2.3- Adaptations for transport Flashcards
1
Q
(a)
Open circulatory system
A
Blood is pumped into a haemocoel where it bathes organs and returns slowly to the heart with little control over direction of flow. Blood is not contained in blood vessels.
2
Q
(a)
Closed circulatory system
A
Blood is pumped into a series of vessels; blood flow is rapid and direction is controlled. Organs are not bathed by blood but by tissue
fluid that leaks from capillaries.
3
Q
(a)
Single circulatory system
A
Blood passes through the heart once in each
circulation.
4
Q
(a)
Double circulatory system
A
Blood passes through the heart twice in each circulation – once in the pulmonary (lung) circulation and then again through the systemic (body) circulation.
5
Q
(a)
Vascular system of earthworm
A
Closed circulatory.
5 pseudohearts.
Respiratory pigment haemoglobin carries respiratory gases in blood.
6
Q
(a)
Vascular system of insects
A
Open circulatory system.
Dorsal tube-shaped heart.
No respiratory pigment in blood as lack of respiratory gases in blood due to tracheal gas exchange system.
7
Q
(a)
Vascular system of fish
A
Closed, single circulatory system. Blood pumped to and oxygenated in the gills continues around body
tissues. This means a lower pressure and slower flow around the body.
8
Q
(a)
Vascular system of mammals
A
Closed, double circulatory system.
High blood pressure to body
delivers oxygen quickly. Lower pressure to lungs prevents hydrostatic pressure forcing tissue fluid into and reducing efficiency of alveoli.
9
Q
(b)
Four chambers of the mammalian heart.
A
- Left atrium
- Right atrium
- Left ventricle
- Right ventricle
10
Q
(b)
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
11
Q
(b)
Atrioventricular valves
A
Bicuspid (left side)
Tricuspid (right side)
12
Q
(b)
Function of bicuspid valve
A
prevents backflow of blood into the left atrium when the ventricles contract.
13
Q
(b)
Function of tricuspid valve
A
pressure of the contraction of the
atrium opens this valve which then closes, preventing backflow to the right atrium when the ventricles contract.
14
Q
(b)
Describe the pathway of blood through the blood vessels.
A
heart → arteries → arterioles → capillaries → venules → veins → heart
15
Q
(b)
Semilunar valves
A
Found between the ventricles and arteries
Prevent the backflow of blood from the arteries into the ventricles
16
Q
(b)
Function of aorta
A
carries oxygenated
blood from the left ventricle
to the body
17
Q
(b)
Function of pulmonary atery
A
takes deoxygenated blood to lungs from right ventricle.
18
Q
(b)
Function of pulmonary veins
A
return oxygenated blood
from lungs to the left atrium.
19
Q
(b)
Function of left ventricle
A
comparatively thicker muscular wall to produce a higher pressure to push
oxygenated blood rapidly around the body
20
Q
(b)
Function of right ventricle
A
Thinner muscular wall compared to
the left ventricle as less pressure is produced on contraction.
21
Q
(b)
Function of right atrium
A
contracts
and pumps deoxygenated
blood into the right ventricle
22
Q
(b)
Function of superior vena cava
A
returns
deoxygenated blood to the heart.
23
Q
(b)
Function of arteries
A
Carry blood away from the heart to the tissues, under high pressure.
24
Q
(b)
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.
25
# (b)
Function of veins
Carry blood towards the heart under low pressure.
26
# (b)
Relate the structure of veins to their function.
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.
27
# (b)
Function of capillaries
Form a large network through the tissues of the body and connect the arterioles to the venules.
28
# (b)
Relate the structure of capillaries to their function
* Walls only one cell thick so 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
29
# (c)
Cardic cycle
The sequence of events involved in one complete contraction and relaxation of the heart.
30
# (c)
Stage one of cardic cycle:
Atrial systole
Atrial contract. Pressure opens atrio-ventricular valves. Blood flows into ventricles
31
# (c)
Stage two of the cardic cycle: Ventricular
systole
Ventricles contract. Atrio-ventricular valves close due to pressure in
ventricles being higher than that in the atria. Semilunar valves in aorta and pulmonary artery open. Blood flows into arteries.
32
# (c)
Stage two of the cardic cycle: Ventricular
Diastole
Ventricle muscle relaxes. Semilunar valves close to prevent backflow of
blood into the ventricles.
33
# (c)
Third stage of cardic cycle: Diastole
Heart muscle relaxes and atria begin to fill from vena cava and pulmonary veins.
34
# (c)
Myogenic in context of the heart
It initiates its own contraction without outside stimulation from nervous impulses.
35
# (c)
Explain how the heart contracts
Sinoatrial node initiates and spreads impulse across the atria, so they contract
Atrio-ventricular 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.
36
# (c)
Electrocardiogram (ECG)
A graph showing the electrical activity in the heart during the cardiac cycle.
37
# (c)
ECG P wave
Depolarisation of the atria
corresponding to atrial systole.
38
# (c)
ECG QRS Wave
Spread of depolarisation through
the ventricles resulting in ventricular
systole.
