Adaptations for Gas Exchange C3 Flashcards
what happens as a result of a cell increasing in size?
diffusion pathway gets longer
slower diffusion
diffusion will not meet the cell’s needs such as supplying nutrients like oxygen and glucose and removing waste like carbon dioxide
define gas exchange
process of oxygen into cells/blood and removing carbon dioxide
define ventilation
process of bringing an exchange medium like air or water to and from an exchange surface
define respiration
hydrolysis of glucose to form ATP/phosphorylation of ADP
what must happen for an organism to become larger?
a number of cells must come together so it becomes multicellular
describe 5 factors of unicellular organisms such as amoebas
extremely large surface area to volume ratio
gas exchange occurs across the whole surface
permeable membrane allowing diffusion of gases
specialised gas exchange organs are not needed
diffusion is sufficient to meet the oxygen requirements of the organism
describe 5 factors of a flatworm which is a simple multicellular organism
evolved flattened shape to overcome problem of increase in size
this increases SA:V ratio so no cell is far from surface
no specialised gas exchange organs so short diffusion pathway
exchange gases directly with environment by diffusion
diffusion across permeable membrane is sufficient to meet oxygen requirements
describe 6 factors of an earthworm which is a simple multicellular organism
developed tubular shape and restricted to damp environments
worms secrete mucus to keep body surface cells moist allowing gases to dissolve and diffuse
elongated shape provides a large SA:V compared with compact organism of similar volume
exchange gases directly with environment by diffusion across moist surface since blood vessels are close to body surface so gases can diffuse in/out of blood, then across cells covering body surface
blood circulates in vessels maintaining conc. gradient for diffusion of oxygen into cells and CO2 out
blood contains respiratory pigment haemoglobin to carry oxygen to body cells
why do multicellular organisms require a specialised gas exchange surface? give 8 points
as size of organism increases, SA:V decreases
diffusion across body is insufficient to provide enough oxygen for organism to survive
larger organisms more metabolically active so have higher oxygen demand
diffusion pathway across body surface too large and rate of diffusion too slow
(so larger multicellular organisms need specialised gas exchange surface between organism and external environment)
provided with a large area of gas exchange surfaces to increase surface area for diffusion
need a method of circulation to distribute gases around body
many animals have toughened body surface so have internal gas exchange surfaces e.g. lungs
in order to achieve maximum rate of diffusion all respiratory surfaces must be: list 4 things
large surface area to volume ratio
thin
moist
permeable
what 2 additional features increase efficiency of gas exchange in organisms which has a circulatory system and respiratory pigment?
extensive blood supply surrounding exchange surface - circulatory system maintains conc. gradient increasing rate of diffusion
respiratory pigments - haemoglobin increases oxygen-carrying capacity of blood
why do insects need a good supply of oxygen for respiration?
since they fly which requires a lot of energy
why is an insects’ gas exchange system different to other animals?
they don’t use blood to transport gases
how does air go into the insect?
it diffuses into the insect through paired holes called spiracles running along each side of the body. these spiracles lead to a system of branched chitin-lined air tubes called trachea
the spiracles can open and close like valves. why is this important?
when its open it allows oxygen in for respiration but when closed it is to reduce water loss
how do insects ventilate during periods of activity?
at rest, simple diffusion of gases meets the oxygen needs of the insect, during flight movements of the abdomen ventilate the trachea with the aid of air sacs off the trachea
describe the gas exchange surface of insects
the trachea branch repeatedly until they end as very fine thin-walled tracheoles. oxygen diffuses directly from the ends of the tracheoles into the cells and carbon dioxide diffuses out of the cells into the tracheoles. the surface of the tracheoles is lined with chitin which keeps the airways open during body movements while allowing some flexibility
give 4 advantages of the tracheal system for gas exchange
oxygen is supplied directly to tissues
no respiratory pigment needed
oxygen diffuses faster in air than in blood
spiracles close to reduce water loss
what is the disadvantage of the insect tracheal system?
only efficient in smaller organisms and chitin is heavy so it would slow the insect down if it was too large
why are the gas exchange organs retained inside the body of all terrestrial organisms?
