PAper 1B Flashcards
why do single celled organisms use diffusion, and diffusion alone, to provide their nutrients ?
As the diffusion pathway is short
What do Multicellular organisms require to provide all of their cells with the nutrients they need??
transport systems and specialised exchange surfaces
Why do organisms with higher metabolic rates need an increased diffusion rate?
They exchange more mterials
What happens to the SA:V ratio as the object becomes bigger?
The ratio of surface area: volume ratio falls
Small organisms has a ____ SA:V ratio and exchange ____ with the _____
.Large.Directly.Surface
Larger organisms has a ____ SA:V, and they need _______ exchange surfaces to meet the organisms demands
.Smaller.Specialist
Give an example of a larger organisms specialist exchange surface
Mass transport system, to deliver and remove material
Sphere surface area formula
4 x Pi x r^2
Sphere volume formula
(4/3) x Pi x r^3
If a gas exchange surface is efficient at gas exchange, what else is it efficient at?
an efficient water loss surface
How do insects limit water loss?
.Rigid exoskeleton – chitin, waterproof cuticle.Small SA:V ratio – minimises water loss area.Spiracles – open and close to prevent water loss
What is the tracheal system?
The tracheal system is a system of tubes in insects that supply muscles with oxygen directly
Trachea divide into
tracheoles
Tracheoles branch throughout
the body tissues of the insect
What are spiracles and what do they do?
Spiracles are tiny pores at the end of the tracheaAllow respiratory gases in and out of the insectValves control the opening/closure of the spiracleWhen open, water can evaporate out of the spiracleClosed most of the timeOnly open to allow gas exchange
Limitations of the tracheal system?
.Relies on diffusion rather than a transport system.For diffusion to be adequate the diffusion distance must be short.This limits the size that insects can grow to
Describe and explain the diffusion gradients in the tracheal system
.During respiration, O2 is used.O2 at tracheole ends falls.Creates a diffusion gradient.O2 diffuses from atmosphere along the tracheas and tracheoles to the cells.CO2 is produced by respiring cells.Diffusion gradient in opposite direction.CO2 diffuses out of the tracheoles and into the atmosphere
Describe and explain muscle contractions in the tracheal system
.Abdominal pumping.Contraction of insect muscles.Trachea ‘squeezed’ and reduced in volume.Some air will be expelled from the trachea.Common in larger insects.Uses energy
Describe and explain water in the tracheoles
.Anaerobic respiration produces lactate.Lactate is water soluble so lowers water potential of muscles cells.Water moves into muscle cells from tracheoles.Volume in the tracheole ends decreases, drawing air in
What is a dicotyledonous?
.(dye coto lee denous).Flowering plants.The seed bears two cotyledons (seed leaves)
What gases are important in plants?
CO2 and O2
Photosynthesis equation
6CO2 + 6H2O C6¬H12O6 + 6O2
Aerobic respiration equation
C6¬H12¬O6 + 6O2 6CO2 + 6H2O + ATP
Why do plants leaves have a large SA?
greater surface for diffusion to take place
Why are plants leaves thin?
Short diffusion pathway
Why are plants leaves membranes selectively permeable?
Control what goes in and out of the cell
Why do plants leaves have a large diffusion gradient?
Increased rate of diffusion
What reactions happen in a plant at night?
Respiration
\What reactions happen in a plant in the day?
Respiration and photosynthesis
What parts make up a plant leaf?
- Waxy cuticle2. Upper epidermis3. Palisade mesophyll cells4. Spongy mesophyll cells5. Sub-stomatal air space6. Lower epidermis cells7. Stomata8. Guard cells9. Sheath10. Phloem11. Xylem
How does a stomata facilitate efficient exchange?
Small pores, allow gases in and out, all cells are close to a stomatal pore therefore there is a short diffusion pathway
How do the air spaces facilitate efficient exchange?
Interconnected air spaces throughout the mesophyll layer so gases can move around mesophyll cells
How does the spongy mesophyll layer facilitate efficient exchange?
Large surface area of mesophyll cells allow for maximum diffusion
What happens to the stomata during the day? Why?
Open during the day, as photosynthesis is occurring it needs to allow the CO2 in and O2 out and water vapour out
What happens to the stomata during the night? Why?
Closed during the night, no photosynthesis so no need for CO2
Name the parts of a plant cell
- Nucleus2. RER3. Ribosomes4. Cell wall5. Golgi apparatus6. Chloroplast7. Mitochondria8. Cell membrane9. Vacuole10. Amyloplast (produces and stores starch)11. SER
Where are gills found?
Behind the fishes head
What are gills made up of?
Gill filaments
How are gill filaments arranged?
Stacked up in piles
What are perpendicular to the gill filaments?
Gill lamellae
What do gill lamellae do?
Increase gill SA
Describe the movement of water in a fishes gas exchange system
.Water is taken in through the mouth, forced over the gills, and out through the opening on each side of the body
What is countercurrent flow?
.The flow of water over the gill lamellae and the flow of blood within them are in opposite directions, this is known as countercurrent flow
Why is countercurrent flow important in fish?
.This means the maximum possible gas exchange can be achieved, if the water and blood flowed in the same direction, far less gas exchange would take place
How does countercurrent flow work?
- Blood that is already well loaded with oxygen meets water which has its maximum concentration of oxygen, therefore diffusion of oxygen from the water to the blood takes place- Blood with little oxygen in it meets water which has had most, but not all, oxygen removed, so diffusion of oxygen from the water to the blood takes place
What does countercurrent exchange principle mean for the diffusion gradient?
a diffusion gradient for oxygen uptake is maintained across the entire width of the gill lamellae
In countercurrent flow, how much oxygen from the water is absorbed into the blood of the fish?
about 80% of the oxygen available in the water is absorbed into the blood of the fish
What would happen if there was parallel flow in fish?
