1
Q
What is the environment around the cells of multicellular organisms called?
A
Tissue fluid
2
Q
What is the surface area to volume ratio like for small organisms and why is this?
A
very large SA comapred to VOL
this means there is a big surface for exchange but there is a smaller distance from the outside of the organism to the middle of it
so dont need specialised systems
3
Q
What 2 factors affect the amount of material that is exchanged?
A
size
metabolic rate
4
Q
What is the surface area to volume ratio like in larger organisms?
A
smaller SA:VOL
need specialised exchang systems
5
Q
Smaller mammals have a high SA:VOL so lose heat rapidly. How do they replace heat that is lost?
A
They have a higher rate of metabolism and respiration
This providses energy for more heat and maintains a stable body temperature
6
Q
What are examples of things that need to be interchanged between an organism and its environment?
A
- respiratory gases (oxygen and carbon dioxide)
- nutrients (glucose, fatty acids, amino acids, vitamins)
- excretory products (urea and carbond dioxide)
- heat
7
Q
Why do larger animals have a lower metabolic rate?
A
thy lose heat slowly due to lower surface area to volume ratio
8
Q
In a cell, whre is the lowest concentration of oxygen?
A
in thee mitochondria
it also has the highest concentration of carbon dioxide
to maintain diffusion gradient
9
Q
What are some adaptations to increase surface area:volume for absorption and gas exchange?
A
- villi and mircrovilli - absorption
- alveoli and brionchioles
- spiracles and tracheols
- gill filaments and lamellae
- thin wide leaves
- many capillaries
10
Q
What are the 2 ways things can be exchanged?
A
- passively - no metabolic energy required
done by diffusion and osmosis - actively - metabolic energy is required
done by active transport
11
Q
What are 5 features of specialised exchange surfaces?
A
-large surface area relative to volume
- thin - short diffusion pathway
-selectively permeable
- movement of environmental medium eg air to maintain diffusion gradient
-a transport system to maintain diffusion gradient
12
Q
What are the 5 key components of the human gas exchange system?
A
- alveoli
- bronchioles
- bronchi
- trachea
- lungs
13
Q
How is ventilation controlled?
A
by the diaphragm muscle and the antagonistic interaction between the external and intercostal muscles
14
Q
Explain the process of inspiration
A
external intercostal muscles contraact to pull the ribs up and out
internal interecostal muscles relax
diaphragm contracts to move down and flattens
volume of thorax increases as a result
air pressure in lungs decreases
air moves into lungs as atmospheric pressure is higher than the thorax
15
Q
Explain the process of expiration
A
external intercostal muscles relax
internal intercostal muscles contract to pull the rib down and in
diaphragm relaxese to move up and dome
volume of thorax decreases as a result
air pressure in lungs decreases
air moves of the lungs as the pressure in the thorax is higher than the atmosphere
16
Q
Only under more strenuous conditions like exercise do the muscles force air out. So, what causes during normal breathing what does this?
A
the recoil of the elastic tissure in the lungs
17
Q
What is pulmonary ventilation?
A
the total volume of air that is moved into the lungs during one minute
18
Q
Why do all aerobic organisms need to respire?
A
They require a constant supply of oxygen to release energy in the form of ATP
the carbon dioxide needs to be removed as it could be harmful
19
Q
Why do larger organisms need to absorb more oxygen and remove more carbon dioxide?
A
they have a large volume of living cells
and
they maintain a high body temperature which is related to them having high mtabolic and respiratory rates
20
Q
Why are lungs located inside the body?
A
- air is not dense enough to support and protect their delicate structures
- the body would lose a great amount of water and dry out
21
Q
What supports and protects the lungs?
A
the ribcage
22
Q
Describe the structure of the lungs
A
made up of highly branched bronchioles which end in tiny air sacs called alveoli
23
Q
What is the trachea?
A
flexible airway supported by rings of cartilage
made up of muscle lined with ciliated epithelium and goblet cells
24
Q
Why is the trachea supported by rings of cartilage?
A
prevents it from collapsing as the air pressure inside falls when breathing in
25
What is the bronchi?
