Topic 3 - Exchanging substances Flashcards
describe the relationship btwn size and structure of an organism and its SA:V
as size increases, SA:V tends to decrease
more thin/flat/folded/elongated structures increase SA:V
how is SA:V calculated
divide surface area by volume
suggest an advantage of calculating SA:mass for organisms instead of SA:V
easier/quicker to find/more accurate because irrgular shapes
what is metabolic rate
the amount og energy used up by an organism within a given period of time
how could we measure metabolic rate
oxygen uptake as used in aerobic respiration to make ATP for energy release
explain the relationship btwn SA:V and metabolic rate
as SA:V increases, metabolic rate increase because:
- rate of heat loss per unit body mass increases
- organisms need a higher rate of respiration
- to release enough heat to maintain a constant body temperature i.e. replace lost heat
explain the adaptations that facilitate exchange as SA:V reduces in larger organisms
- changes body shape to increase SA:V and overcome long diffusion distance/pathway
- development of systems such as specialised surface/organ for gaseous exchange = increases SA:V and overcomes long diffusion distance/pathway, maintain a concentration gradient for diffusion e.g. ventilation/good blood supply
explain how the body surface of a single celled organism is adapted for gas exchange
- thin flat shape, large SA:V
- short diffusion distance to all parts of cell = rapid diffusion e.g. of O2 CO2
state 3 parts of the tracheal system of an insect
spiracles, tracheae, tracheoles
what are spiracles
pores on surface that can open/close to allow diffusion
what are tracheae
large tubes full of air that allow diffusion
what are tracheoles
smaller branches from tracheae, permeable to allow gas exchange with cells
explain how an insect’s tracheal system is adapted for gas exchange
- tracheloles have thin walls = short diffusion distance to cells
- high numbers of fhighly branched tracheoles = short diffusion distance to cells so large SA
- tracheae provides tubes full of air = fast diffusion
- contraction of abdominal muscles changes pressure in body = air moves in and out so maintains conc. gradient
- fluid in end of tracheoles drawn into tissues by osmosis durinng excercise (lactate produced in anaerobic respiration lowers water potential of cells) = diffusion is fater through air rather than in fluid
explain the structural and functional compromises in terrestrial inisects that allow efficient gas exchange while limitinng water loss
- thick waxy cuticle/exoskeleton = increases diffusion distance so less water is loss
- spiracles can open to allow gas exchannge and close to reduce water loss
- hairs around spiracles trap moist air, reducing water potential gradient so less water loss
expxlain how the gills of fish are adapted for gas exchange
- gills are made of many filaments covered with many lamella = increased surface area for diffusion
- thin lamellae wall/epithelium = short diffusion distance btwn water/blood
- lamellae have a large number of capillaries = removes O2, brings CO2 quickly maintains conc. gradient
what is the counter current flow
- blood and water flow in opposite directions through/over lamellae
- oxygen conc. always higher in water so maintains conc. gradient of O2 btwn water and blood for diffusion along whole length of lamellae
explain how the leaves of dicotyledonous plants are adapted for gas exchange
many stomata (high density) - large SA for gas exchange
spongy mesophyll contains air spaces - large surface area for gases to diffuse through
thin - short diffusion distance
state 7 structures you’d find in a leaf cross section
waxy cuticle, upper and lower epidermis, palisade mesophyll, spongy mesophyll, stomata, guard cell
explain structural and functional compromises in xerophytic plants that allow efiicient gas exchange while limiting water loss
- thicker waxy cuticle increases diffusion distance so less evaporation
- sunken stomato in pets, rolled leaves, hairs = trap water vapour/protect stomata from wind, reduced water potential gradient btwn leaf/air so less evaporation
- spines/needles reduce SA:V
describe the gross structure of the human gas exchange
trachea, bronchi, bronchioles, alveoli, capillary network
explain the essential features of the alveolar epithelium that makes it adapted as a surface for gas exchange
flattened cells - 1 cell thick = short diffusion distance
folded = large SA
permeable - allows diffusion of O2, CO2
moist - gases can dissolve for diffusion
good blood supply from large network of capillaries = maintains conc. gradient
describe how gas exchange occurs in the lungs
oxygen diffuses from alveolar air space into blood down its conc. gradient across alveolar epithelium then across capillary endothelium
