AQA A2 BIOL5 22nd June 2012
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Original post by DoaaK
we just finished unit 5 and i hate chapter 16, it makes no sense
How have you finished it already?!
Original post by Heyimdec
How have you finished it already?!
Don't worry we haven't finished it either- no where near finishing
Original post by ned6494
Don't worry we haven't finished it either- no where near finishing
We've only done 2 chapters, LOL.
Original post by Heyimdec
We've only done 2 chapters, LOL.
We finished off unit 4 in November, started unit 5 in December, went back to unit 4 in January, went back to unit 5 in February
Original post by thegodofgod
We finished off unit 4 in November, started unit 5 in December, went back to unit 4 in January, went back to unit 5 in February
How do you finish it so fast? How many lessons a week do you have of Biology?
Original post by Heyimdec
How do you finish it so fast? How many lessons a week do you have of Biology?
I'm not the person you're thinking you're talking to
I just interrupted to show how hectic our timetable is
EDIT: unless you mean how we finished Unit 4 so fast...
Original post by thegodofgod
I'm not the person you're thinking you're talking to
I just interrupted to show how hectic our timetable is
EDIT: unless you mean how we finished Unit 4 so fast...
I just interrupted to show how hectic our timetable is
EDIT: unless you mean how we finished Unit 4 so fast...
Yes, I did realise you had interrupted, haha. We have 4 lessons a week of biology, but we probably won't finish until March/April.
Original post by Heyimdec
Yes, I did realise you had interrupted, haha. We have 4 lessons a week of biology, but we probably won't finish until March/April.
We have 7 periods (35 mins each) of Biology a week; 3 doubles + 1 single, split up between 2 teachers.
We started Unit 4 as soon as study leave was over at the end of year 12 June exams - so we got a head start of about 6 weeks
Original post by thegodofgod
We have 7 periods (35 mins each) of Biology a week; 3 doubles + 1 single, split up between 2 teachers.
We started Unit 4 as soon as study leave was over at the end of year 12 June exams - so we got a head start of about 6 weeks
We started Unit 4 as soon as study leave was over at the end of year 12 June exams - so we got a head start of about 6 weeks
We have 6 periods (50 mins) of Bio a week 3 doubles hate biology
Original post by ned6494
We have 6 periods (50 mins) of Bio a week 3 doubles hate biology
Wow - I can't imagine sitting in 1 place for almost 2 hours
Btw guys, here's an essay that I made on ATP last April. I used the eBook and other sources for guidance.
Adenosine triphosphate (ATP) is a nucleotide that is used as a coenzyme in cells. It transports chemical energy within cells for metabolism. This complex molecule is comprised mainly of three phosphate groups that are attached to a pentose sugar. In essence , ATP is critical for all life, from the simplest to the most complex of entity. An intricate nanomachine, ATP is at the epicentre of the design and biological functioning of the natural world we live in today.
Nearly all living organisms produce ATP through respiration. In humans, muscle and liver cells require a lot of energy in the form of ATP to function properly. Firstly, glucose is phosphorylated in the cytoplasm by the addition of two phosphate ions that are provided by the hydrolysis of two ATP molecules by ATPase during its glycolysis. This phosphorylation makes the glucose more reactive by lowering the activation energy for the enzyme-controlled reactions that follow. Phosphoryalted glucose undergoes several steps until pyruvate is formed. This enters the mitochondrion and is decarboxylated, and oxidised. During oxidation by dehydrogenase enzymes, pyruvate transfers its hydrogen ions and electrons to electron carriers, NAD and FAD. These carriers transfer electrons to the electron transport chain, thus providing energy for hydrogen ions are pumped into the inter-membrane spaces of the cristae via chemiosmois. This is used to create an electrochemical gradient that drives the proton motive force of the axial on ATP Synthase to form ATP as part of oxidative phosphorylation.
