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Biology > 3B Mass Transport > Flashcards

3B Mass Transport Flashcards

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1
Q

What kind of protein is haemoglobin?

A
  • globular
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2
Q

What is haemoglobin?

A
  • an oxygen-carrying pigment found in vast quantities in red blood cells
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3
Q

Describe the structure of red blood cells

A
  • biconcave discs for high SA:V ratio
  • no nucleus
  • more space for haemoglobin for more oxygen transport
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4
Q

Describe the quaternary structure of haemoglobin

A
  • made up of 4 polypeptide chains (globin proteins)
  • made of 2 alpha globins and 2 beta globins
  • each globin has a prosthetic haem group
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5
Q

How are the 4 globin subunits held together and arranged in haemoglobin?

A
  • held together by disulphide bonds
  • arranged with hydrophobic R groups facing inwards which preserves the 3D spherical shape
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6
Q

Why does the hydrophilic R groups facing outwards in haemoglobin benefit the molecule?

A
  • it maintains solubility
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7
Q

Why is the arrangement of the R groups within haemoglobin important for its function?

A
  • if changes occur to amino acid sequence, the function of the protein can change
  • eg. in sickle cell anaemia, valine (non-polar) replaces glutamic acid (polar) which affects solubility of haemoglobin (lessens it)
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8
Q

Describe the importance of the prosthetic haem groups in haemoglobin

A
  • prosthetic haem group contains an iron (II) ion (Fe2+) which is able to reversibly combine with an oxygen molecule
  • this forms oxyhaemoglobin
  • the presence if this causes blood to appear bright red in colour
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9
Q

How many oxygen molecules can each haemoglobin molecule carry?

A
  • 4
  • each haem group can carry one molecule
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10
Q

Are all haemoglobin molecules the same?

A
  • the haem group is the same for all types of haemoglobin
  • the globin chains can differ lots from different species of haemoglobins
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11
Q

Describe the function of haemoglobin

A
  • responsible for binding oxygen in the lung and transporting oxygen to the tissue to be used in aerobic metabolic pathways (respiration)
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12
Q

How does haemoglobin help with transport of oxygen?

A
  • oxygen isn’t very soluble in water
  • haemoglobin is soluble in water
  • oxygen can be carried more efficiently around the body when bound to haemoglobin
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13
Q

What does the presence of the haem group enable?

A
  • enables small molecules like oxygen to be bound more easily because as each oxygen binds the quaternary structure is altered
  • this is due to changes in the teriary structure
  • this causes haemoglobin to have a higher affinity for subsequent oxygen molecules
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14
Q

Describe cooperative binding of haemoglobin

A
  • binding of first oxygen molecule results in a conformational change in the structure of the haemoglobin molecule
  • this makes it easier for each successive oxygen molecule to bind
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15
Q

What does the existence of the iron (II) ion in the prosthetic haem group allow?

A
  • allows oxygen to reversibly bind to form oxyhaemoglobin
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16
Q

Which oxygen is hardest to dissociate from the haemoglobin?

A
  • the last one
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17
Q

Describe what partial pressure is

A
  • the pressure of the gas if the gas were in the same volume and temperature by itself
  • it can change with altitude
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18
Q

Does altitude affect % composition of a mixture of gases?

A

no

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19
Q

What does the oxygen dissociation curve describe?

A
  • the relationship between the partial pressure of oxygen and the % saturation of haemoglobin with oxygen
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20
Q

Why can haemoglobin pick up lots of oxygen in the lungs?

A
  • low CO2 in lungs so haemoglobin can pick up more oxygen
  • also a high partial pressure of oxygen in the lungs
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21
Q

Why is oxygen dropped off by haemoglobin in respiring tissues?

A
  • the partial pressure of oxygen is low
  • the oxygen diffuses out into the body cells down a conc grad
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22
Q

Why can a small change in partial pressure of oxygen have a very large effect on the % saturation of haemoglobin with oxygen?

A
  • because haemoglobin has such a high affinity for oxygen
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23
Q

How does the partial pressure of oxygen in different areas of the body help with transport of oxygen?

A
  • it ensures oxygen is picked up from where there is lots of it and dropped off to where there is less of it
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24
Q

How does pH alter haemoglobin?

A
  • CO2 makes blood more acidic
  • pH alters the hydrogen bonds in haemoglobin
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25
Q

What does the Bohr shift explain and how?

