Topic 3A: Gas Exchange Flashcards
Suggest an explanation why mitochondria are mostly found close to the cell-surface membrane in large cells. [2]
- Large(r) cells have small(er) surface area to volume ratio;
- Diffusion pathway is long(er)
The body of a flatworm allows it to have efficient gas exchange between the water and the cells inside its body.
Explain how two features of the flatworm’s body allow efficient gas exchange. [2]
- (Thin/flat body so) short diffusion pathway;
- (Thin/flat body so) large surface area to volume ratio
Describe the relationship between size and surface area to volume ratio of organisms. [1]
- As size increases, ratio (of surface area to volume) decreases
Explain why oxygen uptake is a measure of metabolic rate in organisms. [1]
- (Oxygen used in) respiration, which is a metabolic process.
Name the structure through which gases enter and leave the body of an insect. [1]
- Spiracle
Name the small tubes that carry gases directly to and from the cells of an insect. [1]
- Tracheole/trachea
Explain the movement of oxygen into the gas exchange system of an insect when it is at rest. [3]
- Oxygen used in (aerobic) respiration;
- (So) oxygen (concentration) gradient (established);
- (So) oxygen diffuses in
Explain what causes the oxygen concentration in the tracheae to fall when the spiracles are closed. [2]
- (Oxygen is used in) respiration therefore diffuses (from tracheae) to tissues;
- Oxygen unable to enter organism.
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange. [3]
- Tracheoles have thin walls so short diffusion distance to cells;
- Highly branched so short diffusion distance to cells;
- Highly branched so large surface area (for gas exchange);
- Tracheae provide tubes full of air so fast diffusion (into insect tissues);
- Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface;
- Body can be moved (by muscles) to move air so maintains concentration gradient for oxygen.
Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill. [3]
- Water and blood flow in opposite directions;
- Maintains concentration gradient of oxygen;
- (Diffusion) along length of lamellae/filament/gill.
When first hatched, the young of some species of fish are less than 2mm long. Explain how these young fish get enough oxygen to their cells without having gills. [2]
- Diffusion across body surface;
- Short diffusion pathway / large SA:V ratio
Mackerel have thinner lamellae and more of them per mm of gill than toadfish.
Explain how mackerel are able to swim faster than toadfish. [3]
- Large numbers of lamellae so large SA;
- Lamellae thin so short (diffusion) pathway to blood;
- High rate of oxygen uptake for respiration.
Describe the features of fish gills that give them a large surface area. [2]
- (Gills have) lamellae on filaments;
- Lots of both.
The volume of water passing over gills increases if the temperature of the water increases. Suggest why. [1]
- Increased metabolism;
- Less oxygen (dissolved in water)
What is meant by the resolution of a ruler? [1]
The smallest change/interval that a ruler can detect.
What is the difference between a measurement and a reading? [1]
Measurement: 2 judgements
Reading: 1 judgement
Abdominal pumping increases the efficiency of gas exchange between the tracheloes and muscle tissue of an insect. Explain why. [2]
- More air enters;
- (So) maintains concentration gradient
The insect opens its spiracles at a lower frequency in very dry conditions.
Suggest one advantage of this. [1]
Less water lost
Suggest one reason why removal of water at the ends of tracheoles increases the rate of diffusion of oxygen between the tracheoles and muscle tissue. [1]
- Greater surface area exposed to air;
OR
Gases diffuse faster in air than through water
Describe how the structure of the insect gas exchange system:
- provides cells with sufficient oxygen
- limits water loss
Explain you answers. [5]
- Spiracles, tracheae, tracheoles;
- (Oxygen) diffuses through tracheae/tracheoles;
- Tracheoles are highly branched so large surface area (for exchange);
- Tracheole (walls) thin so short diffusion pathway;
- Tracheole walls are permeable to oxygen;
- Cuticle (impermeable) so reduces water loss;
- Spiracles have valves so reduces water loss;
- Hairs around spiracles reduce water loss.
Explain the typical adaptations of xerophytic plant leaves for reducing water loss? [5]
- Lower number of stomata per unit area so reduced evaporation;
- Stomata in pits so trap water vapour and water potential gradient decreases;
- Hairs so trap water vapour and water potential gradient decreases;
- Rolled leaves so trap water vapour and water potential gradient decreases;
- Thick waxy cuticle layer so increases diffusion pathway;
- Needle-shaped leaves so reduces surface area to volume ratio.
Describe how a student could use an eyepiece graticule to determine the mean diameter of stomata. [3]
- Measure (each stomata) using eyepiece graticule;
- Calibrate eyepiece graticule against stage micrometer;
- Take a number of measurements (to calibrate a mean).
Describe a method you could use to find the surface area of a leaf. [3]
- Draw around a leaf on graph paper;
- Count squares;
- Multiply by 2.
Suggest two reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration. [2]
- Water used for turgidity;
- Water used for photosynthesis;
- Water used in hydrolysis;
- Water produced during respiration.
What does standard deviation show? [2]
- Spread of data;
- Around the mean
Suggest three adaptations that leaves might have that enable the plant to grow well in dry conditions. [3]
- Low stomata density;
- Hairy leaves;
- Thick cuticle;
- Sunken stomata;
- Rolled leaves;
- Small leaves
Describe and explain the relationship between humidity and the rate of transpiration. [3]
- Increased humidity leads to decreased transpiration;
- High humidity means increased water potential;
- Reduces water potential gradient;
- Less evaporation.
Describe and explain the relationship between surface area to volume ratio of an organism and metabolic rate. [3]
- As surface area to volume ratio increases, metabolic rate increases;
- (A larger surface area to volume ratio will) lose more heat;
- (A higher rate of metabolism) replaces heat
Explain why a logarithmic scale is used when plotting body mass in a body mass against oxygen uptake graph. [1]
- Wide range of values (so can fit on graph)
Explain why, when plotting body mass against oxygen uptake, the oxygen uptake is measured per gram of body mass. [2]
- Enables comparison;
- As animals differ in size/mass