explain the importance of ventilation
brings in air containing higher conc. of oxygen and removes air w lower conc. of oxygen maintaining conc. gradient
explain how humans breathe in (inspiration)
diaphragm muscles contract - flattens
external intercostal muscles contract, internal intercostal muscles relax - ribcage pulled up and out
increasing volume and decreasing pressure in thoracic cavity
air moves into lungs down pressure gradient
explain how humans breathe out (expiration)
diaphragm relaxes - moves upwards
external intercostal muscles relax, intercostal muscles contract
decreasing volume and increasing pressure in thoracic cavity
air moves lungs down pressure gradient
suggest why expiration is normally passive at rest
internal intercostal muscles do not normally need to contract
expiration is aided by elastic recoil in alveoli
suggest how different lung diseases reduce the rate of gas exchange
thickened alveolar tissue increases diffusion distance
alveolar wall breakdown reduces surface area
reduce lung elasticity = lungs expand/recoil less so it reduces conc. gradient of O2/CO2
suggest how different lung diseases affect ventilation
reduce lung elasticity (e.g. fibrosis, build up scar tissue) - reduces volume of air in each breath (tidal volume) and reduces the maximum volume of air breathed out in one breath (forced vital capacity)
narrow airway/reduce airflow in and out of lungs(e.g. asthma - inflamed bronchi) - reducing maximum volume of air breathed out in 1 second
reduced gas exchange - increased ventilation rate to compensate for reduced oxygen in blood
suggest why people with lung disease experience fatigue
cells receive less oxygen - rate of aerobic respiration reduced = less ATP made
suggest how you can analyse and interpret data to the effects of pollution, smoking and other risk factors on the incidence of lung disease
describe overall trend e.g. positive/negative correlation btwn risk factor and disease
manipulate data e.g. calculate % change
interpret standard deviations - overlap suggests difference in means are likely due to change
use statistical tests to identify whether difference/correlation is significant or due to chance
suggest how you can evaluate the way in which experimental data led to statutory restrictions on the sources of risk factors
analyse and interpret data and identify what does or doesn’t support statement
evaluate the method - was it representative enough, valid, showed effects and could show comparison:
- sample size,
- participant diversity
- control groups and variales
- duration
evaluate context - has a broad generalisation been made from a specific set of data
are there other risk factors that could have affected results
state 3 statistical tests
chi-squared
correlation coefficient
student’s t test
state when you would use a correlation coefficient test
when examining an association btwn 2 sets of data
state when you would use a student’s t test
when comparing the means of 2 sets of data
state when you would use a chi-squared test
for categorical data
what is correlation
when change in one variable is reflected by a change in another - identified on a scatter diagram
what is causation
when a change in one variable causes a change in another variable
what is the difference btwn correlation and casual relationships
correlation and causation
correlation doesn’t mean causation - other factors may be involved
explain what happens in digestion
large insoluble biological molecules are hydrolysed to smaller soluble molecuies that are small enough to be absorbed across cell membranes into blood
describe the digestion of starch in mammals
amylase produced by salivary glands hydrolyse starch to maltose
membrane bound maltase hydrolyses maltose into glucose
hydrolysis of glycosidic bond
describe the digestion of disaccharides in mammals
maltase -> maltose = glucose + glucose
lactase -> lactose = galactose + glucose
sucrase -> sucrose = fructose + glucose
hydrolysis of glycosidic bond
describe the digestion of lipids in mammals including action of bile salts
bile salts emulsify lipids causing them to form smaller lipid droplets
this increases SA of lipids for increased/faster lipase activity
lipase (pancreas) hydrolyses lipids -> monoglycerides + fatty acids
hydrolysis of ester bond
Describe the digestion of proteins by a mammal
Endopeptidases - hydrolyse internal peptide bonds w/n a polypeptide = smaller peptides so more ends, increased SA for exopeptidasees
Exopeptidases hydrolyse terminal peptide bonds at the ends of polypeptides - single amino acid
Membrane bound dipeptidases hydrolyse bond btwn a dipeptide - 2 amino acids
hydrolysis of peptide bonds
