Gas Exchange Flashcards
What is the total oxygen requirement proportional to?
the volume of the organism
What is the rate of absorption of oxygen proportional to?
the organisms surface area
What are the common features of gas exchange surfaces?
large surface area relative to volume
permeable
thin
moist
mechanism to maintain diffusion gradients
What are the 3 main factors that affect the need for a specialised transport system?
Volume -> an increase in the layers of cells means that less oxygen can diffuse into the organism (can only occur across 2 cells w/o specialised carriers) as it would be used up by outer cells first
Level of Activity -> animals require the energy released by food in respiration to enable them to move around, if the animals is active or needs to keep warm the animal requires larger volumes of oxygen and nutrients to supply energy
Surface area to volume ratio
Describe gas exchange generally for small organisms
don’t need a transport system
their cells are surrounded by the environment they live in
can rely on diffusion to supply the substances required
Describe gas exchange in amoeba
a single-celled organism that has a very large SA:V (pseudopodia) so that simple diffusion through cell membrane is fast enough to meet oxygen demands (short diffusion pathway)
lives in fresh water ponds
removes CO2 fast so cytoplasm doesn’t become acidic and enzymes can’t function
Describe gas exchange in flatworms
a multicellular organism with a smaller surface area to volume ration but are flattened to reduce diffusion distance and so they can rely on their external surface for gas exchange
Describe gas exchange in earthworms
a multi-cellular organism
smaller SA:V as it’s cylindrical but it’s elongated
diffusion happens across the moist skin but has a closed circulation with haemoglobin to carry oxygen to tissues and each cell
haemoglobin and circulation maintain a steep concentration gradient
since the skin has to stay moist it restricts the environment to damp soil
Why do terrestrial organisms have gas exchange organs inside the body?
to reduce water and heat loss
Describe the gas exchange in amphibians (e.g. frogs)
both terrestrial and aquatic
gas exchange takes place across the skin (at rest) and lungs (when active)
the skin is moist, permeable and has a well developed capillary network
undergoes metamorphosis when going from the larval form to the adult form
Describe the gas exchange in reptiles
gas exchange takes place across the lungs with in-growths of tissue to increase SA
movement of the ribs aid in the ventilation of the lungs
Describe the gas exchange in birds
gas exchange takes place in the lungs with air sacs
air sacs act as bellows, when the bird breathes in any air that remains in the lungs from the last breath gets sucked into air sacs = lungs always filed with fresh air
no diaphragm but ribs and flight muscles ventilate lungs
Describe the gills as the special respiratory surface in fish
one-way current of water kept flowing by ventilation mechanisms which maintains concentration gradient
large surface area provided by the gill filaments (density of water flowing through prevents gills from collapsing)
extensive network of blood capillaries to allow efficient diffusion and haemoglobin for oxygen carriage
thin layer of cells separate blood from outside water
Describe the gas exchange organ in bony fish?
called gills
fish possess several gills located between their buccal cavity (mouth cavity) and a chamber at the sides of their mouth called the opercular cavity
Compare bony fish to cartilaginous fish
Bony:
skeleton made of bones
lives in sea or fresh water
covered in scales (= no exchange through surface)
gills inside opercular cavity
gas exchange involves a counter-current system
Cartilaginous:
skeleton made of cartilage
mostly live in the sea
covered in scales
contain gill clefts
gas exchange involves a parallel system where the water and blood travel in the same direction
Draw a labelled diagram of a gill (bony fish)
Gill Arch: bony structure to support gill filaments and rakers
Gill Rakers: filter water and trap prey
Gill Filament (gas exchange surface): provides a large SA, filled with blood and short diffusion path (gill plates)
Why is water harder to respire in than air?
contains a low concentration of oxygen (1/30th of the concentration in air)
denser and more viscous than air making it harder to move in
What is the ventilation mechanism for taking in water?
mouth opens
operculum cavity closes
floor of the mouth is lowered
volume inside the mouth cavity increases
pressure inside the mouth cavity decreases
water flows in as the external pressure is higher than the pressure inside the mouth
What is the ventilation mechanism to force water out?
mouth closes
operculum opens
floor of the mouth is raised
volume inside the mouth cavity decreases
pressure inside the mouth cavity increases
water flows out over the gills because the pressure in the mouth cavity is higher than in the opercular cavity
What is meant by a counter current flow?
blood and water flow in opposite directions at the gill lamellae, maintaining the concentration gradient across the entire length
Why is counter current flow more efficient?
