Topic 3 Organisms exchange substances. Surface area to volume ration + gas exchange Flashcards
what is surface area of an organism
The surface area refers to the total area of the organism that is exposed to the external environment
what is volume of an organism
The volume refers to the total internal volume of the organism (total amount of space inside the organism)
How do you calculate the volume?
Volume= length xheight x width
or
area of face X length/depth
How do you calculate the suface area of a cube
area of face (lengthxlength) X 6 sides
Face X six sides
How do you calculate the surface area of a cuboid
surface area of rectangles
2x length xheight
2x length x height
2x height x width
total SA iis 2(lxh+lxw+hw)
How do you calculate the surface area of a cylinder
area of circle faces= πXR² X 2
area of rectangle= 2πXradius X height
What is the surface area to volume ratio
The relationship between the size of an organism or structure and its surface area to volume ratio, plays a significant role in the types of adaptations an organism will have
How does an organisms size relate to their surface area to volume ratio?
The larger the organisms, the lower the surface area to volume ratio therefore they cannot just diffuse substances across their surface they require adaptations to increase their surface area.
In the case of single celled organisms, the substances can easily enter the cell as the distance that needs to be crossed over is short. However, in multicellular organisms that distance is much larger due to a higher surface area to volume ratio. As a result of that, multicellular organisms required specialised exchange surfaces for efficient gas exchange of carbon dioxide and oxygen.
quick due to short diffusion pathway
-high SA: volume ratio
-oxygen and carbon dioxide can directly diffuse into cell through cell-surface membrane
Describe the surface area to volume ratio of small organisms (single cellular)
Small organisms have a very large surface area in comparison to their volume. (large SA:Vol ratio) Meaning that there is a big surface for exchange of substances but also there is a smaller distance from the outside of the organisms to the middle of it, as a result very small organisms can simple exchange substances across their surface via diffusion
Describe the surface area to volume ratio of larger organisms (multi cellular)
The larger an organism the smaller its surface area to volume ratio (longer diffusion pathway) Larger organisms will typically have a higher metabolic rate which demands efficent transport of waste out of cells and reactants into cells. as a result they are adapted to heko this be more efiicent
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What is the metabolic rate of an organism
The metabolic rate of an organism is the amount of energy expended by that organism within a given period of time
The basal metabolic rate (BMR) is the metabolic rate of an organism when at rest. The BMR is significantly lower than when an organism is actively moving
small organisms:-higher metabolic rate (to generate enough heat to stay warm)
-have larger SA:volume ratio = larger surface area for heat loss
larger organisms:low metabolic rate
-have smaller SA: volume = smaller surface area for heat loss
How does an organisms surface area to volume ratio relate to their metabolic rate
the lower the Sa:Vol ratio the lower the metabolic rate
adaptations to increase surface area to volume ratio
Villi and microvilli-absorbtion of digested food
alveoli and bronchioles- Gas exchange
Spiracles and tracheoles- gas exchange
gill filaments and lamelle-gas exchange
thin wide leaves-gas exchange
many capilliries-capillary network
Name three features of an efficient gas exchange surface
- Large surface area e.g folded membranes in mitrochondria
- Thin/short distance e.g wall of capillaries
- steep concentration gradient maintained by blood supply or ventiliation e.g alveoli
Why cant insects use their bodies an exchange surface
They have a waterproof chitin exoskeleton and a small surface area to volume ratio in order to conserve water
Name and describe the three main features of an insects gas transport system
Spiracles-Holes on the body’s surface which may be opened or closed by a valve for gas or water exchange. oxygen and carbon dioxide enter and leave via spiracles
Trachea-large tubes extending through all body tissues supported by rings of cartilage preventing collapse
tracheoles- smaller branches dividing off the trachea. deliver oxygen to all respiring cells.
How are insects adapted to limit water loss
water evaporates off the surface of terrestrial insects and the adaptations of gas exchange surfaces provide ideal conditions for evaporation.
1.insects have a small surface area to volume ratio where water can evaporate from
2. insects have a waterproof exoskeleton
3. spiracles where gases enter and water can evaporate from, can open and close to reduce water loss
-close spiracles by abdominal muscle contractions in ventillation
-spiracles close when insect is at rest = gaseous exchange reduced + reduced water loss
small SA: volume ratio to minimise surface area for water loss
-waterproof, waxy cuticle around exoskeleton = reduced water evaporation
-small hairs around spiracles retain some water = less water evporated
Describe gas exchange in insects
Oxygen enters the insect’s body via diffusion through small openings on the surface called spiracles.
