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Biology: 3.3 Exchange of Substances > 3.4 Mass Transport > Flashcards

3.4 Mass Transport Flashcards

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1
Q

Structure of haemoglobin

A

Globular, water soluble. Consists of four polypeptide chains, each carrying a haem group (quaternary structure).

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2
Q

Role of haemoglobin

A

Present in red blood cells. Oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues.

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3
Q

3 factors affecting oxygen-haemoglobin binding

A
  1. Partial pressure/concentration of oxygen.
  2. Partial pressure/concentration of carbon dioxide.
  3. Saturation of haemoglobin with oxygen.
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4
Q

What happens to the affinity of haemoglobin for oxygen as partial pressure of oxygen increases?

A

The affinity of haemoglobin for oxygen increases.

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5
Q

What occurs when the partial pressure of oxygen is low?

A

Oxygen is released from haemoglobin.

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6
Q

What is the relationship between partial pressure of oxygen and how tightly oxygen binds to haemoglobin?

A

As partial pressure of oxygen increases, oxygen binds more tightly to haemoglobin.

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7
Q

What happens to haemoglobin as the partial pressure of carbon dioxide increases?

A

Haemoglobin changes shape.

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8
Q

How does increased partial pressure of carbon dioxide affect the acidity of the conditions?

A

It causes the conditions to become acidic.

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9
Q

What is the effect of increased acidity on the affinity of haemoglobin for oxygen?

A

The affinity of haemoglobin for oxygen decreases.

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10
Q

What is released from haemoglobin as a result of increased partial pressure of carbon dioxide?

A

Oxygen is released from haemoglobin.

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11
Q

What is the phenomenon called when increased carbon dioxide partial pressure leads to decreased oxygen affinity in haemoglobin?

A

The Bohr effect.

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12
Q

What is the effect of the first oxygen molecule binding to hemoglobin?

A

It is hard for the first oxygen molecule to bind.

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13
Q

What is positive cooperativity in hemoglobin?

A

Once the first oxygen molecule binds, it changes the shape of hemoglobin to make it easier for the second and third molecules to bind.

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14
Q

Why is it slightly harder for the fourth oxygen molecule to bind to hemoglobin?

A

There is a low chance of finding a binding site.

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15
Q

Why oxygen binds to haemoglobin in the lungs

A
  • Partial pressure of oxygen is high.
  • Low concentration of carbon dioxide in the lungs, so affinity is high.
  • Positive cooperativity (after the first oxygen molecule binds, binding of subsequent molecules is easier).
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16
Q

Why oxygen is released from haemoglobin in respiring tissues

A
  • Partial pressure of oxygen is low.
  • High concentration of carbon dioxide in respiring tissues, so affinity decreases.
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17
Q

What do oxyhaemoglobin dissociation curves plot?

A

Saturation of haemoglobin with oxygen (in %) against partial pressure of oxygen (in kPa).

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18
Q

What does a curve further to the left on an oxyhaemoglobin dissociation curve indicate?

A

Haemoglobin has a higher affinity for oxygen.

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19
Q

Effect of carbon dioxide on oxyhaemoglobin dissociation curve

A

Curve shifts to the right because haemoglobin’s affinity for oxygen has decreased.

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20
Q

What is the suitable medium for transport in a mammalian circulatory system?

A

Water-based to allow substances to dissolve.

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21
Q

What organ is responsible for moving the transport medium in a mammalian circulatory system?

A

The heart.

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22
Q

What is the purpose of valves in a mammalian circulatory system?

A

To control flow so it remains unidirectional.

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23
Q

What are the characteristics of the atria in the heart?

A

The atria are thin-walled and elastic, allowing them to stretch when filled with blood.

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24
Q

What are the characteristics of the ventricles in the heart?

A

The ventricles have thick muscular walls that pump blood under high pressure.

