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Flans AS Biology > Mass Transport > Flashcards

Mass Transport Flashcards

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1
Q

Why do large organisms have a transport system?

A

Multicellular organisms, like mammals and plants, have a small surface area to volume ratio so they need a specialised mass transport system to carry molecules between specialised exchange surfaces and cells

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2
Q

Describe haemoglobin

A
  • Found in erythrocytes
  • Protein with quaternary structure
  • 2 alpha and 2 beta sub units, each contains a polypeptide chain and an Fe2+ haem group
  • High affinity for oxygen
  • Can bind to 4 oxygen molecules to form oxyhaemoglobin (this is a reversible reaction)
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3
Q

What is the oxyhaemoglobin dissociation curve described as?

A

Sigmoidal curve

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4
Q

Describe the sigmoidal curve at low oxygen partial pressure

A

The haemoglobin does not easily bind to the oxygen. This is because the haem groups are in the centre of the haemoglobin which makes it difficult for the oxygen to bind with it. This results in a low saturation level at low oxygen partial pressures i.e. low affinity

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5
Q

Describe the sigmoidal curve as the oxygen partial pressure increases

A

The diffusion gradient into the haemoglobin increases. This means that eventually an oxygen molecule will associate with one of the haem groups. This results in a change in the shape of the haemoglobin molecule and makes it easier for more oxygen molecules to associate with the other haem groups, therefore the gradient of the curve increases as the oxygen partial pressure does. However, it is difficult for all the haemoglobin molecules to become 100% saturated even at high oxygen partial pressures. This is because it is difficult for the last oxygen to diffuse and associate with the 4th haem group

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6
Q

Describe carbon dioxide concentration and how it affect the dissociation of oxyhaemoglobin to form haemoglobin

A

At higher partial pressures of carbon dioxide oxygen unloads more readily.
When cells respire they produce carbon dioxide, which raises pCO2. This increases the rate at which oxyhaemoglobin dissociates to form haemoglobin and oxygen . The dissociation curve therefore shift to the right. This is called the Bohr Effect.

The Bohr Effect therefore results in more oxygen being released when more carbon dixoide is being produced. This means that when exercising the muscles can be supplied with more oxygen for continued aerobic respiration

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7
Q

What must haemoglobin be like at low oxygen environments?

A

Must have a higher affinity for oxygen than human haemoglobin. This is because there isn’t much oxygen available so the haemoglobin has to be very good at loading any oxygen available. The dissociation curve moves to the LEFT of a human’s E.g. lugworm

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8
Q

What must haemoglobin be like at high activity levels?

A

The haemoglobin must have a lower affinity for oxygen than human haemoglobin. This is because they need to be able to unload oxygen easily, so that it’s available to use. The dissociation curve moves to the RIGHT of a human’s E.g. hawk

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9
Q

How does the size of the mammal affect the haemoglobin?

A

Small mammals tend to have higher surface area to volume ratios than larger mammals. This means they lose heat quickly, so have a higher metabolic rate to help them keep warm - therefore they have a high oxygen demand. They have haemoglobin with a lower affinity oxygen than human haemoglobin. This is because they need their haemoglobin to easily unload oxygen, so that its available to use. The dissociation curve is to the RIGHT of a human’s. e.g. rat

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10
Q

Mammals have a closed, double circulatory system, what does this mean?

A

Closed - blood is confined to vessels

Double - blood passes twice through the heart for each complete circuit of the body

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11
Q

Where does the pulmonary artery carry blood from and to?

A

From heart to lungs

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12
Q

Where does the pulmonary vein carry blood from and to?

A

From lungs to heart

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13
Q

Where does the aorta carry blood from and to?

A

From heart to body

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14
Q

Where does the vena cava carry blood from and to?

A

From body to heart

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15
Q

Where does the renal artery carry blood from and to?

A

From body to kidneys

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16
Q

Where does the renal vein carry blood from and to?

A

From kidneys to heart

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17
Q

What is the word ‘hepatic’ associated with?

A

Liver

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18
Q

Which side of the heart pumps deoxygenated blood to the lungs?