.If the flow of water and blood had been the same in the same direction (parallel flow), the diffusion gradient would only be maintained across part of the length of the gill lamellae and only 50% of the available oxygen would be absorbed by the blood
Why are gills good exchange surfaces?
.High SA.Good blood supply.countercurrent flow
Why do plants rely on the transpiration stream? How is it made?
.Plants rely on the transpiration stream to transport water from their roots to their leaves.The transpiration stream is created as water is evaporated from the surface of the leaf
What are xerophytes?
Plants adapted to living in areas with a short supply of water
How do plants prevent water loss?
A thick cuticle, rolled up leaves, sunken stomata, hairs on leaves, reduced SA:V ration
How does a a thick cuticle prevent water loss?
Waxy cuticle acts as a waterproof barrier
How do rolled up leaves prevent water loss?
Stomata on lower epidermis protected/trap still air Traps water vapour so high water potential No water potential gradient between plant and air
How does a sunken stomata prevent water loss?
Traps still, moist air next to the lead surface Lower water potential gradient
How does having hairs on leaves prevent water loss?
Traps still, moist air next to leaf surface Lower water potential gradient
How does having a reduced SA:V ratio prevent water loss?
Slower rate of diffusion Still able to photosynthesise
Respiration equation
C6H12O6 + O2 CO2 + H2O + ATP
Name components of the lungs
- Lung2. Nasal cavity3. Bronchiole4. Alveoli5. Intercostal muscles6. Ribs7. Diaphragm8. Lung9. Bronchus10. Trachea11. Bronchus
Features of lungs
Lobed structures
Features of trachea
Flexible airway supported by cartilage rings.Muscular walls lined with ciliated epithelium and goblet cells
Features of bronchi
Trachea splits into two bronchi.Large bronchi are supported by cartilage rings.Lined with ciliated epithelium and goblet cells
Features of bronchioles
.Subdivisions of bronchi.Muscular walls lined with epithelium cells.Can constrict to control air flow
Where are alveoli and what are they?
Alveoli are located at the end of bronchioles. They are the site of gas exchange in mammals. Tiny air sacs (100-300 um).
Why are lungs on the inside?
If they were on the outside they would dry out and get damaged
How many alveoli do we have?
300 mil
How much SA does the alveoli have?
70m^2
What are alveoli lined with?
epithelial cells
Why are alveoli good surfaces for gas exchange?
- Short diffusion pathway (one cell thick), large SA, constant concentration gradient maintained through good blood supply, red blood cells slowed down and flattened against capillary wall
What is breathing/ventilation?
the constant movement of air into and out of the lungs
What is respiration?
the chemical process of using glucose and oxygen to produce carbon dioxide and ATP while releasing energy
Define inspiration
pressure outside the lungs is greater than inside, air moves in
Define expiration
pressure inside the lungs is greater than outside, air forced out
Muscles involved in ventilation/breathing?
- Internal intercostal muscles- External intercostal muscles- Diaphragm
How does a bell jar work?
.The rubber sheet moves down, the volume in the bell jar increases so the pressure in the bell jar decreases, the pressure inside the bell jar is greater than outside, air moves in via the balloons and inflates them
Explain how inspiration works?
.External intercostal muscles contract, internal intercostal muscles relax.Rib cage pulled up and out.Increases volume of thorax.Diaphragm muscles contract and diaphragm moves down.Increases volume in thorax further and reduces pressure inside.Atmospheric pressure is now greater than pulmonary pressure.Air is forced into lungs
Explain how expiration works?
.External intercostal muscles relax, internal intercostal muscles contract.Rib cage pushed down and in.Decreased volume of thorax.Diaphragm muscles relax and diaphragm moves up.Decreases volume in thorax further and increases pressure inside.Atmospheric pressure is now less than pulmonary pressure.Air is forced out of the lungs
Is inspiration passive or active?
Active
Is expiration passive or active?
Passive
Define tidal volume
The volume of air inhaled and exhaled in normal breath
Define expiatory reserve volume
Volume of a maximum exhalation after normal exhalation
Define residual volume
Volume remaining in the lune after maximum exhalation
Define inspiratory reserve volume
Additional volume that can be inhaled after inhalation of tidal volume
Define vital capacity
maximum volume of exhalation after lungs are maximally filled
Pulmonary ventilation rate equation with units
Pulmonary ventilation rate (dm3min-1) = tidal volume (dm3) x breathing rate (min-1)
Name the 4 main lung diseases we need to know about
Pulmonary fibrosis, tuberculosis, asthma, emphysema
Describe pulmonary fibrosis
.Scaring forms on the epithelium lining of the lungs.This causes the lining to thicken.This reduces the amount of oxygen able to diffuse across the membrane and into the bloodalso.The volume of air entering the lungs is also reduced.A healthy lung is elastic allowing it to spring back into shape, expelling air.Fibrosis reduces the elasticity of the lungs, making it more difficult to breathe out.This inhibits ventilation
Symptoms of pulmonary fibrosis
Shortness of breath, especially when exercising Chronic, dry cough Pain and discomfort in the chest Weakness and fatigue
How does pulmonary fibrosis cause shortness of breath, especially when exersizing?
.Fibrosis tissue occupies space in the lung.This reduces the air space available.less air=less oxygen.oxygen in high demand during exercise, breathing more, but can’t get the oxygen needed
How does pulmonary fibrosis cause a chronic, dry cough?
