gas exchange Flashcards
how do you achieve the best diffusion rates
large area thin permeable moist ( allow a medium in which gases can dissolve) diffusion path must be short
what is gas exchange
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
how do amoeba perform gas exchange
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
what is a flat worm and what advantage does it have
aquatic organism
very flat so large surface area
diffusion pathways are short
what is an earthworm and what advantage does it have
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
characteristics of insects
terrestrial most live in dry habitats small surface area to volume ratio inefficient gas exchange waterproof layer covering surface to prevent water loss dehydration
describe the respiratory system of an insect
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
describe gas exchange in humans
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
how does inspiration in humans work
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
how does expiration in humans work
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
what are antagonistic muscles
internal and external intercostal muscles
what is expiration assisted by
elastic recoil of the lungs following the stretch of elastic fibres
what happens during exercise
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
where does gas exchange in fish occur
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
what is the distance between water and blood cells
5 micrometres
what is the distance between 2 lamellae
50 micrometres
how are lamellae kept apart
water holds them open
how does passive ventilation in fish take place
swim forward with mouth open
point mouth upstream
how does active ventilation in bony fish take place
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
how does parallel flow work
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
what is the concentration limited to in parallel flow
50% as it reaches a concentration equilibrium and no longer has a concentration gradient
what part of the gill lamella does parallel flow use
only part of it
how does counter current flow work
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
why is counter current flow a more efficient system
it used the whole gill lamella as water has a higher oxygen concentration than the blood at all times
what percentage of oxygen can the gills remove from the water
80%
what happens to plants in darkness
no photosynthesis takes place only respiration
the plant doesnt use a transport system
each cell obtains gases it needs by difusion
what adaptations do plants have
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
how do plants combat water loss
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
what other adaptations do plants have
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
how do you reduce water loss in plants
high humidity
low temp
out of the wind
closing the stomata
what do guard cells control
the opening and closing of the stomata
how do guard cells work
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
how does water enter the guard cells
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
