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Biology A-level > Biology Chapter 7 > Flashcards

Biology Chapter 7 Flashcards

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1
Q

Describe the quaternary structure of haemoglobin

A

4 polypeptides linked together: 2 alpha and 2 beta groups. 4 ferrous ions, one bound to each polypeptide, which can each bind to one oxygen molecule

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2
Q

How many oxygen molecules can be carried by one haemoglobin molecule?

A

4

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3
Q

Name 2 properties of haemoglobin which can make it efficient at transporting oxygen

A

Readily associates with oxygen when oxygen is plentiful

Readily releases oxygen where oxygen is needed

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4
Q

How does haemoglobin achieve efficiency at transporting oxygen

A

It changes its affinity for oxygen according to conditions. Its shape changes in high carbon dioxide to release oxygen

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5
Q

How does carbon dioxide concentration affect whether haemoglobin is released or attached?

A

Low carbon dioxide concentration = oxygen is attached

High carbon dioxide concentration = oxygen is released

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6
Q

Suggest why the concentration of oxygen is low in respiring tissues, while the concentration of carbon dioxide is high

A

Because oxygen is being used up to produce energy, and carbon dioxide is a by-product of respiration

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7
Q

Define ‘high affinity’

A

Easily takes up oxygen but gives it away less readily

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8
Q

Define ‘low affinity’

A

Releases oxygen more readily but takes up oxygen less readily

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9
Q

Explain how the environment can influence the type of haemoglobin an organism exhibits

A

When little oxygen is available from the environment, haemoglobin must be able to bind as much of it as possible

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10
Q

Explain how metabolic rate can influence the type of haemoglobin an organism exhibits

A

A high metabolic rate means the organism needs oxygen readily available; therefore, it needs a type of haemoglobin that can release oxygen readily

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11
Q

Why do different haemoglobins have different affinities for oxygen?

A

Slightly different amino acid sequences means that haemoglobins have different shapes and affinities

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12
Q

Define ‘loading/associating’

A

Haemoglobin combining with oxygen

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13
Q

Define ‘unloading/dissociating’

A

Oxygen being released from haemoglobin

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14
Q

Why, at very low concentrations of oxygen, is it difficult for haemoglobin to load the first oxygen molecule?

A

There is a close union between the 4 polypeptides of the haemoglobin molecule

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15
Q

What is meant by ‘partial pressure’?

A

The proportion of the total pressure that is contributed by a particular gas in a mixture

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16
Q

What is measured on the x-axis of an oxygen dissociation curve?

A

Partial pressure of oxygen (KPa)

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17
Q

What is measured on the y-axis?

A

Saturation of haemoglobin with oxygen (%)

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18
Q

Why does the graph show a steep rise in oxygen saturation of haemoglobin at higher concentrations of oxygen?

A

After the first oxygen molecule has bound, it is much easier for the other 3 polypeptides to binds to oxygen

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19
Q

What is the name given to the graph of the relationship between oxygen binding and oxygen concentration?

A

Oxygen dissociation curve

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20
Q

Explain why the graph tails off at high concentrations of oxygen

A

The haemoglobin molecule is saturated

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21
Q

How are the oxygen dissociation curves of different haemoglobins similar?

A

Similar S-shaped curves

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22
Q

How are oxygen dissociation curves different?

A

Different positions on the axes

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23
Q

The further to the left the curve…

A

the greater the affinity for oxygen

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24
Q

The further to the right the curve…

A

the lower the affinity for oxygen

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25
Q

How does the presence of carbon dioxide affect haemoglobin’s affinity for oxygen?

A

Reduces it

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26
Q

What affect does carbon dioxide have on the dissociation curve?

A

Shifts it to the right

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27
Q

What is the Bohr effect?

A

Where haemoglobin releases its oxygen more readily in response to a greater carbon dioxide concentration

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28
Q

Is pH at the gas exchange surface raised or lowered?

A

Raised

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29
Q

How does raised pH affect haemoglobin’s affinity to load oxygen?

A

Increases due to shape change

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30
Q

Why is oxygen not released before it gets to respiring tissues?

A

Shape change also increases affinity

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31
Q

Why is oxygen released at respiring tissues?