2 divisions of the trachea leading to each lung
supported by cartilage
lined with epithelium and goblet cells
26
What is the purpose of ciliated epithelium and goblet cells in the trachea and bronchi?
goblet cells - produce mucus to trap dirt particles
cilia - move mucus upwards towards the throat
27
What are the bronchioles?
branching subdivisions of the bronchi
made of muscle lined with epithelial cells
28
Why do bronchioles have walls made of muscle?
to constrict so that they can control the flow of air in and out of the alveoli
29
What are alveoli?
air sacs at the end of the bronchioles
lined with epithlium
between the aleveoli ther are some collagen and elastic fibres
the alveolar membrane is the gas-exchange surface
30
What is the purpose of elastic fibres in alveoli?
it allows it to strech as they fill with air when breathing in
31
Why is diffusion of gases betwen the alveoli and the blood very fast (5)?
- red blood cells are slowed (flattened) as they pass through pulmonary capillaries (narrow) allowing more time for diffusion
- red blood cells are flattened against capillary walls decreasing diffusion distanc
- walls of alveoli and capillaries are thin for short diffusion pathway
- alveoli and pulmonary capillaries have a very large surface area
- breathing ventilates lungs and action of heart circulates blood flow through capillaries ensuring steep concentration gradient
32
Where does gas exchange occur in fish?
at the lamella in the gills
33
Why do fish have a specialised gas exchange system?
there is less oxygen in water than in air but need to maintain concentration gradient
and are relatively large so have a small surface area to volume ratio
34
Describe the sturcture of the gills
4 layers of gills on both sides of the head
gills made up of stacks of gill filaments
each gill filament is covered in gill lamellae at right angles to the filament
-> large SA
when fish open their mouth, water rushes in and over the gills and then out through a hole in the sides of their heads
35
What are the 3 adaptation fo efficient gas exchange in fish?
- large surface area to volume ratio
created by many gill filaments covered in many gill lamellae
- short diffusion distance
due to a capillary network in every lamellae and very thin gill lamellae
- maintaining concentration gradient
countercurrent flow mechanism
36
What is the countercurrent exchange principle?
when water flows over the gills in the opposite direction to the flow of blood in the capillaries
this ensures equilibrium is not reached
a diffusion gradient is maintainede across the ENTIRE length of the gill lamellae
37
How do insects prevent water loss (3)?
1 have an exoskeleton made of hard fibrous material
and a lipid layer to reduce evaporation
2 spiracles open and close using valves
3 spiracles have hairs around them to trap humid air and reduce the water potential gradient, reduicng evaporation
38
What does the tracheal system consist of ?
Tracheae
Tracheoles
Spiracles
39
What are spiracles?
valve-like openings along the length of the abdomen
open and close for oxygen and carbon dioxide enter and leave
attached to tracheae
40
What are tracheoles?
smaller tubes that extend throughout all the tissues in the insect to deliver oxygen to all respiring cells - short diffusion distance
41
What is the trachea in the tracheal system?
network of internal tubes
have rings within them to strengthen the tubes and to keep them open
42
What is the limitation of the tracheal system?
it telies mostly on diffusion which requires a short diffusion pathway
this limits the size insects caan attain
43
What are the 3 adaptations for efficient diffusion in insects?
- tracheoles have thin walls so short diffusion distance to cells
- tracheoles are highly branched so short diffusion distance AND large surface area
44
What are the 3 ways gases move in and out of the tracheal system?
