3.3 Organisms exchange substances with their environment Flashcards
(188 cards)
1
Q
what are the three exchange processes?
A
diffusion: the net movement of substances through a partially permeable membrane down the concentration gradient (Passive)
Osmosis: the net movement of water molecules through a partially permeable membrane from a higher water potential to a lower water potential (Passive)
Active Transport: the movement of molecules and ions across a partially permeable membrane against concentration gradient using ATP and carrier proteins (Active)
2
Q
for exchange surfaces to be effective the exchange surface of the organism needs to be _______ than the volume
(complete the sentence)
A
for exchange surfaces to be effective the exchange surface of the organism needs to be larger than the volume
3
Q
what do organisms need to be able to obtain enough substances?
A
- a flattened shape so that every cell is not far from the surface (leaf)
- specialised exchange surfaces with large areas to increase the surface area to volume ratio (e.g alveoli in mammals, gills in fish, villi and microvilli of the digestive system)
4
Q
what are the main features of a specialised exchange surface?
A
- ) A large surface area compared to volume ratio to increase rate of exchange
- ) very thin so diffusion pathway is short
- ) selectively permeable to allow substances to cross
- ) movement of environmental medium e.g air, to maintain a diffusion gradient
- ) a transport system to ensure movement of the internal medium to maintain the diffusion gradient
5
Q
what are the roles of mass transport in plants and animals?
A
in animals: mass transport such as the circulatory system is used to carry blood with glucose and oxygen to the cells as well as substances such as waste, urea CO2 and hormones
in plants: mass transport transports water and solutes in xylem and phloem
6
Q
how can you express the relationship between the features of a specialised exchange surface
A
diffusion ∝ surface area x difference in concentration / length of diffusion path
7
Q
if you increase the surface area you ______ diffusion rate
(complete the sentence)
A
if you increase the surface area you increase the rate of diffusion
8
Q
if you increase the difference in concentration gradient you _______ the rate of diffusion
A
if you increase the difference in concentration gradient you increase the rate of diffusion
9
Q
if you increase the length of diffusion pathway you ________ the rate of diffusion
(complete sentence)
A
if your increase the length of diffusion pathway you decrease the rate of diffusion
10
Q
why are exchange surfaces foudn within the organism?
A
- to reduce dehydration
- reduce the chance of damage
11
Q
which process produces heat in your body?
A
respiration
12
Q
what is the internal body temperature?
A
37 degrees celcius
13
Q
why doesn’t the temperature does not exceed safe levels (37 degrees celcius)?
A
- because if the temperature is too high then the enzymes cant funcion because they may be denatured so less of you metabolic reaction may take place
- this is because when the temperature is high the bonds in the active site are disrupted from the ezymes vibrating too much
- therefore the active site chages shape and the substrate cn not bind to the active site and catalyse reactions
14
Q
what are the factors that ensure organisms stay at the correct temperature?
A
- body size: a small surface area makes it difficult to lose heat e.g a hippo, a large surface area leads to increased heat loss. a mouse needs a high metabolic rate to keep warm
- body shape: animals with compact shape has a small surface area to volume area- minimising heat loss. animals with less compact shape have a large surfacr area to volume ratio so lose heat quicker from their surface
15
Q
what are some exchange adaptations if body shape or size isn’t an option?
A
- water loss through surface
- adapted kidney structure so less urine is made and less water is lost
- a high metabolic rate in a cold environment
- consuming food with high energy content (seeds and nuts)
- smaller mamals have larger thicker fur or hibernate
- large animals in hot place e.g elephants have larger ears with increased surface area and hippos spend the day in water to help them lose heat
16
Q
give two reasons why diffusion is too slow in multicellular organisms for them to absorb and excrete substances this way
A
- a multicellular organism is too thick for substances to go in and out by diffusion to get to all cells
- surface area is too small to absorb enough subtance
17
Q
in winter some birds fluff their feathers to trap more warm air close to their body. would you expect this physiological adaptation to be more common amonf small or large birds? explain your answer
A
larger birds.
larger birds are more sucesptible to heat loss because of their smaller volume to surface area ratio
18
Q
what are the three main factors of a gas exchange surface?
A
- ) large surface area
- ) thin (usually one epithelial layer) short diffusion pathway
- ) maintenance of a steep concentration gradient across the exchange surface
19
Q
describe gas exchange in insects
A
- insects have microscopic air-filled pipes called trachea which they use for gas exchange
- air moves into the tracheae through pores on the surface called spiracles
- oxygen travels down the concentration gradient towards the cells
- the trachea branch off into smaller tracheoles which have thin, permeable walls and go to individual cells. this means that oxygen diffuses directly into the respiring cells (the insect’s circulatory system doesnt transport O2)
- carbon dioxide from the cells moves down it own concentration gradient towards the spiracles to be released into the atomosphere
- insects use rythmic abdominal movements to move air in and out of the spiracles
20
Q
exchanging gases causes water loss.
how is water loss reduced in insects?
A
- insects use muscles to close spiracles if they are losing too much water
- they have a waterproof waxy cuticle all over their body and tiny hairs around their spiracles, both of which reduce evaporation
21
Q
discuss the strucure of the gill and how this helps with the counter-current system
A
oxygen hasa lower concentration in water than in air
- oxygen containing water enters through the mouth and exits through the gills
- each gill contains ‘thin plates’ or ‘gill filaments’
- gill filaments are covered in lots of tiny structures called lamaellae, which increase the surface area even more
- the lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
counter current system:
- this is where water flows over the gill lamellae in the opposite direction to the fish blood flow
- this helps to maintaine a favourable concentration gradient across the whole length of the gill lamellae (entire exchange surface)
- the concentration of oxygen of water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood
22
Q
describe the counter current system
A
counter current system:
- this is where water flows over the fill lamella in the opposite direction to the fish blood flow
- this helps to maintaina diffusion gradient across the whole length of the gill lamellae
- the concentration of oxygen of water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood
23
Q
describe ventilation and circulation in a fish
A
- the constant movement of water through the mouth and over the gills (ventilation) helps to replace water low in O2 with water higher in O2
- at the cells; circulation of blood helps to replace blood that is low in O2 with blood saturated with O2
24
Q
the volume of water assing over the gilss increases if the temperature of the water increases. suggest why.
