gas exchange

Question 1

how do you achieve the best diffusion rates

Answer 1

large area
thin 
permeable 
moist ( allow a medium in which gases can dissolve) 
diffusion path must be short

Question 2

what is gas exchange

Answer 2

the diffusion of gases down a concentration gradient across a respiratory surface between or organism and its environment. the gases being exchanged are CO2 and 02

Question 3

how do amoeba perform gas exchange

Answer 3

use the cell membrane as a gas exchange surface. the diffusion can occur through the membrane as it is:
thin - moist - permeable - diffusion path is short

Question 4

what is a flat worm and what advantage does it have

Answer 4

aquatic organism
very flat so large surface area
diffusion pathways are short

Question 5

what is an earthworm and what advantage does it have

Answer 5

terrestrial
cylindrical less surface area
their skin is the respiratory surfaces they secrete out a mucus to make their skin soft
they have haemoglobin to carry the oxygen away from the surface in order to maintain a concentration gradient

Question 6

characteristics of insects

Answer 6

terrestrial 
most live in dry habitats 
small surface area to volume ratio 
inefficient gas exchange 
waterproof layer covering surface to prevent water loss 
dehydration

Question 7

describe the respiratory system of an insect

Answer 7

every segment has a spiracle leads into a trachea which leads into tracheoles and goes to all respiring cells in body
ventilation to change pressure

Question 8

describe gas exchange in humans

Answer 8

gas exchange occurs in the lungs
connected to the outside air with a set of tubes
the trachea starts at the back of the mouth and branches to form 2 bronchi
one bronchus goes into each lung
each bronchus branches many times getting smaller to form tubes called bronchioles
at the end of the bronchioles are alveoli
each alveolus is folded for a set of interconnected spaces there are many alveoli providing a large surface area for gas exchange
the alveoli surrounded by blood capillaries transporting blood to and from the lungs

Question 9

how does inspiration in humans work

Answer 9

ribcage expands as rib muscles contract
impulse from brain causes intercostal muscles to contract 
diaphragm contracts 
air pressure in lungs decreases 
air movement into lungs 
lung volume increases

Question 10

how does expiration in humans work

Answer 10

rib cage gets smaller as rib muscles relax
no nerve impulses are sent
diaphragm relaxes and air pressure in lungs increases
air movement out of lungs
lung volume decreases

Question 11

what are antagonistic muscles

Answer 11

internal and external intercostal muscles

Question 12

what is expiration assisted by

Answer 12

elastic recoil of the lungs following the stretch of elastic fibres

Question 13

what happens during exercise

Answer 13

impulses are sent to contact internal intercostal muscles for a more forceful expirations and contraction of the abdominal muscles to push the diaphragm into a more domed position

Question 14

where does gas exchange in fish occur

Answer 14

in gills which are supported by a gill arch which is made of bonds
the space between the gill arch is called gill slit
each gill has two rows of gill filaments which are covered in folds called lamellae

Question 15

what is the distance between water and blood cells

Answer 15

5 micrometres

Question 16

what is the distance between 2 lamellae

Answer 16

50 micrometres

Question 17

how are lamellae kept apart

Answer 17

water holds them open

Question 18

how does passive ventilation in fish take place

Answer 18

swim forward with mouth open

point mouth upstream

Question 19

how does active ventilation in bony fish take place

Answer 19

1- mouth opens and operculum closes
2- buccal cavity lowers so volume increases, pressure decreases which creates a pressure difference so water flows in
3- mouth closes and operculum opens
4- buccal floor raises and pressure increases
5- water if forced across gills, gill cavity pressure increases
6- operculum opens

Question 20

how does parallel flow work

Answer 20

cartilaginous fish have no special mechanism to force water over the gills, they rely on swimming for ventilation
blood travels the same direction as water

Question 21

what is the concentration limited to in parallel flow

Answer 21

50% as it reaches a concentration equilibrium and no longer has a concentration gradient

Question 22

what part of the gill lamella does parallel flow use

Answer 22

only part of it

Question 23

how does counter current flow work

Answer 23

blood in the gill capillaries flows in the opposite direction to the water flowing over the gill surface
water has a higher oxygen concentration than the blood

Question 24

why is counter current flow a more efficient system

Answer 24

it used the whole gill lamella as water has a higher oxygen concentration than the blood at all times

Question 25

what percentage of oxygen can the gills remove from the water

Answer 25

80%

Question 26

what happens to plants in darkness

Answer 26

no photosynthesis takes place only respiration
the plant doesnt use a transport system
each cell obtains gases it needs by difusion

Question 27

what adaptations do plants have

Answer 27

cuticle - prevents gas exchange in that area and prevents water loss
stomata - gases come in
large surface area and thin
spongy mesophyll - gas exchange occurs, moist and diffuse into mesophyll
palisade mesophyll contains lots of chlorophyll

Question 28

how do plants combat water loss

Answer 28

stomata opens and closes

water evaporates from the wet cell walls in and contact with any air spaces in the leaf and is lost by transpiration

Question 29

what other adaptations do plants have

Answer 29

surface of mesophyll cells in contact with air spaces in leaf
surface is large and diffusion distances are small
so gases only have to travel across a single cell

Question 30

how do you reduce water loss in plants

Answer 30

high humidity
low temp
out of the wind
closing the stomata

Question 31

what do guard cells control

Answer 31

the opening and closing of the stomata

Question 32

how do guard cells work

Answer 32

have chloroplasts
cell walls are rigid
when cells absorb water it expands and becomes turgid
when cells lose water they become flaccid and collapse
cell walls are thinner in some places and expand less so a pore is created

Question 33

how does water enter the guard cells

Answer 33

chloroplasts in the guard cells photosynthesis and produce carbohydrates
ATP produce energy for active transport of potassium ions into the guard cells
potassium and malate (stored starch) lower the water potential making it more negative and water enters by osmosis