A

Right

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19
Q

Which side of the heart pumps oxygenated blood to the whole body?

A

Left

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20
Q

Which ventricle has the thicker muscular wall and why?

A

The left ventricle has a thicker muscular wall because the ventricle must contract very hard to pump blood all around the body

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21
Q

What does the septum do?

A

Separates the two sides of the heart so oxygenated blood and deoxygenated blood does not mix

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22
Q

Describe the structure of arteries and arterioles

A

Arteries carry blood from the heart to the rest of the body. These then divide into arterioles

  • Lumen is narrow to maintain the blood pressure
  • Collagen fibres and fibrous means the thick wall can withstand high pressure.
  • The elastic tissue allows the wall to stretch and then recoil. This maintains the diastolic blood pressure
  • The endothelium is smooth to reduce friction and is also folded so it can unfold when the artery stretches
  • Smooth muscle allows contraction and vasoconstriction, this narrows the lumen of the artery.
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23
Q

Describe the structure of the veins

A

Veins carry blood back to the heart

  • Lumen is large to ease the flow of the blood
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24
Q

What is meant by the term systole?

A

Contraction of the cardiac muscle

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25
What is meant by the term diastole?
Relaxation of the cardiac muscle
26
How long does the cardiac cycle last and what heart rate does this give?
0.8 seconds | 75 beats per min
27
What is the first stage of the cardiac cycle?
- Atria fill with blood - Atria contact decreasing the volume of the atria and increasing the pressure in the chambers - blood is squeezed into ventricle via atrioventricular valve
28
What is the second stage of the cardiac cycle?
- Ventricles contract decreasing their volume and increasing the pressure inside their chambers - The pressure inside the ventricle becomes higher than the pressure inside the atria forcing the atrioventricular valves shut to prevent back flow. - The pressure in the ventricles is also higher than that of the arteries which forces the semi-lunar valves open
29
What is the third stage of the cardiac cycle?
- Ventricles and atria both relax (diastole) - The higher pressure in the arteries than ventricles causes the semi lunar valves to close to prevent the back flow of blood into the ventricles - Atria fill with blood - The cycle starts again
30
When are valves closed?
When the pressure beneath the valve is greater than above it
31
What is the lub-dub sound of the heart caused by?
The closing of the atrioventricular valve and the closing of the semi-lunar valve
32
When looking at a graph on the cardiac cycle what mnemonic should you remember to show if the valves are open or closed?
COCO
33
On an electrocardiogram (ECG) what does the 'P' show?
Excitation of the atria (atrial systole)
34
On an ECG what does the 'Q,R,S' show?
Excitation of the ventricles (ventricular systole)
35
On an ECG what does the 'T' show?
Diastole
36
What is the equation for cardiac output?
Cardiac output = Stroke volume x Heart rate
37
What does the blood contain?
- Cells (Red, white, platelets) | - Plasma
38
What does the plasma contain?
- Oxygen - Carbon dioxide - Salts - Glucose - Fatty acids - Amino acids - Hormones - Plasma proteins
39
Describe the composition of tissue fluid
- Similar composition to plasma | - DOES NOT contain plasma proteins
40
What is the role of tissue fluid in the body?
- Transport oxygen and nutrients from the blood to the cells | - Transport carbon dioxide and waste products from the cells back to the blood
41
Where does the formation of tissue fluid occur?
At a capillary network which surrounds cells
42
Describe the process of the formation of tissue fluid
Occurs at the arterial end of the capillary 1 - The higher hydrostatic pressure due to the contraction of the left ventricle muscle of the heart 2 - This means the fluid in the blood is forced out of tiny gaps in the capillary wall 3 - The plasma proteins are retained in the capillary as they are too big to fit through the gaps in the endothelium of the capillary 4 - Fluid is now known as tissue fluid as it surrounds the cells and allows the movement of substances across the plasma membrane 5 - This type of filtration is known as ultrafiltration
43
Describe the process of the return of tissue fluid to the capillary