reduces water loss
reduces heat loss
protection by the ribs or exoskeleton in insects
what problems are caused by living in water?
less oxygen in water than air
rate of diffusion lower than water
water is more dense so doesn’t flow as easily
what two groups can fish be categorised in?
cartilaginous fish
bony fish
describe cartilaginous fish eg sharks in 5 points
skeleton made of cartilage
nearly all live in sea water
5 gill clefts behind head on each side
water taken in the mouth and forced through gill slits when floor of mouth is raised
gas exchange involves parallel flow: blood in capillaries circulates in same direction as water flowing over gills
describe bony fish eg herring in five points
have internal skeleton made of bone
gills covered with a flap called operculum
live in freshwater and seawater
gas exchange involves counter-current flow : blood in gill capillaries circulates in opposite direction as water flowing over gills
usually 4 gills on each side
how does water flow into, through and out of the fish?
water taken in through mouth, passes over gills and expelled via operculum
movement of buccal cavity floor and operculum allow one-way current of water to flow through gills for gas exchange
describe the structure of the gills of bony fish in 4 points
along each gill arch there are many thin filaments
on these are the gill lamellae
therefore gill filaments have a large SA for gas exchange
blood circulates through gill lamellae into capillaries and CO2 diffuses out into water
describe how countercurrent works
water always meets blood with a higher oxygen concentration
gradient for diffusion of oxygen into blood from water is maintained over the whole length of gill lamellae
oxygen diffuses into blood across the whole length of gill lamellae
counter-current flow more efficient than parallel flow as it results in higher blood oxygen saturation level
describe how parallel flow works
water is taken into the mouth and blood flows through the gill capillaries in the same direction as the water
gas exchange is very efficient at first as there is a very high concentration gradient
about halfway along the gill lamellae, equilibrium is reached and diffusion of oxygen and carbon dioxide is no longer possible
describe briefly the gas exchange in amphibian larvae
the larvae live in water so have gills for gas exchange
the adult amphibians are terrestrial so live on land
describe briefly the gas exchange in adult amphibians
when inactive, diffusion happens across their moist skin
when active, it happens across lungs
describe the lung structure of an amphibian
lungs have a simple structure with little folding of the gas exchange tissues
give the names of structures in the human breathing system
give 14
larynx, cartilage, tracheae, left lung, bronchus, heart, diaphragm, alveoli, pleural membranes, ribs, pleural cavity, inner intercostal muscles, outer intercostal muscles, bronchiole
why do rings of cartilage support the trachea, bronchi and bronchioles?
prevents them from collapsing during inspiration when the pressure is low
what is the name of the airtight compartment of the body that encloses the lungs?
thorax
what is the role of goblet cells?
produce and secrete mucus to trap microorganisms, cilia will then waft to move the mucus up and out of the trachea.
why is there pleural fluid in the pleural cavity?
lubrication
prevents friction with other organs
helps lungs to stick with thorax and expand with it
what is in each bronchiole?
hundreds of alveoli providing a large surface area to volume ratio
describe briefly about alveolus
each alveolus lined with thin film of water to allow gases to dissolve and diffuse
lined with lung surfactant which prevents watery lining from creating surface tension
describe what happens to the alveoli due to emphysema lung tissue disease
alveoli air sacs broken down
drastically reduced gas exchange surface area, reducing surface area to volume ratio
scarring thickens the walls of the alveoli reducing the efficiency of diffusion.
describe the ventilation of the human lungs during inspiration and expiration
inspiration:
external intercostal muscles and ribs contracts and moves out and up
outer pleural membrane moves out and up with the ribcage
inner pleural membrane moves out and up with the outer pleural membrane as the pressure in the pleural cavity decreases
thorax increases in volume
diaphragm contracts (flattens)
alveoli increase in volume and lungs pulled out
pressure in alveoli decreases below atmospheric pressure
expiration:
external intercostal muscles and ribs relaxes and moves in and down
outer pleural membrane moves in and down
inner pleural membrane moves in and down
thorax decreases in volume
diaphragm relaxes (dome shape)
alveoli decrease in volume and lungs move in
pressure in alveoli increases above atmospheric pressure
describe the pressure changes during inspiration in 4 points
diaphragm flattens and rib cage expands pulling on outer pleural membrane, which lowers pressure in pleural cavity
inner pleural membrane pulls on lungs which increases volume of lungs/alveoli
this decreases pressure in alveoli
pressure in alveoli is below atmospheric pressure so air moves in
what changes would you expect to see during strenuous exercise?
