Chapter 10 - Diet and Food Production

Heterotrophs - humans, we rely on organic substances in our diet that have been made by plants

Autotrophs - plants, use inorganic substances to build organic substances such as carbohydrates, proteins and enzymes. 

Carbohydrates - provide energy (bread, rice)

Proteins - formation of new cells and tissues, growth and repair of muscles (meat, eggs)

Lipids - making cell membranes, proived energy when broken down during respiration (Diary products, oils)

Vitamin A - makes pigment for rod cells in eye, essential for vision (eggs yolks, carrots)

Vitamin C - makes collagen (citrus fruits, potatoes)

Vitamin D - formation of bones and teeth (dairy food, oily fish)

Iron - formation of haemoglobin (meat, beans)

Calcium - bone formation and blood clotting (dairy products)

A good diet contains a full range of all key nutrients in their right proportions

Malnutrition is "bad eating". Refers to any diet that is seriously unbalanced.

UK mains problem is Obesity. Obese people are seriously over weight. Have a BMI > 30

Obesity is where you eat to many nutrients that provide you with more energy than you need. Spare energy is stored as fat in the adipose tissues underneath skin.

Obesity can cause type 2 diabetes and arthritis. Obesity is becoming more of a problem.

Common disorder of the blood vessels that supply oxygenated blood to the heart.

Ability of the cardiac muscle to contract it needs a constant supply of oxygenated blood. The muscles use the oxygen for respiration which provides the energy for contraction.

If there is no oxygen, the muscles cant contract.

CHD is caused by Atherosclerosis in the coronary arteries.

Atherosclerosis is cause by build up of atherome

• 1. Part of the arery lining is scared (possibly caused by high blood pressure)
• 2. White blood cells sent to invade the damaged lining
• 3. Causes build up of cholesterol and lipids
• 4. Over time the phagocytes & cholesterol build up under artery lining forming a fibourous protein 
• If atheromas get to big they could rupture endothelium, this leaves a rough surface on lining of artery.
• Blood clot could form at the site of rupture, and could block up the vessel

Myocardial Infartcion is the loss of sufficient blood flow to muscles.

Myocardial Infarction is caused by coronary thrombosis.

If the infarction involves a large amount of muscles the person may die immediatly. Severe myocardial infarction may cause the heart to stop beating (cardiac arrest)

Most common time is first thing in the morning and at 5pm

Staurated fat diets which provide human with a lot of cholesterol can increase risk of CHD

Strokes

Occur when there is a disruption of the flow of blood to the brain. This can be caused by a blood clot in artery leading to the brain

Cholesterol is not soluble in water, and therefore is transported in solution in the blood plasma as lipoproteins

Lipoproteins are tiny balls made up of various lipids, cholesterol and proteins

High Density Lipoproteins HDL's - lots of protein & small amounts of lipids

Low Density Lipoproteins LDL's - more lipids and less proteins than HDL's

Chylomicrons - contains a lot of lipid & very little protein

HDL's usually pick up cholesterol from dying body cells and deposit it in the liver

LDL's carry lipids and cholesterol to liver

Chylomicrons carry lipids from small intestine to liver

LDL's have a tendancy to deposit the cholesterol and lipids in the damaged walls of the arteiry on its way to the cells in the body. This then builds up and contributes to Atheromatous plaque.

HDL's seem to help stop CHD. They can pick up the cholesterol and deposit it back in the liver.

HDL's = Good
LDL's = Bad

Lower the proportions of LDl and Higher proportion of HDL = reduced risk of CHD

To get this a person must eat a diet lower in saturated fats (saturated fats have high amounts of LDL's in them) therefore eating less dairy and meat.

However it isnt only food that gives humans LDL's. It is also produced in the liver. High amount of LDL intake means that the liver produces less.

Most effective way to reduce LDL's is to use drugs called Statins. Statins inhibit a enzyme in the liver cells which catalyses one of the reaction which forms cholesterol

Blood pressure is the force that the blood exerts on the walls.

If a person resting blood pressure is excessively and persistently high, they are said to have hypertension.

Hypertension can increase risk of CHD. Causes walls of arteries to thicken and stiffen. Increases the risk of damage to the epithelium lining the vessel. Which is followed by atheromatous plaque.

Also the heart has to pump doubley hard and this can overwork it.

High salt concentratin means water is brought into the blood by osmosis. Increasing blood volume and increasing the pressure.

Farming began over 10,000 years ago.

