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1. CHAPTER 4:CHEMICAL COMPOSITION OF THE CELL
2. ELEMENT IN THE CELL
There are about 92 element occurring naturally in nature.
From these 92 element, only about 25 element are needed to build living organisms.
Not all these element found in all living cell.
Main element (CHON) are the most frequently found elements in cells, forming about 96% of the human body mass.
Trace-elements are the elements are found in small quantity in cells, but are important in biological processes.
3. CHEMICAL COMPOUND IN THE CELL Chemical compounds in the cell can be divided into two major group:
Organic compounds are:
Chemical compounds contain carbon (exception are carbon monoxide, carbon dioxide, carbides and carbonates which are typically considered as inorganic)
Are usually found in and originate from living organism.
Usually consist of macromolecules (large molecules).
Inorganic compounds are:
Chemical compounds that do not contain carbon
Usually a smaller and simpler than organic compounds
Founds in cells water, acids, alkalis and mineral salts
4. There are 4 main group of organic compounds in cells:
The carbohydrates are made up of carbon, hydrogen and oxygen. The ratio of hydrogen to oxygen atoms in a molecule usually 2:1.
Many carbohydrates have the general formula CX(H2O)Y,where x is approximately equal to y.
Three basic types of carbohydrates are monosaccharide, disaccharides and polysaccharides
Monosaccharide also called simple sugar
The common monosaccharide are six-carbon sugar with a molecular formula of C6H12O6
Example of monosaccharide are glucose, fructose (fruit sugar) and galactose
Glucose is the most common monosaccharide and respiratory substrate
Monosaccharide are sweet-tasting crystalline substances which are soluble in water
Disaccharides are formed from two monosaccharide molecules combining together with the elements of a molecule of water. The chemical reaction of the formation is known as condensation.
The general formula of a disaccharides is C12H22O11
Disaccharides also called double sugar.
Disaccharides can be broken down to their constituent monosaccharide by a chemical reaction involving the addition of water. The reaction is know as hydrolysis.
7. Like monosaccharide, they are sweet-tasting crystalline substances that are soluble in water.
The most common disaccharides are maltose, lactose and sucrose.
Many monosaccharide molecules join together in a condensation reaction (with the removal of water molecules) to form a large polysaccharides molecules.
Polymerisation is the process of condensing many individual monosaccharide molecules to form a large polysaccharides molecules.
In polymerisation, the individual monosaccharide molecule are called monomers.
Polymerisation of monosaccharide forms:
Glycogen in humans and animals
Starch and cellulose in plants
13. Reducing and non-reducing sugar
Some sugars act as mild reducing agents
Two common test reagent to test for reducing sugar are:
Benedicts reagent (alkaline solution of CuSO4)
Fehlings reagent (alkaline solution of CuSO4)
c) Reducing sugars reduce Cu+ (blue solution) to Cu+ (brick red precipitate) in both reagents.
Proteins are compounds of these element: carbon, hydrogen, oxygen, nitrogen sulphur and phosphorus.
Amino acids are the subunits of all proteins.
Each amino acids carries two functional group:
A carboxyl group (- COOH) which is acidic and
An amino group (-NH2) which is basic.
COOH carboxyl group
NH2 amino group
15. Two amino acids can combine together to form a dipeptide by a condensation reaction between the carboxyl group of one and the amino group of the other. The resulting a bond liking the two amino acids that is called a peptide bond.
16. Long chains of amino acids are called polypeptides.
A polypeptide is formed by the condensation reaction of many amino acids, with the removel of water.
A polypeptide chain can also be hydrolysed, with the addition of water molecules to form individual amino acids.
Primary-linear sequence of amino acids
Secondary structure- forming ahelixor pleated sheet.
Tertiary structure- compact structure
Quaternary structure- 2 or more tertiary structure
Lipids a diverse group of substance that contain carbon, hydrogen and oxygen. The proportion of oxygen is lower than that in carbohydrates. For example, the general formula of stearic acid is C18H36O2.
All lipids are insoluble in water
Lipids dissolve readily in other lipids and in organic solvent such as ether and ethanol.
