Exchange Flashcards
How do microorganisms obtain nutrients and remove waste
- nutrients (glucose,oxygen) move in by diffusion via their surface
- waste (CO2) moves out by diffusion via their surface
Why are microorganisms able to perform exchange via their surface
- have a large SA to volume ratio
- short diffusion distance
- have low demand
Why can’t plants/animals perform exchange via their surface
- have a small SA to volume ratio
- large diffusion distance
- require specialised systems
Why do fish have specialised gas exchange systems
- they have a small SA to volume ratio
- large diffusion distance
- so can’t perform gas exchange via their surface, require specialised system called gills
What is gas exchange
oxygen in, carbon dioxide out
Structure of gills in fish
- many gill filaments and lamellae; increase surface area
- lamellae have thin walls so have a short diffusion distance
What does ventilation do in fish
brings in pure water, high oxygen low carbon dioxide
What does circulation do in fish
brings in deoxygenated blood, low oxygen high carbon dioxide
What is the counter-current flow
water and blood pass over in opposite directions, maintaining the concentration gradient along the lamellae
Why do insects have specialised gas exchange systems
- small SA to volume ratio
- large diffusion distance
- so can’t perform gas exchange via their surface, require specialised system called tracheal system
Structure of tracheal system in insects
- starts with openings on body surface called spiracles; spiracles contain valves, if open, gas exchange, if closed, preventing water loss
- spiracles connect to trachea
- trachea connect to tracheoles
- tracheoles connect directly to respiring cells
How does gas exchange occur in tracheal system of insects
- at rest, down a concentration gradient, oxygen moves in, co2 moves out via simple diffusion
- when active, by ventilation, air inhaled for mass flow of oxygen, air exhaled for mass flow of co2
Function of the lungs
site of gas exchange in mammals
Components of the lungs
- trachea
- bronchi
- bronchioles
- alveoli
Function of trachea, bronchi and bronchioles
transport of air and filter (bronchioles also control how much air reaches alveoli)
Adaptation of alveoli
- million of folded microvilli (large surface area)
- one cell thick (short diffusion distance)
- ventilation maintains concentration gradient
Adaptation of capillaries
- one cell thick (short diffusion distance)
- narrow lumen (increases diffusion time, decreases diffusion distance)
- cirvulation maintains concentration gradient
How does oxygen move from alveoli to capillaries
by simple diffusion passing through alveolar epithelium and capillary epithelium
How does CO2 move from capillaries to alveoli
by simple diffusion passing through capillary epithelium and alveolar epithelium
Describe the process of breathing in/inhalation
- external intercostal muscles contract, rib cage moves up and out
- diaphragm contracts (flattens)
- increase in volume, decrease in pressure
- air moves in
Describe the process of breathing out/exhalation
- external intercostal muscles relax, rib cage moves down and in
- diaphragm relaxes
- decrease in volume, increase in pressure
- air moves out
What is pulmonary ventilation
volume of air breathed in/out per minute
Formula for pulmonary ventilation
PV = tidal volume (volume of air breathed in/out in one breath) x ventilation rate (number of breaths per minute)
Function of intestines
site of exchange of digested nutrients in mammals
What is digestion
breakdown of large insoluble molecules into small soluble molecules (so they can move into the blood then into body cells)
How are lipids broken down
by lipase into monoglycerides and 2 fatty acids (small intestine)
How are proteins broken down
by endopeptidase/exopeptidase/dipeptidase into amino acids
endo= in stomach
exo= in small intestine
di= on lining of SI
How is starch/glycogen broken down
by amylase into glucose; if on lining of small intestine, maltase/lactase/sucrase are used
Where can amylase be found
- salivary glands
- pancreas
Where can maltase/lactase/sucrase be found
lining of small intestine
What does the small intestine absorb
small soluble nutrients (glucose, amino acids, monoglyceride and fatty acids, vitamins and minerals)
What does the large intestine absorb
water
Why do humans need a specialised transport system