In the absence of oxygen, glycolysis continues to produce 2 net ATP molecules per glucose. This is not as efficient as aerobic respiration, and so more carbohydrate stores need to be broken down to provide enough ATP to meet the organism metabolic and physical needs. During anaerobic respiration, reduced NAD oxidises pyruvate to lactate in animals and ethanol (& CO2) in plants and fungi.
Contraction of muscles requires ATP. When a muscle is stimulated by an action potential, calcium ions bind to troponin, which causes tropomyosin to move away from the binding site on actin filaments. This allows the myosin heads to attach to the actin, forming cross bridges. The myosin heads change angle, causing the actin to move over the myosin. ATP attaches to the myosin head, causing it to become detached from the actin filaments. Calcium ions activate ATPase to hydrolyse ATP to ADP and phosphate ions, a process that releases energy for myosin heads to resume normal position and so, the reformation of cross bridges. When muscle stimulation ceases, calcium ions are actively transported back into the sarcoplasmic reticulum against their concentration gradient, using energy from the hydrolysis of ATP by ATPase. Contraction of the muscle sarcomere allows the contraction of skeletal muscle, allowing the animal to move.
In a very active muscle, oxygen is rapidly used up in respiration to produce ATP for contraction. It takes time for the blood to supply more oxygen quickly. Therefore, there needs to be a means of providing energy to maintain efficiency of muscles; particularly important if an organism escaping from predation. A molecule known as phosphocreatine is one that can rapidly generate ATP from ADP and inorganic phosphate in aerobic conditions. This molecule is in plentiful supply within fast-twitch fibres that produce powerful contractions over short periods.
On use of ATP is in the formation of a resting potential in nerve cells. Hydrolysis of ATP provides energy that is used to pump out three sodium ions and pump in two potassium ions into the axon of a neurone through a NA+/K+ATPase pump by active transport. A reduction of the membrane permeability to sodium ions maintains a resting potential of -70mV on the inside of the axon. This ATP is provided by respiring shwann cells that are densely packed with mitochondria. These cells span the length of a myelinated axon, except at the nodes of ranvier. Moreover, ATP provides the energy to move and fuse vesicles containing the neurotransmitter, acetylcholine with the pre-synaptic membrane (exocytosis) as well as providing energy for the re-synthesis of acetylcholine from ethanoic acid and choline.
Autotrophic organisms produce ATP during photosynthesis to produce their own chemical energy. The photolysis of water yields hydrogen ions and electrons. Together with the electrons, the hydrogen ions are used to reduce NADP in the light-dependent reaction in the thylakoid. This reduced NADP is used to reduce glycerate-3-phosphate, using energy from the hydrolysis of ATP, to form triose phosphate and then glucose in the stroma of the chloroplast. Hydrogen ions also play a role in the production of ATP in the electron transport chains. They are pumped into the inter-membrane space and generate an electrochemical gradient that provides energy for the activation of ATPase, which combines ADP and inorganic phosphate ions to form ATP by photo-phosphorylation.
Mutualistic nitrogen fixing bacteria in the roots of leguminous plants reduce atmospheric nitrogen to ammonium containing compounds such as protein, using energy from ATP. These compounds are taken-up by the plant, to which the bacteria has a mutualistic relation with, in exchange for carbohydrates.
All organisms use ATP as an immediate energy source for processes such as active transport. In plants, root hair cells have specific channels for ions such as nitrate and potassium. These channels have the enzyme ATPase which hydrolyses ATP and releases energy to absorb the ions against a concentration gradient into the cell. This movement into the cell from the soil lowers the water potential of the roots hair cells allowing water to enter by osmosis. Movement of this water then takes place via the symplast pathways and apoplast pathways. Active transport of the mineral ions into the xylem allows the water to enter the xylem by osmosis, generating a hydrostatic pressure called the root pressure. This creates a push, which together with the cohesion-tension, pulls water up the xylem in a column through the hollow lignified xylem vessels.
