AS- exchange

Question 1

How 02 in air reaches cappilaries surrounding alveoli in lungs ( no deatails of breathing required)

Answer 1

. down tranchae > into the 2 bronchi then bronchioles
.o2 travels down a pressure gradient
. down a diffusion gradient
. across alveolar epithilium
. across capillary epithelium

Question 2

why are lungs located inside body (textbook)

Answer 2

air is not dense enough to support it because delicate

the body would lose water and dry out

Question 3

site of gas exchange in lungs?

Answer 3

alveolar epithilium, diffusion gradient maintained

Question 4

How CO2 moves from capillaries to the alveoli?

Answer 4

by simple diffusion, from capillary epithilieum to alveolar endothelium

Question 5

process of inhalation

Answer 5

intercostal muscles contract> rib cage moves up and out> diaphram contacts and flatterns> decreased pressure and increased volume so air is forced in

Question 6

process of exhalation

Answer 6

intercostal muscles relax> rib cage moves down and in> diaphram relaxes > increased pressire and decreased volume so air forced out

Question 7

many large animals have blood systems, explain why these animals need blood systems to supply cells with o2

Answer 7

large diffusion distance between gas exchange surface and some respiring tissues
diffusion is slow
so blood system is needed as blood allows rapid transport of 02 to respiring cells

Question 8

translocation in phloem

Answer 8

sucrose is actively loaded into phloem by companion cells at source
increase in sugar concentration > lower water potential in phloem
water moves into phloem from xylem by osmosis
> ^vol of water so hydrosatic pressure ^> causes mass movement to sink/root
> sugars used in respiratoin