organisation

• Protease


  Proteases are digestive enzymes that break down proteins into amino acids.

  Proteins are digested in the stomach by pepsin and in the small intestine by other proteases.

  Proteases are produced in the stomach, pancreas and small intestine.
• Structure of an enzyme

  Enzymes are made up of long chains of amino acids that are folded into specific shapes. They have a very specifically shaped active site which has a complementary to the substrate that the enzyme acts on
• Lock and key theory

  All enzymes have an active site which is where it can bind to a substrate(substance involved in the reaction).

  Enzymes and their active sites have very specific shapes. The specific shape of each active site means only certain substrates can bind to it and form enzyme-substrate complexes. This means each enzyme can only catalyse one specific type of reaction and therefore produce the products.

  The 'lock and key' model is a simplified version of how enzymes work. It states that the active site of an enzyme fits the substrate perfectly like a lock and a key, they are complementary.
• Amylase


  Amylase is a carbohydrase that breaks down starch into maltose (comprised of two glucose molecules).

  Amylase digests starch in the mouth and small intestine. It is produced in the salivary glands, pancreas and small intestine.
• Bile


  Bile is produced by the liver, stored in the gall bladder and then released into the small intestine. It has 2 uses:

  It is an alkaline substance so neutraliseshydrochloric acid from the stomach. This creates better conditions for enzymes in the small intestine so they can digest food efficiently.

  Bile also emulsifies fats which means it breaks them into small droplets. This gives them a greater surface area for lipases to work on, making digestion faster.
• Lipase


  Lipases are digestive enzymes that break down lipid molecules into glycerol and fatty acids, in the small intestine. They are made in the pancreas and small intestine.
• Digestion as a whole

  Food enters the body in the mouth. Mechanical digestion occurs by the teethwhich breaks it into small pieces. Amylase in the saliva is secreted into the mouth by the salivary glands to start breaking down starchfrom the food into maltose. It then is sent down the oesophagus to the stomach.

  The stomach churns and pummels the food and digests proteins with the pepsin. Pepsin requires acidic conditions in order to work so the stomach is full of hydrochloric acid which makes the stomach approximately pH22 . The hydrochloric acid also kills most of the bacteria in the food.

  The food is then sent to the small intestinewhere bile and enzymes are released:

  Bile is made in the liver, stored in the gall bladder and released into the small intestine. It neutralises the acid from the stomach to create a pH suitable for the enzymes of the small intestine and emulsifies fats so they can be more easily digested by lipase enzymes.

  Lots of digestive enzymes are made in the pancreas and then released into the small intestine. Amylase digests starch into maltose, protease digests proteins into amino acids and lipase digests lipids into fatty acids and glycerol.

  Food molecules are now much smaller so can be absorbed through specialised intestinal walls and into the bloodstream.

  Food passes through the large intestinewhere excess water is absorbed from the food. It is finally stored in the rectum as faeces and excreted from the body through the anus.
• digestive system


  Breaks down food into absorbable units that enter the blood for distribution to body cells.
• Function of lungs


  The lungs are responsible for taking in oxygen from the air so it can be carried by the blood to cells that require it for aerobic respiration. They also remove carbon dioxide from the blood and send it back out into the air.
• Adaptations of alveoli


  They provide a massive surface areafor the exchange of gases.

  They have a moist lining for dissolving gases.

  They have very thin walls so a short diffusion distance.

  They have a good blood supply to maintain the concentration gradient.
• The Whole Respiratory System(simple)

  Air enters the body through the mouth and nose and travels down the trachea to the lungs. The trachea splits into two bronchi that go into each lung. Each bronchus branches out into bronchioles that end in little air sacs called alveoli. Alveoli are the exchange surface for gases in and out of the body.

  The lungs are located in the thorax, separated from the rest of the body by the diaphragm. They are surrounded by pleural membranes and encased in the rib cage with the heart for protection. The contraction and relaxation of the intercostal muscles and the diaphragm causes ventilation.
• Inhalation


  The external intercostal muscles contract pulling the rib cage up and out.

  The diaphragm contracts and flattens.

  This increases the volume and decreases the pressure of the thorax.

  Air is therefore drawn into the body.
• Exhalation


  The external intercostal muscles relax pulling the rib cage down and in.

  The diaphragm relaxes and moves upwards.

  This decreases the volume and increases the pressure of the thorax.

