Biology B1.1JaskiratK

Keeping Healthy

Regular exercise and a balanced diet are needed to keep the body healthy. Too little food leads to a person being underweight and prone to certain types of illness, while too much food and not enough exercise leads to a person being overweight and other types of ill health.

Diet & Exercise

Nutrients:A mixture of different types of food in the correct amounts is needed to maintain health. The main food groups are:

The Main Food Groups:

Food Group Found In… Needed By Our Bodies For:

Carbohydrates - Potatoes - Pasta- Bread - Bananas

- Sugar - Rice

A Source Of Energy For Other Life Processes. Referred To As Fibre ~ Very

Common Type Of Carbohydrate.

Fats - Cheese - Butter- Margarine - Oils

A Source Of Energy For Life Processes: Fats Also Make Cell Membranes & To Insulate

Our Bodies. Contains Fat-Soluble Vitamins.

Proteins - Meat - Fish- Eggs - Cheese

Growth and Repair ~ Building Cells

Fruit & Vegetables - Wholemeal Bread- Fruit - Vegetables

- Pulses

The Fibre Or Roughage In Our Diet Is Not Digested. It Allows The Muscles In Our

Intestines To Move Food Throughout Our System By Peristalsis

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Mineral ions and vitamins are also important in a healthy diet. They are needed in a small amounts for healthy functioning of the body.

Imbalanced Diets:An imbalanced diet may cause a person to become malnourished. For example:- Too little food may lead to a person being underweight.- Too much food may lead to a person being overweight.

A poor diet may also lead to deficiency diseases. For example, too little vitamin D in the diet can lead to rickets, which affects the proper growth of the skeleton. Type 2 diabetes is also a problem related to poor diet. Note that you do not need to know how the nutrients work or the effects of any particular deficiency in the diet for your exam.

Metabolic Rate:A healthy diet contains all the different nutrients in the correct amounts, and provides the right amount of energy for each individual. An unbalanced diet can lead to a person becoming malnourished. They may be too thin or too fat as a result, and they may suffer from deficiency diseases.

Chemical Reactions –Respiration is the chemical reaction that allows cells to release energy from food. The metabolic rate is the speed at which such chemical reactions take place in the body. It variesbecause of several factors, including:- Age- Gender ~ Male or Female- The Proportion Of Muscle To Fat In The Body- The Amount Of Exercise And Other Physical Activity - Genetic Traits

The metabolic rate increases as we exercise and stays high for awhile afterwards.

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The Right Amount Of FoodNot Enough Food:

If you don’t eat enough food, you will become too thin and may suffer from health problems. These include:- Irregular Periods In Women- Reduced Resistance To Infection- Deficiency Diseases

Deficiency diseases include rickets – which affects proper growth of the skeleton and is caused by insufficient vitamin D – and Kwashiorkor – which causes a swollen abdomen and is a result of insufficient protein. Problems such as these are more likely to affect people in the developing world, where it can be more difficult to get enough food.

Too Much Food:In warm weather, or when you don’t do much exercise, you do not need to eat as much food as when it is cold or when you have exerted yourself physically. If you eat too much food without taking enough exercise, you will become overweight. Very fat people are described as obese. Overweight people may suffer from health problems, including:- Diabetes = An illness in which the body is unable to control the amount of sugar in the blood.- Arthritis = An illness in which the joints become worn, inflamed and painful.- High Blood Pressure- Heart Disease

The Heart:The heart is an organ that needs its own supply of blood to keep it working. If the blood supply is reduced, the heart muscle will not work properly and will become weaker. A heart attack happens when part of the heart does not get any blood because of a blocked artery.

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CholesterolCholesterol is a substance found in the blood. It is made in the liver and is needed for healthy cell membranes. However, too much cholesterol in the blood increases the risk of heart disease, and of diseased arteries.

Good & Bad Cholesterol:The bloodstream transports cholesterol around the body attached to proteins. The combination of cholesterol and protein is called lipoprotein, and there are two types.1. Low-Density Lipoproteins – LDL’s – Carry Cholesterol From The Liver To The Cells.2. High-Density Lipoproteins – HDL’s – Carry Excess Cholesterol Back To The Liver.