A
  • explains how the ability of haemoglobin to bind to and release oxygen changes
  • when partial pressure of CO2 is high (eg. in respiring tissues) haemoglobin’s affinity for oxygen is reduced
  • this is because CO2 lowers the pH of the blood by forming carbonic acid and causes the release of oxygen
  • CO2 in the lungs is comparatively lower so haemoglobin’s affinity for oxygen is increased
  • causes easier binding
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26
Q

How does more CO2 affect the position of the oxygen dissociation curve?

A
  • more CO2 shifts the dissociation curve to the right
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27
Q

What can have a major impact on the evolution of haemoglobin within a species?

A
  • environmental factors
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28
Q

Describe the effects of altitude on haemoglobin

A
  • the pp of oxygen is lower at higher altitudes
  • species living at high altitudes have haemoglobin that is adapted to these conditions
  • eg. llamas have haemoglobin that binds much more readily with oxygen
  • this is beneficial as it allows them to obtain a sufficient level of oxygen saturation in their blood when the pp of oxygen is low
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29
Q

Describe the deer mouse’s haemoglobin

A
  • they populate much of the US at high and low altitudes
  • this species inhabits the widest range of altitudes of any north american mammal and it has a large degree of genetic variation for haemoglobin
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30
Q

Describe the lugworm and how its oxygen dissociation curve compares to that of a deer mouse

A
  • lugworms live in low oxygen conditions
  • luworm/high altitude deer mouse curve is to the right of the low altitude deer mouse’s curve and reaches 100% saturation quicker
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31
Q

Describe the adaptations of foetal haemoglobin

A
  • more efficient at absorbing oxygen at lower concs
  • vital as it allows for a baby to obtain oxygen from its mother’s blood (via placenta)
  • oxygen conc in mother’s blood is lower than oxygen conc in the lungs
  • after birth, the baby produces adult haemoglobin as it is more suited for uptake of oxygen from the air
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32
Q

Describe myoglobin and its adaptations

A
  • ‘muscle haemoglobin’
  • higher affinity for oxygen than foetal and adult haemoglobin
  • myoglobin can take oxygen from adult haemoglobin
  • used for storing oxygen in muscles
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33
Q

Compare the oxygen dissociation curves of myoglobin, foetal haemoglobin and adult haemoglobin

A
  • myoglobin is furthest left
  • foetal haemoglobin is in the middle
  • adult haemoglobin is furthest right
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34
Q

What tends to be the case in larger more complex organisms in terms of their important exchange sites?

A
  • they tend to be far away from other cells within the organism
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35
Q

Why is diffusion a non-viable method for transport of substances in larger organisms?

A
  • the distance is too far and the process would be inefficient
  • diffusion wouldn’t be fast enough for metabolic requirements of cells
  • diffusion is only involved at exchange sites right at the start and end of the process
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36
Q

What is mass transport?

A
  • the bulk movement of gases or liquids in one direction
  • usually via a system of vessels and tubes
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37
Q

Describe generally the mammal circulatory system as a mass transport system

A
  • one-way flow of blood carries nutrients and gases to all the cells of the body
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38
Q

What do mass transport systems help to do?

A
  • help to bring substances quickly from one exchange site to another
  • they also help maintain diffusion gradients at exchange sites and between cells and their fluid surroundings
  • they ensure effective cell activity by keeping the immediate fluid environment of cells within a suitable metabolic range
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39
Q

Describe blood circulation within mammals (big and small)

A
  • small animals with large SA:V can rely on diffusion to exchange oxygen, CO2 and nutrients
  • larger animals have a smaller SA:V so diffusion alone is insufficient for exchange of materials
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40
Q

What do all organisms need to do?

A

Exchange materials with their environments

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41
Q

What are circulatory systems generally?

A
  • systems which carry around fluids containing materials needed by the organism as well as waste that needs removing
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42
Q

Describe a closed circulatory system

A
  • blood is pumped around the body and is always contained within a network of blood vessels
  • possessed by all vertebrates and many invertebrates
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43
Q

Describe an open circulatory system

A
  • blood isn’t contained within blood vessels but is pumped directly into body cavities
  • possessed by arthropods and molluscs
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44
Q

Which type of circulatory system do humans possess?

