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AQA A Level Biology > Organisms exchange substances with their environment > Flashcards

Organisms exchange substances with their environment Flashcards

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1
Q

Generally is it good or bad to have a large SA:volume ratio?

A

Generally the larger the better

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2
Q

What adaptation may an organism have to maximise SA to volume ratio?

A

Flattened shape

Specialised exchange surface (e.g. lungs) which are also often adapted to maximise diffusion

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3
Q

Having large ears would do what to the heat loss of an organism?

A

Increase it

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4
Q

Describe the gas exchange system in insects

A

Each segment has spiracles (pair of lip like opening)
These lead to trachea, which are supported by strengthened rings to stop the from collapsing
These divide into smaller tubes called tracheoles which lead to each individual cell

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5
Q

Give the three ways in which respiratory gases move in and out of the tracheal system

A

Along a diffusion gradient
Mass transport
Ends of tracheoles filled with water

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6
Q

Describe how respiratory gases move in and out of the tracheal system along a diffusion gradient

A

Cells respire and use up O2, therefore the O2 conc. towards the tracheal ends fall
Creates a diffusion gradient whereby O2 gas diffuses for the atmosphere along the trachea and tracheoles to the cells
Also creates diffusion gradient in opposite direction involving CO2

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7
Q

Describe how respiratory gases move in and out of the tracheal system by mass transport

A

Muscles contract and squeeze the trachea
Allows mass movement of air
Speeds it up

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8
Q

Describe how respiratory gases move in and out of the tracheal system due to the end of the tracheoles are filled with water

A

During major activity the muscle cells around the tracheoles carry out some anaerobic respiration
The lactate produced leaves the water potential of the cells, therefore water moves into the cells from the tracheoles by osmosis
Water vol. in tracheoles decreases therefore air drawn in

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9
Q

Describe and explain the adaptations of the fish gas exchange system

A

Gills made of lamellae which are covered in filaments - increase SA
Thin epithelium - short diffusion distance
Counter current flow, water pumped over gills - maintain conc. gradient

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10
Q

How do fish ventilate their gills?

A

By moving their mouths and opercula, they pump water over their gills, which ventilate them

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11
Q

Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish (3) PPQ

A

Water and blood flow in opposite directions;

  1. Maintains concentration/diffusion gradient / equilibrium not reached / water always next to blood with a lower concentration of oxygen;
  2. Along whole/length of gill/lamellae;
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12
Q

How do insects prevent water loss?

A

Spiracles are able to close
Body covered with waterproof waxy cuticle
Small SA : V ratio

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13
Q

How are leaves adapted for diffusion?

A

Many stomata - more gas in, short diffusion distance
Many interconnecting air spaces - gases readily in contact with cells
Large SA of mesophyll cells

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14
Q

How is gas exchange in plants similar to that in insects?

A

No living cell is far from the external air (and therefore a O2 and CO2 source)
Diffusion takes place in the gas phase (quicker than in water)

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15
Q

Describe and explain the way xerophytic plants are adapted

A 
Rolled up leaves
Hairy leaves
Stomata in pits/grooves
All these reduce by transpiration by reducing the gradient of water potential by trapping moist air to the surface
Thick waxy cuticle
A reduced SA:V of the leaves
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16
Q

What is a xerophyte?

A

A plant adapted to dry conditions

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17
Q

How does rolled up leaves prevent water loss?

A

Protects lower epidermis from outside
Helps trap air inside
As inside becomes saturated with water, conc. gradient decreases

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18
Q

How do hairy leaves prevent water loss?

A

Traps moist air next to leaf surface
Reduces water potential gradient b/wn inside and outside of leaf
Less water loss by transpiration

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19
Q

How does having stomata in pits prevent water loss?

A

Protects stomata from outside

Traps moist air in gap - reduces water potential gradient

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20
Q

Why are lungs located inside the body?

A

Air not dense enough to support these delicate structure

Body as a whole would lose a lot of water

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21
Q

How are the alveolus adapted to aid diffusion?

