3.1-2 Gas Exchange in Organisms Flashcards
What needs to be exchanged between an organism and its environment?
Respiratory gases - oxygen, carbon dioxide, water
Nutrients- vitamins, minerals, glucose
Excretory products - urea, faeces, fibre
Heat
What kind of exchanges can take place?
Passive - simple diffusion and osmosis
Active - facilitated diffusion and active transport
What happens to SA:V ratio when you increase the surface area?
As surface area increases
Volume will eventually become bigger than the surface area
Therefore SA:V ratio decreases
What is fick’s law?
Large SA x steep concentration gradient
Divided by
Short diffusion distance
What are some single cell organisms?
Bacteria
Fungi
Yeast
Algae
How does gas exchange take place in single celled organisms?
High SA:V ratio
1 cell thick therefore short diffusion distance
They use O2 for respiration constantly and water for chemical reactions (like protein synthesis) therefore steep concentration gradient as more O2 and water outside the cell
Describe the pathway of oxygen into insects?
Spiracle Trachea Tracheoles Capillaries Cells
How is steep concentration gradient achieved in gas exchange of insects?
Oxygen is constantly used by the cells for aerobic respiration therefore there is always more oxygen outside the cells
Abdominal pumping (rhythmic contractions) moves the gas in and out
How is large surface area achieved in gas exchange of insects?
Thin flat body surface
Leads to many spiracles available for oxygen to move in
How is short diffusion distance achieved in gas exchange of insects?
The tubes have a thin permeable membrane adjacent to individual cells for aerobic respiration
Mitochondria are rarely more than a few micrometers away from an air capillary
How does the trachea in insects being filled with water at the end help gas exchange?
In major activity anaerobic respiration takes place producing lactate = lower water potential
Therefore water moves into the cells and the volume of water in the trachioles decreases drawing air further in
This means the final stage of diffusion takes place as a gas and not a liquid making diffusion happen quicker
What is important about the trachea in insects?
They are supported by strengthened rings to prevent them form collapsing
How do insects limit water loss?
Small SA:V ratio - minimising area for water to be lost
Water proof covering on their whole body
Spiracles can be closed
How does water move into a fish?
Open mouth
= volume increases
∴ pressure decreases
Drawing water in because of the pressure concentration gradient
Water is forced over the gills for gas exchange
How does water move out of a fish?
Close mouth
= volume decreases
∴ pressure increases
Forcing water out because of the pressure concentration gradient
How is steep concentration gradient achieved in gas exchange of fish?
The blood in the gills acquiring oxygen moves around the body
∴ maintaining a steep concentration gradient
As always more oxygen in the water
How is large surface area achieved in gas exchange of fish?
The gill filaments and lamella
How is short diffusion distance achieved in gas exchange of fish?
1 cell thick to move through
What property do fish have?
A waterproof coating and therefore it is gas tight
What is the gill lamella?
Where the actual exchange takes place
A little disk perpendicularly placed at the end of the gill filaments that make up the gill rakers
How does the water move within the gills of a fish?
Countercurrent flow
The water moves in the opposite direction to the blood flow
A constant concentration gradient is maintained across the whole lamella
This allows for 80% of oxygen available to be absorbed into the blood
What would happen if the fish gills used a parallel flow?
You reach an equilibrium where no diffusion can take place as the concentration gradient becomes isotonic
Only 50% of oxygen available can be absorbed into the blood
What are the features of the cross section of a leaf? Top to bottom
Waxy cuticle
Upper epidermis
Palisade mesophyll
Spongey mesophyll (containing air spaces)
Lower epidermis- containing guard cells and stomata
What is the equation for photosynthesis?
6H20 + 6CO2 -> C6H12O6 + 6O2
What is different about gas exchange in plants?
They respire and photosynthesise therefore the products produced can be used as the reactants in the other
This can reduce gas exchange with the external medium (air)
However depends on the balance of the rates as most of the reactants are acquired from the external medium
How do stomata work in gas exchange?
They are surrounded by guard cells which can open and close the stomatal pore to control gas exchange
How is large surface area achieved in gas exchange of plants?
They are flat and thin due to air spaces in the spongey mesophyll
How is steep concentration gradient achieved in gas exchange of plants?
