Topic 4 Exhange And Transport Flashcards
what adaptations of respiratory surfaces can be taken to provide sufficient diffusion?
- thinner membrane
- higher SA (:V ratio)
- some means of maintaining conc gradient
what are insects’ external called?
exoskeleton
what are exoskeletons made up of?
chitin
what are some uses of chitin in insects?
- provide strength and flexibility
- impermeable to oxygen, so barrier to gas exchange
what is the gaseous route in insects?
spiracles > tracheae > tracheoles >
in what conditions would insects close their spiracles?
hot and dry
what are insect ‘blood’ called?
haemolymph
how does fish obtain oxygen?
from water using internal gills. they have gill filaments protected by the operculum, in the buccal cavity
how does the gill ventilate?
maintained by changes of water pressure.
mouth opens and closes forcing water across gills
when mouth opens, operculum shuts
what is the mechanism used in fish gaseous exchange?
counter current flow
to maintain a conc gradient along the whole length of blood-water boundary
where are the lungs of locusts housed in?
thorax
what is the thorax?
an air tight chamber formed by the rib cage and intercostal muscles, and domed floor (diaphragm)
what happens during a mammal inspiration?
external intercostal muscles contract,
ribs move up and out
diaphragm down and contracts
what happens during a mammal expiration?
external intercostal muscles relax
ribs move down and inwards,
diaphragm relax
how do stomas close?
K+ ions actively transported into guard cells, lowering water potential, and water enters by osmosis. guard cells becomes turgid, swells and closes
what is the definition of osmosis?
net movement of water from a higher water potential to a lower water potential through a partially permeable membrane
how do stomas open?
K+ ions actively transport out of guard cells, increasing wp in guard cells, so water osmosise out of guard cells from high wp to low wp
what are lenticels?
pores on bark/stem of tree
what do lenticels do?
allow direct diffusion from air to tissues!
gaseous exchange
prevent water loss
why do small organisms like flatworms not have circulatory systems?
They have large SA:V ratio
what does a good circulatory system contain? 3 things
- an effective pump of fluids
- suitable fluid/medium
- dense network of tubes/vessels
what is an open circulatory system?
where fluids (eg blood) is not contained, flows freely through cavities
what is a closed circulatory system?
have vessels that contain the fluids throughout the body
what organisms have open circulatory systems?
invertebrates
insects, lobsters, crabs
what organisms have closed circulatory systems?
most vertebrates
mammals, fish, birds, reptiles
what are advantages of closed circulatory systems?
fast metabolism, blood transported faster due to higher pressure, further distances
what are disads of closed circulatory systems?
uses a lot of energy
what are advantages of open circulatory systems?
less to transport, less energy needed
what are disads for open circulatory systems?
slow metabolic rate
how does gas exchange take place in leaves?
Gas exchange occurs in plants through tiny pores called stomata, which are found on the leaves. Carbon dioxide enters the plant through the stomata, and oxygen is released.
what are the components of blood?
plasma
erythrocytes
leukocytes
platelets
what is plasma and what does it do?
- transport digested food products, nutrient molecules, excretory products and chemical messages
- help maintain steady body temp by transferring heat
what are erythrocytes and what do they do?
contain haemoglobin
transport oxygen
what are leucocytes and what do they do?
defend body against infections
what is a P wave?
wave from SAN
what is the QRS wave?
w.o.e from AVN -> bundle of His -> apex -> purkinje fibres
(Ventricular systole)
what is the T wave?
ventricles recover, back to normal
what is the QT interval?
contraction time
What is the TP interval?
diastole
What is the name of the heart arrhythmia when HR is higher than normal?
Tachycardia
What is the name of the heart arrhythmia when HR is lower than normal?
Bradycardia
What happens during diastole?
AV valve open
SL valve close
blood trickle down ventricles
what happens during atrial systole?
atrium walls contract ; ventricles relax
AV valves open ; SL valve close
what happens during ventricular systole?
atrial walls relax ; ventricular walls contract
SL valve open, AV valve close
what route does the wave of excitation (w.o.e) take?
SAN (in right atrium) -> atrial walls -> AVN -> delay -> bundle of His in septum -> apex -> purkinje fibres -> ventricular walls
why is there a delay of w.o.e when travelling across chambers?
to make sure all blood are pumped out, so the chambers woulnd’t both be pumping blood simultaneously
what are 4 things needed for clotting to occur?
- clotting factors
- fibrin
- platelets
- erythrocytes & leucocytes
what are the 4 stages of the clotting process?