A

Lined with epithelium (site of gas exchange)
++ SA
Lined with ++ capillary network - maintains good conc. gradient

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22
Q

Describe how inhalation occurs

A

External intercostal muscles contract whilst the internal intercostal muscles. relax
Ribs are pulled upwards and outwards, increasing the volume of the thorax
Diaphragm muscles contract, causing it to flatten, which also increases the volume of the thorax
Increased vol of thorax results in reduction of pressure in the lungs
Atmospheric pressure is now greater than pulmonary pressure, and so air is forced into the lungs

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23
Q

Describe how expiration occurs

A

Internal intercostal muscles contract, external ones relax
Ribs move downwards and inwards –> decrease vol of thorax
Diaphragm muscles relax - pushed up against abdo –> decreases vol of thorax
Decreased vol of thorax increases pressure in lungs
Pulmonary pressure now greater than atmos - air forced out of lungs

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24
Q

How do you calculate pulmonary ventilation rate?

A

PVR = breathing rate x tidal volume

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25
Q

How is the body adapted for gas exchange?

A

RBCs slowed –> ++ time for diffusion
RBCs flattened against capillary walls –> reduces distance b/w RBC and alveolar air
Thin alveoli and capillary wall –> reduces diffusion distance
Alveoli and pulmonary capillaries both have large overall SA
Lungs constantly ventilated and constant blood circulation –> steep conc. gradient

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26
Q

What is the function of the oesophagus?

A

Carries from the mouth to the stomach

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27
Q

What is chemical digestion?

A

The process by which large, insoluble molecules are hydrolysed into smaller, soluble ones

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28
Q

What is the role of the stomach in digestion?

A

Store and digest food (especially proteins)

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29
Q

What is the role of the ileum in digestion?

A

Releases more enzymes to further digest

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30
Q

How is the ileum adapted for diffusion?

A

Villi and microvilli increases SA
Good blood supply maintain high gradient
Thin walled - short diffusion distance
Contain muscle and so are able to move - maintain diffusion gradient, mixes content

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31
Q

Lipases do what to lipids?

A

Hydrolyse them into glycerol and fatty acids

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32
Q

Proteases do what?

A

Hydrolyse proteins ultimately into amino acids

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33
Q

Carbohydrases do what?

A

Hydrolyse carbohydrates ultimately into monosaccharides

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34
Q

Describe the process of carbohydrate digestion

A

Salivary glands release saliva which contain salivary amylase - hydrolyse starch to maltose
Also mineral salts which maintain neutral pH (optimum)
Food swallowed and enters stomach, acid denatures
Moves into small intestine, where it mixes with pancreatic juice that contains pancreatic amylase - hydrolyses any remaining
Reaches ileum - membrane disaccharidase - maltose to a glucose

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35
Q

Why is the maltase in the ileum known as a membrane bound disaccharidase?

A

It is part of the cell-surface membranes of the epithelial cells rather than being released

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36
Q

Describe the process of lipid digestion

A

Lipids firstly split into micelles by bile salts from the liver in a process known as emulsification - increases SA and so hydrolysis into fatty acids and monoglycerides by lipases

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37
Q

Where are lipase produced?

A

Pancreas

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38
Q

Proteins are hydrolysed by a group of enzymes known as peptidases. What is an endopeptidase?

A

Enzymes which hydrolyse peptide bonds b/w amino acids in the central region of a protein molecule forming a series of peptide molecules

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39
Q

Proteins are hydrolysed by a group of enzymes known as peptidases. What is an exopeptidase?

A

Enzymes which hydrolyse peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases - progressively release dipeptides and single amino acids

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40
Q

Proteins are hydrolysed by a group of enzymes known as peptidases. What is a dipeptidase?

A

Enzymes which hydrolyse the bond b/w 2 amino acids of a dipeptide

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41
Q

How are amino acids and monosaccharides absorbed?

A

Diffusion and co-transport

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42
Q

How are triglycerides absorbed?