Since then they have been keeping the seeds of the best plants to grow the next year and doing the same each year. This has led to farmers now having the best crops. Wheat crops now have higher yields and better harvesting characteristics.

Specified characteristics can be seen and those genes can be taken and mixed with other genes carrying specifiec charcterists so you get a super plant.

Gene modification can be used to introduce a new gene into the crops.

Part of the wheat plant that is desirable is the grains.

The rest of the plant form straw and stubble. Straw has a extremely low value and farmers usually have to pay to get rid of it.

2000

A new breeding programme began to produce a new, dwarf variety that gives a higher yield and less waste.

Leaf Rust is a disease of what caused by a fungus.

It is common in warm wet conditions. e.g. Asia

Majoirty of the cultivars of wheat grown in Asia now do have some resistance.

If 2 or more cultivars have same resitstance genes, they could quickly become susceptible to the funus if it can evolve their defences.

Best strategy to prevent it is produce a cultivar with sevel different gens that stop rust. Not all of these can be overcome.

Researches have found many different genes in wheat each of which has a small effect and which add up to provide excellent resistance.

Difficult to carry out selective breeding to produce varieties of many different rust resistance genes. This is partly because it is hard to find starter varieties with more than one of the genes, so breeder have to reproduce with 5 or 6 plants.

Russian wheat aphid is a pest. It settle on the growing wheat plant and push their styluts in the the phloem of the wheat plant. The phloem sap seeps out into the aphids.

Then plant can lose a large proportion of fluid this way, which reduces their growth and yield.
Aphids can also carry disease which can affect the plant causing it to be weak and reduce its yield. 

Pesticides can be used to kill the aphids, but this is expensive.

It is possible that wheat plants can be introduced with a toxin in its genes.

Selective breeding is still used to see which comes out best.

In cattle breeding there is no longer a need to take bulls to cows. Semen can be collected from the chosen bull. Then this is used for artificial insemination. Farmers can look up characteristics and order semen from which bull has the best characteristics.

Semen can be frozen and transported over long distances. One bull can be used for breeding with many other cows.

For milk yield you choose a bull, whose its female cow has the largets milk yield.

Fertilisers are added to soils when the soil is lacking one of more key nutrients.

Most used fertiliser is ammonium nitrate.

Fertilisers are expensive, so farmers must only use them if they have a benefit overall.

Soil tests will show wether a soil is lacking nutrients. They can also use GPS to map the soil content in a field

Fertilisers only help until a certain point, after too much they can decrease yield. The high concentrations of solutes decreases water potential below that in the roots so water moves out of the plant.

Another problem is that the water can wash the fertilisers into seas and rivers causing Eutrophication.

Kill Pests - they include insecticides and fungicides

Some pesticides used to be highly damaging because they werent biodregadable.

A example is DDT - doesnt not breakdown in a organism and can build up in organism. Animals at top of food chain can gather large amounts of DDT through the food chain.

Another problem with DDT was that it was a broad-spectrum insecticide (kills all insects not just the pests) Bees maybe killed but they are useful as the pollinate.

Specific insecticides have been developed but are costly.

Pesticides can cost a lot and the insect can develop a resistance. Also the taste may linger on the food.

Chemicals the kill bacteria without harming the organism that is infected.

When animals are kept in intensive conditions the chance that they will gather a disease.

People found out that treatment of antibiotics would increase growth rates, even if the animal had no disease.

Antibiotics kept down the overall numbers of bacteria reducing disease.

4 degrees will considerably slow down the growth of microbes

Doesnt complete stop microbe growth.

Frozen stops microbe growth.

+ve = very little losss of nutritional value

-ve = water expansion leads to mushy foods

Removes all moisture, less effect on taste compared to dehydration

Food quickly frozen and placed in vacuum

Food in low pressure, the water in the food the vapourises

Salt of Sugar used to generate a high solute concentration in food.

Inhibit growth of microbes which lose water by osmosis

Pasteruisation of milk - heating up milk to 63degrees for 30 mins. Then rapidly cool down to 4 degrees.

This does not kill all microbes.

UHT milk - heated well above boiling point as is then sealed in a air tight container. Keeps milk alive for long time.

1. Ionisation radiation can kill cells

2. Radiation excited the electrons in atoms

3. Radicals formed and are highly reactive which kill cells

4. Radiation can damage cells (DNA)

5. Radiation absorbed microorganisms & food radication can alter taste