.The fibrosis tissue causes an obstruction in the lung.The body attempt to remove it by coughing, but it won’t move.So you are always coughing
How does pulmonary fibrosis cause pain and discomfort in the chest?
The mass of fibrosis tissue causes pressure, leading to pain.Discomfort leads to more coughing which causes more scaring
How does pulmonary fibrosis cause weakness and fatigue?
.Respiration reduced due to lack of oxygen
Describe tuberculosis?
.Formation of small hard lumps called tubercles in lungs.Stimulation of the white blood cells to fight these results in scar tissue.Can lay dormant
Cause of tuberculosis
A bacteria
Symptoms of tuberculosis
Persistent coughFatigueLoss of appetiteHigh temperatureChest painsFeverCoughing up blood
Describe asthma
The cells of the epithelial lining secrete larger quantities of mucus than normalThe muscles surrounding the bronchioles contract and so constricts the airways
How many people does asthma affect?
10% of world populationKills 2000 people in the UK each year
Cause of asthma
Localised allergic reactionCommon allergens include:.Pollen.Animal fur.Faeces of house dust mitesAllergens stimulate WBC found in the lining of the bronchi and bronchioles to release histamineHistamine causes:.InflammationLining of airways becomes inflamed
Symptoms of asthma
Difficulty breathingWheezingTightness in chestCoughing
Describe emphysema
Loss of elasticity preventing expansion and contractionCommon in smokersThe lungs have been permanently stretchedSo no longer able to expel all of the air from the alveoliSome alveoli burst, the surface area of alveoli reduced, little gas exchange occurs
Cause of emphysema
smoking
symptoms of emphysema
Shortness of breathChronic coughBluish skin
Name the parts of the digestive system
- Tongue2. Salivary gland3. Lobe of liver4. Gall bladder5. Traverse limb of the large intestine6. Ascending limb of the large intestine7. Salivary gland8. Oesophagus9. Stomach10. Pancreas11. Small intestine12. Descending limb of the large intestine13. Rectum14. Anus
What is digestion?
Digestion is the process in which large molecules are hydrolysed by enzymes into small molecules which can be absorbed and assimilated.
What does the oesophagus do?
The oesophagus carries food from the mouth to the stomach
What is the stomach?
a muscular sac with an inner layer that produces enzymes
What is the role of the stomach?
to store and digest food, especially proteins. It has glands that produce enzymes which digest proteins
What is the ileum?
a long muscular tube
What happens in the ileum?
Food is further digested in the ileum by enzymes that are produced by its walls and by glands that pour their secretions into
How is the ileum adapted for its purpose of absorbing the products of digestion into the blood stream?
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.
What does the large intestine do?
Absorb waterMost of the water that is absorbed is water from the secretions of the many digestive glands
What happens in the rectum?
rectum is the final section of the intestines. The faeces are stored here before periodically being removed via the anus in a process called egestion
Where are the salivary glands?
Near the mouth
What does the salivary glands do?
They pass their secretions via a duct into the mouth. These secretions contain the enzymes amylase, which hydrolyses starch into maltose
What is the pancreas?
a large gland situated below the stomach
What does the pancreas do?
The secretion contains proteases to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse starch
What are the two stages of digestion in humans?
- Physical breakdown2. Chemical digestion
What is physical breakdown and why does it happen?
If food is large it is broken down by means of structures like the teeth into smaller pieces. This not only makes it possible to ingest the food but also provides a large surface area for chemical digestion. Food is churned by the muscles in the stomach wall and this also physically breaks it up.
What happens in chemical digestion?
Hydrolyses large insoluble molecules into smaller soluble ones
What carries out chemical digestion?
Enzymes
How do all enzymes function?
Hydrolysis
What is hydrolysis
the splitting up of molecules by adding water to the chemical bonds that hold them together
How does one molecules hydrolysis from enzymes usually work?
Usually one enzyme hydrolyses a large molecule into sections, and these sections are then hydrolysed into smaller molecules by one or more additional enzymes
What are the different types of digestive enzymes and their reactions?
- Carbohydrase’s hydrolyse carbohydrates to monosaccharides2. Lipases hydrolyse lipids (fats and oils) into glycerol and fatty acids3. Proteases hydrolyse proteins to amino acids
Where is the enzyme amylase produced?
The mouth and pancreas
What does amylase do?
Amylase hydrolyses the alternate glyosidic bonds of the starch molecules to produce the disaccharide maltose
What does the disaccharade maltase do?
maltose is in turn hydrolysed into the monosaccharide a-glucose by it
What is maltase produced by?
The lining of the ileum
What is the full process of carbohydrate digestion in humans?
- Saliva enters the mouth from the salivary glands and is thoroughly mixed with food when chewing- Saliva contains salivary amylase, this starts hydrolysing any starch in the food to maltose. It also contains mineral salts which help to maintain the pH at around neutral. - The food is swallowed and enters the stomach, where the conditions are acidic, this acid denatures the amylase and prevents further hydrolysis of the starch- After a time the food is passed into the small intestine, where it mixes with the secretion from the pancreas called the pancreatic juice- The pancreatic juice contains pancreatic amylase, this continues the hydrolysis of any remaining starch to maltose, alkaline salts are produced by both the pancreas and intestinal wall to maintain the pH at around neutral so that the amylase can function- Muscles in the intestine wall push the food along the ileum, its epithelial lining produces the disaccharide maltase, the maltase hydrolyses the maltose from starch breakdown into a-glucose.
What is the optimum pH for amylase?
Neutral
Why is maltase referred to as a membrane bound disaccharidase?
It is not released into the lumen of the ileum but is a part of the cell surface membranes of the epithelial cells that line the ileum
Where is sucrose found?
in many natural foods, especially fruits.
