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Biology A- Level > Component 3 (Adaptations for Transport ) > Flashcards

Component 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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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
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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27
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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28
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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29
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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30
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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31
Q

Why is cardiac muscle described as
myogenic?

A

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

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32
Q

Explain how the heart contracts.

A

● sinoatrial node initiates and spreads impulse across the atria, so
they contract
● atrioventricular node 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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33
Q

What is an electrocardiogram (ECG)?

A

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

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34
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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35
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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36
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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37
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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38
Q

How does the 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

39
Q

Write an equation for the formation of
oxyhaemoglobin.

A

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

40
Q

What do oxyhaemoglobin 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.

41
Q

Explain the shape of oxyhaemoglobin
dissociation curves.

A

Sigmoidal curve (S-shaped):
● When first O2
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

42
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.

43
Q

Why is the higher affinity of fetal
haemoglobin important?

A

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

44
Q

Compare the dissociation curves of adult
and fetal haemoglobin.

A

Fetal haemoglobin
dissociation curve to the left.
At the same partial pressure,
% oxygen saturation is
greater.

45
Q

Fetal haemoglobin
dissociation curve to the left.
At the same partial pressure,
% oxygen saturation is
greater.

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:
H2CO3 ⇌HCO3- (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

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

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

What is the transpiration stream?

A

The flow of water from the roots to the
leaves in plants, where it is lost by
evaporation to the environment.

75
Q

How does water move up the stem?

A

● Root pressure
● Cohesion tension theory
● Capillarity

76
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.

77
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

78
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.

79
Q

State the factors that affect the rate of
transpiration.

A

● Light
● Temperature
● Humidity
● Air movement

80
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.

81
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.

82
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.

83
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.

84
Q

What is a hydrophyte?

A

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

85
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

86
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.

87
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

88
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

89
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

90
Q

What are cytoplasmic strands?

A

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

91
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

92
Q

Define translocation.

A

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

93
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

94
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

95
Q

What is autoradiography?

A

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

96
Q

What is a potometer?

A

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

97
Q

What is a potometer?

A

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

Biology A- Level (11 decks)

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