A

Increased carbon dioxide concentration leads to increased acidity and shape change in haemoglobin

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32
Q

Why might there be more oxygen unloaded at an active muscle cell than an intestinal epithelial cell during heavy exercise?

A

The more carbon dioxide is produced, the greater the shape change in haemoglobin and so the more oxygen is unloaded

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33
Q

Suggest where the dissociation curve of a native mountain dweller in the Andes where the air is thinner would lie? why?

A

Left

Needs ability to load oxygen at low partial pressures

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34
Q

Name 6 features of a transport system

A
  1. Suitable medium
  2. A form of mass transport
  3. Closed system of tubular vessels
  4. Mechanism for moving the medium in the vessels
  5. Unidirectional flow
  6. Means of controlling flow
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35
Q

What is meant by a ‘double circulatory system’?

A

The blood passes through the heart twice for each circuit of the body

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36
Q

What are the 3 types of blood vessels?

A

Arteries

Veins

Capillaries

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37
Q

The final exchange from blood into cells is rapid because…

A
  1. Large surface area

2.

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38
Q

The final exchange from blood into cells is rapid because…

A
  1. Large surface area
  2. Short diffusion pathway
  3. Steep diffusion gradient
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39
Q

Describe the thickness of muscle in the atria and why?

A

Thinnest layer of muscle

Only has to pump blood a short distance (to ventricles)

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40
Q

Describe the thickness of the right ventricle and why?

A

Thicker than atria, thinner than left ventricle

Pumps blood to the lungs

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41
Q

Describe the thickness of the left ventricle and why?

A

Thickest layer of muscle

Blood must be pumped to the rest of the body at high pressure

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42
Q

What is the advantage of having 2 separate pumps?

A

Blood pressure in the rest of the body can remain higher, while blood that goes to the lungs can go slowly with low blood pressure

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43
Q

What is the function of valves in the circulatory system?

A

To prevent the back flow of blood

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44
Q

Number of flaps in the left atrioventricular valve?

A

2 (bicuspid)

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45
Q

Number of flaps in the right atrioventricular valve?

A

3 (tricuspid)

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46
Q

Which heart chamber pumps blood into the aorta?

A

Left ventricle

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47
Q

Which blood chamber receives blood from veins?

A

Atria

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48
Q

Which 2 organs do pulmonary vessels link?

A

Heart and lungs

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49
Q

The aorta is connected to ____ to carry _____ blood to _____ except _____

A

Left ventricle

Oxygenated

All of the body

Lungs

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50
Q

The vena cava is connected to ____ to carry _____ blood from _____

A

Right atrium

Deoxygenated

All of the body

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51
Q

The pulmonary artery is connected to _____ to carry ______ blood to ______

A

Right ventricle

Deoxygenated

Lungs

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52
Q

The pulmonary vein is connected to _____ to carry _____ blood from _____

A

Left atrium

Oxygenated

lungs

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53
Q

What is the name given to the blood vessels that supply the heart itself with oxygen?

A

Coronary arteries

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54
Q

What is a myocardial infarction?

A

Flow through a coronary artery is reduced/prevented by blockage; oxygen supply to part of heart muscle is reduced; tissue may dies as a result (heart attack)

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55
Q

Suggest why it is important that oxygenated and deoxygenated blood is kept separate in the heart

A

To ensure that only oxygenated blood is delivered to tissues so that they have adequate oxygen for respiration

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56
Q

What are 4 risk factors associated with coronary heart disease?

A
  1. Smoking
  2. High blood pressure
  3. Blood cholesterol
  4. Diet
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57
Q

How does high blood pressure increase the risk of heart disease?

A

The heart must work harder to pump blood into higher-pressured arteries and so the arteries are more likely to suffer from an aneurysm and arteries thicken and harden, restricting blood flow

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58
Q

2 phases of heartbeat:

A

Systole (contraction)

Diastole (relaxation)

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59
Q

2 ways direction of blood flow is maintained:

A

Valves

Pressure changes

60
Q

During diastole the pressure in the atria _____, the pressure in the ventricles _____ and the semi lunar valves ______

A

Increases

Decreases

Close

61
Q

During atrial systole the atrial muscle wall _____, the blood in the atria ________________ and the ventricle muscle wall _______

A

Contracts

Is squeezed into the ventricles

Remains relaxed

62
Q

During ventricular systole the ventricle muscle wall _______, the atrioventricular valves _____, the pressure in the ventricles _______ and the semi lunar valves ______

A

Contracts

Close

Increases

Open

63
Q

Where is the atrioventricular valve located?