39
# (c)
ECG T Wave
Repolarisation of the ventricles
resulting in ventricular diastole.
40
# (d)
Erythrocytes
**Function:** Contains haemoglobin which enables the transport of oxygen and carbon dioxide to and from the tissues
**Stucture:** Type of blood cell that is anucleated and biconcave
41
# (d)
Role of haemogloblin
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.
42
# (d)
How does partial pressure of oxygen affect oxygen-haemoglobin binding?
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
43
# (d)
What do oxyhaemoglobin dissociation curves show?
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.
44
# (d)
Sigmoidal curve (S-shaped)
When the first oxygen molecule binds to haemoglobin, it changes the tertiary structure, making it easier for the second and third oxygen molecules to bind. This is known as cooperative binding. However, when the third oxygen molecule binds, the structure changes again, making it harder for the fourth oxygen molecule to attach. This pattern of binding explains the sigmoid shape of the oxygen dissociation curve.
45
# (d)
How does fetal haemoglobin differ from adult haemoglobin?
Has a higher affinity for oxygen than adult haemoglobin due to the presence of two different subunits that allow oxygen to bind more readily.
46
# (d)
Why is the higher affinity of fetal haemoglobin important?
Enables the fetus to obtain oxygen from the mother’s blood.
47
# (d)
Compare the dissociation curves of adult and fetal haemoglobin.
Fetal haemoglobin dissociation curve to the left. At the same partial pressure, % oxygen saturation is greater due to fetal haemoglobin having a higher affinity.
48
# (e)
The shape of the dissociation curves of animals adapted to low oxygen level habitats
* Haemoglobin has a greater affinity for oxygen
* Haemoglobin is saturated at a lower p(O2 )
* ∴ dissociation curve to the left
49
# (f)
How is carbon dioxide carried from respiring cells to the lungs?
Some CO2 is carried in the blood dissolved in plasma, while some is carried in the blood as carbaminohaemoglobin.
50
# (f)
Chloride shift
Process by which chloride ions move into the erythrocytes in exchange for hydrogen carbonate ions which diffuse out of the erythrocytes
51
# (f)
Why is the chloride shift important?
It maintains the electrochemical equilibrium of the cell.
52
# (f)
The Bohr effect
The loss of affinity of haemoglobin for oxygen as the partial pressure of carbon dioxide increases.
53
# (f)
Function of carbonic anhydrase
Catalyses the reversible reaction between water and carbon dioxide to produce carbonic acid.
54
# (f)
The role of carbonic anhydrase in the Bohr effect.
Carbonic anhydrase, found in red blood cells, catalyses the reaction between carbon dioxide and water to form carbonic acid. This acid then dissociates, releasing H⁺ ions. The H⁺ ions bind to haemoglobin, forming haemoglobinic acid, which helps oxygen to dissociate from haemoglobin. This process is key to oxygen delivery in respiring tissues.
55
# (g)
Plasma
**Structure:** Contains proteins, nutrients, mineral ions, hormones, dissolved gases and waste. Also distributes heat
**Function:** Main component of the blood (yellow liquid) that carries red blood cells
56
# (h)
Tissue fluid
Tissue fluid surrounds the cells in animals and has a similar composition to plasma, but it lacks red blood cells and plasma proteins.
57
# (h)
Formation of tissue fluid
As blood is pumped through increasingly smaller vessels, hydrostatic pressure is greater than osmotic pressure, so fluid moves out of the capillaries. It then exchanges substances with the cells.
58
# (h)
Describe the different pressures involved in the formation of tissue fluid.
Hydrostatic pressure = higher at arterial end of capillary than venous end
Osmotic pressure = changing water potential of the capillaries as water moves out, induced by proteins in the plasma
59
# (h)
Process of formation of tissue fluid
1. At the arterial end of the capillary bed, hydrostatic
pressure is higher than osmotic pressure.
2. Water and small soluble molecules are forced through
the capillary walls, forming tissue fluid between the cells.
3. Proteins and cells in the plasma are too large to be
forced out.
4. Due to reduced volume of blood and friction, blood
pressure falls and it moves through the capillary.
5. At the venous end of the capillary bed, osmotic pressure of the blood is higher than the hydrostatic pressure.
6. Most of the water from tissue fluid moves back into
blood capillaries (down its water potential gradient). The
remainder of the tissue fluid is returned to the blood via
lymph vessels.
60
# (h)
The formation of tissue fluid and its importance as a link between blood and cells
This is important as plasma transports nutrients, hormones and excretory products and also distributes heat.
61
# (i)
Vascular bundle
Vascular system in herbaceous dicotyledonous plants
Consists of two transport vessels, the xylem and the phloem
62
# (i)
The structure of the vascular system in the roots of dicotyledons.
In dicotyledon roots, the xylem forms a central star shape with phloem between the arms. Surrounded by endodermis, aiding water passage.
63
# (i)
The function of the vascular system in the roots of dicotyledons.