Concentration gradient maintained over entire distance of gill lamellae (diffusion occurs across entire length)
What is meant by parallel flow?
blood and water flow in the same direction at the gill lamellae, maintaining the concentration gradient for oxygen to diffuse into the blood only up to the point where its concentration in the blood and water is equal (50% max and not maintained across entire length)
Define the term ‘breathing’
the passage of air into and out of the lungs to supply the blood with oxygen
Define the term ‘ventilation’
movement of diaphragm and rib cage that brings air into and out of the lungs
Define the term ‘respiration’
the metabolic process by which an organism obtains energy by reacting O2 with glucose to give H2O, CO2 and ATP
What is the function of the human breathing system?
to supply respiring tissues with oxygen
reduce heat and water loss
Name and draw a diagram of the lungs
tongue
epiglotis
oesophagus
trachea
cartilage rings
ribs
intercostal muscles
bronchi
bronchioles
pleural membranes
pleural space
diaphragm
Why are the cartilage rings not complete?
allows the oesophagus behind it to bulge as food is being swallowed
Name the parts of the trachea section
larynx
trachea
rings of cartilage
bronchi
bronchioles
Draw and label the cross section of a bronchiole
smooth muscle
ciliated epithelium
loose tissue with elastic fibres
goblet cell
blood vessel
Draw and label the cross section of the trachea
cartilage
smooth muscle and elastic fibres
ciliated epithelium with goblet cells
small blood vessel
mucus secreting gland
What is the function of the goblet cells and positions in the gas exchange system?
secrete a sticky mucus which traps tiny particles in the air (e.g. pollen and bacteria)
this reduces the chance of infection as they are removed from the lungs
found in the trachea, bronchi and large bronchioles
What is the function of ciliated epithelial cells and positions in the gas exchange system?
cells have tiny hair like structures which waft the mucus up the airway to the back of the throat where it can be swallowed
trachea, bronchi and large bronchioles
What is the function of cartilage and positions in the gas exchange system?
supports the trachea and bronchi by holding them open and preventing them from collapsing during pressure changes in inspiration or expiration
trachea, bronchi and large bronchioles
What is the function of elastic fibres and positions in gas exchange system?
stretch during inhalation, the alveoli expand increasing the SA
elastic recoil of alveoli in expiration, helps force air out
found in trachea, bronchi, bronchioles and alveoli
What is the function of smooth muscle and positions in the gas exchange system?
adjusts the size of the airways, it can contract which causes the constriction of airway, restricting flow
trachea, bronchi and bronchiole
What are the parts of the alveoli?
branch of pulmonary vein
branch of pulmonary artery
capillary network
bronchiole
State 5 ways in which the alveoli are efficient at gas exchange?
provide a large surface area
gases dissolve in the surfactant moisture lining the alveoli (moist)
walls made of squamous epithelium, diffusion pathways is short
extensive capillary network maintains diffusion gradients
capillary walls are also one cell thick creating a short diffusion pathway for gases
Why is the percentage of oxygen in expired air less than inspired air?
oxygen is absorbed into the blood at the alveoli for aerobic respiration
Why is there a difference in the carbon dioxide concentration between inspired and expired air?
CO2 produced by aerobic respiration diffuses from the plasma into the alveoli to be exhaled
Why does the percentage of nitrogen hardly change inspired and expired air?
nitrogen is neither absorbed or taken out of the blood, not needed
Why is expired air saturated with water?
alveoli are permanently lined with moisture, evaporates from them and is exhaled
What is surfactant and what is its function?
an “anti-sticking” mixture
prevents the alveoli collapsing during exhalation by reducing surface tension when the pressure inside is low
also allows gases to dissolve
Describe the mechanism of inhalation in the lungs
external intercostal muscles contract, pulling the ribcage upwards & outwards
pulls out the pleural membranes, reducing pressure in the pleural cavity and the inner pleural membrane moves outwards
this pulls on the surfaces of the lungs and causes alveoli to expand (forced inspiration only)
diaphragm contracts, pulling it from a domed to a flattened shape
the combined effect is…
* volume of the thorax and lungs increase
* alveolar pressure is reduced to below atmospheric pressure
* air drawn into lungs, going down the pressure gradient
Describe the mechanism of exhalation in the lungs
external intercostal muscles relax and the ribcage falls under its own weight
diaphragm relaxes and gut pressure pushes back into its domed shape
the combined effect is…
* volume of the thorax and lungs decrease
* pressure is increased
* air is forced out
Describe the mechanism of forced exhalation in the lungs
internal intercostal muscles contract, pulling the ribcage down and in
abdominal muscle contracts pushing the diaphragm upwards
the combined effect is…
* volume of the thorax and lungs decrease
* pressure is increased
* air is forced out
How do the lungs stay ventilated?