- multicellular organisms so have a large diffusion distance and high demand
- need a transport system to deliver nutrients and remove waste from all cells
Name the human transport system
circulatory system
Components of the circulatory system + roles
- heart (pumps blood)
- blood vessels (carry blood)
- blood (carries nutrients/waste)
Why it called the double circulatory system in humans
the heart pumps twice, transporting oxygenated and deoxygenated blood; generates enough pressure to supply all body cells
Why is it called a closed system in humans
blood is transported in blood vessels, helps to maintain pressure and redirect blood flow
Layout of circulatory system
artery, arterioles, capillaries, venules, veins
Role of artery/arterioles
carry oxygenated blood away from the heart
Role of capillaries
site of exchange
Role of veins/venules
return deoxygenated blood to the heart
Components of the heart
- left and right atriums
- left and right ventricles
- atria pump blood to ventricles
- ventricles pump blood out of the heart
Ventricles vs atria
ventricles are thicker since they have to pump blood further
Left vs right ventricle
left ventricle thicker as it pumps blood to the whole body
Name 4 blood vessels in the heart + roles
- vena cava (supplies R atrium with deoxygenated blood from body)
- pulmonary vein (supplies L atrium oxygenated blood from lungs)
- pulmonary artery (supplies deoxygenated blood to lungs to become oxygenated)
- aorta (supplies oxygenated blood to body)
Role of valves
ensure one way flow of blood, prevents backflow
Name the 2 types of valves in the heart
- AV valve, between atria and ventricles
- SL valve, between ventricles and arteries
When are AV valves open or closed
- open, pressure in atria greater than pressure in ventricles
- closed, pressure in ventricles is greater than pressure in atria
When are SL valves open or closed
- open, pressure in ventricles greater than pressure in arteries
- closed, pressure in arteries greater than pressure in ventricles
Describe the cardiac cycle
Cardiac diastole:
- atria relaxed, ventricles relaxed
- AV valve open, SL valve closed
Atrial systole:
- atria contract whilst ventricles relax
- decreases volume inside atria which increases pressure
- increased pressure forced AV valves to open and pushes blood into the ventricles
Ventricular systole:
- ventricles contract whilst atria relax
- decreases volume inside ventricles which increases pressure
- pressure is now higher in ventricles so AV valves close and SL valve opens
- closure of AV valve is important to prevent backflow of blood into atria
- blood is forced out of ventricles into arteries
Diastole:
- atria and ventricles relaxed
- AV valve opens, SL valve closes
- filling starts again
What causes the heart sounds
when the valves close, 1st is the AV valve, 2nd is the SL valve
Formula for cardiac output
CO = stroke volume x heart rate
What is stroke volume
volume of blood pumped out of heart in one beat
What is heart rate
number of beats per minute
What is cardiac output
volume of blood pumped out of the heart per minute
Describe how CHD occurs
- high blood pressure damages lining of coronary artery
- cholesterol builds up beneath lining, in the wall
- this causes turbulent blood flow
- a blood clot forms
- this blocks the coronary artery
- so less blood flow to the heart muscle
- so less glucose and oxygen delivered
- the heart muscle can’t respire so it dies (myocardial infarction)
Risk factors of CHD
- obesity
- smoking
- lack of exercise
- age, gender, ethnicity
- saturated fats
Exception for the role of an artery
pulmonary artery carries deoxygenated blood to lungs
Exception for the role of a vein
pulmonary vein carries oxygenated blood to the heart
Structure of artery/arterioles
- narrow lumen, maintains pressure
- thick wall, withstands high pressure
- elastic tissue in wall, allows for expansion and contraction when necessary to withstand pressure
- collagen in walls, prevents artery from tearing
Structure of veins
- wide lumen, ease off blood flow
- thin wall
- valves in lumen, prevents backflow of blood
Structure of capillaries
- one cell thick, short diffusion distance
- pores between cells, allows fluid to move in and out
- narrow lumen, increases diffusion time, decreases diffusion distance
- many small capillaries, increase SA
Contents of blood
- plasma; carries cells and solutes
- cells; red and white blood cells, platelets
