Exchange And Transpor Flashcards
What surface area to volume ratio do single cell organisms have?
a high SA:V ratio which allows for the exchange of substances to occur via simple diffusion
The large surface area allows for maximum absorption of nutrients and gases and secretion of waste products
The small volume means the diffusion distance to all organelles is short
As organisms increase in size, what happens to their surface area to volume ratio?
their SA:V ratio decreases
There is less surface area for the absorption of nutrients and gases and secretion of waste products
The greater volume results in a longer diffusion distance to the cells and tissues of the organism
Why is oxygen required for specialised systems for gas exchange?
Supply of Oxygen:
Organisms require ATP in order to carry out the biochemical processes required for survival. The majority of ATP is produced through aerobic respiration which requires oxygen
Why is the removal of carbon dioxide needed for specialised systems gas exchange
Removal of Carbon Dioxide:
Carbon dioxide is a toxic waste product of aerobic respiration
If it accumulates in cells/tissues it alters the pH
Why is diffusion a viable transport mechanism for single-celled organisms but not for larger multicellular organisms
The time taken for oxygen to diffuse from the cell-surface membrane to the tissues would be too long
Body mass affecting metabolic rate
Experiments conducted by scientists have shown that the greater the mass of an organism, the higher the metabolic rate
Therefore, a single rhino consumes more oxygen within a given period of time compared to a single mouse
SA:V Ratio affecting metabolism
Although metabolic rate increases with body mass the BMR per unit of body mass is higher in smaller animals than in larger animals
Smaller animals have a greater SA:V ratio so they lose more heat, meaning they have to use up more energy to maintain their body temperature
What is metabolic rate
The metabolic rate of an organism is the amount of energy expended by that organism within a given period of time
What is the basal metabolic rate
The basal metabolic rate (BMR) is the metabolic rate of an organism when at rest. The BMR is significantly lower than when an organism is actively moving
How can the metabolic rate of an organism be measured
The metabolic rate of an organism can be measured/estimate using different methods:
Oxygen consumption
Carbon dioxide production
Heat production
What features that organism surfaces have that make them effective exchange surfaces have
A large surface area
Short diffusion distance
Concentration gradient (maintained)
What does all trachael insect systems contain
All insects possess a rigid exoskeleton with a waxy coating that is impermeable to gases
Insects have evolved a breathing system that delivers oxygen directly to all the organs and tissues of their bodies
What is a spiracle
A spiracle is an round valve like openings in the exoskeleton running along length of abdomen
It allows air to enter the insect and flow into the system of tracheae. The trachea attatch to these openings.
Most of the time, the spiracle is closed to reduce water loss
What are the trachea
Tracheae are a network of internal tubes within the insect breathing system which lead to tracheoles (narrower tubes)
The walls of trachaea are reinforced with spirals of chitin. This prevents the trachaea from collapsing when the insect moves.
The tracheae walls have reinforcement that keeps them open as the air pressure inside them fluctuates
Where do the tracheoles go?
A large number of tracheoles run between cells and into the muscle fibres - the site of gas exchange
For smaller insects, this system provides sufficient oxygen via diffusion
How is a concentration gradient created in insects?
A concentration gradient is created as oxygen is used by respiring tissues allowing more to move in through the spiracles by diffusion
Carbon dioxide produced by the respiring tissues moves out through the spiracles down a concentration gradient
How do insects create a mass flow of air into the tracheal system
flying insects need a more rapid supply/intake of oxygen.
They create a mass flow of air into the tracheal system by:
Closing the spiracles
Using muscles to create a pumping movement for ventilation
What happens during flight in an insect
During flight, the production of lactate in the respiring muscles, lowers the water potential of muscle cells
water found at the narrow ends of the tracheoles is then drawn into the respiring muscle by osmosis
This allows gases to diffuse across more quickly
Structure of fish gills in bony fish
Series of gills on each side of the head
Each gill arch is attached to two stacks of filaments
On the surface of each filament, there are rows of lamellae
The lamellae surface consists of a single layer of flattened cells that cover a vast network of capillaries
Explain the mechanism of the structure of bony fish
The capillary system within the lamellae ensures that the blood flow is in the opposite direction to the flow of water - it is a counter-current system
The counter-current system ensures the concentration gradient is maintained along the whole length of the capillary
The water with the lowest oxygen concentration is found adjacent to the most deoxygenated blood
Structure of a leaf:
Waterproof cuticle
Upper epidermis - layer of tightly packed cells
Palisade mesophyll layer - layer of elongated cells containing chloroplasts
Spongy mesophyll layer - layer of cells that contains an extensive network of air spaces
Stomata - pores (usually) on the underside of the leaf which allow air to enter
Guard cells - pairs of cells that control the opening and closing of the stomata
Lower epidermis - layer of tightly packed cells
Mechanism of the structure of the leaf
When the guard cells are turgid (full of water) the stoma remains open allowing air to enter the leaf
The air spaces within the spongy mesophyll layer allows carbon dioxide to rapidly diffuse into cells
The carbon dioxide is quickly used up in photosynthesis by cells containing chloroplasts - maintaining the concentration gradient
No active ventilation is required as the thinness of the plant tissues and the presence of stomata helps to create a short diffusion pathway
Why is the exchange of gases from the atmosphere essential for the survival of organisms
Oxygen is required for respiration
Carbon dioxide is required for photosynthesis
What range of vital functions within organisms does water have
It is a solvent that facilitates the transport of essential nutrients
Extreme water loss can lead to death
It is a solvent that facilitates the transport of essential nutrients
Extreme water loss can lead to death