What to expect in this lesson?

• Definition of the term “Nutrition”

• Biological molecules

• The sources of biological molecules

• The synthesis of biological molecules

The need for foodFor 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.

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:

1. PROVIDE THE ENERGY TO DRIVE THE 7 LIFE PROCESSES

2. PROVIDE THE RAW MATERIALS FOR THE GROWTH AND REPAIR OF TISSUES

3. PROVIDE MOLECULES THAT CAN BE OXIDISED IN RESPIRATION AND

THEREFORE ACT AS A SOURCE OF ENERGY

4. PROVIDE ELEMENTS AND COMPOUNDS THAT ENABLE THE RAW MATERIALS

AND ENERGY TO BE USED AS EFFICIENTLY AS POSSIBLE

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

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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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”

Condensation reactions

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

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.

The four classes of biological molecules

CarbohydratesLipids

Proteins Nucleic Acids

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

The digestion and Use of Carbohydrates

Oxidised in Respiration

Digested to sugar

Glycogen stored in the liver

Fat stored under the skin (subcutaneous)

Hydrolysis

Condensation

Sources of Carbohydrates

• Potatoes • Rice• Corn• Bread• Table sugar• Jam• Biscuits (cookies)• Cakes• Fruit and vegetables

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: 1. They are a highly concentrated and convenient energy storage molecule2. Waxy lipids provide a waterproofing layer3. They form the protective barrier in cell membranes – i.e. between the

cell content and its surroundings4. They act as an concentrated energy STORE providing twice as much

energy per gram as glucose5. They act as an insulating layer (adipose tissue)

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

Sources of Lipids

• Animal fatsI. MeatII. Milk III. CheeseIV. ButterV. Egg yolk

• Plant fatsI. Fruits II. Seeds

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.

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

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.

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

Amino Acid Condensation Reaction

Sources of proteins

Animal protein• Meat • Fish • Eggs • Milk• Cheese

Plant Proteins• Beans • Cereals

Hydrolysis

Condensation

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.

Nucleic acids

Nucleotides

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

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

A DNA molecule

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.