Gas Exchange And Circulatory System

Question 1

State Fick’s law:

Answer 1

The rate of diffusion is directly proportional to (surface area x conc. difference)/distance

Question 2

Why do organisms larger than 100 micrometers have to be multicellular?

Answer 2

The diffusion pathway would be too long to support the life as rate of diffusion would be too slow

Question 3

Give 3 examples of specialised exchange systems:

Answer 3

Lungs, gills, intestines, roots and leaves

Question 4

Why do smaller animals have a higher metabolic rate?

Answer 4

Smaller animals: smaller volumes to surface area ratio, more heat is lost, high metabolism generates a lot of heat

Question 5

How is diffusion passive?

Answer 5

It requires no energy

Question 6

What is the difference between mass flow and diffusion?

Answer 6

Mass flow-> requires a pump and force, independent of concentration differences
Diffusion-> passive

Question 7

Examples of mass flow are?

Answer 7

Circulatory system, xylem, phloem and ventilation

Question 8

How have tapeworms adapted for gas exchange?

Answer 8

Very long and thin -> high SA:volume

-> short diffusion pathway

Question 9

How have marine sponges adapted for gas exchange?

Answer 9

Hollow Tube shape -> highSA:volume
1 cell think walls -> short diffusion pathway
Beating flagella-> maintain flow of water (conc. gradient)

Question 10

Describe the route air takes from the atmosphere to a muscle cell of an insect:

Answer 10

• enters via the spiracle (holes in the exoskeleton)
• leads to network of trachea
• which branch into tracheoles
• tracheoles carry air to every muscle cell of the insect

Question 11

When insects fly any water build up in the insect tracheoles goes away, but how and why?

Answer 11

• insect muscles respire anaerobically producing lactic acid
• this lowers the water potential in muscle cells
• water from tracheoles diffuses into muscle cells by osmosis
• this also makes diffusion of oxygen occur faster

Question 12

How have some insects adapted for gas exchange?

Answer 12

• some ventilate their tracheal system -> muscles squeeze the trachea sucking air in and out
• some close their spiracles when inactive to reduce water loss

Question 13

Describe the structure of a fish’s gill

Answer 13

Gill-> composed of thousands of filaments-> which are covered in feathery lamellae

Question 14

Why are lamellae essential for gas exchange?

Answer 14

• provide a huge surface area (90 degrees to gill filament)
• very thin (short diffusion pathway)
• contain capillaries (maintain conc. gradient)

Question 15

How is fish ventilation different to human ventilation?

Answer 15

Human - tidal

Fish - one way

Question 16

How have fish adapted for gas exchange?

Answer 16

Counter current flow

Question 17

Explain counter current flow:

Answer 17

• Bloods flows opposite way in the lamellae to the water in the fish’s mouth
• there is always a higher conc of O2 in the water than the blood, so O2 diffuses continuously
• 80% O2 is usually extracted this way

Question 18

Humans have a double circulatory system, what are the 2systems called?

Answer 18

Pulmonary circulation

Systematic circulation

Question 19

What are the different kinds of blood vessels?

Answer 19

Arteries-> arterioles -> capillaries -> venules -> veins

Question 20

Why has the artery got such a thick elastic layer?

Answer 20

• allows the artery to expand without bursting
• withstand high pressure
• recoil during diastole

Question 21

Everything we know on arterioles:

Answer 21

• each arterioles leads to a capillary bed
• mainly smooth muscle tissue to regulate blood flow to capillary beds
• (vasodilate and vasoconstrict)

Question 22

Capillary structure:

Answer 22

Very narrow
Extremely high surface area to volume ratio
Walls are single squamous endothelial cell thick

Question 23

Why do veins contain semi lunar valves?

Answer 23

• Pressure has all been lost in capillaries

- little driving force up veins so valves prevent the back flow

Question 24

How does blood flow up the veins in the legs or lower body?

Answer 24

Contracting muscles surrounding the veins squeeze the veins pushing the blood up

Question 25

Once plasma is forced out the capillary bed it forms tissue fluid, what substances then move into the cells from tissue fluid? And how

Answer 25

Water - osmosis
Ions - facilitated diffusion
Glucose and amino acids - active transport
Lipid soluble substances - lipid diffusion

Question 26

What is the purpose of the lymph vessel?

Answer 26

There is always excess tissue fluid so it drains into the lymph vessels, these are like capillaries but inside is lymph

Question 27

Describe the process (4 steps) and purpose of formation of tissue fluid:

Answer 27

• at arterial end of capillary bed blood pressure is high, blood plasma is forced out (cells and protein are too big)
• the tissue fluid surrounds the cells where materials are exchanged between the fluid and the cells by all methods
  (Glucose, amino acids -> AT, water->osmosis, ions ->FD)
  -at venous end of capillary bed blood pressure is low and water potential is high, so tissue fluid returns by diffusion into capillary with CO2, urea and salts, water also returns by osmosis
  -not all the fluid returns, excess tissue fluid is drained into the lymph vessels forming lymph

Question 28

What are the 3 functions of the lymphatic system?

Answer 28

1- drain excess tissue fluid
2- to absorb fats from small intestine via lacteals in each villus
3- as part of the immune system (lymph nodes developed white blood cells)

Question 29

What is the difference between blood plasma, lymph and tissue fluid?

Answer 29

Blood plasma: liquid part of blood, contains dissolved glucose, amino acids, salts, vitamins and insoluble proteins and fats
Tissue fluid: solution surrounding cells, like plasma but with fewer proteins (too big to diffuse across capillary wall)
Lymph: solution inside lymph vessels, similar to tissue fluid but with more fats (from digestive system)

Question 30

What is the equation for haemoglobin when it binds to a 3rd oxygen molecule?

Answer 30

Hb(O2)2 + O2 <=> Hb(O2)3

Question 31

Describe the structure of a haemoglobin and why it can bind to only 4 oxygen molecules:

Answer 31

• 4 polypeptide chains, each with a prosthetic Haem group

- each haem group contains an iron atom which can bind to a single O2 molecule

Question 32

How can % saturation of O2 in blood be measured?

Answer 32

Oxygenated blood is a different colour to oxygenated blood

Therefore % saturation can be tested with a colorimeter

Question 33

What is the Bohr effect?

Answer 33

When there is a lower pH or increased concentration of CO2 which dissolves in tissue fluid to form carbonic acid, the oxygen association curve shifts right

Question 34

How is fetal haemoglobin different from adult?

Answer 34

• fetal haemoglobin has a higher affinity for oxygen at a lower partial pressure, so is shifted left

Question 35

How is lugworm haemoglobin different from adult?

Answer 35

• lugworms live in holes in the sand and when the tide is out, there is no constant supply of new water and oxygen, so the ppO2 gets low
• haemoglobin has a very high affinity for oxygen at a very low ppO2, so curve is shifted far left

Question 36

How has the mouse haemoglobin adapted for its survival?

Answer 36

• mice high surface area: volume ratio, so lose lots of heat
• high metabolic rate to produce more heat
• tissues have a constant demand for O2 for respiration
• curve is shifted right so higher % of oxygen is unloaded to tissues at the same/lower ppO2