A

Between the atrium and ventricle on the same side of the body

64
Q

Where is the semi-lunar valve located?

A

Aorta and left ventricle

Pulmonary artery and right ventricle

65
Q

where are pocket valves located?

A

Veins

66
Q

What is the equation for cardiac output?

A

Heart rate x stroke volume

67
Q

What is the function of the arteries?

A

Carry blood from heart to arterioles

68
Q

What is the function of the arterioles?

A

Control blood flow between arteries and capillaries

69
Q

What is the function of the capillaries?

A

Link arterioles to vein; the smallest blood vessel

70
Q

What is the function of the veins?

A

Carry blood from capillaries back to heart

71
Q

Name the structure that helps maintain blood pressure through the ability to stretch

A

Elastic layer

72
Q

Name the part of the vessel in which the blood travels

A

Lumen

73
Q

Name the structure that resists pressure changes

A

Tough outer layer

74
Q

Name the structure that reduces friction; thin

A

Endothelium

75
Q

Name the structure that controls the flow of blood

A

Muscle layer

76
Q

What is the pressure of blood in the arteries?

A

High

77
Q

What is the function of the thick muscle layer?

A

Control of blood volume

78
Q

What is the function of the thick elastic layer?

A

Maintains blood pressure

79
Q

what is the function of the thick wall

A

Prevents artery bursting

80
Q

Function of no valves

A

High pressure means backflow is not a problem

81
Q

What is the pressure of blood in the arterioles?

A

Lower than in arteries

82
Q

Function of thicker muscle wall of arterioles

A

Allows constriction of the arterioles to control the blood supply into the capillaries

83
Q

Function of the thinner elastic layer of arterioles?

A

Due to lower blood pressure

84
Q

What is the pressure of blood in the veins?

A

Low

85
Q

4 adaptations of veins

A

Thin muscle layer = carry blood away from tissues, so fine control is not required

Thin elastic layer = low pressure

Overall thinness of wall layer = low pressure; allows veins to be flattened more easily

Valves = ensures blood flows only towards the heart

86
Q

Function of capillaries

A

To exchange metabolic materials between the blood and the tissues

87
Q

Pressure and speed of blood in the capillaries:

A

Pressure = very low

Speed = slow

88
Q

5 adaptations of capillaries

A

Wall consists of lining layer = short diffusion distance

Many of them, branched = large surface area for diffusion to take place

Narrow diameter = can reach deep into tissues

Extremely narrow lumen = Red blood cells squeezed flat, decreases diffusion distance

Spaced between endothelial cells = white blood cells can escape to deal with infections

89
Q

How is hydrostatic pressure produced?

A

High pressure is created at the arterial end of the capillaries as there is high pressure from the heart forced through smaller and smaller blood vessels

90
Q

2 ways the outward pressure is resisted:

A
  1. Tissue fluid outside the capillaries generates a counteracting hydrostatic pressure
  2. Blood has a lower water potential
91
Q

What is the overall effect of these different pressures?

A

Tissue fluid if pushed out of the capillaries

92
Q

Summarise the 4 steps involved in the return of tissue fluid to the circulatory system

A
  1. Hydrostatic pressure in the capillaries is reduced as tissue fluid moves out
  2. The hydrostatic pressure is therefore lower at the venous end of the capillaries than that of the surrounding tissue fluid
  3. Tissue fluid is forced to re-enter the capillaries
  4. Osmotic forces also help to draw water back in
93
Q

How is the remainder of tissue fluid transported back into the blood?

