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A.3.1 Define protein, amino acid, essential and biological value.

A complex, high-molecular-weight, organic compound consisting of an amino acid joined by a peptide bond. Proteins make up the constituents of biological organisms.
Amino acid
In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. In biochemistry, this shorter and more general term is frequently used to refer to alpha amino acids in which the amino and carboxylate functionalities are attached to the same carbon, the so-called α-carbon (alpha-carbon).
A compound that cannot be made in the body but has to be provided ready-made in the diet, for example, vitamins, essential fatty acids and essential amino acids.
Biological value
The biological value of a protein refers to how much of the nitrogen content of food is retained by the body. The biological value of proteins ranges from 50% to 100% and is a measure of how much dietary protein source can support growth.

A.3.2 Describe the role of protein in the body.

Protein provides essential and non-essential amino acids and acts as an energy source.

A.3.3 Identify foods of high biological value and low biological value.

  • High biological value proteins are provided by animal sources of protein, such as meat, poultry, fish, eggs, milk, cheese and yoghurt.
  • Low biological value proteins are found in plants, legumes, grains, nuts, seeds and vegetables.
  • Table of BV foods and a definition from

A.3.4 Describe how low biological value foods are complemented in different parts of the world to ensure that essential amino acid requirements are met.

For example, complementation of rice and beans.

A.3.5 Discuss the effect of low protein intake.

A diet too low in protein could result in many disorders, especially when the poor diet is one of a child. Lack of protein in a child’s diet could result in marasmus, which is a sickness that leads to extensive tissue and muscle wasting; the child’s weight may decrease to 80% less then the normal weight for its height.

Kwashiorkor is another medical illness that low protein could lead to; it is very similar to maramus except for the fact that kwashiorkor’s occurrence after 18 months while maramus’s occurrence increases prior to one year old. Victims of kwashiorkor show signs of swelling feet and distended abdomen, enlarged liver, loss of hair and teeth, children who suffer from this disease usually end up with anorexia and irritably.

Low protein for children can also result in stunted growth; the less then average height remains permanent for the child. The low protein in the diet will impede recovery, decrease healthy muscles, increase body fat levels and increase the chance of over-training.


A.3.6 Define monosaccharide, disaccharide and polysaccharide.

The simplest form of carbohydrate, consisting of one sugar residue. They are the building blocks of disaccharides and polysaccharides.
A sugar (a carbohydrate) composed of two monosaccharide molecules.
A polymer comprising many monosaccharide molecules joined by glycosidic links. For example, starch and cellulose.

A.3.7 Describe the role of carbohydrate as an energy source in the body.

A.3.8 Identify the importance of staple foods in the provision of dietary carbohydrate.

For example, cassava, rice, wheat, maize, potatoes and sugar.

A.3.9 Explain that carbohydrate foods are often cheap and used by people on low incomes to bulk their diet.

From the supermarket Coles

  • Beef (cheapest) = $14/kg
  • Chicken = $6/kg
  • Rice = $2/kg
  • Cous cous = $5/kg

A.3.10 Discuss the effects of low and excess carbohydrate intakes.


A.3.11 Define lipid, glycerol, fatty acid, essential fatty acid, saturated fatty acid and unsaturated fatty acid.

An organic compound that contains aliphatic hydrocarbons, essential for the structure and function of living cells. Examples include fats, waxes and steroids.
A sugar alcohol with three hydrophilic alcoholic hydroxyl groups. It is an important component of triglycerides (fats and oils) and phospholipids
Fatty acid
Fatty acids are carboxylic acids with a long hydrocarbon chain, usually straight.
Essential fatty acid
Fatty acids that are required in the human diet. This means that they cannot be synthesized by the body from other fatty acids and must be obtained from food.
Saturated fatty acid
A fatty acid in which no double bonds are present between the carbons of the fatty acid chains.
Unsaturated fatty acid
One in which there are double bonds present between the carbons of the fatty acid chains.

A.3.12 Describe the role of lipids in the body.

The three major purposes of lipids are energy storage, cell membrane development, and serving as a component of hormones and vitamins in the body. Wisegeek

Lipids play a role of storage for energy in the body, and upon oxidation it produces a great deal of energy.

A.3.13 Identify major sources of lipids in the diet.

Lipids are generally fats (usually animal) & oils (plant such as palm oil), waxes (bees & plants) and steroids

A.3.14 Discuss the effects of low and excess lipid intakes.

  • High lipid intake - can cause heart disease, stroke, and high blood pressure.
  • Low lipid intake - hypolipidemia, grow poorly

Vitamins and minerals

A.3.15 Define vitamins and minerals.

