Biology AS OCR Unit 2

We eat so that:

1. we have a better health

2. stronger immune system

3. become ill less often

4. stronger

5. more productive

Components in our diet

Functions of the components

Carbohydrates

Energy store and supply

Fats

Insulation, protection layer, absorb fat-soluble vitamins, source of energy

Protein

Growth and repair of muscles and tissues

Water

As a solvent, allows reactions to take place, transport

Vitamins

Help chemical processes in cells

Minerals

Inorganic elements which are essential to the normal function

Fibre

Proper digestion, a bulk so that the gut can push against it to move food.

Energy taken in is more than energy spent = Weight Gain because excess energy is stored as fat in adipose tissues

Energy taken in is less than energy spent = Weight Loss because there is not enough energy present

BMI – mass in kg / (height in m) ²

When BMI is 30 or over, the person is considered obese because there is a body weight of 20% or more than the weight recommended for the person’s height.

The level of energy consumed should be consistent to the body’s needs because if sufficient energy is consumed, the person will have enough energy for their activities, if insufficient energy is consumed, the person will not have enough energy and will lose weight and if too much energy is consumed, the excess fat will deposit in adipose tissues and result in weight gain which can be dangerous.

Obesity can cause type 2 diabetes, cancer, cardiovascular diseases, gallstones, osteoarthritis and high blood pressure.

Excess energy in the body can cause coronary heart diseases (CHD). This is the result of fatty deposits building up on the walls of the coronary arteries. The deposition is known as atherosclerosis. The deposition narrows the lumen of the coronary artery and restricts the flow of oxygenated blood to the heart muscles. The heart muscles have an oxygen starvation.

Salt – causes high blood pressure also known as hypertension

1. too much salt in the diet causes water potential of the blood to decrease so what?

2. the water is held in the blood so what?

3. this causes increased in blood pressure so what?

4. this leads to hypertension or high blood pressure so what?

5. high blood pressure is harmful as it causes diastolic pressure to be maintained at a higher pressure so what?

6. as blood flows in the heart when it is in the diastolic stage / at rest, the pressure is higher than normal

so what?

7. the linings of the arteries are damaged and this is one of the early steps causing atherosclerosis

HDL - high density lipoprotein

This is associated with unsaturated fats from plants. So what? Unsaturated fat is combined with protein and cholesterol to transport cholesterol from the body cells to the liver cells. So what? The liver cells have receptors which allow HDL to bind to their surfaces. The liver cells use the cholesterol for making bile during metabolism or the cholesterol is broken down. So what? This reduces the level of cholesterol in the blood. So what? Therefore high levels of high density lipoprotein is associated to low cholesterol level since the lipoprotein transport the cholesterol to the liver cells to be broken down.

LDL – low density lipoprotein

This is associated with saturated fats from animals. So what? Saturated fat is combined with cholesterol and protein and transport cholesterol from the liver cells to the body cells. The body cells have receptors for LDL. So what? An accumulation of cholesterol happens in the body cells. So what? This causes the cholesterol level in the blood to increase. A diet with lots of saturated fat provides an increase in the LDL level.So what? This means that more cholesterol is transported from the liver.

Eating lots of saturated fat (animals) will increase the level of LDL.

Eating a low fat diet will decrease the overall level of lipoprotein in the blood.

Eating a diet with lots of unsaturated fat will increase the level of HDL and decrease the level of LDL

Eating lots of polyunsaturated fats will decrease the level of LDL

Eating lots of monounsaturated fats will decrease the level of LDL

Terms

Balanced diet – a diet that contains adequate amounts of all the necessary nutrients required for healthy growth and activity.

Malnutrition – it means eating much more or much less than required. If a person takes in much more than what he needs or if a person takes much less energy than what his body needs.

Obesity – when a person’s intake of energy is much higher than his body’s needs. The excess energy is stored as fat in adipose cells. When a person’s body weight is over 20% of the recommended weight for his height. BMI of 30 or more.

Prevalence – the number of people with a particular disease at a certain time.

Risk factor – it is a factor that increases the chance of contracting a disease. For example, a diet with high amount of saturated fat is a risk factor of CHD.

Atherosclerosis – also known as atheroma, the process of build up of plaque in the endothelial wall of arteries. After a while, the atheroma results in atherosclerosis which can further result in hardening of the artery walls, blood clot, narrowed lumen or high blood pressure in this part of the artery.

How can we make food production more efficient?

In plants:

• Increase yield from each plant
• Improve plant responds to fertiliser
• Prevent the loss of crops due to pests/diseases
• Improve growth rate of crops
• Improve resistance to fungi, parasites, pests.
• nitrates to make amino acid, magnesium for chlorophyll, phosphate ions for DNA/RNA

In animals

• Increase resistance to disease
• Improve growth rate of animals
• Increase productivity
• Improve quality of meat, products.

Fertilisers – contain minerals and added to the soil to improve its fertility

Pesticides – a chemical used to kill pests

Fungicides – chemicals used to kill fungi

Antibiotic – a chemical used to kill or prevent the reproduction of bacteria

What is the difference between natural selection and artificial selection?

Natural selection is the selection of particular characteristics which are well adapted to the environment. The selection pressure is the environment forces. Artificial selection is the selection done by human to allow individuals with the desired characteristics to breed so that there is an exaggeration of the desired characteristic

Mycoprotein – single cell protein

This is the new food produced using micro organisms. A fungus called Fusarium Venenatum is used. The fungus is used to make a product which is a meat substitute called Quorn.

Advantages

• micro organisms grow quickly
• give a high yield and fast production
• low fat or no fat food, does not contain any animal fat or cholesterol
• high protein content needed by vegetarians
• less space is needed than what is needed to rear animals
• less waste products is needed
• less expenses on antibiotic, shelter needed
• can be grown independent to the weather
• uses waste products such as sugars as a substrate

Disadvantages

• expensive purification to ensure that it is not contaminated
• Palatability – it does not have same taste and structure as meat
• micro organisms can be subject to infections by viruses
• Customer resistance to new food.
• Lack of essential amino acids
• Because it is a micro organism, it has a chitin wall which can be indigestible
• Many people may not want to eat fungal protein

Food is often treated to kill bacteria or prevent bacteria from growing or multiplying in the food.

Cooking

The heat denatures the enzymes and other proteins and kill the micro organisms

Pasteurising

Heating for 15 s at 72 C and then cooling rapidly to 4 C to kill harmful microorganisms

Drying, salting, coating

Water leaves by osmosis, and this causes dehydration in microorganisms . They can no longer function normally.

Smoking

The food develops a hard outer surface. The smoke contains antibacterial chemicals

Pickling

An acid is added and the pH change kills the microorganisms by denaturing enzymes

Irradiation

Use of radiation to kill microorganisms by destroying DNA structure

Cooling and freezing

As the temperature is low, the activity of the enzymes in microorganisms is very slow and so are metabolism, growth and reproduction of microorganisms. Not killed.