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A-Level Biology- Y12 > 3.3- Mass Transport > Flashcards

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

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2
Q

Suitable transport medium

A

Normally liquid but can also be gas e.g blood

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3
Q

Closed system of tubular vessels

A

contains medium and branch to all parts of an organism e.g. blood vessels

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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

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5
Q

How do animals move the transport medium?

A

muscular contractions, skeletal muscles or specialised pump

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6
Q

How do plants move the transport medium?

A

natural passive processes such as evaporation

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7
Q

What must both animals and plants have a method for?

A

to control flow direction and amount of flow

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8
Q

Fish circulatory system

A

2 chambers heart

single loop

blood flows from heart to gills to tissues to heart

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9
Q

Human circulatory system

A

heart, lungs, heart, body, heart

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10
Q

What is a double circulation system?

A

blood passes through the heart twice per circuit

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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

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12
Q

Circulatory system in mammals

A

high level activity and maintains temperature via respiration

2 circuits

pulmonary and systemic

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13
Q

Pulmonary circulation

A

flow of blood from the heart to the lungs and back to the heart

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14
Q

Systemic circulation

A

circulation that supplies blood to all the body except to the lungs

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15
Q

how many times does the heart beat a day?

A

100,000

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16
Q

myogenic

A

Describes muscle tissue (heart muscle) that generates its own contractions.

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17
Q

coronary arteries

A

blood vessels that branch from the aorta and carry oxygen-rich blood to the heart muscle

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18
Q

vena cava

A

a large vein carrying deoxygenated blood into the heart

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19
Q

pulmonary artery

A

Carries deoxygentated blood from the heart to the lungs

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20
Q

pulmonary vein

A

carries oxygenated blood from the lungs to the heart

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21
Q

aorta

A

The largest artery in the body. Carries oxygenated blood from the left ventricle to the rest of the body.

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22
Q

atrium

A

thin walls, collect blood from body or lungs

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23
Q

ventricles

A

thicker walls, capable of strong ejections from the heart

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24
Q

Cardiac Output equation

A

heart rate x stroke volume

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25
Q

Valves

A

prevent back flow of blood

Flexible, tough and fibrous

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26
Q

atrioventricular valves

A

between atria and ventricles

Prevent back flow of blood from contracting ventricles and force blood to leave the heart via aorta or pulmonary valve

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27
Q

Semi-lunar valve

A

Found in aorta and pulmonary valve to prevent ventricular backflle

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28
Q

Pocket valves

A

Found in veins - ensure that when veins are squeezed blood flows back towards the heart.

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29
Q

Open valves

A

Pressure is greatest on convex side of cusps

Valve opens

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30
Q

Closed valves

A

Pressure greater on concave side

Blood collects in cusps and forms a tight seal

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31
Q

Diastole

A

Relaxation of the heart

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32
Q

Systole

A

Contraction of the heart

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33
Q

Diastole phase

A

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

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34
Q

Atrial systole

A

Walls of atria contract at the same time so blood is pushed into ventricles and ventricle walls relax to receive blood

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35
Q

Ventricular Systole

A

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

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36
Q

Aortic Pressure in the Cardiac cycle

A

-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
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37
Q

Atrial Pressure in the Cardiac cycle

A

-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

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38
Q

Ventricular pressure in the Cardiac cycle

A

-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

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39
Q

Ventricular volume in the Cardiac cycle

A

-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

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40
Q

Arteries

A

carry blood away from the heart

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41
Q

Arterioles

A

small vessels that receive blood from the arteries and control blood flow to capillaries

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42
Q

Capillaries

A

Microscopic vessel through which exchanges take place between the blood and cells of the body

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43
Q

Veins

A

Blood vessels that carry blood back to the heart

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44
Q

Features of arteries, arterioles and veins

A

Tough fibrous outer layer, muscle layer, elastic layer, thin inner lining, lumen

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45
Q

Tough fibrous outer layer

A

Resists pressure changes from both within and outside arteries, arterioles and veins.

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46
Q

Muscle layer

A

Contracts to help blood flow be controlled

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47
Q

Elastic layer

A

Maintains blood pressure by stretching and recoiling

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48
Q

Thin endothelial lining

A

reduces friction for blood flow and provides a short diffusion surface

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49
Q

Lumen

A

a cavity or passage for blood

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50
Q

Why is the artery elastic layer much thicker than veins?

A

Elastic keeps bp high and arteries need a higher blood pressure to allow blood to travel throughout the body

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51
Q

Why do the arteries have no valves but veins do?

A

Blood is constantly under high pressure in arteries but under much lower pressure in veins so back flow is more likely

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52
Q

Why do veins have a thinner muscle layer?

