1. Most organisms are active in a limited temperature range
1.1 Identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity on substrates
Definition: Enzyme is a chemical that controls the rate of a specific cell reaction without itself being altered by the reaction (biological catalyst)
Structure/chemical composition: made of protein (long chains of amino acids) proteins which are coiled up and held together in a 3D shape by cross linking. The enzyme contains active sites which is where the substrate attaches. Enzymes are sensitive to temperature and to pH.
Role of enzymes in metabolism:
• Acceleration of chemical reactions: enzyme catalysts are able to speed up (or slow down) reactions without a change in temperature. This is important in cells as heat damages living tissue. Activation energy is needed for a chemical reaction to begun. The role of the enzyme is to lower the activation energy needed to start a reaction, so that the reaction can proceed quickly, without a change in temperature
• Lowering of activation energy: In the non-living world heat provides activation energy, but in the body hear burns tissue. Enzymes do NOT PROVIDE activation energy but REDUCE the amount needed. It does this by bringing specific molecules together, rather than relying on them colliding randomly.
• Action of specific substrates: Enzymes are therefore substrate specific, meaning that one particular enzyme can work on only one particular substrate molecule. The enzyme itself is not chemically changed in the reaction and so it can be reused in subsequent reactions. Enzyme controlled reactions are always reversible.
Simple model: Lock and Key
• The key represents the enzyme and the lock represents the substrate
• It shows that enzymes are specific: each lock has its own key and the key can only open one specific lock
• It shows that enzymes are re-usable: the key can be used over and over again
• It shows that enzymes cause changes but are not changed themselves in the reaction: a key causes a change in the lock but is not changed itself
- Limitations: keys are smaller than locks but enzymes are larger than the substrate molecule. Keys are not generally affected by temperature and enzymes are: when enzymes are cooled they act slower. It they are heated back to normal they are fine. When they are heated above optimum they are denatured. If pH is high or low the enzymes denature, normal pH is fine.
2. Plants and animals transport dissolved nutrients and gases in a fluid medium
2.C Analyse information from secondary sources to identify current technologies that allow measurement of oxygen saturation and carbon dioxide concentrations in blood and describe and explain the conditions under which these technologies are used
Arterial blood gas analysis (ABG’s): Is a blood test which measures oxygen, carbon dioxide and pH using blood drawn from an artery and run through a blood gas analyser.
Can be used to:
– Test lung functioning. Test is the lungs are working properly. Assess how well the lungs can oxygenate the blood. If the level of O2 is too low then appropriate oxygen therapy is given.
– Test acid base balance (pH) eg gives information on how well the kidneys are functioning. A major alteration in the level of pH can be fatal.
– Test level of carbon dioxide. This measures the body’s ability to excrete the metabolic by-product CO2. This is a respiratory function of the lung. A high level of CO2 may suggest a problem with lung ventilation (could require mechanical ventilation). A low level of CO2 may suggest a metabolic problem.
– Diagnosis: lung diseases such as emphysema and lung cancer
– Treatment: oxygen level can be monitored, treatment can commence if the level is not too low
– Monitoring: can be used to follow the complex course of critically ill patients (eg intensive care patients)
– It’s a snap shot in time, not continuous
– Cannot measure pulse
Pulse Oximeter: a peg like monitor attached to the finger to detect low oxygen levels by passing light through haemoglobin
Monitors the percentage of haemoglobin (Hb) which is saturated with oxygen
Probe can be attached to patients finger or in some cases ear lobe. This is linked to a computerised unit which displays:
– the percentage of Hb saturated with oxygen
– an audible signal for each pulse beat
– calculated heart rate
– Graphical display of the blood flow past the probe ( in some models)
– Audible alarms can be programed
How it works
– Haemoglobin with oxygen is a different colour (red) than haemoglobin without oxygen (blue). The probe can detect these different colours through the finger nail and calculate the proportion of haemoglobin which is oxygenated.
Can be used to:
– Monitor oxygenation and pulse rates during anaesthesia
– Monitor during recovery
– Monitor those with respiratory diseases or congenital heart diseases (may have lower readings)
– Low readings can detect the severity of an underlying disease
– Monitor intensive care patients especially during mechanical ventilation
– Assess whether a patients oxygen therapy is adequate
– Used in casualty departments eg for asthma
– When patients are sedated for procedures such as endoscopy, oximetry can increase safety by alerting the staff to unexpected problems with oxygen levels.
– Also used to monitor snorers in sleep clinics
– Non-invasive, no needles needed
– Continuous reading
– Can measure pulse rate
– Only detects O2
– Does not detect CO2, therefore can not assess patients who are developing respiratory failure due to CO2 retention
– Needs good blood flow to work properly
2D Analyse information from secondary sources to identify the products extracted from donated blood and discuss the uses of these products
Secondary source: Australian Red Cross Blood Service website
• Unless whole blood is urgently needed, a blood donation is separated into its components. This way it is possible to use a single donation to treat several patients suffering from different illnesses
• Blood components have a short shelf life:
-Platelets: up to 5 days
-Red cells: 42 days
-Plasma: up to 1day
20 different products eg:
∗ Red cell concentrates: ideal for treatment of anaemia and bleeding after trauma or surgery. Most widely used blood component. Those who need transfusions are usually in need of oxygen carrying capacity of the red cells
∗ Platelet concentrates: used for control of haemorages, often in children with leukaemia. Used to control bleeding due to platelet deficiencies or problems with platelet function.
