3.3- Mass Transport Flashcards
1
Q
3 features of an efficient transport system
A
suitable transport medium, closed system of tubular vessels, mechanisms for movement of transport vessels
2
Q
Suitable transport medium
A
Normally liquid but can also be gas e.g blood
3
Q
Closed system of tubular vessels
A
contains medium and branch to all parts of an organism e.g. blood vessels
4
Q
mechanisms for movement of transport medium
A
maintenance of concentration gradient
requires a pressure difference in one part of the system to another
5
Q
How do animals move the transport medium?
A
muscular contractions, skeletal muscles or specialised pump
6
Q
How do plants move the transport medium?
A
natural passive processes such as evaporation
7
Q
What must both animals and plants have a method for?
A
to control flow direction and amount of flow
8
Q
Fish circulatory system
A
2 chambers heart
single loop
blood flows from heart to gills to tissues to heart
9
Q
Human circulatory system
A
heart, lungs, heart, body, heart
10
Q
What is a double circulation system?
A
blood passes through the heart twice per circuit
11
Q
Why do humans have a double circulatory system?
A
the blood can be pumped at higher pressure. Goes slow when going through the lungs meaning it wouldnt reach the extremities
12
Q
Circulatory system in mammals
A
high level activity and maintains temperature via respiration
2 circuits
pulmonary and systemic
13
Q
Pulmonary circulation
A
flow of blood from the heart to the lungs and back to the heart
14
Q
Systemic circulation
A
circulation that supplies blood to all the body except to the lungs
15
Q
how many times does the heart beat a day?
A
100,000
16
Q
myogenic
A
Describes muscle tissue (heart muscle) that generates its own contractions.
17
Q
coronary arteries
A
blood vessels that branch from the aorta and carry oxygen-rich blood to the heart muscle
18
Q
vena cava
A
a large vein carrying deoxygenated blood into the heart
19
Q
pulmonary artery
A
Carries deoxygentated blood from the heart to the lungs
20
Q
pulmonary vein
A
carries oxygenated blood from the lungs to the heart
21
Q
aorta
A
The largest artery in the body. Carries oxygenated blood from the left ventricle to the rest of the body.
22
Q
atrium
A
thin walls, collect blood from body or lungs
23
Q
ventricles
A
thicker walls, capable of strong ejections from the heart
24
Q
Cardiac Output equation
A
heart rate x stroke volume
25
Valves
prevent back flow of blood
Flexible, tough and fibrous
26
atrioventricular valves
between atria and ventricles
Prevent back flow of blood from contracting ventricles and force blood to leave the heart via aorta or pulmonary valve
27
Semi-lunar valve
Found in aorta and pulmonary valve to prevent ventricular backflle
28
Pocket valves
Found in veins - ensure that when veins are squeezed blood flows back towards the heart.
29
Open valves
Pressure is greatest on convex side of cusps
Valve opens
30
Closed valves
Pressure greater on concave side
Blood collects in cusps and forms a tight seal
31
Diastole
Relaxation of the heart
32
Systole
Contraction of the heart
33
Diastole phase
Blood enters the atria from vena cava and pulmonary vein. Increased atrial pressure opens atrioventricular valves so blood flows into ventricles and both chamber walls are relaxed. This reduces pressure in ventricles so it's lower than in aorta or pulmonary artery. SL valves close
34
Atrial systole
Walls of atria contract at the same time so blood is pushed into ventricles and ventricle walls relax to receive blood
35
Ventricular Systole
Ventricles fill and bp increases in ventricles so AV valves close to prevent back flow
Pressure rises which opens semilunar valves. Blood leaves through aorta and pulmonary artery
36
Aortic Pressure in the Cardiac cycle
-Pressure rises when blood leaves ventricles
-It never falls below 12kpa because of the elasticity of the walls
- Elasticity of walls causes recoil action which leads to a rise in pressure before the relaxation phase
37
Atrial Pressure in the Cardiac cycle
-Pressure always low due to thin walls and it peaks when atria contract
-Pressure drops when AV valve closes and walls relax
-Gradual increase in pressure caused by atria filling
-Pressure drops when AV valves open and blood moves into the ventricles
38
Ventricular pressure in the Cardiac cycle
-Starts low but slowly increases as blood enters from atria
-AV valves close
-Pressure higher than in aorta so blood forced through semi-lunar valves
-Large pressure increase when ventricle walls contract
-Pressure falls when ventricle relax
39
Ventricular volume in the Cardiac cycle
-Rises when atria contract and fill ventricles
-Drops when blood is forced out through the semi-lunar valves
-Volume increases again as ventricles fill with blood
40
Arteries
carry blood away from the heart
41
Arterioles
small vessels that receive blood from the arteries and control blood flow to capillaries
42
Capillaries
Microscopic vessel through which exchanges take place between the blood and cells of the body
43
Veins
Blood vessels that carry blood back to the heart
44
Features of arteries, arterioles and veins
Tough fibrous outer layer, muscle layer, elastic layer, thin inner lining, lumen
45
Tough fibrous outer layer
Resists pressure changes from both within and outside arteries, arterioles and veins.
