topic 3 - exchange and transport systems

Question 1

how does the surface area:volume ratio of an organism affect exchange?

Answer 1

a lower ratio means that exchange is more difficult (elephant) than an organism with a high ratio (mouse).

Question 2

in single-celled organisms, what is diffusion like?

Answer 2

they can diffuse directly into/out of the cell through the membrane.

Question 3

what is the speed of the rate of diffusion in single-cell organisms?

Answer 3

it is quick because of the small distance travelled.

Question 4

in multicellular organisms, what is diffusion like?

Answer 4

it is too slow because some cells are deep within the body and some organisms have a low surface area:volume ratio

Question 5

what is the definition of mass transport?

Answer 5

when multicellular organisms have an efficient system that carries substances to and from the cells.

Question 6

which type of organism can maintain heat easily?

Answer 6

organisms with a low surface area:volume ratio.

Question 7

which type of organism can’t maintain heat easily, and what must it have?

Answer 7

organisms with a high surface area:volume ratio; it must have a high metabolic rate to generate heat.

Question 8

what two things do most gas exchange surfaces have in common to increase the rate of diffusion?

Answer 8

they have a large surface area and they’re thin.

Question 9

what are gill filaments covered by, and what do they contain

Answer 9

lamellae; they have many blood capillaries.

Question 10

how does the counter-current system work?

Answer 10

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.

Question 11

what cell type in plants are the main gas exchange surface?

Answer 11

mesophyll cells.

Question 12

what are spiracles?

Answer 12

pores on the surface of insects.

Question 13

what do insects do to move air in and out of spiracles?

Answer 13

they use rhythmic abdominal movements.

Question 14

what is the correlation between water loss and gas exchange?

Answer 14

as gas exchange increases, water loss increases. there is a positive correlation.

Question 15

what are different ways that plants can reduce water loss?

Answer 15

• 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.

Question 16

what 3 parts of the body (along with lungs) help move air in and out?

Answer 16

the ribcage, diaphragm and intercostal muscles.

Question 17

what is the thoracic cavity?

Answer 17

the space where lungs are.

Question 18

where are the intercostal muscles found?

Answer 18

between the ribs.

Question 19

what happens during inspiration?

Answer 19

the ribcage moves up and out when the external intercostal muscles and diaphragm contract. the lung pressure decreases and air flows in.

Question 20

is inspiration an active or passive process?

Answer 20

active process; it requires energy.

Question 21

what happens during expiration?

Answer 21

the ribcage moves down and inwards when the external intercostal muscles and diaphragm relax. the lung pressure increases and air is forced out.

Question 22

is expiration an active or passive process?

Answer 22

passive process; it doesn’t require energy.

Question 23

what are the names of the walls of the alveoli and capillaries?

Answer 23

alveolar epithelium and capillary epithelium.

Question 24

what order does oxygen travel through the gas exchange system?

Answer 24

trachea > bronchi > bronchioles > alveoli > alveolar epithelium > capillary epithelium > bloodstream

Question 25

what is the volume of air in each breath known as?

Answer 25

the tidal volume.

Question 26

what is the number of breaths per minute known as?

Answer 26

the ventilation rate.

Question 27

what is the difference between endopeptidases and exopeptidases?

Answer 27

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.

Question 28

where are dipeptidases often located?

Answer 28

within the cell membrane of epithelial cells in the small intestine.

Question 29

how are the different monosaccharides absorbed into the ileum epithelium?

Answer 29

• 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.

Question 30

what is the chemical equation for association and dissociation of oxygen from haemoglobin?

Answer 30

Hb (haemoglobin) + 4O₂ (oxygen) ⇌ HbO₈ (oxyhaemoglobin).

Question 31

what gives haemoglobin it’s red colour?

Answer 31

the iron ion in each of the 4 haem groups.

Question 32

what is the partial pressure of oxygen (pO₂)?

Answer 32

one of the conditions that affect oxygen affinity; it’s a measure of oxygen concentration. if it increases, so does the affinity.

Question 33

what shape is a dissociation curve?

Answer 33

the graph is “S-shaped”.

Question 34

what is the partial pressure of carbon dioxide (pCO₂)?

Answer 34

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.

Question 35

what is the Bohr Effect?

Answer 35

when the dissociation curve “shifts” right and more oxygen is being released because the pCO₂ increases.

Question 36

what does the dissociation curve look like for organisms living in low oxygen environments compared to humans, and why?

Answer 36

the curve is to the left of ours; there isn’t much oxygen available so Hb must have a high affinity.

Question 37

what does the dissociation curve look like for organisms that are more active compared to humans, and why?

Answer 37

the curve is to the right of ours; Hb must unload oxygen easily due to the high demand.

Question 38

what is tissue fluid made up of?

Answer 38

oxygen, water and nutrients.

Question 39

how do substances move out of capillaries and into tissue fluid?

Answer 39

pressure filtration.

Question 40

where is the hydrostatic pressure higher?

Answer 40

at the start of the capillary bed, the pressure is higher in inside the capillaries than in the tissue fluid.

Question 41

where is the hydrostatic pressure lower?

Answer 41

at the venule end of the capillary bed, the hydrostatic pressure is lower, since fluid leaves.

Question 42

water molecules are cohesive - what does that mean?

Answer 42

they stick together during transpiration.

Question 43

what factors can affect the rate of transpiration?

Answer 43

• 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.

Question 44

what is translocation?

Answer 44

the movement of solutes like sugars and amino acids to another part where they’re needed.