A

Monoglycerides and fatty acids in combo w/ bile salts –> micelles
Micelles come into contact w/epithelial cells and break down - release fatty acids and monoglycerides - non-polar and so can diffuse into cell
Transported to ER - recombo as triglycerides
Associate w/ cholesterol and lipoproteins to form chlorymicrons (adapted for lipid transport)
Chloryms move out of cell by exocytosis
Enter lymphatic capillaries called lacteals
Pass into blood system
Triglycerides hydrolysed in endothelial cell - diffuse in

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43
Q

How do chylomicrons move out of epithelial cells?

A

Exocytosis

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44
Q

Where do chylomicrons go after leaving the epithelial cell (during digestion)?

A

Lacteals (lymphatic capillaries)

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45
Q

What is haemoglobin?

A

A protein with a quaternary structure that transports oxygen in animals

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46
Q

Describe the structure of haemoglobin

A

Quaternary structure which forms an almost spherical molecule
Polypeptides associated w/ a haem group containing a ferrous ion (Fe 2+)

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47
Q

What is the role of haemoglobin?

A

To transport oxygen in the blood (in animals)

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48
Q

What is loading/associating (with regards to Hb)?

A

The process by which Hb binds with oxygen

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49
Q

Where does loading take place? (Hb)

A

In the lungs

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50
Q

What is unloading/dissociating (with regards to Hb)?

A

The process by which Hb releases O2

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51
Q

What does it mean when Hb has a high affinity?

A

It has a strong chemical attraction to O2 and so can take up O2 easily
However, releases less easily

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52
Q

What does in mean when Hb has a low affinity?

A

It has a weak chemical attraction to O2 and so can take up O2 less easily
However, releases more easily

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53
Q

What will the O2 affinity of Hb be like for an animal living in an area with low oxygen levels?

A

High affinity - needs to be able to take up easily

54
Q

What will the O2 affinity of Hb be like for an animal that has a low metabolic rate?

A

Low affinity - needs to be able to release easily, but doesn’t necessarily need to be able to take up easily

55
Q

How does Hb affinity change under acidic conditions?

A

Decreases (low affinity)

56
Q

How does Hb affinity change under low CO2 conditions?

A

Increases (high affinity)

57
Q

What is the Bohr effect?

A

The observation that Hb’s O2 binding affinity is related to acidity and the conc. of CO2

58
Q

Give a general formula to show the association and dissociation of Hb with oxygen

A

Hb + 4O2 <==> Hb(O2)4

59
Q

Describe and explain Hb’s O2 loading affinity at the gas exchange surface

A

High affinity
High O2 conc and low CO2 conc
O2 easily associates

60
Q

Describe and explain Hb’s O2 loading affinity at the respiring tissues

A

Low affinity
Low O2 conc but high CO2 (Bohr effect, acidity decrease affinity)
O2 readily dissociates

61
Q

The positive cooperative nature of oxygen means what? (With regards to Hb binding)

A

The binding of the first oxygen makes binding of further oxygens easier

62
Q

Why is it difficult for the 4th O2 molecule to bind to Hb?

A

The low probability of O2 finding an empty site to bind to

63
Q

Describe and explain a general oxygen dissociation curve

A
  • Hb shape makes it hard to bind (all subunits close together) therefore at low O2 conc, little O2 binds (shallow gradient)
  • 1st O2 binding changes 4* structure and so shape - makes it easier for other to bind (positive cooperativity), therefore a smaller increase in partial pressure of O2 is required to bind the 2nd O2 than the 1st
  • 4th molecule hard to bind bc low probability of O2 finding an empty binding site - increase decreases to straight line (‘tails off’)
64
Q

Why is blood passed through the heart twice in mammals?

A

When blood passed through lungs, its pressure is reduced

If pressure was not increased via the heart, circulation would be v. slow

65
Q

What kind of circulatory system do mammals have?

A

Closed, double circulatory

66
Q

Which blood vessel carries deoxygenated blood from the heart to the lungs?

A

Pulmonary artery

67
Q

Which blood vessel carries deoxygenated blood from the body to heart?

A

Vena cava

68
Q

Which blood vessel carries deoxygenated blood from the kidneys to the main venous system?

