurement
either correlation if correlation coefficient or means if T test
Null means there isn’t a significant difference between measurement
either correlation if correlation coefficient or means if T test
Accepting/rejecting hypothesis
If testing a null hypothesis and your P value is less than 0.05 then there is a significant difference and the null hypothesis must be rejected
if you are testing a null hypothesis and the P value is greater than 0.05 then there is no sig difference and so null hypothesis is accepted
Haemoglobin- basic knowledge
complex protein- 4 polypeptide chain
each has a haem group containg an iron ion which associates with 1 02 molecule
so can combine with 4 overall
haemoglobin + O2 —> Oxyhaemoglobin
reversible reaction
percentage saturation of haemoglobin
amount of O2 combined
100% 4/4,oxygen molecules bonded
75% 3/4
50% 2/4
25% 1/4
oxygen dissociation curve
shows how saturated haemoglobin is with O2 at any pp
this is affected by haemoglobins affinity to O2
always S shaped- sigmoid curve
shifted left= higher O2 affinity (low O2 environment)
Shifted right= low O2 affinity (high activity)
affinity
natural attraction to something e.g. haemoglobin to O2
Partial pressure (p)
the amount of a particular gas in a mixture of gases or a solution
pO2 in lungs
High pO2 in lungs
haemoglobin has higher O2 affinity at high pO2, causing association/loading (O2 taken up by haemoglobin)
haemoglobin becomes fully saturated as red BC pass through Pulmonary capillaries
pO2 in tissue
PO2 is low in tissue
Haemoglobin has low affinity for O2 at low PO2
so oxyhaemoglobin starts to break down + release O2 (disassociation/unloading)
due to the high conc of CO2 in respiring tissues
dissolved into blood to Make in more acidic (carbonic acid formed)
alters shape of haemoglobin lowering affinity for O2 (ensures more O2 is provided during increased metabolic rate as CO2 produced when cells respire)
O2 released is available for respiration in tissue cells
CO2 causes curve to shift to the right( bohr shift) as raised PCO2 increases rate of O2 unloading
why is O2 disassociation curve S shaped
First O2 molecules combines relatively slow with first iron ion- so first part of graph not very steep
causes tertiary structure of haemoglobin to change
exposes rest of binding sites easier for 2nd and 3rd to bind (becomes steeper)
4th hardest to bind as close to 100% saturation (requires laregest pp increase) so graph levels off
diff types of haemoglobin
diff organisms have diff types of haemoglobin
diff O2 transport properties
adaptation to help survival in particular environments
Low O2 environment-
low O2 conc
haemoglobin with higher O2 affinity
focuses on association of O2
Dissociation curve shifts to left
High activity levels-
high O2 demand
Haemoglobin with lower affinity for O2
Easier to unload O2 at respiring tissues for respiration
Dissociation curve shifted right
Mother and foetus Dissociation curve
foetus-
shifted left
higher O2 affinity
as low O2 environment
load O2 when mother unloads O2
Mothers-
shifted right
lower affinity
easier unloading to foetus
load O2 as foetus loads O2
Circulatory system
made up of heart and blood vessels
mammals- have double system (passes through the heart twice to maintain pressure)
head
lungs
A C ---> right A left A <----- <--- right V left V ----->
B D
E F
<---- liver<------
^ G
gut
H I
<---kidney<---
legs
A- Vena Cava (body to heart e.g. connects to renal and hepatic vein)
Deoxgenated
B- Pulmonary artery (heart to lungs)
deoxygenated
C- pulmonary vein (lungs to heart)
oxygenated
D- Aorta (heart to body)
oxygenated
E-hepatic vein (liver to vene Cava to heart)
f- Hepatic artery (Aorta to hepatic artery to liver)
g- hepatic portal vein (gut to liver)
H- Renal vein (kidney to vene cava)
I- Renal artery (heart to Aorta to renal artery to liver)
heart functions plus adaptations
right- deoxygenated blood from body via vene Cava
pumps blood to lungs via pulmonary artery
left- oxygenated blood from lungs via pulmonary vein
pumps oxygenated blood to body via Aorta
thicker as higher pressure
left ventrical- has thicker muscle wall as higher it has to pump blood all the way around body not just to lungs, allows higher pressure
ventricals have thick muscular walls to generate high pressure to punp blood out of heart, atria are less thick as pump blood short distance
Valves prevent backflow, they do this by only opening one way and closing/opening based on pressure of heart chamber
always high to low pressure
atrioventricualr valves- atria to ventricals
semilunar valves- ventricals to arteries
structure of heart
pulmonary artery aorta
vene -Right a left a - pulmonary vein
Cava
tricuspid valve mitral valve
right v left V
there are also 2 semilunar valves between the arteries and ventricles .
on the right-pulmonary valve
on the left-aortic valve
The cardiac cycle
sequence of contracts and relaxation the creates pressure gradients to open valves and move blood around the body.
