exchange

Question 1

SA:V ratio

Answer 1

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

Question 2

Fick’s law

Answer 2

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

Question 3

SA and Metabolic rate

Answer 3

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

Question 4

single called organisms

Answer 4

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

Question 5

specialised gas exchange

Answer 5

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

Question 6

what makes a good gas exchange surface

Answer 6

Large SA
large conc gradient
thin exchange surface so short diffusion distance

Question 7

gas exchange in insects

Answer 7

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

Question 8

Tracheal system adaptations

Answer 8

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

Question 9

Insects- features to reduce water loss

Answer 9

rigid outer skeleton- waterproof exoskeleton, impermeable

spirituals close

small hairs around spiricals trap water to reduce water potential gradient

Question 10

Gas exchange in fish

Answer 10

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

Question 11

Adaptation for efficient gas exchange- gills

Answer 11

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

Question 12

gas exchange- dicotyledonous plants

Answer 12

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

Question 13

leaf adaptations for efficient gad exchange

Answer 13

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

Question 14

adaptation of leaf ti reduce water loss

Answer 14

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

Question 15

Xerophytes

Answer 15

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

Question 16

Lung anatomy

Answer 16

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

Question 17

Alveoli structure and adaptations

Answer 17

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

Question 18

ventilation

Answer 18

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

Question 19

pulmonary ventilation

Answer 19

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

Question 20

what is a risk factor

Answer 20

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

Question 21

risk factors for lung disease

Answer 21

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

Question 22

linear vs non linear relationship

Answer 22

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

Question 23

correlation

Answer 23

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

Question 24

Probability(P) Values

Answer 24

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

Question 25

statistical tests

Answer 25

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

Question 26

correlation coefficient

Answer 26

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

Question 27

Writing out hypothesis

Answer 27

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

Question 28

Accepting/rejecting hypothesis

Answer 28

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

Question 29

Haemoglobin- basic knowledge

Answer 29

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

Question 30

percentage saturation of haemoglobin

Answer 30

amount of O2 combined

100% 4/4,oxygen molecules bonded

75% 3/4

50% 2/4

25% 1/4

Question 31

oxygen dissociation curve

Answer 31

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)

Question 32

affinity

Answer 32

natural attraction to something e.g. haemoglobin to O2

Question 33

Partial pressure (p)

Answer 33

the amount of a particular gas in a mixture of gases or a solution

Question 34

pO2 in lungs

Answer 34

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

Question 35

pO2 in tissue

Answer 35

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

Question 36

why is O2 disassociation curve S shaped

Answer 36

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

Question 37

diff types of haemoglobin

Answer 37

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

Question 38

Mother and foetus Dissociation curve

Answer 38

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

Question 39

Circulatory system

Answer 39

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)

Question 40

heart functions plus adaptations

Answer 40

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

Question 41

structure of heart

Answer 41

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

Question 42

The cardiac cycle

Answer 42

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

3. 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

Question 43

cardiac output

Answer 43

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

Question 44

arteries

Answer 44

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

Question 45

arterioles

Answer 45

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

Question 46

veins

Answer 46

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

Question 47

capillaries

Answer 47

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

Question 48

tissue fluid formation

Answer 48

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

Question 49

Cardiovascular disease

Answer 49

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

Question 50

risk factors of cardiovascular disease

Answer 50

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

Question 51

tranpiration

Answer 51

water loss from the leaves via evaporation

leads to mass transport of water up the Xylem to replace water that has been lost

Question 52

Translocation

Answer 52

transport of sugars and organic substances from the leaves by the phloem

Question 53

vascular bundle

Answer 53

Xylem + Phloem

Question 54

Structure + adaptation of xylem

Answer 54

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

Question 55

cohesion tension theory

Answer 55

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)

Question 56

Evidence for Cohesion theory

Answer 56

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

Question 57

cohesion vs adhesion

Answer 57

C= attract between same molecules e.g. H2O to H2O
A= Attraction between diff molecules e.g. H2O and lignin

Question 58

effect of light intensity on transpiration

Answer 58

stomata opens in light closes in dark

rate of transpiration is higher with increasing light intensity

Question 59

affect of temp on transpiration

Answer 59

temp increase

increase kinetic energy

increases movement of water molecules

change to water vapour

temp increases rate of evaporation increases

increases transpiration

Question 60

affect of humidity

Answer 60

% 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

Question 61

affect of air movement + wind speed on transpiration

Answer 61

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)

Question 62

measuring rate of transpiration

Answer 62

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)

5. air bubble introduced to capillary tube
6. 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)

Question 63

structure and adaptation of phloem

Answer 63

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

Question 64

translocation

Answer 64

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

Question 65

mass flow hypothesis

Answer 65

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)

Question 66

evidence for mass flow (for)

Answer 66

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

Question 67

evidence against mass flow

Answer 67

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