Gas exchange Flashcards
(20 cards)
How is the body surface of a single-celled organism adapted for gas exchange?
- thin, flat shape & larger SA:V
- short diffusion distance to all parts of the cell which allows rapid diffusion of e.g. oxygen & carbon dioxide
What does the tracheal system of an insect include?
- spiracles - pores on surface that open/close to allow diffusion
- tracheae - large tubes full of air that allow diffusion
- tracheoles - smaller branches from tracheae which is permeable to allow gas exchange with cells
How is an insect’s tracheal system adapted for gas exchange?
- tracheoles have thin walls - short diffusion distance
- high numbers of highly branches tracheoles - short diffusion distance & large SA
- tracheae provides tubes filled with air - allows fast diffusion
- contraction of abdominal muscles changes pressure in body which causes air to move in/out - maintains conc gradient for diffusion
- fluid in end of tracheoles drawn into tissues by osmosis during exercise - diffusion is faster through air rather than fluid to gas exchange surface
What are the structural & functional compromises in terrestrial insects that allow efficient gas exchange while limiting water loss?
- thick exoskeleton - increases diffusion distance so less water loss
- spiracles can open to allow gas exchange & closes to reduce water loss
- hairs around spiracles - trap moist air reducing water potential gradient so less water loss
How are the gills of a fish adapted for gas exchange?
- gills are made of many filaments covered with many lamellae - increase SA for diffusion
- thin lamellae wall - short diffusion distance
- lamellae have large no. of capillaries - maintains conc gradient
What is the counter current flow in gills?
- blood & water flow in opposite directions over lamellae
- conc of oxygen is always higher in water
- this maintains conc gradient of oxygen between water & blood
- diffusion can occur efficiently along the whole length of lamellae
How are the leaves of dicotyledonous plants adapted for gas exchange?
- many stomata which provides a large SA for gas exchange
- spongy mesophyll has air spaces - gives large SA for gases to diffuse through
- thin which provides short diffusion distance
What are the structural & functional compromises in xerophytes that allow efficient gas exchange while limiting water loss?
- thicker waxy cuticle - increases diffusion distance so less evaporation
- sunken stomata in pits - trap water vapour so reduced water potential gradient for less evaporation
- needles reduce SA:V
What is the human gas exchange system made of?
lungs are the site of ventilation
- trachea
- bronchi
- bronchioles
- capillary network surrounds alveoli
What are the essential features of the alveolar epithelium that make it adapted for gas exchange?
- flattened cells - short diffusion distance
- folded - large surface area
- permeable - allows diffusion of oxygen & carbon dioxide
- moist - gases can dissolve for diffusion
- large network of blood capillaries - maintains conc gradient
How does gas exchange occur in the lungs?
oxygen diffuses from alveoli into blood down its conc gradient across alveolar epithelium then across capillary endothelium
What is the importance of ventilation?
it brings in air with high conc of oxygen & removes air with low conc of oxygen maintaining conc gradients
How do humans breathe in and out?
inspiration:
1. diaphragm contracts & flattens
2. external intercostal muscles contract, internal intercostal muscles relax & ribcage is pushed up and out
3. volume in thorax increases and pressure decreases (less than atmospheric pressure)
4. air moves into lungs down the pressure gradient
expiration:
1. diaphragm relaxes & moves upwards
2. external intercostal muscles relax, internal intercostal muscles may contract & ribcage moves down and in
3. volume in thorax decreases so pressure increases (more than atmospheric pressure)
4. air moves out of lungs down the pressure gradient
Why is expiration normally passive at rest?
- internal intercostal muscles don’t normally need to contract
- expiration is aided by elastic recoil in alveoli
How do different lung diseases reduce the rate of gas exchange?
- thickened alveolar tissue - increases diffusion distance
- alveolar wall breakdown - reduces surface area
- reduces lung elasticity - lungs expand/recoil less which reduces conc gradient of oxygen & carbon dioxide
How do different lung diseases affect ventilation?
- reduce lung elasticity - lungs expand/recoil less which reduces tidal volume & vital capacity
- narrow airways in & out of the lungs which reduces forced expiratory volume
- reduced rate of gas exchange - increases ventilation rate to compensate for reduced oxygen in blood
Why do people with lung disease experience fatigue?
cells receive less oxygen - rate of aerobic respiration reduces so less ATP made
How can you analyse & interpret data to the effects of pollution, smoking and other risk factors on the incidence of lung disease?
- describe overall trend e.g. positive/ negative correlation
- manipulate data e.g. calculate percentage change
- interpret standard deviations - overlap suggests there is no significant difference and it’s likely due to chance
- use statistical tests to identify whether difference/ correlation is significant or due to chance e.g. correlation coefficient examines association between 2 variables, student’s test compares means of 2 sets of data & chi-squared test is for categorical data
How can you evaluate the way in which experimental data led to statutory restrictions on the sources of risk factors?
- analyse & interpret data & identify what does and doesn’t support statement
- evaluate method of collecting data e.g. if sample size is large enough to be representative of population, if pps diversity is representative, control groups for comparison, if control variables are valid & duration of study to show long-term effects
- evaluate context & if a broad generalisation has been made from a specific set of data
- other risk factors that could have been affected results
What is the difference between correlations & causal relationships?
- a correlation occurs when there is a change in one variable reflected by a change in another
- a causation occurs when a change in one variable causes a change in another
- correlation doesn’t mean causation as there may be other factors involved