In this essay, I have outlined how ATP is mainly produced in organisms and some of its uses. There is no doubt that ATP is essential for the survival of organisms. It really intrigues me that with every keystroke I am taking of this computer, ATP is acting in wondrous ways to keep me functioning; from providing energy to help muscles in my hand contract and so allow me to type, to providing me with the energy to think of what word I am going to type next. The overwhelming application of ATP amazes me and I am proud to have been given the knowledge to understand the theory behind such a vital component to the finite mechanism that is life.
Adenosine triphosphate (ATP) is a nucleotide that is used as a coenzyme in cells. It transports chemical energy within cells for metabolism. This complex molecule is comprised mainly of three phosphate groups that are attached to a pentose sugar. In essence , ATP is critical for all life, from the simplest to the most complex of entity. An intricate nanomachine, ATP is at the epicentre of the design and biological functioning of the natural world we live in today.
Nearly all living organisms produce ATP through respiration. In humans, muscle and liver cells require a lot of energy in the form of ATP to function properly. Firstly, glucose is phosphorylated in the cytoplasm by the addition of two phosphate ions that are provided by the hydrolysis of two ATP molecules by ATPase during its glycolysis. This phosphorylation makes the glucose more reactive by lowering the activation energy for the enzyme-controlled reactions that follow. Phosphoryalted glucose undergoes several steps until pyruvate is formed. This enters the mitochondrion and is decarboxylated, and oxidised. During oxidation by dehydrogenase enzymes, pyruvate transfers its hydrogen ions and electrons to electron carriers, NAD and FAD. These carriers transfer electrons to the electron transport chain, thus providing energy for hydrogen ions are pumped into the inter-membrane spaces of the cristae via chemiosmois. This is used to create an electrochemical gradient that drives the proton motive force of the axial on ATP Synthase to form ATP as part of oxidative phosphorylation.
In the absence of oxygen, glycolysis continues to produce 2 net ATP molecules per glucose. This is not as efficient as aerobic respiration, and so more carbohydrate stores need to be broken down to provide enough ATP to meet the organism metabolic and physical needs. During anaerobic respiration, reduced NAD oxidises pyruvate to lactate in animals and ethanol (& CO2) in plants and fungi.
Contraction of muscles requires ATP. When a muscle is stimulated by an action potential, calcium ions bind to troponin, which causes tropomyosin to move away from the binding site on actin filaments. This allows the myosin heads to attach to the actin, forming cross bridges. The myosin heads change angle, causing the actin to move over the myosin. ATP attaches to the myosin head, causing it to become detached from the actin filaments. Calcium ions activate ATPase to hydrolyse ATP to ADP and phosphate ions, a process that releases energy for myosin heads to resume normal position and so, the reformation of cross bridges. When muscle stimulation ceases, calcium ions are actively transported back into the sarcoplasmic reticulum against their concentration gradient, using energy from the hydrolysis of ATP by ATPase. Contraction of the muscle sarcomere allows the contraction of skeletal muscle, allowing the animal to move.
In a very active muscle, oxygen is rapidly used up in respiration to produce ATP for contraction. It takes time for the blood to supply more oxygen quickly. Therefore, there needs to be a means of providing energy to maintain efficiency of muscles; particularly important if an organism escaping from predation. A molecule known as phosphocreatine is one that can rapidly generate ATP from ADP and inorganic phosphate in aerobic conditions. This molecule is in plentiful supply within fast-twitch fibres that produce powerful contractions over short periods.
On use of ATP is in the formation of a resting potential in nerve cells. Hydrolysis of ATP provides energy that is used to pump out three sodium ions and pump in two potassium ions into the axon of a neurone through a NA+/K+ATPase pump by active transport. A reduction of the membrane permeability to sodium ions maintains a resting potential of -70mV on the inside of the axon. This ATP is provided by respiring shwann cells that are densely packed with mitochondria. These cells span the length of a myelinated axon, except at the nodes of ranvier. Moreover, ATP provides the energy to move and fuse vesicles containing the neurotransmitter, acetylcholine with the pre-synaptic membrane (exocytosis) as well as providing energy for the re-synthesis of acetylcholine from ethanoic acid and choline.