A

they have lower pressure so don’t require lots of muscle to push blood through at high pressure

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53
Q

Why is the muscle layer in arterioles thicker than the layer in arteries?

A

Can construct and control the flow of blood into capillaries

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54
Q

Capillary function

A

allows for diffusion of nutrients and wastes between cells and blood

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55
Q

Capillaries- Walls consist of mainly lining layer

A

Makes the walls thinner. Short diffusion pathway= rapid diffusion

56
Q

Capillaries- numerous and highly branched

A

Provide a large sa for exchange

57
Q

Capillaries- narrow diameter

A

Can permeate tissues and get closer to cells

58
Q

Capillaries- Narrow lumen

A

RBC are squeezed flat against walls to decrease distance

59
Q

Capillaries- spaces between endothelial cells

A

Allow white bc to escape and get out

60
Q

Tissue fluid

A

The fluid surrounding the cells and tissues. Allows exchange. Made of blood plasma

61
Q

How else is tissue fluid known?

A

Interstitial fluid

62
Q

Formation of tissue fluid

A

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
Q

How is hydrostatic pressure created?

A

by the pumping action of the heart and gravity and narrowing of the capillary wall

64
Q

How does tissue fluid return to the blood plasma?

A

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
Q

What happens when tissue fluid loses its nutrients?

A

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
Q

Lymph is moved by?

A

Hydrostatic pressure of the tissue fluid

Contraction of the body muscles aided by valves in lymph vessels

67
Q

Difference between plasma, tissue fluid and lymph

A

Plasma- fluid in blood

TF- fluid in surrounding cells

Lymph- fluid in lymphatic system

68
Q

Haemoglobin

A

a protein containing iron, found in red blood cells, which carries oxygen. Form of respiratory pigment

69
Q

Structure of haemoglobin

A

4 polypeptide chains

  • 2 alpha
  • 2 beta

each chain has a haem group which contains a ferrous Fe2+ ion.

Quaternary

70
Q

Loading of oxygen

A

The action of an oxygen molecule binding with a haemoglobin molecule. AKA associating. Happens at the lungs

71
Q

Unloading of oxygen

A

The action of an oxygen molecule being released from a haemoglobin molecule. Aka dissociating. Happens at tissues

72
Q

Haemoglobin efficiency

A

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
Q

High affinity

A

Associate easily and dissociate less easily

74
Q

Low affinity

A

Associate less easily and dissociate easily

75
Q

Haemoglobin in exchange surface

A

O2 conc: high

CO2 conc: low

Oxygen affinity: high

Associates

76
Q

Ultrafiltration

A

The process where small molecules are forced from the blood out of the capillaries

77
Q

Haemoglobin in respiring tissues

A

O2 conc: low

CO2 conc: high

Oxygen affinity: low

Dissociation

78
Q

Why do different organisms require different Haemoglobin?

A

They have different metabolic rates

79
Q

Haemoglobin summary

A

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
Q

Affinity

A

The attractive force binding atoms in molecules, chemical attraction

81
Q

metabolic rate

A

the rate at which the body uses energy and works

82
Q

partial pressure of a gas

A

The proportion of total pressure provided by a particular gas as part of a mixture of gases.

decreases with altitude

83
Q

oxygen dissociation curve

A

represents the relationship between haemoglobin o2 saturation and pp of o2.

84
Q

Why is the curve a sigmoid shape?

A

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
Q

why do different animals have different oxygen dissociation curves?

A

different animals have different types of Hb with different oxygen affinities. the curves will be the same shape just shifted along the axis.

86
Q

curve to the left

A

Curve (Left) = higher affinity, takes oxygen readily, releases slower

87
Q

curve to the right

A

Right= lower oxygen affinity, takes oxygen up less readily, releases it easily.

88
Q

Effects of CO2 concentration on oxygen dissociation curve

A

Haemoglobin has reduced affinity for oxygen in presence of CO2. This is the Bohr affect.

89
Q

Haemoglobin behaviour in the lungs vs tissues

A

Lungs- high o2 affinity and low co2 levels

tissues- low o2 affinity and high co2 levels

90
Q

Why does haemoglobin behave differently at the tissues compared to lungs?

A

high levels of CO2 form carbonic acid and a lower pH changes the shape of haemoglobin.

91
Q

Why do organisms require different haemoglobin?

A

the environment-how much oxygen is available

metabolic rate- how much oxygen they use

92
Q

low oxygen environment haemoglobin

A

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
Q

High oxygen environment haemoglobin

A

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
Q

A Left shift in Oxyhemoglobin Dissociation Curve

A

LEFT- loads easily

loves oxygen-> high affinity

low O2 around so needs to grab as much as possible

low metabolic rate (lazy)

95
Q

Right shift of oxyhemoglobin dissociation curve

A

RIGHT- low affinity for oxygen

Doesn’t load easily.