suggest why membrane-bound enzymes are important in digestion
membrane bound enzymes are located on cell membranes of epithelial cells lining ileum
through hydrolysisi at the site of absorption, conc. gradient is maintained for absorption
describe the pathway for absorption of products of digestion in mammals
lumen of ileum -> cells lining ileum -> blood
Describe the absorption of amino acids and monosaccharides in mammals
Co-Transport:
- Na+ actively transported from epithelial cells lining ileum to blood by Na+/K pump
- establishing a conc. gradient of Na+ (higher in lumen than epithelial cell)
- Na+ enters epithelial cell down its conc. gradient against its conc. gradient via a co-transporter protein
- Glucose moves down a conc. gradient into blood via facilitated diffusion
Describe the role of micelles
they contain bile salts, monoglycerides and fatty acids:
- make monoglycerides and fatty acids = more soluble in water
- carry/release fatty aciids and monoglycerides to cell/lining of ileum
- maintain high conc. of fatty acids to cell/lining
Describe the absorption of lipids by a mammal
- monoglycerdies/fatty acids absorbed by diffusion
- triglycerides reformed in epithelial cells and aggregate into globules
- globules coated with proteins forming chylomicrons which are then packaged into vesicles
- vesicles move to cell membrane and leave via exocytosis, enter lymphatic vessels and eventually return to blood circulation
describe the role of red blood cells and haemoglobin in oxygen transport
- red blood cells contain lots of haemoglobin - no nucleus, biconcave, high SA:V, short diffusion path
- haemoglobin associates with/binds/loads O2 at gas exchange surfaces where partial pressure of O2 (pO2) is high
- this forms oxyhaemoglobin which transports O2 (each can carry 4 O2)
- haemoglobin dissociates from/unloads O2 near cells/tissues where pO2 is low
describe the structure of haemoglobin
protein with a quaternary structure, made of 4 polypeptide chains. each chain contains a haem group containing on iron ion (FE2+)
they are a group of chemically similar molecules found in many different organisms
Describe the loading, transport and unloading of oxygen in relation to the oxyhaemoglobin dissociationi curve
areas with low pO2 (respiring tissues):
- haemoglobin has low affinity for O2
- so O2 readily unloads/dissociates with haemoglobin
- % saturation is low
areas with high pO2 (gas exchange surfaces):
- haemoglobin has a high affinity for O2
- O2 readily loads/associates with haemoglobin
- % saturation is high
explain how the cooperative nature of oxygen binding results in an S-shaped oxyhaemoglobin dissociation curve
- binding first oxygen changes tertiary/quaternary structure of haemoglobin
- this uncovers haemoglobin group binding sites, making further binding of oxygens easier
Describe evidence for the cooperative nature of oxygen binding
- a low pO2 as oxygen increases there is little/slow increase in % saturation of haemoglobin with oxygen. first oxygen is binding
- at higher pO2, oxygen increases there is a big/rapid increase in % saturation of haemoglobin with oxygen, showing it has gotten easier for oxygens to bind
what is the bohr effect
effect of Co2 conc. on dissociation of oxyhaemoglobin -> curve shifts to the right
explain the effect of CO2 conc. on the dissociation of oxyhaemoglobin
- increasing blood CO2 e.g. due to increased rate of respiration
- lowers blood pH (more acidic)
- reducing haemoglobin’s affinity for ooxygen as shape/tertiary/quaternary structure changes slightly
- more/faster unloading of oxygen to respiring cells at a given pO2
hohw does the curve of the pO2 and % saturation of haem w O2 provide evidence of the effect of CO2 conc. on dissociationg of haem
at a given pO2 % saturation of haem is lower
explain the advantage of Bohr effeect
more dissociation of oxygen -> faster aerobic respiration/less aerobic respiration -> more ATP produced
explain why different types of haemoglobin can have different oxygen transport properties
different types of haem are made of polypeptide chains with slightly different amino acid sequences, resulting in different tertiary/quaternary structures/shape -> different affinities of oxygen
explain how organisms can be adapted to their environment by having different types of haemoglobin with different oxygen transport properties if the curve on the graph shifts left
curve shifts left = haem has a higher affinity for O2
- more O2 associates with haem more readily at gas exchange surfaces where pO2 is lower
e.g. organisms in low environments - high altitudes, underground or foetuses
explain how organisms can be adapted to their environment by having different types of haemoglobin with different oxygen transport properties if the curve on the graph shifts right