Autotrophic organisms produce ATP during photosynthesis to produce their own chemical energy. The photolysis of water yields hydrogen ions and electrons. Together with the electrons, the hydrogen ions are used to reduce NADP in the light-dependent reaction in the thylakoid. This reduced NADP is used to reduce glycerate-3-phosphate, using energy from the hydrolysis of ATP, to form triose phosphate and then glucose in the stroma of the chloroplast. Hydrogen ions also play a role in the production of ATP in the electron transport chains. They are pumped into the inter-membrane space and generate an electrochemical gradient that provides energy for the activation of ATPase, which combines ADP and inorganic phosphate ions to form ATP by photo-phosphorylation.
Mutualistic nitrogen fixing bacteria in the roots of leguminous plants reduce atmospheric nitrogen to ammonium containing compounds such as protein, using energy from ATP. These compounds are taken-up by the plant, to which the bacteria has a mutualistic relation with, in exchange for carbohydrates.
All organisms use ATP as an immediate energy source for processes such as active transport. In plants, root hair cells have specific channels for ions such as nitrate and potassium. These channels have the enzyme ATPase which hydrolyses ATP and releases energy to absorb the ions against a concentration gradient into the cell. This movement into the cell from the soil lowers the water potential of the roots hair cells allowing water to enter by osmosis. Movement of this water then takes place via the symplast pathways and apoplast pathways. Active transport of the mineral ions into the xylem allows the water to enter the xylem by osmosis, generating a hydrostatic pressure called the root pressure. This creates a push, which together with the cohesion-tension, pulls water up the xylem in a column through the hollow lignified xylem vessels.
In this essay, I have outlined how ATP is mainly produced in organisms and some of its uses. There is no doubt that ATP is essential for the survival of organisms. It really intrigues me that with every keystroke I am taking of this computer, ATP is acting in wondrous ways to keep me functioning; from providing energy to help muscles in my hand contract and so allow me to type, to providing me with the energy to think of what word I am going to type next. The overwhelming application of ATP amazes me and I am proud to have been given the knowledge to understand the theory behind such a vital component to the finite mechanism that is life.
Here's another one I posted on last years thread. This one was to practice for our EMPA, so it's quite rushed. Has a a few mistakes in it and isn't quite coherent but if it can help then that's good.
Gas Exchange in Living Organisms
In this essay, I am going to outline the process of gas exchange within several types of organisms.
Fick’s law states that the rate of diffusion across a membrane is directly proportional to the concentration gradient of the substance on the two sides of the membrane, which is also inversely related to the thickness of the membrane. Therefore, to increase efficiency of gas exchange between surfaces requires a large surface area: volume ratio, a thin partially membrane, a movement of the environmental medium and a movement of an internal medium to maintain a diffusion gradient.
Single-celled organisms, such as bacteria and protozoa, are in constant contact with their external environment. Being small, they have a large surface area: volume ratio that means they rely on diffusion for the exchange of gasses. These organisms are covered only by a cell-surface membrane, therefore oxygen, used for respiration, is absorbed across their body surface. In the same way, the co2 waste product produced in the link reaction and Krebs cycle of aerobic respiration, diffuses out through their body surface.
Most insects are terrestrial organisms. The problem of this is that they lose moisture from their body surface and become dehydrated: which may lead to desiccation. To compromise, they are adapted by having a small surface area: volume ratio as well as a thick waterproof covering. This need to conserve water is therefore in conflict with the need for efficient gas exchange. This indicates that insects cannot use their body surfaces to diffuse reparatory gasses. Instead, they have a special internal network of tubes that supply respiring tissues directly.
