Module 3 - Gas Exchange Flashcards
3 marks
Describe and explain the relationship between surface area to volume ratio of the human body and metabolic rate.
- As SA:V increases, metabolic rate increases
- A larger SA:V will lose more heat
- A higher rate of respiration/ metabolism, releases heat
4 marks
Decsribe fish ventillation
- Mouth opens, opercular valve shuts
- Floor of mouth lowered
- Water enters due to decreased pressure, increased volume
- Mouth closed, opercular valave opens
- Floor of mouth raised= increased pressure, decreased volume
- Increased pressure pushes water over gills
4 marks
Describe expiration
- Contraction of internal intercostal muscles
- Relaxation of diaphragm muscles and external intercostal muscles
- Causes decrease in thoracic cavity
- Air pushed down pressure gradient
How does asthma affect the mean volume of air breathed out
- Muscle walls of bronchi/bronchioles contract;
- Walls of bronchi/bronchioles secrete more mucus;
- Diameter of airways reduced;
- (Therefore) flow of air reduced;
3 marks
Describe how gas exchange occurs in single-celled organisms and explain why this method cannot be used by large, multicellular organisms.
- Diffusion (across the cell surface membrane);
- Large organisms have small(er) sa : vol ratio
- Diffusion pathway would be too long
3 marks
Describe and explain the importance of three adaptation of the gas exchange surface in the tracheal system of an insect
- Tracheole (wall) thin/one cell thick
- (So) rapid diffusion (into cells)
- Tracheoles supply tissues
- (So) diffusion direct into cells
- Tracheoles are highly branched
- (So) large surface area for (rapid) diffusion
4 marks
Describe the pathway taken by an O2 molecule from the atmosphere to the respiring tissues in an insect
- Via spiracle
- Down trachea
- To tracheoles
- Diffuses into respiring tissue
- Down concentration gradient
6 marks
Describe how the structure of the insect gas exchange system:
* provides cells with sufficient oxygen
* limits water loss.
- Spiracles, tracheae, tracheoles;
- Spiracles allow diffusion of oxygen
- Tracheoles are highly branched so large surface area for exchange
- Tracheole walls thin so short diffusion distance to cells
- Tracheole walls are permeable to oxygen/air
- Exoskeleton impermeable- covered with waterproof waxy cuticle so reduce water loss
- Spiracles can close so less water loss
- Hairs around spiracles reduce water loss
5 marks
Describe how humans breathe in and out
Breathing in
1. Diaphragm muscles contract and diaphragm flattens
2. External intercostal muscles contract and ribcage pulled up
3. Increase in volume of thoraic cavity and pressure decreases
Breathing out
4. Diaphragm muscles relaxes and diaphragm becomes curved
5. External intercostal muscles relax and ribcage moves down
6. Decrease in volume of thoraic cavity and increase in pressure –> air pushed down pressure gradient
3 marks
Explain three ways in which an insect’s tracheal system is adapted for efficient gas
exchange.
- Tracheoles have thin walls so short diffusion distance to cells
- Highly branched/ large no. of tracheoles so short diffusion distance to cells
- Highly branched/ large no. of tracheoles so large SA
- Tracheae provide tubes full of air so fast diffusion into insect tissues
- Fluid in the end of tracheoles that move out into tissues during exercise so larer SA
- Body can be moved by muscles to more air so maintains conc gradient for O2/CO2
2 marks
The damselfly larva is a carnivore that actively hunts prey. It has gills to obtain oxygen from water. Explain how the presence of gills adapts the damselfly to its way of life
- Damselfly has a higher metabolic/ respiratory rate
- So uses more oxygen
3 marks
Particulate matter is solid particles and liquid particles suspended in air. Polluted air contains more particulate matter than clean air. A high concentration of particulate matter results in the death of some alveolar epithelium cells. If alveolar epithelium cells die inside the human body they are replaced by non-specialised, thickened tissue.
Explain why death of alveolar epithelium cells reduces gas exchange in human lungs.
- Reduced surface area
- Increased distance for diffusion
- Reduced rate of gas exchange
3 marks
Describe how we breathe in.
- Diaphragm contracts pulling diaphragm down
- External intercostal muscles contracts pulling/moving ribs upwards/outwards
- (Causes) volume increase and pressure decrease in thoracic cavity
Describe how O2 in the air reached capillaries surrounding alveoli in the lung. Details of breathing are not required
- Trachea, bronchi, bronchioles
- Down pressure gradient
- Down diffusion gradient
- Across alveolar epithelium
- Across capillary endothelium
6 marks
Explain how the ventilation mechanism of a fish and the structure of its gills result in the efficient uptake of oxygen from water.
- filaments / lamellae: large SA
- gill plates or secondary lamellae
- large number of capillaries: to remove oxygen / to maintain a gradient
- thin epithelium: short diffusion distance
- pressure changes: to bring in more water / to maintain gradient
- countercurrent flow: diffusion along whole length –> concentration gradient maintained as water and blood flow in opposite directions
4 marks
Describe and explain how fish maintain a flow of water over their gills.
- mouth opens, opercular valve shuts
- floor of mouth lowered
- water enters due to decreased pressure / increased volume
- mouth closes, opercular valve opens
- floor raised results in increased pressure / decreased volume
- increased pressure forces water over gills
6 marks
Describe and explain how the structure of the mammalian breathing system enables efficient uptake of oxygen into the blood.
- alveoli provide a large surface area
- walls of alveoli thin to provide a short diffusion pathway
- walls of capillary thin- provides a short diffusion pathway
- walls of capillaries / alveoli have flattened cells
- cell membrane permeable to gases
- many blood capillaries provide a large surface area
- diaphragm muscles maintain a concentration gradient
- wide trachea / branching of bronchi / bronchioles for efficient flow of air
- cartilage rings keep airways open
1 mark
The ends of tracheoles connect directly with the insect’s muscle tissue and are filled with
water. When flying, water is absorbed into the muscle tissue. Removal of water from the
tracheoles increases the rate of diffusion of oxygen between the tracheoles and muscle
tissue. Suggest one reason why.
- Greater surface area exposed to air
- Gases diffuse faster in air than through water
- Increases volume / amount of air
1 mark
The insect opens its spiracles at a lower frequency in very dry conditions. Suggest one
advantage of this.
Reduces water loss
2 marks
Abdominal pumping increases the efficiency of gas exchange between the tracheoles and
muscle tissue of the insect. Explain why.
- More oxygen enters
- So maintains / greater diffusion or concentration gradient
1 mark
Abdominal pumping is an adaptation not found in many small insects. These small insects
obtain sufficient oxygen by diffusion.
Explain how their small size enables gas exchange to be efficient without the need for
abdominal pumping
Large SA: V, reduces diffusion distance to tissues/cells
4 marks
Explain how the counter current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills
- Water and blood flow in opposite directions
- Blood always passing water with a higher oxygen concentration
- Diffusion gradient maintained throughout length of gill/ this maintains a conc gradient
- Diffusion occurs across whole length of lamella/ gill
2 marks
Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.
- Many lamellae / filaments so large surface area
- Thin (surface) so short diffusion pathway
Outline the factors that affect the rate of gas exchange
Fick’s Law= Surface Area x Concentration gradient/ diffusion pathway