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25
Why is the left ventricle thicker than the right ventricle?
The left ventricle is thicker because it has to pump blood all the way around the body.
26
What is the structure of arteries?
Arteries have thick walls to handle high pressure, and are muscular and elastic to control blood flow.
27
What is the structure of veins?
Veins have thin walls due to lower pressure and require valves to prevent backflow.
28
Why do veins have less muscular and elastic tissue compared to arteries?
Veins do not need to control blood flow as they operate under lower pressure.
29
Why does the heart need two pumps?
To maintain blood pressure around the whole body.
30
What happens to blood pressure when blood passes through the narrow capillaries of the lungs?
The pressure drops sharply.
31
What is the consequence of low blood pressure in the lungs?
Blood would not be flowing strongly enough to continue around the whole body.
32
What does the heart do to increase blood pressure after it drops in the lungs?
It returns blood to the heart to increase the pressure.
33
What happens during cardiac diastole
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atrioventricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valves remain closed.
34
What happens during atrial systole
The atria contract, pushing any remaining blood into the ventricles.
35
What happens during ventricular systole?
The ventricles contract.
36
What occurs to the pressure in the ventricles during systole?
The pressure increases.
37
What happens to the atrioventricular valves during ventricular systole?
They close to prevent backflow.
38
What happens to the semilunar valves during ventricular systole?
They open.
39
Where does blood flow during ventricular systole?
Into the arteries.
40
Where is sinoatrial node (SAN) located?
Located in the wall of the right atrium.
41
Where is atrioventricular node (AVN) located?
Situated in between the two atria.
42
What does myogenic mean?
The heart's contraction is initiated from within the muscle itself, rather than by nerve impulses.
43
What initiates the heart contraction process?
SAN (Sinoatrial Node)
44
What does the SAN do during heart contraction?
It initiates and spreads the impulse across the atria, causing them to contract.
45
What role does the AVN (Atrioventricular Node) play in heart contraction?
It receives, delays, and then conveys the impulse down the bundle of His.
46
How does the impulse travel after the bundle of His?
It travels into the Purkinje fibres which branch across the ventricles.
47
How do the ventricles contract during the heart contraction process?
They contract from the bottom up.
48
What happens if the impulse spreads straight from the atria into the ventricles?
There would not be enough time for all the blood to pass through and for the valves to close.
49
Why is there a delay in the impulse from the atria to the ventricles?
To allow enough time for all the blood to pass through and for the valves to close.
50
What is the thickness of capillary walls?
Walls are only one cell thick.
51
What is the benefit of capillary walls being one cell thick?
It provides a short diffusion pathway.
52
Why are capillaries narrow?
They are very narrow, allowing them to permeate tissues and enabling red blood cells to lie flat against the wall.
53
What is the function of capillaries in delivering oxygen?
They effectively deliver oxygen to tissues.
54
What is a characteristic of capillary networks?
They are numerous and highly branched, providing a large surface area.
55
What is tissue fluid?
A watery substance containing glucose, amino acids, oxygen, and other nutrients.
56
What does tissue fluid supply to the cells?
Glucose, amino acids, oxygen, and other nutrients.
57
What does tissue fluid remove from the cells?
Waste materials.
58
What creates hydrostatic pressure in blood vessels?
The pumping of blood through increasingly small vessels.
59
What happens to fluid as hydrostatic pressure forces it out of the capillaries?
It bathes the cells.
60
When does fluid return to the capillaries?
When the hydrostatic pressure is low enough.
61
How is water transported in plants?
Through xylem vessels; long, continuous columns that also provide structural support to the stem.
62
What is cohesion in the context of water molecules?
Cohesion refers to water molecules forming hydrogen bonds with each other, causing them to 'stick' together.
63
What role does surface tension play in water cohesion?
The surface tension of water enhances the sticking effect of water molecules.
64
How does transpiration affect water movement in plants?
As water is lost through transpiration, more water can be drawn up the stem.
65
What do sieve tube elements do in phloem vessels?
They form a tube to transport sucrose in the dissolved form of sap.
66
What is the role of companion cells in phloem vessels?
They are involved in ATP production for active loading of sucrose into sieve tubes.
67
What are plasmodesmata in phloem vessels?
They are gaps between cell walls where the cytoplasm links, allowing substances to flow.
68
Translocation
The process whereby organic materials are transported around the plant.
69
How does sucrose enter companion cells of the phloem vessels?
By active loading, which uses ATP and a diffusion gradient of hydrogen ions.
70
How does sucrose move from companion cells into the sieve tube elements?
Sucrose diffuses through the plasmodesmata.
71
What happens to water potential inside the phloem when sucrose moves into the tube elements?
It is reduced.
72
What process causes water to enter the phloem from the xylem?
Osmosis.
73
What effect does the entry of water into the phloem have on hydrostatic pressure?
It increases hydrostatic pressure.
74
In which direction does water move along the sieve tube?
Towards areas of lower hydrostatic pressure.
75
What happens to sucrose after it moves into the phloem?
It diffuses into surrounding cells where it is needed.
76
What happens when a stem is cut in relation to sap?
Sap is released when a stem is cut.
77
What can be inferred about pressure in the phloem based on sap release?
There must be pressure in the phloem.
78
Where is the sucrose concentration higher, in the leaves or the roots?
The sucrose concentration is higher in the leaves than in the roots.
79
What effect does increasing sucrose levels in the leaves have on the phloem?
Increasing sucrose levels in the leaves results in increased sucrose levels in the phloem.
80
What is one piece of counter evidence against the Mass Flow Hypothesis?
The structure of sieve tubes seems to hinder mass flow.
81
Do all solutes move at the same speed according to the Mass Flow Hypothesis?
No, not all solutes move at the same speed.
82
How is sucrose delivered throughout the plant according to the counter evidence?
Sucrose is delivered at the same rate throughout the plant.
83
According to the counter evidence, does sucrose move to areas with the lowest sucrose concentration first?
No, sucrose does not move to areas with the lowest sucrose concentration first.
84
What part of a tree is removed in ringing experiments?
The bark and phloem
85
What is left behind after the bark and phloem are removed in ringing experiments?
The xylem
86
What happens to the tissues above the missing ring in a ringing experiment?
They swell due to accumulation of sucrose
87
What happens to the tissue below the missing ring in a ringing experiment?
It begins to die
88
What substance must be transported in the phloem according to ringing experiments?
Sucrose
89
What is the purpose of using radioactive CO2 in tracing experiments with plants?
To incorporate radioactive carbon into the plant's sugars.
90
What technique is used to visualize the areas of a plant exposed to radiation?
Autoradiography
91
In tracing experiments, what part of the plant corresponds to the areas exposed to radiation?
The phloem

Biology: 3.3 Exchange of Substances (3 decks)

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