Enzymes, Vitamins, and Biological Molecules

• All living organisms comprise chemical compounds which come in two groups

Inorganic Compounds

• These do not contain carbon and include water and mineral salts.

Organic Compounds

• These contain a carbon skeleton and include carbohydrates, fats (lipids), proteins, and vitamins.

Water

• Water is the most abundant compound in living organisms.
• Approximately 65% of bodies consist of water.
• A water molecule has two hydrogen atoms covalently bonded to one oxygen atom, making it a polar molecule.
• Water functions in nutrition, acting as fluid in chemical reactions, a reactant in the hydrolysis of large molecules, a transport medium for nutrients, and a lubricating fluid for food movement.
• It is a fluid medium for excretion of wastes.
• Gases dissolve in water for gaseous exchange
• It provides support through turgor in plants and fluid in animals' eyes.
• It cools mammals through evaporation.

Mineral Salts

• Living organisms need variety of micro and macro nutrients act as building blocks of important cells

Carbohydrates

• Organic compounds comprise carbon, hydrogen, and oxygen, with a hydrogen to oxygen atom ratio of 2:1.
• All carbohydrates consist single sugar units known as saccharides.

Monosaccharides

• These are simple sugar units (CnH2nOn)
• They are water soluble, crystal-forming, and sweet
• They are classified by carbon atoms in the molecule.
• Triose monosaccharides have three sugars
• Pentose monosaccharides have five sugars like ribose and deoxyribose sugars
• Hexose monosaccharides have six carbon sugars, like glucose.
• Hexose sugars with the same chemical formula but different atomic arrangements are isomers.

Disaccharides

• Compound sugars are from two monosaccharides.
• Combining two hexose monosaccharides forms 12-carbon disaccharide through condensation (releasing water).
• The bond formed between the monosaccharides is a glucosidic link.
• Glucose + Glucose results in Maltose + Water (C6H12O6 + C6H12O6 → C12H22O11 + H2O)
• Glucose + Fructose results in Sucrose + Water
• Glucose + Galactose results in Lactose + Water
• Maltose, sucrose, and lactose are isomers; they are soluble but unable to pass through cell membranes.
• Breaking a dissacharide down into two monosaccharides requires adding a water molecule, and creating a process called hydrolysis
• Digestion is a series of hydrolysis processes.
• Sucrose + Water results in Glucose + Fructose (C12H22O11 + H2O → C6H12O6 + C6H12O6)

Polysaccharides

• Joining more than ten monosaccharides by condensation creates large, insoluble polysaccharide molecules.
• Starch is a polymer of glucose molecules and acts as food storage in plants, found as starch grains in plastids in plant cells in storage organs like tubers and seeds.
• Glycogen comprises chains of glucose molecules and acts as food storage in animals, stored mainly in the liver and muscles.
• Cellulose comprises long chains of glucose linked to form microfibrils, providing tensile strength and acts as structural component of plant cell walls.

Biological Importance of Carbohydrates

• They act as a main energy source for organisms.
• They are a vital form of stored food.
• Cellulose forms plant cell walls.
• Cellulose acts as roughage in mammal digestive systems.
• Pentose sugars form part of nucleic acid molecules.

Lipids

• Lipids comprise carbon, hydrogen, and oxygen, with a hydrogen to oxygen atom ratio greater than 2:1 but variable
• They are insoluble in water but dissolve in non-polar solvents like ether and chloroform.
• Each lipid molecule has one glycerol and three fatty acids.
• Glycerol has three carbon alcohol with three hydroxyl (-OH) groups.
• Fatty acids have a formula of R – C – O – H (R = molecule).
• They have a carboxyl group (-COOH) attached at one end with a carbon chain of various lengths.
• The carbon and hydrogen chain is non-polar, providing hydrophobic properties.
• Creating a lipid molecule involves condensation between the carboxyl group of fatty acids and the hydroxyl group of the glycerol, which forms an ester link that results in three water molecules produced.
• During lipid digestion, hydrolysis breaks down the lipid into three fatty and one glycerol, requiring water.

Biological Importance of Lipids

• They are a source of energy
• They act as important form of stored food
• Plant lipids are stored as oils in seeds
• Animal lipids store under the skin and around organs as adipose tissue.
• They form part of cell membranes.
• Fat stored under animal skin acts as an insulator.
• Fats form the waterproofing for plants and insects
• Fats around organs have a protective function.
• Stored fats in animals are used as a water source during drought or hibernation.
• Fats facilitate absorption of fat-soluble vitamins A and D in animal intestines.

Proteins

• Proteins are organic compounds found in living organisms that comprise carbon, hydrogen, oxygen, and nitrogen, potentially sulphur as well
• They are sensitive to temperature and pH changes
• Proteins may denature in unfavourable settings
• They act as macromolecules built from amino acid monomers.
• There are 20 known amino acids with the formula N-H, H-C-R, C=O, O-H
• Amino acids link through CONDENSATION to make dipeptides, removing a water molecule and creating a peptide link
• Dipeptides have a free amino group on one end and a free carboxyl group on the other, allowing bonding to more amino acids to form tripeptides and polypeptides.
• Joining more amino acids by condensation forms a polypeptide
• If a chain has more than 50 amino acids, then creates a protein.
• Polypeptides and proteins branch and fold into diverse shapes.
• The human body has around 50 000 different proteins

Biological Importance of Proteins

• Structural part in living protoplasm
• They form cell membranes.
• In the absence of fats and carbohydrates, proteins provide energy.
• Proteins act as buffers to maintain the pH of protoplasm.
• Nucleo-proteins form chromosomes in cell nuclei.
• Many hormones (e.g., insulin) are proteins.

Enzymes

• Organic catalysts accelerate chemical reactions without being used up by lowering the required activation energy
• Enzymes are protein molecules with protein properties
• Enzymes have a particular shape.
• Enzyme molecules have an active site of a specific shape where substrate molecules attach.
• The combined enzyme and substrate forms the enzyme-substrate complex.
• The Various bonds hold in place and the substrate molecules react together to form an enzyme-product complex after their bonds are held by enzyme
• The product splits into an enzyme and a product.
• Enzymes are unchanged during the process and can reuse.

Properties of Enzymes

• They work fast
• Enzymes do not get destroyed or change in any way
• Enzymes can catalyse in both directions

Enzymes are sensitive to temperature and pH

• Some enzymes require a co-factor
• Organic non-protein cofactors can be used as co-enzymes.
• Co-enzymes transfer atoms and chemical groups between enzymes
• NAD transfers hydrogen atoms during respiration.

Vitamins

• Organic compounds are vital for usual metabolism
• The body requires relative small amounts.
• the vitamins are fat-soluble and water-soluble.
• Fat soluble vitamins consist of A, D, E and K
• Water soluble vitamins consist of B and C.