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A-level Biology > 8 - Transport In Animals 🫀 > Flashcards

8 - Transport In Animals 🫀 Flashcards

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1
Q

Why are specialised transport systems needed?

A
  • metabolic demands
  • SA:V
  • transporting molecules (hormones/enzymes/food)
  • waste products need to be removed
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2
Q

Most circulatory systems have what features in common?

A
  • a liquid transport medium that circulates around the body
  • have vessels that carry the medium
  • a pumping mechanism to move fluid around the system
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3
Q

What processes take place over the membrane?

A
  • diffusion
  • osmosis
  • active transport
  • endocytosis
  • exocytosis
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4
Q

Give an example of animals with open circulatory systems

A

Molluscs 🦑
Arthropods

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5
Q

Give an example of animals with closed circulatory systems

A

Vertebrates

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6
Q

What is a mass transport system?

A

When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body

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7
Q

Where is blood pumped in an open circulatory system?

A

Straight from the heart into the body cavity of the animal (called the haemocoel)

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8
Q

In the haemocoel, what is the pressure of tbe transport medium?

A

The transport medium is under low pressure, and comes under direct contact with tissue and cells

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9
Q

How do the transport medium return to the heart in an open circulatory system?

A

Through an open-ended vessel

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10
Q

What is an ostium in insects?

pl = Ostia

A

A small opening

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11
Q

What is haemolymph?

A

A circulating fluid in the bodies of some invertebrates that is the equivalent of blood

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12
Q

What is haemocoel?

A

The system of cavities between the organs through which blood circulates in an open system

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13
Q

What is carried by haemolymph?

A

Food and nitrogenous waste

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14
Q

What is not carried by haemolymph?

A

Oxygen and carbon dioxide as insects have a tracheal system for that

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15
Q

What is the problem with haemolymph in an open system?

A
  • steep diffusion gradients can’t be maintained
  • amount of haemolymph flowing can’t be varied to meet demands
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16
Q

What happens when the heart relaxes in an open circulatory system in insects?

A

The haemolymph blood is sucked back in via ostia

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17
Q

What happens in closed circulatory systems?

A

Blood is enclosed in blood vessels and doesn’t come directly into contact with the cells of the body

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18
Q

How do substances leave and enter blood in a closed system?

A

By diffusion

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19
Q

How can the amount of blood flowing to a tissue be adjusted in a closed system?

A

By widening or narrowing blood vessels

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20
Q

Fish

What is the structure of the single closed circulatory systems in fish?

A
  • heart has 2 chambers
  • blood passes through 2 sets of capillaries: 1 gill capillaries and systemic capillaries
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21
Q

Fish

Why is low pressure needed?

A

As blood goes through 2 sets of narrow vessels, so pressure must be low to avoid damage

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22
Q

Fish

How come fish can cope with high metabolic demand with a single circulatory system?

A
  • SHC of water is hard to change = fish don’t need to worry about temperature
  • counter-current mechanism = efficient
  • water supports body weight
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23
Q

What happens in a single circulatory system?

A

The blood travels through the heart and is pumped around the body once

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24
Q

In a single closed system, what does the blood exchange in the first set of capillaries it passes through?

A

Oxygen and carbon dioxide

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25
Q

In a single closed system, what does the blood exchange in the second set of capillaries it passes through?

A

Substances are exchanged between blood and cells

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26
Q

As a result of passing through two sets of narrow capillaries, what happens in a single closed system?

A
  • blood pressure drops
  • blood returns slowly to heart
  • limits efficiency of exchange process
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27
Q

What is the most efficient system for transporting substances around the body?

A

Double closed circulatory system

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28
Q

What are the 2 separate circulations in a double system?

A
  • blood is pumped from the heart to the lungs
  • blood flows through the heart and is pumped around the body
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29
Q

Why is there higher pressure and fast flow of blood in a double system?

A

Each circuit only passes through one capillary network, so no need to slow down as much as in a single

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30
Q

Why do birds and mammals need need a double closed circulatory system?

A

They need to maintain their own body temperature, so require high metabolic demand

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31
Q

Advantages to a single circulatory system

A
  • less complex
  • doesn’t require complex organs
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32
Q

Advantages to a double circulation

A
  • separates blood
  • higher pressure
  • fast flow of blood
  • blood pumped further around body
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33
Q

Disadvantages of single circulation

A
  • low blood pressure
  • slow movement of blood
  • activity level of the mammal tend to be lower
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34
Q

Disadvantages of double circulation

A
  • highly complex in development
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35
Q

What are the 5 types of blood vessels?