A
at higher temperatures the ezymes work faster
- so there is a higher rate of metabolic reactions such as respiration
- these reactions require more oxygen from the water so more water is needed to be transferred replace water low in oxygen
25
a fish uses gills to absorb oxygen from water, explain how the gills of a fish are adapted for efficient gas exchange
- gill filaments and lamallae speed up diffusion by providing large surface area
- the lamallae have lots of capillaries and thin surface area of cells which provide a short diffusion pathway
- a concentration gradient is maintained across the whole length of the gill as water flows over the gill lamellae in the direction opposite to the flow of the fish blood. this is the counter current system.
26
label the parts of this leaf
A= palisade mesophyll cell
B= xylem and phloem
C= spongy mesophyll cells
D= waxy cuticle
E= lower epidermis cells
F= guard cell
G= stoma
H= upper epidermis cell
I= waxy cuticle
27
in what ways is gas exchange in plants is similar to thay of insects?
- no living cell is far from the external air, and therefore a source of oxgen and carbon dioxide
- diffusion takes place in the gas phase (air), which makes it more rapid then if it were in water
28
what are the adaptations plants have for rapid diffusion?
- many small pores, called stomata and so no cell is far from a stoma and therefore the diffusion pathway is short
- many interconnecting air-spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells
- large surface are of mesophyll cells for rapid diffusion
29
why do plants not have a large surface area to volume ratio?
because they photosynthesise, and photosynthesis requires a large leaf surface area for the capture of light and for the exchange of gases
30
what are xerophytes plants?
plants that are adapted to living in areas where water is in short supply
31
what are adaptations xerophyte plants have to reduce water loss?
- a thick waxy cuticle: waxy cuticle forms a waterproof barrier, it reduces evaporation, the thicker the cuticle the less water can escape.
- curles/rolling up of leaves: the rolling of leaves protects the lower epidermis from the outside and helps to trap a region of still air within the rolled leaf. This region becomes saturated with water vapour and so has a very high water potential, there is no water potential gradient betweent he inside and outside of the leaf and therefore no water loss. also protects from wind
- sunken stomata surrounded by hairs: traps still mosit air next to the leaf and reduce the water potential gradient
- reduced stomata: few pores for water to escape
32
Insects and plants face the same problems when it comes to living on land. what is the main problem they share?
efficient gas change requires a thin, permeable surface with large area.
On land these features can lead to consdierable loss of water by evaporation
33
plants such as marram grass roll up their leaves, with the lower epidermis on the inside, to reduce water loss
why would rolling the lead the other way (with the upper epidermis on the inside) not be effective in reducing water loss?
- almost all stomata are on the lower epidermis
- this would be exposed to air currents that would reduce the water potential outside the leaf
- the water potential gradient would be increased and a lot of water vapout would be lost
34
\*label this diagram showing the gas exchange system and describe the function of these organs in the system\*
\*diagram in cgp books\*
1. ) as you breathe in, air enters the trachea (windpipe)
2. ) the trachea splits into two bronchi- one brochus lead to each lung
3. ) Each bronchus then branches off into smaller tubes called bronchioles
4. ) the bronchioles ened in small 'air sacs' called alveoli (this is where gas is exchanged)
5. ) the ribcage, intercostal muscles and diaphragm all work together to move air in and out
35
what are the lungs?
they are a pair of lobed structures made up of a series of highly branched tubes, called bronchioles, which end in tiny air sacs called alveoli
36
what is the trachea and what does it do?
a flexible airway that is supported by rings of cartilage
the cartialge prevents the trachea from collapsing as the air pressure inside falls when breathing in.
the trachea walls are made up of muscles, lined with cilliated epithelium and goblet cells
37
what are the bronchioles and what do they do?
they are a series of branching subdivisions of the bronchi
their walls are made of muscle lined with epithelial cells
this muscle allows them to constrict so that they can control the flow of air in and out of the alveoli
38
what are the bronchi and what do they do?
the bronchi are two divisions of the trache each leading to the lung
like the trachea they produce mucus to trap dirt and have cillia that move dirt-laden mucus towards the throat
the larger bronchi are supported by cartilage
39
what are alveoli and what do they do?
they are minute air-sacs, with a diamete of between 100-300 nanometers at the end of the bronchioles
- between the alveoli there are some collagen and elastic fibres which allow the alveoli to stretch as they fill with air when breakthing air and then spring back to expel CO2 rich air
- the alveoli are lined with epithelium (thin tissue)
- the alveolar membrane is the gas-exchange surface
40
state two reasons why humans need to absorb large volumes of oxygen from the lungs
humans are large so have a large volume of cells
humans aloso have a high metabolic rate
41
explain how the cells lining the trachea and bronchus protect the alveoli from damage
the dirt/bacteria could damage and cause infection in the alveoli
so the cells produce mucus that traps particles of dirt and bacteria in the air breathed in
the cillia on these cells move this debris up the trachea and into the stomach
42
what is ventilation?
where air is constantly moved in and out of the lungs to maintain diffusion of gases across the alveolar epithelium
43
what is inspiration (inhalation)?
the air pressure of the atomosphere is greater than the air pressure inside the lungs so air is forced into the lungs
44
what is expiration?
when the air pressure in the lungs is greater than that of the atomosphere so air is forced out of the lungs
45
what are three set of muscles that move to change pressure within the lungs?
the diaphragm: sheet of muscle that seperates the thorax from the abdomen
the intercostal muscles: which lie between the ribs
- internal intercostal muscles whose contaction leads to expiration
- external intercostal muscles whose contractions lead to inspiration
46
what does the diaphragm during inspiration?
the diaphragm contracts, pulls down which causes it to flatten
this enlarges the thoraic cavity increasin the volume of the thorax
47
what does the diaphragm do in expiration?
the diaphragm relaxes and so it is pushed up again by the contents of the adbomen, returning to its dome shape
the volume of the thorax is further decreased
48
what do the external intercostal muscles do during inspiration?
during inspiration the external intercostal muscles contract and lift the ribs up and outwards
49
what do the internal intercostal muscles do during expiration?
during expiration the internal intercostal muscles contract and pull the ribs downwards and inwards
50
what are antagonistic muscles
these are muscle pairs that work opposite to each other
51
why is gas exchange vital?
