1
Q
how can single celled organisms exchange substances
A
- with the external environment by diffusion through the cell surface membrane
- they can do this due to short diffusion distances
2
Q
why is diffusion through the cell surface membrane enough for single celled organisms
A
- metabolic activity is usually relatively low
- surface area to volume ratio is large
- these mechanisms are enough to supply a single cell with everything it needs to survive
3
Q
example of a single celled organism
A
ameoba
4
Q
why can’t multi cellular organisms solely rely on diffusion of substances across the body surface to the cells in order to survive ?
A
- diffusion would be too slow as they are larger
- higher metabolic rate
- surface area to volume ratio is much smaller
- environment is a lot further away from the organisms centre
5
Q
why do animals need specialised transport systems
A
- they are very active and have high metabolic demands
- bigger SA:V ratio as they are bigger
- many molecules are produced in one part of the body but are needed in another part
- food is digested in digestive system but products of this is needed all over the body
- all cells produce waster products which must be transported to excretory organs
6
Q
how do you calculate surface area to volume ratio
A
surface area/volume :1
7
Q
give common exchange surfaces present in most animals
A
- increased surface area
- thin layers
- good blood supply
- ventilation to maintain diffusion gradient
8
Q
increased surface area -
A
provides the area needed for exchange and overcomes the limitations of SA:V ratio of larger organisms
- e.g villi, root hair cells
9
Q
thin layers -
A
diffusion distances are short
making process fast and efficient
- e.g alveoli in lungs
10
Q
good blood supply -
A
- steeper concentration gradient
- the faster diffusion takes place
- ensures substances are constantly delivered to and removed from exchange surfaces
maintaining steep concentration gradient
11
Q
ventilation to maintain diffusion gradient
A
for gases in a ventilation system, helps to maintain concentration gradient
makes process more efficient
e.g alveoli in lungs, gills of fish
12
Q
as the size of an organism increases, what happens to SA:V ratio
A
decreases
13
Q
why does the SA:V ratio decrease when organism size increases
A
- the distances substances need to travel from the outside to reach the cells at the centre of the body get longer
- making it hard for cells to absorb enough O2 through the available SA to meet needs of the body
14
Q
if exchange surfaces are thin and permeable enough what molecule is able to be let across
A
water
15
Q
why could water being able to cross exchange surfaces be a negative
A
- there is a risk of organisms losing water to the environment as it could evaporate from gas exchange surface
16
Q
in mammalian exchange systems, why do we keep the lungs deep inside of our body
A
so a much lower concentration gradient of water evaporates out of the body
17
Q
why are mammalian gas exchange surfaces moist ?
A
so O2 dissolves in the water before diffusion into body tissues
however these conditions are also good for evaporation of water
18
Q
why do mammals need an exchange system
A
- they are big an have a small SA:V ratio
- have a large volume of cells
- high metabolic rate
- maintain a constant body temperature independent of their environment
- need lots of O2 for respiration and removed CO2 from the lungs
19
Q
site of mammalian gas exchange
A
lungs
20
Q
lungs
A
inflatable sacs lying in the chest cavity
21
Q
how are lungs protected
A
ribcage
22
Q
how are ribs held together
A
intercostal muscles
23
Q
what do the intercostal muscles and diaphragm do
A
help to produce breathing movements
24
Q
name parts of the mammalian gas exchange system
A
nasal cavity
trachea
bronchus
bronchioles
alveoli
25
nasal cavity adaptations (just name)
- large SA with good blood supply
- hairy lining
- moist surfaces
26
nasal cavity - large SA with good blood supply - explain
warms the air to body temperature
27
nasal cavity - hairy lining - explain
secretes mucus to trap dust and bacteria
this protects delicate lung tissue from irritation and infection
28
nasal cavity - moist surfaces - explain
increases humidity of incoming air
this reduces evaporation from exchange surfaces
29
trachea
main airway carrying clean, warm air from the nose to the chest
30
trachea - structure
wide tube supported by incomplete rings of strong, flexible cartilage
