3.2 - adaptations for transport Flashcards
describe the vascular system of insects
- open circulatory system
- dorsal-tube shaped heart
- respiratory gases not carried in blood
what’s an open circulatory system
- transport medium pumped by heart not contained in vessels, but moves freely
- transport fluid comes into direct contact w/ cells
describe the vascular system of earthworms
- vascularisation
- closed circulatory system
- respiratory gases carried in blood
what’s a closed circulatory system
- blood pumped by heart contained in blood vessels
- blood doesn’t come into direct contact w/ cells
advantages of a closed circulatory system
- blood pressure can be maintained
- blood supply to different organs can vary
- lower volumes of transport fluid required
what type of circulatory system do fish have
single circulatory system
what’s a single circulatory system
- blood travels one circuit
- blood flows through heart + pumped around body before retuning to heart
what type of circulatory system do mammals have
double circulatory system
what’s a double circulatory system
- blood flows through heart twice in 2 circuits
- blood pumped from heart to lungs before returning to heart, then pumped around body, after which returning to heart again
what are the benefits of a double circulatory system
- maintains blood pressure around whole body
- uptake of O2 more efficient
- delivery of O2 + nutrients more efficient
- blood pressure can differ in pulmonary + systemic circuits
describe the double circulatory system in humans
blood flows through heart twice in 2 circuits:
- pulmonary circuit
- systemic circuit
name the 4 chambers of the mammalian heart
- left atrium
- right atrium
- left ventricle
- right ventricle
describe the pathway of blood around the body, naming the structures of the heart
pulmonary vein → left atrium → left ventricle → aorta → body → vena cava → right atrium →. right ventricle → pulmonary artery → lungs
where are the atrioventricular valves found + what’s their function
- found between atria + ventricles
- prevents backflow of blood from ventricles into atria
what are the 2 types of atrioventricular valves
- bicuspid (left side)
- tricuspid (right side)
where are the semilunar valves found + what’s their function
- found between ventricles + arteries
- prevents backflow of blood from arteries into ventricles
name the 5 types of blood vessel
- arteries
- arterioles
- capillaries
- venules
- veins
describe the pathway of blood through the blood vessels
heart → arteries → arterioles → capillaries → venules → veins → heart
what’s the function of arteries
carries blood away from heart to tissues, under high pressure
relate the structure of arteries to their function
- thick muscular walls to handle high pressure w/out tearing
- elastic tissue allows recoil to prevent pressure surges
- narrow lumen to maintain pressre
what’s the function of veins
carry blood towards heart under low pressure
relate the structure of veins to their function
- thin walls due to lower pressure
- valves to ensure blood doesn’t flow backwards
- less muscular + elastic tissue as they dont have to control blood flow
what’s the function of capillaries
form large network through tissue of body + connect arterioles to venules
relate the structure of capillaries to their function
- walls only one cell thick, short diffusion pathway
- v narrow, can permeate tissues + red blood cells can lie flat against wall, reducing diffusion distance
- numerous + highly branched, providing large SA
what’s the function of arterioles
connect arteries + capillaries
what’s the function of venules
connect capillaries + veins
relate the structure of arterioles + venules to their function
- branch off arteries + veins to feed blood into capillaries
- smaller than arteries + veins so change in pressure is more gradual as blood flows to capillaries
what’s the cardiac cycle
- sequence of events involved in one complete contraction + relaxation of heart
- 3 stages: atrial systole, ventricular systole, diastole
describe what happens in ventricular diastole
- heart is relaxed
- blood enters atria, increasing pressure + pushing open AV valves
- allows blood to flow into ventricles
- pressure in heart is lower than in arteries, so SL valves remain closed
describe what happens in atrial systole
- atria contract, pushing any remaining blood into ventricles
- AV valves pushed fully open
describe what happens in ventricular systole
- ventricles contract
- pressure in ventricles increases, closing AV valves to prevent backflow + opening SL valves
- blood flows into arteries
why is cardiac muscle described as myogenic
it initiates its own contraction w/out outside stimulation from nervous impulses
explain how the heart contracts
- SAN initiates + spreads impulse across atria, so they contract
- AVN receives, delays, + then conveys impulse down bundle of his
- impulse travels into purkyne fibres which branch across ventricles, so they contract from bottom up
what’s an electrocardiogram (ECG)
graph showing electrical activity in heart during cardiac cycle
explain the characteristic patterns displayed on a typical ECG
P wave - depolarisation of atria in atrial systole
QRS wave - depolarisation of ventricles during ventricular systole