- provide oxygen for repiration
- it allows waste CO2 to be expelled
- CO2 lowers the pH of cells and blood plasma (normally pH 7-4) which could cause problems such as denaturing
52
what happens during inhalation?
breathing in is an active process (it uses energy) and occurs as follows:
- the external intercostal and diaphragm muscles contract whilst the internal intercostal muscles relax
- this causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thoracic cavity (the space where the lungs are)
- as the volume of the thoracic cavity increases, the lung pressure decreases (to below atomosphere pressure)
- amospheric pressure is now greater than pulmonary pressure so air moves down the concentration gradient. It flows down the trachea and into the lungs
53
what happends during expiration?
breathing in is an passive process (it doesnt require much energy) and occurs as follows:
- the internal intercostal and contract whilst the external intercostal muscles and diaphragm relax
- this causes the ribcage to move downwards and inwards and the diaphragm to become curved, reducing the volume of the thoracic cavity (the space where the lungs are)
- as the volume of the thoracic cavity decreases, the lung pressure increases (to above atomosphere pressure)
- amospheric pressure is now less than pulmonary pressure so air moves down the concentration gradient and is forced out of the lungs
54
what happesn during forced expiration?
the external intercostal muscles relax and internal intercostal muscles contract, pulling the ribcage down and in
-during this time, the movemnt of the two sets of the intercostal muscles is said to be antagonisitic (opposing)
55
where is the site of gas exchange in mammals?
in the epithelium of the alveoli (surface membrane of the alveoli)
56
whar are the 3 things that the alveoli epithelium needs to have for efficient diffusion?
1. ) large surface area compared to its volume
2. ) A short diffusion distance for the gas to diffuse
3,) a large difference in the concentration of gas on the opposite side of the surface
57
what are the adapations of the alveoli for effficient gas exchange?
- a thin surface: the alveolar epithelium are only one cell thick which means theres a short diffusion pathway
- a large surface are: the large number of alveoli means theres a large surface area for gas exchange
- inner surface of the alveoli is covered in a thin film of water: the water is essential to allow oxygen to dissolce in it and pass into the blood
58
how does O2 get into the blood from the alveoli?
- the alveoli are surrounded by a network of capillaries
- O2 diffuses out of the alveoli, accross the aveoli epithelium and the capillary endothelium (a type of epithelium that forms the capillary wall) and into haemoglobin in the blood
- CO2 diffuses into the alveoli from the blood is breathed out
59
summary of gas exchange
oxygen from the air moves down the trachea, bronchi and bronhioles into the allveoli (this movement happends down the pressure gradient)
Once in the alveoli the oxygen diffuses across the alveolar epithelium, the capillary endothelium ending up in thecapillary itself. (this movement happens down a diffusion gradient)
60
how is a concentration maintained
it maintained by ventilation and bood circulation
- ventilation ensure the alveoli have a high conc of O2
- blood circulation removes red blood cells with a high conc O2 and replaces them with red blood cells with a low O2 conc
61
how do infections such as pneumonia affect gas exchange?
they cause the layer of water on the alveoli wall to get thicker so diffusion of O2 is slower and decreased, serisouly hindering gas exchange
62
a mountain climber is climbing at altitude, where theres less oxygen
suggest how this will affect gas exchange in the alveoli
-gradient of oxygen between the capillaries will be less steep slowing the rate of diffusion
63
what lung disease affect?
ventilation
gas exchange
64
what is the tidal volume?
what is the healthy range?
volume of air in each breath at rest
healthy range: 0.4dm3 - 0.5dm3
65
what is meant by the ventilation rate?
what is the healthy range?
number of breaths per minute
15 breaths per minute
66
what is meant by the forced expiration volume (FEV)?
max volume of air breathed out in 1 second
67
what is meant by the forced tidal capacity (FTC)
the max volume of air that's forcefully breathed out after a really deep breath in
68
what is the pulmonary ventilation and what is the eqaution for working it out?
state the units
this is the total volume of air moved in and out of the lungs in one minute
pulmonary ventilation = tidal volume x ventilation rate
pulmary ventilation= (dm3 min-1)
tidal volume= dm3
Ventilation rate= min-1
69
what is a spirometer?
a machine that scientist and doctors use to measure the volume of air breatherd in and out
70
Name the parts of this graph
A= deep breath in
B= tidal volume of normal breath
C=deep breath out
D=residual air can't be expelled
71
discuss how emphysema is caused, the symptoms and how it affects lung function
emphysema
causes: smoking, long term exposure to air pollution - where the foreign particles in the smoke (or air) become trapped in alveoli
symptoms: shortness of breath, wheezing, increased ventilation rate to try and increase the amount of air in the lungs
how it affects lung function:
- the trapped particles in the alveoli cause inflammation, which attracts phagocytes,
- the phagocytes produce an enzyme that breaks elastin (protein in the walls of the alveoli)
- elastin is elasti, helps the allveoli to return their normal shape after inhaling and exhaling air
- loss of elastin means the alveoli cant recoil to expel air as well and can lead to the destruction of the alveoli walls which reduce surface area so rate of gaseous exchange decreases
72
discuss how asthma is caused, the symptoms and how it affects lung function
Cause: asthma is a respiratory condition where the airways become inflame and irritated, caused by allergic reactions to substances such as pollen and dust
symptoms: wheezing, tight chest, shortness of breath
how it affects lung function:
- during an asthma attack, the smooth muscle lining the bronchioles contracts and a large amount of mucus is produced
- this constritcs the airways making it difficult to breathe
- air flow in and out of the lungs is severly reduced, so less oxygen enters the alveoli and moves into the blood. reduced airflow means that FEV1 is severely reduced
73
discuss how pulmonary tuberculosis (TB) is caused, the symptoms and how it affects lung function
causes: infection from tuberculosis bacteria, exposure to substances like dust, asbestos
symptoms: persistent cough, coughing blood and mucus, chest pains, shortness of breath fatigue
how it affects lung function:
when someone becomes infected with tuberculosis bacteria, the immune system build a wall around the bacteria in the lungs which forms small, hard lumps known as tubercles
- infected tissure with the tubercles dies and the gaseous exchange surface is damaged so tidal volume is decreases
- a reduced tidal volume means less air can be inhaled with each breath, in order to take in enough oxygen patients have to breathe faster i.e ventilation rate is increased
74
discuss how fibrosis is caused, the symptoms and how it affects lung function
fibrosis is the formation of scar tissue in the lungs
cause: infection, exposure to substances like asbestos or dust
symptoms: dey cough, chest pain, fatigue, weakness, shortness of breath (faster ventilation rate than normal to get enough air into lungs to oxygenate their blood)
how it affects lung function:
- scar tissue (tissue formed when the tissue before was damaged) is thicker and less elastic than normal lung tissue
- this means that the lungs are less able to expan and so cant hold as much air as normal so tidal volume is reduced and so is FVC
- there is a reduction in the rate of gaseous exchange- diffusion is slower across a thicker scarred membrane
75
answer this question
76
whar are the risk factors for lung disease?
