Module 3 - Exchange and Transport Flashcards
Why do fish and insects have specialised gas exchange system?
Multicellular, small SA:volume ratio, large diffusion distance
Can’t perform gas exchange via surface so they have gills and tracheal system
Structure of gills
Many gill filaments and lamellae = large SA
Gill lamellae have thin wall and are permeable
Countercurrent flow - water and blood pass over opposite directions, blood always passes water with high 02 concentration, maintains favourable conc gradient all across gradient
Structure of tracheal system
Spiracles, have valves to prevent water loss
Spiracles connect to trachea connect to tracheoles connect directly to respiring cells/ muscle fibres
How does gas exchange occur in tracheal system?
Rest = down concentration gradient, simple diffusion of 02 and c02, tracheal fluid containing 02 seeps in Active = ventilation, mass flow of 02 and c02, tracheal fluid containing 02 is sucked in
Function of lungs?
Site of gas exchange in mammals
What are lungs made up of?
Trachea, bronchi, bronchioles, alveoli
Structure of trachea/bronchi?
Strong c-shaped cartilage, c-shape gives flexibility
Goblet cells - make mucus, traps pathogens
Epithelial cells - have cilia, pushes mucus out of the lungs
They are the lining
Structure of bronchioles
Wall made of smooth muscle
Smooth muscle contracts, lumen smaller, bronchioles constrict, occurs near dangerous gases, reduces intake
Lining made of goblet cells and ciliated epithilial cells
Adaptation of alveoli
Many folded tiny alveoli so large SA
Thin wall so short diffusion distance
Elastic tissue so stretches increasing SA when breathing in, recoils when breathing out
Ventilation maintains concentration gradient
Adaptation of capillaries
Many tiny capillaries so large SA
One cell thick thin wall so large diffusion distance
Narrow lumen low diffusion distance
Circulation maintains concentration gradient
How 02 moves from alveoli to capillaries
Simple diffusion
How c02 moves from capillaries to alveoli
Simple diffusion
Process of breathing/ventilation
Inhalation - external intercostals contract, rib cage moves up and out, diaphragm contracts , increase thoracic cavity/ volume DECREASING pressure
Pulmonary ventilation
PV = tidal volume x breathing rate
Blood vessels of heart
Vena Cava supplies R atrium with deox blood from body
Pulmonary vein supplies L atrium with oxy blood from heart
R ventricle supplies pulmonary artery with deox blood
L ventricle supplies aorta with oxy blood
Job of valves
Ensure one way flow Atria - ventricles - arteries 2 valves - AV valves, semi-lunar valves AV valves - between atria and ventricles SL valve - between ventricles and arteries
When are AV open ore closed
Open = pressure in atria bigger than ventricles Closed = pressure in ventricles greater than atria
When are SL open or closed
Open = pressure in ventricles bigger than arteries Closed = pressure in arteries bigger than ventricles
Process of cardiac cycle
All relaxed, AV valve open SL valve closed
SA node causes atria to contract with an impulse
Sent too AV node allowing ventricles to fill with blood
Impulse travels through bundle of his and into ventricle walls through purkinje fibres causing contraction of ventricles, av valves close, sl valves open
ventricles relax, sl close, av open
Formula for cardiac output
CO = stroke volume x heart rate
CHD and myocardial infarction
High pressure damages lining of coronary artery
cholesterol build up beneath lining
breaks through lining forming atheromatous plaque
blood clot forms
blocks coronary artery
less blood flow
Risk factors of CHD
Age, gender, ethnicity
saturated fats, salts, smoking, obesity
Atheroma and aneurysm
Atheroma weakens wall of artery, blood builds up in the wall, the wall swells then bursts = aneurysm
Structure of arteries/arterioles
Narrow lumen
Thick wall
Elastic tissue - withstand pressure, recoils to maintain pressure and smooth out
Smooth muscle for vasodilation/constriction
Collagen prevents tearing
Structure of veins/venules
Wide lumen for good blood flow
Thin wall, can be squished by muscles to increase venous return
Valves prevent back flow
Adaptations of capillaries
Many small capillaries, large sa
Thin wall, short diffusion distance
Pores between cells, allows fluid to move in and out
Narrow lumen, increase diffusion time but decrease diffusion distance
How does exchange occur between capillaries and all cells
By mass flow
Fluid moves out of blood in capillaries carrying the nutrients
Fluid moves back in the blood capillaries carrying the waste
How is tissue fluid formed and returned to circulatory system
At arterial end there is a build up of hydrostatic pressure
Pushes fluid out of capillaries via pores
Fluid carries nutrients
Fluid surrounds the cells
At venous end fluid moves back in by osmosis
Capillary has low water potential due to protein presence, too large to move out
Any excess tissue fluid is picked up by lymph system and returned to vena cava
Why does high blood pressure cause tissue fluid accumulation
Increased hydrostatic pressure, more tissue fluid forced out
Why does diet low in protein cause accumulation of tissue fluid
The water potential in capillary is not as low as normal, not as much fluid can move back in vias osmosis
Structure of haemoglobin
Globular protein - soluble and specific Quaternary Each chain has a haem group Each haem has Fe2+ Each Fe2+ carries and 02 Each haemoglobin carries 4 lots of 02
What is affinity
The level of attraction haemoglobin has to 02
Role of haemoglobin in 02 transport
Haem has high affinity in lungs, high pp of 02 and low pp of c02 in lungs and becomes saturated
Haem is transported in rbc in the blood