LDL’s are often referred to as ‘bad’ cholesterol because they lead to fat building up on artery walls, which causes heart disease. HDL’s are often called ‘good’ cholesterol because they help to stop fat building up in the arteries.

A high proportion of HDL’s to LDL’s is good for a healthy heart. Monounsaturated and polyunsaturated oils – as found in vegetable oils – help to reduce cholesterol levels in the blood, and also increase the proportion of HDL’s compared with LDL’s. Check your understanding of such oils by looking at vegetable oils.There are also drugs that can improve high blood pressure and high cholesterol levels.

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SaltTable salt is sodium chloride. Too much salt in the diet can lead to high blood pressure, which in turn leads to an increased risk or heart disease and strokes.Salt is found naturally in many kinds of food, but more is added by food manufacturers – and many people add even more when they are eating. Processed foods often have a high proportion of salt and fat. Salt added to food during processing accounts for about two-thirds of the average salt intake.

On average, men in the UK eat about 10g of salt a day and women in the UK eat about 8g of salt a day. However, food scientists recommend no more than 6g of salt a day in the diet. Reducing the amount of salt in the diet will help to reduce the risk of heart disease, and to a greater extent the risk of suffering a stroke.

There is some evidence that the food industry has persuaded government bodies to set higher government bodies to set higher targets for the recommended amounts of dietary salt in our food that doctors might wish.

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Defending Against Infection

Pathogens are micro-organisms ~ such as bacteria and viruses ~ that causes disease. Bacteria release toxins, and viruses damage our cells. White blood cells can ingest and destroy pathogens by producing antibodies that destroy the infectious micro-organisms, and anti-toxins to neutralise toxins created as a by-product.

Pathogens

Pathogens – Bacteria:Bacteria and viruses are the main type of pathogen. Bacteria are microscopic organisms. They come in may shapes and sizes, but even the largest are only 10 micrometres long - that’s 10 millionths of a metre.Bacteria are living cells and, in favourable conditions, can multiply rapidly. Once inside the body, they release poisons or toxins that make us feel ill. Diseases caused by bacteria include:- Food Poisoning- Cholera- Typhoid- Whooping Cough

Pathogens – Viruses:Viruses are many times smaller than bacteria. They are among the smallest organisms known and consist of a fragment of genetic material inside a protective protein coat.Viruses can only reproduce inside host cells and they damage the cell when they do this. A virus can get inside a cell and , once there, can take over and make 100’s of 1000’s of copies of itself. Eventually the virus copies fill the whole host cell and burst it open. The viruses are then passed out in the bloodstream, the airways, or by other routes.

Diseases caused by viruses include:- Influenza (Flu) - Colds- Measles - Mumps

- Rubella - AID’s

- Chicken PoxA hepatitis C virus showing DNA enclosed in a protein coat.

Structure of a salmonella bacterium cell.

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White Blood CellsWhite blood cells can:- Ingest Pathogens And Destroy Them.- Produce Antibodies To Destroy Particular Pathogens.- Produce Antitoxins That Counteract The Toxins Released By Pathogens.

In a written examination, it is easy to get carried away with metaphors about invaders and battles: stick to the point. Note that:- The Pathogens Are Not The Disease ~ They Cause The Disease.- White Blood Cells Do Not Eat The Pathogens ~ They Ingest Them- Antibodies And Antitoxins Are Not Living Things ~ They Are Specialised Proteins.

Types Of White Blood Cells:There are several types of white blood cells, each with a different function. But there are two main groups. The first of these groups surrounds and digests bacteria. They can pass easily through blood vessel walls into the surrounding tissue and move towards pathogens {Pathogens: Micro-organisms That Cause Disease} or toxins {Toxins: A Type Of Natural Poison Produced By An Organism, Often As A Form Of Protection}.The second produces antibodies to label micro-organisms. Pathogens contain certain chemicals that are foreign to the body. These are called antigens {Antigens: Foreign organismsthat get into the body, and trigger an immune response.}. Each of this group of white blood cell carries a specific type of antibody – a protein with a chemical ‘fit’ to a certain antigen.When a white blood cell with the appropriate antibody meetsthe antigen, the white blood cell reproduces quickly to make many copies of the antibody that neutralises the pathogen.

