b4 Flashcards
upper epidermis in plant
thin and transparent layer to allow light to enter
waxy cuticle in plants
protective layer on top of leaf, prevents water from evaporating
palisade mesophyll in plants
rectangular shaped cells, tightly packed that contain lots of chloroplasts to absorb as much light as possible, maximising photosynthesis
spongy mesophyll in plants
contains tiny air spaces which increase surface area for diffusion of gases, mainly carbon dioxide
lower epidermis
guard cells and stomata
guard cells
opens and closes the stomata to allow gases to diffuse in and out the plant
stomata
where gas exchange in plants take place, opens during the day and closes at night, also allows evaporation of water. it’s found in the underside of the plant which means that less water is lost
what is the vascular bundle
contains xylem and phloem cells which transfer substances through the plant
transpiration stream
loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata
how xylem tubes are adapted for transpiration
- have ligin which strengthens the plant to help withstand pressure of water movement
- lined with dead cells which are hollow and form a continuous tube for water and mineral ions to travel through roots
- movement is only in one direction from roots to leaves
factors affecting rate of transpiration
air humidity - more humid means less transpiration as the concentration gradient is lower, so slower diffusion
temperature - higher temperature means more transpiration as particles have more energy therefore can evaporate faster
wind - more wind means more water vapor from air is removed which increases the concentration gradient so more water is lost
light intensity - the higher the light intensity, the more turgid the guard cells, so the stomata are open so more water can be lost.
how is the phloem adapted to its function
Phloem is composed of tubes of elongated cells. Cell sap can move from one phloem cell to the next through pores in the end walls
what is translocation
the transport of sucrose and amino acids in phloem, from regions of production to regions of storage or use. happens in all directions as opposed to the transpiration stream which is only from the roots to the leaves
arteries
transport blood away from heart. must be able to withstand high pressure from the heart contracting.
- thick walls with elastic fibres which allows the artery wall to expand around blood surging through at high pressure when the heart contracts
- narrow lumen -> maintains high blood pressure
veins
transport blood to the heart. blood travels at low pressure
- thin walls and large lumens.
- Veins contain valves that prevent the backflow of blood, helping return blood to the heart
capilaries
have thin walls which are “leaky”, allowing substances to leave the blood to reach the body’s tissues
- only one cell thick which reduces diffusion distance
components of blood
red blood cells, white blood cells, platlets, plasma
red blood cells
- biconcave shape gives large surface area to volume ratio which maximises efficiency of diffusion of gases
- cytoplasm has haemoglobin which binds to oxygen forming oxyhaemoglobin
- transports oxygen around the body for cells to respire
white blood cells
part of the immune system, responsible for defending the body from infection by recognising and destroying pathogens
platelets
- fragments of cells (they contain cytoplasm but no nucleus)
- when damage to a blood vessel occurs, the platelets are involved in forming a blood clot to prevent blood loss
- they release chemicals that cause soluble protens to form a mesh of insoluble fibres across the wound.
lung adaptations for gas exchange
- Large surface area to allow faster diffusion of gases across the surface
- Thin walls to ensure diffusion distances remain short
- Good ventilation with air so that diffusion gradients can be maintained
- Good blood supply (dense capillary network) to maintain a high concentration gradient so diffusion occurs faster
what happens in coronary artery disease
layers of fatty material build up inside the coronary arteries, narrowing them. this reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle
what do stents do
Stents are used to keep the coronary arteries open.
- A narrow tube is threaded up through the groin up to the blocked vessel
- A tiny balloon is then inflated
- The balloon pushes the metal or plastic stent against the wall of the artery, increasing the width of the lumen
- The balloon and tube are then removed
what do statins do
drugs that are widely used to reduce the levels of fatty deposits (cholesterol) in the blood
- reduce the amount of LDL in blood (bad cholestrol) and increase HDL too
evaluate statins vs stents
stents: procedure is simple, reduce risk of heart attack, but risk of thrombosis (blood clots)
statins: reduce LDL so lower risk of heart attacks as less plaque build up, increase HDL, drug so must be taken regularly, take a while to start having an effect, there are side effects to it
what happens with faulty heart valve
cannot open/close, might leak
- reduces volume of blood pumped by heart so less oxygenated blood is pumped around the body so less aerobic respiration
treatment for faulty valves, and pros and cons of each method
can use biological valves - from humans, pigs, cows or use mechanical valves
mechanical - lasts much longer, but might cause blood clots so need blood thinning drugs which might have side effects
biological - cheaper, works pretty well, however, could trigger immune response, and ethical issue as taken from animals
heart failure treatment
artificial heart, or heart transplant
heart transplants have long wait time and they could be rejected/trigger an immune response
what is a double circulatory system?
two pumps working at the same time to transport the blood in differentdirections
advantages of double circulatory system
- Blood travelling through the small capillaries in the lungs loses a lot of pressure which reduces the speed at which it can flow
- By returning oxygenated blood to the heart from the lungs, the pressure can be raised before sending it to the body, meaning cells can be supplied with oxygenated blood more quickly