- walls of smooth muscle
- elastic fibres
31
trachea - why is the cartilage useful
- supports trachea and stops it from collapsing
32
why are cartilage rings incomplete
to allow food to move down
33
what is the trachea lined with
ciliated epithelium and goblet cells
34
cilia
- hair like structures
- they beat the mucus secreted by goblet cells away from the alveoli to the throat where it is swallowed
- preventing lung infections
35
goblet cells
- secrete mucus trapping microorganisms and dust particles in the inhaled air
- stops them reaching alveoli
36
bronchus
- in chest cavity, trachea divides forming left and right bronchus
37
bronchus structure
similar to trachea - with some rings of cartilage, except smaller
- walls of smooth muscle
- elastic fibres
38
bronchioles
- bronchi divide to form bronchioles
39
bronchioles structure
- no cartilage rings
- walls of smooth muscle
- elastic fibres
40
smooth muscle
- controls diameter of walls
- when smooth muscle walls contract, structures constrict
- when smooth muscle walls relax, structures dilate
- controlling air volume of the lungs
41
elastic fibres
- aids process of breathing out
- when breathing in, elastic fibres stretch
- when breathing out, the fibres recoil to help push air out
- stretch and recoil mechanism
42
alveoli
tiny air sacs which are the main gas exchange surfaces of the body
43
alveoli - structure
- each alveolus has a diameter of 200-300 micrometres
- consists of a layer of thin, flattened epithelial cells along with some collagen and elastic fibres
44
what do the collagen and elastic fibres surrounding alveoli help them to do
stretch as air is drawn in
squeeze air out when they return to their normal size
= elastic recoil of the lungs
45
alveoli adaptations
- large SA
- thin layers
- good blood supply
- good ventilation
- inner surfaces covered in thin layers of water salts and lung surfactant
46
alveoli - explain - large SA
- the alveoli provides an average surface between the lungs of around 50-72 m2
= HUGE
- provides area needed for exchange and overcomes limitations of SA:V ratio
47
alveoli - thin layers - explain
- only 1 epithelial cell thick = short diffusion path
48
alveoli - good blood supply - explain
- around 280 million capillaries surround alveoli = transports O2 and CO2 maintaining a steep concentration gradient between air in the alveoli and blood in capillaries
49
alveoli - good ventilation - explain
- breathing moves air in and out of the alveoli = steep concentration gradient of oxygen and CO2 from air in lungs and blood in capillaries
- constantly refreshes oxygen supply
50
alveoli - inner surfaces covered in thin layer of water salts and lung surfactants - explain
- allows alveoli to stay inflated
- O2 dissolves into H20 before it goes into the blood, and water evaporates
51
ventilation
- air is moved in and out of the lungs
- as a result of pressure changes in the thorax
- brought about by breathing movements
52
pleural membrane
lines the thorax surrounding the lungs
53
pleural cavity
space between the lungs and pleural membrane, contains lubricating fluid so membrane slides easily
54
rib cage
provides a semi rigid case within which the pressure can be changed with respect to the air outside it
55
diaphragm
broad, domed sheet of muscle which forms the floor of the thorax
56
inspiration
taking air in
57
inspiration: active or passive
active
58
inspiration - step by step
1- external intercostal and diaphragm muscles contract
2- causes ribcage to move upwards and outwards and the diaphragm to flatten, increasing volume of the thorax
3- as volume of thorax increases, pressure decreases
4- air flows to lungs
59
active process
requires energy
60
expiration
process of breathing out
61
expiration - active or passive
passive
62
expiration - step by step
1- external intercostal and diaphragm muscles relax
2- ribcage moves downwards and inwards and diaphragm becomes curved again
3- thorax volume decreases causing air pressure to increase
4- air is forced out of the lungs
63
passive
does not require energy
64
when can expiration be active
when forced, e.g blowing out birthday candles
65
what happens during forced expiration
internal intercostal muscles contract, to pull ribcage down and in
66
asthma effects
airways sensitive to everyday triggers, e.g house dust mites, pollen etc
67
what happens to exchange surfaces during an asthma attack ?
