Biological molecules

Elements that make up our body:

Carbon, Hydrogen, Oxygen, Nitrogen, Sulphur

• If an organism contains carbon, hydrogen and oxygen we can call it a biological molecule

• Nitrogen and sulphur are the additional elements that are found in proteins

The most common molecules in living things:

- Water but it is not a biological molecule

Carbohydrates  

Proteins              

Lipids                  

Nucleic acids    

• Carbohydrates contain 3 elements : C, H, O

• Lipids contain 3 elements : C, H, O

• Proteins contain 5 elements: C, H, O, N, S

• All biological molecules are large, so its called as macromolecules

• They are made of small molecules (same type or different types joining together. So, we call them polymers)

Structure of macromolecules

• The simple unit of carbohydrate is glucose (monomer)

• If 2 glucose molecules combined it's called a disaccharide    

        mono = one

        Oi = two

        poly = many

• Starch is found only in plants and glycogen is found in animals. Cellulose is present only in the cell wall of plants.

• Maltose is found in germinating seeds. Sucrose is found in table sugar. Lactose is a milk sugar.

• Storage sugar in plants is starch and the storage carbohydrate in animals glycogen.

• Starch is found in the chloroplast of a plant.

• you get energy from respiration where glucose is broken down.

• The function of a carbohydrate is to provide energy.

• Monosaccharides and disaccharides are soluble in water.

• Polysaccharides are large molecules hence insoluble in water.

• All Monosaccharides and disaccharides taste sweet but polysaccharides don't have a taste.

• 1 gram of carbohydrate releases 17 kilo joules of energy

• Glycogen is stored in the liver and muscles.

Sources of Carbohydrates:

1. Bread

2. Rice

3. Cereal

4. Potatoes

5. Pasta

Monosaccharide                Disaccharides                Polysaccharides

- Glucose                                - Maltose                            - Starch

- Fructose                               - Sucrose                           - Glycose

- Galactose                            - Lactose                           - Cellulose

• Proteins are made of long chains of amino acids.

• The monomer of proteins are amino acids.

• It is made from Hydrogen, Nitrogen, Oxygen, Carbon and Sulphur (only present in some).

• Keratin is present in your hair and nails.

• Antibodies and enzymes are examples of proteins.

• Antibodies are produced by white blood cells which are present in the blood during the time of infection.

• Haemoglobin is a soluble protein and an insoluble protein is Keratin.

Functions of Proteins

• Used to make new cells

• Used for growth and repair

• Used to make antibodies which are used to kill bacteria and viruses

• Used to make enzymes

• Some are soluble (haemoglobin) and some are insoluble (Keratin)

• Peptide bond is the bond between each amino acid molecule

Importance of Water

• It acts as a transport medium in animals and plants for transporting dissolved mediums

• Water transports amino acids and sugar up the stem and keeps the plant turgid.

• Water also plays an important role in excretion in animals. It acts as a powerful solvent for excretory materials, such as nitrogenous molecules like urea, as well as salts, spent hormones and drugs

• Plant seeds contain oil for germination

• The monomer of fats is glycerol and fatty acids

• Fats are also known as lipids

• like carbohydrates - fats contain only three kinds of atom - carbon, hydrogen and oxygen

• Fatty acids + Glycerol + Fat molecule

• All fats are insoluble in water

• When fats are liquid at room temperature we call them oil

• One gram of fat gives about 39kgs of energy

• Like carbohydrates, fats and oils can be used in a cell to release energy

• Fats are stored under the skin - Layer of cells under the skin called adipose tissue

Function of Water

• Water is a good solvent

• Chemical reactions takes place in water

• In plants, it combines with Co2 to form sugar

• In animals, it helps to break down and dissolve food molecules

• Blood is made up of cells and a liquid called plasma. Plasma is 92% water and acts as a transport medium for many dissolved substances. Blood cells are carried around the body in the plasma

Structure of DNA

• DNA comes under nucleic acid

• DNA is the chemical that carries genetic information. DNA is contained in chromosomes, which are found in the nucleus of cells.