A
  • double closed circulatory system
45
Q

Describe the pulmonary circulatory system

A
  • right side of the heart
  • pumps deoxygenated blood to lungs for gas exchange
46
Q

Describe the systematic circulatory system

A
  • left side of the heart
  • pumps oxygenated blood efficiently around the body
  • pumps at high pressure
47
Q

State the pathway of circulation starting at the right atrium

A

right atrium
tricuspid valve
right ventricle
pulmonary artery
lungs
pulmonary vein
left atrium
bicuspid valve
left ventricle
aorta
body
(renal artery, kidneys, renal vein)
vena cava
right atrium
etc.

48
Q

Describe the function of the heart

A
  • hollow muscular organ located in the chest cavity which pumps blood
  • cardiac muscle tissue is specialised for repeated involuntary contraction without rest
49
Q

Describe the function of the arteries

A
  • blood vessels that carry blood away from the heart
  • walls contain lots of muscle and elastic tissue
  • lumen is narrow to maintain high blood pressure
  • arteries range from 0.4-2.5cm in diameter
50
Q

Describe the function of arterioles

A
  • small arteries which branch from larger arteries and connect to capillaries
  • around 30um in diameter
51
Q

Describe the function of the capillaries

A
  • tiny blood vessels which connect arterioles and venules
  • their size means they pass directly past cells and tissues and perform gas exchange and exchange of substances
52
Q

Describe the function of the venules

A
  • small veins which join capillaries to larger veins
53
Q

Describe the function of the veins

A
  • blood vessels which carry blood back towards the heart
  • the walls of veins are thin in comparison to arteries having less muscle and elastic tissue but a wider lumen
  • valves help maintain blood flow back towards the heart
54
Q

Describe the pulmonary artery

A
  • carries deoxygenated blood away from the heart towards the lungs
55
Q

Describe the pulmonary vein

A
  • carries oxygenated blood towards the heart away from the lungs
56
Q

Describe the coronary arteries

A
  • supply the heart with oxygenated blood
57
Q

Describe the aorta

A
  • carries oxygenated blood out of the heart and to the rest of the body
58
Q

Describe the vena cava

A
  • carries deoxygenated blood towards the heart
59
Q

Describe the renal artery

A
  • supplies the kidneys with oxygenated blood
60
Q

Describe the renal vein

A
  • carries deoxygenated blood away from the kidneys to the heart
61
Q

What separates the left and right side of the heart?

A
  • the septum
62
Q

Describe valves in the cardiac cycle

A
  • prevent backflow of blood
  • open when pressure behind them is greater than the pressure in front
  • closed when pressure is greater in front of them
63
Q

Compare semilunar valves and atrioventricular valves

A
  • semilunar separate ventricles and arteries
  • atrioventricular separate atrium and ventricles
64
Q

What is important that happens in regards to the coronary arteries?

A
  • important that they stay free of plaques
  • plaques can lead to angina or heart attacks
65
Q

Describe the heart walls

A
  • ventricular walls are thicker than the atria walls
  • atria wall contractions don’t generate much pressure (only enough to force the blood into the ventricles)
66
Q

Compare the walls of the left and right ventricles

A
  • left wall is thicker than the right
  • blood leaving the left ventricle needs to travel further so needs to be at a higher pressure
67
Q

Describe systole

A
  • contraction of the heart
  • contraction pushes blood out of heart
  • atrioventricular valves are closed
  • semilunar valves are open
68
Q

Describe diastole

A
  • relaxation of the heart
  • atrioventricular valves are open
  • semilunar valves are closed
69
Q

Describe the demands needed for the arteries

A
  • must be able to withstand high pressures generated by the heart
  • must be able to maintain these pressures when the heart is relaxed
70
Q

Describe the structure of the arteries

A
  • wall is thick with layers of collagen, smooth muscle and elastic fibres
  • elastic fibres allow the artery wall to expand around blood surging through at high pressure
  • elastic fibres recoil when the heart relaxes (works with small lumen to maintain high pressure)
71
Q

Describe the function of the veins

A
  • receive blood that has passed through capillary networks
  • blood is at low pressure and must be returned to the heart
72
Q

Describe the structure of the veins

A
  • wall is relatively thin with thinner layers of collagen, elastic fibres and smooth muscle
  • lumen is much bigger than artery’s
  • contain valves that prevent backflow of blood which helps return blood to the heart
73
Q