Gas enters the insect through tine pores on the body surface, known as spiracles, after which it travels into trachea. From here, it diffuses into tracheoles, which are permeable to gasses and water. A supply of oxygen is delivered down a concentration gradient directly into the cells themselves. Meanwhile, the co2 produced by tissues during respiration travels along this internal network and out to atmosphere down its diffusion gradient. Many larger insects actively ventilate their respiratory systems, by raising and lowering the volumes of their abdomens with muscle contractions.
Although the tracheal system is an efficient method of gas exchange, it has some limitations. It relies solely on diffusion to exchange gasses between the environment and cells. Diffusion pathways need to be short and so consequently, this limits the natural size that an insect can attain.
In the presence of light, autotrophs take up atmospheric co2 for photosynthesis in order to synthesise the sugars needed for respiration. The gas exchange surface of the plant is on the underside of the leaf. Small pores, called stomata allow the diffusion of carbon dioxide into the air spaces as oxygen diffuses out. The thin structure and flat shape of the leaf minimises the diffusion pathway as well as offering an increased surface area for gaseous exchange. The air spaces between the mesophyll cells allow a rapid spreading and expansion of the CO2 up through the leaf towards the palisade cells down a concentration gradient, by diffusion. Here it diffuses through the plasma membrane, through the cytoplasm and on into the stroma of chloroplasts where it undergoes the Calvin cycle. Similarly, oxygen produced in respiration leaves the plant through the reverse pathway to that of co2.
In contrary to respiratory gasses, water vapour is also lost through the plants gas exchange surface, the stomata. The evaporation of water through the gas exchange surface draws water up the xylem by cohesion-tension creating a transpiration stream that returns the water to the atmosphere.
Aquatic organisms, namely fish, have a waterproof, gas-tight outer covering. Being relatively large, they have a small surface area: volume ratio. This means that their body surface alone in not adequate to supply their respiratory gasses and so, they too have developed a specialised gas exchange surface: gills.
The gills are made up of stacks of gill filaments. Each filament has gill lamellae at right angles to itself which immensely increases the surface area of the gills for more efficient gas exchange. Gaseous exchange in fish relies on the principle of counter-current flow. This is where the flow of water over the gill lamellae and the flow of blood within them are in opposite direction. This helps maintain a steep diffusion gradient for oxygen across the entire length of the gill lamellae, which ensures that the blood absorbs about 80% of oxygen in the water. Blood acts as a transport medium, delivering oxygen to respiring tissues by mass transport.
Mammals have a complex gaseous exchange system. This is because organisms have evolved into larger and more complex structures and so the tissues and organs from which they are made of have become more specialised and dependent upon each other. There therefore needs to be an efficient system that is able to meet the respiratory needs of an active mammal.
Contraction allows ventilation of the lungs to take place in mammals. The contraction of the intercostal muscles and the flattening of the diaphragm moves the rib cage up and out, increasing the volume of the thorax. This decreases the pressure, allowing air to be drawn into the lungs down a pressure gradient. This introduces oxygen to the gas exchange surface, the epithelium of the alveoli of the lungs. This ventilates the epithelial cells of the alveoli, allowing oxygen to diffuse through the membrane of the cells. The oxygen then continues to diffuse through to the membrane of the red blood cells where it loads to haemoglobin, forming oxyhaemoglobin.
Red blood cells themselves are small cells that have a biconcave shape that can flex easily and offer a high surface area of contact with the capillary walls for efficient gas exchange. This reduces the diffusion pathway of the oxygen and carbon dioxide, increasing gas exchange rates. An absence of organelles also increases the room available for the haemoglobin, each molecule of which can load four oxygen molecules.