A

Through lymph vessels via the lymphatic system

94
Q

2 adaptations of root hairs that increase their efficiency

A
  1. Large surface area

2. Thin surface layer

95
Q

There is a high water potential in the _____

A

Soil

96
Q

There is low water potential in the ____

A

Root

97
Q

As a result, water more from the ____ into the ____ by ____

A

Soil

Root

Osmosis

98
Q

Summarise the movement of water as it moves up the root

A

Water increases the water potential of a root-hair cell. As the next root-hair cell now has a lower water potential in comparison, water moves into it by osmosis, and continues in this way by osmosis

99
Q

What is a likely method of transport into the xylem?

A

Osmosis

100
Q

Movement of water up stems depends on:

A
  1. Humidity

2. The stomata being open

101
Q

Water is lost by:

A

Evaporation

102
Q

Water in then replenished from:

A

The xylem

103
Q

Water moves by the establishment of:

A

A water potential gradient

104
Q

Name a factor responsible for the movement of water up the stem in the xylem:

A

Cohesion-tension

105
Q

Define ‘cohesion’

A

Water molecules’ stick together’ as they form hydrogen bonds between one another

106
Q

What is the ‘transpiration pull’?

A

Water molecules are drawn up the xylem tubes as a result of evaporation from the leaves. This is aided by water’s cohesive properties

107
Q

Name given to this theory of water movement

A

The cohesion-tension theory

108
Q

Give 3 pieces of evidence to support the cohesion-tension theory

A
  1. During the day, there is more negative tension in the xylem so the tree trunk decreases in diameter. it expands again at night when there is less transpiration
  2. A tree can no longer draw up water from a broken xylem vessel
  3. When a xylem vessel is broken, air is drawn back in, rather than water leaking out
109
Q

Is transpiration pull a passive or active process?

A

Passive

110
Q

Where does the energy in this system come from?

A

The sun

111
Q

Why does transpiration occur?

A

Leaves have a large surface area and stomata to facilitate photosynthesis

112
Q

What are the benefits to transpiration?

A

Helps add to the amount of water transported in the plant, and increases the rate of solute transport

113
Q

How does an increase in light intensity result in a corresponding increase in transpiration?

A

Photosynthesis increases with light intensity, so stomata are more likely to open, increasing water loss

114
Q

How does a rise in temperature lead to an increase in transpiration?

A
  1. Increases the speed at which the water molecules are moving, which leads to increased evaporation
  2. Decreases the air’s water potential
115
Q

What is the effect on transpiration of high humidity?

A

Reduces transpiration

116
Q

Is the water potential of air higher in lower or higher humidity?

A

Higher humidity

117
Q

How does a breeze increase the rate of transpiration?

A

It disperses the water vapour that collects near the stomata. This increases the water potential gradient

118
Q

Describe the stages and results of a photometer experiment

A

Cutting is attached to a water-filled tube and a bubble is introduced into the end of the tube which moves up the tube, therefore allowing measurements of water loss by/rate of transpiration

119
Q

Define translocation

A

The movement of organic substances around a plant

120
Q

Where does translation take place?

A

In the phloem vessels

121
Q

Is translocation an active process?

A

Yes, it requires energy to create a pressure difference

122
Q

Explain how sucrose is transferred into sieve elements

A
  1. Sucrose is loaded into the phloem at the source (usually a photosynthesising leaf)
  2. Hydrogen ions are pumped out of the companion cell using ATP
  3. This creates a high concentration of hydrogen ions outside the companion cell
  4. Sucrose is loaded (moved into companion cells) by active transport, against the concentration gradient
123
Q

Explain the mass flow of sucrose through sieve tube elements

A

Sucrose diffuses down the concentration gradient into the sieve tube elements. This lowers the water potential of the sieve tube element so water enters by osmosis

124
Q

Explain how sucrose is unloaded at the phloem

A
  1. Sucrose is unloaded from the phloem into a sink (e.g root)
  2. Sucrose moves out by diffusion and is then converted into another substance to maintain a concentration gradient
  3. Water will follow by osmosis
125
Q

What name is given to the hypothesis for how solutes are transported by the phloem

A

Mass flow hypothesis for translocation

126
Q

At the source sucrose is co-transported with _____ into ______

A

Hydrogen ions

Companion cells (linked to sieve cells)

127
Q

What does sucrose decrease in the phloem?