From the spiracles, the oxygen moves into the tracheae, which are large tubes that carry oxygen deeper into the body. (diffusion because when cells respire they use up oxygen and produce carbon dioxide creating a concentration gradient from tracheoles to the atmosphere)
The tracheae branch into finer tubes called tracheoles, which spread throughout the insect’s body to deliver oxygen directly to the cells.
Oxygen diffuses from the tracheoles into the surrounding cells, where it is used in cellular respiration.
contraction of muscles in the trachea allows mass movement of air in and out
Adaptations to Facilitate Efficient Gas Exchange in insects
Active transport: In some insects, muscle contraction around the tracheae helps to move air and ensure a higher rate of gas exchange.
Thin walls of tracheoles: The walls are thin to facilitate diffusion of gases quickly and efficiently.
Large number of fine tracheoles-large surface area for diffusion (highly branched)
walls of tracheoles are thin and short distance between spiracles and tracheoles short diffusion pathway
use of oxygen and production of carbon dioxide sets up steep concentration gradient.
Three methods of moving gases in the tracheal system
Gas exchange via diffusion as when cells respire they use oxygen and produce carbon dioxide creating a conc gradient from tracheoles to the atmosphere.
The second method of gas exchange is mass transport, in which an insect contracts and relaxes their abodminal muscles to move gases on mass.
When the insects are in flight their cells start to respire anaerobically to produce lactate, lowering the water potential of the cells and therefore water moves from the tracheoles into the cells by osmosis. this decreases the volume in tracheoles and as a result more air from the atmosphere is drawn in .
How are insects adapted to limit water loss
Waterproof/impermeable chitin coat/layer on exoskeleton reduce water loss
spiracles can open/close so less water loss
hairs around spiracles reduce water loss
Why cant fish use their bodies as an exchange surface
They have waterproof impermeable outer membranes and a small surface area to volume ratio
Describe features of a fish’s gas transport system
Gills are made up of stacks of gill filaments.
each gill filament is covered in gill lamellae, position at right angles to the filament. creating a large surface area. Blood and water flow across them in opposite directions (counter current exchange system)
when the fish open their mouth water rushes in and over the gills and then out through a hole in the sides of their head
What is ficks law
Diffusion ∝ surface area X difference in concentration/length of diffusion path
Adaptations of fish for efficient gas exchange
Large surface area to volume ratio created by many gill filaments covered in many gill lamellae
short diffusion distance due to a capillary network in every lamellae and very thin gill lamellae
maintaining concentration gradient- counter current flow mechanism. Water and blood flow in opposite directions; Maintains diffusion/concentration gradient of oxygen
What is the counter current exchange principle in fish, how does it maximise oxygen absorbed by the fish?
When water flows over the gills in the opposite direction to the flow of blood in the capillaries
counter current flow ensures that the equilibrium is not reached. this ensures that a diffusion gradient is maintained across the entire length of the gill lamellae.
Maintains a steep concentration gradient as water is always next to the blood of lower oxygen concentration. keeps diffusion constant along whole length of gill enabling 80% of available oxygen to be absorbed.
-water flow over lamellae and blood flow through lamellae are in opposite directions
-maintains a steep concentration gradient of O2 between blood and water
=more oxygen diffuses into blood
Explain the process of gas exchange in fish
The fish opens its mouth to enable water to flow in then closes its mouth to increase pressure.
The water passes over the lamellae and the oxygen diffuses into the blood stream.
Waste carbon dioxide diffuses into the water and flows back out of the gills.
Pathway of Oxygen Gas Exchange in Fish
Water containing oxygeb enter the buccal cavity (mouth). the fish opens its mouth and lowers its floor of the buccal cavity creating pressure differences that force water flow into the mouth and over the gills.
the water flows over the gill filaments, which are covered in lamellae. These filaments are rich in capillaries, which provide a large surface area for gas exchange.
As water flows over the gill filaments, oxygen diffuses from the water into the blood in the capillaries of the gill filaments. This occurs due to the difference in partial pressures of oxygen (higher in the water and lower in the blood).
At the same time, carbon dioxide diffuses from the blood in the capillaries into the water, due to the higher concentration of CO₂ in the blood compared to the water.
The oxygenated blood is then transported from the gills to the rest of the body.