T wave - repolarisation of ventricles in ventricular diastole
describe the structure + function of erythrocytes
- type of blood cell that’s anucleated + biconcave
- contains haemoglobin which enables the transport of O2 + CO2 to and from tissues
what’s plasma
- main component of blood (yellow liquid) that carries red blood cells cells
- contains proteins, nutrients, mineral ions, hormones, dissolved gases + waste
- distributes heat
describe the role of haemoglobin
present in red blood cells
O2 molecules bind to haem groups + are carried around the body, then released where they are needed in respiring tissues
how does partial pressure of O2 affect oxygen-haemoglobin binding
haemoglobin has variable affinity for O2 depending on partial pressure of O2, p(O2):
- at hig p(O2), oxygen associates to form oxyhaemoglobin
- at low p(O2), oxygen dissociates to form deoxyhaemoglobin
what do oxyhaemoglobin dissociation curves show
saturation of haemoglobin w/ O2 (%) plotted against partial pressure of O2 (kPa)
curves further to left show that haemoglobin has higher affinity for O2
explain the shape of oxyhaemoglobin dissociation curves
sigmoidal curve (s-shaped):
- when first O2 molecule binds, it changes the tertiary structure of haemoglobin so its easier for second + third molecules to bind
- third molecule changes tertiary structure of haemoglobin so its more difficult for fourth molecule to bind
how does fetal haemoglobin differ from adult haemoglobin
has higher affinity for O2 than adult haemoglobin due to presence of 2 different subunits that allow O2 to bind more readily
why is higher affinity of fetal haemoglobin important
enables fetus to obtain O2 from mothers blood
compare dissociation curves of adult + fetal haemoglobin
fetal curves to left
at same partial pressure, % O2 saturation is greater
predict the shape of the dissociation curves of animals adapted to low O2 level habitats
- haemoglobin has greater affinity for O2
- haemoglobin saturated at lower p(O2)
- dissociation curves to left
how is CO2 carried from respiring cells to lungs
- transported in aqueous solution in plasma
- as hydrogen carbonate ions in plasma
- carried as carbaminohaemoglobin in blood
what’s the chloride shift
- process by which chloride ions move into erythrocytes for hydrogen carbonate ions which diffuse out of erythrocytes
- one to one exchange
whys the chloride shift important
maintains electrochemical equilibrium of cell
what’s the function of carbonic anhydrase
catalyses the reversible reaction between water + CO2 to produce carbonic acid
equations to show the formation of hydrogen carbonate ions in plasma
carbonic anhydrase enzyme catalyses:
CO2 + H2O ⇌ H2CO3 (carbonic acid)
carbonic cider dissociates:
H2CO3 ⇌ HCO3- (hydrogen carbonate ions) + H+
state the bohr effect
loss of affinity of haemoglobin for O2 as the partial pressure of CO2 increases
explains he role of carbonic anhydrase in the bohr effect
- carbonic anhydrase present in red blood cells
- catalyses reaction of CO2 + water to form carbonic acid, dissociating to produce H+ ions
- H+ ions combine w/ haemoglobin to form haemoglobinic acid
- encourages O2 to dissociate from haemoglobin
what’s tissue fluid
- fluid surrounding cells of animals
- same composition as plasma but docents contain red blood cells or plasma proteins
describe the different pressure involved in formation of tissue fluid
- hydrostatic pressure = higher at arterial end of capillary than venous end
- oncotic pressure = changing water potential of capillaries as water moves out, induced by proteins in plasma
how is tissue fluid formed
as blood pumped through increasingly smaller vessels, hydrostatic pressure is greater than oncotic pressure, so fluid moves out of capillaries
then exchanges substances w/ cells
why does blood pressure fall along capillary
- friction
- lower volume of blood
what happens at venous end of capillary
- oncotic pressure greater than hydrostatic pressure
- fluid moves down water potential gradient back into capillaries
where does some tissue fluid drain
into lymphatic system + eventually returns to blood
define vascular bundle
- vascular system in herbaceous dicotyledonous plants
- consists of 2 transport vessels, xylem + phloem
describe the structure + function of the vascular system in roots of dicotyledons
xylem arranged in X shape to provide resistance against force
phloem found as patches between arms
surrounded by endodermis, aiding water passage
describe the structure + function of the vascular system in stem of dicotyledons
vascular bundles organised around central pith
xylem on inside of bundle providing support + flexibility
phloem on outside of bundle
cambium found between the 2
what structure in plants adapted for uptake of water + minerals
root hair cell
how is water taken up from soil
- root hair cells absorb minerals by active transport, reducing water potential of root
- water potential of root hair cells lower than that of soil
- water moves into root by osmosis
outline how plant roots adapted for absorption of water + minerals
plant roots composed of millions of root hair cells which have:
- long hairs extending from cell body, increasing SA for absorption
- many mitochondria producing energy for active transport of mineral ions