curve shifts right = haem has a lower affinity for O2
- more O2 dissociates from haem more readily at respiring tissues where more O2 is needed
e.g. organisms with high rates of respiration/metabolic rate (may be small or active)
Describe the general pattern of blood circulation in a mammal
closed double circulatory system - blood passes through the heart twice for every circuit around body:
deoxygenated blood in the right side of the heart is pumped to lungs; oxygenated returns to the left side
oxygenated blood in the left side of the heart is pumped to the rest of the body; deoxygenated returns to the right
suggest the importance of a double circulatory system
prevents mixing of oxygenated/deoxygenated blood so blood pumped to the body is fully saturated with oxygen for aerobic respiration
blood can be pumped to body at higher pressure after being lower from lungs, substances can be taken to/removed from body cells quicker/more efficiently
name the blood vessels entering the heart and lungs and their role
vena cava - transports deoxygenated blood from respiring tissues -> heart
pulmonary artery - transports deoxygenated blood from heart -> lungs
name the blood vessels leaving the heart and lungs and their role
pulmonary vein - transports oxygenated blood from lungs -> heart
aorta - transports oxygenated blood from heart -> respiring body tissues
name the blood vessels entering and leaving the kidneys
renal arteries - oxygenated blood to the kidneys
renal veins - deoxygenated blood to vena cava from kidneys
name the blood vessels that carry oxygennated blood to the heart muscle
coronary arteries are located on the surface of the heart, branching from the aorta
what are the names of the valves
atrioventricular and semilunar valve
suggeset why the wall of the left ventricle is thicker than that of the right
thicker muscle to contract with greater force to generate higher pressure to pump blood around entire body
explain the presssures and volume changes and associated valve movements during the diastole part of the cardiac system which maintains a unidirectional flow of blood
- atria and ventricles relax so volume increases, pressure decreases
- semilunar valves shut when pressure in arteries exceeds pressure in ventricles
- atrioventricular valves open when pressure in atria exceeds pressure in ventricles
- blood fills atria via veins and flows passively to ventricles
explain the presssures and volume changes and associated valve movements during the atrial systole part of the cardiac system which maintains a unidirectional flow of blood
- atria contract = volume deacreases, pressure increases
- atrioventricular valves open when pressure in atria exceeds pressure in ventricles
- semilunar valves remain shut as pressure in arteries exceeds pressure in ventricles
- blood pushed into ventricles
explain the presssures and volume changes and associated valve movements during the ventricular systole part of the cardiac system which maintains a unidirectional flow of blood
- ventricles contract = volume decreases, pressure increases
- atrioventricular valves shut when pressure in ventricles exceeds pressure in atria
- semilunar valves open when pressure in ventricles exceeds pressure in arteries
- blood pushed out of the heart through the arteries
explain how graphs showing pressure or volulme changes during the cardiac cycle can be interpreted
e.g. how to identify when valves are open/closed
- semilunar valves closed:
pressure in [named] artery is higher than in the ventricle to prevent backflow of blood from artery to ventricles - semilunar valves open:
pressure in ventrile is higher than in [named] artery so blood flows from ventricle to artery - atrioventricular valves closed:
pressure in ventricle higher than atrium to prevent backflow of blood from ventricles to atrium - atrioventricular valves open:
pressure in atrium is higher than in ventricle so blood flows from atrium to ventricle
what is the equation for caridac output
cardiac output = stroke volume x heart rate
what is stroke volume
volume of blood pumped in each heart beat
what is cardiac output
volume of blood pumped out of heart per min
how can heart rate be calculated from cardiac cycle data
heart rate = 60 seconds / length of on cardiac cycle (seconds)
what is the function of arteries
carry blood away from heart at high pressure
how does the structure of arteries relate to its function
- thick smooth muscle tissue can contract and control/maintain blood flow/pressure
- thick elastic tissue can stretch as ventricles contract and recoil as ventricles relax to reduce pressure surges/even out blood pressure/maintain high pressure
