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Biology Unit 2 ☁️ > 2.3 Adaptations for transport > Flashcards

2.3 Adaptations for transport Flashcards

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1
Q

Briefly describe the vascular system of insects.

A

• Open circulatory system
• Dorsal-tube shaped heart
• Respiratory gases not carried in blood

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2
Q

What is an open circulatory system?

A

• Transport medium pumped by the heart is not contained within vessels, but moves freely
• Transport fluid comes into direct contact with the cells

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3
Q

Briefly describe the vascular system of earthworms.

A

• Vascularisation
• Closed circulatory system
• Respiratory gases carried in blood

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4
Q

What is a closed circulatory system?

A

• Blood pumped by the heart is contained within blood vessels
• Blood does not come into direct contact with the cells

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5
Q

Describe the advantages of a closed circulatory system.

A

• Blood pressure can be maintained
• Blood supply to different organs can vary
• Lower volumes of transport fluid required

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6
Q

What type of circulatory system do fish have?

A

Single circulatory system

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7
Q

What is a single circulatory system?

A

• Circulatory system in which the blood travels through the heart once in one circuit

• Blood flows through the heart and is pumped around the body before returning to the heart

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8
Q

What type of circulatory system do mammals have?

A

Double circulatory system

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9
Q

What is a double circulatory system?

A

• Circulatory system in which the blood flows through the heart twice in two circuits

• Blood is pumped from the heart to the lungs before returning to the heart. It is then pumped around the body, after which it returns to the heart again

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10
Q

What are the benefits of a double circulatory system?

A

• Maintains blood pressure around the whole body

• Uptake of oxygen is more efficient

• Delivery of oxygen and nutrients is more efficient

• Blood pressure can differ in pulmonary and systemic circuits

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11
Q

Describe the double circulatory system in humans.

A

Blood flows through the heart twice in two circuits:

• Pulmonary circuit
• Systemic circuit

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12
Q

Name the four chambers of the mammalian heart.

A

• Left atrium
• Right atrium
• Left ventricle
• Right ventricle

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13
Q

Describe the pathway of blood around the body, naming the structures of the heart.

A

Pulmonary vein → Left atrium → Left ventricle → Aorta → Body → Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lungs

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14
Q

Where are the atrioventricular valves found and what is their function?

A

• Found between the atria and ventricles
• Prevent the backflow of blood from the ventricles into the atria

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15
Q

What are the two types of atrioventricular valves?

A

• Bicuspid (left side)
• Tricuspid (right side)

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16
Q

Where are the semilunar valves found and what is their function?

A

• Found between the ventricles and arteries

• Prevent the backflow of blood from the arteries into the ventricles

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17
Q

Name the five types of blood vessel.

A

• Arteries
• Arterioles
• Capillaries
• Venules
• Veins

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18
Q

Describe the pathway of blood through the blood vessels.

A

heart → arteries → arterioles →
capillaries → venules → veins → heart

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19
Q

What is the function of arteries?

A

Carry blood away from the heart to the tissues, under high pressure.

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20
Q

Relate the structure of arteries to their function.

A

Thick, muscular walls to handle high pressure without tearing. Elastic tissue allows recoil to prevent pressure surges.

Narrow lumen to maintain pressure.

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21
Q

What is the function of veins?

A

Carry blood towards the heart under low pressure.

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22
Q

Relate the structure of veins to their function.

A

Thin walls due to lower pressure. Require valves to ensure blood doesn’t flow backwards. Have less muscular and elastic tissue as they don’t have to control blood flow.

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23
Q

What is the function of capillaries?

A

Form a large network through the tissues of the body and connect the arterioles to the venules.

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24
Q

Relate the structure of capillaries to their function.

A

• Walls only one cell thick ∴ short diffusion pathway
• Very narrow, so can permeate tissues and red blood cells can lie flat against the wall, reducing the diffusion distance
• Numerous and highly branched, providing a large surface area

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25
Q

What is the function of arterioles?

A

Connect the arteries and the capillaries.

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26
Q

What is the function of venules?

A

Connect the capillaries and the veins.

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27
Q

Relate the structure of arterioles and venules to their function.

A

• Branch off arteries and veins in order to feed blood into capillaries

• Smaller than arteries and veins so that the change in pressure is more gradual as blood flows to the capillaries

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28
Q

What is the cardiac cycle?