- smooking
- air pollution
- genetic make up
- infections
- occupation (working with harmful chemicals
77
to prove that something is a cause of a factor e.g premature death is caused by smoking, what procedures are used?
1. ) establish a hypothesis to try to explain the correlation, this should be based on current knowledge
2. ) design and perform experimets to test the hypothesis
3. ) establish the causal link and formulae theories to explain it
78
what is a risk?
the measure of the probablilty that damage to health will occur as a result of a given hazard
79
what are risk factors?
factors that increase the chance of something happening
80
what is meant by correlation?
when a change in one of two variables is reflected by a change in the other variable
81
what are inavoidable factors?
- age
- gender
- the genes you inherit
82
interpreting lung disease data
83
interpreting lung disease graphs
84
answer theses questions on lung disease data
85
describe how ventilation helps to maintain this difference in oxygen concentration
- ventilation ensures that the alveoli have a high concentration of O2 from when air is breathed in
- lower concentration of O2 in air when breathed out
86
label the parts of the digestive system
A= tongue
B= salivary glands
C= oesophagus
E= lobe of liver
F= transverse limb of large intestine
G= ascending limb of large intesting (colon)
H= stomach
I= pancreas
J= descending limb of the large intestine (colon)
K= small intestine (ileum)
L= rectum
M= anus
87
what does the oesophagus do?
carries food from the mouth to the stomach
88
what is the stomach and what does it do?
it is muscular sac with an inner layer that produces enzymes
its role is to store and digest food, especially proteins
it has glands that produce enzymes which digest protein
89
what is the ileum (small intestine) what does it do?
what are its adaptations?
- the ileum is a long muscular tube
- food is further digested in the ileum by enzymes that are produced by its walls and by glands that pour their secretions into it
- the inner walls of the ileum are folded into villi, which gives them a large surface area, the surface area of these villi is further increased by millions of tiny projections called microvilli, on the epithelial cells of each villus
- this adapts the ileum for its purpose of absorbing the products of digestion into the bloodstream
90
what does the large intestine do?
the large intestine absorbs water
-most of the water that is absorbed is water from secretions of the many digestive glands
91
what does the rectum do?
stores faeces and then removes them via the anus in a process called egestion
92
what do the silvary glands do?
they pass secretions via a duct in the mouth
these secretions contain the enzyme amylase, which hydrolyse starch into maltose
93
what is the pancreas and what does it do?
the pancreas is a large gland situated below the stomach
it produces secretions called pancreatic juice
this secretion contains proteases to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse starch
94
what are the two stages of digestion?
1. physical break down: large pieces of food are broken down into smaller pieces using teeth, which makes it possible to ingest food and provide a large surface area for chemical digestion
2. chemical digestion: hydrolyses large, insoluble molecules into smaller soluble ones using enzymes
95
what are the main three types of digestive enzymes?
- carbohydrases; carbohydrates to monosaccharides
- lipases: lipids to fatty acids and glycerol
- proteases: proteins to amino acids
96
why do we need digest?
-food compounds so such as starch, protein and lipids are large insoluble molecules that can not be absorbed directly into the blood
to be absorbed they must be digested through hydrolysis reaction
-diestion is catalysed by enzymes secreated into the lumen of the digestive system
97
why do we need to digest?
- food compounds such as starch, proteins and lipids are large insoluble molecules that can not be absorbed directly into the blood
- to be absorbed they must be digested through a hydrolysis reaction
- digestion is catalysed by enzymes secreted in the lumen of the digestive system
98
in the break down of starch: what enzyme is involved and where is it produced? which bond is broken? and what is the product created?
enzyme used: amylase which is produced by the salivary glands and pancreas
bond broken: glycosidic bond
product produced: maltose
99
in the break down of sucrose: what enzyme is involved and where is it produced? which bond is broken? and what is the product created?
enzyme used: sucrase produced in the ileum
bond broken: glycosidic bond
product: glucose and fructose
100
in the break down of maltose: what enzyme is involved and where is it produced? which bond is broken? and what is the product created?
enzyme used: maltase which is produced in the ileum
bond broken: glycosidic bond
product: glucose and glucose
101
in the break down of lactose: what enzyme is involved and where is it produced? which bond is broken? and what is the product created?
enzyme used: lactase which is produced in the ileum
bond broken: glycosidic bond
products: galactose and glucose
102
in the break down of lipids: what enzyme is involved and where is it produced? which bond is broken? and what is the product created?
enzyme used: lipase produced in the pancreas
bond broken: ester bond
products: fatty acids and glycerol
103
in the break down of protein (hydrolysis within a protein): what enzyme is involved and where is it produced? which bond is broken? and what is the product created?
enzyme used: endopeptides which hydrolyse the peptide bonds between amino acids in the central region of a protein molecule e.g trypsin and chymotypsin synthesised in the pancreas or secreted into the small intestine/ e.g pepsin released into the stomach by cells in the stomach lining, it only works in acidic condition
bonds broken: peptide bond
products: polypeptide fragments
104
in the break down of proteins (hydrolysis at end of protein): what enzyme is involved and where is it produced? which bond is broken? and what is the product created?
enzyme used: exopeptideases which hydrolyse peptide bonds at the ends of protein molecules. they remove single amino acids from proteins and synthesised in the pancreas
bond broken: peptide bonds
products: amino acids and polypeptides
105
in the break down of dipeptides: what enzyme is involved and where is it produced? which bond is broken? and what is the product created?
enzyme used: dipeptidases from the cell-surface membrane of epithelial cells in the small intestine
bond broken: dipeptide bond
products: amino acid x2
106
what are the products of digestion (monosaccharides, monoglycerides and fatty acids, amino acids) used for after they are absorbed across the ileum epithelium into the bloodstream?
