Gas exchange Flashcards
Features of an efficient gas exchange system
1) Large SA:V
2) Short diffusion distance
3) Steep concentration gradient
How does SA:V relate to an organisms size?
The smaller the organism the larger the SA:V.
How does SA:V relate to organisms metabolic rate?
The smaller the SA:V the higher the metabolic rate.
Why do multicellular organisms need gas exchange systems?
Smaller SA:V means more distance needs to be crossed for substances to reach cells.
What are insect adaptations to limit water loss?
a) Small SA:V of place where water can evaporate
b) Have chitin waterproof lipid coated exoskeleton so water doesn’t evaporate across body
c) Spiracles can open and close
Describe parts of the insect gas exchange system
SPIRACLE: Small valve opening across abdomen which lets O2 in and CO2 out.
TRACHEA: Internal tubing with disks to hold shape.
TRACHEOLS: Extended tubing to respiring tissue/cells
How are insects adapted for large SA:V?
Lots of tracheoles.
How are insects adapted for short diffusion distances?
Walls of tracheoles are thin + small in size so short distance between spiracles and tracheoles.
How are insects adapted for steep diffusion distances?
Constant intake of O2 and production of CO2.
Explain the process of gas exchange in insects
1) Simple diffusion: Cells make CO2 and use up O2 which makes a concentration gradient from atmosphere-inside.
2) Mass transport: Contraction and relaxing of abdominal muscles pumps gases across.
3) Pressure gradient: during flight when there is anaerobic respiration = lactate = lower water potential = water osmosis from tracheoles-cells = less volume in tracheoles = less pressure = air enters.
Describe the parts of a fish’s gas exchange system
GILLS: 4 layers on each side of head.
GILL FILAMENTS: V shape stack together to make a gill
GILL LAMELLAE: Cover the gill filaments at right angles.
How are fish adapted to large SA:V?
Many gill filaments covered by many gill lamellae at right angles.
How are fish adapted to short diffusion distances?
Very thin lamellae + capillary bed in every lamellae.
How are fishes adapted to steep concentration gradient?
Using the counter current flow mechanism.
Explain the counter current flow mechanism
Water flows over gills in the opposite direction to the blood flow in capillaries so water is always slightly more concentrated than the blood. This ensures equilibrium is never reached and diffusion gradient is maintained across entire lamellae.
Explain concurrent flow mechanism
Water flows in the same direction as blood ( water= 100% - blood= 0%)
So starts with rapid diffusion but reached 50% so not across entire lamellae.
Explain the process of gas exchange in fish
Water in though mouth, water over lamellae, O2 diffuses into blood stream, waste CO2 diffuses into water and out through gills.
What are plant adaptions to limit water loss?
a) Stomata: Can open and close- but mostly close
b) Waterproof cuticles: So no water loss across leaf
What are some structural features of xerophytes?
a) Thick cuticles: Less evaporation.
b) Curled leaf: Trap water= increase humidity= lowers inside water potential= less water exits.
c) Hairy/ spiky leaf: Traps water.
d) Stomata in pits: Traps water.
e) Longer root network: Reach water in further places.
Describe the parts of a plants gas exchange system
STOMATA: Many small pores on underside of leaf which open close to allow gas in and out.
AIR SPACES: In the spongy mesophyll allows gas to move around leaf.
How are plants adapted to large SA:V?
Thin and flat leaf.
How are plant adapted to short diffusion distances?
Thin and flat leaf.
How are plants adapted to steep concentration gradients?
With the stomata open, production and consumption of O2 and CO2 in the leaf is sufficient to maintain a concentration gradient for gas exchange with the atmosphere and inside.
Describe the parts of the human gas exchange system
LUNGS
NASAL CAVITY: Warms/moistens air entering lungs + goblet cells secrete mucus to trap dust/bacteria
TRACHEA: Tube supported by C-shaped cartilage to keep passage open during pressure change + lined with ciliated cells
BRONCHI: 2 narrow tubes supported by C-shaped rings + lined with ciliated cells
BRONCHIOLES: Made of muscle/elastic fiber to contract/relax
ALVEOLI: Mini air sacks which are site of gas exchange
How are alveoli adapted to large SA:V?
300 million per each lung
How are alveoli adapted to short diffusion distance?
Epithelium cells + wall of the capillary are 1 cell thin
How are alveoli adapted to steep concentration distance?
Each alveoli is surrounded by a network of capillaries that remove exchanged gas
Explain the process of inspiration
- External ICM contract = pulls ribs up and out
- Internal ICM relax
- Diaphragm contracts = flattens from dome position
- Lung volume increases = pressure initially drops = Air moves in from atm pressure to lower pressure = pressure rises
Explain the process of expiration
- External ICM relax
- Internal ICM contract = pulls ribs down and in
- Diaphragm relaxes = returns to dome position
- Lung volume decreases = pressure initially > than atm pressure = air moves out of lungs from high pressure to atm pressure = pressure drops
Explain gas exchange in the alveoli
- Blood vessel has a high concentration of CO2 = diffuses out to alveoli
- Alveoli have a high concentration of O2 = diffuses out to blood vessel
What apparatus is used to measure lung capacity?
Spirometer
Tidal volume
The volume of air that enters + leaves the lungs at normal resting breath
Vital capacity
Max volume of air we can inhale + exhale
Residual volume
Volume of air left in lungs after strongest exhalation
Total lung capacity
Vital capacity + residual volume
Ventilation rate
Breaths per minute
Pulmonary ventilation
The total volume of air that is moved into lungs during 1 minute
How to calculate pulmonary ventilation
Tidal volume(dm3) * Ventilation rate(min-1)
Describe how can lung diseases affect ventilation/gas exchange
- Narrowed bronchioles = less concentration of gas exchanged + less O2 delivered to respiring cells
- Broken down/thicker alveoli walls = fewer and larger sacks = less SA:V so less concentration of gas exchange and can’t expand as much
Evaluate a lung disease graph for cigarettes + lung cancer
- Positive correlation trend
- But data overlaps on certain points
- Correlation doesn’t = causation as other factors e.g. genetics, exposure, pollution, or other lung diseases can cause deaths and are not mentioned
- There is no correlation statistic to show correlation is significant