- solutes; nutrients, waste, protein
How does exchange occur between capillaries and all cells
- by mass flow
- fluid moves out of blood in the capillaries carrying nutrients
- fluid moves back into blood in the capillaries carrying waste
What is the fluid surrounding our cells called
tissue fluid
How is tissue fluid formed and returned to the circulatory system
- at the start of the capillary (arterial end) , build up of hydrostatic pressure
- this pushes fluid out of the capillary via the pores
- the fluid carries nutrients with it
- the fluid surrounds the cells (tissue fluid)
- at the end of the capillary (venous end), fluid moves back in by osmosis
- capillary has low water potential due to presence of proteins
- any excess tissue fluid is picked up by the lymph system and deposited in the vena cava
Why does high blood pressure cause accumulation of tissue fluid
increases hydrostatic pressure, so more tissue fluid is formed
Why does diet low in protein cause accumulation of tissue fluid
water potential in the capillary isn’t as low as normal, so not as much fluid can move back into capillary by osmosis
Role of red blood cells
carries haemoglobin, haemoglobin carries oxygen to cells
Structure of haemoglobin
- globular protein (soluble and specific 3D shape)
- quaternary structure made of 4 polypeptide chains
- each chain carries haem group
- each haem group carries Fe2+
- each Fe2+ carries an O2
- so each haemoglobin carries 4 lots of O2
Role of haemoglobin
load oxygen into lungs and deliver to respiring tissues
What is affinity
the level of attraction haemoglobin has to oxygen
high affinity = strong attraction
low affinity = weak attraction
Role of haemoglobin in oxygen transport
- haemoglobin has high affinity in the lungs due to high partial pressure of oxygen and low partial pressure of carbon dioxide
- so haemoglobin loads oxygen in the lungs and becomes saturated
- haemoglobin is transported in blood in red blood cell
- at respiring tissues, haemoglobin has low affinity due to low partial pressure of oxygen and high partial pressure of carbon dioxide
- so oxygen is unloaded and haemoglobin is therefore unsaturated
Relationship between oxygen partial pressure and affinity of haemoglobin
- positive correlation, as oxygen partial pressure increases, affinity of haemoglobin increases
- correlation is curved not linear
Relationship between carbon dioxide partial pressure and haemoglobin affinity
- negative correlation, as carbon dioxide partial pressure increases, affinity of haemoglobin decreases
- CO2 lowers pH of blood, causes haemoglobin to change shape, lowering its affinity
How does a fetus receive oxygen
- from mother’s blood, oxygen dissociates from mother’s haemoglobin and associates with fetal haemoglobin in placenta
- fetal haemoglobin has higher affinity than mother’s haemoglobin
Benefit of fetal haemoglobin having high affinity
fetal haemoglobin’s ODC will be to the left, high affinity
Why do adults not keep with fetal haemoglobin
the high affinity will mean less oxygen will be unloaded at respiring tissues
Affinity of organisms in a low oxygen environment
- high affinity, curve to the left
- so can readily associate at low oxygen partial pressures
Affinity of active organisms
- low affinity, curve to the right
- so more oxygen can be unloaded to meet cell’s demand for more respiration
Affinity of small organisms
- large SA to volume ratio, lose alot of heat, needs to respire to generate heat
- low affinity, curve to the right, so unloads enough oxygen for cells which demand more oxygen
Name the exchange systems in plants
- leaf, to absorb light and CO2 for photosynthesis
- roots, to absorb water and minerals
Name the transport systems in plants
- xylem, transports water and minerals in one direction from roots to leaves
- phloem, transports glucose/sugars in both directions
Role of the roots
- absorb water and minerals
- absorb water by osmosis
- absorb minerals by active transport
What do plants need
- water, for photosynthesis, cytoplasm hydration, turgidity of cells
- magnesium, nitrate and phosphate, mg to make chlorophyll, nitrate to make amino acids, phosphate to make ATP
Role of the xylem
transport water and minerals from roots, up the plant, to the leaves
Structure of xylem
- long continuous hollow tube (no resistance to water flow)
- narrow lumen
- wall made of lignin, lignin is strong, waterproof and adhesive