Monosaccharides:
- glucose is absorbed by active transport with sodium ions via a co-transporter protein
- galactose is absorbed in the same way using the same co-transporter protein
- fructose is absorbed via facilitated diffusion through a different transporter protein
Monoglycerides and fatty acids:
micells help to move monoglycerides and fatty acids towards the epithelium because micelles constantly break up and reform they can 'release' monoglycerides and fatty acids, allowing them to be absorbed- whole micells are not taken up across the epithelium.
-monoglycerides and fatty acids are lipid solube, so can diffuse directly across the epithelial cell membrane
Amino acids:
- amino acids are absorbes in a similar way to glucose and galactose
- sodium ions are actively transported out of the epithelial cells into the ileum itself
- they then diffuse back into the ells through sodium-dependant transporter proteins in the epithelial cell membranes, carrying the amino acids with them
107
describe the role of bile in digestion
- bile salts are produced by the live and they emulsify lipids to form smaller droplets of lipids
- the smaller droplets have a larger surface area for enzyme action than one large droplet (of the same volume)
- when the lipids have been broken down the fatty acids and monoglycerides stick with the bile salts to make micelles that allow absorption of these products
108
what is heamoglobin made up off?
haemoglobin is a large protein with a quatenary structure
it has 4 polypeptide chains
each polypeptide contains a heam group with an Fe2+ ion (which gives it its red colour)
each iron ion can combine with a single O2 molecule
so one heamoglobin molecule can carry 4 O2 molecules
this is why it said that haemoglobin has a high affinity for oxygen
109
what is the reversible eqaution for the loading and unloading of haemoglobin?
110
what is the partial pressure of oxygen?
pO2
this is the measure of oxygen concentration
111
which words are used for the process by which haemoglobin binds with oxygen
loading/ association
112
which words are used for the process by which haemoglobin releases its oxygen
unloading/ dissociation
113
the greater the oxygen concentration the _______ the partial pressure
the greater the oxygen concentration the greater the partial pressure
114
what happens to the O2 around haemoglobin at a high pO2?
O2 loads onto haemoglobin at a high pO2
115
what happens to the O2 bound to haemoglobin (oxyhaemoglobin) at a low pO2
the oxyhaemoglobin unloads at a low pO2
116
what is meant by 'an affinity for O2'
the tendancy for a molecule to bind with O2
117
at a gas exchange surface is the O2 concentration, CO2 concentration and affinity of haemoglobin for oxygen high or low?
what does this result in, in terms of loading and unloading of O2?
oxygen concentration: high
Carbon dioxide concentration: low
affinty of haemoglobin for oxygen: high
results: loads onto haemoglobin
118
at respiring tissue cells is the O2 concentration, CO2 concentration and affinity of haemoglobin for oxygen high or low?
what does this result in, in terms of loading and unloading of O2?
oxygen concentration: low
Carbon dioxide concentration: high
affinty of haemoglobin for oxygen: low
results: oxyhaemoglobin unloads
119
explain how dna leads to different haemoglobin molecules having different affinities for oxygen
- different base sequence in dna
- different amino acid sequence
- different tertiary and qauternary structure/shape
- different affinities for oxygen
120
describe the s (sigma) shape curve on this oxygen dissociation graph
talk about the point:
0%
low pO2
high pO2
- almost max saturation
- 100% saturation
- when the curve is steep
- there is 0% saturation as non of the haemoglobin molecules are carrying oxygen
- where pO2 is low haemoglobin has a low affinity for oxygen which means it releases oxygen rather than combining with it, thats why it has a low saturation of oxygen near the start
- where pO2 is high haemoglobin has a high affinity for O2 (it will readily combine with oxygen so it has a high saturation of oxygen)
this is because as the first O2 molecule binds to the haemoglobin, it alters the shape making it easier for other O2 to bind (the steep part in the middle)
- As haemoglobin becomes more saturated it gets harder for more O2 molecules to bind
- 100% saturation means every haemoglobin molecule is carrying 4 molecules of O2
- when the curve is steep, it shows that a small change in pO2 causes a big change in the amount of O2 carried by haemoglobin
121
at higher partial pressure of carbon dioxide (pCO2) haemoglobin gives up its oxygen _______ \_\_\_\_\_\_\_\_
at higher partial pressure of carbon dioxide (pCO2) haemoglobin gives up its oxygen more readily
122
explain the bohr effect
the bohr effects is the reduction in affinity of haemoglobin for O2 as CO2 increases
1. ) when cells respire they produce carbon dioxide which raises the pCO2
2. ) this increases the rate of oxygen unloading (the rate at which oxyhaemoglobin dissociates to form haemoglobin and oxygen)
so the dissociation cuve shifts to the right (as there is a higher pCO2)
3.) the saturation of blood with O2 is lower for a given pO2 meaning more oxygen is being released
CO2 also lowers the pH which changes the shape of haemoglobin (protein) so it gives up O2 more readily at a higher pCO2
123
organisms that live in a environments with with a low concentration oxygen have haemoglobin with a lower affinity for O2 than human haemoglobin.
On a dissocation graph, which position would you find the curve showing this relative to a human O2 dissociation curve
to the left of a human's dissociation curve
(shifted to the left oxygen is kept)
124
organisms that are very active and have high oxygen demand have haemoglobin with a higher affinity for O2 than human haemoglobin.
On a dissocation graph, which position would you find the curve showing this relative to a human O2 dissociation curve
it is positioned to the right of the human dissociation curve
(shifted to the right haemoglobin has a fright)
125
organisms that are very small have haemoglobin with a lower affinity for O2 than human haemoglobin.