  Air is therefore expelled from body.
• gas exchange in alveoli

  Deoxygenated blood is pumped to the the lungs to be oxygenated, by the heart. It contains lots of carbon dioxide and very little oxygen because it has been supplying oxygen to respiring cells around the body and receiving their waste carbon dioxide.

  The alveoli contains air that has a high concentration of oxygen and a low concentration of carbon dioxide. Oxygen will therefore diffuse into the blood and carbon dioxide will diffuse out of the blood, down the concentration gradients.

  Now the blood is oxygenated, it returns to the heart so it can be pumped around the body to respiring cells.
• Double circulatory system


  Humans have a double circulatory system which means it is made up of two loops that are joined together.

  The heart pumps deoxygenated blood to the lungs to be oxygenated and then it returns to the heart.

  The heart then pumps the oxygenated blood around the rest of the body, to supply respiring cells with everything they need, before returning again when deoxygenated.

  Blood is transported round the circulatory system by different types of blood vessels that are all adapted for their functions.
• Arteries


  Arteries carry blood away from the heart and branch off into capillaries.

  They have thick walls made up of elastic fibres and smooth muscle and a relatively narrow lumen.

  The elastic fibres relax when the heart pumps blood, allowing the artery to expandand blood to flow through at high pressures. The elastic fibres contract when the heart is not pumping blood to narrow the lumen of the artery and maintain the high blood pressure.
• Vein


  Veins take blood from capillaries back to the heart.

  This blood is under low pressure so the walls of veins are not as thick as the walls of arteries.

  They have a large lumen to allow the blood to flow despite the low pressure and valves which help to keep the blood flowing in the right direction (prevent backflow).
• Capilaries


  Capillaries are tiny vessels that surround cells and enable them to exchangedifferent substances with the blood.

  They supply the cells with oxygen and glucose for respiration and remove waste products such as carbon dioxide and urea.

  Their permeable walls are only one cell thick which provides a short distance for diffusion between the blood and the cells and therefore increases the rate of diffusion.

  very small lumen

  carry blood between arteries and veins
• Function of heart(full)


  The heart has a left side and a right side, divided by the septum. Each side of the heart is split into an atrium and a ventricle.

  Blood flows in very specific directions through the heart to ensure deoxygenated blood is sent to the lungs and oxygenated blood is sent around the body. The heart has valves that prevent blood flowing backwards, just like veins.

  Deoxygenated blood from the body enters the right atrium through thevena cava.

  The atria contract pushing the deoxygenated blood to the right ventricle.

  The ventricles contract pushing the deoxygenated blood through the pulmonary artery to the lungs to be oxygenated.

  Oxygenated blood from the lungs enters the left atrium through the pulmonary vein.

  The atria contract pushing the oxygenated blood to the left ventricle.

  The ventricles contract pushing the oxygenated blood through the aorta to the rest of the body, to supply respiring cells with oxygen.
• Red blood cell


  Red blood cells carry oxygen from the lungs to cells around the body for aerobic respiration.

  They contain a protein called haemoglobinwhich binds to the oxygen to form oxyhaemoglobin. When arriving at a cell that requires oxygen, oxyhaemoglobin splits back into haemoglobin and oxygen so the oxygen can diffuse into the cell.

  Red blood cells are adapted for efficient gas exchange because:

  - They have a biconcave shape which increases the surface area for increased diffusion.

  - They are really small so can fit through small capillaries.

  - They have no nucleus to make room for lots of haemoglobin.

  - They have lots of haemoglobin to bind and carry lots of oxygen.
• White blood cell


  White blood cells are an important part of the immune system as they are responsible for identifying and destroying pathogens. They do contain a nucleus.

  There are two different types of white blood cell:

  Phagocytes engulf and digest pathogens through phagocytosis.

  Lymphocytes identify pathogens and produce antibodies that bind to the antigens on pathogens and cause them to clump together. This makes them easier to be engulfed by phagocytes. Some lymphocytes also release antitoxins that neutralise toxic substances produced by pathogens.
• Plasma


  Plasma is a pale yellow liquid that transports everything in the blood:

  Red blood cells, white blood cells and platelets.

  Products from digestion of food such as glucose and amino acids.

  Waste products such as carbon dioxide and urea.

  Hormones, proteins, antibodies and antitoxins.
• Platelets


  Platelets are fragments of cells produced in the bone marrow that cause the blood to clot. They do not have a nucleus.