negative pressure breathing and the movement of ribcage and diaphragm
lung is surrounded by the pleural membranes and the pleural cavity where the fluid lubricates movement and acts as a shock absorber
pleural membranes ensure the thorax is airtight, as changes in the volume of the thorax must be converted to pressure changes in the lung or ventilation wouldn’t occur
Give an example of external gills
tadpoles (larval form of frogs)
highly branched
short diffusion path
vascularised (provide tissue with blood vessels)
movement provides water current
How have insects adapted to live in arid habitats (terrestrial organisms)?
with all terrestrial organisms water evaporates from their body surface and risk dehydration
insects reduce water loss with a waterproof layer covering the body surface
exoskeleton made of chitin is impermeable and comprises a thin waxy layer over a thicker
layer of chitin and protein
Describe the gas exchange system in insects
the tracheal system
paired holes called spiracles on segments of the thorax and abdomen
they allow air to enter the system of chitin lined tubes called tracheae which branch into smaller tubes called tracheoles
spiracles can open and close so water loss is reduced (hairs covering spiracles help further with reducing water loss and stopping solid
particles entering)
the ends of tracheoles are fluid-filled and close to muscle fibres, oxygen dissolves in the fluid directly into muscle cells
no respiratory pigment needed / blood circulation
What is the difference in gas exchange for insects when they are resting vs when active?
Resting: rely on diffusion through spiracles, tracheae and tracheoles to take in oxygen and to remove carbon dioxide
Activity: movements of the abdomen ventilate the trachea
What is the limitation of the tracheal system?
it limits the size of the insect as diffusion can only occur over small distances
Why were insects much larger millions of years ago?
the oxygen concentration was so much higher than today
oxygen diffused more efficiently into the insect the cells so more energy is generated from respiration
this fuelled flight and growth
What are the parts in a cross section in a leaf?
cuticle
upper epidermis
palisade mesophyll
spongy mesophyll
vascular bundle: xylem, phloem and bundle sheath parenchyma
air spaces
lower epidermis
stomata
guard cells
Describe the pathway for gases into the leaf
gases diffuse through the stomata down a concentration gradient
then gases diffuse through the intracellular spaces between the mesophyll cells
gases dissolve in the film water covering the cells and in the cellulose and cell wall
then the gases diffuse into the cell
Describe the role of the guard cell and stomata
control water loss
- allows exchange of gases inside and outside leaf
Describe how the guard cells close the stomata (in the darkness)
potassium ions diffuse out of the guard cells, down the concentration gradient
malate is converted into starch
both these processes raise the water potential of the guard cells
water flows down its water potential gradient out of the cells
Turgor of the guard cell reduces, the guard cells change shape and the stomata closes
Describe how the guard cells open the stomata (in daylight)
potassium ions move into the guard cells by active transport
starch is converted into malate also lowering the water potential of guard cells
water flows into the guard cells down the water potential gradient by osmosis
turgor increases and the guard cell changes shape, opening stomata (inner wall is inelastic so they curve)
State which direction the gases travel in daylight
Photosynthesis is dominant and respiration is still happening
CO2 in and O2 out
the CO2 produced by respiration can be used in photosynthesis but more CO2 is needed so CO2 diffuses in
some O2 is used in respiration but most diffuses out
State which direction the gases travel in darkness
Respiration is dominant
O2 in and CO2 out
no photosynthesis
Name 3 structural features of fish gills which make them efficient gaseous exchange organs
Large surface area
Short diffusion pathway/thin
Good blood supply
Explain the advantages to the fish with counter-current flow compared to parallel flow
blood saturation reaches a higher % level of saturation of oxygen
uptake continues throughout lamella as water concentration of oxygen is always higher than blood
concentration gradient is maintained across whole surface as blood always meet water with a higher oxygen concentration
As the size of an organism increases which ratio decreases?
surface area:volume
What is the role of the intercostal muscles in the thorax of a mammal?
move ribs/enlarge thorax
Give 2 advantages to a mammal of having internal lungs
reduce heat (or water) loss
- protection by ribs
Suggest how the expanding and compressing of an insects abdomen helps ventilate the tracheal system?
acting as a pump to draw air in via the thoracic spiracles through the system and foces it out via abdominal spiracles
Explain why the long periods of closure of spiracles is important for an insects survival?
Reduces excessive water loss
What do plants rely on?