On a dissocation graph, which position would you find the curve showing this relative to a human O2 dissociation curve
explain why
the curve would be positioned to the right of a human's dissociation curve
- this is because smaller mammasl usually have a larger surface area to volume ratio
- they lose heat quickly so need a high metabolic rate (greater demand of O2) to keep warm
- therefore haemoglobin has to be good at unloading oxygen quickly to meet the high demand from respiration
126
Heat from respiration helps mammals to maintain a constant body temperature. Use this information to explain the relationship between surface area to volume ration of mammals and the oxygen dissociation curves of their heamoglobin
1. ) smaller mammals have a larger surface area to volume ratio
2. ) so they will lose heat faster
3. ) therefore they will require more oxygen to maintain a high rate of respiration for heat
4. ) a right-shifted curve means haemoglobin will dissociate more readily at higher partial pressure of oxygen.
127
why do muticellular organism e.g mammals need a circulatory system?
mammals have a low surface area to volume ratio, so they need specialised transport system to carry raw materials from specialised exchange organs to their body cells
128
what is the circulatory system made up of?
the heart and its blood vessels
129
label the parts of this heart
A= left pulmonary artery
B= right pulmonary artery
C= pulmonary trunk
D= superior vena cava
E= right atrium
F= right AV valve
G= pulmonay semilunar valve
H= right ventricle
I= inferior vena cava
J= aortic arch
K= aorta
L= left pulmonary veins
M= right pulmonary veins
N= left atrium
O= left AV valve
P= aortic semilunar valve
Q= left ventricle
R= septum
S= descending aorta
130
what are the two types of chambers in the heart
ventricles:
- the left ventricle has thicker muscular wall to create high pressure to pump blood to the body
- the right is less muscular as at it only needs to be powerful enough to pump blood to the lungs
Atrium:
-have thinner elastic walls as they only pump blood a short distance to the ventricles
131
what do chords do?
attach atrioventricular valves to the ventricles to stop them being forced up into the atria when the ventricles contract
132
what do the atrioventricular valves do?
link the atria to ventricles and stop blood flowing back into the atria when the ventricles contract
133
what do the semilunar valves do?
link ventricles to the pulmonary artery and aorta and stop blood flowing back into the heart when the ventricles contract
134
when pressure is greater infront of the valves what do they do?
close
135
when pressure is greater behind the valves what do they do?
open
136
what are the four vessels connected to the chambers of the heart?
- aorta
- vena cava
- pulmonary artery
- pulmonary vein
137
what does the aorta do?
the aorta is connected to the left ventricle and carries oxygenated blood to all parts of the body except the lungs
138
what does the vena cava do?
the vena cava is connected to the right atriym and brings deoxygenated blood back from the tissues of the body (except the lungs)
139
what does the pulmanary artery do?
the pulmonary artery is connected to the right ventricle and carries deoxygenated blood to the lungs, where it is oxygen replenished and its carbon dioxide is removed
(unusually for an artery, it carries deoxygenated blood)
140
what does the pulmonary vein do?
the pulmonary vein is connected to the left atrium and brings oxygenated blood back from the lungs
(unusually for a vein, it carries oxygenated blood)
141
how is the heart muscle supplied with oxygen?
the heart muscle is supplied by its own blood vessels called the coronary arteries which brancg of the aorta shortly afyer it leaves the heart.
-blockage of these arteries, e.g blood clot, leads to myocardial infarction, or heart attack, because an area of the heart muscle is deprived of blood and therefore oxygen also. The muscle cells in this region are unable to respire (aeorbically) and so die.
142
why are there two pumps required for the blood circulation in mammals?
- pressure steadily drops as blood exists the heart from the aorta and returns in the vena cava
- the two pumps ensure the blood has enough pressure to reach cells and return
143
Arteries, arterioles and veins all have the same layered components from the outside inwards.
what are these layers?
LEEMF
1. Tough fibrous outer layer (which resists pressure)
2. smooth muscle layer (can contract and control the flow of blood)
3. Elastic layer (maintain the blood pressure by stretching and springing back "recoiling")
4. Thin inner lining "endothelium (smooth to reduce friction and thin to allow diffusion)
5. Lumen (not actually a layer but the central cavity of the blood vessel through which the blood flows)
144
what is the structure, function and adaptations of the artery?
Structure:
1. thicker muscle layer than veins
2. thicker elastic layer than veins
Function:
Transports blood at high pressure from hearts to tissues
Adaptation:
1. Constrict & dilate to control volume of blood
2. Stretches and recoils to maintain high pressure
145
what is the structure, function and adaptations of the arteriole
Structure:
1. muscle layer relatively thicker than arteries
2. elastic layer relatively thinner than arteries
Function:
carry and control blood flow at lower pressure between arteries and capillaries
Adaptation:
1. Contractions constricts lumen restricting blood flow into capillaries
2. blood at low pressure
146
what is the structure, function and adaptations of the capillary
Structure:
1. Narrow lumen
2. Single endothelial lining
3. spaces between lining
4. numerous and highly branched
Function:
site of diffusion of substances between blood and cells
Adaptation:
1. RBC's squeezed against wall so always close to cells
2. short diffusion pathway
3. Allows WBC's to escape
4. large surface area
147
what is the structure, function and adaptations of the vein
Structure:
1. muscle layer relatively thinner than arteries
2. elastic layer thin than arteries
3. thinner wall than arteries
4. valves
Function:
carries blood slowly at low pressure from tissues to heart
Adaptations:
1. No need to control blood flow to tissues
2. pressure to low to create recoil action
3. low pressure poses no bursting risk
4. ensure blood flows in one direction
148
what is tissue fluid?
fluid that surrounds the cells in tissues that contains glucose, amino acids, fatty acids, ions in solutions and oxygen
\*it does not contain red blood cells or big proteins
149
how is tissure fluid formed?