• Within the nucleus, a thread- like structure is present called chromosomes.

• We have 23 pairs of chromosomes in our body (46)

• Chromosomes are visible only during cell division, there are 2 types : mitosis and meiosis

• The DNA molecule is made of nucleotides. Each nucleotide contains a base and a sugar phosphate backbone.

• DNA has a double nuical structure held together by chemical bonds between the bases. 

• A - Adenine, T - Thymine, G - Guranine, C - Cytosine

• A muttation is formed when the bases do not pair accordingly. A muttation occurs when unpredictable changes occurs in a person's chromosomes.

• If one chromosome is more than 46, then that child has down syndrome.

• The 4 bases in RNA are A, U (curacil), C, G

• RNA is also single stranded

• Ribose is the sugar present in RNA 

• The sequence of bases in our DNA provides a genetic code which is used to determine the kind of protein made in your cells.

• Each sequence of bases in DNA is coded for a characteristic

• 30% since it needs to be paired with A so the percentage has to be equal

• 20% as the remaining should be C, since 60% of AT has to be minused from 100% causing 40% to remain, That divided by 2 since C & G pair up.

Enzymes

• Enzymes are proteins all metabolic reactions are controlled by enzymes.

• Chemical reactions are called metabolic reactions.

• Enzymes make sure that the rate of metabolic reaction has reached the optipum level.

• A catalyst is a substance that speeds up the rate of a chemical reaction but is not itself changed by the reaction.

• Enzymes are proteins that act as biological catalysts.

• They occur inside cells or are secreted by the cells.

• All enzymes end in - ase. Catalase breaks down hydrogen peroixde. It can be found in plants and animals.

• Carbohydrases break down carbohydrates, proteases break down protiens, lipases break down fats (lipids).

• Amylase breaks down starch, maltase breaks down maltose, (glucose and guicose) sucrase breaks down sucrose (glucose and fractose).

• Examples of proteases : pepsin, trypsin

           Enzymes                      Source / Location                    Function

           Amylase                        Mouth, Intestine                              Breaks down starch

           Catalase                        Plants and animals                        Breaks down hydrogen peroxide

           Protease                        Stomach and intestine                  Breaks down proteins

• The enzyme is lipase, the substrate is lipids and the product formed fatty acids and glycerol. Lipase is formed in the pancreas.
  

• Enzymes in plants work under 28-30 degree Centigrade

Characteristics of Enzymes

1. Enzymes are proteins

2. Enzymes are specific in action

3. Enzymes are catalysts

4. Enzymes control metabolic reactions

5. Enzymes work under specific temperatures and specific pH.

Lock and key mechanism of enzymes

Substrate - is the material upon which an enzyme acts.

Active site - is the region of an enzyme where substrate molecules bind and undergo a chemical reaction

• If the shape of the substrate is complimentary to the shape of the enzyme, they react to form enzyme - substrate complex.

• The substrate later forms products, where as the enzyme stays the same

Catabolism - breakdown of larger molecules

Anabolism - synthesis of larger molecules

• Activation energy is reduced when catabolic and anabolic reaction takes place, enzymes speed up the process by reducing the activation energy.

• The rate of reaction is the speed at which substrates are converted into products.

R = amount of products / time

• Catalase is found in the liver and plants and breaks down hydrogen peroxide into water and oxygen

• Protease breaks down proteins to amino acids

• pH value, temperature can change the shape of enzymes

Temperature

Low Temperature

• At low temperatures enzyme controlled reactions go slowly because the molecules have low kinetic energy.

Optimum Temperature

• When temperature increases the reaction also increases as the molecules have more kinetic energy.

• The temperature at which the rate of reaction is fastest is known as the optimum temperature.

High Temperature

• The enzyme becomes denatured

• The enzyme changes shape and the active site no longer matches the shape of the molecule.

• Salivary amylase is present in the saliva

• It works under the pH 7.4 for sarivary amylase (alkaline)

• The stomach protease (pepsin) has a pH level of 2,one to the presence of hydrochloric acid, pepsin has to work under acidic conditions