1. 1.3.1 Function of Food
Why do we need food?

2. Need to know
The Function of Food
Three reasons for requiring food

3. Food is needed for: Energy Growth of new cells and
Repair of existing cells, tissues, organs, etc.

4. Food also supplies: the materials and energy for the processes of:
Metabolism and
Continuity

5. Learning check Why do we need food? What is metabolism?
Energy
Growth of new cells and
Repair of existing cells, tissues, organs, etc.
What is metabolism?
Metabolism is the chemical reactions that occur in the cells of living organisms
What is continuity?
Continuity of life is the ability of an organism to exist from generation to the next

6. 1.3.2 Chemical Elements
Elements in Food

7. Need to know Chemical elements Six common elements in food
Five elements in dissolved salts
Three trace elements

8. What is Food made up of? Food is made up of: Six chemical elements
C, H, O, N, P, S
Salts of
Na, Mg, Cl, K, Ca
Three trace elements
Fe, Cu, Zn

9. Chemical Elements and their Symbols
Calcium Ca
Nitrogen N
Carbon C
Oxygen O
Chlorine Cl
Phosphorus P
Copper Cu
Potassium K
Hydrogen H
Sodium Na
Iron Fe
Sulphur S
Magnesium Mg
Zinc Zn

10. 1.3.3 Biomolecular Structures

11. Need to know Define Biomolecular Structures
State that simple biomolecular units are composed of a combination of elements in different ratios e.g. carbohydrates Cx(H2O)y

12. Types of Food
The elements combine in different ratios to form different food components (biomolecular units) Food is made up of six different components Water Proteins Lipids Carbohydrates Vitamins Minerals

13. Humans are mainly made up of Water!

14. Carbohydrates
Carbohydrates contain the elements Carbon Hydrogen Oxygen The general formula for a carbohydrate is Cx(H2O)y There are twice as many hydrogen molecules as oxygen molecules

15. Learning check
What are the six different food components? Water Proteins Lipids Carbohydrates Vitamins Minerals

16. A common carbohydrate
General formula = Cx(H2O)y When x = y = 6 We fet the formula C6H12O6 What is the name of this monosaccharide carbohydrate? Glucose

17. Another common carbohydrate
General formula = Cx(H2O)y When x = 12 and y = 11 We get the formula C12H22O11 What is the name of this disaccharide carbohydrate? Sucrose

18. Learning check
Name the three elements that make up carbohydrates Carbon Hydrogen Oxygen What is the general formula for a carbohydrate? Cx(H2O)y

19. 1.3.4 Biomolecular Sources and the Components of Food

20. Need to know
State that simple bio molecular units are composed of a combination of elements in different ratios e.g. carbohydrates Cx(H2O)y
Name the element components, bio molecular components and sources of: carbohydrates, lipids and proteins.
State that carbohydrates are composed of indivisible units and give examples of these e.g.
Monosaccharides – glucose;
Disaccharides – maltose; &
Polysaccharides – starch/cellulose.

21. Need to know What is a vitamin? Name one water soluble vitamin.
Name one water in-soluble vitamin (fat-soluble)
List the sources of these vitamins

22. Carbohydrates Carbohydrates contain the elements Hydrogen Oxygen
Carbon
Hydrogen
Oxygen
Usually in the ratio of 1C:2H:1O
They have twice as many hydrogen molecules as oxygen molecules

23. 3 Types of Carbohydrate
Monosaccharides Disaccharides Polysaccharides

24. Monosaccharides
Photo Credit fruit image by Edvin selimovic
from Fotolia.com
These are single sugar molecules simple sugars soluble in water sweet to taste smallest carbohydrate unit Examples: glucose, fructose Found in: fruit

25. Learning check
What are the elements that make up all carbohydrates? Carbon Hydrogen Oxygen Can you remember the general formula for a carbohydrate? Cx(H2O)y

26. Disaccharides These are
two monosaccharide sugar units joined together – known as double sugar molecules
soluble in water
sweet to taste
Examples: sucrose, lactose, maltose
Found in: table sugar, milk

27. Polysaccharides These are
Many monosaccharide sugar molecules joined together
Not soluble in water
Do not taste sweet
Example: starch, cellulose
Found in: bread, pasta, cereals

28. Learning check Name the three types of carbohydrate Monosaccharides
Disaccharides
Polysaccharides

29. Lipids Lipids are a diverse group of substances which include
fats (solid at room temp.)
oils (liquid at room temp.)
steroids which include cholesterol and some of the sex hormones
waxes which cover insect bodies and plant leaves.

