topic 3 - exchange and transport systems Flashcards
how does the surface area:volume ratio of an organism affect exchange?
a lower ratio means that exchange is more difficult (elephant) than an organism with a high ratio (mouse).
in single-celled organisms, what is diffusion like?
they can diffuse directly into/out of the cell through the membrane.
what is the speed of the rate of diffusion in single-cell organisms?
it is quick because of the small distance travelled.
in multicellular organisms, what is diffusion like?
it is too slow because some cells are deep within the body and some organisms have a low surface area:volume ratio
what is the definition of mass transport?
when multicellular organisms have an efficient system that carries substances to and from the cells.
which type of organism can maintain heat easily?
organisms with a low surface area:volume ratio.
which type of organism can’t maintain heat easily, and what must it have?
organisms with a high surface area:volume ratio; it must have a high metabolic rate to generate heat.
what two things do most gas exchange surfaces have in common to increase the rate of diffusion?
they have a large surface area and they’re thin.
what are gill filaments covered by, and what do they contain
lamellae; they have many blood capillaries.
how does the counter-current system work?
water with a high concentration of oxygen will always flow next to blood with low oxygen concentrations. a steep concentration gradient is maintained because of this, meaning there will be as much oxygen diffusing into the blood.
what cell type in plants are the main gas exchange surface?
mesophyll cells.
what are spiracles?
pores on the surface of insects.
what do insects do to move air in and out of spiracles?
they use rhythmic abdominal movements.
what is the correlation between water loss and gas exchange?
as gas exchange increases, water loss increases. there is a positive correlation.
what are different ways that plants can reduce water loss?
- a layer of hairs on the epidermis of the stomata.
- reduced number of stomata on plants in hot weather.
- waxy, thick cuticles on leaves and stems.
what 3 parts of the body (along with lungs) help move air in and out?
the ribcage, diaphragm and intercostal muscles.
what is the thoracic cavity?
the space where lungs are.
where are the intercostal muscles found?
between the ribs.
what happens during inspiration?
the ribcage moves up and out when the external intercostal muscles and diaphragm contract. the lung pressure decreases and air flows in.
is inspiration an active or passive process?
active process; it requires energy.
what happens during expiration?
the ribcage moves down and inwards when the external intercostal muscles and diaphragm relax. the lung pressure increases and air is forced out.
is expiration an active or passive process?
passive process; it doesn’t require energy.
what are the names of the walls of the alveoli and capillaries?
alveolar epithelium and capillary epithelium.
what order does oxygen travel through the gas exchange system?
trachea > bronchi > bronchioles > alveoli > alveolar epithelium > capillary epithelium > bloodstream
what is the volume of air in each breath known as?
the tidal volume.
what is the number of breaths per minute known as?
the ventilation rate.
what is the difference between endopeptidases and exopeptidases?
endopeptidases hydrolyse peptide bonds in the middle of a protein while exopeptidases hydrolyse peptide bonds at the end of proteins, by removing a single amino acid.
where are dipeptidases often located?
within the cell membrane of epithelial cells in the small intestine.
how are the different monosaccharides absorbed into the ileum epithelium?
- glucose: absorbed by active transport with sodium ions using a co-transporter.
- fructose: absorbed by a different transporter protein by facilitated diffusion.
- galactose: absorbed by active transport with sodium ions using a co-transporter.
what is the chemical equation for association and dissociation of oxygen from haemoglobin?
Hb (haemoglobin) + 4O₂ (oxygen) ⇌ HbO₈ (oxyhaemoglobin).
what gives haemoglobin it’s red colour?
the iron ion in each of the 4 haem groups.
what is the partial pressure of oxygen (pO₂)?
one of the conditions that affect oxygen affinity; it’s a measure of oxygen concentration. if it increases, so does the affinity.
what shape is a dissociation curve?
the graph is “S-shaped”.
what is the partial pressure of carbon dioxide (pCO₂)?
a measure of the concentration of CO₂ in a cell; it also affects oxygen unloading, with Hb giving up oxygen easier at a higher pCO₂.
what is the Bohr Effect?
when the dissociation curve “shifts” right and more oxygen is being released because the pCO₂ increases.
what does the dissociation curve look like for organisms living in low oxygen environments compared to humans, and why?
the curve is to the left of ours; there isn’t much oxygen available so Hb must have a high affinity.
what does the dissociation curve look like for organisms that are more active compared to humans, and why?
the curve is to the right of ours; Hb must unload oxygen easily due to the high demand.
what is tissue fluid made up of?
oxygen, water and nutrients.
how do substances move out of capillaries and into tissue fluid?
pressure filtration.
where is the hydrostatic pressure higher?
at the start of the capillary bed, the pressure is higher in inside the capillaries than in the tissue fluid.
where is the hydrostatic pressure lower?
at the venule end of the capillary bed, the hydrostatic pressure is lower, since fluid leaves.
water molecules are cohesive - what does that mean?
they stick together during transpiration.
what factors can affect the rate of transpiration?
- light intensity: the lighter it is, the higher the rate. more stomata open so CO₂ is let in for photosynthesis.
- temperature: the higher the temperature, the higher the rate. warmer molecules have more kinetic energy so they speed up, making the water potential gradient increase.
- humidity: the lower it is, the higher the rate of transpiration. if there is less water in the air around the plant, the water potential gradient is increased.
- wind speed: the windier, the higher the rate of transpiration. air movement will blow water molecules from the stomata away, so the water potential gradient increases.
what is translocation?
the movement of solutes like sugars and amino acids to another part where they’re needed.