- thick wall to withstand pressure and stop from bursting
- smooth/foolded endothelium reduces friction/can stretch
- narrow lumen to increase/maintain high pressure
what is the funcntion of arterioles
to direct blood to different capillaries/tissues
what are arterioles
the divion of arteries to smaller vessels
explain how the structure of arterioles relates to its function
- thicker smooth muscle layer than arteries:
contracts -> narrow lumen (vasoconstriction) reduces blood flow to capillaries
relaxes -> widens lumen (vasodilation) increases blood flow to capillaries - thinner elastic layer = pressuree surges are lower due to being further away from the heart
what is the fucntion of veins
carry blood back to heart at lower pressure
explain how the structure of veins relates to their function
- wider lumen than arteries = less resistance to blood flow
- very little elastic + mucles tissue due to lower blood pressure
- valves prevent the backflow of blood
what is the function of the capillaries
to allow efficient exchange of substances btwn blood and tissue fluid
explain how the structure of capillaries relates to their function
- wall is thin, one cell thick layer of endothelial cells so reduces diffusion distance
- capillary bed is a large network of branched capillaries -> increases SA for diffusion
- smaller diamter/narrow lumen -> reduces blood flow rate so more time for diffusion
- pores in walls btwn cells = larger substances can move through
explain the formation of tissue fluid
arteriole end of capillaries:
higher blood/hydrostatic pressure inside capillaries due to contractioni of ventricles than tissue fluid so net outward force
forcing water and dissolved substances out of capillaries
large plasma proteins remain in the capillary
explain the return of tissue fluid to the circulatory system
at the venulee end of capillaries:
hydrostatic pressure reduces as fluid leaves capillary due to friction
due to water loss an increasing conc. of plasma proteins lowers water potential in capillary below that of tissue fluid
water enters capillaries from tissue fluid by osmosis down a water potential gradient
excess water is taken up by lymph capillaries and returned to circulatory system through veins
suggest and explain the causes of excess tissue fluid formation
- low conc. of protein in bloow plasma or high salt conc.
water potential in capillary not as low - water potential gradient is reduced
more tissue fluid formed at arteriole end/less water absorbed at venule end by osmosis - high blood pressure = high hydrostatic pressure
increases outward pressure from arterial end and reduces inward pressure at venule end
more tissue fluid formed at arteriole end/less water absorbed at venule end by osmosis
lymph system may not be able to drain excess fast enough
what is a risk factor
an aspect of a person’s lifestyle or substance in a person’s body/environment that has been shown to be linked to an increased rate of disease
state a few examples of risk factors for cardiovascular disease
age, high salt or saturated fat in diet, smoking, lack of excercise, genes
describe the function of xylem tissue
transports water and mineral ions through the stem, up the plant to the leaves of plants
suggest how xylem tissue is adapted for its function
- cells joined with no end walls forming a long continuous tube = water flows at a continuous column
- cells contain no cytoplasm/nucleus = easier water flow/no obstructions
- thick cell wall with lignin = provides support.withstands tension/prevents water loss
- pits in side walls which allows laterall water movements
explain the cohesion-tension theory of water transport in the xylem
leaf:
- water lost from leaf by transpiration it evaporates from mesophyll cells into air spaces and water vapour diffuese through open stomata
- reducing water potential of mesophyll cells
- water drawn out of xylem down a water potential gradient
xylem:
- creating tension in the xylem
- hydrogen bonds result in cohesion btwn water molecules so water is pulled up as a continuous column
- water also adheres to the walls of xylem
root:
- water enters roots via osmosis
Describe how ot set up a potometer
- cut a shoot underwater at a slant - prevents air enetering the xylem
- assemble the potometer with capillary tube end and submerge it under a beaker of water
- insert shoot underwater
- ensure apparatus is watertight/airtight
- dry leaves and allow time for shoot to accclimatise
- shut tap to reservoir
- form an air bubble wuickly remove end of capillary tube from water
what does a potometer do
it estimates transpiration rate by measuring water uptake
describe how a potometer can be used to measure the rate of transpiration
- record position of air bubble