SImple diffusion so they have lots of adaptations suited to it
Describe and explain how terrestrial mammals are adapted for gaseous exchange in air
large number of alveoli to increase SA where gas exchange takes place
internal lungs to reduce water and heat loss
layer of moisture on alveoli for gases to dissolve in
thin walls reduce diffusion distance
blood supply maintains conc. between alveolar air and blood
haemoglobin transport oxygen
ventilation by diaphragm and rib cage enable stale air to be replaced by fresh air (ventilation mechanism)
Describe 3 properties that all respiratory surfaces must posses and explain why they must have them
- thin - small diffusion distance
- large surface area - large contact with air for gas exchange
- moist - allows gases to dissolve/go into solution
Give 2 reasons why gills don’t function effectively on land?
- unable to remain moist
- they clump together because of surface tension and collapse
What to say instead of ‘good blood supply’?
rich/dense network of capillaries
concentration gradient (mechanism)
State 2 advantages of using a tracheal system for gas exchange?
- No respiratory pigment (no haemoglobin required)
- Oxygen supplied directly to tissues (no transport system needed)
State 2 important structural features of alveoli
- large surface area
- One cell thick (thin)
(3. large numbers of capillaries)
Why have large, multicellular organisms evolved special surfaces for gaseous exchange?
Larger organisms need more O2 to meet metabolic needs
external surface becomes insufficient for gas exchange
diffusion distances are too large for O2 to reach cells furthest from surface
SA:V is too small
How are plants adapted for harvesting light energy?
Palisade cells are elongated cells
are arranged in densely-packed layers/layer
contain many chloroplast cells and can arrange themselves according to light intensity (or to avoid bleaching)
light can pass through spongy mesophyll
large leaf surface area
How are plants adapted for the inward diffusion of CO2?
Spaces between spongy mesophyll cells allows CO2 to diffuse to cells
Cells are moist so gases can dissolve
leaves are thin, short diffusion distance
thick waxy cuticle can reduce gaseous exchange
guard cells can change shape and reduce gaseous exchange
How are plants adapted for the provision of water?
guard cells and stomata control water loss from plant (open and close with photosynthetic activity)
guard cells change shape
leaves covered by a thick waxy cuticle prevents water loss
How are plants adapted for the removal of products of photosynthesis?
spaces between spongy mesophyll cells allows O2 to diffuse away
Describe the input and output of gases in plants during the day
During the day the rate of photosynthesis is faster than the rate of respiration. This means more oxygen is produced in photosynthesis than is used in respiration. So, overall the gas released is oxygen.
Describe the input and output of gases in plants during the night
At night photosynthesis does not happen, only respiration, so no oxygen is produced. So the gas that is released is carbon dioxide.
Describe how gases get into the leaf
Gases diffuse through the stomata down a concentration gradient. The gases inside the sub-stomatal chamber diffuse through intercellular spaces in the spongy mesophyll.
How does the cuticle being transparent help with photosynthesis?
Light can penetrate to the mesophyll
How does elongated palisade cells help with photosynthesis?
The leaf can accommodate a large number of them
How does palisade cells having lots of chloroplasts help with photosynthesis?
They can capture as much light energy as possible
How does the fact that chloroplasts can move within mesophyll cells help with photosynthesis?
They move into bets positions for maximum absorption of light
How do air spaces in the spongy mesophyll help with gas exchange?
They allow oxygen and carbon dioxide to diffuse between the stomata and the cells
How do air spaces in the spongy mesophyll help with photosynthesis?
Allows carbon dioxide to diffuse to photosynthesising cells
How do stomata pores help with gas exchange?
They allow gas exchange in and out of the leaf
Describe the Malate cycle
1) chloroplasts photosynthesise producing ATP
2) ATP gives energy for K+ ions to enter the guard cells by active transport from surrounding epidermal cells
3) Stored starch is converted into malate
4) K+ and malate lower the water potential, so water enters the guard cells by osmosis
5) Guard cells expand where walls are thinner. Thicker walls are opposite each other on the inside creating a pore
Reverse happens at night
What is the function of guard cells?
Guard cells control the opening and closing of the stomata
Why are stomata on the lower surface of the leaf?
Plants lose water by evaporation through their stomata in a process called transpiration. Sunlight on the upper surface of the leaf would increase evaporation and cause plants to wilt. So having them on the lower surface minimises water loss.
Why do stomata close and in what situations do they close?
Gas exchange and water lose both happen through Stomata and the plants must balance the conflicting needs of gas exchange and water loss, so they close :
1) At night when there is insufficient light for photosynthesis
2) In bright light as this is usually accompanied by intense heat which increases evaporation
3) If there is excessive water loss