greater/faster pressure and volume changes
faster (inspiration/expiration/)breathing
why is the alveoli suitable as a gas exchange surface? (Give 5 points)
large SA:V ratio due to many alveoli
moist
short diffusion distance due to extensive capillary network
walls of alveoli and capillaries are one cell thick
maintained conc. gradient - circulation of blood/ventilation of air
describe what is surfactant
a chemical substance covering the surface of alveoli, reduces surface tension, prevents alveoli from sticking together and collapsing when breathing out
why is the cellular demand for oxygen in a mammal higher compared to a fish the same size?
mammals are warm-blooded and have to maintain their body temp.
list 12 structures in the breathing system and their function
external intercostal muscles - when these contract, the ribs are pulled up and out increasing the volume of the thorax
bronchioles - bronchi branch into these smaller tubes
larynx - box-shaped structure above trachea containing vocal cords
alveoli - main site of gas exchange
bronchi - trachea splits into 2 of these
surfactant - prevents alveoli from sticking together and collapsing, reduces surface tension
trachea - tube held open by rings of C-shaped cartilage
ribs - bones moved by intercostal muscles and alter the size of the thorax
diaphragm - dome-shaped muscle relaxes and contracts altering the volume of the thorax
pleural cavity - contains pleural fluid which acts as a lubricant to reduce friction between lungs and inside wall of thorax during ventilation
epiglottis - flap of skin that stops food entering the trachea when swallowing
pleural fluid - acts as a lubricant providing friction-free movement against the inner wall of the thorax
out of all organisms studied, which need haemoglobin?
mammal, amphibian, earthworm, fish
where is the ventilation in the fish?
buccal floor movements
which organism has water as their respiratory medium?
amoeba, flatworm, fish , amphibian (air also)
what are the 4 adaptations of leaves to gas exchange?
flat/thin
air spaces in spongy mesophyll - a lot of cell walls are in contact with air
mesophyll walls wet due to transpiration
structural pores
how do plants respire?
they generate ATP so they respire all the time
oxygen is required
when light available, plants carry out photosynthesis using chloroplasts, carbon dioxide is required
how are plant leaves adapted for photosynthesis? give 7
large surface area to absorb as much light as possible
leaves can orientate themselves towards the sunlight
leaves are thin to allow light to penetrate lower layers
cuticle and epidermis are transparent to allow light to pass through the mesophyll below
palisade cells are elongated and densely packed together and contain many chloroplasts
chloroplasts can move and rotate within the mesophyll cells to maximise light absorption
intercellular air spaces allow carbon dioxide to diffuse into cells and oxygen and water vapour to diffuse away
where in the leaf is the stomata found and what is their role?
lower epidermis
to allow co2 in
how many guard cells surround each stoma?
2
what is unusual about guard cells?
they are the only epidermal cells that contain chloroplasts
they have unevenly thickened inner cell wall
what causes the stomata to open?
light makes K+ ions and water to enter guard cells causing change in shape
or
potassium pump and entry of water causes stomata to open
how does the structure of stomata help it to open/close?
inner cell wall is thick and outer wall is thin so if guard cells become turgid pore opens and if guard cell becomes flaccid pore closes
in some plants inner cell wall is thin so ends of guard cells expand and stoma opens
describe in detail the mechanism for stomatal opening (give 5 points)
K+ Ions actively transported from epidermal cells into guard cells
stored starch, insoluble, in guard cells is converted to malate, soluble, by enzymes in cytoplasm
both above processes happen due to ATP
water potential in guard cells is lowered so water enters by osmosis
guard cells become turgid and curve apart because outer cell walls are thinner than inner cell walls so have more stretch
why are stomata open during the day and closed at night?
open - plants need co2 to diffuse into the leaf for photosynthesis
close - allows plants to reduce water loss
what do chloroplasts provide as a result of photosynthesis?
glucose
energy
ATP
sugar