Occurs at the venous end of the capillary 1 - The blood has lower hydrostatic pressure 2 - The retention of the plasma proteins means plasma has a lower water potential compared to the tissue fluid 3 - There is a small amount of hydrostatic pressure being exerted by the tissue fluid 4 - These two factors result in the tissue fluis entering the capillary carrying carbon dioxide and other waste products from the cells 5 - Some water re-enters capillary via osmosis
44
What is the function of the lymphatic system?
The remainder of the tissue fluid can be returned to the capillaries via the lymphatic system
45
What is the function of the lymph vessels?
- Form a secondary drainage system returning some tissue fluid to the bloodstream via the subclavian vein in the neck
46
Describe the composition of the lymph fluid
- Similar composition to tissue fluid - More lipids and carbon dioxide - Less oxygen and nutrients
47
Where are lymph nodes situated
- Armpit - Groin - Neck - Gut
48
What is the function of the lymph nodes?
Produce lymphocytes which intercept bacteria and viruses and help prevent the spread of microbial infection in the body
49
What is the lymphatic system involved with?
- Draining excess tissue fluid and returning it to the blood - Immune system - produces lymphocytes - Absorption of lipids from digestive system
50
What are the 4 cardiovascular diseases?
- Aneurysm - Thrombosis - Myocardial infarction - Stroke
51
How do most cardiovascular diseases start?
With the formation of an atheroma
52
Describe the stages to the formation of an atheroma
1 - Part of the lining of the artery wall is damaged 2 - Gradually, over time, cells divide in the artery wall and there is a build up of lipids in the endothelium 3 - Exercise/stress can make the plaque break. Blood enters the crack. Platelets are activated and form blood clots. Part of the clot may break off
53
What is an aneurysm?
- Balloon-like swelling if the artery
54
Describe the formation of an aneurysm
- Starts with the formation of an atheroma - Atheroma plaque damages, weakens and narrows the arteries increasing blood pressure - When blood travels through at high pressure, it may push the inner layers of the artery through the outer elastic layer to form an aneurysm - This may burst causing a haemorrhage
55
What is thrombosis?
Formation of a blood clot
56
Describe the formation of thrombosis
- An atheroma plaque can rupture the endothelium of the artery, damaging the artery wall - Platelets accumulate at the site of damage and form a blood clot - This clot can cause complete blockage of the artery lumen, or block a vessel elsewhere in the body
57
What is a myocardial infarction more commonly known as?
A heart attack
58
Describe how a myocardial infarction arises
- If the atheroma becomes unstable, a piece may break off damaging the artery wall and leading to a blood clot forming - If the blood clot blocks the coronary artery, the heart muscle is starved of blood, receiving no oxygen and glucose - If large areas of the heart muscle are affected this can causes complete heart failure - this is often failure
59
What symptoms are present during a myocardial infarction?
- Pain in the chest/upper body - Shortness of breath - Sweating
60
What is a stroke?
Death of part of the brain tissue due to lack of oxygen and glucose being delivered to the tissue
61
How do strokes occur?
Either: - Blockage caused by blood clot travelling to the arteries in the brain - Artery bursting (haemorrhage)
62
What are the symptoms of a stroke?
FAST - Face distorts normally on one side - Arms - weakness of limbs on one side of the body - Speech difficulty - Time to call the hospital asap
63
What are the risk factors for cardiovascular disease? (13)
- Age - Gender - Smoking - High blood pressure (hypertension) - Obesity - Physical inactivity - High concentration in LDL - Diet high in salt - Diet high in saturated fats - Lack of vitamins - Type 2 diabetes - Stress - Family history
64
What is the function of the xylem tissue?
Transport water and mineral ions UP the plant from root to leaves
65
What is the function of the phloem tissue?
Transport assimilates (e.g. sucrose) UP and DOWN the plant
66
What do xylem vessels contain?
- Dead cells aligned end to end - No end walls - No nucleus and cytoplasm - Walls lignified to prevent tubes collapsing and waterproof the walls of the cells - Bordered pits to allow water to flow into adjacent vessels
67
How does water move up a plant?
Cohesion-tension theory
68
Describe the cohesion-tension theory
1 - Water evaporates from the leaf surface (transpiration) 2 - This creates tension in the xylem 3 - Water molecules are cohesive due to hydrogen bonds between molecules so when some are pulled into the leaf, others follow 4 - Water then enters the stem trough the roots