A

Renal veins

69
Q

What general system of vessels carries deoxygenated from the respiring tissues to the heart?

A

Veins

70
Q

Which blood vessel carries oxygenated blood from the lungs to the heart?

A

Pulmonary vein

71
Q

Which blood vessel carries oxygenated blood from the heart to the kidneys?

A

Renal artery

72
Q

What is the general name of blood vessels that carry blood away from the heart to the respiring tissues?

A

Arteries

73
Q

What does the pulmonary vein do?

A

Carry oxygenated blood from the lungs to the heart

74
Q

What does the pulmonary artery do?

A

Carry deoxygenated blood from the heart to the lungs

75
Q

What does the vena cava do?

A

Carry deoxygenated blood from the rest of the body to the heart

76
Q

What do veins do?

A

Carry deoxygenated blood from the rest of the body to the heart

77
Q

What do arteries do?

A

Carry oxygenated blood away from the heart, to the respiring tissues

78
Q

If you were standing opposite someone and looking at their heart, what is the name of the bottom left chamber?

A

Right ventricle

79
Q

If you were standing opposite someone and looking at their heart, what is the name of the bottom right chamber?

A

Left ventricle

80
Q

If you were standing opposite someone and looking at their heart, what is the name of the top right chamber?

A

Left atrium

81
Q

If you were standing opposite someone and looking at their heart, what is the name of the top left chamber?

A

Right atrium

82
Q

Which blood vessel carries oxygenated blood away from the heart to all parts of the body except the lungs?

A

The aorta

83
Q

What does the aorta do?

A

Carries oxygenated blood away from the heart to all parts of the body except the lungs

84
Q

Where is the bicuspid valve found?

A

Between the left atrium and left ventricle

85
Q

Where is the tricuspid valve found?

A

Between the right atrium and right ventricle

86
Q

Where is the pulmonary valve found?

A

In the pulmonary artery

87
Q

Which chamber of the heart is the vena cava connected to?

A

The right atrium

88
Q

Which chamber of the heart is the aorta connected to?

A

Left ventricle

89
Q

Which chamber of the heart is the pulmonary artery connected to?

A

Right ventricle

90
Q

Which chamber of the heart is the pulmonary vein connected to?

A

Left atrium

91
Q

Describe the general structure of the atria

A

Thin walled, elastic

92
Q

The atria are thin walled and elastic. Explain why

A

Able to expand as they are filled with blood

93
Q

Describe the general structure of the ventricles

A

Thick, muscular wall

94
Q

The ventricles have a thick, muscular wall. Explain why

A

They have to contract to pump the blood round the heart.

95
Q

The left ventricle has a thicker, more muscular wall than the right ventricle. Why is this?

A

The right ventricle is just contracting enough to push blood to the lungs. The left has to contract enough to push blood round the whole body

96
Q

What is the role of coronary arteries?

A

They supply the heart with blood

97
Q

What are the sounds the heart makes during its cardiac cycle?

A

Lub-dupp

98
Q

The ‘lub’ sound refers to what part of the cardiac cycle?

A

Contraction of ventricles and closing of AV valves

99
Q

The ‘dupp’ refers to what part of the cardiac cycle?

A

Semilunar valves closing

100
Q

Describe what happens during atrial diastole

A

All muscles relaxed and all heart valves closed

Blood returns to atria so pressure in atria increases

101
Q

Describe what happens during atrial systole

A

Atria contracts
AV valves open
Blood moves into the ventricles and so pressure in the atria decreases, in the ventricle increases

102
Q

Describe what happens during ventricular systole

A

Ventricles contracting
Semilunar valves open
Blood passed to arteries

103
Q

What are the two atrioventricular valves?

A

Tricuspid and bicuspid/(mitral) valve

104
Q

What are the two semilunar valves?

A

Aortic valve and pulmonary valve

105
Q

Describe what happens during ventricular diastole

A

All heart muscles in relaxation and all heart valves closed

Blood returning to atria

106
Q

How do you calculate cardiac output?

A

Heart rate x stroke volume

107
Q

How do you calculate heart rate?

