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Biology > Mass transport in animals and plants > Flashcards

Mass transport in animals and plants Flashcards

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1
Q

What protein structure does haemoglobin have?

A

Quaternary - 4 polypeptide chains each containing a haem group, globular protein

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2
Q

What is the equation for when haemoglobin is loaded with oxygen?

A

Haemoglobin (Hb) + oxygen (O2) -> oxyhemoglobin (HbO8)

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3
Q

What are the names for attachment and detachment of O2?

A

loading/unloading
association/dissociation

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4
Q

What is the difference between high and low affinity haemoglobin?

A

high affinity = oxygen is taken up more easily but released less readily

low affinity = oxygen is taken up less easily but released more readily

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5
Q

What is the role of haemoglobin?

A

Due to the 4 haem (Fe2+) groups, haemoglobin is able to bind to 4 oxygen molecules to form oxyhemoglobin

  • it will readily associate with oxygen at the surface where gas exchange takes place
  • readily dissociate from oxygen at the tissues requiring it
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6
Q

Why do different haemoglobin have different affinities for oxygen?

A

slightly different tertiary and quaternary structure and hence different oxygen binding properties

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7
Q

Explain the shape of an oxygen dissociation curve?

A
  • the shape of haemoglobin makes it difficult for the first oxygen molecule to bind so initially a shallow gradient
  • binding of the first oxygen molecule changes the quaternary structure of the haemoglobin, making it easier for the other subunits to bind to O2
  • graph flattens off when 3 binding sites are occupied because it is less likely that a single O2 molecule will find an empty site to bind to
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8
Q

What do oxygen dissociation curves show?

A

Oxygen affinity

  • the further to the left, the greater the oxygen affinity (during rest)
  • the further to the right, the lower the oxygen affinity (during exercise)
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9
Q

What is the effect of CO2 on oxygen affinity?

A
  • haemoglobin has reduced affinity for oxygen in the presence of carbon dioxide, so reduces oxygen more readily

eg. in muscles, CO2 concentration is high during respiration. This reduces oxygen affinity so it can be more readily released for respiration

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10
Q

How does pH help to load and unload oxygen?

A
  • at the gas exchange surface, CO2 is constantly removed
  • pH is slightly raised due to low CO2 concentration
  • higher pH changes the shape of haemoglobin into one that enables it to load oxygen more readily
  • in tissues, CO2 is produced by respiring cells
  • CO2 is acidic in solution, so pH of blood within the tissues is lowered
  • lower pH changes the shape of haemoglobin into one with a lower affinity for oxygen
  • haemoglobin releases oxygen to respiring tissues
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11
Q

How is more oxygen produced during respiration due to affinity?

A
  • the higher rate of respiration
  • the more CO2 produced by tissues
  • the lower the pH
  • the greater the shape change of haemoglobin
  • the more readily oxygen is unloaded
  • the more oxygen is available for respiration

(known as the Bohr effect)

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12
Q

How is oxygen affinity different for insects and llamas?

A
  • insects have a very rapid rate of respiration and high metabolism, and so dissociation curve lies to the right of humans due to low O2 affinity
  • llamas live at high altitudes with low atmospheric pressure, so partial pressure of oxygen is lower. It is therefore more difficult to load haemoglobin with oxygen so the dissociation curve lies to the left of humans, with a much higher O2 affinity
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13
Q

Why must blood pass through the heart twice in one circuit?

A
  • when blood passes through the lungs, the pressure is reduced. If it were to pass immediately through to the body, the low pressure would make circulation very slow. Blood is therefore returned to the heart to boost its pressure before being circulated to the rest of the tissues
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14
Q

What is the pathway taken by a RBC from the vena cava to the body?

A

vena cava, right atrium, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, left ventricle, aorta, body

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15
Q

Why does the left ventricle have a thicker muscle wall?

A

it must contract to create enough pressure to pump blood around the rest of the body

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16
Q

Which valves are between the atria and ventricles, and what is their purpose?

A

Left and right atrioventricular valves, prevent back flow of blood

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17
Q

Which side of the heart does oxygenated blood pass through?

