Chapter 3 Food ( Biomolecules) Summary Notes
After studying this chapter you should know the following:
1. Nutrition means getting and using food.
2. The Functions of food are
1. for energy. ( e.g. sugars and lipids)
2. for growth and repair. (e.g. protein).
3. to control metabolic reactions (e.g. enzymes, hormones, minerals and vitamins).
3. Food is made of chemicals.
??? There are six common chemical elements in organisms: C, H, O, N, P and S,
??? five elements in dissolved salts: Na, Mg, Cl, K and Ca.
??? three trace elements: Fe, Cu and Zn. (trace elements are those needed in only tiny amounts)
4. Biomolecules are chemicals made in living organisms, e.g. glucose, lipids, proteins, DNA etc.
The main biomolecules in food are Carbohydrates, Lipids, Proteins and Vitamins.
5. Minerals come in to the body from the soil through plants and animals that feed on plants.
Minerals are not classed as biomolecules.
Chemical elements combine in different ratios to form simple biomolecular units, (sub-units)e.g. the unit from which carbohydrates are made is Cx(H2O)y.
6. For each of the nutrients Carbohydrates, Lipids and Proteins you need to know the following:
1. The elements it is made of.
2. The sub-unit it is made of.
3. Named examples of it.
4. It??™s general function.
5. Two good sources of it in the diet.
6. Its structural role. ( i.e. its role in building parts of cells and the body)
7. Its metabolic role. (i.e. its role in reactions in the cells).
8. A laboratory test for it.
See Tables below.
Once you know these facts for each biomolecule you should be able to make comparisons between them in terms of their similarities and differences.
Vitamins are large complex organic molecules that are needed in relatively small amounts by the body for it to function properly.
Vitamins are classified as being either water-soluble or fat-soluble. This fact can be used when thinking of source of the vitamins, i.e. what foods in the diet they are found in.
Water-soluble Vitamins include Vitamin C and the B vitamins.
Fat-soluble Vitamins include Vitamin A, D, K and E.
You only have to know about any one water-soluble and one fat-soluble vitamin.
For each Vitamin selected you need to know:
??? its name,
??? whether it is water-soluble or fat-soluble.
??? its function i.e. what the body needs it for.
??? one deficiency disease for it ( i.e. what happens to you when the vitamin is missing from your diet). See below
Water Soluble: Vitamin C and B.
Role: Vitamin C is needed to build connective tissue (in gums/ blood vessel walls).
Deficiency Disorder: Scurvy – breakdown of connective tissue.
Fat/Lipid Soluble: Vitamins D, A, K, E.
Role : Vitamin D is needed for calcium absorption to make strong bones and teeth.
Deficiency disorder: Rickets in children/ Osteomalacia (softening of bone) in adults.
Minerals such as calcium, magnesium and zinc which originally form part of the earth??™s crust. You must know the need for and use of any two minerals present in dissolved salts or in trace amounts in plants and animals.
Minerals are needed to build both rigid and soft body parts and to function in cellular fluids (cytoplasm).
Know 2 Minerals needed by Plants and 2 Minerals needed by Animals.
Calcium (Ca) : needed to form the middle lamella (which cements plant cells together).
Magnesium (Mg): essential for chlorophyll formation. Too little Mg means a plant cannot photosynthesise properly.
Iron (Fe) : needed to form haemoglobin. Too little iron means not enough oxygen can be transported by the red blood cells.
Calcium (Ca): needed to form strong bones and teeth.
9. METABOLISM :- The sum of all the chemical reactions occurring in cells.
(a) Anabolic Reactions involve building large molecules from smaller ones.
This requires energy.
Eg. 1. Photosynthesis CO2 + H2 O = C6H12 O6 + O2.
2. Protein synthesis. (building proteins in cells).
(b) Catabolic reactions involve breakdown of large molecules into smaller ones.
This releases energy.
Eg. 1. Respiration C6H12 O6 + O2 = CO2 + H2 O + Energy.
2. Digestion: (breaking down large molecules to smaller ones)
|Common Elements |Mineral Elements |Trace Elements( needed in TINY amounts) |
|Carbon (C) |Sodium (Na) |Iron (Fe) |
|Hydrogen (H) |Potassium (K) |Copper (Cu) |
|Oxygen (O) |Magnesium (Mg) |Zinc (Zn) |
|Nitrogen (N) |Calcium (Ca) | |
|Sulphur (S) |Chlorine (Cl) | |
|Phosphorous (P) | | |
11. Finally, know the important role of Water in organisms.
??? is a component of the cytoplasm of cells and body fluids( blood)
??? is a solvent and a medium in which chemical reactions can take place.
??? can take part in chemical reactions, e.g. it is needed for photosynthesis and is a product of aerobic respiration.
??? controls cell shape and enables movement of substances into and out of cells.
??? is a good absorber of heat energy and therefore provides a constant environment, particularly for aquatic organisms.
12. Biomolecules in Food ??“ Summary Table
|Biomolecule |Elements |Type (sub-unit) |Example |Test |Structural Role |Metabolic Role |Source in |
| | | | | | | |diet |
|Carbohydrate: C(H2O) |C, H, O |Monosaccharide |Glucose, |Benedict??™s | |To release energy|Fruit |
| | |(single sugar unit) |fructose |Heat | |in respiration | |
| | | | |Blue >brick red | | | |
| | |Disaccharides (double |Sucrose, lactose| | |To release energy|Sugar |
| | |sugar units) | | | |in respiration. |Milk |
| | |Polysaccharides |Starch ??“ made of|Iodine | |Store of energy |Bread |
| | |(many sugar units in a |many glucose |Brown > | |in Plants |Pasta |
| | |chain) |units |blue-black | | | |
| | | |Glycogen ??“ mad | | |Store of energy |Meat |
| | | |of many glucose | | |in animals | |
| | | |units | | |(muscle) | |
| | | |Cellulose | |Build cell walls | |Veg, fruit |
| | | | | |of plants | | |
| | | |Chitin | |Builds cell walls| | |
| | | | | |of Fungi | | |
|Biomolecule |Elements |Type (sub-unit) |Test |Example |Structural Role |Metabolic Role |Source in diet|
|Protein | C, H, O + N |Amino acid |Biuret test |Globular ??“ enzymes| |Involved in the |Milk |
|(made at the | | |Blue > Purple |(amylase) and | |chemistry of the | |
|Ribosomes) | | |(no heat) |hormones (insulin)| |cell e.g. | |
| | | | | | |catalysts. | |
| | | | | | | | |
| | | | |Fibrous ??“ |Keratin is found | |Meat |
| | | | |Keratin and Myosin|in nails and hair.| | |
| | | | | | | | |
| | | | | |Myosin is found in| | |
| | | | | |muscle. | | |
|Biomolecule |Elements |Type (sub-unit) |Test |Example |Structural Role |Metabolic Role |Source in |
| | | | | | | |diet |
|Lipid | C, H, O |3 Fatty acids + |Brown paper test. | |Storage and |To release energy |Butter, |
| | |glycerol |transluscent spot | |insulation. Part of|in respiration. |Cheese |
| | | |appears. | |cell membranes. | | |