Where is lactose found?
in milk and hence any milk products
What does sucrase do?
hydrolyses the single glyosidic bond in the sucrose molecule, this hydrolyses produces the two monosaccharides glucose and fructose.
What does lactase do?
hydrolyses the single glyosidic bond in the lactose molecule, this hydrolysis produces the two monosaccharides glucose and galactose.
What are lipids hydrolysed by?
Enzymes called lipases
What are lipases?
enzymes produced in the pancreas that hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides
What is a monoglyceride?
a glycerol molecule with single fatty acid molecule attached
What is emulsification and why does it happen?
Lipids (fats and oils) are firstly split up into tiny droplets called micelles by bile salts, which are produced by the liver.This process is called emulsification and increases the surface area of the lipids so that the action of lipases is sped up
What are proteins hydrolysed by?
a group of enzymes called peptidases (proteases)
What do endopeptidases do?
hydrolyse the peptide bonds between amino acids in the central region of the peptide molecule forming a series of peptide molecules
What do exdopeptidases do?
hydrolyse the peptide bonds on the terminal amino acids of the peptide molecules formed by the endopeptidases. In this way they progressively release dipeptides and single amino acids
What do dipeptidases do?
hydrolyse the bond between the two amino acids of a dipeptide. Dipeptidases are membrane bound, being part of the cell surface membrane of the epithelial cells lining the ileum
What helps maintain the neutral pH for amylase?
Saliva contains mineral salts that maintain the neutral pH for amylase
How is protease kept at the right pH?
Stomach produces hydrochloric acid which provides an acidic pH for protease
What allows amylase to function after the stomach, how?
Alkaline salts are produced by the pancreas and intestinal wall to neutralise stomach acid and allow amylase to function.Bile salts produced by the liver and released/stored in the gall bladder also helps as it is alkaline
Describe the structure of bile salts
.One end is soluble in fat (lipophilic) but not in water (hydrophobic).The other side is insoluble in fat (lipophobic) but soluble in water (hydrophilic)
Describe the process of the absorption of triglycerides
.Lipid mixed with bile salts.This forms micelles.Monoglycerides and fatty acids releases.Monoglycerides and fatty acids are absorbed through the membrane of the ileum.Monoglycerides and fatty acids are converted back to triglycerides in the endoplasmic reticulum.Triglycerides are packaged into chylomicrons.Chylomicrons released by exocytosis.Chylomicrons go into lymphatic vessels and then into the blood stream
What are chlymicrons?
Small milky globules.A small fat globule composed of proteins (1-2%) and lipid.They transport fat from the intestines to the liver and to adipose (fat) tissue.After a fatty meal, the blood is so full of chylomicrons that it looks milky.The chylomicrons are synthesised in the mucosa (the lining) of the intestine
Define mass transport
the bulk movement of materials from exchange surfaces to the cells throughout the organism
What do efficient transport systems have?
- A suitable transport mediumo Normally liquid but can be a gaso Materials (oxygen, waste) can dissolve- Closed system of tubular vesselso Contains or holds the mediumo Forms branching to all parts of the organismo Ensures medium is close to cells- Mechanisms for movement of tissue fluido Generates pressureo Enables the medium to move
What is the circulatory systems transport medium, tubular vessels and mechanisms for movement of tissue fluid?
Blood, veins/arteries/capillaries and heart
What type of muscle is the heart?
A cardiac muscle
What is the heart?
An organ in the circulatory system
The heart is myogenic, what does this mean?
It naturally contracts and relaxes
Describe our circulatory system
Double
How is the heart apart of a double circulatory system?
Blood passes the heart twice, through two different circuits
In the circulatory system, what is circuit one?
links the heart and the rest of the body
In the circulatory system, what is circuit two?
links the heart with the lungs
Name the parts of the heart
- Right atrium2. Right ventricle3. Left atrium4. Left ventricle5. Pulmonary artery6. Aorta7. Superior vena cava8. Inferior vena cava9. Pulmonary vein10. Septum11. SAN node
What is the SAN node
the hearts pace maker, initiates an electrical wave of electricity
How do the coronary arteries maximise mass transport?
- Coronary arteries supply the heart with the oxygen it requires, the oxygen is needed so that the heart can contract and pump blood around the bod
How does the wall thickness of the heart maximise mass transport?
left ventricle wall is much thicker to produce necessary pressure, since it is thicker it can contract much stronger, this increases the pressure so the blood can travel around the entire body
How do the valves of the heart maximise mass transport?
open and close between atriums and ventricles as well as ventricles and vessels to help produce necessary pressure and prevent backflow. This also generally builds pressure in the blood
What are the 3 heart valves and where are they?
- Semi-lunar valves (between ventricle and vessel)- Left atrioventricular valve (tricuspid valve) between left atrium and left ventricle- Right atrioventricular valve (bicuspid valve) between right atrium and right ventricle
Describe the opening and closing of valves?
- Pressure is higher where concave (as ventricle fills with blood)- Pushes the flexible, fibrous tissues together- Tissues form a tight fit with no gap- Prevents the backflow of blood (back into the atrium)- Pressure is higher above the valve- Pushes the flexible fibrous tissues apart- Causes opening for blood to travel (from high to low pressure) into the ventricle
What causes the hearts beat sound?
The opening and closing of valves
Advantages of biological valve replacements
Cows are in high supplyFairly well testedFewer long term issues
Disadvantages of biological valve replacements
Unethical to use cowsNot suitable for allCan need replacing
What is systole?
contraction
What is diastole?
relaxation
What happens in ventricular systole?
ventricle completely full, forces tricuspid and bicuspid valves to close, forces semi-lunar valve to open, pushes blood out of the heart
What happens in atrial systole?
pushes last bit of blood into ventricle, ventricular diastole occurs in this stage
What happens in ventricular and atrial diastole?
