- Malnutrition is when someone does not get a balanced diet - leads to obesity or deficiencies.
- Obesity causes Type 2 Diabetes where body stops regulating sugar in blood, because of little insulin.
- Carbohydrates: made up of simple sugars (glucose). Needed to release energy through respiration. In respiration: glucose + oxygen ==> carbon dioxide + water.
- Fats: made up of glycerol and fatty acids. Used as an energy store and insulator.
- Proteins: made up of amino acids. Needed for growth and repair.
- Unit for energy is kJ (kilojoules).
- Vegetarians take legumes or pulses in place of meat for a source of protein.
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- Metabolic rate: rate at which chemical reactions happen in cells.
- Basal metabolic rate is inherited metabolic rate.
- During exercise your body works harder so more energy is needed. Long period of regular exercising means that overall metabolic rate increases, more muscle tissue which is more efficient when using energy. Healthier, less likely to get heart disease.
- To lose mass, energy input should be lower than energy output.
- Cholesterol made in liver can cause fatty deposits, but this can be reduced by exercising and eating healthily.
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- Pathogens are microbes that cause infections.
- There are many methods of defence in order for us to be safe from these pahogens.
- These defences are divided into physical barriers and chemical barriers.
- An example of a physical barrier is the skin, a tough layer that stops pathogens from being able to enter the body in the first place.
- However, when there is a cut in the skin, pathogens are able to enter, as well as being able to enter through the mouth, nose or ears.
- To counter this, the nose has mucus or nose hair to trap the pathogens, while the ears have ear wax, also to trap the pathogens.
- An example of a chemical barrier is hydrochloric acid in the stomach, which is too acidic for pathogens to survive in.
- In the eyes, there are chemicals called lysozymes which can attack pathogens.
- White blood cells are effective when the pathogen has somehow managed to get into the body, and there are three ways that white blood cells can combat pathogens:
- Some white blood cells ingest pathogens, then destroy them
- Some produce antibodies, that are designed to stick onto a specific pathogen, then kill it.
- Others produce antitoxins, that can neutralise toxins released by a pathogen, which can otherwise make us feel very ill.
- Although painkillers can reduce the symptoms caused by pathogens, they cannot kill them.
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The Immune System
- All cells in our body are covered in something called antigens, which help the white blood cells identify our cells as our own, and prevent the white blood cells from accidentally attacking the body's cells.
- Pathogens are also covered in antigens, but they have different antigens to the body, meaning it is easy for the white blood cells to identify a foreign body and remove the foreign body. When this happens, antibodies are created that can fit around the antigens of the pathogens to kill them.
- During the first time, this process takes time, so the person may still be feeling ill.
- Antigens work in three ways:
- Some make pathogens stick together so it is hard for them to move and can be easily engulfed by another white blood cell.
- Some directly kill the pathogen.
- Some make the pathogen more obvious for other white blood cells to kill it.
- Once the antibody has been made once, the white bloods that made them can make a memory cell that remembers the antibody needed to kill the pathogen. This means that if the pathogen enters the body again, the white blood cells can make antibodies much faster, so we do not realise we are ill.
- This is called the immune response. Some pathogens, like the common cold, are able to change their antigen, so we can catch it many times.
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- Overuse of antibiotics, drugs used to treat bacterial infections, means that some strains of bacteria have become resistant to the antibiotic, and can no longer be killed by the antibiotic
- An example is the MRSA bacterium, which is resistant to most antibiotics.
- When bacteria multiply, there are often slight variations because there may be genetic mutations due to incorrect copying of cells.
- Often, these mutations make no difference to the bacterium, or it gets killed.
- Sometimes, these mutations mean that a strain of bacteria has gained a characteristic in order to be able to survive an antibiotic. It has become resistant to the antibiotic.
- When the antibiotic is not being used, this is of no advantage to the bacterium, and may die of its own.
- However, when the antibiotic the strain of bacteria is resistant to is used, the strain is more likely to multiply when other bacteria that are not resistant to the antibiotic are killed.
- Mutations could also result in new strains of dieases that can spread quickly and result in more dieases because no one is resistant to this new disease. This could result in an epidemic (in one country) or a pandemic (more than one country).
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- Examples of vaccines include MMR, which is a vaccine for immunity against measles, mumps and rubella.
- Vaccines contain dead or inactive forms of the pathogen that we want to be immune to.
- When this vaccine is injected into our body, lymphocytes, a special type of white blood cells immediately detect the foreign bodies and start to come up with the right shape of antibody that will bind to the antigen on the pathogen.
- Because the pathogen is dead or weakened, it is very rare that we get ill from this injection.
- Once the lymphocytes have produced the right antibody, they can kill the pathogens.
- Memory cells are also produced, which remember the antibody needed to bind to the antigen on the pathogen.
- When we are infected by the actual pathogen again, the lymphocytes are able to quickly find the right shape of antibody to kill the pathogen, so we do not even realise that we have been infected.
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- In order to culture bacteria, it is necessary that we provide it everything it needs to live. We usually give them a liquid or gel of some kind containing these nutrients, called a culture medium.
- The culture medium contains carboydrates, minerals, and sometimes other chemicals. These are all usually added to agar jelly that sets at room temperature.
- Bacteria are often cultured in petri dishes, which are usually sterilised beforehand, as well as any other equipment used to culture the bacteria, using an overn called an autoclave or using gamma rays.
- Aseptic technique is processes and techniques used by microbiologists to try and minimise the amount of contamination done by bacteria.
- An inoculation loop is used to inoculate or streak the agar jelly with bacteria.
- The inoculation loop is first heated to sterilise it, then dipped into a suspension of the bacteria. It is then used to streak the bacteria across the agar jelly, and the petri dish lid is promptly closed then sealed to minimise contamination.
- The sealed petri dish is incubated , or kept warm, for a few days to let the bacteria grow into a colony that we can see.
- The maximum temperature to be used in schools and colleges is 25°C, because using a higher temperature increases the risk of growth of more dangerous pathogens.
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