On contraction of the ventricles, the pressure forces the red blood cells through the body to regions where the partial pressure of oxygen is lower. These regions are that of respiring tissue which release co2. Co2 decreases pH around its immediate vicinity, which changes the shape of the haemoglobin molecule in red blood cells, to one that has a lower affinity to oxygen: thus, oxygen is released. Hydrostatic pressure forces the oxygen and other small molecules into the respiring tissues through the formation of a tissue fluid that allows aerobic respiration to take place, which ultimately leads to the production of ATP. Some co2 now binds with the haemoglobin molecules, forming carbaminoglobin, which is transported to the alveoli for gas exchange.
Relaxation of the intercostal muscle’s actin and myosin protein filaments and the arching of the diaphragm move the rib cage down and in, decreasing the volume of the thorax and increasing the pressure in the lungs to higher than atmospheric. This creates a pressure gradient that forces co2 back though the respiratory system and back out into the atmosphere.
Gas Exchange in Living Organisms
In this essay, I am going to outline the process of gas exchange within several types of organisms.
Fick’s law states that the rate of diffusion across a membrane is directly proportional to the concentration gradient of the substance on the two sides of the membrane, which is also inversely related to the thickness of the membrane. Therefore, to increase efficiency of gas exchange between surfaces requires a large surface area: volume ratio, a thin partially membrane, a movement of the environmental medium and a movement of an internal medium to maintain a diffusion gradient.
Single-celled organisms, such as bacteria and protozoa, are in constant contact with their external environment. Being small, they have a large surface area: volume ratio that means they rely on diffusion for the exchange of gasses. These organisms are covered only by a cell-surface membrane, therefore oxygen, used for respiration, is absorbed across their body surface. In the same way, the co2 waste product produced in the link reaction and Krebs cycle of aerobic respiration, diffuses out through their body surface.
Most insects are terrestrial organisms. The problem of this is that they lose moisture from their body surface and become dehydrated: which may lead to desiccation. To compromise, they are adapted by having a small surface area: volume ratio as well as a thick waterproof covering. This need to conserve water is therefore in conflict with the need for efficient gas exchange. This indicates that insects cannot use their body surfaces to diffuse reparatory gasses. Instead, they have a special internal network of tubes that supply respiring tissues directly.
Gas enters the insect through tine pores on the body surface, known as spiracles, after which it travels into trachea. From here, it diffuses into tracheoles, which are permeable to gasses and water. A supply of oxygen is delivered down a concentration gradient directly into the cells themselves. Meanwhile, the co2 produced by tissues during respiration travels along this internal network and out to atmosphere down its diffusion gradient. Many larger insects actively ventilate their respiratory systems, by raising and lowering the volumes of their abdomens with muscle contractions.
Although the tracheal system is an efficient method of gas exchange, it has some limitations. It relies solely on diffusion to exchange gasses between the environment and cells. Diffusion pathways need to be short and so consequently, this limits the natural size that an insect can attain.
In the presence of light, autotrophs take up atmospheric co2 for photosynthesis in order to synthesise the sugars needed for respiration. The gas exchange surface of the plant is on the underside of the leaf. Small pores, called stomata allow the diffusion of carbon dioxide into the air spaces as oxygen diffuses out. The thin structure and flat shape of the leaf minimises the diffusion pathway as well as offering an increased surface area for gaseous exchange. The air spaces between the mesophyll cells allow a rapid spreading and expansion of the CO2 up through the leaf towards the palisade cells down a concentration gradient, by diffusion. Here it diffuses through the plasma membrane, through the cytoplasm and on into the stroma of chloroplasts where it undergoes the Calvin cycle. Similarly, oxygen produced in respiration leaves the plant through the reverse pathway to that of co2.
In contrary to respiratory gasses, water vapour is also lost through the plants gas exchange surface, the stomata. The evaporation of water through the gas exchange surface draws water up the xylem by cohesion-tension creating a transpiration stream that returns the water to the atmosphere.