state the 3 pathways by which water moves through root
- apoplast pathway
- symplast pathway
- vacuolar pathway
describe the apoplast pathway
water moves through intercellular spaces between cellulose molecules in cell wall
diffuses down water potential gradient by osmosis
describe the symplast pathway
water enters cytoplasm through plasma membrane + moves between adjacent cells via plasmodesmata
water diffuse down water potential gradient by osmosis
describe the vacuolar pathway
water enters cytoplasm through plasma membrane + moves between vacuoles of adjacent cells
water diffuses down water potential gradient by osmosis
describe the structure + function of the endodermis
- innermost layer of cortex of dicot root
- impregnated w/ suberin which forms casparian strip
- endodermal cells actively transport mineral ions into xylem
what’s the function of the casparian strip
- blocks apoplast pathway, forcing water through symplast route
- enables control of movement of water + minerals across root + into xylem
what molecule makes casparian strip waterproof
suberin
relate the structure of xylem to its function
- long, continuous column shade of dead tissue, allowing transport of water
- containing bordered pits, allowing sideways movement of water between vessels
- walls impregnated with/ lignin, providing structural support
define transpiration
- loss of water vapour from parts of plant exposed to air due to evaporation + diffusion
- consequence of gaseous exchange; occurs when plant opens stomata to exchange O2 + CO2
what’s the transpiration stream
flow of water from roots to leaves in plants, where its lost by evaporation to environment
how does water move up stem
- root pressure
- cohesion tension theory
- capillarity
what is root pressure
force driving water into + up xylem by osmosis due to active transport of minerals into xylem by endodermal cells
explain the cohesion tension theory
- water molecules form H bonds w/ each other, causing them to ‘stick’ together
- surface tension of water also creates sticking effect
- as water lost through transpiration, more is raw n up stem from roots
define capillarity
tendency of water to move up xylem, against gravity, due to adhesive forces preventing water column dropping back
state the factors affecting the rate of transpiration
- light
- temperature
- humidity
- air movement
how does temperature affect transpiration rate
higher temp increases random motion + rate of evaporation, increasing rate of transpiration
how does light affect rate of transpiration
higher light intensity increases rate of photosynthesis, causing more stomata to open for gas exchange, increasing rate of transpiration
how does humidity affect rate of transpiration
high humidity means water content of air next to leaf is high
reduces conc gradient, decreasing rate of transpiration
how does air movement affect rate of transpiration
large amounts of air movement blow moist air away from leaves, creating steep concentration gradient, increasing rate of transpiration
what’s a hydrophyte
plant adapted to live + reproduce in v wet habitats e.g: water lilies
adaptations of hydrophytes allowing them to live in wet conditions
- thin/absent waxy cuticle
- stomata often open
- wide, flat leaves
- air spaces for buoyancy
what’s a xerophyte
plant adapted to live + reproduce in dry habitats where water availability is low
e.g: cacti + marram grass
adaptations of xerophytes allowing them to live in dry conditions
- small/rolled leaves
- densely packed mesophyll
- thick waxy cuticle
- stomata often closed
- hairs to trap moisture
what are mesophytes
- terrestrial plants adapted to live in environments w/ average conditions + an adequate water supply
- have feature that enable survival at unfavourable times of the year
relate the structure of phloem to its function
- sieve tube elements transport sugars around plant
- companion cells designed for active transport of sugars into tubes
- plasmodesmata allow communication + exchange of substances between sieve tubes + companion cells
what are cytoplasmic strands
small extensions of cytoplasm between adjacent sieve tube elements + companion cells
describe the function of cytoplasmic strands
- allow communication + exchange of materials between sieve tube elements + companion cells
- hold nucleus in place
define translocation
movement of organic compounds in phloem, from sources to sink
define translocation
movement of organic compounds in phloem, from sources to sink
summarise the mass flow hypothesis of translocation
- sugar loaded into sieve tubes via active transport
- lowers water potential causing water to move in from xylem
- hydrostatic pressure causes sugars to move towards sink
give evidence for the mass flow hypothesis
- sap released when stem is cut, must be pressure in phloem
- sap exuding from stylet or aphid inserted into sieve tues provides evidence that sugars are carried in phloem
- higher sucrose conc in leaves than roots
- autoradiographs produced using CO2 labelled with/ radioactive carbon provide evidence for translocation in phloem
what’s autoradiography
technique used to record distribution of radioactive material within a specimen
what’s a potometer
apparatus used to measure water uptake from cut shoot