- nearby platelets activated
- clotting factors reinforce platelets
- fibrin acts like glue
- erythrocytes/leucocytes reinforce clots
how is the clot removed by the body when no longer needed?
dissolves it
what are the stages that lead to atherosclerosis
- arterial endothelium (a.e.) is damaged
- cholesterol deposited onto wall, forming atheroma
- may rupture (a.e.)
- trigger blood clotting process, forming blood clot
- lumen narrow
how are endothelium damaged in terms of atherosclerosis?
from high pressures
why do blood clots in lumen increase blood pressure?
lumen becomes more narrow, loses elasticity in arterial wall so blood pressure increases
and block blood flow
why is it lethal for atherosclerosis to occur?
thrombus(blood clot) increases blood pressure, and block blood flow, affecting oxygen supply to the heart, the heart is unable to pump oxygen to the brain. failure to respire results in death
What is tissue fluid formed from?
Plasma, components of blood that diffused out from hydrostatic pressure
Pass between the cells in most tissues of the body
What is hydrostatic pressure generated from?
Heartbeats
What does not transport out of capillaries?
Erythrocytes and proteins
How is lymph formed?
Some tissue fluids return to capillaries, those that don’t, goes to lymph capillaries
Molecules too large to enter blood capillaries can pass into lymph system
And drains back into blood circulation
Where are lymphocytes produced?
Lymph nodes
The lymph system is a pathway for _____ to be transported from _______ to the ________ following digestion
Lipids
Intestines
Bloodstream
Why is water potential more negative near the venule end than tissue fluid?
Because water diffuses out via osmosis from oncotic pressure
Loss of fluids but same concentration of proteins
what are 2 pathways for water to transport through root hair cells?
- apoplastic
- symplastic
what is the apoplastic pathway?
water travels through cell wall, non-living cells of root hair cells via diffusion
what is the symplastic pathway?
water travels through cytoplasm, living cells of root hair cells via osmosis
why do water molecules often choose apoplastic pathway > symplastic?
faster with less resistance
what does the casparian strip cause
apoplastic pathway joins symplastic pathway as it blocks water
what do xylem tissues transport?
- water
- mineral ions
what factors increases the rate of transpiration? And why?
- ↑temp (increase KE)
- ↑wind (moving air maintains concentration gradient)
- ↑light intensity (stomata open in light)
- ↓humidity (increase concentration gradient)
diffusion
what bond is formed between water molecules for cohesion?
Hydrogen bonds
why are xylems dead, hollow cells with no end walls?
without cytoplasm or nucleus
to reduce resistance for water to move up xylem for cohesion and adhesion
why are xylems lignified?
give structure
waterproofing
strengthen
why do xylems have pits?
holes in water to let water in and out
What is the casparian strip and what is it made up of?
Waterproof block blocking water through the cell wall in apoplastic pathway
Made up of lignin and suberin
How does water move up the stem?
Cohesion and adhesion in xylem
How is water transported in xylem to leaves? 3 marks
- cohesion between water molecules via hydrogen bonds
- adhesion to xylem walls
- from higher to lower wp: lower in leaves bcs water transpired out from leaves/stomata
Is apoplastic pathway diffusion or osmosis?
Diffusion
Bcs no need to travel through partially permeable membranes
Where does translocation occur?
Phloem
What is the source cell
Produce glucose and convert to sucrose , Supply of carbs
What do sink cells do
Store carbs and uses them (eg for growing shoot tip, fruit, seed)
What direction does translocation take place
Bidirectional
What adaptations does phloem have? 4 marks
- sieve tube elements: to transport organic molecules(1), less barriers to transport(1)
- companion cells: large nucleus, many mitochondria to produce ATP (1) for active transport bidirectionally (1) in phloem
Plasmodesmata allows…
Communication and flow of minerals in companion cells
What are plasmodesmatas?
Channel in between cells where cytoplasm joins
Proofs for acidic companion cells/phloem and use of H+ ions in translocation and phloem uses living cells?
- radioactive isotopes
- pH is low in companion cells
- ringing experiments
- Aphid Stylet analysis (cutting off their heads to find sucrose)
- metabolic poisons (using cyanide to kill phloem but xylem still working)
What’s the difference between dead cells and non-living cells?
Dead cells were once living
Non-living never lived
how do small simple organisms respire?
small diffusion distance
large SA:V ratio
low metabolic demands
how do large complex organisms respire?
substances need to travel long distance to reach cells/tissues from external surface
small SA:V ratio
high metabolic rate
specialised gas system required
what is fick’s law?
rate of diffusion is proportional to:
SA x diff in conc / diffusion distance
how do spiracles open and close?
by small sphincters
what are insect exoskeleton made up of?
chitin
Describe the structure of a cell membrane. (3 marks)
phospholipid bilayer - hydrophilic heads and hydrophobic tails
channel proteins and proteins to transport molecules
what are features of ATP?
can move easily across intracellular membranes
used in metabolic reactions
small but sufficient
what are 3 mechanisms used to transport?