Aquatic organisms, namely fish, have a waterproof, gas-tight outer covering. Being relatively large, they have a small surface area: volume ratio. This means that their body surface alone in not adequate to supply their respiratory gasses and so, they too have developed a specialised gas exchange surface: gills.
The gills are made up of stacks of gill filaments. Each filament has gill lamellae at right angles to itself which immensely increases the surface area of the gills for more efficient gas exchange. Gaseous exchange in fish relies on the principle of counter-current flow. This is where the flow of water over the gill lamellae and the flow of blood within them are in opposite direction. This helps maintain a steep diffusion gradient for oxygen across the entire length of the gill lamellae, which ensures that the blood absorbs about 80% of oxygen in the water. Blood acts as a transport medium, delivering oxygen to respiring tissues by mass transport.
Mammals have a complex gaseous exchange system. This is because organisms have evolved into larger and more complex structures and so the tissues and organs from which they are made of have become more specialised and dependent upon each other. There therefore needs to be an efficient system that is able to meet the respiratory needs of an active mammal.
Contraction allows ventilation of the lungs to take place in mammals. The contraction of the intercostal muscles and the flattening of the diaphragm moves the rib cage up and out, increasing the volume of the thorax. This decreases the pressure, allowing air to be drawn into the lungs down a pressure gradient. This introduces oxygen to the gas exchange surface, the epithelium of the alveoli of the lungs. This ventilates the epithelial cells of the alveoli, allowing oxygen to diffuse through the membrane of the cells. The oxygen then continues to diffuse through to the membrane of the red blood cells where it loads to haemoglobin, forming oxyhaemoglobin.
Red blood cells themselves are small cells that have a biconcave shape that can flex easily and offer a high surface area of contact with the capillary walls for efficient gas exchange. This reduces the diffusion pathway of the oxygen and carbon dioxide, increasing gas exchange rates. An absence of organelles also increases the room available for the haemoglobin, each molecule of which can load four oxygen molecules.
On contraction of the ventricles, the pressure forces the red blood cells through the body to regions where the partial pressure of oxygen is lower. These regions are that of respiring tissue which release co2. Co2 decreases pH around its immediate vicinity, which changes the shape of the haemoglobin molecule in red blood cells, to one that has a lower affinity to oxygen: thus, oxygen is released. Hydrostatic pressure forces the oxygen and other small molecules into the respiring tissues through the formation of a tissue fluid that allows aerobic respiration to take place, which ultimately leads to the production of ATP. Some co2 now binds with the haemoglobin molecules, forming carbaminoglobin, which is transported to the alveoli for gas exchange.
Relaxation of the intercostal muscle’s actin and myosin protein filaments and the arching of the diaphragm move the rib cage down and in, decreasing the volume of the thorax and increasing the pressure in the lungs to higher than atmospheric. This creates a pressure gradient that forces co2 back though the respiratory system and back out into the atmosphere.
Original post by Heyimdec
How have you finished it already?!
we didn't have january modules, we haven't finished unit 4 yet but we've just finished unit 5, my school's weird, don't worry :P
I'm taking unit four and unit five this summer, but I'm still working though unit four. It's amazing that you're nearly done so early, is this your only exam this summer?
Hey does anyone have the June 2011 unit 5 paper, if so could you please post it, would be much appreciated.
We've got section 3.5.8 to go and we're done wooooo
Only the EMPA and revision to go soon
Only the EMPA and revision to go soon
Original post by al_habib
guys i know its too early to start with unit 5 but yeah am off to chapter 14, hopefully i finish this by tomorrow, and then do questions at the end of the chapter.
i'll post notes, essays and relevant websites on BIOL5
this site have good bio notes --> http://www.heckgrammar.kirklees.sch.uk/index.php?p=10312
i'll post notes, essays and relevant websites on BIOL5
this site have good bio notes --> http://www.heckgrammar.kirklees.sch.uk/index.php?p=10312
That link is awesome, thanks for sharing!
+rep
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