A
  • arterioles
  • arteries
  • capillaries
  • venules
  • veins
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36
Q

What do elastic fibres do in vessels?

A
  • stretch and recoil
  • providing flexibility to ease blood flow
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37
Q

What does smooth muscle do in vessels?

A
  • contract and relax
  • changes size of lumen
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38
Q

What does collagen do in vessels?

A
  • provides structural support
  • maintains shape and volume of vessel
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39
Q

What do arteries carry?

A

carry oxygenated blood away from the heart to tissues

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40
Q

When do arteries carry deoxygenated blood?

A

in the pulmonary artery on the way to the lungs, and during pregnancy in the umbilical artery, carrying blood from fetus to placenta

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41
Q

How does blood flow out of the heart?

A

expelled from the heart upon ventricular contraction, and flows through the arteries in repeated surges called pulses

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42
Q

What assists in maintaining the pressure in the artery?

A

smooth muscle and elastic fibres

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43
Q

How does the structure of a narrow lumen help an artery’s function?

A
  • creates less volume = increases pressure
  • maintains high blood pressure
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44
Q

How does a thick wall containing an outer layer of collagen help an artery’s function?

A
  • to withstand high pressure to prevent the artery from rupturing
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45
Q

How does an inner layer of muscle and elastic fibres help an artery’s function?

A
  • maintains pulse flow smoothly
  • controls diameter of lumen
  • does not pump blood
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46
Q

What does elastic do in artery walls?

A
  • allows stretch and recoil
  • evens out surges of blood pumped from hart to create a continuous flow
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47
Q

Why is the lining of an artery smooth?

A

so blood flows over it easily

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48
Q

What links arteries and capillaries?

A

arterioles

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49
Q

How are arterioles different to arteries?

A

have more smooth muscle and less elastin in their walls, as they have little pulse surge, but can constrict or dilate to control the flow of blood

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50
Q

What happens when smooth muscle in the arteriole contracts?

A

it constricts the vessel and prevents blood flowing into a capillary bed = vasoconstriction

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51
Q

What is vasodilation?

A

when the smooth muscle in the wall of an arteriole relaxes, blood flows through into the capillary bed

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52
Q

How does a very narrow diameter help a capillary’s function?

A

reduces blood flow to allow time for exchange between blood and surrounding cells to take place more efficiently

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53
Q

How does having thin walls only 1 cell thick help a capillary’s function?

A

ensures maximum rate of transfer between blood and surrounding tissue fluid (short diffusion pathway) as they don’t need to withstand high pressure

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54
Q

How does having walls have gaps (leaky walls) help a capillary’s function?

A

allows plasma and dissolved substances to leave the blood ()high permeability

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55
Q

What shows just how tiny capillaries are?

A

Red blood cells have to travel single file through them

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56
Q

Why do capillaries have such large gaps in their walls?

A

where many substances pass out of the capillaries into the fluid surrounding the cells

the exception of these gaps is in the CNS, which have very tight junctions between cells

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57
Q

What does it mean if the capillary wall is continous?

A

the capillary wall may be continuous with endothelial cells held together by tight junctions to limit permeability of large molecules

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58
Q

What does it mean if the capillary wall is fenestrated?

A

occurs in tissues specialised for absorption, the capillary contains pores

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59
Q

What does it mean if the capillary wall is sinusoid?

A

they have open spaces between cells and be permeable to large molecules and cells to allow large molecules to exchange

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60
Q

How does a very wide lumen (relative to wall thickness) help a vein’s structure?

A

maximises blood flow for more effective return

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61
Q

How does a thin wall containing less muscle/elastin but more collagen help a vein’s structure?

A

carries blood at low pressure (5-10mmHg) so doesn’t need to withstand high pressure

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62
Q

How does a vein having valves help its function?

A

prevents backflow and pooling

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63
Q

Why do veins not have a pulse?

A

the surges from hearts are lost at capillaries

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63
Q

Why do veins not have a pulse?

A

the surges from hearts are lost at capillaries

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64
Q

What do several venules rejoin to form?

A

one vein

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65
Q

What do venules contain?

A

no elastin fibres or smooth muscle, only collagen for structural support

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66
Q

What % of your blood volume is in your veins at any 1 time?

A

60%

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67
Q

What are the 3 adaptations of veins to move blood against gravity?