A

• The sequence of events involved in one complete contraction and relaxation of the heart

• Three stages: atrial systole, ventricular systole and diastole

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29
Q

Describe what happens during ventricular diastole.

A

The heart is relaxed.

Blood enters the atria, increasing the pressure and pushing open the AV valves.

This allows blood to flow into the ventricles.

Pressure in the heart is lower than in the arteries, so SL valves remain closed.

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30
Q

Describe what happens during atrial systole.

A

• The atria contract, pushing any remaining blood into the ventricles

• AV valves pushed fully open

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31
Q

Describe what happens during ventricular systole.

A

The ventricles contract.

The pressure in the ventricles increases, closing the AV valves to prevent backflow and opening the SL valves.

Blood flows into the arteries.

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32
Q

Why is cardiac muscle described as myogenic?

A

It initiates its own contraction without outside stimulation from nervous impulses.

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33
Q

Explain how the heart contracts.

A

• SAN initiates and spreads impulse across the atria, so they contract

• AVN receives, delays, and then conveys the impulse down the bundle of His

• Impulse travels into the Purkyne fibres which branch across the ventricles, so they contract from the bottom up.

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34
Q

What is an electrocardiogram (ECG)?

A

A graph showing the electrical activity in the heart during the cardiac cycle.

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35
Q

Explain the characteristic patterns displayed on a typical ECG.

A

• P wave - depolarisation of atria during atrial systole

• QRS wave - depolarisation of ventricles during ventricular systole

• T wave - repolarisation of ventricles during ventricular diastole

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36
Q

Describe the structure and function of erythrocytes.

A

• Type of blood cell that is anucleated and biconcave

• Contains haemoglobin which enables the transport of oxygen and carbon dioxide to and from the tissues

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37
Q

What is plasma?

A

• Main component of the blood (yellow liquid) that carries red blood cells
• Contains proteins, nutrients, mineral ions, hormones, dissolved gases and waste. Also distributes heat

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38
Q

Describe the role of haemoglobin.

A

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

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39
Q

How does partial pressure of oxygen affect oxygen-haemoglobin binding?

A

Haemoglobin has variable affinity for oxygen depending on the partial pressure of oxygen, p(O₂):

• At high p(O₂), oxygen associates to form oxyhaemoglobin
• At low p(O₂), oxygen dissociates to form deoxyhaemoglobin

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40
Q

Write an equation for the formation of oxyhaemoglobin.

A

Hb + 4O₂ ⇌ Hb•4O₂
(note that full saturation is rare)

41
Q

What do oxyhemoglobin dissociation curves show?

A

Saturation of haemoglobin with oxygen (%), plotted against partial pressure of oxygen (kPa). Curves further to the left show that the haemoglobin has a higher affinity for oxygen.

42
Q

Explain the shape of oxyhemoglobin dissociation curves.

A

Sigmoidal curve (S-shaped):

• When first O, molecule binds, it changes the tertiary structure of haemoglobin so that it is easier for the second and third molecules to bind

• Third molecule changes the tertiary structure of haemoglobin so that it is more difficult for the fourth molecule to bind

43
Q

How does fetal haemoglobin differ from adult haemoglobin?

A

Has a higher affinity for oxygen than adult haemoglobin due to the presence of two different subunits that allow oxygen to bind more readily.

44
Q

Why is the higher affinity of fetal haemoglobin important?

A

Enables the fetus to obtain oxygen from the mother’s blood.

45
Q

Predict the shape of the dissociation curves of animals adapted to low oxygen level habitats.

A

• Haemoglobin has a greater affinity for oxygen
• Haemoglobin is saturated at a lower p(O₂)
• ∴ dissociation curve to the left

46
Q

How is carbon dioxide carried from respiring cells to the lungs?

A

• Transported in aqueous solution in the plasma
• As hydrogen carbonate ions in the plasma
• Carried as carbaminohaemoglobin in the blood

47
Q

What is the chloride shift?

A

• Process by which chloride ions move into the erythrocytes in exchange for hydrogen carbonate ions which diffuse out of the erythrocytes

• One-to-one exchange

48
Q

Why is the chloride shift important?

A

It maintains the electrochemical equilibrium of the cell.

49
Q

What is the function of carbonic anhydrase?

A

Catalyses the reversible reaction between water and carbon dioxide to produce carbonic acid.

50
Q

Write equations to show the formation of hydrogen carbonate ions in the plasma.