  They are particularly important when the organism has a wound as they stop blood from flowing out of the body and stop pathogens getting into the body.

  They do this by forming blood clots and scabs.

  People who have few platelets are prone to excessive bleeding and bruising.
• Coronary heart disease


  Coronary heart disease (CHD) is when the coronary arteries get blocked by layers of fatty build up (made from 'bad' LDL cholesterol), narrowing the lumen of the vessel. This restricts the flow of blood, limits the amount of oxygen reaching the cells and can ultimately cause a heart attack.
• coronary arteries


  The heart has a network of vessels called the coronary arteries that supply the cells of the heart with everything they need, such as oxygen. The muscle cells of the heart use oxygen in respiration to produce the energyrequired for muscle contraction and therefore keep the heart beating.
• Stents(full)


  Stents are tubes that are inserted into peoples arteries and used to treat people with coronary heart disease. The stents hold the arteries open, allowing blood to flow through and access respiring muscle cells.

  Stents reduce the risk of patients with the disease having a heart attack and remain effective for a long time. The recovery time for the operation is relatively small but the surgery itself comes with risk of complications and infections. There is also an additional risk of blood clots called thrombosis near the stent.
• Statins


  Statins are drugs that reduce the amount of 'bad' or LDL cholesterol in the blood. This prevents fatty deposits forming and stops vessels getting blocked.

  Statins reduce the risk of strokes, coronary heart disease and heart attacks and increase the levels of 'good' or HDL cholesterol in the blood. However:

  The patient must remember to take the drug regularly in order for them to be effective and there is a risk that they could be forgotten.

  They can cause various side effects such as headaches, joint pain and kidney problems.

  They do not take effect immediately.
• Faulty Heart Valves


  Some people have faulty heart valves. This could mean the valve is leaky and blood flows where it shouldn't or the valve is stiff and amount of blood that gets pumped is reduced.

  People with severely faulty heart valves can have their valves replaced with either biological valves from other humans and mammals or man-made mechanical valves.

  Valve replacement is a safer surgery than a whole heart transplant but there is a risk of problems with blood clotting.
• heart failure


  In the case of heart failure, the patient can be treated by a whole heart transplant (or heart and lungs if they are both diseased).

  The transplanted organs usually come from a recently deceased donor. There is a high demand for transplants and they are only available after people have died so there are often very long waiting lists. While patients are waiting, artificial hearts can be used to keep the patients alive. Artificial hearts can also be used to give the heart a rest and therefore aid in its recovery.

  Artificial hearts are manufactured so patients don't have to wait for someone to die for one to become available and there is less chance of the body rejecting it as it is made of metals and plastics (the body will not recognise it as foreign).

  However, they do not work as well as real hearts and parts wear out more easily. There is also an increased chance of blood clots and therefore strokes in an artificial heart as the blood doesn't flow through as easily. To aid the flow of blood, patients must take blood thinning drugs but this can cause serious problems if they are accidently hurt.
• health


  Health is the state of physical and mental well-being and can be affected by a number of factors:

  Disease is the main cause of ill health and can be communicable or non-communicable.

  A healthy balanced diet is essential in order to supply the body with the correct amounts of nutrients. Poor diets can impact both physical and mental health.

  Prolonged, high levels of stress can lead to health issues, e.g. cardiovascular diseases and mental health issues.

  Life situation has a major impact on health. People who do not have access to medicines, vaccines, food, clean water and other supplies are more at risk of getting certain diseases and may have impacts on their mental health, e.g. having access to condoms reduces the risk of getting a sexually transmitted disease.
• Non communicable full


  Non-communicable diseases are those that are unable to spread between organisms. They are not caused by pathogens, are usually long-lasting and often get worse over time. Some examples are asthma, cancer and coronary heart disease.

  There are many human and financial costs of non-communicable diseases:

  Poor quality of life, reduced lifespan and death.

  Emotional impacts on family and friends.

  Financial cost of healthcare, research and treatments. This cost may be covered by a healthcare provider (in the UK it is paid by the NHS) or attributed to the individual.

  Further financial costs if families have to move or adapt their home to better fulfil the patients needs and cost of frequent travel to the hospital.
• Risk factor


  Risk factors increase the chances of an organism getting a particular disease. They can be a certain aspect of a person's life, such as amount of regular exercise or diet, or the presence of a certain substance in the environment or body, such as air pollution.