1. along a diffusion gradient
2. mass transport
3. ends of the tracheoles are filled with water
45
How do gases move in the tracheal system when an insect is at rest?
diffusion
cells respire and use up oxygen and produce carbon dioxide creating a steep concentration gradient both directions
46
When does mass transport occur in insects and how?
during high activity like flight
contract and relax abdominal muscles squeezing the trachea
to move air helping to maintain diffusion gradient by speeding up exchange
47
How do gases move when an insect is very active and respires anaerobically?
lactate is produces
which lowers the water potential of muscle cells
water at end of tracheoles moves into cells by osmosis
this reduces volume of fluid in tracheols so gases diffuse more quickly through air rather than liquid
48
How are the diffusion gradients in a leaf maintained?
by mitochondria carrying out rspiration and chloroplasts carrying out photosynthesis
49
Describe the process of gas exchange in leafs
the palisade mesophyll produces oxygen and usees carbon dioxide as it is the site of photosynthesis
this creates a concentration gradient
oxygen travels through air spaces in the spongy mesophyll and diffues out of the stomata created by guard cells
carbon dioxide diffuses in through stomata
50
Why do stomata close at night?
photosynthesis is not occurring
this reduces water loss by evaporation
51
Leaves do not have a specific transport system for gases.
How are they adapted for rapid diffusion (3)?
- many stomata so no cells is far from a stoma - short diffusion pathway
- air spaces in mesophyll so gases can come in contact with cells
- large surface area of mesophyll cells for rapid diffusion
52
What are xerophytic plants?
plants that are adapted to survive in environments with limited water
53
What are the structural adaptations of xerophytes (5)?
- curled leaves to trap moisture to increase local humidity - no water potential gradient = no water loss
- hairs to trap moisture to increase local humidity = reduces water potential gradient
-sunken stomata to trap moisture
-thick waxy cuticle to reduce evaporation
-reduced surface area to volume ratio of leaves - small circular cross-sectioned leaves
54
Why can't plants have a small SA:VOL like insects to reduce water loss?
they photosynthesis which requires a large surface area to capture ligh
and to exchange gases
55
What is digestion?
the process in which large biological molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes
56
What are the 7 main parts of the digestive system?
- oesophagus
- stomach
- ileum
- large intestine
- rectum
- salivary glands
- pancreas
57
Digestion take place in 2 stages. What are they?
1. physical breakdown
2. chemical breakdown
58
What does the large intestine do?
absorb water
59
What does the rectum do?
stores faeces before being removed via the anus during egestion
60
What is the physical breakdown stage of digestion?
breaking down large food using teeth
this makes food easier to ingest and provides a large surface area for chemical digestion
food is churned in the stomach by wall muscles to break it up
61
Where is amylase produced and what does it break down?
By the pancreas and salivary glands
it hydrolyses starch into the disaccharide maltose
by breaking its glycosidic bonds
62
What enzymes are required to hydrolyse carbohydrates?
Amylases
and
membrane-bound disaccharidases
63
Describe how starch is digestion into alpha-glucose
- saliva from salivary gland mixed with food when chewing which contains amylase that hydrolyses starch into maltose by breaking glycosidic bonds
- saliva also contains mineral salts to maintain pH at neutral, optimum for amylase
- food enters stomach where acid dentatures amylase prevents further hydrolysis
- pancreatic jucice contains amylase which hydrolyses starch into maltose
alkaline salts produced by pancrease to maintatin optimum pH at neutral
- muscles in intestine wall push food along ileum
epithelial lining produces maltase in membrane to hydrolyse malto into alpha-glucose
64
Name the 3 membrane-bound disaccharidasesand what they hydrolyse
Maltase - maltose into alpha-glucose
Sucrase - sucrose into glucose and fructose
Lactase - lactose into glucose and galactose
(hydrolysed with the addition of water)
65
Name the 3 types of digestive enzymes
Carbohydrases - carbohydrates into monosaccharides
Lipases - lipids into glycerol and fatty acids
Proteases - propteins into amino acids
66
How are proteins digested?
1. endopeptidases - hydrolyse peptide bonds between amino acids in middle of polymer chain
2. exopeptidases - hydrolyse peptide bonds on terminal amino acids releasing dipeptides and single amino acids
3. dipeptidases - hydrolyse the bond between 2 amino acids of a dipeptide
67
How are lipids digested?
by lipase and the action of bile salts
lipase hydrolyses the ester bonds in triglycerids to from monoglycerides and fatty acids
bile salts emulsify lipids to form tiny droplets called micelles to increase surface area for lipase
68
Where is lipase produced ?
produced in the pancreas
69
Where are bile salts produced?
in the liver
70
Describe the structure of the ileum
wall covered in villi
have thin walls
surrounded by a network of capillaries and epithelial calls have even smaller microvilli
71
How do villi increase the efficiency of absorption?