A

Carbonic anhydrase enzyme catalyses:
CO₂ + H₂O ⇌ H₂CO₃ (carbonic acid)
Carbonic acid dissociates:
Н₂СО₃ ⇌ НСО₃⁻ (hydrogen carbonate ions) + H⁺

51
Q

State the Bohr effect.

A

The loss of affinity of haemoglobin for oxygen as the partial pressure of carbon dioxide increases.

52
Q

Explain the role of carbonic anhydrase in the Bohr effect.

A

• Carbonic anhydrase is present in red blood cells

• Catalyses the reaction of carbon dioxide and water to form carbonic acid, which dissociates to produce H⁺ ions

• H⁺ ions combine with the haemoglobin to form haemoglobinic acid

• Encourages oxygen to dissociate from haemoglobin

53
Q

What is tissue fluid?

A

• Fluid that surrounds the cells of animals
• Same composition as plasma but does not contain red blood cells or plasma proteins

54
Q

Describe the different pressures involved in the formation of tissue fluid.

A

• Hydrostatic pressure = higher at arterial end of capillary than venous end

• Oncotic pressure = changing water potential of the capillaries as water moves out, induced by proteins in the plasma

55
Q

How is tissue fluid formed?

A

As blood is pumped through increasingly smaller vessels, hydrostatic pressure is greater than oncotic pressure, so fluid moves out of the capillaries. It then exchanges substances with the cells.

56
Q

Why does blood pressure fall along the capillary?

A

• Friction
• Lower volume of blood

57
Q

What happens at the venous end of the capillary?

A

• Oncotic pressure is greater than hydrostatic pressure

• Fluid moves down its water potential gradient back into the capillaries

58
Q

Where does some tissue fluid drain?

A

Some tissue fluid drains into the lymphatic system and eventually returns to the blood.

59
Q

Define vascular bundle.

A

• Vascular system in herbaceous dicotyledonous plants
• Consists of two transport vessels, the xylem and the phloem

60
Q

Describe the structure and function of the vascular system in the roots of dicotyledons.

A

Xylem arranged in an X shape to provide resistance against force. Phloem found as patches between the arms. Surrounded by endodermis, aiding water passage.

61
Q

Describe the structure and function of the vascular system in the stem of dicotyledons.

A

Vascular bundles organised around a central pith. Xylem on the inside of the bundle to provide support and flexibility, phloem on the outside. Cambium is found between the two.

62
Q

Which structure in plants is adapted for the uptake of water and minerals?

A

Root hair cells

63
Q

How is water taken up from the soil?

A

• Root hair cells absorb minerals by active transport, reducing the water potential of the root

• Water potential of root hairs cells is lower than that of the soil

• Water moves into the root by osmosis

64
Q

Outline how plant roots are adapted for the absorption of water and minerals

A

Plant roots are composed of millions of root hair cells which have:

• Long hairs that extend from the cell body, increasing the surface area for absorption

• Many mitochondria which produce energy for the active transport of mineral ions

65
Q

State the three pathways by which water moves through the root.

A

• Apoplast pathway
• Symplast pathway
• Vacuolar pathway

66
Q

Describe the apoplast pathway.

A

Water moves through intercellular spaces between cellulose molecules in the cell wall. It diffuses down its water potential gradient by osmosis.

67
Q

Describe the symplast pathway.

A

Water enters the cytoplasm through the plasma membrane and moves between adjacent cells via plasmodesmata. Water diffuses down its water potential gradient by osmosis.

68
Q

Describe the vacuolar pathway.

A

Water enters the cytoplasm through the plasma membrane and moves between vacuoles of adjacent cells. Water diffuses down its water potential gradient by osmosis.

69
Q

Describe the structure and function of the endodermis.

A

• Innermost layer of the cortex of a dicot root
• Impregnated with suberin which forms the Casparian strip
• Endodermal cells actively transport mineral ions into the xylem

70
Q

What is the function of the Casparian strip?

A

• Blocks the apoplast pathway, forcing water through the symplast route
• Enables control of the movement of water and minerals across the root and into the xylem

71
Q

What molecule makes the Casparian strip waterproof?

A

Suberin

72
Q

Relate the structure of the xylem to its function.

A

• Long, continuous columns made of dead tissue, allowing the transportation of water
• Contain bordered pits, allowing the sideways movement of water between vessels
• Walls impregnated with lignin, providing structural support

73
Q

Define transpiration

A

• The loss of water vapour from the parts of a plant exposed to the air due to evaporation and diffusion

• Consequence of gaseous exchange; occurs when the plant opens the stomata to exchange O₂ and CO₂

74
Q

How does water move up the stem?