Describe the arterioles

A
  • what the large arteries split into that then branch into capillaries
74
Q

Describe how arteriole structure relates to function

A
  • walls are similar too artery walls but have more smooth muscle and less elastic fibres because they don’t have to withstand as high a pressure
  • they have the ability to contract due to smooth muscle which regulates the flow of blood to a tissue
  • can contract and temporarily cut off blood flow to certain organs
  • eg. during exercise, blood flow to intestines may be reduced
75
Q

Describe the structure of the capillaries

A
  • very small lumen which forces slower travel so diffusion can occur
  • capillaries branch between cells for a shirt diffusion distance
  • wall is made from a single layer of endothelial cells which gives short diffusion distance and allows small pores to form so blood plasma can leak out and form tissue fluid
76
Q

Describe the general process of how tissue fluid forms

A
  • when blood is at the arteriole end of a capillary, the hydrostatic pressure is great enough to push molecules out of the capillary
  • proteins remain in blood as they are too large to fit through gaps
  • increased protein content lowers water potential
  • the overall movement of water is out of the capillary
  • at the venule end, less fluid is pushed out as the hydrostatic pressure is less than osmotic pressure
  • overall movement of water is into capillary
77
Q

What can hypertension cause in terms of tissue fluid?

A
  • oedema
  • if blood pressure is high then the pressure at the arteriole end is even greater so more fluid is forced out
  • this fluid accumulates around tissues
  • this is called oedema
78
Q

What is tissue fluid and where is it located?

A
  • it is blood plasma without the plasma proteins
  • it is located between/around cells
79
Q

Describe the movement of lymph

A
  • some tissue fluid reenters the capillaries while some enters the lymph capillaries
  • larger molecules enter the lymphatic system as lymph (made by cells, not plasma proteins)
  • the liquid moves along the larger vessels of this system by compression caused by body movement (backflow prevented by valves)
  • plasma proteins escaped from blood are returned to blood via the lymph capillaries
  • if plasma proteins aren’t removed from tissue fluid then the water pot is lower so water can’t be reabsorbed
80
Q

What is chd?

A
  • any condition that interferes with the coronary arteries which supply blood to the heart muscle
81
Q

State some main risk factors of chd

A
  • genetic factors
  • age and sex (older men at most risk)
  • high blood pressure (can cause thicker artery walls, smaller lumen and enlarged ventricles or atheromas (fatty deposits) can develop)
  • smoking (nicotine and tobacco can damage lungs and heart)
  • high conc of low-density lipoproteins in the blood (cause atheromas)
82
Q

What does the xylem transport?

A
  • dissolved mineral ions
  • water
83
Q

What does the phloem transport?

A
  • dissolved organic compounds
84
Q

Compare the uptake of water and minerals

A
  • water is passive via osmosis
  • minerals can be active or passive via active transport and diffusion respectively
85
Q

What 2 routes are there for transport of water and dissolved solutes within a plant?

A
  • apoplast pathway
  • symplast pathway
86
Q

Describe the apoplast pathway

A
  • most water travels this way when transpiration rates are high
  • series of spaces running through cell walls, dead cells and hollow tubes of the xylem
  • water moves via diffusion
  • faster than symplast pathway
87
Q

When must substances switch from the apoplast to the symplast?

A
  • when they reach the Casparian strip
  • it is a thick waterproof waxy band of suberin within the endodermis cells’ cell wall
88
Q

State the order of a flow diagram for the apoplast

A
  • soil water with dissolved mineral ions
  • root hair cell wall
  • cortex cell wall
  • endodermis cell wall
  • casparian strip
    (switch to symplast)
  • endodermis cell membrane
  • endodermis cytoplasm
  • endodermis cell membrane
  • endodermis cell wall
  • xylem vessel
89
Q

Describe the symplast pathway

A
  • smaller amount of substance travels this way
  • consists of cytoplasm and plasmodesmata of cells
  • water moves by osmosis into the cell, possibly into the vacuole and between cells through the plasmodesmata
  • movement of water is slower than apoplast
90
Q

State the order of the flow diagram for symplast

A
  • soil water and mineral ions
  • root hair cell wall
  • root hair cell membrane
  • root hair cell cytoplasm
  • plasmodesmata
  • cortex cytoplasm
  • plasmodesmata
  • endodermis cytoplasm
  • endodermic cell membrane
  • endodermis cell wall
  • xylem vessel
91
Q

Describe transpiration

A
  • the loss of water vapour from a plant to its environment via diffusion
  • this water is replaced by water taken in at the roots and transported to the plant via the xylem
92
Q