- cells lining in bronchioles release histamines
- as a result airways narrow and fill with mucus making breathing difficult
68
histamines - what do they do
- make epithelial cells inflamed and swollen
- stimulate goblet cells to make excess mucus and smooth muscle walls in bronchioles contract
69
relivers
give relief to symptoms (of asthma)
70
what do relivers do
- they are chemicals similar to adrenaline
- attach to active sites of surface membranes of smooth muscle cells in bronchioles making them relax and dilating the airways
71
preventers (for asthma attacks)
often steroids
taken everyday to reduce sensitivity of the lining in the airways
72
what happens to the bells jar model when the rubber sheet is pulled down
- volume of bell jar increases
- decreasing pressure in bell jar
- causing pressure in bell jar to be less than the atmospheric pressure
- so air from the atmosphere is forced into the glass tube
- causing the balloons in the bell jar to inflate
73
how can the volume of air which is drawn in and out of the lungs be measured
peak flow meter
vitalograph
spirometer
74
peak flow meter
rate at which air can be expelled from lungs
75
vitalograph
more sophisticated peak flow meter
76
spirometer
measures different aspects of lung volumes, as well as to investigate breathing patterns
77
what does a spirometer produce
a trace showing different aspects of lung volume
78
steps of how a spirometer works
1- person breathes in and out through their mouth via mouthpiece
2- air is trapped between enclosed chamber between the float and the water
3- when breathing in, the volume of air in the chamber decreases and the float drops
4- when breathing out, the volume of air inside the chamber increases and float rises
79
in the spirometer what is the float attached to
a pen, which writes on paper on the revolving drum, recording breathing movements
80
if soda lime is used in spirometry, what happens
the carbon dioxide breathed out into the mouthpiece is absorbed so does not reach the chamber
81
tidal volume
volume of air in each breath
(usually 0.4 dm3)
82
vital capacity
maximum volume of air that can be breathed in and out in one breath
83
breathing rate
how many breaths taken per unit of time
84
oxygen uptake
rate at which a person uses up oxygen
(e.g, number of dm3 used/minute)
85
residual volume
the remaining air left in the lungs after the maximum amount of air has been forcibly expelled from the body
86
why is there always air left in the lungs
to prevent the lungs from collapsing
87
what rules should we follow when using a spirometer
- use a healthy volunteer
- block their nose
- make sure they are breathing in and out of their mouth normally
88
Inside the spirometer there is pure oxygen, why ?
aerobic respiration
89
why does the reading from the spirometer gradually decrease over time
oxygen is being used up
90
revolving drum
records movements of pen
91
inner chamber
filled with oxygen
rises and falls when air enters/leaves the chamber
92
canister
filled with soda lime
93
valves
maintain direction of flow
94
how do we calculate breathing rate on the spirometer
peak to peak = 1 breath
count the number of these per minute
95
how is oxygen uptake calculated
work out the gradient of the trace
96
what happens to the gradient of oxygen uptake during exercise
it gets steeper
97
how do we calculate the rate of reaction on a spirometer trace
x/y
98
how do we calculate pulmonary ventilation
tidal volume x breathing rate
99
how do we calculate ventilation rate
tidal volume x breathing rate
100
why do the participants need to wear a nose clip
so no air escapes the nose
so breathing can be measured and measurements are more valid and accurate
101
how would we use a spirometer to calculate someones tidal volume
- get subject to take normal breaths through the mouthpiece
- minimum of 3 breaths
- calculate mean
- use trace to measure volume 0f air breathed in and out
102
relationship between tidal volume, breathing rate and oxygen uptake
- ventilation rate = tidal volume of air breathed in x number breaths/min
- oxygen uptake is linked to this as the more air moved into the lungs = more oxygen uptake
103
what difficulties are there in trying to gain oxygen from water rather than air
- water is 1000 x denser than air
- water is 1000 x more viscous than air
- water has a lower oxygen concentration = smaller concentration gradient across exchange surface
104
what is the issue with water being more viscous than air
it can't move in and out of the lungs without using lots of energy
105
what gas exchange surface to fish use
gills
106
why do fish need a very efficient gas exchange mechanism
- they are very active - swimming
- high oxygen demands
- lots of carbon dioxide to get rid of
107
how many gills do fish have
4, on each side of their head
108
gils adaptations
- large SA
- good blood supply
- thin surface
109
where are gills found
within a gill cavity
covered by a flap called operculum
110
what does the operculum help to do
maintain a 1 way flow of water over the gills
- bringing in water with fresh oxygen
- carrying away water with carbon dioxide
111
gills - structure
- each gill is made up of 2 rows of gill filaments
- attached to bony gill arch
112
how do gills achieve a large surface area
- each gill filament is very thin
- surface is folded into gill lamellae
113
where does gas exchange take place in fish
gill lamellae
114
fish - counter-current system
- blood flows through gill plates in 1 direction
- water flows over in the opposite direction
115