**Xylem:**
Dead cells that transport water and minerals up the plant. They also give strength and support because their walls are reinforced with waterproof lignin.
**Phloem:**
Phloem sieve tubes transport sucrose and amino acids. The sieve elements have sieve plates with pores, allowing cytoplasmic filaments to connect cells. They have no organelles, so companion cells support them by providing ATP (from mitochondria) and proteins through plasmodesmata.
64
# (i)
Structure of the root
Epidermis
Exodermis
Cortex
(parenchyma)
Phloem
Xylem
Endodermis
65
# (j)
Which structure in plants is adapted for the uptake of water and minerals?
Root hair cells
66
# (j)
How is water taken up from the soil?
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.
67
# (k)
the movement of water through the root
apoplast, symplast and vacuolar pathways
68
# (k)
Apoplast pathway
Water moves through intercellular spaces between cellulose molecules in the cell wall. It diffuses down its water potential gradient by osmosis.
69
# (k)
Symplast pathway
Water enters the cytoplasm through the plasma membrane and moves between adjacent cells via plasmodesmata. Water diffuses down its water potential gradient by osmosis.
70
# (k)
Vacuolar pathway
Water enters the cytoplasm through the plasma membrane and moves between vacuoles of adjacent cells. Water diffuses down its water potential gradient by osmosis.
71
# (l)
the structure and function of the endodermis
The endodermis contains the Casparian strip (made of suberin), which blocks the apoplast pathway, forcing water into the symplast pathway. Minerals enter by active transport, lowering the water potential in the xylem. Water follows by osmosis, creating root pressure that helps push water up the plant.
72
# (m)
Relate the structure of the xylem to its function.
Xylem forms long, continuous tubes of dead cells to transport water efficiently. They have bordered pits for sideways movement of water between vessels. Their walls are strengthened with lignin, which gives support and prevents collapse under pressure.
73
# (m)
Describe the structure and function of the vascular system in the stem of dicotyledons.
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.
74
# (n)
Transpiration
Transpiration is the loss of water as water vapour, by evaporation and
diffusion out of the open stomata, from the leaves of plants. It leads to the transpiration stream.
75
# (n)
Transpiration stream
Water enters the root and moves into the xylem, creating root pressure. As water evaporates from leaves, it pulls on the water molecules below. This is due to cohesion (between water molecules) and adhesion (to xylem walls), creating a continuous transpiration pull. This process is called the cohesion–tension theory.
76
# (o)
Factors increasing transpiration
Lower humidity
Higher temperature
77
# (p)
Hydrophyte
A plant that is adapted to live and reproduce in very wet habitats, e.g. water lilies.
78
# (p)
Adaptations shown by hydrophyte
* Little/no waxy cuticle as no need to conserve water.
* Stomata on upper surface as lower surface submerged.
* Poorly developed xylem as no need to transport water.
* Large air spaces (aerenchyma) provide buoyancy and act as
reservoirs of gas.
79
# (p)
Mesophyte
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.
80
# (p)
Adaptations shown by mesophyte
* Close stomata at night to decrease water loss.
* Shed leaves in unfavourable conditions, e.g. winter.
* Underground organs and dormant seeds survive winter.
81
# (p)
Xerophyte
A plant that is adapted to live and reproduce in dry habitats where water availability is low, e.g. cacti and marram grass.
82
# (p)
Adaptations shown by xerophyte
Thick waxy cuticle: reduces evaporation from the leaf surface.
Sunken stomata: trap moist air, reducing the diffusion gradient and water loss.
Rolled leaves: reduce the surface area exposed to air.
Stiff hairs: trap water vapour, lowering the water potential gradient and reducing water loss.
83
# (q)
Relate the structure of the phloem to its function.
* 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
84
# (r)
cytoplasmic strands
Small extensions of the cytoplasm between adjacent sieve tube elements and companion cells.
85
# (r)
function of cytoplasmic strands.
Allow communication and the exchange of materials between sieve tube elements and companion cells and hold the nucleus in place
86
# (r)
Translocation
The phloem transports the products of photosynthesis from the
source (the leaf) to the sink (area of use or storage).
87
# (r)
Summarise the mass-flow hypothesis of translocation.
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
88
# (r)
Evidence for mass-flow hypothesis
At the source, sucrose is made and lowers water potential, so water enters by osmosis. This pushes sucrose into the phloem (loading), increasing hydrostatic pressure. The pressure causes mass flow toward the sink (e.g. root), where sucrose is stored as starch. Water potential rises, so water moves into the xylem.
89
# (r)
Evidence aganist mass-flow hypothesis
* Sieve plates impede flow.
* Translocation is faster than expected with diffusion.
* This theory does not explain
bidirectional flow or different rates of
flow of sucrose and amino acids.
* Does not explain companion cell
mitochondria, high O2 intake or
stopping of translocation by cyanide.
90
# (r)
Autoradiography
A technique used to record the distribution of radioactive material within a specimen.
91
# (r)
Potometer
An apparatus used to measure water uptake from a cut shoot.