A
  • 1-way valves that close if blood starts to flow back
  • bigger veins run between big, active muscles in body so when the muscle contracts, the veins are squeezes
  • the breathing movements of the chest act as a pump as the pressyre changes and squeezing actions move blood
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68
Q

What are varicose veins?

A
  • a vein wall becomes weakened, valves may no longer close properly
  • this allows backflow of blood causing vein to become enlarged and bumpy
  • usually happens to surface veins
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69
Q

What does blood consist of?

A

Plasma

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70
Q

What does plasma contain?

A
  • dissolved glucose
  • amino acids
  • mineral ions
  • hormones
  • plasma proteins
  • albumin
  • fibrinogen
  • globulins
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71
Q

What does albumin do in the blood?

A

Important for maintaining the osmotic potential of the blood

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72
Q

What does fibrinogen do in the blood?

A

Important in blood clotting

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73
Q

What does globulin do in the blood?

A

Involved in transport and the immune system

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74
Q

How are platelets carried?

A

By plasma in the blood

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75
Q

What are platelets?

A

Fragments of large cells called megakaryocytes found in the red bone marrow

76
Q

What does blood transport?

A
  • oxygen and CO2
  • digested food
  • nitrogenous waste
  • chemical messages (hormones)
  • food molecules from storage
  • platelets to damaged areas
  • cells and antibodies
77
Q

What roles does the blood do?

A
  • defence
  • thermoregulation
  • maintaining pH of body fkuids
78
Q

What % of the blood is plasma?

A

55%

79
Q

What % of the blood is red blood cells?

A

45%

80
Q

What % of the blood is buffy coat and what does it contain?

A

<1%

Contains white blood cells and platelets

81
Q

Why would you examine a buffy coat?

A

To look for abnormal white blood cells such as a mast cell

82
Q

What is the buffy coat?

A

The fraction of anticoagulated blood that contains most of the white blood cells and platelets following density gradient centrifugation

83
Q

What are the main electrolytes in blood?

A

Sodium, chloride, potassium, magnesium, calcium

84
Q

Why should capillary walls be impermeable?

A

As solutes lower w.p., so should be impermeable as to not lower w.p. of cells, reducing w.p. gradient for diffusion

85
Q

What does albumin do in the blood?

A

give the blood a relatively high solute potential, so low w.p. compared with surrounding fluid

86
Q

What does a low w.p. in blood in capillaries cause to happen?

A

Water moves into the blood from the surrounding fluid by osmosis

87
Q

Define oncotic pressure

A

The tendency of water to move into the blood by osmosis at -3.3kPa

88
Q

What is tissue fluid and how is it formed?

A

Extracellular fluid that comes from substances that leak out of blood capillaries via fenestrations

89
Q

What is the hydrostatic pressure as the blood arrives at the arteriole end of capillaries?

A
  • Hydrostatic pressure forces fluid out of the capillaries (4.6kPa)
  • This is higher than oncotic pressure attracting water in by osmosis
  • so fluid is squeezed out if capillaries
  • new flow out
90
Q

What is the hydrostatic pressure as the blood reaches the venous of the capillary?

A
  • Hydrostatic pressure falls to 2.3kPa in the vessels as fluid moves out and pulse is lost
  • the oncotic pressure is now stronger than hydrostatic
  • so water moves back into capillaries by osmosis
  • net flow in
91
Q

By the time blood returns to the veins, what % of tissue fluid is back in blood vessels

A

90% - the other 10% is used to bathe cells

92
Q

Does oncotic pressure ever change?

A

No remains at -3.3kPa

93
Q

Tissue fluid has what composition?

A

Same as plasma except cells and plasma proteins

94
Q

What happen to the 10% of tissue fluid that leaves the blood vessels?

A

It drains ins or a system of blind-ended tubes called lymph capillaries, where it is known as lymph

95
Q

What is lymph’s composition?

A

Similar to plasma/tissue fluid but has fewer oxygen and nutrients

Lymph also contains fatty acids

96
Q

How does lymph end up with fatty acids in it?

A

They have been absorbed him to the lymph from the villi of the small intestine

97
Q

Name some major lymphatic organs

A

Spleen, tonsils, thymus and adenoids

98
Q

What is the lymphatic systems role?

A
  • immune function
  • absorbing fats from gut
  • lipid transport
  • maintaining viable blood pressure
99
Q

What are the characteristics of lymph capillaries?

A
  • separate from circulatory system
  • closed ends and large pores
  • valves prevent back flow
100
Q

How does lymph return to the blood eventually?