- passive transport (diffusion, (facilitated) osmosis)
- endocytosis & exocytosis
- active transport
what could rate of transport across membranes be affected by?
- molecule size
- solubility
- charged particles
facilitated diffusion transports molecules …. the conc gradient
down!
compare carrier vs channel proteins??
ca: both active and passive transport, can move across membrane, can transport both water solu/insoluble substances
ch: only passive, cannot move, only pass water soluble substances
what is endocytosis?
infolding or extension of the plasma membrane to form vesicle or vacuole
is phagocytosis active or passive?
active
requires energy
what is exocytosis?
- release plasma membrane
- release molecules synthesised by the cell
what is endocytosis?
plasma membrane forms a pit and move inwards
what are channel proteins for water called?
aquaporins
what does hypertonic mean? what would happen to animal cells?
concentrated solution
so animal cells lose water molecules, becomes crenated
what does hypotonic mean? what happens to animal cells when placed in it?
pure water solution
cell gains water, membrane bursts aka haemolysis bcs no cell wall
what is water potential and what is the unit?
measure of tendency for water to pass into or out of cell
kPa
what is the water potential equation for plant cells?
water potential = turgor pressure + osmotic potential
what is turgor pressure?
pressure inside plant cells caused by water entering the cell
what is osmotic potential?
water potential of solution caused by solutes dissolved in it
(ALWAYS NEGATIVE)
what is the unit for partial pressure of oxygen and what does it mean?
kPa
concentration of oxygen basically
what is Hb short for?
haemoglobin
Hb + 4O2 <->
HbO8
when does Hb become saturated?
at high partial pressure (pp) of oxygen, and low pp of CO2
when does Hb dissociate with oxygen?
at low pp of O2, high pp of CO2
what is the relationship between partial pressure (pp) of O2 and % saturation of Hb?
oxygen dissociation curve
sigmoid curve
what is the explanation for Hb’s sigmoid curve?
Hb finds it difficult to bind to the first O2 molecule.
When it does bind, it changes the tertiary structure of Hb (via cooperative binding), making it easier for O2 molecules to bind to
Due to conformational change
why does Hb’s tertiary structure change after binding to the first O2?
cooperative binding
what do curves on the left of the normal sigmoid curve mean?
Hb has higher affinity for O2,
what does affinity in terms of Hb mean?
becoming saturated with O2 at lower pp of O2
(higher affinity = gives up oxygen less readily)
what are 2 exemplar organisms that have S-curves to the left?
llama (live in higher altitude, pp of O2 lower)
lugworms (in waterlogged burrows, pp of O2 lower in air than water)
what are 2 exemplar organisms that have S-curves to the right?
mice
birds
why do mice’s Hb have lower affinity for O2?
small, so high SA:V ratio
high metabolic rate
lose lots of energy as heat
so more O2 is supplied to cells for more aerobic respiration to compensate for heat loss
why do birds’ Hb have lower affinity for O2?
they fly, so use up lots of energy for muscle contraction
Hb has lower affinity by giving up O2 at higher pp of O2 to supply O2 to muslces
what are myoglobins?
oxygen store in muscles
where are myoglobin curves found relative to normal adult Hb? Why?
Left
only gives up O2 at v low pp of O2, eg during vigorous exercise
where is the foetal Hb curve found relative to the adult (maternal) Hb? Why?
Left
greater affinity for O2, becomes saturated w O2 at lower pps of O2
- allow foetus to take O2 from mother’s blood in placenta where pp of O2 is low
what is the Bohr effect?
the greater the CO2 conc, the greater shift to right (low pH changes quaternary structure of Hb)
In terms of oxidation dissociation curves:
there is a ____ correlation between high temperatures and low pHs and shift to the ____. Because it reduces _______
positive
right
rate of respiration for O2 dissociation
what is the sequence of events for blood clotting?
