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Yr 12 Biology A Level > Transport in animals > Flashcards

Transport in animals Flashcards

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1
Q

Why do multicellular organisms require transport systems?

A

High metabolic demands
- Diffusion over long distances not fast enough

Small SA:V ratio
- Not enough surface available to absorb sufficient amount of
substances

Hormones and enzymes needed in different region to where they’re made

Waste products need to be removed from cells and transported to excretory organs

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2
Q

Describe the differences between an open and closed circulatory system

A

Open:
- Few transport vessels
- Haemolymph instead of blood - Doesn’t carry oxygen or carbon dioxide
- Haemolymph pumped straight from heart into body cavity at low pressure - Comes into direct contact with cells
- e.g. insects

Closed:
- Blood enclosed in blood vessels (e.g. veins, arteries)
- Does not come into direct contact with cells of body
- Heart pumps blood through vessels under high pressure
- Substances leave and enter blood by diffusion
- Blood flow can be diverted
- e.g. mammals

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3
Q

Describe the differences between a single and double circulatory system

A

Single:
- Blood passes through the heart once for each circuit of the body
- Passes through two sets of capillaries
- Oxygen and carbon dioxide exchanged in the first
- Nutrients and gasses exchanged with cells in the second
- e.g. fish

Double
- Blood flows twice through the heart for every once around the body
- Pulmonary circulation (heart - lungs - heart)
- Systemic circulation (heart - body - heart)
- e.g. mammals

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4
Q

Describe the structure and function of arteries

A

Structure:
- Three layers in their walls
- Thick smooth muscle and elastic fibre walls to withstand high pressures
- Narrow lumen to maintain high pressure

Function:
- Carry blood at high pressure from the ventricles of the heart to tissues of body

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5
Q

Describe the structure and function of veins

A

Structure:
- Three layers in their walls
- Thin smooth muscle and elastic fibre walls allows them to be pressed flat by muscles to carry blood under low pressure
- Valves to prevent backflow of blood
- Wide lumen for slow flowing blood

Function:
- Carry blood at low pressure
from the tissues of body to the atria of the heart

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6
Q

Describe the structure and function of capillaries

A

Structure:
- Single layer of endothelium
- Very narrow lumen
- Permeable walls

Function:
- Carry blood through tissues
- Exchange of materials between cells in the tissue and the blood in the capillary

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7
Q

What is the role of elastic fibres?

A
  • Composed of elastin
  • Can stretch and recoil - make vessel walls flexible
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8
Q

What is the role of smooth muscle?

A

Contracts and relaxes - changes size of lumen

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9
Q

What is the role of collagen?

A

Provides structural support for vessels

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10
Q

Why do artery walls require elastic fibres?

A
  • Withstand force of blood pumped out of heart
  • Stretch to take large volume of blood
  • Recoil evens out surges of blood pumped from heart
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11
Q

Describe and explain how the wall of an artery is adapted both to withstand and maintain high hydrostatic pressure

A

To withstand pressure:
- Wall is thick and contains collagen - Provides strength
- Endothelium is folded - No damage to endothelium as it stretches

To maintain pressure:
- Thick layer of elastic fibres - Cause recoil to return to original size
- Thick layer of smooth muscle - Narrows lumen

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12
Q

Why is the lining of arteries smooth?

A

Allow blood to flow easily

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13
Q

What links arteries and capillaries?

A

Arterioles

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14
Q

How does the structure of arterioles differ to that of arteries?

A
  • Arterioles have more smooth muscle, less elastic fibre
  • Muscle can control blood flow to organs
  • Smaller lumen
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15
Q

What is the function of capillaries?

A

Exchange of substances

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16
Q

How are capillaries adapted to their function?

A
  • Large surface area for diffusion - slows blood down to give more time for exchange
  • Narrow lumen - red blood cells pass through one at a time - Slows blood down to give more time for exchange
  • Walls are one endothelial thick - Short diffusion pathway
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17
Q

What links capillaries to veins?

A

Venules

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18
Q

Describe the structure of venules

A
  • Very thin walls with little smooth muscle - allows blood to flow into veins
  • Do not have valves so cannot control blood flow
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19
Q

How are veins adapted to their function?

A
  • Valves prevent backflow of blood
  • Run between muscles - Contractions squeeze veins, forcing blood towards heart
  • Smooth endothelial lining to allow blood to flow easily
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20
Q

Why do veins require valves?

A
  • Blood under much lower pressure than in arteries
  • No pumping from heart and little elastic recoil in veins - Blood might flow backwards as it moves towards heart against gravity
  • Valves prevent backflow - open as blood flows towards heart and close if it flows in
    opposite direction
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21
Q

Why do arteries require thicker walls than veins?