A

Left

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18
Q

What are the 3 stages of the cardiac cycle?

A
  • diastole
  • atrial systole
  • ventricular systole
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19
Q

What happens during diastole?

A

Relaxation of the heart

Blood enters atria and ventricles from pulmonary veins and vena cava. As atria fills, pressure rises causing atrioventricular valves to open and blood to flow into ventricles. Pressure is lower in ventricles than in the aorta and pulmonary artery, so semi-lunar valves close. Atria and ventricles are relaxed

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20
Q

What happens during atrial systole?

A

Contraction of the atria

Contraction of atrial walls and recoil of ventricle walls forces the remaining blood into ventricles from the atria. The ventricle muscles remain relaxed

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21
Q

What happens during ventricular systole?

A

Contraction of ventricles

Ventricle walls contract once filled with blood and this increases blood pressure, forcing shut AV valves to prevent back flow into atria. This causes the pressure in ventricles to be higher than in the aorta and pulmonary artery, so blood is forced into these vessels.

22
Q

What is the sequence of events that control the cardiac cycle?

A
  • deoxygenated blood enters the right atrium via the vena cava
  • right atrium contracts and blood is forced into right ventricle through the AV valve
  • right ventricle contracts and blood is pumped into pulmonary artery
  • blood transported to lungs where CO2 diffuses out and O2 diffuses in
  • oxygenated, low pressure blood returns to the heart via the pulmonary vein and enters left atrium
  • left atrium contracts and blood is forced into left ventricle through AV valve
  • left ventricle contracts and blood is forced under high pressure into aorta, where it is transported around the rest of the body
23
Q

What is cardiac output?

A

Volume of blood pumped by one ventricle of the heart in one minute

24
Q

Equation for cardiac output?

A

cardiac output = heart rate x stroke volume (volume of blood pumped out per beat)

25
Q

What is the structure of arteries?

A

Carry the blood away from the heart and into arterioles

  • thick outer wall which prevents bursting under high pressure
  • thick muscle and elastic tissue so can be constricted or dilated to control volume of blood passing through,
  • narrow lumen
  • smooth to reduce friction for smooth blood flow
26
Q

What is the structure of veins?

A

Carry blood from capillaries back to the heart

  • less muscle and elastic because blood is at lower pressure
  • wider lumen
  • valves to prevent back flow
27
Q

What is the structure of capillaries?

A

Vessels linking arterioles to veins

  • 1 cell thick for rapid diffusion between blood and cells
  • very narrow lumen to reduce diffusion distance
  • large surface area for exchange
28
Q

What are arterioles?

A

small arteries controlling blood flow from arteries to capillaries

29
Q

What is the role of tissue fluid?

A

a watery liquid containing glucose, amino acids, fatty acids, ions and oxygen (dissolved in water). Tissue fluid flows over cells and supplies these substances to the tissues, and removes CO2 and other waste materials through diffusion

30
Q

How does water move out through the stomata?

A

Humidity of the atmosphere is lower than the air space next to the stomata. As a result, there is a water potential gradient causing water to diffuse out into the surrounding air

31
Q

How does water move up the stem in the xylem?

A
  • Water lost from leaf because of transpiration / evaporation of water through stomata from leaves
  • Lowers water potential of leaf cells
  • Water pulled up xylem (creating tension) and water molecules ‘stick’ together by hydrogen bonds (forming continuous) water column
  • Adhesion of water (molecules) to walls of xylem
32
Q

What factors affect the rate of transpiration?

A
  • temperature - higher temperature = higher kinetic energy
  • air movement - wind = steeper water potential gradient
  • light energy - high light energy = stomata forced open
  • humidity - low humidity = higher water potential gradient
33
Q

What variables are found on an oxygen dissociation curve graph?

A
  • partial pressure of oxygen
  • oxygen saturation of haemoglobin
34
Q

Which sides of the body does de/oxygenated blood pass through?

A

oxygenated = left
deoxygenated = right

35
Q

Which valves are found between the atria and ventricles?

A

left and right atrioventricular valves

36
Q

Where do ventricles pump blood?

A

away from the heart and into arteries

37
Q

Where do atria receive blood from?