- platelets form a plug and release clotting factors, including thromboplastin
- prothrombin → thrombin
- which activates fibrinogen→fibrin
what are neutrophils?
leucocyte to fight infection
Phagocytosis by digesting pathogens
what are eosinophils?
leucocyte in the immune system that fights against pathogens, such as parasites and bacteria
what are monocytes?
type of leucocyte: inflammatory and anti-inflammatory processes that take place during an immune response
why is bipolar lipids suitable molecules to form cell membrane? 2 marks
- hydrophilic layer interacts with aqueous environment
- hydrophobic barrier inside
how are mineral ions taken up by active transport? (3 marks)
- using ATP
- against conc. gradient
- using carrier proteins across membrane
describe structure of phospholipid (2 marks)
glycerol head
2 fatty acid tails
bonded via ester bonds
what is the description of exocytosis?
form of active transport where large particles move out of cells
how is tissue fluids formed?
hydrostatic pressure forcing fluids out of capillaries
how is tissue fluids returned to capillaries? (3 marks)
oncotic pressure > hydrostatic pressure
generated by proteins that are too large to pass out of capillary
more proteins in plasma than tissue fluids
why is there more proteins in plasma than tissue fluids?
proteins are too large to pass out of capillaries to tissue fluids
compare and contrast the transport of fluids in veins vs lymph vessels (2 marks)
both have valves
both are low pressure
faster in vein
heart causes mass flow in vein
why is production of tissue fluids essential in the human body? (2 marks)
- supply O2
- remove CO2/urea
- so respiration can take place
what happens to tissue fluids that aren’t reabsorbed into the blood capillary? (2 marks)
- enters lymphatic system
- lymph returns to veins/blood
what are hydrostatic and oncotic pressures generated by? respectively
heart pumping/contraction
(plasma) proteins
how does blockage of lymphatic duct lead to lymphoedema? (2 marks)
- proteins accumulate in tissue fluid / less protein in blood plasma
- lowering oncotic pressure
- less fluids removed by blood capillary/more fluids drawn out of blood
how is tissue fluid formed by the capillary? (3 marks)
- when hydrstatic pressure > oncotic pressure (???)
- leaves capillaries through pores
- plasma proteins are too large to leave capillary
- more plasma proteins in plasma than tissue fluid
Why is it difficult to determine osmotic potential than water potential of plant cells? 2 marks
- can only be measured by incipient plasmolysis
- cannot measure directly
Why is it difficult to determine osmotic potential than water potential of plant cells? 2 marks
- can only be measured by incipient plasmolysis
- cannot measure directly
What is myogenic and where is it found?
Impulse originating on its own, not nerve impulse
In the heart initiating SAN pacemaker w.o.e.
What are the 3 features of alveoli to increase efficiency of diffusion in lungs?
- moist surface, allow gases to dissolve
- one cell thick, thin membrane
- high SA:V ratio
- maintains steep conc gradient
Why does mucus in bronchi and bronchioles for cystic fibrosis patients affect them? 2 marks
Airways are blocked
So less gaseous exchange since less oxygen to alveoli
What are the 2 active enzymes involved in blood clotting process?
Thrombin and thromboplastin
Why does rate of calcium ion uptake in pancreatic cells increase and level off as calcium ion concentration increases? (2 marks)
- Rate of diffusion increases due to increased concentration gradient
- rate levels off since transport proteins limit rate
- bcs calcium ions enter by facilitated diffusion
What is the net movement of gaseous exchange in roots of a plant?
Only ‘in’ of oxygen
Only ‘out’ of carbon dioxide
Describe how the events of the cardiac cycle change when the demand of body cells for oxygen increases. (2 marks)
- cardiac cycle happens more frequently
- ventricles contract more forcefully
How does translocation in plants take place?
- assimilates in phloem transport substances
- sucrose transported from source to sink
- bidirectionally
how does sucrose get transported in the phloem?
- from source
- into companion cells via active transport
- into sieve tubes
What is the mechanism of translocation from source to sink?
Mass flow hypothesis
Describe the mass flow hypothesis of translocation from source to sink. (4 marks)
- sugars loaded in phloem (/sieve tubes)
- lowering wp so water enters
- increases pressure
- sugars converted into starch, lowering wp in cell
- water moves out of cell
what happens in sink cells?
use sucrose in respiration or converted to starch for storage
How are companion cells adapted?
- lots of mitochondria -> ATP for active transport of sucrose into sieve tubes
How are sieve tube elements adapted?
- stacked on top of each other, allow uninterrupted flow of sucrose
- sieve pores allow solutes flow through phloem
- no nucleus, little cytoplasm and organelles - no obstruction of flow
- fewer sieve plates from elongation, less resistance
- many plasmodesmata, allow flow
what are strengths of the mass flow hypothesis of translocation?
- explains why contents of phloem are under pressure
- explains conc gradient between source and sink
Weaknesses of the mass flow hypothesis in translocation?
does not explain
- bidirectional movement
- why assimilates travel at different rates
what are adaptations of root hair cells?