A white blood cell ingesting disease-causing bacteria.

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White Blood CellsThere are several different types of white blood cells, each with different functions, but they can be put into two main groups:- Phagocytes or Macrophages.- Lymphocytes.

Phagocytes:Phagocytes can easily pass through blood vessel walls into the surrounding tissue and move towards pathogens or toxins. They then either:- Ingest And Absorb The Pathogens Or Toxins.- Release An Enzyme To Destroy Them.

Lymphocytes:Pathogens contain certain chemicals that are foreign to the body and are called antigens. Each lymphocyte carries a specific type of antibody – a protein that has a chemical ‘fit’ to a certain antigen. When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte reproduces quickly, and makes many copies of the antibody that neutralises the pathogen.

Antibodies neutralise pathogens in a number of ways:- They Bind To The Pathogens And Damage Or

Destroy Them.- They Coat Pathogens, Clumping Them

Together So That They Are Easily Ingested By Phagocytes.

- They Bind To The Pathogens And Release Chemical Signals To Attract More Phagocytes.

Lymphocytes may also release antitoxins that stick to the appropriate toxin and stop it damaging the body.

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VaccinationsPeople can be immunised against a pathogen through vaccination. Different vaccines are needed for different pathogens.Vaccination involves putting a small amount of an inactive form of a pathogen, or dead pathogen, into the body. Vaccines can contain:- Live Pathogens Treated To Make Them Harmless.- Harmless Fragments Of The Pathogen.- Toxins Produced By Pathogens.- Dead Pathogens

These all act as antigens. When injected into the body, they stimulate white blood cells to produce antibodies against the pathogen.Because the vaccine contains only a weakened or harmless version of the pathogen, the vaccinated person is not in danger of developing disease – although some people may suffer a mild reaction. If the person does get infected by the pathogen later, the required lymphocytes are able to reproduce rapidly and destroy it.

Vaccinations And Boosters: Vaccines in early childhood can give protection against serious diseases. Sometimes more than one vaccine is given at a time, like the MMR triple vaccine mumps, measles and rubella.Sometimes vaccine boosters are needed, because the immune response ‘memory’ weakens over time. Anti-tetanus injections may need to be repeated every ten years.

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AntibioticsAntibiotics are substances that kill bacteria or stop their growth. They do not work against viruses; it is difficult to develop drugs that kill viruses without also damaging the body’s tissues.

How Some Common Antibiotics Work:

Antibiotic: How It Works:

Penicillin Breaks Down Cell Walls

Erythromycin Stops Protein Synthesis

Neomycin Stops Protein Synthesis

Vancomycin Stops Protein Synthesis

Ciprofloxacin Stops DNA Replication

Penicillin:The first antibiotic – penicillin – was discovered in 1928 by Alexander Fleming. He noticed that some bacteria he had left in a petri dish had been killed by naturally occurring penicillin mould.Since the discovery of penicillin, many other antibiotics have been discovered or developed. Most antibiotics used in medicine have been altered chemically to make them more effective and safer for humans. A bacterium damaged and distorted by penicillin

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Resistance:Bacterial strains can develop resistance to antibiotics. This happened because of natural selection. In a large population of bacteria, they may be some cells that are not affected by the antibiotic. These cells survive and reproduce, producing even more bacteria that are not affected by the antibiotic.MRSA is methicillin-resistant staphylococcus aureus. It is very dangerous because it is resistant to most antibiotics. It is important to avoid over-use of antibiotics, so we can slow down, or stop, the development of other strains of resistant bacteria.

Cleanliness:One simple way to reduce the risk of infection is to maintain personal hygiene and to keep hospitals clean. In the 19th century, Ignaz Semmelweis realised the importance of cleanliness in hospitals. However, although his ideas were successful, they were ignored at the time because people did not know that diseases were cause by pathogens that could be killed.