how does the counter-current system ensure a steep concentration gradient is maintained between water and the blood
- water with relatively high oxygen concentration always flows next to blood with a lower oxygen concentration
- maximising diffusion
116
fish use their mouth and operculum flap to maintain a flow of water over their gills at all times, the tips of adjacent gill filaments overlap - how is this good
- increases resistance to the flow of water
- slows down water movement
- allowing more time for gas exchange
117
ventilation in bony fish - step by step - fish opening mouth
- fish opens their mouth
- lowering floor of buccal cavity
- increases volume of buccal cavity
- lowering pressure of buccal cavity
- water is then drawn into the buccal cavity due to pressure gradient
118
ventilation in bony fish - step by step - fish closing their mouth
- fish closes mouth
- floor of buccal cavity is raised
- volume inside buccal cavity falls
- pressure inside buccal cavity increases
- water is forced over gill filaments
- gas exchange occurs
- pressure forces open the flaps over operculum so water leaves gills
119
dissecting fish gills - step by step
1- place fish on dissection tray
2- push back operculum
3- use scissors to remove the gills
4- cut each gill arch through the bone at the top and bottom
5- gill filaments should be visable
120
why do insects have high oxygen demands
they are very active (flight)
121
why can't gas exchange occur across insects body surface
they have a hard exoskeleton
122
what type of circulatory system do insects have
open circulatory system
123
open circulatory system
no blood or blood vessels
oxygen is delivered directly to cells
124
spiracles
small opening where air enters and leaves the insect
125
trachae
tube which carries air into the body
126
what is trachae lined with
rings of chitin
127
tracheoles
smaller tubes
elongated single cell with no chitin
tubes lead directly to insect tissues
site of gas exchange
128
insect pathway of air
- air enters through spiracles
- oxygen diffuses down concentration gradient along the trachea
- trachea branches into trachae then tracheoles
- tracheoles have thin walls which lead directly into insect tissues, where oxygen diffuses into
129
in insects, what helps to maintain a high concentration gradient
ventilation
130
chitin
similar function to cartilage
provides support
keeps tubes open even if they are bent or pressed
131
how are tracheoles adapted for insects
single celled
thin
short diffusion distance
132
tracheoles adaptations insects
- branches
- gives large SA
- greater surface for gases to diffuse from
- large number of these
133
towards the end of each tracheole there is tracheal fluid - why is this bad
prevents air getting to the very ends of tracheoles, near the cells
134
how can insects overcome tracheal fluid
- when they are active
- because respiration rate increases
- some anaerobic respiration happens, producing lactic acid in body cells
135
how can lactic acid produced by insects during anaerobic respiration reduce the volume of tracheal fluid in tracheoles
- water moves out by osmosis
- exposing more surface area for gas exchange
136
what do sphincter muscles do
surround the spiracles of an insect
causes them to open and close
137
why are sphincter muscles important
- to control extent of gas exchange
- and maximise this whilst minimising water vapour loss from gas exchange surface
138
when inactive, sphincter muscles close spiracles - why
- to save water
139
when active - sphincter muscles open spiracles - why
- to allow more oxygen in
- however some water vapour will leave
140
how is water loss reduced in insects
they are covered in waxy cuticle to reduce evaporation
insects can close their spiracles
141
ventilation in insects helps to maintain a steep concentration gradient, how ?
- large insects = by moving body can ventilate tracheal system
- sections of tracheal system can be expanded and have flexible walls which act as air sacs which can be squeezed by the action of the flight muscles
- movements of wing alters thorax volume
142
some insects such as Locusts can alter volume of abdomen - how does this aid ventilation
- as abdomen expands, spiracles at front end of body open and air enters tracheal system
- as abdomen reduces in volume spiracles at rear end open and air leaves tracheal system
143
a level biology
flashcards
Decks in class (33)
# Cards
-
PAG - Identifying mystery substances using biochemical tests19
-
PAG - Extraction of DNA25
-
PAG- Finding the concentration of glucose in urine using a colorimeter16
-
PAG - The effect of ethanol concentration on membrane permeability14
-
PAG - Dissection of a heart16
-
PAG - Determination of water potential by measuring changes in mass10
-
PAG - Investigation into the effect of substrate concentration on enzyme activity11
-
PAG - Using aseptic technique to investigate the use of antimicrobials24
-
Investigating transpiration using a potomoter16
-
Microscopy - preparing slides3
-
Key Question - how effective are the current clinical treatments for schizophrenia40
-
Cell biology92
-
Biological molecules273
-
nucleic acids130
-
Enzymes168
-
Cell cycle137
-
Biological membranes114
-
Organisation and Specialisation of cells121
-
Exchange surfaces143
-
Transport in animals226
-
Transport in plants154
-
Classification209
-
Biodiversity252
-
Communicable diseases, disease prevention, and the immune system173
-
Neuronal Communication68
-
Plant responses45
-
Respiration40
-
Cellular Control171
-
Inheritance141
-
Manipulating genomes91
-
Cloning and Biotechnology71
-
Ecosystems200
-
Populations and Sustainability215