O2, water and CO2 are constantly being used up in respiration and photosynthesis
Through transpiration a constant flow of water is achieved through the plant with the stomata helping
How is short diffusion distance achieved in gas exchange of plants?
Between the stomata the gas travels through the numerous interconnecting air spaces and only has to go through 1 cell
Diffusion takes place in the gas phase which makes it faster than if it was in water
What is a xerophyte?
A plant that is adapted to live in areas where water is in short supply
What are the adaptations of xerophytic plants to limit water loss?
Thick waxy cuticle Hairs on its lower surface Leaf rolled up Stomata in pits Shallow roots close to the surface Reduced SA:V ratio of leaves
How does the thick waxy cuticle in xerophytes help reduce water loss?
Reduces water evaporation from its surface
How does hairs on the lower surface, leaf rolled up and stomata in pits help reduce water loss in xerophytes?
Traps the still moist air inside/next to the stomata
Which reduces the water potential gradient
How do the shallow roots in xerophytes help reduce water loss?
Allows more water to be absorbed
How does the reduced SA:V ratio of leaves in xerophytes help reduce water loss?
They are small and circular in cross as so not to compromise large SA for photosynthesis
Describe inspiration in mammals?
The external intercostal muscles and the diaphragm contract whilst the internal intercostal muscles relax
The ribcage moves up and out which increases the volume of the thorax and decreases the pressure inside the lungs
Because of the concentration gradient of pressure air is forced in
Describe expiration in mammals?
The external intercostal muscles and the diaphragm relax whilst the internal intercostal muscles contract (if expiration is forced)
The ribcage moves down and in which decreases the volume of the thorax and increases the pressure inside the lungs
Because of the concentration gradient of pressure air is forced out
What is the equation for pulmonary ventilation?
Pulmonary ventilation = tidal volume (dm3) X ventilation rate (min-1)
What is pulmonary ventilation?
Total volume of air moved into the lungs per minute
What is tidal volume?
Total volume of air taken in each breath
What is ventilation rate?
Number of breaths per min
How is short diffusion distance achieved in gas exchange of mammals?
Thin cell surface membrane
The capillaries are immediately next to the alveoli
The cell wall of the alveolus is 1 cell thick
How is large surface area achieved in gas exchange of mammals?
Lots of alveoli create a large SA in a small space
How is steep concentration gradient achieved in gas exchange of mammals?
The movement of the internal medium of blood is constant - O2 is moved away around the body
The movement of external medium of air is constant - due to changes in volume and pressure (always more oxygen in alveoli)
This keeps oxygen and carbon dioxide levels at a constant concentration gradient
What does the alveolus and capillary include?
Cell wall
Thin layer of moisture
Plasma
Red blood cells
Cell wall
O2 and CO2 diffusing between the two
What is the cause, symptoms and treatment of pulmonary tuberculosis? Risk factors?
Caused by a bacterium
Difficulty breathing
Chest pain
Coughing
Antibiotics
Smoker, HIV, Age
What is the effect on gas exchange in the lungs of pulmonary tuberculosis?
The white blood cells surrounding the bacteria prevent a path to the cell membrane of the alveoli so oxygen struggles to diffuse in
What is the cause, symptoms and treatment of pulmonary fibrosis? Risk factors?
Dust, mould - viral infection
Short of breath
Cough
Nutritional advice, oxygen therapy, lung transplant
Age, gender(men)
What is the effect on gas exchange in the lungs of pulmonary fibrosis?
A lot of scaring on the alveoli creating irregular/abnormal air spaces
Leading to less surface area for exchange
Fibrous connective tissue also builds up in the lungs reducing elasticity
What is the cause, symptoms and treatment of asthma? Risk factors?
Unknown
Breathlessness
Tight chest
Inhalers
Genetic, smoking
What is the effect on gas exchange in the lungs of asthma?
Bronchiole tubes become constricted due to muscle spasms therefore a lack of oxygen reaches the alveoli
What is the cause, symptoms and treatment of emphysema? Risk factors?
Smoking
Air-pollution
Coughing
Exhaustion
Bronchodilators
Inhaled steroids
SMOKING!
Air pollution, genetics, age
