Section 3 - Chapter 6: Exchange - old Flashcards
1
Q
What are some examples of things that need to be exchanged between environments
A
- Respiratory gases (oxygen, carbon dioxide)
- Nutrients(Glucose, fatty acids, amino acids, vitamins, minerals
- Excretory Products(urea, and carbon dioxide)
- Heat
2
Q
What does an organisms surface area to volume ratio affect
A
- Surface area: volume ratio - how quickly substances are exchanged. The exchange surface of the organism must be large compared with its volume
- As volume increases - simple diffusion of substances across the outer surface can only meet the needs of relatively inactive organisms - takes too long if diffusion alone
3
Q
What features have organisms evolved more of
A
- A flattened shape so no cell is far from surface
- Specialised exchange surface with large areas to increase the surface area to volume ratio
4
Q
What are some features of exchange surfaces
A
- A large surface area to relative to the volume of the organism which increases the rate of exchange
- Very thin so that the diffusionn distance is short and materials can exchange rapidly
- Selectively permeable to allow selected materials across
- Moist surface
- Movement of environmental medium, maintain a steep diffusion gradient
- A transport system to ensure the movement of the internal medium, for example blood
5
Q
How is gas exchange in single-celled organisms
A
- Single-celled organisms are small and therefore have a large surface area to volume ratio.
- Oxygen is absorbed by diffusion across their body surface, which is covered only by a cell-surface membrane.
6
Q
What are Ficks law
A
- Ficks law shows the relationship between the variables that affect diffusion
- Rate of Diffusion = surface area x difference in concentration / length of diffusion path
7
Q
What does terrestrial mean
A
They live on land
8
Q
What have insects adapted
A
- Insects have evolved mechanisms to conserve water.
- The increase in surface area required for gas exchange conflicts with conserving water because water will evaporate from it
9
Q
How do insects exchange gas
A
- Insects have evolved a network of tubes called tracheae. They are supported by strengthened rings to prevent them from collapsing.
- The tracheae is divided into smaller dead end tubes called tracheoles.
- These extend into body tissue throughout so there is a short diffusion pathway from tracheole to any body cell
10
Q
Respiratory gases move in and out of the tracheal system in 3 ways (2 of the ways)
A
- Along a diffusion gradient
- When cells are respiring (oxygen used) so concentration towards ends of tracheoles falls. Oxygen enters spiracles (high) moves in. Cells are respiring and using CO2. Conc near cells is high. Near spiracles its low. Co2 moves away from cells
- Mass Transport
- The contraction of muscles squeeze trachea enabling mass movement of air in and out. Speeds up exchange
11
Q
Respiratory gases move in and out of the tracheal system in 3 ways (1 of them)
A
- Ends of tracheoles are filled with water
- During active periods, muscle cells respire anaerobically.
- Produces lactate - (soluble) lowers water potential of muscle cells.
- Water moves into cells from tracheoles by osmosis. The water in the ends of the tracheoles decrease in volume and in doing so draws air further in.
- This means the final diffusion pathway is in gas rather than liquid - rapid. Increases rate of air in but causes water evaporation.
12
Q
How does the gas enter and leave in insects
A
- Through tiny pores called spiracles.
- The spiracles may be opened and closed by a valve
- When spiracle = open water vapour can evaporate from the insect. Most time = closed to prevent water loss. Periodically they open to allow gas exchange
- Insects need to be small as they rely on diffusion which needs a short diffusion pathway
13
Q
What features do fish have
A
- Fish have a waterproof therefore a gas-tight, outer covering.
- Relatively large they have a small surface area to volume ratio
- Their body surface is not adequate to supply and remove respiratory gases. Like insects evolved specialised internal gas exchange surface - gills
14
Q
What is the structure of gills
A
- The gills are located within body of fish behind head
- Made of gill filaments - they are stacked up in a pile.
- At right angles to filaments are gill lamellae, increase surface area of gills.
- Water enters mouth - and forced over gills and out through opening on each side of body
- Flow of water and blood over gill lamellae are in opposite directions - countercurrent flow
15
Q
What is the countercurrent exchange principle
A
- Main feature is that blood and water flow over the gill in opposite directions.
- This means that blood always passes water with higher oxygen concentration (oxygen moves out of water into blood)
- This maintains a concentration gradient throughout the length of the gill
- Blood leaves lamella with a high oxygen conc
16
Q
Why does gas exchange need to take place when plants both photosynthesize and respire
A
- When photosynthesis is not occuring, in dark. Oxygen needed for respiration is obtainted from air. The carbon dioxide produced during respiration cant be used (as its dark) and diffuses out of the plant.
17
Q
Why is gas exchange in plants similar to gas exchange in insects
A
- No living cell is far from external air and therefore a source of oxygen and carbon dioxide
- Diffusion takes place in the gas phase (air) which makes it more rapid than if it were in water.
18
Q
What are some features of the plant exchange system
A
- Air spaces inside a leaf have a very large surface area compared with the volume of living tissue.
- There is no specific transport system for gases, which simply move in through the plant by diffusion
- Most gaseous exchange occurs in the leaves
19
Q
What adaptations do leaves have for rapid diffusion
A
- Many small pores, called stomata, and so no cell is far from stoma and therefore the diffusion pathway is short
- Numerous interconnecting air spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells
- Large surface area of mesophyll cells for rapid diffusion.
20
Q
What are the stomata
A
- Stomata are minute pores that occur mainly not exclusively on the leaves especially underside.
- Each stoma is surrounded by guard cells - these open and close the pore
- They can control rate of gaseous exchange.
- Plants have evolved to balance conflicting needs of gas exchange and control of water loss. They do this by closing stomata at times when water loss would be excessive.
21
Q
What features has an insect evolved to reduce water loss
A
- Problem for terrestrial organisms is that water easily evaporates from their surface
- Small surface area to volume ratio - minimise the area in whih water is lost
- Waterproof coverings - rigid outer skeleton of chitin is covered with a waterproof cuticle
- Spiracles - openings of the tracheae at the body surface. Closed to reduce water loss
- These feature mean insects cant use their body surface to diffuse gases. Instead have an internal network of tubes called tracheae.
35
Q
What changes the pressure inside the lungs
A
- The movement of 2 muscle types:
- The diaphragm - sheet of muscle that separates the thorax from the abdomen
- The intercostal muscles which lie between ribs
- The internal intercostal muscles - contraction leads to expiration
- The external intercostal muscles - contraction leads to inspiration
36
Q
What is Inspiration
A
- Breathing in is an active process (it uses energy) and occurs as follows
- The external intercostal muscles contract while internal intercostal muscles relax
- Ribs are pulled inwards and outwards, increasing volume of thorax
- The diaphragm muscles contract, causing it to flatten, which also increaes volume of thorax
- The increased volume of the thorax results in reduction of pressure in the lungs
- Atmospheric pressure is now greater than pulmonary pressure and air is forced into lungs.
37
Q
What is Expiration
A
- Breathing out is a largely passive process (does not require much energy)
- The internal intercostal muscles contract, external intercostal muscles relax
- The ribs move downwards and inwards - decreasing volume of thorax
- The diaphragm relax and is pushed again by the contents of the abdomen that were compressed during inspiration. Volume of thorax is decreased
- Decreased volume of thorax increases pressure in lungs
- The pulmonary pressure is now greater than the amosphere - air is forced out of lungs