- stick out, increase SA
- lots of mitochondria, release ATP for active transport
- lots of ribosomes to make carrier proteins
- thin cell walls, decrease diffusion distance
compare the apoplastic and symplastic pathways.
- non living / living
- via cell walls / cytoplasm and plasmodesmata
- diffusion / osmosis
- faster / slower
- blocked by Casparian strip / not
does water usually travel via apoplastic or symplastic pathway?
apoplastic
- faster
- due to less resistance to flow
Draw + Label a transverse diagram of a stem
(Check photo!)
Adaptation of xylems (5 total, give 3 at least)
- no end walls, ensure continuous flow of water
- dead cells so little resistance to water flow
- lignified walls, give strength and prevent water leak
- diff lignin patterns allow stretch
- pits in walls allow lateral movement of water
What is the evidence for cohesion tension theory?
- lignin walls can withstand tension
- diameter of trees reduced in daytime (due to tension pulling xylem vessels inwards)
What is the perfect definition for transpiration?
Diffusion of evaporated water vapour from aerial parts of plant through stomata
Why is transpiration important?
- brings water to leaves for p/s
- cools leaves
- pulling water up keeps plant cell turgid and upright
- make nitrates and chlorophyll as water contains mineral ions
What are similarities between xylem and phloem?
Both
- contain vertical arrangement of cells to form tubes
- have cellulose cell walls
- contain parenchyma cells
What are structural differences between xylem and phloem?
X / P
- has lignified walls / does not
- no end walls / have sieve plates
- none / has companion cells
- none / has cytoplasm and organelles
- has pits in walls / doesn’t
What are general non-structural differences between xylem and phloem?
X / P
- dead / living
- one direction / bidirectional
- transports water + mineral ions / organic molecules
- down water gradient / pressure gradient
What are 2 types of photometers to measure rate of transpiration?
- bubble photometer
- mass photometer
What does a photometer do?
Measure rate of water uptake
How is transpiration possible?
From cohesion tension effect
Uptake of water is dependent on rate of transpiration!
What is the mammalian advantage to have the HB dissociation curve towards the right? (3 marks)
As respiring cells are releasing O2
So Hb has lower affinity for O2
It dissociates at higher pp of O2
So more O2 released for aerobic respiration
Explain why it is more difficult to determine the osmotic potential than the water potential in plant cells. (2 marks)
-Cannot measure osmotic potential directly as water potential of cell contains both op and turgid pressure (tp)
-can only measure by incipient plasmolyses
- when wp=op, tp=0
Blood taken from a patient had an unusually high proportion of eosinophils.
Explain why this patient had an unusually high proportion of eosinophils. (2 marks)
Has an allergy
Excess production of eosinophils
Or parasitic infection
Describe the techniques microbiologists could use to confirm this food poisoning was caused by Staphylococcus. (4 marks)
- isolate bacteria from food / patients
- streak plate
- look at characterises of colonies
- onto selective media
- use gram stain to distinguish between Gram+ or Gram-
- use antibodies
Explain why heart cells are damaged as a result of heart disease. (2 marks)
Atheroma blocks arteries
So heart cells have less oxygen
To respire
Explain the role of air sacs in locusts. (2 marks)
- Store of oxygen
- to allow respiration for large active locusts
Explain why single cell organelles don’t have gas exchange system. (2 marks)
- have high SA:V ratio
- so diffusion is sufficient
Explain how changes in fibrinogen concentration might be a risk factor for CVD. (3 marks)
- increased conc of fibrinogen leads to increased fibrin
- increase risk of blood clotting
- blocking lumen of arteries
Explain how plants in dry climates ensures water potential is high. (3 marks)
- traps water vapour
- with hairs
- so less evaporation/transpiration
Explain how gills are adapted for gas exchange. (3marks)
- gill filaments to increase surface area for diffusion
- counter currently flow to maintain conc grad
- thin membrane to reduce diffusion distance
Explain how the structure of haemoglobin enables it to combine with oxygen in the blood vessels of the lungs. (3 marks)
- has 4 haem groups, so can pick up 4 molecules of O2
- can bind to oxygen molecules reversibly
- 3D shape of haem groups changes after first oxygen binds - cooperative binding
Explain how atherosclerosis can cause coronary heart disease and can lead to death. (4 marks)
- atheroma forms in coronary artery
- cause blockage of coronary artery
- reduce oxygen supply to heart
- heart muscles die, stop contracting
- oxygen not supplied to brain cells and die
Suggest 2 advantages of injecting the protein into a vein rather than an artery. (2 marks)
- larger lumen, thinner wall - so easier penetration
- easier to find as closer to the surface
- lower blood pressure so less damage done