Organic molecules required by a living organism in minute amounts, but which the organism cannot synthesize.
Natural compounds formed through geological processes.

A.3.16 Describe the role of water-soluble vitamins (vitamin B complex, vitamin C) in the body and their food sources.

Link to Colorado State University extension programme.

A.3.17 Describe the role of fat-soluble vitamins (vitamins A, D, E, K) in the body and their food sources.

Link to Colorado State University extension programme.

A.3.18 Describe the effects of deficiency of water-soluble vitamins on the body.

For example, effect of lack of B vitamins or vitamin C.

Link to Colorado State University extension programme.

Vitamin C Vitamin B
* Bleeding gums
* scurvy
* increase in infection
* dry and rough skin
* Skin disorders
* mental confusion and/or irritability
* weakness
* beriberi.

A.3.19 Describe the effects of deficiency or excess of fat-soluble vitamin intake.

For example, cases of excess vitamin A or D intake in children in western Europe, and effect of lack of vitamin A on eyesight in parts of central Africa.

Link to Colorado State University extension programme.

A.3.20 Describe the functions and sources of minerals.

Consider calcium and iron.

Alternative Medicine Angel has a table summarising the various minerals and their roles.

  • STRUCTURE: The skeleton (e.g calcium, magnesium, phosphorus)
  • CELLULAR FLUIDS: (e.g. iron in haemoglobin)
  • BODY FLUIDS: (e.g. nerve transmition) wikianswers

A.3.21 Discuss the effect of low or excessive intake of calcium and iron.

  • Low calcium intake and cause bones to weaken and fracture or break easily. As well as osteoporosis later in life.
  • High Calcium intake can cause kidney or bladder stones.
  • Low iron intake can cause anaemia or fatigue
  • High iron intake (toxicity) can be dangerous and fatal; symptoms include fatigue, nausea, dizziness, headache, shortness of breath, and a grey tint to the skin.

Balanced diets and health

A.3.22 Define micro-nutrient deficiency and malnutrition.

The physiological condition resulting from inadequacy or imbalance in food intake or from poor absorption of food consumed.
Micro-nutrient Deficiency
Lack of essential vitamins and minerals resulting from unbalanced food intake and specific problems of food absorption

A.3.23 Explain what is meant by a balanced diet and how various food-group systems can be used to help achieve a balanced diet.

Consider pyramid, chalice, “five a day” and plate systems.
  • PDF from Food insight. Has the food chalice as well as other cultural balanced diet images.
  • Picture this! we article of the different ideas of a balanced diet.

Chalice is the Israeli explanation.

Pyramid Plate Systems “five a day”

A.3.24 Explain how nutritional requirements and food choice change as a person gets older.

  • As you age changes occur in your body that affect your nutrintioanl requiremenst and food choice.
  • For example it is very important to ensure the correct calcium levels in your diet for bones however later in adulthood you don't need as muchs.

A.3.25 Identify the nutrient content of typical foods.

A.3.26 Discuss how health awareness affects food choice with reference to fat (quality and quantity), fibre, sugar and salt content.

Consumer awareness of acute and chronic health issues has a major impact through the food chain from food production to food manufacture and distribution. Understanding of such issues and health impacts has a considerable influence on patterns of food consumption.

A.3.27 Discuss the social impacts resulting from a change from traditional diets and the effect on consumer health.

Consider the increasing incidence of diabetes and obesity.
  • NEJM peer reviewed article of the rise of diabetes and obesity
  • "In the past 20 years, the rates of obesity have tripled in developing countries that have been adopting a Western lifestyle involving decreased physical activity and overconsumption of cheap, energy-dense food. Such lifestyle changes are also affecting children in these countries; the prevalence of overweight among them ranges from 10 to 25%, and the prevalence of obesity ranges from 2 to 10%. The Middle East, Pacific Islands, Southeast Asia, and China face the greatest threat" excerpt from Obesity and Diabetes in the Developing World — A Growing Challenge Parvez Hossain, M.D., Bisher Kawar, M.D., and Meguid El Nahas, M.D., Ph.D.
  • Photo gallery from Time. Photo Essay - How the World Eats
  • Accompanying article from time How the World Eats

Some interesting Podcasts related to food


Bulleted list and italicised paragraphs are excerpted from Design Technology: guide. Cardiff Wales, UK: International Baccalaureate Organization, 2007.

Images are clickable links to its location.

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Page last modified on December 16, 2012, at 03:39 AM