46
Muscle layer
Contracts to help blood flow be controlled
47
Elastic layer
Maintains blood pressure by stretching and recoiling
48
Thin endothelial lining
reduces friction for blood flow and provides a short diffusion surface
49
Lumen
a cavity or passage for blood
50
Why is the artery elastic layer much thicker than veins?
Elastic keeps bp high and arteries need a higher blood pressure to allow blood to travel throughout the body
51
Why do the arteries have no valves but veins do?
Blood is constantly under high pressure in arteries but under much lower pressure in veins so back flow is more likely
52
Why do veins have a thinner muscle layer?
they have lower pressure so don't require lots of muscle to push blood through at high pressure
53
Why is the muscle layer in arterioles thicker than the layer in arteries?
Can construct and control the flow of blood into capillaries
54
Capillary function
allows for diffusion of nutrients and wastes between cells and blood
55
Capillaries- Walls consist of mainly lining layer
Makes the walls thinner. Short diffusion pathway= rapid diffusion
56
Capillaries- numerous and highly branched
Provide a large sa for exchange
57
Capillaries- narrow diameter
Can permeate tissues and get closer to cells
58
Capillaries- Narrow lumen
RBC are squeezed flat against walls to decrease distance
59
Capillaries- spaces between endothelial cells
Allow white bc to escape and get out
60
Tissue fluid
The fluid surrounding the cells and tissues. Allows exchange. Made of blood plasma
61
How else is tissue fluid known?
Interstitial fluid
62
Formation of tissue fluid
1) *high hydrostatic pressure* in arterial end of capillary bed. Hydrostatic pressure *higher than oncotic pressure* so fluid is pushed out into surrounding tissues, forming tissue fluid. Most of plasma is pushed out *except for RBC's and plasma proteins.*
2) Diffusion takes place between blood and cells via tissue fluid.
3) *High oncotic pressure* in venous end of capillary bed due to plasma proteins generating *low water potential* in the blood. Hydrostatic pressure is low. *95% tissue fluid moves back into capillary via osmosis.* remaining 10% move back into lymphatic tissue.
63
How is hydrostatic pressure created?
by the pumping action of the heart and gravity and narrowing of the capillary wall
64
How does tissue fluid return to the blood plasma?
Loss of tf lowers hydrostatic pressure inside capillaries. When blood reaches venous end of capillary it's hydrostatic pressure is less than tissue fluid outside. Tf is then forced back into the capillary by the high hydrostatic pressure outside. Osmotic forces pull water back in
65
What happens when tissue fluid loses its nutrients?
Some goes into capillaries, others drain into the lymphatic system. The vessels start in tissues and eventually drain tissue fluid back into the blood stream
66
Lymph is moved by?
Hydrostatic pressure of the tissue fluid
Contraction of the body muscles aided by valves in lymph vessels
67
Difference between plasma, tissue fluid and lymph
Plasma- fluid in blood
TF- fluid in surrounding cells
Lymph- fluid in lymphatic system
68
Haemoglobin
a protein containing iron, found in red blood cells, which carries oxygen. Form of respiratory pigment
69
Structure of haemoglobin
4 polypeptide chains
- 2 alpha
- 2 beta
each chain has a haem group which contains a ferrous Fe2+ ion.
Quaternary
70
Loading of oxygen
The action of an oxygen molecule binding with a haemoglobin molecule. AKA associating. Happens at the lungs
71
Unloading of oxygen
The action of an oxygen molecule being released from a haemoglobin molecule. Aka dissociating. Happens at tissues
72
Haemoglobin efficiency
In order to be efficient haemoglobin needs to be able to readily associate (at gas exchange surface) and readily dissociate (at the tissues) from oxygen
73
High affinity
Associate easily and dissociate less easily
74
Low affinity
Associate less easily and dissociate easily
75
Haemoglobin in exchange surface
O2 conc: high
CO2 conc: low
Oxygen affinity: high
Associates
76
Ultrafiltration
The process where small molecules are forced from the blood out of the capillaries
77
Haemoglobin in respiring tissues
O2 conc: low
CO2 conc: high
Oxygen affinity: low
Dissociation
78
Why do different organisms require different Haemoglobin?