A

Blood flows at higher pressure through arteries

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22
Q

List the components of the blood

A
  • Red blood cells - transports oxygen
  • White blood cells - engulf and destroy pathogens
  • Plasma - liquid that transports all other components of the blood
  • Proteins - maintain osmotic potential of the blood
  • Platelets - involved in blood clotting
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23
Q

What substances are transported by the blood?

A
  • Oxygen to respiring cells
  • Carbon dioxide away from respiring cells
  • Digested food e.g. glucose, amino acids
  • Nitrogenous waste e.g. urea
  • Hormones
  • Antibodies
  • Platelets
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24
Q

Define tissue fluid

A

The fluid forced out of blood into surrounding space around cells

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25
Q

What is the role of tissue fluid?

A
  • Deliver oxygen to respiring cells
  • Remove carbon dioxide from respiring cells
  • Deliver amino acids, glucose, hormones to cells
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26
Q

What feature of capillaries allows tissue fluid to form?

A

Small gaps between epithelial cells

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27
Q

Which components of the blood cannot be forced out of capillaries?

A
  • Red blood cells
  • Most white blood cells
  • Plasma proteins
  • All other substances dissolved in plasma can pass through gaps
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28
Q

Define hydrostatic pressure

A
  • The pressure from heart beat
  • Forces liquid out through gaps between cells of capillary linings
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29
Q

Define oncotic pressure

A

Tendency of water to move from a region of high water potential to a region of low water potential

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30
Q

Explain how hydrostatic and oncotic pressure affect the movement of fluids into and out of
capillaries

A
  • Hydrostatic pressure forces liquid out of capillaries
  • Hydrostatic pressure (4.6kPa) higher than oncotic pressure (-3.3KPa) at arterial end of
    capillary
  • Water forced out of capillary and forms tissue fluid
  • As blood moves along capillary more fluid moves out
  • Hydrostatic pressure decreases
  • By venous end of capillaries hydrostatic pressure falls to 2.3kPa
  • Oncotic pressure remains at -3.3kPa throughout
  • Plasma proteins too large to leave capillary so water potential remains constant
  • Water moves back into capillary by osmosis at venous end
  • Around 90% of tissue fluid moves back into capillaries
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31
Q

Define lymph

A

10 % of tissue fluid that does not return to capillaries

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32
Q

Describe the lymph system

A
  • Lymph vessels
  • Valves prevent backflow
  • Lymph nodes - contain lots of lymphocytes
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33
Q

Where does lymph return to the blood?

A

Subclavian veins

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34
Q

What is the source of fatty acids in lymph?

A
  • Absorption from small intestine
  • Fatty acids move into lacteals, then into lymph system
35
Q

What is the role of lymph nodes?

A
  • Contain lots of lymphocytes
  • Produce antibodies when pathogens detected
  • Antibodies pass into blood
36
Q

Describe the structure of heart

A
  • Left and right side separated by the septum
  • Oxygenated blood flows through left side
  • Deoxygenated blood flows through right side
  • 4 chambers: left atrium, left ventricle, right atrium, right ventricle
  • Oxygenated blood enters left atrium via pulmonary vein from the lungs
  • Oxygenated blood leaves left ventricle via aorta to travel to rest of the body
  • Deoxygenated blood returns to heart in the right atrium via the vena cava
  • Deoxygenated blood leaves the heart at the right ventricle via the pulmonary artery
37
Q

Which vessel carries deoxygenated blood away from the heart?

A
  • Pulmonary artery
  • Takes blood to lungs
38
Q

In which blood vessel connected to the heart does blood have the lowest carbon dioxide
concentration?

A

Pulmonary vein

39
Q

Explain why the wall of the left ventricle is thicker than the wall of the right ventricle

A
  • Left ventricle requires more muscle to create more force
  • Needs to create higher pressure
  • To pump blood further (to all parts of body)
  • Right ventricle only pumping blood to lungs
40
Q

Explain why ventricles have thicker walls than the atria

A
  • Atria receive blood with lower pressure
  • Have only a short distance to pump the blood - into the ventricle
  • Ventricles have to contract strongly to pump high pressure blood to lungs or rest of body
41
Q

What is the role of the valves in the heart?

A
  • Prevent blood flowing backwards
  • Valve tendons prevent inversion
42
Q

What is the function of the coronary arteries?

A

Carry oxygenated blood to heart muscles

43
Q

How do coronary arteries maintain a regular heart rhythm?