Haem has low affinity in respiring tissues, low pp of 02 and high pp of c02 in respiring tissues so 02 is unloaded, haem becomes unsaturated
Relationship between 02 partial pressure and affinity/saturation of haemoglobin
Positive correlation
As 02 partial pressure increases, affinity/saturation of haemoglobin increases
The correlation is not linear but is curved, 02 dissociation curve/ODC
Middle portion of ODC has a steep gradient, when respiring tissues change from resting to active and pp02 falls, so large drop in affinity, more 02 delivered to respiring tissues
Relationship between co2 pp and affinity/saturation of haemoglobin (BOHR SHIFT)
Negative correlation
As co2 pp increases, affinity/ saturation of haem decreases
The co2 lowers the pH of the blood, changes the shape of haem so 02 is released, lowers affinity, shifts ODC to the RIGHT, called the bohr shift
Benefit = more o2 delivered to respiring cells
How does foetus receive o2
o2 dissociates from mothers haem to foetul haem, foetul haem has higerh affinity
Benefit of foetul haem having high affinity
ODC will be to the left, o2 dissociates from mothers haem to foetul haem at low pp02 in the placenta
Why do adults not keep with foetul haemoglobin
High affinity will mean less o2 will be unloaded at the respiring tissues
Affinity of organism in low o2 environment
Has a high affinity, curve to left, can readily associate o2 at low o2 partial pressures
Affinity of active organism
Has a low affinity, curve to right, so more o2 can be unloaded to meet cells demands for more respiration
Affinity of small organisms
Large sa:volume ratio, lose lots of heat, needs to respire for heat, low affinity, curve to right, unloads enough o2 for cells demands of more respiration
Job of roots
Absorb water and minerals
water by osmosis, minerals by active transport
Function of xylem
Transport water and minerals up the plant to leaves
Xylem structure
Long hollow tube
Narrow lumen
Wall made of lignin so strong, water proof and adhesive
wall contains pores
How does water move up xylem
Transpiration/ loss of water at leaves
Osmosis of water from top of xylem into leaf (transpirational pull)
Applies TENSION to water in xylem
Water particles stick together pulling each other up COHESION
-Cohesion-tension theory
Supported by:
-capillary action - water automatically moves up lumen
-adhesion - water particles stick to lignin
-root pressure - water absorbed at roots pushes water up by hydrostatic pressure
Why does tree diameter decrease during day
More light and temp Higher rate of transpiration Higher transpirational pull Water pulled via cohesion-tension Water adheres to lignin, pulls xylem walls inwards
Leaf structure
Upper layer called UPPER EPIDERMIS
Waxy cuticle on upper epidermis, acts as barrier reducing water loss
Beneath UPPER EPIDERMIS there are PALISADE CELLS
PALISADE CELLS allow photosynthesis
Beneath PALISADE CELLS are SPONGY MESOPHYLL CELLS
MESOPYLL CELLS are loosely packed allowing gas exchange
Lower layer called LOWER EPIDERMIS
Adaptation of palisade cells
Located near top of leaf, close to light
Large SA for light
Thin cell wall so short diffusion pathway
Contains many chloroplasts
Large vacuole, pushes chloroplasts closer to edge and therefore light
Chloroplast structure
Organelle for photosynthesis Has double membrane Contains thylakoid discs Thylakoids contain chlorophyll Thylakoids stacks called granum Thylakoids surrounded by stroma
Gas exchange in leaves
Lower epidermis has guard cells When turgid guard cells open forming a stomata Gas exchange occurs through stroma Day - C02 IN 02 OUT Night - 02 IN C02 OUT
What is transpiration
Loss of water vapour via stomata
How does transpiration occur
Moist lining of spongy mesophyll evaporates forming vapour
Builds up in air spaces
If conc of water vapour is high enough and stomata is open, diffuses out
Factors that increase rate of transpiration
Light - more light, more stomata open, higher SA for diffusion
Temp - more evaporation, higher vapour conc and kinetic energy
Wind - more wind, maitains conc gradient
Humidity -less humidity, less vapour outside, conc gradient
What is a potometer
Measures rate of transpiration
Principle of potometer
As transpiration occurs, plant pulls up more water from potometer by cohesion-tension, causes bubble to move towards plant
More water lost by transpiration, more water taken up, further the bubble moves
Measuring rate of transpiration
Rate of transpiration = volume of transpiration/time
Volume of transpiration = distance bubble moved x csa of tube (πr2)
How to set up potometer
Healthy leaf and shoot
Cut shoot underwater and connect to potometer (prevents air bubbles from blocking xylem)
Ensure potometer is tight
What does potometer actually measure
Rate of water uptake as a result of water loss
What is a xerophyte
Plant adapted to reduce water loss
Xerophyte adaptations
Needle like leaves - reduce SA
Thick waxy cuticle - impermeable barrier, waterproof
Dense spongy mesophyll, less air spaces for vapour build up
Sunken stomata, hairy leaves, rolled up leaves, traps moist layer of air, reduce conc gradient
Function of phloem
Transport organic material
Phloem structure
Sieve tube with companion cells
Translocation
Mass flow of water carries sucrose
H+ actively transported out of companion cell into cell wall
Sucrose diffuses (facilitated) from source to companion cell
Co-transport of sucrose (against conc) and H+ (with conc)
Lowers wp in phloem, osmosis from xylem, increases hydrostat pressure
Forces sucrose to sink down pressure gradient
Sucrose into sink via active transport, lowers wp of sink
Osmosis of water into sink, some returns to xylem
Lowers pressure