They relax, makes up the majority of the cycle, blood movement is aided by gravity
What is haemoglobin
A respiratory pigment used to transport oxygen
What type of molecule is haemoglobin?
A protein
Why is haemoglobin needed?
as oxygen has a low solubility in water
Describe the structure of haemoglobin
Each haemoglobin has beta polypeptides, alpha polypeptides and four haem groups (1 per polypeptide chain) which contain a ferrous ion (Fe2+)Each haem group carries one O2 molecule
What is haemoglobin called when it is combined with oxygen?
oxyhaemoglobin
What must haemoglobin do to be efficient?
- Readily associate with oxygen at the exchange surface2. Readily dissociate with oxygen at the tissues
Define affinity
the attractive force binding atoms in molecules, chemical attraction
What is high affinity with haemoglobin?
high attractive force, readily associates with O2
What is low affinity with haemoglobin?
take up less O2 (lower association) but release more readily (easily disassociation)
In the body, where is oxygen affinity high and low?
High in exchange surfaces (lungs) and low in respiring tissues (muscles)
How does affinity change?
- The environment:.How much oxygen is available.Partial pressure of oxygen2. Metabolic rate:.How much oxygen is required by the organism
What is partial pressure of oxygen?
.The amount of gas present in a mixture of gases .Measured in kilopascals (kPa)
If the environment has a low concentration (partial pressure) of oxygen:
- Need haemoglobin to hold onto oxygen- High affinity for oxygen- Hold onto oxygen tightlyBUT- Means oxygen will not be used up as readily- Organisms have a low metabolic rate
If the environment has a high concentration (partial pressure) of oxygen:
- Oxygen is readily available- Do not need to hold on to oxygen - Low affinity for oxygenSO- Oxygen dissociates easily
How does partial pressure differ throughout the body?
.High at exchange surfaces.Low at muscles, where it has been used to respire
How does haemoglobin change how it works in different pO2 levels?
Low pO2, difficult to attach the first O2Medium pO2, changed shape means it can easily associate (disrupt bonds in the structure)High pO2, fewer binding sites so difficult to fully saturate
What is an oxygen dissociation curve
Relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen
Drawn an oxygen dissociation curve
IDK Chec your notes
Describe oxygen dissociation curve
The higher the pO2 the more saturation of haemoglobin with oxygen. At low pO2, the rate of increase of saturation of haemoglobin with oxygen is low, then it speeds up as pO2 increases, before again slowing as pO2 reaches large values.
Explain oxygen dissociation curve
At low pO2, the rate of increase of saturation of haemoglobin with oxygen is low as it is initially difficult to attach the first O2. The rate of increase of saturation of haemoglobin with oxygen increases as the changed shape of the haemoglobin means it can easily associate (disrupt bonds in the structure). The rate of increase of saturation of haemoglobin with oxygen slows again as pO2 reaches large values, because the fewer binding sites make it difficult to fully saturate.
What does a shift to the left on an oxygen dissociation curve mean?
NAME?
What does a shift to the right on an oxygen dissociation curve mean?
NAME?
What is the Bohr Effect?
Haemoglobin has a reduced affinity for oxygen in the presence of carbon dioxide. The greater the concentration of carbon dioxide, the more readily the haemoglobin releases it
Why does the behaviour of haemoglobin change in different regions of the body?
The Bohr Effect
Describe and explain the behaviour of haemoglobin at the gas exchange substance (lungs)?
- At the gas exchange surface (lungs), the level of carbon dioxide is low because it diffuses across the exchange surface and is expelled from the organism. The affinity of haemoglobin for oxygen is increased, which, coupled with the high concentration of oxygen in the lungs, means that oxygen is readily loaded by haemoglobin. The reduced carbon dioxide level has shifted the oxygen dissociation curve to the left.
Describe and explain the behaviour of haemoglobin at rapidly respiring tissues (muscles)?
- In rapidly respiring tissues (muscles), the level of carbon dioxide is high. The affinity of haemoglobin for oxygen is reduced, which, coupled with the low concentration of oxygen in the muscles, means that oxygen is readily unloaded from the haemoglobin into the muscle cells. The increased carbon dioxide level has shifted the oxygen dissociation curve to the right.
Why is it that the greater the concentration of carbon dioxide, the more readily haemoglobin releases its oxygen?
Because dissolved carbon dioxide is acidic and the low pH causes haemoglobin to change shape.
Describe and explain the loading, transporting and unloading of oxygen
- At the gas exchange surface carbon dioxide is constantly being removed- The pH is raised due to the low level of carbon dioxide- The higher pH changes the shape of haemoglobin into one that enables it to load oxygen readily- This shape also increases the affinity of haemoglobin for oxygen, so it is not released while being transported in the blood to the tissues- In the tissues, carbon dioxide is produced by respiring cells- Carbon dioxide is acidic in solution, so the pH of the blood within the tissues is lowered- The lower pH changes the shape of haemoglobin into one with a lower affinity for oxygen- Haemoglobin releases its oxygen into the respiring tissues
Explain the statement, ‘The more active a tissue, the more oxygen is unloaded’
The higher rate of respiration the more carbon dioxide the tissues produce - the lower pH the greater the haemoglobin shape change the more readily oxygen is unloaded the more oxygen is available for respiration
Why is the loading, transporting and unloading of oxygen important?
This means that there is a flexible way of ensuring that there is always sufficient oxygen for respiring tissues.