∗ Anti D: prevents Rhesus disease in newborns. Incompatibility of the mother’s and baby’s blood resulting in the mother developing antibodies against her baby’s blood.
∗ Factor VIII: (Anti-haemophilic factor) for management of haemophilia (any of several hereditary illnesses that impair the body’s ability to control bleeding, usually passed from mother to son)
2E Analyse and present information from secondary courses to report on progress in the production of artificial blood and use available evidence to propose reasons why such research is needed
Concentrated efforts to develop blood substitutes for public use only began seriously in 1986 as a response to concerns about HIV
Why is development needed? (what are the advantages?)
• There is a world wide shortage of blood (not as important, must remember other reasons)
• It can be made disease free eg by filtering, pasteurising and chemically cleansing
• It doesn’t need type matching. Whole donated blood causes an antibody/antigen reaction if the wrong type is given, artificial blood can go into anyone quickly
• It can be stored at room temperature. This will make it easier to be used everywhere eg war zones
• It would have a longer shelf life
What stage has the development of artificial blood reached?
• Products are not in general use, they are being trailed. Not perfected yet.
• The only functions of blood that are currently carried out by artificial blood are to carry oxygen and carbon dioxide.
• There are three types of blood products that have been designed to carry oxygen:
1. Perfluorochemicals: synthetic fluids in which oxygen can dissolve. Advantages: cheaply produced in large amounts, can carry 50 times the amount of oxygen than blood plasma. Disadvantages: carries much less oxygen than haemoglobin, don’t flow as well through blood vessels.
2. Modified haemoglobin: modified by either chemically cross-linking or genetically engineering. Advantages: are stable and do not break down into toxic substances like free haemoglobin does. (had to be more stable than free haemoglobin, so they used the cross linking etc). Disadvantages: lasts in circulation for 20-30hrs (normal red blood cells last 100 days)
- Encapsulated haemoglobin: haemoglobin in encapsulated in an artificial cell membrane made of lipids. This protects the haemoglobin from being broken down and increases circulation time. It must be put in a membrane because if its free is breaks down into toxic chemicals.
2.3 Compare the structure of arteries, capillaries and veins in relation to their function
• Arteries break into capillaries in various organs and these rejoin to form veins
• Very small (microscopic)
• Walls only 1 cell thick
• Semi permeable to blood contents. Plasma together with all its solutes (food, hormones, oxygen) can pass through. Red blood cells and large plasma proteins cannot. Some white blood cells can wriggle between cells in capillary walls.
• They allow for exchange of substances from cells to blood eg O2 to cells, nutrients to cells, CO2 away from cells.
- There are so many of them because every cell must be near a capillary
3.3 Identify the role of the kidney in the excretory system of fish and mammals
Mammals: The mammalian kidney is made of millions of functional units called nephrons.
3.7 Outline the role of the hormones, aldosterone and ADH (anti-diuretic hormone) in the regulation of water and salt levels in blood
• Produced by the hypothalamus
• Stored in the pituitary gland
• Released into the blood stream if the water content of the blood begins to fall below normal and the organism is in danger of dehydration
• Carried in the blood to the distal kidney tubule and the collecting tube
• Causes the re-absorption of additional water from the filtrate by making kidney tubules more permeable to water
• Once normal water levels have been restored a negative feedback system causes the production of ADH to cease.
- Hypothalamus sends a message of thirst to the brain so the person will drink water when the water levels in the blood begin to drop
• Ankles and feet swollen
• High protein in urine
• High cholesterol
• Limited fluid intake
• Elastic stockings
• Decreased sodium intake
• Medicine increases the production of urine
• Strict diet
• Fluid balance
• No urine produced, never urinate again until kidney transplant
• Dialysis removes the build up of urea and water because the kidney does not get rid of it during urination
• If you don’t have dialysis you die within a few days
• The other was is not as efficient, uses the intestines as semi permeable membrane
• The veins get scarred and there is no access point and the can no longer do dialysis.
• Can change the composition of the dialysis fluid depending on the person.
• Portable machines, can have one at home, normally people go to day clinics
Composition of the fluid: we want glucose and amino acids to say the same, fluid around the blood has the same composition (normal glucose and aa level) want no urea in the blood. Replenish, concentration gradient is getting less, balance in regards to water and salt in the fluid, by the end the excess water and salts go out
Aim of dialysis:
• To remove urea from blood
• To balance water and salts
• To maintain glucose and amino acid levels
• Dialysis solution must contain sufficient glucose and amino acids to stop these diffusing out of the blood
• It has the correct amount of all the salts and water to correct fluid balance. Water moves into fluid by osmosis
• Urea diffuses into dialysis is fluid
• Drugs can also be added to solution and will diffuse into blood
Comparing renal dialysis with normal kidney function
3.C present information to outline the general use of hormone replacement therapy in people who cannot secrete aldosterone
• Caused by aldosterone deficiency
• Causes increased sodium loss
• Decreased water re-absorption decreased blood volume = low blood pressure = fainting, cardiac failure, shock and death
• Hormone replacement therapy
• With aldosterone replacement with various corticosteroid (drug that mimics the action of aldosterone)
• Eg Florine f (brand name)