1.Ventricles relax and atria contract-
V= relax so lower pressure
A=contract causing volume of the chambers to decrease
increasing pressure
Av opens->blood moves into V-> down pressure gradient
2.A=relax so pressure decreases
V= contract
causing volume to decrease and pressure increase
pressure higher in V than A
so AV closes to prevent backflow
Sl valve opens as pressure in V higher than artery
blood forced into arteries
- V and A are now relaxed
pressure higher in arteries than V
so SL valves close to prevent backflow
blood returns to heart as pressure in veins higher than A
so blood enters-> pressure increases and cycle restarts
pressure is greater before valve opens, when the pressure is greater after it will close
cardiac output
CO=stroke volume (SV)x Heart rate (HR)
Cm3 min-1 Cm3 Bpm
SV- volume of blood pumped each heart beat
HR- no of beats per min
arteries
artery
mean diameter- 4 mm
mean wall thickness- 1mm
has the most elastic tissue and smooth muscle
Thick outer walls to withstand pressure
muscular walls-> contract -> reduce lumen diameter-> allow changes in flow and pressure (vasocontraction)
elastic tissue- stretch when V contract + recoil when V relaxes-> recoil maintains high pressure
small lumen + endothelium-smooth and reduces friction
no valves- constant pressure so no backflow
arterioles
arteries -> arterioles
little/no elastic (low pressure) or fibrous tissue
mean diameter- 30 micrometres
mean wall thickness- 6 “
carry blood from arteries to capillaries under lower pressure
muscular layer is thicker in these allowing them to contract and constrict lumen -> restricts blood flow -> control movement into capillaries
veins
take blood back to heart from body
relaxation of heart muscle-> lowers pressure-> blood flow towards atria down pressure gradient
mean diameter- 5mm
mean wall thickness- 0.5mm
thin muscle layer (in comp to arteries) -> constriction and dilation cant control flow of blood to tissues (as body-> heart)
thin elastic layer(“)-> as low pressure no risk of burst or need for recoil
thin wall- pressure to low for risk of bursting also easy flattening aids blood flow
valves-to insure no backflow due to low pressure, ensure pressure directs blood flow in only 1 direction
when body muscle contracts, veins compressed, increase pressure of blood
wide lumen- reduces friction
capillaries
smallest
site of substance exchange from blood to cell
found near cells in exchange surface e.g. alveoli, for short diffusion path
large no of capillaries (branched/network/beds) increase SA for exchange
one cells thick- short diffusion path
capillary wall is permeable- for diffusion
contain fenestrations- allow large molecules to leave blood vessel
narrow lumen- reduce flow rate, more time for diffusion, only 1 red blood cell at a time
endothelial cells- smooth and flat, reduces friction and shortens diffusion distance
tissue fluid formation
tissue fluid in tissue space
formed from blood plasma
substances move out of capillary into tissue fluid via pressure filtration
blood-> tissue fluid -> cell
arterial end- hydrostatic pressure higher than in tissue fluid
difference means pressure forces fluids out of capillaries into tissue space
form tissue fluid
as fluid leave -> hydrostatic pressure decreases in cap so much lower at venous end
large proteins, too big to leave, remain reducing WP of cap at venous end
venous end- hydrostatic pressure lower than in tissue fluid
so tissue fluid forced back into cap due to pressure diff
also WP of cap lower than tissue fluid
so water re-enters cap by osmosis
tissue fluid that doesn’t return into cap is drained away from tissue by lymphatic system, this fluid now referred to as lymph
Cardiovascular disease
general term for diseases associated with heart and blood vessels
most start with atheroma formation
e.g.
aneurysm-a bulging, weakened area in the wall of a blood vessel resulting in an abnormal widening or ballooning, which then ruptures
thrombosis-a bulging, weakened area in the wall of a blood vessel resulting in an abnormal widening or ballooning
myocardial infraction- heart attack, blood to heart is blocked suddenly and heart muscles begin to die
coronary heart disease- refers to any inference with the coronary arteries with supply blood to the heart muscle itself
risk factors of cardiovascular disease
age- increased risk with age due to gradual deposits
gender- Men are more at risk than women till middle age after risk is similar, due to protective oestrogen till menopause
genetic factors- predisposition due to genetics or family having similar lifestyle
stress- increases blood pressure
smoking- nicotine is a vaso-constrictor which increases BP which damages endothelium
also increases levels of cholesterol in blood
chemicals in cigarettes lead to increased risk of thrombosis
high lipid diet- lipoprotein made in liver of fats cholesterol and proteins
cholesterol transported in blood to damaged ares combined with LDL
so greater conc of LDL greater risk
high LDL treated with statins
HDL is beneficial as absorbs excess cholesterol and return to the liver where it is removed
tranpiration
water loss from the leaves via evaporation
leads to mass transport of water up the Xylem to replace water that has been lost
Translocation
transport of sugars and organic substances from the leaves by the phloem
vascular bundle
Xylem + Phloem
Structure + adaptation of xylem
No cytoplasm or organelles(dead cells)- no obstruction to flow of water
no end walls (continous tube)- allows formation of continuous water columns
lignin- straightens and waterproofs the vessel, also allows adhesion, preventing collapse of vessels under tension caused by negative water pressure within them
lateral pits in cell walls- allows lateral movement around blockages
hollow cells linked end to end- continuous columns of water