Why is the blood returning to the lungs usually only 75% saturated?
In humans, haemoglobin normally becomes saturated with oxygen as it passes through the lungs. In other words, most of the haemoglobin molecules are loaded with their maximum four oxygen molecules. When this haemoglobin reaches a tissue with a low respiratory rate, only one of these molecules will normally be released. The blood returning to the lungs will therefore contain haemoglobin that is still 75% saturated with oxygen.
If a tissue is very active (an exercising muscle) then how many oxygen molecules are usually unloaded from each haemoglobin?
3 oxygen molecules are usually unloaded from each haemoglobin molecules.
What do veins do?
carry blood towards the heart
What do Venules do?
control blood flow from capillaries to veins
What do capillaries do?
Link arterioles to veins
What do Arteries do?
carry blood away from the heart
What do Arterioles do?
control blood flow from arteries to capillaries
Why is the tough layer of blood vessels important?
resist pressure changes from both within and outside
Why is the muscle layer of vessels importan?
contract to control flow of blood
Why is the elastic layer of vessels important?
stretches and recoils, helps to maintain pressure
Why is the lumen of vessels important?
a passage for the blood to travel through
Order of thickness muscle layer of blood vessels (thick to thin)
Ateriole, artery, vein, capillary
Order of thickness of elastic layer of blood vessels (thick to thin)
Artery, arteriole, vein, capillary
Order of lumen size of blood vessels (thick to thin)
Vein, arteriole, artery, capillary
Which blood vessels have high pressure?
Artery
Which blood vessels have valves present?
Vein
The artery elastic layer is much thicker than veins so …
it keeps the blood pressure high, stretching at systole and springing back during diastole
The arteries have no valves but the veins do as …
blood is constantly under high pressure in arteries but much lower pressure in veins so back flow is more likely
Veins have thinner muscle layers as …
they are carrying blood away from tissue therefore construction and dilation does not control flow to tissues
There are spaces between the lining cells of capillaries as …
this gives them an increased rate of diffusion, short diffusion pathway, and an increased surface area/coverage to cells
Why are thick elastic tissue good?
Stretches under pressure, when heart beatsSprings backEvens out pressure/flow
Why are thick muscle tissue good?
Muscle contractsReduces diameter of lumenChanges flow/pressure
Why is a smooth epithelium good in vessels?
Smooth, so reduces friction, lessens possible blood clots, and provides less resistance
What does the SAN do?
sends an electrical wave the septum (base), via the atrium
What is the SAN?
the hearts pace maker, initiates an electrical wave of activity
What is the AVN?
the second node for contraction, initiates an electrical wave down the septum
Atrial systole is a weaker contraction than …
ventricular systole
Equation for cardiac output (with units)
Cardiac output (dm3min-1) = heart rate (bpm) x stroke volume (dm3)
Heart rate is …
how many times the heart beats per minute
Stroke volume is …
volume of blood pumped at each beat
What is a cardiovascular disease?
A degenerative disease of the heart and circulatory system
4 examples of cardiovascular disease
- Strokes- Angina- Heart failure/attacks- Atherosclerosis
A risk factor is …
any characteristic or exposure of an individual that increases the likelihood of developing a disease or injury (not causes)
A correlation is …
a change in one or two variables that is reflected by a change in the other
Are risk factors correlations?
Yes
Name 4 risk factors for cardiovascular disase
SmokingHigh Blood PressureCholesterolDiet/Lifestyle
How is smoking a risk factor for cardiovascular disease?
Smoking cigarettes makes the walls of your arteries sticky from the chemicals, so fatty material can stick to them. If the arteries that carry blood to your heart get damaged and clogged, it can lead to a heart attack. If this happens in the arteries that carry blood to your brain it can lead to a stroke. The build-up of plaque is called atherosclerosis.
How is high blood pressure a risk factor for cardiovascular disease?
If your blood pressure is consistently too high this means that your heart has to work harder to pump blood around your body. It also makes the walls of your arteries less stretchy, causing a build-up of fat which can lead to a heart attack or stroke. The build-up of plaque is called atherosclerosis.
How is cholesterol a risk factor for cardiovascular disease?
Cholesterol joins with proteins to form lipoproteins, non-high density lipoproteins can build up fatty deposits which narrow your arteries, leading to heart attacks or strokes. The build-up of plaque is called atherosclerosis.
How is diet/lifestyle a risk factor for cardiovascular disease?
Eating unhealthy and not exercising can cause high cholesterol and a weak heart, this can lead to a heart attack or stroke. The build-up of plaque is called atherosclerosis.
What is tissue fluid?
a watery liquid that bathes all of the tissues in our body
What does tissue fluid do?
Allows the exchange of substances between the blood and cells
What does tissue fluid contain?
Molecules required:- Glucose, amino acids, fatty acids, ions and oxygenWaste produced:- Carbon dioxide, urea and water
Unlike the blood, what does tissue fluid not contain?
it does not contain large products like red blood cells and plasma proteins
What is the formation of tissue fluid dependent on?
NAME?
What is hydrostatic pressure caused by and what does it do?
.Result of heart pumping.Forces small molecules out.Prevents movement of liquid in
How is tissue fluid formed?
- The hydrostatic pressure is greater than the osmotic pressure (water potential) at the arterial end (where it is narrow), which forces the fluid out of the capillary, along with some molecules, but not large molecules like proteins. This is called ultra-filtration and it lowers the water potential of the capillary. At the venous end (where it is wider), the hydrostatic pressure is lower than the osmotic pressure so fluid moves into the capillary, bringing waste products with it
What is ultra-filtration?