A

• Root pressure
• Cohesion tension theory
• Capillarity

75
Q

What is root pressure?

A

The force that drives water into and up the xylem by osmosis due to the active transport of minerals into the xylem by endodermal cells.

76
Q

Explain the cohesion-tension theory.

A

• Water molecules form hydrogen bonds with each other, causing them to ‘stick’ together
• Surface tension of the water also creates this sticking effect
• Therefore as water is lost through transpiration, more is drawn up the stem from the roots

77
Q

Define capillarity.

A

The tendency of water to move up the xylem, against gravity, due to adhesive forces that prevent the water column dropping back.

78
Q

State the factors that affect the rate of transpiration.

A

• Light
• Temperature
• Humidity
• Air movement

79
Q

How does temperature affect the rate of transpiration?

A

A higher temperature increases random motion and rate of evaporation, therefore increasing rate of transpiration.

80
Q

How does light affect the rate of transpiration?

A

A higher light intensity increases the rate of photosynthesis, causing more stomata to open for gas exchange, therefore increasing rate of transpiration.

81
Q

How does humidity affect the rate of transpiration?

A

High humidity means the water content of the air next to the leaf is high. This reduces the concentration gradient, therefore decreasing rate of transpiration.

82
Q

How does air movement affect the rate of transpiration?

A

Large amounts of air movement blow moist air away from the leaves, creating a steep concentration gradient.
Therefore increases rate of transpiration.

83
Q

What is a hydrophyte?

A

A plant that is adapted to live and reproduce in very wet habitats, e.g. water lilies.

84
Q

Give adaptations of hydrophytes that allow them to live in wet conditions.

A

• Thin or absent waxy cuticle
• Stomata often open
• Wide, flat leaves
• Air spaces for buoyancy

85
Q

What is a xerophyte?

A

A plant that is adapted to live and reproduce in dry habitats where water availability is low, e.g. cacti and marram grass.

86
Q

Give adaptations of xerophytes that allow them to live in dry conditions.

A

• Small/rolled leaves
• Densely packed mesophyll
• Thick waxy cuticle
• Stomata often closed
• Hairs to trap moist air

87
Q

What are mesophytes?

A

• Terrestrial plants adapted to live in environments with average conditions and an adequate water supply
• They have features that enable their survival at unfavourable times of the year

88
Q

Relate the structure of the phloem to its function.

A

• Sieve tube elements transport sugars around the plant
• Companion cells designed for active transport of sugars into tubes
• Plasmodesmata allow communication and the exchange of substances between sieve tubes and companion cells

89
Q

What are cytoplasmic strands?

A

Small extensions of the cytoplasm between adjacent sieve tube elements and companion cells.

90
Q

Describe the function of cytoplasmic strands.

A

• Allow communication and the exchange of materials between sieve tube elements and companion cells
• Hold the nucleus in place

91
Q

Define translocation.

A

The movement of organic compounds in the phloem, from sources to sinks.

92
Q

Summarise the mass-flow hypothesis of translocation.

A

• Sugar loaded into sieve tubes via active transport
• Lowers water potential, causing water to move in from the xylem
• Hydrostatic pressure causes sugars to move towards the sink

93
Q

Give evidence for the mass-flow hypothesis.

A

• Sap is released when the stem is cut ∴ must be pressure in phloem

• Sap exuding from the stylet (mouthpart) of an aphid inserted into sieve tubes provides evidence that sugars are carried in the phloem

• There is a higher sucrose concentration in the leaves than the roots

• Autoradiographs produced using carbon dioxide labelled with radioactive carbon provide evidence for translocation in the phloem

94
Q

What is autoradiography?

A

A technique used to record the distribution of radioactive material within a specimen.

95
Q

What is a potometer?

A

An apparatus used to measure water uptake from a cut shoot.

96
Q

What is the largest blood vessel at the heart?

A

The aorta.

97
Q

What is an observable feature that differentiates arteries and veins?

A

Arteries have thicker walls than veins.
Veins have a larger lumen and valves

98
Q

What is an observable difference between the left and right ventricles?

A

The left ventricle has a thicker muscle wall than the right.

99
Q

Which structures can be observed between the atria and ventricles?

A

Valves.

Biology Unit 2 ☁️ (4 decks)

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