cohesion tension theory
open stomata- causes water to diffuse from air spaces to outside (higher wp to lower wp)
transpiration
loss of water from airspaces causes water to move down wp gradient from mesophyll cells to airspaces
lowers wp in meso cells so water moves by osmosis from adjacent meso cells
water lost from leaf is replaced by xylem
Wp gradient across leaf creates tension/pulling force
tension helps to pull water up the xylem via continuous columns of water held by H bonds (Cohesion)
movement of water throught plant is called the transpiration stream and cohesion tension is the theory
(H2O molecules also attracted to walls of Xylem by adhesion, narrows walls of xylem and contributes to negative pressure)
Evidence for Cohesion theory
Daytime tree trunk shrinks due to increased transpiration rates that create more tension and negative pressure in xylem
at night opp occurs
If xylem vessel broken air is drawn in instead of water out, shows negative pressure
cohesion vs adhesion
C= attract between same molecules e.g. H2O to H2O
A= Attraction between diff molecules e.g. H2O and lignin
effect of light intensity on transpiration
stomata opens in light closes in dark
rate of transpiration is higher with increasing light intensity
affect of temp on transpiration
temp increase
increase kinetic energy
increases movement of water molecules
change to water vapour
temp increases rate of evaporation increases
increases transpiration
affect of humidity
% of water vapour in air
higher=closer to 100, lower=closer to 0
the air spaces in leaf = saturated with water Vapour
Air outside contain much less water vapour
greater diff I’m humidity between leaf and outside greater rate of diffusion out of leaf and therefore transpiration
water leaves down wp gradient
affect of air movement + wind speed on transpiration
air movement over leaf moves H20 away from stomatal pores
increase wp gradient
faster wind speed, faster movement of water vapour
so faster rate of transpiration
(xerophytes have sucken stomata trapping water vapour reducing gradient and so transpiration)
measuring rate of transpiration
use potometer
2 types-
flow- measures movement of water up tube
mass- measures chage in mass of water in beaker
flow-
1.leafy shoot of water cut underwater (precation), care taken to prevent water on leaves
2.potometer filled completely with water, ensure no air bubbles (precation)
3.useing rubber tube, shoot fitted to potometer under water(precation)
4.potometer removed from underwater (precation) and all Joints sealed with waterproof jelly (precation)
- air bubble introduced to capillary tube
- as transpiration occurs water moves through the cappilary tube and air bubble moves with
7.distance moved over period of time is recorded, mean calced from repeats
8.volume of water lost over time (transpiration) calced by
PI×r²×L
r=radius of tube
L=distance bubble moved
mass-
1.place shoot In beaker of water, may 2.place layer of oil over water to insure non escapes
3.measure initial mass
4.measure final mass
5.as well as period of time
6.this is volume lost over period of time (transpiration)
(not totally accurate as not all water uptaken is transpired some used in photosynthesis or hydrolysis/condensation reactions)
structure and adaptation of phloem
transport organic substances,source to sink
sieve tube elements(STE) living cells form tube to transport salutes
no nucleus and few organelles-less blockages
do have cytoplasm
sieve tube connected by sieve plates (end walls)
companion cells for each STE, carry out living functions for them
many mitochondria to produce ATP for active transport of solutes
also have ribsomes
and carrier proteins for co transport
cellulose cell walls + thick walls to support + easier flow
no lignin
flow in 2 directions
translocation
movement of solutes–active process
solutes- source to sink
low conc at sink as used up here creating pressure gradient
this is maintained by enzymes converting sugar at sink to storage molecules e.g. starch as well ad respiration
always lower conc at sink than source
mass flow hypothesis
hypothesis as has some evidence against
sucrose is actively transported into sieve tube by companion cells
lowers wp in sieve tube and water enters by osmosis from xylem
produces higher hydrostatic pressure inside sieve tube at source end
mass flow to respiring tissues (down pressure gradient,forces it down/ conc gradient)
sucrose moved into sinks (root and shoot tips) by A transport and facilitated diffusion
(water renters xylem by osmosis at sink end as higher wp in phloem than xylem, lowers pressur,pressure gradient)
evidence for mass flow (for)
supporting-
ring experiment:
if ring of bark (Inc phloem not xylem) is removed
bulge forms above ring
fluid from bulge above has higher coc of sugar than bulge below
as sugar can’t move past this area
evidence for doward flow of sugar and transport in phloem
no sucrose detected below removed section so cells die
experiments with radiotracers:
CO2 contain C14 (radioactive) used
supplied to single leaf by container that surrounds leaf
incorporated into organic substances produced in leaf
moved around plant by translocation
can be traced using autoradiography
under Xray film areas carrying appear black
these black areas show specifically at phloem and nowhere else
shows translocation only by phloem
pressure- investigated with aphids, pierce phloem then bodies are removed leaving mouth parts behind
allows sap to flow out
sap flows out quicker nearer leaves than further down stem
shows pressure gradient
evidence against mass flow
sugar travel to many diff sinks not just one with lower Hydrostatic pressure as model suggests
since plates would create barrier to mass flow
means lots of pressure needed for solutes to get through at reasonable rate
