1. What to expect in this lesson?
Definition of the term “Nutrition”
Biological molecules
The sources of biological molecules
The synthesis of biological molecules

2. The need for food For growth:
It provides the substances needed for making new cells and tissues
As a source of energy:
Energy drives the processes which organisms functioning (RESPIRATION)
For replacement of damaged or worn out tissue:
Millions of red blood cells need to be replaced every day
Wounds and skin need to be repaired.

3. Organic molecules contain carbon
Carbon has the unique property that it can bond to other carbon atoms.
This means the element can form large molecules which show a huge range of structures.
Organisms need these molecules to:
PROVIDE THE ENERGY TO DRIVE THE 7 LIFE PROCESSES
PROVIDE THE RAW MATERIALS FOR THE GROWTH AND REPAIR OF TISSUES
PROVIDE MOLECULES THAT CAN BE OXIDISED IN RESPIRATION AND THEREFORE ACT AS A SOURCE OF ENERGY
PROVIDE ELEMENTS AND COMPOUNDS THAT ENABLE THE RAW MATERIALS AND ENERGY TO BE USED AS EFFICIENTLY AS POSSIBLE

4. Basic Biochemistry
Organisms also contain inorganic molecules and water. The study of the interactions between the two types of molecule is called BIOCHEMISTRY.
The sum of all chemical reactions in an organism is called METABOLISM
Organisms can take molecules from their environment and rearrange them into a form they can use

5. Hydrolysis
Large organic molecules are normally made up of many smaller molecules (called subunits).
The molecules can be split in a number of ways one is HYDROLYSIS Reacting a compound with water.
STARCH can be broken down by HYDROLYSIS (catalysed by enzymes) this produces glucose sub units which are in turn reassembled into GLYCOGEN.

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7. Condensation Reactions
The sub units can then be re assembled (normally in different combinations) in CONDENSATION REACTIONS which normally produce water – hence the term.
A condensation reaction is “A chemical reaction in which two molecules combine producing a larger molecule with the elimination of a smaller molecule”

8. Condensation reactions

9. Key points
Condensation reactions convert (polymerise) smaller sub units into longer chain molecules
For example – Amino Acids into proteins
Glucose into starch or glycogen
Hydrolysis reactions convert long chain polymers into smaller sub units
For example – Proteins into Amino Acids
Starch or Glycogen into Glucose
The reaction can occur in either direction depending on the needs of the organism

10. NUTRITION
Nutrition supplies organisms with the organic molecules they need
It occurs when an organism obtains the organic substances and mineral ions.
In turn the organism is able to acquire the raw materials needed for growth and repair and to maintain its seven life processes.

11. The four classes of biological molecules
Carbohydrates
Lipids
Proteins
Nucleic Acids

12. Carbohydrates Sugar and starch are carbohydrates
They are made up carbon, hydrogen and oxygen
They are the most readily available source of energy
Glucose is the simplest carbohydrate
It is soluble in water and so is easily transported and dissolves in the cell cytoplasm
Glucose is the main energy source for living respiring cells.
In condensation reactions glucose bonds with other glucose molecules forming di, tri and poly saccharides, such as starch and glycogen

13. The digestion and Use of Carbohydrates
Digested to sugar
Hydrolysis
Glycogen stored in the liver
Oxidised in Respiration
Fat stored under the skin (subcutaneous)
Condensation

14. Sources of Carbohydrates
Potatoes
Rice
Corn
Bread
Table sugar
Jam
Biscuits (cookies)
Cakes
Fruit and vegetables

15. Lipids
Fats are solid at room temperature and oils are liquid at room temperature.
Composed of atoms of carbon, hydrogen and oxygen
They have a variety of functions:
They are a highly concentrated and convenient energy storage molecule
Waxy lipids provide a waterproofing layer
They form the protective barrier in cell membranes – i.e. between the cell content and its surroundings
They act as an concentrated energy STORE providing twice as much energy per gram as glucose
They act as an insulating layer (adipose tissue)

16. A fat Molecule Also known as tri-glycerides
Formed in a condensation reaction between 3 fatty acids and an alcohol called Glycerol
They are not soluble in water

17. Sources of Lipids Animal fats Plant fats Fruits Seeds Meat Milk Cheese
Butter
Egg yolk
Plant fats
Fruits
Seeds

18. Proteins are made of Amino Acids
A huge class of molecules which contain carbon, hydrogen, oxygen, nitrogen, and some also contain sulphur.
For proteins the function of the molecule is directly related to its shape and structure.
They are made of long chains of amino acids (Polypeptides) joined together in a particular sequence which is coded for by genes.
The sequence of amino acids determines the shape and therefore function of the protein molecule.

19. Protein Structure
There are 20 amino acids which can be joined together in a vast number of different orders – some proteins are thousands of amino acids long.
The bond between each amino acid is called a PEPTIDE LINK

20. Amino Acids
A group of water soluble molecules that have a carboxyl group –COOH and an amino group NH2 group attached to the same carbon atom called the α carbon atom
Shown by the general formula R-CH(NH2)COOH. The R group determines the property of the amino acid – it can be hydrogen or any of the organic functional groups.
Some are long and thin – Keratin the protein in hair and nails – some are spherical shaped Haemoglobin.
Amino acids are soluble and so can be transported and are assembled into proteins in the cell cytoplasm (in the ribosomes)
Plants and microorganisms can synthesise some amino acids from simple organic molecules – mammals including humans need a constant supply from the diet.
Essential amino acids have to be present but the others can be manufactured from digested protein molecules.

21. Digestion and use of Proteins
The amino acids are assimilated by condensation reactions, into the chemicals needed to build cells and tissues.
This means the amino acids are rebuilt in a specific order depending on the protein function.
Carbohydrates and fats do not perform this function.
Proteins are essential for healthy metabolism
Amino acids cannot be stored, so any excess is removed by the liver (deamination) and then converted to glycogen which is stored in the liver

22. Amino Acid Condensation Reaction

23. Sources of proteins Animal protein Plant Proteins Beans Cereals Meat
Fish
Eggs
Milk
Cheese
Plant Proteins
Beans
Cereals
Hydrolysis
Condensation

24. Nucleic Acids
Complex molecules which contain carbon, hydrogen, oxygen nitrogen and phosphorous.
Made of long chains of sub units called nucleotides.
Nucleotide
Organic molecule with N-containing purine pyrimidine base linked to a sugar (ribose/deoxyribose) there is no phosphate group – EG Adenine, thymine, guanine, cytosine
Nucleic Acid
An organic molecule with a Nitrogen containing purine or pyrimidine base linked to a sugar (ribose or deoxyribose) and a phosphate group
A Nucleotide In DNA there are four different nucleotides each has a different base and the chains are coiled around each other in a double helix shape.

25. Nucleic acids
Nucleotides

26. Nucleotides form nucleic acids
Each molecule of DNA is a long chain of nucleotides
The nucleotides are bonded together by the phosphate group
The chain is thousands of nucleotides long
The sequence of bases down the length of DNA creates a code which tells the cell which proteins to make

27. Nucleotides in a DNA molecule
Each molecule of DNA is a long chain of nucleotides
The nucleotides are bonded together by the phosphate group
The chain is thousands of nucleotides long
The sequence of bases down the length of DNA creates a code which tells the cell which proteins to make

28. A DNA molecule

29. Key points
All of these classes of compounds are essential for healthy metabolism
They are all formed from substances that we ingest as food
The food is broken down in hydrolysis reactions
The products of hydrolysis are then assimilated into new substances that the body uses in condensation reactions
We need a nutritious diet so that all of these biological molecules can be constructed.