2.2 Adaptations for Gas Exchange Flashcards
1
Q
Diffusion of a substance is
A
Directly proportional to their surface area
2
Q
What does volume of nutrients depend on?
A
Volume (bulk), activity levels and metabolic rate
3
Q
What makes a good gas exchange surface?
A
- large SA (often highly folded) as more space for molecules involved
- thin barrier (one cell thick) to reduce diffusion distance
- fresh supply and removal of molecules to maintain steep diffusion gradient
- moist
4
Q
Explain flatworms in terms of gas exchange
A
- flat so larger surface area than spherical organism of the same volume
- very short diffusion path
5
Q
Explain earthworms in terms of gas exchange
A
- cylindrical so small SA:V ratio
- skin is a respiratory surface so kept moist by mucus secretion
- low O2 requirement as slow moving and low metabolic rate
- haemoglobin helps to maintain diffusion gradient at surface
6
Q
Explain multicellular organisms in terms of gas exchange
A
- higher metabolic rate so need to deliver more O2 to cells
- increased size and specialisation of cells so tissues and organs more interdependent
- steep conc gradient
- respiratory surfaces v thin & protected as inside organism
7
Q
Define ventilation
A
Bringing gases to or from a gas exchange surface
8
Q
Define metabolic rate
A
The rate of energy expenditure of the body
—> respiration, O2, activity
9
Q
Why is metabolic rate greater in mammals and birds than fish?
A
Feathers and fur lead to higher constant body temp
10
Q
2 ways a diffusion gradient is maintained in multicellular organisms
A
- blood flow
- respiratory pigments ie haemoglobin
11
Q
Inspiration in fish
A
- mouth open, operculum closed, floor of mouth down, volume in mouth increase, pressure in mouth decrease, water movement in as external pressure higher
12
Q
Expiration in fish
A
- mouth closed, operculum open, floor of mouth up, volume decrease and pressure increase, water movement out as internal pressure higher
13
Q
What are pleural membranes?
A
Thin, fluid filled membrane that surrounds the outer surface of the lungs and lines the inner wall of the chest cavity
14
Q
Inhalation in mammals
A
- diaphragm flatten and intercostal muscles contract, rib position fill up and move out, thorax volume increase and pressure in thorax decrease, air moves in
15
Q
Exhalation in mammals
A
- diaphragm relax and dome, intercostal muscles relax, ribs empty and move in, thorax volume decrease and pressure increase, air move out
16
Q
What vessels take blood to and from heart?
A
Pulmonary artery = blood to lungs
Pulmonary veins = blood to heart and away from lungs
17
Q
Explain gas exchange in cartilaginous fish
A
- parallel flow of blood and water
—> oxygen diffuse from concentrated to less concentrated areas but can only continue until the water and blood O2 concentrations are equal as concentration gradient is not maintained past this point - does not occur continuously across whole gill lamella
18
Q
Explain gill structure in bony fish
A
- each gill supported by a gill arch
- thin projections called gill filaments on each arch
- gill lamellae for gas exchange
—> stick together when not in water hence fish die on ground
19
Q
Explain gas exchange in bony fish
A
- water move from mouth cavity to opercular cavity and into gill pouches where it flows between gill lamellae
- counter current flow enables conc gradient to be maintained and therefore diffusion along entire length of lamellae
- gills extract 80% of available oxygen
20
Q
Why is parallel flow less efficient than counter current?
A
- O2 only diffused to equilibria
- does not occur across whole gill lamellae
—> therefore less O2 uptake
21
Q
Suggest why gill lamellae would not be efficient on land
A
- dry out so oxygen cannot dissolve so fish suffocate
- stick together which decreases SA therefore less gas exchange
22
Q
Explain efficient adaptations for gas exchange in mammalian respiratory system
A
- many alveoli which are highly folded to increase SA therefore gas exchange efficiency
- one cell thick - short diffusion path
- capillaries to maintain rich blood supply which maintains concentration gradient for diffusion
23
Q
Why do mammals need a complex ventilation system?
A
- high metabolic rate
- ventilation maintains steep concentration gradient so more O2 can be diffused
24
Q
Give 2 advantages of humans having internal gas exchange surfaces
A
Reduce heat and water loss
25
Stage one medical use of artificial surfactant and explain why it would be needed
- premature babies
- lowers surface tension of fluid in the alveoli to prevent alveoli from collapsing
26
Function of gill rakers
Filter large molecules and sediment
27
What part of the respiratory system becomes inflamed during an asthma attack?
Bronchioles
28
What part of the respiratory system contains a surfactant to reduce surface tension?
Alveoli
29
In the trachea, what is the function of the ciliated epithelial layer?
Beat and move mucus/bacteria upward
30
In trachea, what is the function of the layer of cartilage?
Prevent trachea closing during inspiration
31
In the trachea, why is the cartilage not in a complete ring?
To enable oesophagus to expand when eating
32
How do insects reduce water loss?
A waterproof layer covering body surface
- exoskeleton has thin waxy layer over chitin
33
Explain gas exchange in insects
- occurs through paired holes called spiracles running along the side of the body
- spiracles lead into a system of branched, chitin lined air tubes called tracheae, which branch to smaller tubes called tracheoles
- spiracles able to open and close for gas exchange and to reduce water loss
- hair on spiracles present water loss and prevent solid particles getting in
34
One advantage and one disadvantage of the tracheal system
A: oxygen delivered directly to cells
D: size/shape limitation
35
Why does amoeba not need a specific aliased gas exchange system?
- diffusion of gas dp to surface area
- very large SA:V ratio
- gets sufficient oxygen through simple diffusion
36
How do mammals maintain conc gradient?
Blood flow and ventilation
37
Explain the difference in size of bird and mammalian red blood cells
- mammalian evolved when O2 levels lower
- biconcave shape increase SA for O2 diffusion
- no nucleus so carry more haemoglobin
- small so short diffusion distance
- high SA:V ratio
38
Explain the causes of the pressure and volume changes shown during inspiration
- expanding rib cage lowers pressure in pleural cavity
- inner pleural membrane pulls on lungs which increases lung volume which decreases pressure in lungs
- below atmospheric pressure so air moves in
39
Explain how the outward movement of the rib cage causes changes in the pleural and alveolar pressures during inspiration
- intercostal muscles contract and expand the rib cage which pulls out pleural membranes
- pleural pressure reduced and inner pleural membranes expand alveoli which decreases alveoli pressure and so air moves in
40
What are stomata?
Pores on lower leaf surface, and other areal parts of a plant, bounded by two guard cells through which gases and water vapour diffuse
41
How do the stoma open?
- chloroplasts in the guard cells photosynthesise, producing ATP
- ATP provides energy for active transport of potassium ions into guard cells from surrounding epidermal cells
- stored starch converted to a late ions
- the K+ and a late ions lower the water potential in the guard cells making it more negative so water enters cells by osmosis
- the cells of guard cells are thinner in some places than others so expand as thy absorb water, but expand less in areas where cell wall thick
- pore appears between the thicker areas, which is the stoma
42
Why do the guard cells form a banana like shape?
Radial cellulose fibres
43
When and why do stomata close?
- at night to prevent water loss when there is insufficient light for photosynthesis
- in very bright light as this is generally accompanied by intense heat which old increase evaporation
- if there is excessive water loss
