Chapter 6 Exchange Flashcards
What is surface area with respect to organisms?
The total area of the organism that is exposed to the external environment.
Explain one advantage of red blood cells being concave compared to being spherical.
There is a greater surface area for oxygen diffusion.
Describe 4 features of specialised exchange surfaces.
A large surface area to volume ratio.
Very thin, so shorter diffusion distance.
Movement of the environmental medium to maintain concentration gradient.
Effective internal transport system to ensure diffusion gradient is maintained.
How do you calculate the surface area of a cube?
Area of one side (length x length) x 6 sides
How do you calculate the volume of a cube?
Length x width x height
How do you calculate the ratio of surface area to volume?
Surface area / volume
How do you calculate the surface area of a sphere?
4 π r2
How do you calculate the volume of a sphere?
4/3 π r3
What is the basal metabolic rate?
The metabolic rate of an organism when at rest.
What activities require energy when an animal is at rest?
The functioning of vital organs such as the lungs, heart and brain.
Give 3 ways that the metabolic rate of an organism can be measured.
Rate of oxygen consumption
Rate of carbon dioxide production
Rate of heat production.
Describe 4 methods for determining metabolic rate.
Respirometers - the overall volume of gas is measured as carbon dioxide is removed from a closed system.
Oxygen probes - oxygen concentration is measured in a closed system.
Carbon dioxide probes - carbon dioxide concentration is measured in a closed system.
Calorimeters - energy produced is measured in a closed system.
What is the relationship between the mass of an organism and metabolic rate?
The greater the mass of the organism the higher the metabolic rate.
Why is the BMR per unit of body mass higher in smaller animals than larger animals?
Smaller animals have a greater surface area to volume ratio. This means they lose more heat. They therefore use up more energy to maintain their body temperature.
What is the equation for diffusion?
diffusion = (surface area x difference in concentration) / length of diffusion path
What method does Chlamydomonas use to exchange materials?
Chlamydomonas is a small single-celled organism so exchange of materials is efficient by diffusion.
How does mass transport of oxygen occur in insects?
Contraction of muscles through abdominal pumping enabling mass movements of air in and out.
How does oxygen reach the working muscles in an insect?
Through the tracheoles.
How do active, flying insects increase the air flow into the tracheal system?
- They close the spiracles
- They use muscles to create a pumping movement for ventilation.
What is the advantage of having water at the end of tracheoles?
In periods of high activity, anaerobic respiration will create lactate which will reduce the water potential of respiring cells causing them to take up water by osmosis. This loss of water from the tracheoles means gas is further inside them.
What are spiracles?
Openings in the exoskeleton of an insect with valves to allow air to enter the insect and flow into the tracheae.
What are the three ways gases move in and out of the tracheal system?
Along the diffusion gradient.
Mass transport.
Movement of the water at the end of the tracheoles.
Why are the insect’s spiracles generally closed?
To prevent water loss.
What are gills mainly made of?
Gill filaments.
What increases the surface area of the gills?
They have many gill filaments with many gill lamellae on them.
Describe how countercurrent flow allows for effective gaseous exchange.
Blood flows in the opposite direction to water. Ensures there is always a diffusion gradient between water and the gills allowing maximum uptake of oxygen.
Explain how parallel flow decreases gaseous exchange.
Oxygen can only be absorbed by diffusion at the start where oxygen concentration in the water is higher than in the blood. Equilibrium is quickly reached.
What are the two processes which require gases in a plant?
Photosynthesis and respiration.
How is a leaf adapted for gas exchange?
Many small pores (stomata) for a short diffusion pathway.
The spongy mesophyll layer has a network of air spaces.
During daytime, what is the exchange of gases in and out of the plant? Why?
Carbon dioxide in and oxygen out. Due to photosynthesis. Respiration doesn’t create enough carbon dioxide or use enough oxygen.
During night time, what is the exchange of gases in a plant? Why?
Carbon dioxide out and oxygen in. Respiration is still occuring, photosynthesis is not.
This is why they used to take plants out of patient’s rooms at night!
How are the gas exchange systems of plants similar to insects?
The cells using the gases are close to the external air.
Diffusion occurs in the gas phase, not water.
Pores for air to enter and leave.
Where are stomata mainly found?
Bottom side of the leaf to limit evaporation and transpiration.
What cells control the opening and closing of stomata?
Guard cells.
What causes guard cells to open?
Guard cells are open when they are turgid.
What is a disadvantage to having open stomata?
Excessive water loss.
What is the name of the plants that are well adapted to dry environments?
Xerophytes
How do insects reduce water loss? Explain one example.
Waterproof coverings, spiracles that can be opened and closed
What is the process known as when a plant loses water?
Transpiration
How does a thick cuticle reduce transpiration?
It is a waterproof barrier which increases diffusion distance.
How does rolled up leaves reduce transpiration?
The stomata end up on the inside part of the leaf. This means water vapour becomes trapped and the air is saturated with water. It has a high water potential removing the water potential gradient between inside and outside the leaf.
How does having hairy leaves reduce transpiration?
These trap moisture near to the leaf, increasing water potential in the air, and reducing the water potential gradient. Less water is therefore evaporated.
How does having stomata in pits or grooves reduce transpiration?
Water vapour is trapped in the pit/groove. This increases the water potential in the air, and reduces the water potential gradient. Less water is therefore evaporated.
How does having a reduced surface area to volume ratio in the leaves of the plant reduce transpiration? What is a drawback of this adaptation?
The smaller the surface area to volume ratio, the slower the rate of diffusion. This slows evaporation. But has to be balanced against surface area for photosynthesis.
What adaptations do cacti have to help them survive in the desert?
Their leaves have become spines to reduce water loss.
Photosynthesis happens in the stem.
The stem has a thick cuticle.
The stem has a large diameter and accordion shape so it can store water.
Deep tap roots.
Shallow roots
What are the adaptations that marram grass has to survive in a dry sandy environment?
Rolled leaves.
Deep grooves to protect the stomata.
Thick cuticle.
No stomata on exposed surfaces.
Inner surfaces have a large number of hairs.
What is the role of goblet cells and ciliated cells in the bronchi?
Goblet cells produce mucus to trap dirt/dust/pathogens. Ciliated cells waft the mucus back up the throat to be swallowed.
Where is maltase found?
It is part of the cell-surface membrane of the epithelial cells lining the ileum.
What is a monoglyceride?
A glycerol and single fatty acid
What does exopeptidase hydrolyse?
The terminal amino acids from a peptide. Creating amino acids and dipeptides.
Which of the peptidases are membrane bound? What does this mean?
Dipeptidases are membrane bound. They are found on the cell-surface membrane of the epithelial cells of the ileum.
What are the basic steps in the co-transport of glucose?
Na+ ions are actively transported out of the cell into the bloodstream.
This causes diffusion of Na+ ions into the cell from the ileum lumen as a concentration gradient is created.
Na+ diffuses through a carrier protein with a glucose molecule.
Glucose moves into the bloodstream via facilitated diffusion.
What other product of digestion is transported by co-transport?
Amino acids.
What is formed from the monoglycerides, bile salts and fatty acids?
Micelles.
What are the vesicles called which are formed from triglycerides, proteins and cholesterol for absorption into the blood?
Chylomicrons
How do chylomicrons take lipids out of the epithelial cells?
They leave through exocytosis. They move into lacteals, which are lymph vessels. These transport them to the bloodstream.