Which 2 properties of water allow it to move up the xylem during transpiration#/#

A
  • cohesion: water molecules sticking to each other via hydrogen bonds
  • adhesion: water molecules sticking to xylem walls
93
Q

State some advantages of transpiration

A
  • cools the plant via evaporative cooling
  • transpiration stream is helpful in the uptake of mineral ions
  • the turgor pressure of the cells provides support to the leaves and the stem of non-woody plants
94
Q

Explain the effect on transpiration when air movement is high

A

more
good airflow removes water vapour from the air surrounding the leaf which maintains a conc grad so water loss is increased

95
Q

Explain the effect on transpiration when humidity is high

A

less
humidity is a measure of moisture in the air so when air is saturated with water vapour, the conc grad is weaker so less water is lost

96
Q

Explain the effect on transpiration when light intesnity is high

A

more
guard cells are responsive to light so when it is high they are turgid and stomata are open so water is lost

97
Q

Explain the effect on transpiration when temp is high

A

more
at higher temps particles have more kinetic energy so transpiration occurs at a faster rate

98
Q

Describe the adaptations of phloem for mass flow

A
  • the intracellular space and walls of the sieve cells are adapted for the mass transport of sugars and amino acids
  • very few organelles, small amount of cytoplasm and a large vacuole in intercellular space
  • phloem sap can flow easily by moving through the open corridor that has low resistance
  • sieve cells have thick cell walls to help withstand the pressure exerted by the mass flow of sugars
99
Q

What does phloem sap consist of?

A
  • sugars (mainly sucrose)
  • water
  • other dissolved substances eg. amino acids, hormones
100
Q

What could the source of assimilates be in a plant?

A
  • green leaves and green stem
  • storage organs eg. tubers and tap roots
  • food stores in seeds which are germinating
101
Q

What could the sink of assimilates be in a plant?

A
  • meristems
  • roots that are growing and/or actively absorbing mineral ions
  • any part of the plant where the assimilates are being stored eg. fruits
102
Q

Why are carbs usually transported as sucrose in plants?

A
  • allows for efficient energy transfer and increased energy storage (disaccharide so contains more energy)
  • it’s less reactive than glucose as it’s a non-reducing sugar
103
Q

Describe the first stage of the mass flow theory: loading of assimilates into the sieve tube elements

A
  • sucrose diffuses down a conc grad by facilitated diffusion into the companion cells
  • modified companion cells (transfer cells) pump H+ ions out of their cytoplasm so that they diffuse back in through a co-transporter with sucrose
  • sucrose then moves into the sieve tube cells via diffusion through the plasmodesmata
104
Q

Describe the second stage of the mass flow theory: mass flow of sucrose through the sieve tube elements

A
  • this mechanism permits some plants to build sucrose conc up to 3x the conc of it in mesophyll
  • high conc of sucrose descreases water potential in the phloem and water enters via osmosis
  • results in high hydrostatic pressure
  • sucrose is used or converted to starch for stoareg at respiring tissues/sinks
  • these cells then have low sucrose conc so it is actively transported there which lowers their water potential
  • water moves into these cells so hydrostatic pressure decreases in sieve tubes and creates mass flow to these low pressure areas
105
Q

Describe the third stage of the mass flow theory: unloading of assimilates

A
  • occurs at the sinks
  • sucrose is actively transported by companion cells out of the sieve tubes and into the sink cells
  • to maintain the conc grad, sucrose us converted into other storage molecules eg. starch
106
Q

State evidence supporting the mass flow theory

A
  • when phloem are punctured, phloem sap oozes out which indicates it is at high pressure
  • phloem sap taken from near a source has high sucrose conc more than at sink which shows water potential would result in osmosis
  • when a plant virus is applied to well-lit leaves, the virus can be seen moving through phloem to the roots which demonstrates bulk flow in one direction
  • when virus is applied in the dark it isn’t transported which suggests photosynthesis needs to occur for translocation to occur
107
Q

State some evidence against the mass flow theory

A
  • amino acids travel slower than sucrose but they should travel at equal speeds as they are both in phloem
  • different substances in the same sieve tube travel in different directions
  • it is suggested some sieve tubes translocate at different times
108
Q

What do tracer and ringing experiments involve?

A
  • the removal of a ring of surface tissues from the stem of the plant while leaving the stem core intact

Biology (17 decks)

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