AS BIOLOGY - EVERYTHING on diet and food production OCR F212

A balanced diet is one that contains all the nutrients required for health in appropriate proportions. There are seven components to a balanced diet;

Carbohydrates - main source of energy. Eg. PASTA

Fats (lipids) - act as an energy store, provide insulation, make up cell membranes. Eg. COCONUT OIL

Proteins - Needed for growth, repair of tissues and muscle. Eg. RED MEAT

Vitamins - Different vitamins have different important roles in chemical processes taking place inside cells. Eg. GREEN VEGETABLES

Mineral Salts (Minerals) - Inorganic elements occuring in the body that are essential to its normal function. Eg. CHEESE

Fibre (Roughage) - Indigestible part of our food that aids movement of our food through the gut. Eg. BROCCOLI

Water - Used in chemical reactions, used to transport substances. Eg. WATER

An unbalanced diet is a diet whereby one or more of the seven components of a balanced diet is not being consumed to the extent it should be. When you consume too little or too much of the necessary nutrients, you undergo malnutrition.

The three main causes of malnutrition are;

1) Not having enough food therefore you get too little of every nutrient.

2) Having an unbalanced diet - too little of one nutrient can lead to a variety of deficiency diseases eg. too little iron in your diet causes anaemia - too much of the nutrients carbohydrates and fats can lead to obesity.

3) Not being able to absorb the nutrients from digestion into your blood stream properly eg. coeliac disease reduces absorbance of nutrients in the small intestine which can lead to other deficiency diseases as a result.

Obesity is becoming a large problem, caused by too much sugary and fatty food alongside too little exercise. Obesity can increase the risk of diabetes (type 2), arthritis, high blood pressure, coronary heart disease and even some cancers.

CHD is the result of reduced blood flow to the heart. It can lead to angina (chest pain) and a heart attack. It is caused by atherosclerosis - the narrowing and hardening of the coronary arteries (blood vessels supplying the heart). Main components that cause atherosclerosis are;

Excess salts - Decrease water potential of your blood which means more water is then held in the blood, increasing blood pressure. This can cause hypertension which is where the blood pressure is maintained at a too higher level. Hypertension then causes damage to the inner lining of the artery walls which is one of the early stages of atherosclerosis.

Excess fats - A diet high in saturated fats raises the blood cholesterol level.

Excess Cholesterol - Cholesterol is made from saturated fats and when combined with saturated fats and protein, forms LDLs (Low density Lipoproteins).

HDLs - Produced by combination of unsaturated fats, cholesterol and protein. They tend to carry cholesterol back to the liver where it is made into bile or broken down. Therefore, high levels of HDLs are associated with reducing blood cholesterol levels and reduced deposition in the artery walls by atherosclerosis.

LDLs - Produced by combination of saturated fats, cholesterol and protein. They tend to carry cholesterol from liver to tissues. Too much saturated fat and cholesterol leads to a high concentration of LDLs which causes deposition in the artery walls (atherosclerosis).

So it is beneficial to have a low concentration of LDLs and a high concentration of HDLs. This can be done by eating a low fat diet, eating a high proportion of unsaturated fats (polyunsaturated and monounsaturated fats).

Humans rely on plants for food because they are the basis of all food chains. Plants carry out photosynthesis to convert carbon dioxide and water into complex organic compounds (such as carbohydrates).

We grow plants for direct consumption and to feed to animals which we then eat because we are omnivores - we eat both plants and animals.

Many modern farming techniques aim to maximise productivity by increasing plant and animal yield.

Selective breeding alongside pesticides and fertilisers help us to increase this productivity.

Selective breeding is in the name. You select the plants/crops that have good characteristics such as high yield, disease resistant or aesthetically pleasing and reproduce them together to increase productivity. An step by step is;

1 - Select two crops with favourable characteristics such as tall plant and a plant that produces lots of vegetables. Breed them two together.

2 - Select the offspring with the best combination ie. tall with lots of vegetables, and breed them together.

3 - Continue this process over many generations until your lefts with a very tall high yielding plant variety.

This works just the same with disease and pest resistance.

Selective breeding can also occur in relation to animals in order to increase the productivity of the animals. Useful characteristics include fast growth rate, quality of meat, high meat yield, high milk yield or high egg yield. This can occur in a step by step process once again (cows as an example);

1 - Select animas with good characteristics that will increase meat yield and improve the quality of meat. So you choose a large variety of cow and breed it with a high quality meat variety of cow.

2 - Select the offspring that are both large, quality meat supply and breed them together.

3 - Continue this over several generations until your cows have an extremely large amount of meat available that is also of high quality.

Fertilisers are chemicals that replace minerals in the soil (eg. potassium) needed for the plant to grow. They increase the rate of growth and the overall size of the crop. They can be natural (eg compost) or artificial.

Pesticides are chemicals designed to kill organisms that cause disease on the crops or that feed on the crops. This prevents the crops being damaged or destroyed. Pests can include insects, mammals (rats). They may be specific to kill only one pest species or broad, and kill a range of species but this could mean some non-pest species may also be damaged.

Fungicides are chemicals used to kill fungi. They are same as pesticides except use to kill fungal problems rather than organisms.

Antibiotics kill or inhibit the growth of bacteria. They can help treat or prevent bacterial diseases. They also help promote growth of animals by influencing the bacteria in the animals gut, allowing them to digest food more efficiently. This can increase both growth rate and size and ultimately, increase food production.

1 - Populations of microorganisms grow rapidly under the right conditions, so food can be produced quickly.

2 - Microorganisms can grow on a range of inexpensive materials.

3 - Their environment can be artificially controlled - so you can potentially grow food anywhere and at any time of year.

4 - Conditions for growth are easy to create.

5 - Some of the food made using microorganisms often lasts longer in storage than raw products they're made from eg. cheese can be stored longer than milk.

6 - There are no animal welfare issues.

7 - The protein produced form microorganisms contains no animal fat or cholesterol.

8 - They provide a good source of protein for vegetarians.

1 - Palatability, the protein produced by microorganisms does not have the taste or texture of traditional protein.

2 - High risk of contamination because the conditions are also desirable for harmful microorganisms which could cause foods produced to spoil or if eaten, cause illnesses eg. food poisoning.

3 - Conditions for microorganisms are easy to create but small changes in temperature or pH can easily kill the microorganisms.

4 - Isolation of the protein made because microorganisms are grown in huge fermenters and need to be isolated form the material on which they grow.

5 - Many people do not want to eat fungal protein or food that has been grown on waste.

Salting - Is simply adding salt to foods. Salt inhibits the growth of microorganisms with their ability to absorb water (which is vital for their survival). 

Adding sugar - Inhibits the growth of microorganisms by interfering with their ability to absorb water.

Freezing - Freezers keep food below -18 degrees. This slows down reactions taking place in microorganisms and freezes the water in the food, preventing microorganisms from using it. Growth and reproduction become very slow.

Pickling - Using an acid with a low pH (eg vinegar) which denatures their enzymes and they cannot function properly. So pickling inhibits microorganisms growth.

Heat Treatment - Heating food to high temperatures kills any microorganisms present. Pasteurisation is a form of heat treatment for liquids eg milk.

Irradiation - Exposing ionising radiation kills the microorganisms present.