- blood pumped by the heart passes along the arteries, then the narrower arterioles, then finally the even narrower capillaries
- pumping by the heart creates a pressure aka "hydrostatic pressure" at the arterial end of the capillaries; this pressure is greater than the hydrostatic pressure in the tissue fluid
- the difference in hydrostatic pressure means an overall outward pressure forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid
150
how do substances move out of the capillaries into the tissure fluid?
this process is called pressure filtration:
- When a difference in hydrostatic pressure is created causing an overall outward pressure to force fluid out of the capillaries and into the spaces around the cells, it forms tissue fluid
- as the fluid leaves small molecules leave with it, the hydrostatic pressure reduces in the capillaries- so the hydrostatic pressure is much lower at the venule end of the capillary bed
- due to fluid loss, and an increasing concentration of plasma proteins, the water potential at the venule end of the capillary bed is lower than the water potential in the tissue fluid
- this means that some water re-enters the capillaries from the tisssure fluid at the venule end by osmosis
151
where does any excess tissue fluid go?
it is drained into the lymphatic system, which transports this excess fluid from the tissures and dumps it back into the circulatory system
152
what is meant by the cardiac cycle?
an ongoing sequence of contraction and relaxation of the atria and ventricles that keep blood flowing through the heart
153
describe the three stages of the cardiac cycle
Diastole (relax, more distance), Systole (contract, smaller)
1. Cardiac diastole:
- Atria and Ventricles relax
- Blood moves into atria from veins (pl and vc) at low pressure
- pressure in atria increases
- blood moves through atrioventricular valves to the ventricles
2. Atrial systole (Ventricular diastole):
- atria contract, ventricles relax
- atria contract to fully empty
- pressure in ventricles increases
- AV valve close to prevent back flow to atria
3. Ventricular systole (atrial diastole)
- ventricles contract, atria relax
- ventricles contract from apex upwards
- AV valves still shut
- pressure in ventricles is greater than in arteries
- semilunar valves open
- so blood moves into arteries (aorta and pl)
154
graph that represnts the cardiac cycle
155
what is meant by the cardia output? state the units
this is the volum of blood pumped by the heart per minute (cm3 min-1)
156
what is the eqaution used to calculate cardiac output
cardiac output = stroke volume x heart rate (bpm)
157
what is cardiovascular disease used to describe?
disease of the heart and blood vessels
158
most cardiovascular disease start with the formation of an atheroma that can lead to three things.
what are these?
1. An aneurysm
2. thrombosis
3. Mycordial Infarction
159
how is an atheroma formed?
- the wall of the artery is made up of many layers
- the endothelium is usually smooth and unbroken
- if damage occurs to the endothelium (e.g by high blood pressure) the white blood cells (mostly macrophages) and lipids from the blood, clump together under the lining to from fatty streaks
- over time, more white blood cells, lipids and connective tissue build up and hard to form fibrous plaque called an atheroma
-
160
how does coronary heart disease develop (CHD)
CHD is a type of cardiovasclular disease
- it occurs when the coronary arteries have lots of atheromas in them, wehich restricts the blood flow to the heart muscle.
- It can lead to myocardial infarction
161
what are the two types of disease that affect the arteries?
- Aneursym
- Thrombosis
162
how is an aneursym formed from atheromas?
1. ) Atheroma plaques damage and weaken arteries. They also narrow arteries increasing blood pressure.
2. ) when blood travel through a weakend artery at high pressure, it may push the inner layers of the artery through the outer elastic layer to form a balloon like swelling -an aneursym
3. ) blood fills it and it may burst casusing a heamorrhage
163
how is thrombosis formed from atheroma?
1. ) An atheroma plaque can rupture the endothelium of an artery
2. ) This damages the artery wall and leaves a rough surface
3. ) Platelets and fibrin (a protein) accumulate at the site of damage and form a blood clot (thrombus)
4. ) This blood clot can cause complete blockage of the artery, or it can become dislodged and block a blood vessel elsewhere in the body.
5. )Debris from the rupture can cause another blood clot to form futher down the artery.
164
How is myocardial infarction formed (heart attack)?
1. ) the heart is supplied with blood from the coronary arteries
2. ) This blood contains the oxygen needed by the heart muscle cells to carry out respiration
3. ) If a coronary artery becomes completely blocked (e.g by a blood clot) an area of heart muscle will be totally cut off from its blood supply, receiving no oxygen
This is know as myocardial infarction. A heart attack can cause damage and death of the heart muscle.
165
what are the symptoms of a heart attack?
- pain in the chest and upper body
- shortness of breath
- sweating
166
what is a risk factor?
something that increases your chance of getting a disease
167
what are the most common risk factors for cardiovascular disease? q
1. ) high blood cholesterol and poor diet:
- diet high in saturated fat
- high blood cholesterol (above 240mg per 100cm3 and risk is increased)
- atheroma formation
- blood clots
- mycordial infarction
- diet high in salt
- high blood pressure (which can then lead to the formation of atheromas)
2. ) Cigarette smoking
- build up of carbon monoxide so less oxygen in blood so less O2 in tissues so reduces the amount of O2 in heart muscle which can lead to a heart attack
OR
- fewer antioxidants which are important for protecting cells from damage, fewer antioxidants means cells damage in the coronary artery walls more which can lead to atheroma formation.
3. ) High blood pressure
- increases risk of damage to artery walls
- damaged walls have increased risk of atheroma formation causing more increase in blood pressure
- atheromas lead to blood clots
- blood clots could block flow of blood to heart muscle --\> heart attack
168
what type of lifetsyles increase the risk of cardiovascular disease?
- not exercising
- excessive alcohol consumption
- being overweight
169
what are the two types of tissues involved in the transport of plants?
1. ) Xylem; transpots water and mineral ions in solution which move up the plant from the roots to the leaves
2. ) Phloem; transports organic substances like sugars both up and down the plant
170
describe the structure of the xylem vessel
- very long
- tuble like structures fromed from dead cells joined end to end
- no end walls on these cells, making am uninterrupted tube which allows watet to pass through the middle easily
171
how does water move up the plant?
1. ) water evaporates from mesophyll cells due to heat from the sun at the top of the xylem
2. ) Thi creates tension (suction) which pulls more water into the leaf
3. ) water molecules are cohesive so when some are pulled into the lead others follow, this means the whole coloumn of water in the xylem from the leaves down to the roots, moves upwards
4. ) water enters the stem through the roots
172
what is transpiration?
the loss of water from a plant's surface
1. ) water evaporates from the moist cell walls and accumulated int he spaces between cells in the leaf
2. ) when the stomata open, it moves out of the leaf down the concentration gradient ( theres more water inside the leaf than in the air outside)
173
what are the 4 main factors that affect the rate of transpiration?
