Section 3 - Organisms exchange substances with their environment: 6. Exchange Flashcards
What is exchange
The transfer of materials between the internal and external environments of an organism
What is passive exchange
Exchange that requires no metabolic energy (diffusion/osmosis)
What is active exchange
Exchange that requires metabolic energy (active transport)
What are the main factors that effect the rate of diffusion
- SA available for diffusion
- Diffusion pathway
- Permeability of membrane
- Concentration gradient
- Temperature
What are the common features of specialised exchange surfaces
- Large SA:Vol ratio (whilst still minimising water loss)
- Shot diffusion pathway
- Selectively permeable membranes
- Ventilation of the internal and environmental mediums (to maintain a concentration gradient)
What is the SA:Vol ratio
The available surface area for exchange per unit of volume
How do you calculate the SA:Vol ratio
SA / Vol
What is the relationship between diffusion and SA, Concentration gradient and diffusion pathway
Diffusion ∝ (SA x Conc. gradient) / (diffusion pathway)
What is the relationship between SA and Vol
SA ∝ Vol^⅔
How does gas exchange occur in single-celled organisms
Small size means SA:Vol ratio is large enough for exchange to occur by diffusion
What is the gas exchange system of an insect
Tracheal system
What are the main features of the tracheal system
- Spiracles
- Tracheae
- Air sacs
- Tracheoles (containing tracheal fluid)
What is the structure and function of spiricles
Small holes in the exoskeleton of insects that allow gas to enter and exit for exchange to occur
What is the structure and function of the tracheae (in the tracheal system)
Network of internal tubes that make up part of the tracheal system, with one main trachea in each side of the insect’s body
What is the structure and function of the tracheoles
Small divisions of the trachea within the tracheal system, that carry and remove air to/from individual cells within the body of the insect
What is the structure and function of the air sacs within the tracheal system
Muscles in the abdomen can contract, reducing the volume of theses sacs and increasing the pressure to force air out, ventilation the system
What is the function of the tracheole fluid
- During intense exercise, anaerobic respiration takes place, releasing Lactic acid
- This lactic acid is water soluble and reduces the water potential within the cells
- The tracheole fluid has a high water potential, so is then taken into the cells by osmosis
- This decreases the pressure within the tracheoles, so air is drawn in through the system, giving a greater oxygen supply, which is needed due to the intense exercise
What is the structure of the gas exchange system of a fish
Under the operculum, there are many gill arches that the water flows past, allowing exchange of oxygen and carbon dioxide to take place
What are the main features of a gill arch
- Gill bar
- Gill filaments
- Gill lamellae
- Gill rakers
What is the structure and function of the gill bar
A stiff bar of cartilage that the gill filaments attach to, supporting the structure of the gill arch
What is the structure and function of the gill filaments
Long projections off of the gill bar, increasing the surface area for gas exchange
What is the structure and function of the gill lamellea
Small disc like projections along and perpendicular to the gill filaments, with a large supply of blood flowing through them, to increase the surface area for diffusion
What is the structure and function of the gill rakers
Small, finger like protrusions and hairs along the gill bar to catch and trap any debris that may damage the structure of the gills are reduce the SA for exchange
What is the counter current flow principle
In the gills, the blood and the water flow in opposite directions, to allow a concentration gradient to be maintained the whole way across, as the blood with the highest oxygen concentration meets the water with the most oxygen concentration, and vice versa