A

Flowing into the right and left subclavian veins (under the collar bone)

101
Q

How is lymph transported in lymph capillaries?

A

By the squeezing of body muscles

102
Q

What would happen in plasma proteins weren’t removed from tissue fluid?

A

They would lower w.p. of the tissue fluid and prevent the reabsorption of water into the blood from capillaries

103
Q

After digestion, where are lipids transported?

A

From the intestines to the blood stream by the lymph system

104
Q

What do lymph nodes do?

A
  • allow lymphocyte to gather
  • intercept bacteria and other debris from lymph which are ingested by phagocytes
  • defence mechanism
105
Q

Where are lymph nodes found?

A

Along lymph vessels

106
Q

What actually IS lymph?

A

A clear fluid that contains white blood cells

107
Q

What do enlarged lymph nodes mean?

A

That the body is fighting off an invading pathogen

108
Q

Why would the loss of the lymphatic system be fatal within a day?

A

It wouldn’t drain excess fluid, so our tissue would swell, blood volume would be lost and pressure would increase

109
Q

The Heart

What is the pericardium?

A

An inelastic double-walled sac containing the heart and the roots of the great vessels

110
Q

The Heart

What is the pericardium’s role?

A
  • creates a closed chamber with sub atmospheric pressure that aids atrial filling and prevents it from distending
  • shields heart by reducing external friction
  • acts as a barrier against infection
111
Q

The Heart

What is the left side of the heart thicker?

A
  • must pump blood at higher pressure over a further distance to whole body
  • has to overcome resistance of aorta and arterial systems of body
112
Q

The Heart

What is the structure of the heart?

A

Inferior / superior vena cava
Right atrium
Tricuspid AV valve
Right ventricle
SL valve
Pulmonary artery
Lungs
Pulmonary vein
Left atrium
Bicuspid AV valve
Left ventricle
SL valve
Aorta

113
Q

The Heart

What does it mean if cardiac muscle is myogenic?

A

It has its own beat - they contract involuntarily

114
Q

The Heart

Why does cardiac muscle have more mitochondria?

A

Cardiac muscle is more reliant on aerobic respiration than skeletal muscle

115
Q

The Heart

Why are cardiac muscle cells branched?

A
  • faster signal propagation
  • contraction in 3 dimensions
116
Q

The Heart

How is cardiac muscle connected?

A

By gap junctions at intercalated discs

117
Q

The Heart

Does heart tissue ever get fatigued?

A

No

118
Q

The Heart

What are the vessels that supply the heart called

A

Coronary artery

119
Q

The Heart

What stops the valves from inverting?

A

Tendons

120
Q

The Heart

How long does each stage of the cardiac cycle take?

A

Atrial systole = 0.1 sec
Ventricular systole = 0.3 secs
Diastole = 0.4 secs

121
Q

The Heart

What is meant by systole and diastole?

A

Systole = contraction
Diastole = relaxtion

122
Q

The Heart

What happens in atrial systole?

A
  • muscle contracts, increasing pressure in ventricles
  • blood flows from atrium to ventricles
  • AV valves open as blood is forced through
  • SL valves shut
123
Q

The Heart

What happens in ventricular systole?

A
  • atrium is relaxed
  • ventricle contracts
  • pressure exceeds atrial pressure
  • both AV valves shut, increasing pressure
  • SL valves open to decrease pressure
124
Q

The Heart

What happens in diastole?

(It’s passive)

A
  • pressure in ventricles decreases
  • as ventricular pressure drops below arterial pressure, SL valves shut
  • all heart muscles relax
  • AV valves open
  • blood pressure increases as blood flows into atria
125
Q

The Heart

What makes the first ‘lubb’ sound of the heart?

A

Closure of AV valves at start of ventricular systole

126
Q

The Heart

What makes the second ‘dupp’ sound?

A

Closure of SL valves at start of ventricular diastole

127
Q

The Heart

What is the septum?

A

The inner dividing wall of the heart preventing the mix of oxygenated and deoxygenated blood

128
Q

The Heart

Pressure changes

When does aortic pressure rise?

A

When ventricles contract as blood is forced into aorta, but it gradually falls again as it moves the blood

The recoil of the elastin produces a temporary rise in pressure at the start of the relaxation phase

Never dropped below 12kPa

129
Q

The Heart

Pressure changes

When does atrial pressure change?

A

It is always relatively low, because the thin walls of the atrium can’t create much force

Highest when atria are contracting but drops when AV valves close and it’s walls relax

Filling of blood increases pressuree

130
Q

The Heart

Pressure changes

When does ventricular pressure change?