Releases oxygen easily

Good in respiring tissues

96
Q

Why do plants require a mass transport system?

A

Large and multicellular

Small SA:V ratio so can’t rely on diffusion

97
Q

What molecules are transported in a plant?

A

Water, glucose

98
Q

What are the 2 main vessels that enable this movement?

A

Xylem and Phloem

99
Q

Xylem

A

Hollow thick walled tubes

Carry water from roots to the leaves by evaporation

100
Q

What causes evaporation?

A

heat from the sun

101
Q

Stomata

A

Small openings on the underside of a leaf through which oxygen and carbon dioxide can move

102
Q

Movement of water across leaves

A

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
Q

In terms of water potential gradients and osmosis, explain why this movement occurs

A

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
Q

Cohesion-tension

A

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
Q

Why is water pulled out of the xylem?

A

Because of transpiration pull- puts the xylem under tension and negative pressure

106
Q

Experimental evidence- tree trunk diameter

A

During the day when transpiration is at its highest, xylem is under more pressure and tension so it pulls walls inwards

107
Q

Experimental Evidence- broken xylem means no more water drawn up the stem

A

Continuous column of water is broken so water molecules no longer stick together

108
Q

Experimental evidence- when breaking a xylem water doesn’t leak out but air is pulled in

A

Air is sucked in which proves xylem is under tension. If there was no tension then water would leak out

109
Q

Why are xylem vessels dead?

A

Water moves through the plant passively so the cells don’t need to be alive to provide energy for this process

110
Q

Why do xylem vessels have no end walls?

A

Allows them to form long, continuous, unbroken tubes from roots to leaves. Essential for cohesion tension

111
Q

How do you measure rate of transpiration?

A

Using a potometer- volume of water absorbed

Decrease in mass due to water loss

112
Q

Potometer experiment

A

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
Q

Describe and explain the relationship between humidity and transpiration rate (3 marks)

A

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
Q

What is translocation?

A

The process by which organic molecules and some mineral ions are transported from one part of a plant to another through the phloem

115
Q

Substances transported by phloem

A

sugars like sucrose and amino acids

Inorganic ions: potassium, chloride, phosphate and magnesium

116
Q

Phloem structure

A
  • 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
Q

Sources

A

The production site of sugars

118
Q

Sinks

A

Where the sugars will be used or stored

Can be anywhere in a plant

119
Q

Why is diffusion not responsible for translocation?

A

Molecules move very fast- too fast for it to be through diffusion

120
Q

Mass flow theory- 3 key stages

A

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
Q

Transfer of sucrose into sieve elements from photosynthesising tissue

A
  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
Q

Mass flow of sucrose through sieve tube elements

A

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
Q

Transfer of sucrose from the sieve tube elements into storage or other sink cells

A

The sucrose is actively transported by companion cells, out of the sieve tubes and into the sink cells.

124
Q

Mass flow theory: evidence for

A

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
Q

Evidence for- Sap is released when stems are cut

A

there is pressure inside the sieve tubes which forces sap out of the stems

126
Q

Evidence for- Concentration of sucrose is higher in leaves than roots

A

leaves are a source and roots are a sink

127
Q

Evidence for- downward flow of phloem occurs in daylight

A

as plant photosynthesises it produces glucose. Stops in shade

128
Q

Evidence for- Sucrose levels in the leaf increase before levels in phloem increase

A

made in leaf then transported in the phloem

129
Q

Evidence for- Metabolic poisons and lack of oxygen inhibit translocation

A

would prevent respiration which is required to provide the energy for active transport

130
Q

Evidence for- companion cells have lots of mitochondria

A

need mitochondria to produce the atp needed for active transport

131
Q

ringing experiments prove transport in phloem

A

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
Q

Tracer Experiments: Phloem

A

trace movement of sucrose. blackened area corresponds with location of sucrose. Blackened areas are only in the phloem

133
Q

aphid experiments

A

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
Q

Structure:function- sieve plates with pores

A

allows for the continous movement of the organic compounds

135
Q

Structure:function- cellulose cell wall

A

Needed for structure and stability- wall strengthened to withstand hydrostatic pressure

136
Q

Structure:function- no nucleus, vacuole or ribosomes

A

more space available to maximise translocation space

137
Q

Structure:function- thin cytoplasm

A

reduces friction to facilitate movement of assimilates

A-Level Biology- Y12 (14 decks)

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