Topic 4 -gaseous exchange systems

Question 1

name 7 layers of a plant leaf:

Answer 1

• waxy cuticle
• upper epidermis
• paliside mesophyll layer
• spongey mesophyll layer
• lower epidermis layer
• guard cells
• stomata

Question 2

layers of a plant leaf

waxy cuticle
what does it do?

Answer 2

• prevents water loss

Question 3

layers of a plant leaf

upper epidermis
-characterisitcs?
- which does what?
- found where in leaf?

Answer 3

• transparent to allow maximum light through to cells w/ chloroplast
• below cuticle. The epidermis is the top layer

Question 4

layers of a plant leaf

palisade mesophyll layer
- how ceels stacked?
- what do they contain? and why?
- whaere are they in the leaf?

Answer 4

• cells stacked vertically to fit in as many cells as possible.
• These cells contain the most chloroplast. To maximise the energy transfer in photosynthesis.
• below upper epidermis
• composed of cylindrically shaped cells oriented perpendicular to the leaf surface.

Question 5

layers of a plant leaf

spongey mesophyll layer
- what does it have and what for?
- where is it located?

Answer 5

• air spaces provide increased surface area for gas exchange
• the center mesophyll, between the palisade mesophyll layer and the lower epidermis of the leaf

Question 6

layers of a plant leaf

guard cells

Answer 6

• walls are thicker on side adjacent to stomata to enable opening + closing

Question 7

layers of a plant leaf

stomata

Answer 7

guard cells open + close to prevent excessive water loss

Question 8

plants

how do the stomata open

aside from guard cells

Answer 8

opens by ions (k+)by moving into guard cells by active transport, causing water to move by osmois bc the water potential decreased, which makes gaurd cells turgid. This causes guard cells to swell+ stomata open

Question 9

What makes guard cells turgid

Answer 9

ions moving into guard cells by active transport, water moving by osmosis

Question 10

what are lenticles

Answer 10

areas of loosely arranged cells whcih act as a pore to allow gas exchange in lignified (woody) plants

Question 11

gaseous exchange in mammals happens where

Answer 11

lungs

Question 12

mammals

Boyle’s law?

what does this mean?

Answer 12

Volume is inversley proportional to pressure

• means inhalation happens by contraction of the intercostal muscle and diaphram. This casues volume to increase, which causes pressure to decrease and air moves into lungs by diffusion down pressure grandient

Question 13

mammals

what happens in exhalation

Answer 13

intercostal muscles + diaphram relax = decreased vol = increased pressure =mair diffuses out down the pressure gradient

Question 14

mammals

what in the lungs provides a large S.A

Answer 14

alveoli

Question 15

mammals

why to the capillaries have a short diffusion distance

not bc theyre one cel thick

Answer 15

• one layer of epithelial cells provides short diffusion distance

Question 16

mammals

why is the conc. gradient steep in capillaries

Answer 16

bc the blood in capillaries is deoxygenated as the oxygenated blood is carried away, so conc. gradient is always steep

Question 17

insects

insects have a ____?____ gas system bc they have an ___?__
whcih ___?__ thewm from taking gas via __?__ through the skin

Answer 17

insects have a specialised gas system bc they have an exoskeleton which prevents them from taking gas via diffusion through the skin

Question 18

insects

what are the openings on insects called (pores)?

Answer 18

spiracles

Question 19

how are spiracles closed and opened.and why do they?

Answer 19

by Sphincters to prevent water loss

Question 20

insects

what is trachea lined with? and whats its purpose

Answer 20

rings of chitin. prevents it from collapsing

Question 21

insects

why cant the trachea carry out gas exchange?

Answer 21

bc its lined with rings of chitin wehich make it impermeable

Question 22

insects

what gas diffuses through the spiracles

Answer 22

O2

Question 23

from the trachea where does O2 diffuse into?

Answer 23

the tracheoles bc theyre permeable

Question 24

what happens when water builds up at the bottom of tracheoles, slowing diffusion.

Answer 24

water is removed in active insects bc lactic acid builds up in cells, whcih lowers water potential, so water moves into cells by osmosis, gas exchange to occur.
- some ative insects have to ventilate their repiratory systems via mechanical ventiliation (pumping abdomen) and/ or air reserves

Question 25

fish

process of which gas echange happens in fish

Answer 25

• floor of mouth opens ( Buccal cavity)
• operculum (gill flaps) close s
• floor of mouth closes (increases pressure, valve stops water leaving)
• increased pressure forces operculum open = forces water over the gills

Question 26

fish

why is gas exchange in water more difficult?

Answer 26

bc water is denser and more visous than air, only contains 5% of Oxygen

Question 27

what law is used to pump water over the gills

Answer 27

Boyle’s law

“volume is inversley proportional to pressure.”

Question 28

fish

gills are made of ? that are covered by folds called ?

Answer 28

made of fillaments, covered by lamellae

Question 30

why is the constant movement of water over gills good?

Answer 30

• it keeps them spread out = increased S.A + prevents them sticking together

Question 31

fish

how do you maintain the conc. gradient btwn water and rich blood supply in capillary network in the lamellae

Answer 31

with a counter current system

draw one out

Question 32

what hapens in a counter current system?

Answer 32

this is where the water flowing over the gills and blood in gill fillaments flow in opposite directions, maintaining a steep conc. gradient over entire gill fillament