When hydrostatic pressure forces smaller molecules out of the capillaries, but leaves the big molecules there
What is it like at the arteriole end?
.Higher hydrostatic pressure.Lower osmotic pressure.Net loss of water/fluid out.Tissue fluid is formed
What is it like at the venular end?
.Lower hydrostatic pressure.Higher osmotic pressure.Net movement in.Removal of waste
What percentage of tissue fluid returns via the lymphatic system instead of the capillaries?
10%
What is the lymphatic system and what does it do?
- Is separate to the circulatory system- Made up of lymph capillaries- Contains accumulated tissue fluid (lymph)- Drains back into the blood via two ducts that join veins close to the heart
Draw a diagram of the lymphaic system, both
check notes
What is lymph moved by?
- Hydrostatic pressure of the tissue fluid- Contraction of body muscles squeezes lymph vessels
Fluid in the blood is called
plasma
Fluid surrounding the cells is called
tissue fluid
Fluid in the lymphatic system is called
lymph
Define Gene
a short section of DNA that codes for a polypeptide or functional RNA
Define allele
a version of a gene
Define locus
a position on a chromosome
Define homologous
the structural features and pattern of genes are the same
For maternal and paternal chromosomes where are same genes found
in the same positions on the chromosomes
The genetic code is:
- Non overlapping- A triplet code- Universal
What is meant by a triplet code?
every 3 base pairs (nucleotides) codes for 1 amino acid
What is meant by universal?
the code is the same in all species, ATA codes for the same thing in every species
What is meant by non overlapping?
Each base is discrete (123456 is 123, 456 and NOT 123, 234, 345, 456) so that the bases don’t get mixed up when they are being read, meaning the wrong amino acid is formed
How many possible triplet codes are there?
64
How many possible amino acids are there?
20
The genetic code is degenerate, what does this mean?
Some amino acids are coded by more than one triplet, e.g. tyrosine is TAT or TAC
What do some triplet codes act as?
Some triplet codes act as punctuation marksSome indicate start and stop points for start/end of an amino acid chain:- A start codon is ATG
What is transcription?
formation of pre mRNA in the nucleus
What is translation?
formation of polypeptides in the ribosomes
How does transcription work?
.Parental DNA has its hydrogen bonds broken by DNA helicase, leaving a template strand.Free RNA nucleotides are attracted to it and form weak hydrogen bonds with the DNA nucleotides that are complementary to their bases.RNA polymerase comes along and resynthesizes the sugar phosphate backbone along the RNA nucleotides and breaks the hydrogen bonds, making a strand of pre mRNA.The pre mRNA is then spliced, which removes introns and joins together exons, turning into mRNA (no longer pre)
What are introns?
non-coding DNA
What are exons?
coding DNA
What is translation?
The process by which mRNA is used to make a specific protein
Describe how translation happens
Translation is the process by which mRNA is used to make a specific protein, after mRNA has been produced through transcription and splicing it then moves through the cytoplasm to a ribosome and enters between the two sub units and attaches to it. Here a start codon (AUG) tells the ribosome to start reading the RNA on it. Each triplet of bases is called a codon, and after the initial start codon tells the ribosome to read it the ribosome then moves along the mRNA and reads the codons, attaches (with temporary hydrogen bonds) tRNA with a complementary anticodon to the mRNA’s codon. Each tRNA has a specific amino acid attached, as one tRNA binds to the mRNA so does another one next to it, then their amino acids form polypeptide bonds to join them together and the first tRNA leaves and another one joins as the ribosome moves along the mRNA and forms a polypeptide bond in a condensation reaction with the amino acid there. This continues till a stop codon is reached which has no complementary anticodon so the chain stops and the polypeptide chain formed leaves the ribosome and coils up into an amino acid which join using energy from ATP.
What does tRNA do?
.Transport specific amino acids
How many different tRNA’s are there?
20
Do all tRNA’s have the same structure?
Yes
What is a tRNA made up of?
codon, anti codon, hydrogen bonds, ester bonds, amino acids
Describe the structure of tRNA
.Each consists of a single polynucleotide strand of RNA.Folded to form a clover arrangement.Held in place by hydrogen bonds between complementary base pairs.One end acts as an attachment site for the amino acid.The other end is called the anti-codon
What is a mutation?
Any change in one or more nucleotide base or a change in the sequence of the bases in DNA
Characteristic of mutations
.Random.Spontaneous.Natural.Positive or negative
Three types of mutations
.Insertion.Deletion.Substitution
Define insertion
A nucleotide is added to the DNA sequence
Define deletion
A nucleotide is lost from the DNA sequence
Define subsitution
One nucleotide is replaced by another nucleotide with a different base
What is a frame shift?
every amino acid after the insertion or deletion will move one place
What will substitution affect?
Only one triplet code
What will deletion and insertion affect?
the whole amino acid sequence, by causing a frame shift
What is a mutagen?
A physical or chemical agent that changes the genetic material of an organism
What do mutagenic agents do?
increase the frequency of a mutation occurring above the natural
Name 4 things that act as mutagenic agents
Caffeine, x-rays, mustard gas and UV radiation
What are chromosomal mutations?
Changes in the structure or number of whole chromosomes
What are the two types of chromosomal mutations?
.Polyploidy.Nondisjunction
What is polyploidy?
.Changes in whole sets of chromosomes.Cells have multiple sets of chromosomes
What form of polyploidy is very common in plants?
.3n = triploid
What is non-disjunction?