1. ) Light:
- the lighter it is the faster the transpiration rate
- this is becasue the stomata opens when it gets light to let in CO2 for photosynthesis
2. ) Temperature:
- the higher the temperature the faste the transpiration
- warmer water molecules have more kinetic energy so they evaporate from the cells inside the leaf faster
- this increases the concentration gradient between the inside and outside of the leaf, making water diffuse out of the leaf faster
3. ) Humidity:
- the lower the humidity, the fast ther transpiration rate
- if the air around the plant is dry, the concentration gradient between the leaf and the air is increased, which increases transpiration
4. ) Wind:
- the windier it is, the faster the transpiration rate
- lots of air movement blows away water molecules from around the stomata
- increases the concentration gradient, which increases the rate of transpiration
174
what is the apparatus used to estimate transpiration rates?
-potometer
175
how does water move across the cells of the leaf?
- water is lost from mesophyll cells by evaporation from their cell walls to the air spaces of the leaf due to heat supplied by the sun
- these cells now have a lower water potential and so water enters by osmosis from neighbouring cells
- the loss of water from the neighbouring cells lowers their water potential
- they, in turn, take in water from their neighbours by osmosis
176
what evidence is there to support the cohesion-tension theory?
- change in diameter of tree trunks according to rate of transpiration; during the day transpiration is greatest as more tension (more negative pressure) in xylem, so walls of xylem vessels pulled inward and causes trunk to shrink in diameter.
- if a xyelm vessel is broken and air enters, tree can longer draw uo water bc continous coloumn of water is broken so water molecules cant stick together
- when a xylem vessel is broken, water does not leak out. instead air is drawn out, which is consistent with with it being under pressure
177
suggest one advantage of xylem vessels being dead cells in order to carry out their function effectively
living cells have a cell-surface memebrane and cytoplasm and water movement would be slowed as it crossed this membrane/ cytoplasm
178
the thickening of the cell wall in xylem vessels is often spiral
suggest three advantages to the plant of having this arrangement rather than continuos thickening
1. ) allows the vessel to elongate as the plant grows
2. ) allows stems to be flexible
3. ) uses less material and is therefore is less wasteful and plant has lower mass
179
how is the ploem tissue adapted for transporting solutes?
- Sieve tube elements: living tubular cells that are connected end to end which form the tube for transporting solutes, they hae no nucleus and few organelles so...
- Companion cell: ...theres a companion cell for each sieve tube element which carry out living functions for sieve cells e.g providing energy needed for the active transport of solutes
180
what is translocation?
translocation is the transport of organic substances in the phloem from source to sink
181
using the mass flow hypothesis explain how translocation happens in the phloem
At the source:
1. ) Active transport is used to actively load the solutes (e.g sucrose from photosynthesis) from companion cells into sieve tubes of the phloem at the source (e.g leaves)
2. ) this lowers the water potential inside the sieve tubes, so water enters the tubes by osmosis from the xylem and companion cells
3. ) this creates a high pressure inside the sieve tubes at the source end of the phloem
At the Sink:
1. ) at the sink end, solutes are removed from the phloem to be used up
2. ) This increases the water potential inside the sieve tubes, so water also leaves the tubes by osmosis
3. ) this lowers the pressure inside the sieve tubes
The results is a pressure gradient from the source end to the sink end
this gradient pushes solutes alond the sieve tubes towards the sink
when they reach the sink the solutes will be used (e.g in repsiration ) or stored (e.g starch)
182
state evidence that supports and questions the the mass flow hypothesis
Supporting evidence:
1. ) if a ring of bark (which includes the phloem, but no the xylem) is removed from a wood stem, a bulge forms above the ring, teh fluid from the bulge has higher conc of sugars than the fluid below the ring- evidence that there's a downward flow of sugars
2. ) a radioactive tracer such as C14 can be used to track the movement of organic substances in a plant
3. ) pressure in phloem can be investigted uing aphids (they pierce the phloem, ther their bodies are remived leaving the mouthparts behing, which allows the sap to flow out) the sap flows out quicker nearer the leaves than further down the stem -evidence that there is a pressure gradient
4. ) If a metabolic inhibitor (which stops ATP production) is put into the phloem, then translocation stop this is evidence that active transport is involved
Objections:
1. ) sugar travles to many different sinks, not just the one with the highest water potential as the model would suggest
2. ) the sieve plates would create a barrier to mass flow. a lot of pressure would be needed for the solutes to get through at a reasonable rate
183
End of topic
184
EQ: Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf.
4 marks
1. (Carbon dioxide enters) via stomata; 2. (Stomata opened by) guard cells; 3. Diffuses through air spaces; 4. Down diffusion gradient;
185
EQ: Use your knowledge of transpiration to explain the changes in the rate of flow in the xylem shown in the graph.
3 marks
Explain why the values for the pressure in the xylem are negative.
1 mark
1. Stomata open;
2. Transpiration highest around midday;
]3. Middle of day warmer / lighter;
4. (Increased) tension / water potential gradient;
5. Cohesion (between water molecules);
- Pressure in xylem is lower than atmospheric pressure
186
EQ: the thickness of the aorta wall changes all the time during each cardiac cycle. Explain why
1. (Aorta wall) stretches;
2. Because ventricle/heart contracts / systole / pressure increases;
3. (Aorta wall) recoils;
4. Because ventricle relaxes / heart relaxes /diastole / pressure falls;
5. Maintain smooth flow / pressure;
187
EQ: Use the information provided to explain the effect that glycaemic load of the diet has on the risk of developing CHD.
2 mark
1. For diet group 2 and above, increase in risk of CHD as GL increases;
2. (Higher GL diets lead to) more (harmful) lipids (in blood), so greater risk of atheroma;
3. Atheroma leads to blockage of coronary artery / increased risk of blood clot in coronary artery;
188
EQ: Describe how a heartbeat is initiated and coordinated
5 marks
1. SAN sends impulses across atria causes atria to contract
3. Impulses are blocked by non conducting collagen tissue which prevents the ventricle from contracting immediately
4. So Impulses goes to the AVN where there is a slight delay to let atriums empty
5. Impulse is then absorbed by the Bundle of His and travels down to apex of heart
6. reaches the purkinje fibres which then cause the ventricles to contract