A

Cardiac output divided by stroke volume

108
Q

What are the units for cardiac output?

A

dm-3 min-1

109
Q

What are the four phases of the cardiac cycle?

A

Atrial diastole, atrial systole, ventricular systole, ventricular diastole

110
Q

How does the structure of an artery relate to its function?

A

Thicker muscle than veins - smaller can be constricted/dilated to control blood flow
Relatively thick elastic layer - maintain high blood pressure
Overall thick wall - prevent bursting
Generally no valves - high pressure so little risk of back flow

111
Q

Why do arteries have a relatively thicker muscle layer than veins?

A

So the smaller arteries can be constricted and dilated in order to control the volume of blood passing through them

112
Q

Why do arteries have relatively thick elastic layers?

A

In order to maintain a high pressure - stretch and recoil action

113
Q

Why are arteries relatively thick walled?

A

Prevent bursting under high pressure

114
Q

Why don’t (most) arteries require valves?

A

Blood is constantly kept under high pressure

115
Q

How does the structure of an arteriole relate to its function?

A

Relatively thicker muscle layer than arteries - control of blood flow into capillaries
Relatively thinner elastic layer than in arteries - blood pressure is lower

116
Q

Why do arterioles have a relatively thicker muscle layer than arteries?

A

Contraction allows constriction/dilation of arteriole lumen - control of blood flow into capillaries

117
Q

Why do arterioles have a relatively thinner elastic layer than in arteries?

A

Blood pressure is lower than in arteries

118
Q

How does the structure of a vein relate to its function?

A

Relatively thinner muscle layer than arteries - veins carry blood away from heart so construction/dilation can’t control blood flow
Relatively thin elastic layer compared to arteries - low pressure of blood
Overall thickness of wall is small - no need for thicker, flattened easily to aid flow
Valves throughout - prevent back flow

119
Q

Why do veins have a relatively thinner muscle layer than arteries?

A

Veins carry blood away from the heart, therefore constriction/dilation can’t control blood flow to tissues

120
Q

Why do veins have a relatively thin elastic layer compared to arteries?

A

Low pressure of blood

Won’t burst and too low a pressure to recoil

121
Q

Why do veins have an overall small wall thickness?

A

No need for thicker as the blood pressure is low

Can be flattened easily to aid flow

122
Q

Why do veins have a valves throughout?

A

To ensure there is no back flow

123
Q

How is the structure of a capillary related to its function?

A

Walls mostly consist of lining layer - v. thin so short diffusion distance
Numerous and highly branched - can permeate tissues so no cell far from capillary so short diffusion distance
Narrow lumen - RBCS squeezed flat which increases SA and shortens diffusion distance
Spaces between lining cells - allows WBCs to escape to deal w/ infections in the tissue

124
Q

Why do capillary walls consist mostly of the lining layer?

A

V. thin so short diffusion distance

125
Q

Why does the numerous number and branches of capillaries aid it with its function?

A

Large SA

126
Q

Why do capillaries have narrow diameter?

A

So they can permeate tissues

This means no cell is far from a capillary and so there is a short diffusion distance

127
Q

Why do capillaries have a narrow lumen?

A

RBCs are squeezed flat against the capillary sides

This increases SA and reduces diffusion distance

128
Q

Why do capillaries have spaces between their endothelial (lining) cells?

A

To allow WBCs to escape to deal with infections within the tissue

129
Q

What does tissue fluid supply to the tissues?

A

Amino acids, glucose, fatty acids, ions in soln. and oxygen

130
Q

What is the role of tissue fluid?

A

The medium in which materials are exchanged between blood and cells
Provides constant surrounding cell environment

131
Q

What is tissue fluid formed from?

A

Blood plasma

132
Q

Describe how proteins are digested in the human gut PPQ

A
  1. Hydrolysis of peptide bonds;
  2. Endopeptidases break polypeptides into smaller peptide chains;
  3. Exopeptidases remove terminal amino acids;
  4. Dipeptidases hydrolyse/break down dipeptides into amino acids;

AQA A Level Biology (11 decks)

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