Describe the structure of a leaf
Epidermis: single layer of cells on both upper and lower surfaces on leaf (transparent)
Palisade mesophyll: layer of tightly packed cells rich in chloroplasts
Spongy mesophyll: consists of irregularly shaped cells with large air spaces between them for gas exchange
Xylem and phloem_ xylem carries water minerals from root to the leaf. Phloem transports sugars
stomata are small pores allowing gas exchange c02 in oxygen out
describe gas exchange at a stomata
Oxygen diffuses out of the stomata
carbon dioxide diffuses in through the stomata
to reduce water loss by evaporation, stomata close at night when photosynthesis wouldn’t be occurring.
How are plants adapted for efficient gas exchange.
Thin and flat to provide short diffusion pathway and large surface area to volume ratio.
Lots of stomata allows gases to enter easily
air spaces in the mesophyll allow gases to move around the leaf facilitating photosynthesis
What are xerophytes
Xerophytes are plants adapted to survive in environments with limited water.
They have structural features to enable efficient gas exchange to occur whilst limiting water loss
How are xerophytes adapted for gas exchange and limited water loss
Curled leaves to trap moisture to increase local humidity
hairs to trap moisture to increase local humidity
air spaces in the mesophyll allow gases to move around leaf
sunken stomata to trap moisture to increase local humidity
lots of stomata regulated by guard cells which allows them to open and close as needed. most stay closed to prevent water loss while some open to let oxygen in.
thin and flat to provide short diffusion pathway large sa:vol
Describe the gross structure of the human gas exchange system and how we breathe in and out
Nasal cavity➜ trachea➜ bronchi➜ bronchioles➜ alveoli
Inspiration
diaphragm contracts and external intercostal muscles contract; rib cage moves up and out. thoracic volume increases thoracic pressure decreases. atmospheric pressure is greater than inside so air is forced in.
Expiration
Diaphragm relaxes (returns to dome shape) internal intercostal muscles contract ribs move down and in causing thoraxic volume to decrease pressure increases pressure inside is more than pressure atmospheric forcing air to move out.
adaptations of alveolar epithelium for gas exchange
-(alveolar epithelium= layer of cells where gas exchange occurs)
-lots of alveoli in lungs= large surface area
-alvoili have folded walls= large surface area
-alevoli surrounded by capillary networks= large surface area
-capillaries have constant blood supply= constant concentration gradient of gases between alveolar epithelium and capillary epithelium
-alveolar and capillary epithelium= only 1 cell thick= thin difffusion pathway= fast diffusion
-collagen and elastic fibres between alveoli= alveoli can stretch when filling with air and revert to original shape (flexible shape)
process of inspiration
-external intercostal muscles and diaphragm contract (internal intercostal muscles relax)
-ribgage moves upwards and ouwards
-diaphragm flattens
-thoracic cavity volume increases= pulmonary pressure decreases below atmospheric pressure
-air forced into lungs down a pressure gradient
-requires energy from ATP
What is the closed and double circulatory system
closed-blood remains within the vessels
double circulatory system: blood passes through the heart twice in each circuit. on ecircuit which delivers blood to the lunchgs and one that delivers blood to the rest of the body
Desribe the function of the nasal cavity in the mammalian gaseous exchnage system
good blood supply warms and moistens air entering the lungs. goblet cells in the membrane secrete mucus which traps the dust bacteria
Describe the trachea and its functions in the mammalian gaseous exchnage system
wide tube supported by c shaped cartilage to keep the air passage open during pressure chnages
lined by ciliated epithelium cells which move mucus towards the throat to be swallowed preventing lung infections
carries air to the bronchioles
Describe the bronchi and their function in the mammalian gaseous exchange system
supported by rings of cartilage and lined by ciliated epithelium cells
but are narrower and there are two of them
allow passage of air in broncihles
Describe the bonchioles and their function in the mammalian exchange system
narrower than the bronchi
do not need to be kept open byc cartilage, therefore mostly have msucles and ellastic fibres so that they can contract and relax easily during ventilation allow passage of air into the alevoli
What is tidal volume
volume of air that we breathe in and out during each breath at rest
What is vital capacity
max volume of air we can inhale and exhale
Residual volume
volume of air left in lungs after the strongest exhalation
What is pulmonary ventilation and how can you calculate it
Pulmonary ventilation is the total volume of air that is moved into the lungs during one minuted.
pulmonary ventilation dm3min-1 = tidal volume x ventilation rate
what is breathing/ventilation rate
number of breaths we take per minute