- increase surface area
- very thin
- contain muscle so can mix contents of the ileum, maintaining diffusion gradient
- well supplied with blood vessels to maintain diffusion gradient
- epithelial cells lining villi possess microvilli which further increases surface area
72
What is the advantage of having many mitochondria in epithelial cells for absorption?
provide ATP which is hydrolysed to release energy needed for
co-transport and active transport
73
What is the advantage of having many ribosomes in epithelial cells for absorption?
produce many membrane proteins, including carrier and channel proteins for transport
74
What is the advantage of having many carrier and channel proteins in the ileum membrane?
allows for active transport and facilitated diffusion from ileum into epithelial cells then into blood
75
What are micelles?
water-soluble vesicles formed from:
- fatty acids
- glycerol
- monoglycerides
- bile salts
76
What do bile salts do?
make fatty acids and micelles water soluble
77
How do micelles help with lipid absorption (2)?
1. help make fatty acids more soluble in water allowing them to remain suspended in watery contents of the small intestine
2. carry and release fatty acids to the epithelial linging of ileum bringing them close to the surface of the cells
this maintains high conentration gradietn of fatty acids
78
What process do fatty acids use for absorption?
simple diffusion
79
Once inside epithelial cells, how are lipids absorped (5)?
- they are reformed into triglycerides in the endoplasmic reticulum and golgi body
- they associate with cholesterol and lipoproteins to form chylomicrons
- chylomicrons move out of the epithelial cell by exocytosis
- they enter lymphatic capillaries called lacteals and pass into the blood stream
- triglycerides in chylomicrons are hydrolysed by an enzyme in endothelial cells of blood capillaries from where they diffuse into cells
80
Why is active tranport and co-transport required for absorption of monosaccharides and amino acids?
there must be a higher concentration of glucose and amino acids in the lumen than the epithelial cells
but usually ther eis more in the epithelial ceells
81
Describe the co-transport of glucose and amino acids process
1. sodium ions are actively transported out the epithelial cell into the blood capillaries using ATP
2. this reduces the sodium ion concentration in the epithelial cell
3. sodium ions then diffuse from the lumen down their concentraiotn gradient into the epithelial cell
4. sodium ion diffuse through a co-transporter protein so glucose/amino acis also attach and are co-tranported into the epithelial cells against their concentration gradient with sodium ions
5. glucose/amino acids then move by facilitated diffusion from th epithelial cell to the blood
82
Why is one-way flow an advantage to fish?
less energy is required because the flow does not have to be reversed
important as water is dense and difficult to move
83
State 2 similarities between gas exchange in a plant leaf and gas exchange ein a terrestrial insect
- diffuse air through pores in outer covering
- no living cell is far from extrnal air
- need to avoid excessive water loss
84
State 2 differences between gas exchange in a plant leaf and gas exchange ein a terrestrial insect
- insects may create mass air flow - plants never do
- insects do not interchange gases between respiration and photosynthesis - plants do
- insects have a smaller surface area to volume ration than plants
85
State one modification to reduve water loss that is shared by plants and insects
waterproof covereing
ability to close openings
86
Insects and plants face the same problems when it comes to livin gon land. What is the main problem they share?
-efficient gas exchange requirees thin, permeable, with large area
- on land = water loss by evaporation
87
State 2 reasons why humans need to absorb large volumes of oxygen from the lungs
- humans are large
- humans have a high metabolic rate
- high body temp
- large vol of cells
88
List in the correct sequence all th structures that air passes through on its journey from the gas-exchange surface of the lungs to the nose
alveoli
bronchioles
bronchus
trachea
nose
89
Why are goblet and ciliated epithelial cells important in the lining of the trachea and bronchus?
dirt could damage/infect the alveoli
90
List 4 risk factors associated with lung disease
- smoking
- air pollution
- infections
- occupation
- genetics
91
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