Transport Flashcards
How the transport of N’a+ is involved in the absorption of glucose/amino acids
Na+ is actively pumped out of the cell into the blood capillaries by the sodium potassium pump by ATP
The conc of N’a+ in epithelial cells decreases so
Na moves into cell by FD g/aa being cotransported with it against the glucose conc gradient
G/sa is transported into blood capillaries by FD
Insects- countering water loss
Waterproof covering-rigid exoskeleton (chitin)
Waterproof cuticle
Lower sa:v minimising water loss
Insect problems
Impermeable to gases-can’t rely on simple diffusion of oxygen for respiration
Insect adaptions
Network of trachea
Tracheoles-thin permeable walls:short diffusion pathway
-ends have fluid so gases can dissolve diffusing towards respiratory cells
Spiricles-tiny holes
Controlled by muscles
Why control spiracles
Permanently open -vulnerable to water loss
Hairs-trap humid air:lower wp gradient
Air sacs advantage
Close spiracles-Less diffusion-gases are stored so gas exchange can occur but dehydration won’t
What causes spiracles to open
Increase in co2 /waste product
Fish problems
Waterproof outercoat
Water is denser than air
Lower sa:v
Why is it better fish have countercurrent flow
Equilibrium isn’t reached
Almost all o2 diffuses into blood
Full lamellar advantage
Increase surface area
Leaf adaptations
No cell from a stoma so short diffusion pathway
Large sa:v:spongy mesophyll
Cohesion tension theory
H20 dipoles attract-cohesion
Forces of attraction between water and polar groups in cell walls-adhesion
Water pulled up by negative hydrostatic pressure from transpiration because of cohesive tension
Xylem is a continuos collum of water
Evaporation -transpiration
Wp in roots decreases
H20 enters by osmosis
Controlling stomata
Closed by guard cells
Guard cells curve apart when turgid
When flaccid edges of the cell lie close together but this slows transpiration
Decreasing photosynthesis
Leaf adaptations
Waxy cuticle-impermeable
Most stomata under leaf-cooler
Thick leaves-less water loss
Hairs/spines-trap moist air
Pits
• Stomata closed at certain times of the day.
• Stomata may be sunken and found in pits.
• Guard cells curve apart when turgid.
• When flaccid, the edges of the cells lie close together.
• However, this drastically slows transpiration and means that no carbon dioxide can enter the leaf (= no photosyn
Xerophytes are
Plants adapted to living in areas where water loss is in short supply
Xerophyte water loss combating
Thick cuticle-longer diffusion pathway
Rolling up of leaves-traps still moist air-lower WP gradient
Hairy leaves-lower WP gradient
Pits-lower WP gradient
Lower sa:v slower diffusion
Where are xerophytes found
Desert
Salt marshes
Coastal regions
Cold regions
Translocation
AT-solutes actively loaded source to sieve tubes by companion cells
O-WP in sieve tubes falls so h20 enters from xylem and companion cells
P rise-high hydro p at source
I-solutes removed at sink by AT ,so WP increases in sieve tubes by osmosis
P fall-sink p decreases as water moves out = maintains pressure gradient
When investigating the effect of something on rate of translocation, they made rate of photosynthesis constant, why
-rate of photosynthesis is related to rate of sucrose production
- rate of translocation is higher when sucrose concentration is higher
- Describe the route air takes to get through the nose into the lungs (correctly sequence the structures it passes through)
Nose, trachea, bronchus (bronchi), bronchioles, alveoli
What is present in the trachea and bronchi to prevent them from collapsing? What could cause them to collapse?
Cartlidge, changes in air pressure in thorax
Wheredoesgasexchangetakeplaceinthelungs
Alveoli
Explain two key features that the gas exchange surface has to increase the rate of diffusion
- Thin (2 cells thick) – short diffusion pathway,
excellent blood supply – maintains the diffusion gradient,
folded/large number of alveoli – increases the surface area for exchange to occur over,
moist surface – allows gases to dissolve before passing into the bloodstream
Why do larger mammals have a higher oxygen demand than smaller mammals?
Larger mammals have a larger volume of living cells that require oxygen for respiration, higher metabolic rate (and respiratory rate) to maintain a high body temperature
How is the diffusion gradient maintained between the air and blood?
Ventilation (brings in fresh air and takes away carbon dioxide), circulation carries away oxygenated blood
What are the advantages of the lungs being inside the body?
Reduces water loss from the organism – so surface and entire body does not dry out, air is not dense enough to support and protect the delicate structures
Evidence for Cohesion-tension theory
• Change in the diameter of tree trunks according to the rate of transpiration – when transpiration is at its greatest = more tension (more negative pressure) in the xylem – xylem vessels pulled inwards → tree trunk shrinks in diameter
• If a xylem vessel is broken and air enters, the tree can no longer draw up water – breaking the continuous column of water.
• When a xylem vessel is broken – water does not leak out, as would be the case if it was under pressure – instead air is drawn in, consistent with being under tension