.Homologous pairs fail to separate.Changes in number of individual chromosomes per cell
What is down’s syndrome caused by?
extra chromosome 21
Define meiosis
the process by which a diploid nucleus (2n) divides to produce four haploid daughter nuclei (n)
Name the phases in meiosis
Interphase, prophase I, Metaphase I, Anaphase I, Telophase I, cytokinesis, Prophase II, Metaphase II, Anaphase II, telophase II and cytokinesis
What is a homogolous pair?
one chromatid of mum and one chromatid of dad
What are sister chromatids?
identical chromatids together
What two forms of genetic variation are there?
Crossing over and independent segregation
What is crossing over?
Crossing over is the exchange of alleles
What is independent segregation?
Independent segregation is the random arrangement of chromosomes
State what happens in each phase of meiosis.
Interphase – The cell is synthesising DNA and checking it (2 chromatid per chromosome)Prophase I – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks downMetaphase I – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeresAnaphase I – The pair of chromosomes are split as each is pulled to opposite poles in the cell by the spindle fibres contracting – the homologous chromosomes are separated from each other but the chromosome stays tgtherTelophase I & Cytokinesis – The cells form two nucleus, one for each set of new chromosomes, and pull apart while forming a membrane to produce two daughter cellsProphase II – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks downMetaphase II – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeresAnaphase II – The sister chromatids are split as each chromatid is pulled to opposite poles in the cell by the spindle fibresTelophase II & cytokinesis – The cells form two nucleus, one for each set of new chromatids, and pull apart while forming a membrane to produce two more daughter cells each (4 cells now altogether)
What is a genotype?
The genetic makeup of an organism, the genes and alleles that they have
What is a phenotype?
Observable characteristics, genotype + environment = phenotype
What are the causes of genetic variation?
.Mutations, sexual reproduction, meiosis
How does crossing over work?
Homologous pairs line up, chromatids of each pair become twisted, section of chromatid breaks off and re-joins chromatid of the other homologous chromosome, sections have different alleles, new combination of linked alleles
With crossing over, what happends to the amount of possible versions of allele combinations?
No crossing over = 2 versionsWith crossing over = 4 possible versions
Who discovered independent segregation? When?
.Gregor Mendel (19th Century)
What is independent segregation?
the random segregation of chromosomes during anaphase
What did Gregor Mendel say about independent segregation?
.Genes are inherited independently of one another.BUT genes close together have a high likelihood of being inherited together
Independent segregation key points
.Homologous pairs line up along the equator randomly.Combination of chromosomes pulled to each pole is random.Daughter cells produced are genetically different
The formula for the number of combinations of genes after independent segregation
2^n
The formula for the number of combinations of genes after fertilisation after independent segregation
(2^n)^2
Why does the formula (2^n)^2 not work for crossing over?
Crossing over is completely random
What is the ‘n’ in the formula (2^n)^2?
number of chromosomes
What is the first ‘2’ in the formula (2^n)^2?
possible number of routes the chromosomes could go to (pulled to two poles)
What does RNA stand for?
Ribonucleic Acid
What is RNA made of?
A polymer of nucleotides
Nucleotide composition in RNA
.Phosphate .Nitrogenous Base .Pentose sugar (ribose sugar)
RNA size in comparison to DNA
Shorter
What are the 4 bases in RNA
A, U, C and G – Uracil replaces Thymine
Sugar present in DNA
Deoxyribose (pentose sugar)
Sugar present in RNA
Ribose (pentose sugar)
Structure of DNA
DOuble helix
Structure of RNA
Single strand
Base pairing in DNA
A to T, C to G
Base pairing in RNA
A to U, C to G
Length of DNA
Long as two times the bases in RNA
Length of RNA
Short, less bases than DNA
Is DNA and RNA a polymer or monomer?
Both polymers of nucleotides
What type of base pairing is in DNA??
Complementary
Type of base pairing in RNA
No base pairing
Can you predict the percentage of other bases from one base percentage in DNA?
Yes
Can you predict the percentage of other bases from one base percentage in RNA?
No
Name the 3 types of RNA
mRNArRNAtRNA
What is mRNA?
messenger RNA, copies of the DNA sequence which leaves the nucleus through membrane pores and give instructions to the ribosomes to make proteins
What is rRNA?
ribosomal RNA, combines with protein to make up the ribosomes structure
What is tRNA?
transfer RNA, carries specific amino acids during the process of protein synthesis (called translation)
How do all the RNA’s work together in protein synthesis?
.The mRNA gives the instructions to make the proteins and brings it to the ribosome, the rRNA makes up the ribosome to make the protein and the tRNA reads the mRNA and interact to make the protein
What is DNA replication vital for?
.Growth .Development/specialisation.Reproduction
What are the 3 proposed methods of DNA replication?
Conservative replicationDispersive replicationSemi-conservative replication
What is conservative replication?
.One DNA molecule contains both parental DNA strands.The other molecule contains only newly-synthesised DNA
What is dispersive replication?
.Parental DNA is interspersed between the two molecules.Both new strands have some new and some original DNA
What is semi-conservative replication?
.BOTH DNA double helices, consist of one parental and one new DNA strand
What are the 5 key requirements of semi-conservative replication?
.DNA template.Free nucleotides.DNA helicase.DNA polymerase.Energy
Describe the process of semi-conservative replication (6 marks)
The parental DNA is gets broken apart by the enzyme DNA helicase V, which breaks the hydrogen bonds between bases. These open bases attract free nucleotides V which come and loosely attach to the complementary bases (A to T and C to G) on the original (template V) strand of parental DNA. Hydrogen bonds V form between the nitrogenous bases. DNA polymerase V helps form the sugar-phosphate backbone of the DNA which gives the new strand structure and support, it holds it in place. This has now formed a daughter DNA’s double helix. V 6/6