A

Water potential

128
Q

What does this create?

A

Hydrostatic pressure that pushes fluid along the phloem

129
Q

Why is sucrose required by cells?

A

For respiration or converted into starch for storage

130
Q

What is the name given to cells that require glucose?

A

Sink

131
Q

How is sucrose transported out of the phloem?

A

Companion cells actively transport sucrose out of the phloem

132
Q

What does this do to the water potential in the surrounding cells?

A

Causes them to have a more negative water potential than the phloem, so water leaves the phloem and enters the cells, causing fluid to be pulled towards the sink

133
Q

What evidence supposes the mass flow hypothesis?

A
  1. If the phloem is cut, hydrostatic pressure causes sap to seep from the cut
  2. Sucrose concentration is higher in the source than in the sink areas
  3. Low light slows translocation due to reduced sucrose production from photosynthesis
  4. Low oxygen slows translocation due to reduced ATP production from photosynthesis
134
Q

What evidence questions the mass flow hypothesis?

A
  1. Role of the sieve plates is unknown, they may hinder movement of solutes
  2. Different types of solutes move at different speeds; they should all move at the same speed in mass flow
135
Q

Name 2 ways evidence has been gained about the mechanism of translocation in plants:

A
  1. Ringing experiments

2. Tracer experiments

136
Q

How does a ringing experiment illustrate that sugars are transported in the phloem?

A

Removing phloem so sugary liquid builds up above the cut and non-photosynthetic tissue below the cut die due to no sugar

137
Q

How do tracer experiments show that translocation of organic molecules occurs in the phloem?

A

Plant kept in 14C carbon dioxide atmosphere

Sugars incorporate 14C

X-ray film responds to 14C and darkens only over locations of phloem

138
Q

Suggest why a student cut the shoot and put it into the photometer under water in a photometer experiment

A

To prevent air bubbles

139
Q

Suggest why a student would make repeat measurements in a photometer experiment

A

To get a reliable mean

To get concordant results

140
Q

Suggest how a sieve tube cell is adapted for translocation

A
  1. End walls form sieve plates

2. No nucleus/ ribosomes so more space for material to pass

141
Q

What are physical and chemical digestion and where do they take place?

A

Physical breakdown = large to small molecules which are possible to ingest and have a large surface area for chemical digestion. Occurs in the mouth by teeth and stomach when churned by muscles in the stomach wall

Chemical breakdown = hydrolyse large insoluble molecules into smaller, soluble ones

142
Q

Describe how starch is digested by amylases and membrane-bound disaccharidases

A

Amylase breaks down starch (polysaccharide) into maltose (disaccharide) in the mouth with enzymes made in the salivary glands. The glycosidic bonds are hydrolysed. Attached to the cell membrane in the ileum are membrane bound disaccharidases such as sucrose

143
Q

Describe digestion of lipids by lipase

A

Lipases breaks down lipids into fatty acids and monoglycerides. Bile salts (made in the liver, stored in the gall bladder) emulsify lipids and so increase the surface area for lipases to work on. Then, the monoglycerides and fatty acids stick to the bile salts and form micelles. Micelles help the products of lipid digestion to be absorbed

144
Q

Describe digestion of proteins by endopeptidases, exopeptidases and membrane-bound dipeptidases in mammals

A

Endopeptidases hydrolyse peptide bond within a protein. Exopeptidases hydrolyse peptide bonds at the end of proteins by removing single amino acids. Dipeptidases are exopeptidases that work specifically on dipeptides often found in the cell-surface membrane of epithelial cells in the small intestine

145
Q

Describe the structure of the ileum and explain how it is adapted for the function of absorption

A
  1. Villi and microvilli increase surface area for diffusion
  2. Thin walled = short diffusion pathway
  3. Rich blood supply = maintains concentration gradient
  4. Contain muscle which can move =maintains concentration gradient
146
Q

Explain how triglycerides are absorbed

A

Micelles help to move monoglycerides and fatty acids to the epithelium. Micelles are constantly breaking up and re-forming releasing monoglycerides and fatty acids to be absorbed. They are lipid soluble so can diffuse across the epithelial cell membrane

Biology A-level (14 decks)

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