- wall contains pores so water and minerals can leave
How does water move up the xylem
- loss of water at the leaves (transpiration)
- water moves from the xylem to the leaf by osmosis (transpiration pull)
- this applies tension to the column of water in the xylem
- the column of water moves up as one as the water particles stick together; cohesion tension theory
- it’s supported by capillary action, adhesion and root pressure
Why does the diameter of a tree decrease during the day
- more light and higher temperature
- increases rate of transpiration
- increases transpiration pull
- water pulled up xylem by cohesion tension as the water particles stick to the wall of the xylem
Structure of leaves
- upper layer called upper epidermis
- waxy cuticle on upper epidermis (barrier to reduce water loss)
- beneath upper epidermis are palisade cells
- palisade cells are where photosynthesis takes place
- beneath palisade cells are spongy mesophyll cells which are loosely packed leaving air spaces to allow for gas exchange
- lower layer called lower epidermis
Adaptations of palisade cells for photosynthesis
- located near top of leaf, closer to sunlight
- large size, large surface area for sunlight
- thin cell wall, short diffusion distance for CO2
- contains many chloroplasts, site of photosynthesis
- large vacuole, pushes chloroplast to edge of cell closer to light
Structure of chloroplast
- double membrane
- contains thylakoids
- thylakoids contain chlorophyll
- stack of thylakoids called granum
- thylakoids surrounded by fluid called stroma
How does exchange occur in leaves
- lower epidermis of plant contains guard cells
- when turgid, guard cells form opening called stomata
- gas exchange occurs via stomata
What exchange occurs in leaves during the day
- plant photosynthesises and respires
- CO2 moves in for photosynthesis
- Oxygen moves out
What exchange occurs in leaves at night
- plant only respires
- oxygen moves in for respiration
- CO2 moves out
What is transpiration
loss of water vapour from the leaf via the stomata
How does transpiration occur
- moist lining of spongy mesophyll cells evaporate forming water vapour
- water vapour builds up in air spaces
- if water vapour concentration is high enough and stomata is open, water vapour diffuses out
Factors that increase rate of transpiration
- sunlight; more sunlight means more stomata open, increases SA for transpiration
- temp; higher temp means more evaporation
- wind; more wind maintains concentration gradient
- humidity; less humidity means less water vapour in surrounding air, increase in water vapour
What is a potometer
apparatus used to measure rate of transpiration
How does a potometer work
as transpiration occurs from the leaves, plant will pull up more water from the potometer by cohesion-tension causing the bubble to move towards plant
How to measure rate of transpiration
rate of transpiration = volume of transpiration/time
How to set up a potometer
- choose healthy leaf and shoot
- cut shoot underwater and connect to potometer underwater
- ensure potometer is air and water tight
What does a potometer measure
rate of water uptake as a result of water loss from a plant
What is a xerophyte
a plant adapted to reduce water loss (reduce transpiration)
Adaptations of xerophyte
- spiky leaves, reduced surface area
- thick, waxy cuticle, waterproof, impermeable barrier
- densely packed spongy mesophyll, less air spaces, less water vapour build up
- hairy leaves, traps moist layer of air, reduces concentration gradient
Function of phloem
transport organic materials like sugars and minerals
Structure of phloem
made of 2 parts, sieve tube with companion cells alongside)
Role of sieve tube in phloem
transports organic substances
Role of companion cells in phloem
help with ATP production
How does the phloem transport organic material like sucrose
- by mass flow
- sucrose loaded into phloem at source
- H+ ions actively transported from companion cells into source
- so H+ ions diffuse back into companion cells from source
- they also pull in sucrose with them by co-transport
- sucrose then diffuses into sieve tube
- this lowers water potential of sieve tube so water follows by osmosis
- this water will carry the sucrose by hydrostatic pressure
- sucrose unloaded from phloem at sink
- sucrose moves out of phloem into sink by diffusion
- water follows by osmosis