69
What is transpiration?
The loss of water vapour from the aerial parts of the plant, such as through the stomata of the plant
70
What 3 processes cause the movement of water through a leaf?
1 - Osmosis from the xylem to the mesophyll cells 2 - Evaporation from the surface of the mesophyll cells into the intercellular spaces 3 - Diffusion of water vapour from the intercellular spaces out through the stomata
71
Why is transpiration important?
- Water is required in the leaves for photosynthesis - Water is required to enable cells to grow and elongate - Water keeps cells turgid - The flow of water carries useful mineral ions up the plant - Evaporation of water keeps the plant cool
72
Name the factors affecting transpration
- Number of leaves - Number, size and position of stomata - Waxy cuticle - Light intensity - Temperature - Humidity - Wind/air movement - Water availability
73
What does the phloem tissue consist of?
- Sieve tube elements | - Companion cells
74
Describe the structure of sieve tube elements
- Living cells - Little cytoplasm - Few organelles - No nucleus - Cross-walls at intervals called sieve plates - Sieve plates connect the sieve tube elements and allow the sap to flow easily - Sieve tube elements are lined up end to end to form a tube which allows the plant to transport assimilates, mainly sucrose - Plasmodesmata link the cytoplasm of companion cells and sieve tube elements
75
Describe the structure and function of companion cells
- Have cytoplasm and many mitochondria which produce ATP for active transport - Have many proteins in the plasma membrane - Many ribosomes
76
What is translocation?
- The movement of assimilates (solutes e.g. amino acids and sugars like sucrose) - It is an energy-requring process - Translocation moves assimilates from source to sink
77
What is meant by the term source?
The part of the plant that releases the assimilates e.g. leaf, storage organs
78
What is meant by the term sink?
The part of the plant that receives the assimilates e.g. roots, fruit, shoot, meristem
79
What theory best supports the process of translocation?
Mass flow hypothesis
80
How is sucrose actively loaded into the phloem?
1 - Companion cells use ATP to actively transport hydrogen ions out of their cytoplasm ans into the surrounding tissue 2 - This creates a concentration gradient and the hydrogen ions diffuse back into the companion cells with the sucrose. The diffusion occurs through co-transporter proteins 3 - As the concentration of sucrose builds up in the companion cells they diffuse into the sieve tube elements through numerous plasmodesmata
81
Describe mass flow hypothesis
- Active transport is used to actively load the sucrose into the sieve tube element, reducing the water potential - Osmosis moves water into sieve tube element so hydrostatic pressure increases in the sieve tube element - Water moves down the sieve tube from higher hydrostatic pressure at source to lower hydrostatic pressure at sink - Sucrose is removed from the sieve tube by the surrounding cells and water potential increases in the sieve tube element - Water moves out of the sieve tube and reduces the hydrostatic pressure
82
How does the use of asphids support the mass flow theory?
- Asphids feed from the phloem containing sugars - The sap flows out quicker nearer the leaves than further down the stem - This is evidence that there is a pressure gradient
83
How does ringing a tree support mass flow theory?
- Involves removing a ring of bark - A bugle forms at the ringed area because the sugars can't pass the ringed area - This is evidence that there can be a downward flow of sugars
84
How can the use of radioactive tracers support the mass flow theory?
- Tracers such as radioactive carbon (C14) can be used to track the movement of organic substances in a plant - Carbon dioxide containing C14 is used - It is pumped into a container which completely surrounds the leaf - The radioactive carbon will then be incorporated into organic substances produced by the leaf e.g. sugars produced by photosynthesis which will be moved around the plant by translocation
85
How can the use of metabolic inhibitors support the mass flow theory?
- Translocation can be stopped by using a metabolic poison that inhibits the formation of ATP - This is evidence that active transport is involved
86
What evidence is there against mass flow hypothesis?
- Sugar travels to many different sinks not just one with the highest water potential, as the model suggests - The sieve plates would create a barrier to mass flow theory. A lot of pressure would be needed for the solutes to get through at a reasonable rate

Flans AS Biology (6 decks)

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