Transport

Question 1

How the transport of N’a+ is involved in the absorption of glucose/amino acids

Answer 1

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

Question 2

Insects- countering water loss

Answer 2

Waterproof covering-rigid exoskeleton (chitin)
Waterproof cuticle
Lower sa:v minimising water loss

Question 3

Insect problems

Answer 3

Impermeable to gases-can’t rely on simple diffusion of oxygen for respiration

Question 4

Insect adaptions

Answer 4

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

Question 5

Why control spiracles

Answer 5

Permanently open -vulnerable to water loss
Hairs-trap humid air:lower wp gradient

Question 6

Air sacs advantage

Answer 6

Close spiracles-Less diffusion-gases are stored so gas exchange can occur but dehydration won’t

Question 7

What causes spiracles to open

Answer 7

Increase in co2 /waste product

Question 8

Fish problems

Answer 8

Waterproof outercoat
Water is denser than air
Lower sa:v

Question 9

Why is it better fish have countercurrent flow

Answer 9

Equilibrium isn’t reached
Almost all o2 diffuses into blood

Question 10

Full lamellar advantage

Answer 10

Increase surface area

Question 11

Leaf adaptations

Answer 11

No cell from a stoma so short diffusion pathway
Large sa:v:spongy mesophyll

Question 12

Cohesion tension theory

Answer 12

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

Question 13

Controlling stomata

Answer 13

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

Question 14

Leaf adaptations

Answer 14

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

Question 15

Xerophytes are

Answer 15

Plants adapted to living in areas where water loss is in short supply

Question 16

Xerophyte water loss combating

Answer 16

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

Question 17

Where are xerophytes found

Answer 17

Desert
Salt marshes
Coastal regions
Cold regions

Question 18

Translocation

Answer 18

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

Question 19

When investigating the effect of something on rate of translocation, they made rate of photosynthesis constant, why

Answer 19

-rate of photosynthesis is related to rate of sucrose production
- rate of translocation is higher when sucrose concentration is higher

Question 20

1. Describe the route air takes to get through the nose into the lungs (correctly sequence the structures it passes through)

Answer 20

Nose, trachea, bronchus (bronchi), bronchioles, alveoli

Question 21

What is present in the trachea and bronchi to prevent them from collapsing? What could cause them to collapse?

Answer 21

Cartlidge, changes in air pressure in thorax

Question 22

Wheredoesgasexchangetakeplaceinthelungs

Answer 22

Alveoli

Question 23

Explain two key features that the gas exchange surface has to increase the rate of diffusion

Answer 23

4. 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

Question 24

Why do larger mammals have a higher oxygen demand than smaller mammals?

Answer 24

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

Question 25

How is the diffusion gradient maintained between the air and blood?

Answer 25

Ventilation (brings in fresh air and takes away carbon dioxide), circulation carries away oxygenated blood

Question 26

What are the advantages of the lungs being inside the body?

Answer 26

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

Question 27

Evidence for Cohesion-tension theory

Answer 27

• 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