They have different metabolic rates
79
Haemoglobin summary
Oxygen changes it's affinity of oxygen under different conditions
It changes affinity and shape in the presence of CO2
CO2 causes O2 to bind loosely with Hb meaning O2 is able to dissociate more readily
80
Affinity
The attractive force binding atoms in molecules, chemical attraction
81
metabolic rate
the rate at which the body uses energy and works
82
partial pressure of a gas
The proportion of total pressure provided by a particular gas as part of a mixture of gases.
decreases with altitude
83
oxygen dissociation curve
represents the relationship between haemoglobin o2 saturation and pp of o2.
84
Why is the curve a sigmoid shape?
1st stage- low O2 means the 4 hb polypeptides are tightly packed so it is difficult to absorb the 1st oxygen molecule. Low O2= less O2 binding to Hb. Curve is shallow.
2nd stage- binding of 1st oxygen changes quaternary structure so molecules 2 and 3 load easier. It takes a smaller increase in pO2 for mol 2 to bind. Known as positive cooperativity
3rd stage- after 3rd O2 oxygen becomes more saturate so O2 loading is difficult due to probability
85
why do different animals have different oxygen dissociation curves?
different animals have different types of Hb with different oxygen affinities. the curves will be the same shape just shifted along the axis.
86
curve to the left
Curve (Left) = higher affinity, takes oxygen readily, releases slower
87
curve to the right
Right= lower oxygen affinity, takes oxygen up less readily, releases it easily.
88
Effects of CO2 concentration on oxygen dissociation curve
Haemoglobin has reduced affinity for oxygen in presence of CO2. This is the Bohr affect.
89
Haemoglobin behaviour in the lungs vs tissues
Lungs- high o2 affinity and low co2 levels
tissues- low o2 affinity and high co2 levels
90
Why does haemoglobin behave differently at the tissues compared to lungs?
high levels of CO2 form carbonic acid and a lower pH changes the shape of haemoglobin.
91
Why do organisms require different haemoglobin?
the environment-how much oxygen is available
metabolic rate- how much oxygen they use
92
low oxygen environment haemoglobin
Haemoglobin (hb) must have a high affinity for O2 so it can absorb enough. Organisms metabolic rate is low- slow release of O2 isn't a problem e.g mountain goats.
93
High oxygen environment haemoglobin
Hb have a low affinity for oxygen as there is plenty available so O2 dissociates readily. Organisms can have a high metabolic rate= low affinity.
94
A Left shift in Oxyhemoglobin Dissociation Curve
LEFT- loads easily
loves oxygen-> high affinity
low O2 around so needs to grab as much as possible
low metabolic rate (lazy)
95
Right shift of oxyhemoglobin dissociation curve
RIGHT- low affinity for oxygen
Doesn't load easily.
Releases oxygen easily
Good in respiring tissues
96
Why do plants require a mass transport system?
Large and multicellular
Small SA:V ratio so can't rely on diffusion
97
What molecules are transported in a plant?
Water, glucose
98
What are the 2 main vessels that enable this movement?
Xylem and Phloem
99
Xylem
Hollow thick walled tubes
Carry water from roots to the leaves by evaporation
100
What causes evaporation?
heat from the sun
101
Stomata
Small openings on the underside of a leaf through which oxygen and carbon dioxide can move
102
Movement of water across leaves
Humidity of the atmosphere is usually lower than the air next to the stomata which causes a water potential gradient. Stomata open-> water vapour diffuses out of air spaces
103
In terms of water potential gradients and osmosis, explain why this movement occurs
Mesophyll cell's lose water to air spaces due to
evaporation.
These cells nowhave a lower water potential. Water then enters them by these cells osmosis from following cells. The loss of water from cells lowers their water potential. They take up water from their neighbor Cells via osmosis.
This establishes a WP gradient that pulls water from the Xylem, aces the leaf I out to the atmosphere
104
Cohesion-tension
molecules of water tend to stick to each other due to hydrogen bonds. Continuous column of water is formed across the mesophyll and down the xylem. Column doesn't break because of adhesion to xylem wall, continues to pick up water molecules
105
Why is water pulled out of the xylem?
Because of transpiration pull- puts the xylem under tension and negative pressure
106
Experimental evidence- tree trunk diameter
During the day when transpiration is at its highest, xylem is under more pressure and tension so it pulls walls inwards
107
Experimental Evidence- broken xylem means no more water drawn up the stem
Continuous column of water is broken so water molecules no longer stick together
108
Experimental evidence- when breaking a xylem water doesn't leak out but air is pulled in
Air is sucked in which proves xylem is under tension. If there was no tension then water would leak out
109
Why are xylem vessels dead?