A
  • Coronary arteries supply blood carrying glucose and oxygen to heart
  • Heart cardiac muscles require oxygen and glucose for respiration
  • ATP from respiration needed to contract muscle with regular rhythm
44
Q

Describe the structure of cardiac muscle

A
  • Myogenic - can contract automatically
  • Cardiac arteries - supply oxygen and nutrients to the heart
  • Valves prevent backflow of blood
45
Q

What causes heart ventricles to fill with blood?

A

Atrial contraction

46
Q

Describe the cardiac cycle

A

Atrial systole
- Walls of atria contract
- Blood forced from the atria into the ventricles via the atrioventricular valves
- Semilunar valves close

Ventricular systole
- Walls of ventricles contract
- Atrioventricular valves close, semilunar valves open
- Blood empties into the arteries
- Atria start to refill

Diastole
- Ventricles stop contracting, pressure falls
- Semilunar valves close, preventing backflow from the arteries
- When ventricular pressure drops below atrial pressure, atrioventricular valves open
- Blood entering atria flows into ventricles

47
Q

What is the sinoatrial node (SAN)?

A
  • Group of specialised muscle cells in wall of right atrium
  • Can trigger impulses without direction from the brain (myogenic)
  • Causes cardiac muscle to contract
  • Acts as pacemaker
48
Q

How is a heart beat initiated?

A
  • SAN sends out electrical impulse that stimulates contraction of atrial muscle
  • Impulse also stimulates the atrioventricular node (AV node)
  • AV node delays impulse
  • AV node sends impulses down septum via Bundle of His
  • Bundle of His stimulates Purkyne fibres in ventricular wall, causing ventricular contraction
    from apex
49
Q

Explain why the excitation wave is carried to the apex by the Purkyne fibre

A
  • So ventricular contraction starts at bottom (apex)
  • Pushes blood upwards into arteries
50
Q

Explain how pressure changes in the heart bring about the closure of the atrioventricular (bicuspid) valve

A
  • Ventricular systole raises ventricular pressure
  • Ventricular pressure higher than atrial pressure
  • Valve tendons prevent inversion
51
Q

Why does the aortic pressure remain high throughout the cardiac cycle?

A

Thick muscle and elastic fibres in the artery wall

52
Q

Define cardiac output

A

Volume of blood the heart pumps per minute

53
Q

Define stroke volume

A

Volume of blood pumped from the left ventricle per beat

54
Q

Define heart rate

A

Number of beats per minute

55
Q

How is cardiac output calculated?

A

Cardiac output = stroke volume x heart rate

56
Q

Explain what causes the fluctuations in blood pressure along the aorta

A
  • Systole (contraction of left ventricle) increases pressure
  • Diastole decreases pressure
57
Q

Describe the pressure changes in the blood as it flows through the circulatory system from the aorta to the veins

A
  • Pressure drops as distance from heart increases
  • Greatest pressure drop while blood is in the arteries
  • Pressure constant in veins
  • No fluctuation in capillaries and veins
58
Q

Explain what causes the overall change in pressure as blood flows from the aorta to the arteries to the capillaries

A
  • Blood flows into larger number of vessels
  • Total cross-sectional area of arteries greater than aorta
  • Total cross-sectional area of capillaries greater than arteries
59
Q

What are electrocardiograms (ECG) used for?

A
  • Measure electrical differences in skin
  • Equivalent to electrical activity of heart
  • Can help diagnose heart problems
60
Q

What is the role of erythrocytes (red blood cells)?

A

Transport oxygen around the body

61
Q

What is haemoglobin (Hb)?

A
  • Pigment in red blood cells
  • Globular protein
  • Made from 4 polypeptide chains
  • Each chain has haem prosthetic group
  • Contains iron
  • Oxygen binds to haemoglobin
62
Q

How does oxyhaemoglobin form?

A

Haemoglobin + oxygen ⇌ oxyhaemoglobin

63
Q

Define partial pressure

A

The contributing pressure of a single gas to the total pressure of a mixture of gases

64
Q

Describe the movement of oxygen in the lungs

A
  • High partial pressure of oxygen (pO2) in alveoli
  • Lower partial pressure of oxygen (pO2) in blood in capillaries
  • Oxygen diffuses from alveoli to blood
65
Q

Describe the movement of oxygen at respiring tissues

A
  • High partial pressure of oxygen (pO2) in blood
  • Lower partial pressure of oxygen (pO2) in respiring tissues
  • Oxygen diffuses from blood to respiring cells
66
Q