30. Structure of Lipids
They are made up of the elements carbon hydrogen oxygen But not have the same ratios as carbohydrates. They are made up of two main types of molecules Fatty acids and Glycerol

31. Learning check Give examples and sources of: Examples Sources
Monosaccharides
Disaccharides
Polysaccharides
Glucose
Fructose
fruit
Sucrose
Lactose
Table sugar
Milk
Starch
Cellulose
Bread, Pasta,
Cereals

32. Types of Lipid
Two of the main types of lipids are Triglycerides Phospholipids

33. Triglyceride This is the smallest lipid It is made up of
Fatty Acid 1
Fatty Acid 2
Fatty Acid 3
Glycerol
It is made up of
3 fatty acid molecules
and
1 glycerol molecule

34. Phospholipids
If one fatty acid of a lipid molecule is replaced by a phosphate group then a phospholipid is formed
Fatty Acid 1
Fatty Acid 2
Glycerol
Phosphate

35. Sources of Lipids
Fat – in and on meat
Butter (80% fat)
Cooking oils

36. Learning check
The two main types of molecules that make up lipids are: Fatty acids and Glycerol The two main types of lipids are: Triglycerides Phospholipids

37. Proteins
Proteins contain the elements Carbon Hydrogen Oxygen Nitrogen Some may also contain sulphur, phosphorous or iron Proteins are found in lean meat, fish, pulses, soya and eggs

38. Structure of Proteins
Proteins are made up of long chains of amino acids There are 20 common and several rare amino acids found in proteins More amino acids are found in cells and tissues but are not in proteins Amino acids are joined together by peptide bonds This results in the formation of polypeptide chains

39. Learning check
Proteins contain the elements Carbon Hydrogen Oxygen Nitrogen Sometimes they contain sulphur, phosphorous or iron Proteins are made up of long chains of amino acids

40. Vitamins Vitamins are essential organic catalysts of metabolism
Needed in small amounts, cannot be produced in the body
Must be supplied continuously and in sufficient quantities
Differ from each other chemically

41. Vitamins
We need Vitamins A, B, C, D, E and K in our diets to keep us healthy Vitamins can be water soluble or fat soluble Vitamins B and C are water soluble Vitamins A, D, E and K are fat soluble

42. Sources of Vitamins Green leafy vegetables, Eggs, Cheese, Carrots
Lean Meat, Cereals, Nuts C
Citrus Fruits, Green vegetables, Turnips D
Milk and Milk products, Sunlight E
Vegetable oils, fish, nuts K
Green leafy vegetables

43. Learning check
What is a vitamin? A vitamin is an essential organic catalyst of metabolism What vitamins dissolve in water? B & C What vitamins are fat-soluble? A, D, E and K

44. 1.3.5 Energy Transfer Reactions
Anabolic & Catabolic Or
Anabolism & Catabolism

45. Need to know Definition of the terms: Anabolic Catabolic
Give an example of each

46. Anabolic Reactions
This is where energy is used to make large molecules (e.g. C6H12O6) from smaller ones (e.g. CO2 and H2O) using enzymes
e.g. Photosynthesis – glucose molecules are formed from carbon dioxide and water using enzymes and the energy from the sun.
This is anabolism. Energy is absorbed.

47. An Anabolic Reaction
Energy being used to join two small molecules to make a larger molecule
ENERGY
Small molecule
Larger molecule

48. Catabolic Reactions
This is where energy is released when large molecules (e.g. C6H12O6) are broken down to form smaller ones (e.g. CO2 and H2O) using enzymes
e.g. Respiration – glucose molecules are broken down by enzymes to form carbon dioxide and water and energy is released.
This is catabolism. Energy is released.

49. Learning check Explain Anabolism
Energy absorbed. Small  large molecules
Give an example of an anabolic reaction
Photosynthesis
Explain Catabolism
Energy released. Large  small molecules
Give an example of a catabolic reaction
Respiration

50. Catabolic Respiration Anabolic Photosynthesis
CRAP
Catabolic Respiration Anabolic Photosynthesis

51. Is catabolism the opposite of anabolism? – NO
In the examples just given the chemical processes (pathways*) involved in each of them are different, therefore catabolism is not the opposite of anabolism.
* e.g. if you travel from A to B – you followed a certain pathway. On the return journey you may come home through C – you followed a different pathway.

52. Energy Transfer Reactions
Respiration – Catabolic reaction
C6H12O6 + Oxygen  Energy + CO2 + H2O release
Photosynthesis – Anabolic reaction
CO2 + H2O + Energy  C6H12O6 + Oxygen absorbed

53. Learning check Is anabolism the opposite of catabolism ? No Why?
Different chemical pathways involved in both.