A

Low at first but gradually increases as atria contracts

Left AV valves close and pressure rises dramatically due to thick muscle walls

When ventricular pressure is above pressure of aorta, blood is forced past SL valves to aorta

131
Q

The Heart

Pressure changes

How does ventricular volume change?

A

Rises as the atria contract and ventricles fill with blood, but suddenly drops as blood moves into aorta

132
Q

The Heart

What is the bpm of pacemaker cells?

A

60bpm - anything higher has input from the brain

133
Q

The Heart

What do pacemaker cells do?

A

Ensure heart beats in Union

134
Q

The Heart

What does the sino-atrial node do?

A

Sends out a wave of electrical activity (depolarisation) which are propagated throughout the entire atria via gap junctions in the intercalated discs

135
Q

The Heart

What does cardiac muscle do in response to the SAN depolarisation?

A

Cardiac muscle within atrial walls contract almost simultaneously = atrial systole

Forces blood through AV valves

136
Q

The Heart

What does the AVN do?

A

Picks up the wave from SAN but imposes a slight delay before sending its own wave of depolarisation down the Bundle of His into the Purkyne fibres

137
Q

The Heart

Why does the AVN impose a delay on the SAN signal?

A

Delay allows time for ventricles to fill before AV valves close, increasing efficiency

138
Q

The Heart

What happens once the depolarisation has travelled to Purkyne fibres?

A

The ventricular walls contract, starting at the apex and forcing blood up and out of heart to lungs/body

139
Q

The Heart

Why is the refractory period?

A

After every contraction, there’s a period of insensitivity to stimulation to allow the heart to refill passively and prevent fatigure

140
Q

The Heart

What is the recording of electrical activity of the heart called?

A

Electrocardiogram (ECG)

141
Q

The Heart

What does an ECG actually measure?

A

Tiny electrical differences in your skin, which result from electrical activity in the heart

142
Q

The Heart

ECG

What is the P wave?

A

Depolarisation if the atria in response to SAN

143
Q

The Heart

ECG

What is the QRS complex?

A

Depolarisation of the ventricles triggered by the AVN

144
Q

The Heart

ECG

What happens at the PR interval?

A

A delay to allow filling of ventricles

145
Q

The Heart

ECG

What is the ST segment?

A

Blood flows

146
Q

The Heart

ECG

What is the T wave?

A

Repolarisation of the ventricles and the completion of a standard heart beat

147
Q

The Heart

Formula for cardiac output and units

A

Stroke volume x heart rate

cm3/min

148
Q

The Heart

Heart conditions

What is Tachycardia?

A

Elevated rested heart rate (>120bpm)

149
Q

The Heart

Heart conditions

What is Bradycardia?

A

Depressed resting heart rate (<40bpm)

150
Q

The Heart

Heart conditions

What is Arrhythmias?

A

Irregular heart beats

151
Q

The Heart

Heart conditions

What are fibrillations?

A

Unsynchronised contractions of either atria or ventricles leading to dangerous spasmodic heart activity

152
Q

The Heart

Heart conditions

What is an ectopic heart beat?

A

Altered rhythm - an extra beat then a gap

153
Q

How are erythrocytes adapted for their function to carry oxygen?

A
  • biconcave shape = large SA
  • small = fit through capillaries
  • no nuclei = more space for haemoglobin
154
Q

What is haemoglobin?

A

Large, globular, conjugated protein with 4 peptide chains, each with an iron-containing haem prosthetic group

155
Q

What is the reversible reaction to form oxyhaemoglobin?

A

Hb + 4O2 = Hb(O2)4

156
Q

What is positive cooperativity?

A

The binding of oxygen to haemoglobin alters the shape of haemoglobin, making it easier for the next oxygen to hind

157
Q

How many oxygen can bind to haemoglobin?

A

8

158
Q

What happens when the blood reaches body tissues with the concentration of oxygen?

A

Conc of oxygen in cytoplasm of the body cells is lower than in the erythrocytes, so oxygen moves out of the erythrocytes down a gradient

159
Q

Why is oxygen loaded in the lungs?

A

Haemoglobin has a higher affinity for O2 in oxygen rich areas = lungs

This promotes oxygen loading = rapid loading

160
Q

Why is oxygen unloaded in tissues?

A

Haemoglobin will have a lower affinity for O2 in oxygen-starved areas, promoting rapid oxygen unloading

161
Q

What is plotted on an oxygen dissociation curve?