Describe the role of haemoglobin in transporting oxygen around the body

A
  • Haemoglobin has high affinity for oxygen
  • Oxygen binds to haemoglobin in lungs (high pO2)
  • Oxyhaemoglobin formed
  • Oxygen released in tissues where respiration is occurring (low pO2)
67
Q

Explain how the binding of one oxygen molecule to a haem group affects haemoglobin

A
  • Binding of first oxygen molecule causes change
  • Tertiary structure of haemoglobin alters
  • Affinity for oxygen increases
  • Becomes easier for next oxygen molecules to bind
68
Q

Explain how the removal of the first oxygen at respiring tissues affects haemoglobin

A
  • Removal of first oxygen molecule causes change
  • Tertiary structure of haemoglobin alters
  • Affinity for oxygen decreases
  • Becomes easier for next oxygen molecules to leave
69
Q

Explain the significance of the oxygen dissociation curve

A
  • High pO2 in lungs
  • Haemoglobin rapidly loaded with oxygen
  • Relative small drop in pO2 at respiring tissues leads to rapid dissociation of oxygen
  • Oxygen free to diffuse into cells
70
Q

Describe the difference in oxygen affinity between fetal haemoglobin and adult haemoglobin

A

Fetal haemoglobin has higher affinity for oxygen

71
Q

Explain why the fetal haemoglobin curve is to the left of the adult haemoglobin curve

A
  • Placenta has low pO2
  • Adult haemoglobin will release O2 at placenta
  • Fetal haemoglobin has higher affinity for oxygen at low pO2
  • Fetal haemoglobin is able to take up oxygen in placenta
72
Q

List the three ways that CO2 is transported in the blood

A
  • 5% dissolves in blood plasma
  • 10-20% combines with haemoglobin - Forms carbaminohaemoglobin
  • 75-85% converted into hydrogen carbonate ions (HCO3-) - Occurs in cytoplasm of red blood cells
73
Q

Which enzyme catalyses the production of hydrogen carbonate ions?

A

Carbonic anhydrase

74
Q

Describe how hydrogencarbonate ions are produced in the erythrocytes

A
  • Carbon dioxide diffuses into erythrocytes
  • Reacts with water
  • Reaction catalysed by carbonic anhydrase
  • Forms carbonic acid (H2CO3)
  • Carbonic acid dissociates to form hydrogencarbonate ions and hydrogen ions
75
Q

Give the equation for the conversion of CO2 into HCO3-

A

CO2 + H2O ⇌ H2CO3 ⇌ H+
+ HCO3-

76
Q

What happens to hydrogen carbonate ions after they have been produced?

A
  • Diffuse down concentration gradient
  • Into plasma
77
Q

What is the chloride shift?

A
  • Movement of Cl-
    ions into erythrocytes
  • To maintain electrical balance
  • Due to hydrogen carbonate ions leaving
78
Q

What happens to hydrogen carbonate ions at the lungs?

A
  • Low pCO2 at lungs
  • HCO3- diffuses back into erythrocytes
  • React with H+ to form H2CO3
  • Carbonic anhydrase catalyses conversion of H2CO3 back into water and CO2
  • CO2 diffuses out of blood into lungs
  • Cl- ions diffuse out of erythrocytes into plasma
79
Q

How does haemoglobin act as a buffer?

A
  • Prevents changes in pH
  • Accepts 3 H+ ions
  • To form haemoglobinic acid
80
Q

What effect does carbon dioxide have on haemoglobin?

A

At higher pCO2 haemoglobin gives up oxygen more easily - reduces affinity for oxygen

81
Q

Why is the Bohr effect important?

A
  • Actively respiring tissues have high pCO2
  • Haemoglobin gives up oxygen more easily
  • Lungs have a lower pCO2
  • Haemoglobin binds to oxygen more easily
82
Q

Outline the benefits of the Bohr shift to actively respiring tissue

A
  • Actively respiring tissue requires more oxygen for aerobic respiration
  • Actively respiring tissue produces more CO2
  • Haemoglobin involved in transport of CO2
  • Less haemoglobin available to combine with O2
  • Bohr shift causes more oxygen to be released
83
Q

What effect does pH have on Hb’s affinity for oxygen?

A

Affinity decreases as pH decreases (H+ concentration increases)

84
Q

Explain why the Bohr shift occurs

A
  • High concentration of CO2 in blood reduces affinity of Hb for oxygen
  • Hydrogen ions interact with haemoglobin to form haemoglobinic acid
  • Hb provides buffering effect
  • H+ displaces O2 in haemoglobin
  • More oxygen released where more respiration occurring

Yr 12 Biology A Level (15 decks)

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