Gas Exchange Flashcards
What factors affect rate of diffusion?
Large Surface Area
Large Concentration Gradient
Short diffusion pathway
State Fick’s Law
Rate of Diffusion is proportional to Surface Area x Difference in concentration divided by length of diffusion pathway
Explain the adaptations of Gas exchange in a Single celled organism
The Exchange Surface is the whole body surface - cell surface membrane
Large Surface Area as the organism is small so it has a high SA:VOL ratio
Short diffusion pathway - gases only dissuade through membrane to enter cell
Conc gradient maintained - Oxygen used up in respiration which maintains low conc. Of Oxygen
What is the role of Spiracles in Insects?
They are the openings on either side of the body through which gases can enter and leave by diffusion
What are the function of the valves in Insects?
Used for opening and closing spiracles
What are tracheae in Insects?
A series of long tubes held open by rings of chitin through which air passes
What are tracheoles?
Smaller branched tubes with no chitin that air passes along ending in muscles of the insect
What is the function of Air Sacs
Used for pumping air in/out of the tracheal system in very active insects
Explain the adaptations of Gas exchange in insects
The exchange Surface is the tips of the tracheoles
Large Surface Area - Large No. Of highly branched Tracheoles
Short diffusion pathway - tracheoles have thin walls
Concentration Gradient - Oxygen used in aerobic respiration in body cells so lower conc. inside cell
How does Gas Exchange work in an insect
Oxygen diffuses through spiracle, down tracheae and tracheoles into body cells. Carbon Dioxide goes in opposite direction. Tips of tracheoles have water in which oxygen dissolves in from tips of tracheoles to body cells. This is enough for small insects
How does Gas exchange differ for large insects
VENTILATION MECHANISM
As oxygen needs to be supplied quicker, spiracles will close and air sacs are squeezed using muscles ina abdomen which pushes air further into tracheoles.
What happens when wing muscles are working hard?
Respiration will become partly anaerobic and lactate builds up (lactate = solute so affects water potential), lowers water potential in muscle cells, so water in tracheoles goes into muscle cells by osmosis. This reduces diffusion distance as oxygen diffuses directly from air into muscle cell without dissolving
Give 2 adaptations to reduce water loss in insects
Insects have an exoskeleton that is covered in a waxy waterproof cuticle
Spiracles can close using valves when insect is not active
Explain the Counter Current Principle
Blood + Water flow in opposite directions
Water with a high oxygen concentration will always flow next to blood with a relatively low oxygen concentration which maintains a concentration gradient and allows diffusion to occur across the whole length of the gill lamellae.
Explain the adaptations for gas exchange in Fish
The gas exchange Surface is the gill lamellae
Large Surface area due to large No. of highly branched gill filaments with many gill lamellae
Short diffusion pathway - very close at exchange surface. The lamella wall is a thin layer of squamous cells and the capillary wall is one cell thick
Concentration Gradient - Ventilation Mechanism continuously flowing oxygenated water over surface and remixing deoxygenated
Transport mechanism bringing deoxygenated blood and removing oxygenated blood.
Counter current maintain conc Gradient for diffusion to occur across whole gill lamellae
Explain Ventilation in Fish during Inspiration
Mouth opens. Floor of pharynx is pulled down, increasing the volume inside and decreases pressure. Water flows in
Explain Ventilation in Fish during Expiration
Mouth closed. Floor of pharynx pulled up. Decreases volume inside and increases pressure, squeezing water through the gills
What is the function for Palisade mesophyll
Main region for photosynthesis in upper parts of the plant
What is spongy mesophyll
They are many large spaces air spaces
Explain the adaptations for gas exchange in a plant
Exchange surface - surface of mesophyll cell
Large Surface area - many mesophyll cells in contact with many air spaces
Diff in conc. gradient - Gases used up as soon as they enter the cell in respiration or photosynthesis
Short diffusion pathway - Gases only diffuse through cell wall + membrane to enter cell
Explain the Structure of the Human Gas exchange System
Air enters the trachea which is supported by rings of cartilage. Stops the trachea collapsing during pressure changes. The trachea divides into a left + right bronchus which further divides into smaller tubes called bronchioles which at the end have alveoli (air sacs)
Explain the adaptations for gas exchange in Humans
Exchange Surface - The Alveolar Epithelium
Large Surface - Many Alveoli
Diff in Conc. Gradient - ventilation brings fresh air with high O2 conc. into alveoli and removes stale air with low O2 conc.
The continuous blood flow means there is a low conc. of O2 in the capillaries at the alveoli maintain a concentration gradient.
Short Diffusion Pathway - Alveolus wall is a single layer of squamous cells called Alveolar Epithelium. Capillary is the same but called the capillary endothelium and both lead to short diffusion pathway
What are the structures needed for ventilation in humans?
External + internal intercostal muscles between ribs and diaphragm. They work as an antagonistic pairs ( 1 contracts + other relaxes)
Explain the mechanism of breathing of Inspiration
- Muscles of diaphragm contract, diaphragm flattens
- External Intercostal Muscles (between ribs) contract, rib cage moves up and out.
- Volume of thoracic cavity increases
- Pressure decreases below atmospheric pressure
- Air sucked into lungs from high to low pressure
Explain the mechanism of breathing out Expiration
- Muscles of diaphragm relax, diaphragm returns to domed position
- Internal Intercostal Muscles (between ribs) contract, ribcage moves down and in
- Volume of thoracic activity decreases
- Pressure in thoracic activity increases above atmospheric pressure
- Air forced out from high to low pressure
Explain the rate of heat loss with small organisms
They have a large SA:VOL ratio. They lose a lot of heat to environment relative to size; high rate of heat loss. To compensate, the have high rates of respiration as heat is a by product of respiration
Explain rate of heat loss for Large organisms
They have a small SA:VOL ratio . They have a lower rate of heat loss so rates of respiration tend to be lower
How do insects prevent water loss?
- Open and close spiracles (prevent evaporation)- Covered in a waxy cuticle
How do the stomata help prevent water loss?
When cells have a lot of water they are turgid and when cells don’t they are flaccid. Flaccid guard cells close the stomata
In photosynthesis in plants, what gas is needed?
Carbon dioxide
What are the ways that insects control water loss?
- Waxy outer cuticle- They can close their spiracles- Water is trapped around the spiracles by hairs