A

The % saturation of oxygen (y-axis)
Oxygen partial pressure (x-axis)

This shows the affinity of Hb for O2

162
Q

What shape is the oxygen dissociation curve for adults?

A

Sigmoidal (S-shaped) due to cooperative binding

163
Q

Why does the dissociation curve level out at higher partial pressures of oxygen?

A

All the haem groups are bound to oxygen and so the haemoglobin is saturated and can’t take up any more

164
Q

Why does a very small change in the partial pressure of oxygen make a significant difference to saturation of Hb?

A

Due to positive cooperativity

165
Q

How much oxygen is released by erythrocytes when you’re not very active?

A

Only about 25% of oxygen is released as the rest acts as a reservoir for when demands increase

166
Q

Different globins

How does foetal haemoglobin differ from adult haemoglobin?

A
  • foetal has a higher affinity for O2
  • because maternal haemoglobin must unload the oxygen at a given partial pressure
  • so the foetal haemoglobin can load it over a diffusion gradient
167
Q

Different globins

What would happen if foetal and adult haemoglobin had the same affinity for O2?

A

Then little to no oxygen would be transferred to the blood of the foetus as there would be no affinity difference

168
Q

Different globins

What is myoglobin?

A

Oxygen-binding molecule in muscles made of a single polypeptide with 1 haem group (so can’t cooperatively bind)

169
Q

Different globins

How does the affinity of myoglobin differ to adult and foetal?

A

Has a higher affinity so curve is to the left

170
Q

Different globins

Why is it important myoglobin has a higher affinity?

A

So it holds oxygen longer, so aerobic respiration occurs, not anaerobic in muscles

171
Q

Different globins

When does myoglobin release oxygen?

A

When oxygen partial pressure falls to reduce the chance of anaerobic respiration

172
Q

What is the Bohr Effect?

A

At lower pH values, Hb gives up oxygen more easily

173
Q

The Bohr Effect

What happens at active tissues?

A
  • higher partial pressure of CO2 and lower pH
  • oxygen given up more readily
174
Q

The Bohr Effect

What happens at the lungs?

A
  • lower partial pressure of CO2
  • oxygen binds more easily
175
Q

The Bohr Effect

Why does the Bohr Effect move the dissociation curve to the right?

A

A decrease in pH shifts the oxygen dissociation curve to the right

176
Q

The Bohr Effect

Why is pH lower at respiring tissues?

A

As partial pressure of CO2 rises, pH decreases due to protons making it more acidic

177
Q

How is CO2 transported in the lungs?

A
  • 5% is carried dissolved in plasma
  • 10-20% is bound to a.a. in haemoglobin to form carbaminohaemoglobin
  • 75-85% is converted into hydrogen carbonate ions in erythrocytes
178
Q

What does CO2 form when it reacts with water?

A

Carbonic acid

179
Q

What does newly formed carbonic acid do?

A

Dissociates to form hydrogen ions and hydrogen carbonate ions

180
Q

What enzyme is in high levels in erythrocytes, catalysing the formation of carbonic acid?

A

Carbonic anhydrase

181
Q

What happens to the negatively charged hydrogen carbonate ions once they’re produced?

A

Move out of the erythrocytes into the plasma by diffusion down grad and negatively charged chloride ions move into erythrocytes = chloride shift

182
Q

Why does the chloride shift occur?

A

To maintain the electrical balance of the erythrocytes

183
Q

Why do erythrocytes remove CO2 and convert it into hydrogen carbonate ions?

A

To maintain a steep conc grad for CO2 to diffuse from the respiring tissues

184
Q

What does HCO3- (hydrogen carbonate ions) do once it has diffused out of erythrocyte in plasma?

A

Combines with sodium to form sodium bicarbonate which travels to the lungs

185
Q

What is the effect of hydrogen ions in an erythrocyte?

A
  • make environment more acidic
  • causes haemoglobin to release O2
  • haemoglobin absorbs H+ ions
  • haemoglobin acts as a buffer
186
Q

What happens when blood reaches the lung tissue with a low conc of CO2?

A

Carbonic anhydrase catalyses the reversible reaction, breaking down carbonic acid into CO2 and water

187
Q

What happens to chloride ions when CO2 diffuses out of erythrocytes?

A

Chloride ions diffuse back into the plasma down an electrochemical gradient

188
Q

How does haemoglobin act as a buffer?

A

Prevents change in pH by accepting free H+ ions in a reversible reaction to form haemoglobinic acid

A-level Biology (23 decks)

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