  You cannot assume that a risk factor has caused a disease just because there is a correlation. Scientists must investigate the mechanism behind the causation in order to come to a decisive conclusion.

  Scientists have concluded that:

  Smoking, poor diet and lack of regular exercise all increase the likelihood of a person developing cardiovascular disease.

  Obesity is a risk factor for type 2 diabetes.

  Consuming large amounts of alcohol increases the risk of liver disease and impaired brain function.

  Smoking increases the probability of developing lung disease or lung cancer.

  Smoking and drinking alcohol when pregnant affects the development of foetuses.

  Exposure to carcinogens, such as x-rays, increases the risk of cancer.

  Many diseases are caused by a combination of different factors.

  The incidence (number of cases) of non-communicable diseases varies with location due to access to different foods, alcohol and cigarettes. On a global level, people in developed countries have money to buy foods that are high in fat which increases their risk of developing cardiovascular diseases. Nationally, people from deprived areas are more likely to smoke, have poor diet andexercise less which increases the incidence of cardiovascular diseases and type 2 diabetes.
• Sampling


  Sampling allows scientists to study potential risk factors for a disease in a population without investigating every individual person. They may do this using medical records or carrying out surveys.

  Samples must be representative of the whole population being studied. To achieve this, the study should cover all groups within the population and must be random within the groups.

  It is also important to take into account other factors such as variations between people of different ages, genders and lifestyles. Separate analysis of sub-sets of data can be performed to investigate the effect of these factors and data can be adjusted to allow better comparisons between groups.

  Samples may be taken at regular time intervals.
• Principles of organisation


  Cells are the basic building blocks of all living organisms.

  A tissue is a group of cells with a similar structure and function.

  Organs are aggregations of tissues performing specific functions.

  Organs are organised into organ systems, which work together to form organisms.
• Growth of tumours


  Cell division by mitosis is controlled by many different genes to produce the correct amount of cells needed by the body.

  Changes to the DNA of cells may mean that genes can no longer regulate mitosis and therefore cells grow and divide uncontrollably, forming tumours.
• Cancer


  any malignant growth or tumor caused by abnormal and uncontrolled cell division
• Malignant tumour


  Malignant tumours are cancerous. They can spread to neighbouring healthy tissues or break off and travel in the blood and lymphatic system to other parts of the body. The spreading of the cancerous cells cause secondary tumours to form in different places. Cancers disrupt the functioning of healthy organs and therefore can be fatal.
• Benign tumour


  Benign tumours usually stay in one place in the body, within a membrane. They therefore do not invade other tissues and are most often harmless.
• Risk factor for cancer

  Obesity has been linked to bowel, liver and kidney cancer.

  Smoking has been linked to lung, mouth, throat, bowel, stomach and cervical cancer.

  Exposure to UV (from the sun and tanning beds) increases the risk of skin cancer.

  Viral infections can trigger the formation of certain cancers e.g. cervical cancer from HPV virus and liver cancer from hepatitis B and C.

  Sometimes faulty genes can be inherited that increase the likelihood of an individual developing certain cancers, e.g. breast and ovarian cancer from faulty BRCA genes.

  Cancers can develop in anyone, in any part of the body, at any time. However, the risk of cancer can be reduced by limiting the amount of risk factors, e.g. eating a balanced diet, exercising, not smoking, limiting time in direct sunlight.
• Structures of leaves and plant tissues

  Leaves are plant organs responsible for the majority of photosynthesis and gas exchange. The structuring of the different tissues in a leaf mean they are adapted for these functions.

  The epidermal tissues are found on the top and bottom of the leaf. They are covered with a waxy cuticle to prevent water loss from the leaf by evaporation. The upper epidermis is transparent and very thin to allow light to pass through into the palisade layer (where the majority of photosynthesis takes place). The lower epidermis is full of little holes called stomata that allow gases to diffuse in and out of the cell. Guard cellsopen and close the stomata in response to environmental conditions.

  The palisade mesophyll tissue is near the top of the leaf and has lots of chloroplasts so is able to absorb lots of light for photosynthesis.

  The spongy mesophyll tissue has lots of air spaces which provide space for gases to diffuse in and out of the cell.

  The xylem and phloem tissues supply the leaf with water and nutrientsrequired by the cells and remove glucose produced by the leaf in photosynthesis.