A

veins

38
Q

What is the aorta?

A

connected to the left ventricle and carries oxygenated blood to all parts of the body except the lungs

39
Q

What is the vena cava?

A

connected to the right atrium and brings deoxygenated blood back from body tissues (except the lungs)

40
Q

What is the pulmonary artery?

A

connected to the right ventricle and carries deoxygenated blood to the lungs where o2 is replenished

41
Q

What is the pulmonary vein?

A

connected to the left atrium and brings oxygenated blood back from the lungs

42
Q

Where are semi-lunar valves located?

A

between ventricles and major arteries (pulmonary artery and aorta)

43
Q

How does a heart attack (myocardial infarction) occur?

A

coronary arteries become blocked leading to a deprivation of blood and oxygen to the heart muscle. Therefore muscle cells are unable to respire and die

44
Q

How is tissue fluid formed?

A
  • Pumping of the blood by the heart creates hydrostatic pressure at the arterial ends of capillaries
  • This causes tissue fluid to move out of blood plasma
  • The outward pressure is opposed by: hydrostatic pressure of tissue fluid outside of capillaries, and the lower water potential of the blood (due to plasma proteins that cause water to move back into blood in capillaries)
  • However the combined effect of forces creates an overall pressure that pushes tissue fluid out of capillaries at the arterial end
  • The pressure is only enough to force out small molecules - larger cells and proteins are too large to cross the membrane. This is called ultrafiltration
45
Q

What happens to tissue fluid once it has exchanged materials?

A

returns to the circulatory system. Most is returned to the blood plasma directly via capillaries

46
Q

How is tissue fluid returned to the circulatory system?

A
  • loss of tissue fluid from capillaries reduces hydrostatic pressure inside them
  • as a result, once blood reaches the venous end of capillaries, hydrostatic pressure is usually lower than that of the tissue fluid outside of it
  • tissue fluid is forced back into capillaries by higher hydrostatic pressure outside them
  • in addition, plasma has lost water and still contains proteins therefore has a lower water potential than tissue fluid, so water leaves by osmosis
  • the remainder of tissue fluid is carried back via the lymphatic system where it is drained back into the bloodstream
47
Q

How is the contents of the lymphatic system moved?

A
  • hydrostatic pressure of tissue fluid
  • contraction of body muscles
48
Q

How is water from tissue fluid returned to the circulatory system?

A

Plasma proteins remain which creates a water potential gradient. Water moves into the blood by osmosis and is returned via the lymphatic system

49
Q

Describe the mass flow hypothesis for the mechanism of translocation in plants

A
  • Glucose is converted to sucrose as it is more soluble
  • Sugars (sucrose) are actively transported into the phloem in the leaves by companion cells
  • Lowers water potential of sieve cell and water enters by osmosis
  • Increase in pressure causes mass movement towards the root
  • Sugars used / converted in root for respiration for storage.
50
Q

What factors affect oxygen-haemoglobin binding?

A
  • partial pressure of oxygen - as partial pressure increases, affinity increases
  • partial pressure of carbon dioxide - as partial pressure increases, affinity decreases because conditions become more acidic which changes the quaternary structure of haemoglobin
  • saturation of haemoglobin with oxygen - hard for the first oxygen to bind but once it does, the quaternary shape changes so it is easier for the second and third oxygen to bind. It is harder for the fourth to bind because there is a low chance of finding a binding site
51
Q

Why does oxygen bind to haemoglobin in the lungs?

A
  • high partial pressure of oxygen - high affinity
  • low carbon dioxide concentration - high affinity
52
Q

How does sucrose in the leaf move into the phloem? How is sucrose then transported around the plant?

A
  • Sucrose enters companion cells of the phloem vessels by active transport which requires ATP and a diffusion gradient of hydrogen ions. Sucrose then diffuses from companion cells into the sieve tube elements through the plasmodesmata
  • As sucrose moves into the tube elements, water potential inside the phloem is reduced, causing water to enter via the xylem which increases hydrostatic pressure. Water moves along the sieve tubes to areas with lower hydrostatic pressure and sucrose diffuses into the surrounding cells

Biology (24 decks)

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