Water moves through the plant passively so the cells don't need to be alive to provide energy for this process
110
Why do xylem vessels have no end walls?
Allows them to form long, continuous, unbroken tubes from roots to leaves. Essential for cohesion tension
111
How do you measure rate of transpiration?
Using a potometer- volume of water absorbed
Decrease in mass due to water loss
112
Potometer experiment
1) take air bubble into capillary tube
2) as water moves into shoot and evaporated from leave air bubbles move to plant.
3) measure how fast air bubble travels and this will show you how fast it transpires.
4) refill tube and repeat while changing environmental conditions.
113
Describe and explain the relationship between humidity and transpiration rate (3 marks)
As humidity increases, transpiration rate decreases. High humidity means more water in the air (increased WP). Leads to a decreased diffusion gradient so there will be a slower rate of water loss
114
What is translocation?
The process by which organic molecules and some mineral ions are transported from one part of a plant to another through the phloem
115
Substances transported by phloem
sugars like sucrose and amino acids
Inorganic ions: potassium, chloride, phosphate and magnesium
116
Phloem structure
- consists of living sieve tube elements and companion cells
- sieve tube elements align end to end and are connected by a sieve plate
- each sieve tube element is close to a companion cell
- companion cells produce ATP for loading of sucrose into sieve tube elements
- cytoplasm of companion cell linked to sieve tube elements by gaps in the cell walls called plasmodesmata
117
Sources
The production site of sugars
118
Sinks
Where the sugars will be used or stored
Can be anywhere in a plant
119
Why is diffusion not responsible for translocation?
Molecules move very fast- too fast for it to be through diffusion
120
Mass flow theory- 3 key stages
1- transfer of sucrose into sieve elements from photosynthesising tissue
2-mass flow of sucrose through sieve tube elements
3-transfer of sucrose from sieve tube elements into storage or sink cells
121
Transfer of sucrose into sieve elements from photosynthesising tissue
1. Sucrose diffuses into companion cell by facilitated diffusion
2. Hydrogen ions are actively transported out of the companion cells into cell walls
3. They diffuses through carrier proteins into sieve tube elements
4. Hydrogen ions pull sucrose with them
122
Mass flow of sucrose through sieve tube elements
The active transport of the sucrose causes a lower water potential in the sieve tubes
Water then moves from the xylem into the sieve tubes via osmosis which creates a high hydrostatic pressure in the sieve tubes
Regions by the sink have a lower hydrostatic pressure
This creates a high hydrostatic pressure by the source and a lower hydrostatic pressure at the sink
This causes sucrose to flow down this pressure gradient. Sucrose is actively transported into sink cells as equilibrium is reached and it decreases WP making water follow.
123
Transfer of sucrose from the sieve tube elements into storage or other sink cells
The sucrose is actively transported by companion cells, out of the sieve tubes and into the sink cells.
124
Mass flow theory: evidence for
Sap is released when stems are cut
Concentration of sucrose is higher in leaves than roots
Downward flow of phloem occurs in daylight
Sucrose levels in the leaf increase before levels in phloem increase
Metabolic poisons and lack of oxygen inhibit translocation
Companion cells have lots of mitochondria
125
Evidence for- Sap is released when stems are cut
there is pressure inside the sieve tubes which forces sap out of the stems
126
Evidence for- Concentration of sucrose is higher in leaves than roots
leaves are a source and roots are a sink
127
Evidence for- downward flow of phloem occurs in daylight
as plant photosynthesises it produces glucose. Stops in shade
128
Evidence for- Sucrose levels in the leaf increase before levels in phloem increase
made in leaf then transported in the phloem
129
Evidence for- Metabolic poisons and lack of oxygen inhibit translocation
would prevent respiration which is required to provide the energy for active transport
130
Evidence for- companion cells have lots of mitochondria
need mitochondria to produce the atp needed for active transport
131
ringing experiments prove transport in phloem
phloem is removed, xylem remains.
sucrose transported down from site of production in leaf accumulates above ring (can be sampled or thickening of tissue noted)
132
Tracer Experiments: Phloem
trace movement of sucrose. blackened area corresponds with location of sucrose. Blackened areas are only in the phloem
133
aphid experiments
proboscis of aphid used to collect sap from phloem. used to work out sap flow rate. Shows sucrose is made in the leaves and travels into phloem
134
Structure:function- sieve plates with pores
allows for the continous movement of the organic compounds
135
Structure:function- cellulose cell wall
Needed for structure and stability- wall strengthened to withstand hydrostatic pressure
136
Structure:function- no nucleus, vacuole or ribosomes
more space available to maximise translocation space
137
Structure:function- thin cytoplasm
reduces friction to facilitate movement of assimilates