- record distance moved in a certain amount of time e.g. 1 minute
- calculate volume of water uptake in a given time: use the radius of capillary tube to calculate cross sectional area of water (pi r squared), multiply this by distance moved by bubble
- calculate rate of water uptake by dividing volume by time taken
describe how a potometer can be used to investigate the effect of a named environmental variable on the rate of transpiration
measure rate of transpiration and change on variable at a time - wind, humidity, light or temperature
e.g. set up a fan, spary water in a plastic bag and wrap around the plant, change distance of a light source, change temperature of room
- keep all other variables constant
suggest limitaitons in using a potometer to measure rate of transpiration
- rate of water uptake might not be same as rate of transpiration: water is used for support,turgidity, used in photosynthesis and produced respiration
- rate of movement through shoot in potometer may not be same as rate of movement through shoot of whole plant: shoot in potometer has no roots whereas a plant does. xylem cells are very narrow
suggest how humidity affects rate of transpiration
increasing humidiity decreases the rate of transpiration
explain why increasing humidity decreases rate of transpiration
more water in air so it has a higher water potential, decreasing water potential gradient from leaf to air. water evaporates slower
suggest the effect of light intensity on the rate of transpiration
increasing light intensity increases the rate of transpiration
explain why increasing light intensity increases rate of transpiration
stomato open in light to let CO2 in for photosynthesis, allowing more water to evaporate faster. stomata close when its dark so there is a low transpiration rate
suggest the effect of temperature on rate of transpiration
increasing temperature increases rate of transpiration
explain why increasing temperature increases rate of transpiration
water molecules gain kinetic energy as temperature increases so water evaporates faster
suggest the effect of wind intensity on rate of transpirationi
increasing wind intensity increases rate of transpiration
explain why increasing wind intensity increases rate of transpiration
wind blows away water moelcules from around stomata decreasing water potential of air around stomata, increasing water potential gradient so water evaporates faster
describe the funciton of phloem tissue
transports organic substances e.g sucrose in plants
suggest how phloem tissue is adapted for its function
sieve tube elements
- no nucleus/few organelles = maximum space for/easier flow of organic substances
- end walls btwn cells perforated sieves plates
companion cells
- many mitochondria = high rate of respiration to make ATP for active transport of solutes
what is translocation
movement of assimilates/solutes such as sucrose from soruce cells to sink cells by mass flow
explain the mass flow hypothesis for translocation in plants
- at source, sucrose is actively transported into phloem sieve tubes/cells by companion cells
- this lowers water potential in sieve tubes os water enters from xylem by osmosis
- this increases hydrostatic pressure in sives tubes at source, creating hydrostatic pressure gradient
- mass flow occurs, movement from source to sink
- at sink, sucrose is removed by active transport to be used by respiring cells or stored in storage organs
describe the use of tracer expirments to investigate transport in plants
- leaf supplied with a radioactive tracer e.g. CO2 containing radioactive isotope 14C
- radioactive carbon incorporated into organic substances during photosynthesis
- these move around plant by translocation
- movement tracked using autoradiography or a Geiger counter
describe the use of ringing experiements to investigate transport in plants
- remove/kill phloem e.g. remove a ring or bark
- bulge forms on source side of ring
- fluid from bulge has a higher conc. of sugars thann below which shows sugar is transported in phloem
- tissue below the ring die as it cannot get organic substances
suggest some points to consider when interpreting evidence from tracer and ringing experiments and evaluating evidence for/against the mass flow hypothesis
- is there evidence to suggest phloem/respiration/active transport is invovled
- is there evidence to show movements is from source to sink what are these in the experiment?
- is there evidence to suggest movement is from high to low hydrostatic pressure
- could movement be due to another factor e.g. gravity
what is the difference btwn transpiration and transpiration stream
transpirtaion is the eloss of water vapour from leaves.
transpiration stream is the constant movement of water through the plant
