3.3.2 Gas Exchange Flashcards
FISH:
Explain how the gills allow efficient gas exchange
- The lamellae provide a large surface area
- Thin epithelium so a short diffusion pathway
- Counter-current flow maintains the concentration gradient across whole length of lamellae
FISH:
Explain how the highly folded structures of the gill (lamellae) increase the efficiency of gas exchange
They increase the surface area over which diffusion can take place
FISH:
Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish.
Water and blood flow in opposite directions.
This maintains a concentration gradient across the gill (as there is always a higher concentration of oxygen in the water than blood)
Name the process by which carbon dioxide is removed from a single celled organism
Simple diffusion over the body surface
INSECTS:
Explain how the tracheal system limits the size of the insect
Because it relies on diffusion to bring oxygen to respiring tissues.
If insects were large it would take too long for oxygen to reach the tissues rapidly enough to supply the insects needs
INSECTS:
Give 2 explanations as to why the rate of water loss during gas exchange is very low in most insects.
- Insects have spiracles that can close to reduce water loss
* Insects have sunken spiracles that trap moist air
Describe and explain ways in which plants limit water loss.
- Plants have a waxy cuticle which prevents the evaporation of water;
- Plants have hairs on their surface that trap moist air reducing the water potential gradient
- Plants have sunken stomata which again traps moist air reducing the water potential gradient
- The stomata can close which reduces evaporation
How can you calculate pulmonary ventilation rate?
= tidal volume (dm3) x breathing rate (min-1)
LEAVES:
Explain why less water is lost by a plant when the air is humid.
Humidity reduces the difference in concentration of water between the plant and the air.
Reduced concentration gradient = less water loss
During an asthma attack, less oxygen diffuses into the blood from the alveoli. Explain why.
Asthma attacks narrow the airways, so not as much oxygen reaches the alveoli.
This means that there is a small concentration gradient (between blood and alveoli) so rate of diffusion is lower
What are xerophytes?
Plants that are adapted to living in areas where water is in short supply
Give examples of how xerophytes limit water loss
- Thick cuticle
- Waxy cuticle
- Rolled up leaves
- Hairy leaves
- Stomata in pits or grooves
- A reduced surface area to volume ratio
- Deep roots
- Sunken stomata
XEROPHYTES:
Explain how having rolled up leaves reduces water loss
- Traps a region of still air within the rolled leaf.
- The trapped region has a high water potential.
- As there is no water potential gradient between the inside and outside of the leaf there is no water loss
XEROPHYTES:
Explain how having hairy leaves reduces water loss
- Traps still, moist air next to the leaf surface.
- This reduces the water potential gradient between the inside and outside of the leaf so less water is lost.
XEROPHYTES:
Explain how having stomata in pits or grooves reduces water loss
- It traps still, moist air next to the leaf surface.
- This reduces the water potential gradient between the inside and outside of the leaf so less water is lost.
Explain why water is always lost from the gas exchange surfaces of terrestrial organisms
- Gas exchange surfaces are permeable.
- As there is a higher concentration of water molecules inside the animal than outside water will diffuse out.
Why does every cell inside an insect have a short diffusion distance?
They are only a short distance from the tracheae or the tracheoles
INSECTS:
Name the tiny pores on the body surface of insects
Spiracles
INSECTS:
For much of the time the spiracles are (open or closed)
Closed, to prevent water loss
INSECTS:
Periodically spiracles must open. Why?
To allow gas exchange
FISH:
What happens if blood and water flow in parallel?
- Diffusion of oxygen into the blood is less efficient - (only 50%)
- Equilibrium is reached as the conc. gradient cannot be maintained along the whole filament
XEROPHYTES:
How can a reduced SA : Vol ratio in leaves be achieved?
eg. Leaves are reduced to pine needles
LUNGS:
Starting with nose/mouth, list the structures that air passes through
Trachea - bronchi - bronchioles - alveoli
LUNGS:
What prevents the trachea from collapsing?
Rings of cartilage
LUNGS:
List the adaptations of the alveoli that make it ideal for gas exchange
Single layer of epithelium cells Stretch as breathe in Spring back as breathe out Huge SA Moist Rich blood supply
LUNGS:
What is the ‘tidal volume’?
The volume of air we breath in and out at rest (typically about 0.5dm3)
LUNGS:
Typically, what is the normal ventilation rate?
12-20 breaths per min
Describe the gross structure of the human gas exchange system
Trachea - Bronchi - Bronchioles - alveoli
describe the pathway of an oxygen molecule from alveolus to blood
crosses the single cell alveolar epithelium and then epithelium of the capillary
describe ONE feature of the alveolus that allows efficient gas exchange
ONE CELL thick therefore creating a SHORTER diffusion pathway
explain how the relationship between the direction of flow of water and of blood shown in a micrograph is useful to fish?
- maintains concentration gradient over whole length of gill
- more oxygen enters blood
- more aerobic respiration for swimming
expiration?
- external intercostal muscles and diaphragm relax
- ribcage moves down and in
- diaphragm curves
- thorax volume decreases
- pressure increases
- air forced out
inspiration?
- external intercostal muscles and diaphragm muscles contract
- ribcage moves up and out
- diaphragm flattens
- thorax volume increases
- pressure decreases
formula to find percentage saturation?
oxygenated haemoglobin / maximum saturation x 100
define partial pressure?
measure of concentration of a gas
the first molecule of oxygen to bind causes a change in the shape of the haemoglobin molecule.
this change of shape makes it easier for other oxygen molecules to bind to the haemoglobin molecule.
suggest one advantage of this change in the affinity of haemoglobin for oxygen?
ensures more intake of oxygen into lungs
the first molecule of oxygen to bind causes a change in the shape of the haemoglobin molecule.
this change of shape makes it easier for other oxygen molecules to bind to the haemoglobin molecule.
explain how a dissocation graph provides evidence for this?
- at low pp of oxygen little increase in saturation as oxygen increases
- then rapid rise as it gets easier for oxygen to bind
during exercise, the haemoglobin dissociation curve moves right.
explain the advantage of this difference?
- haemoglobin has LOWER affinity for oxygen
- therefore, more oxygen for respiration
explain the differences between the haemoglobin dissociation curve for rest and exercise?
- muscle contraction causes inc respiration
- inc CO2 production lowering pH
- inc heat released so inc temp
- inc oxygen consumption lowering pp of oxygen
the change to a dissociation curve is one of a number ways in which the total oxygen supplied to muscles is increased during exercise.
give TWO other ways in which total oxygen supplied to muscles during exercise is increased?
- increase in pulmonary ventilation
- increase in stroke volume
explain how the presence of gills adapts the damselfly to its way of life?
- damselfly has larger metabolic rate
- uses more oxygen
the scale for plotting body mass is a logarithmic scale. explain why a logarithmic scale was used to plot body mass?
large range of values - so can fit on graph
the zoologist measured oxygen uptake per gram of body mass.
explain why he measure uptake per gram of body mass?
- enables comparison
- as animals differ in size and mass
explain 2 ways in which the structure of fish gills is adapted for efficient gas exchange?
- many lamellae - large surface area
- thin surface - short diffusion distance
haemoglobins are chemically similar molecules found in many different species.
differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic relationships between species.
how?
- mutations change base sequence
- causing change in amino acid sequence
- mutations build up over time
- more mutations - more differences in amino acid sequence between distantly related species
- distantly related species have earlier common ancestor