The main types of lipids are:
18. Fats and oils
Fats are solid at room temperature (20C), whereas oil are liquid
Each molecule of fats or oils is made up of one glycerol combine with three fatty acids which may be the same or may be different. Three molecule of water are remove in this condensation reaction.
19. These molecules of fats and oils are known as triglycerides.
Fats often contain only saturated fatty acids.
Oils usually contain unsaturated fatty acids.
In a saturated fatty acids, the carbon atoms are bonded to the maximum number of other atoms. Saturated fatty acid has only single bond and the hydrocarbon chain is relatively straight.
Unsaturated fatty acids has double bond in the form of CH=CH- in the hydrocarbon chain. Fatty acids; those with two or more double bond are called polyunsaturated fatty acids.
20. Fats and oils function efficiently as energy storage material. Fats and oils provide 38kJ per gram, while carbohydrates can provide only 17 kJ per gram.
Waxes are similar to triglycerides, but the fatty acids are bonded to long-chain alcohols rather than glycerol
Waxes are usually hard solids at room temperature
Waxes are used to waterproof the external surface of plants and animal. The cuticle of a leaf and the protective covering on an insects body are made of waxes.
Wax is also a constituent of the honeycomb of bees
Phospholipids have a similar structure to triglycerides but one of the fatty acids is replaced by a phosphate group
The end of the phospholipids molecule containing the phosphate group is hydrophilic. The other end containing the hydrocarbon chain of the fatty acids is hydrophobic.
The hydrophilic end is soluble in water while hydrophobic is insoluble in water.
Phospholipids bilayer from the basis of all cell membrane.
A steroid molecule has a complex ring structure
Steroid occur in plants and animals
Examples of steroids are cholesterol, testosterone, estrogen and progesterone.
24. Saturated and and saturated fats
Animal fats such as lard, butter and cream are example of saturated fats
Vegetable oil such as olive oil and sunflower oil are example of unsaturated fats.
26. ENZYMES Enzymes are protein molecules act as biological catalysts. They speed up the rate of metabolic reactions and do not chemically changed at the end of the reaction
The substance whose reactivity is increased by an enzymes is knowing as a substrate
27. THE GENERAL CHARACTERISTICS OF ENZYMES Enzymes speed up the rates of biochemical reactions in cells.
Only a small amount of enzymes is needed to catalyse a lot of substrate.
Enzymes are very specific each class of enzymes will catalyse only one particular reaction.
Enzymes are not used up or destroyed in the reactions that they catalyse, but can be reused again.
Enzymes catalyse reversible reactions
Many enzymes are only able to work with in presence of a coenzymes (or cofactor).
Enzymes are effected by changes in temperature and pH
28. NAMING OF ENZYMES An emzyme is named by taking its substrate name and adding the suffix -ase
Example, protease catalyses the hydrolysis of protein.
The -ase rule does not apply to enzymes discover before the -ase idea was introduced. For example, pepsin, rennin, ptyalin and tripsin.
The modern classification of enzymes was decided by the International Union of Biochemistry (IUB) in 1961
29. INTRACELLULAR AND EXTRACELLULAR ENZYMES Intracellular emzyme that catalyses reaction within a cell and formed by the free ribosome in the cytoplasm.
Extracellular emzyme that leaves the cell and catalyses reaction outside the cell and synthesised by ribosome attached to the rough endoplasmic recticulum.
30. MECHANISM OF ENZYMES ACTION Each enzyme molecule has a region with very precise shape called active site.
The substrate molecule fit into the active site of the enzymes like a key into a lock, forming an enzyme-substrate complex, a temporary structure.
Reaction take place at active site to form a product.
The product have a different shape from the substrate and therefore repelled from a active site.
31. THERE ARE 4 FACTORS AFFECT THE ACTIVITY OF ENZYMES
Concentration of enzyme
Concentration of substrate
The effect of pH on enzyme activity
Each enzyme has a optimum pH at which its rate of reaction is the fastest. i.e. pepsin at pH 2,(acidic) amylase pH 7 (neutral) and trypsin at pH 8-9 (alkaline)
32. The effect of temperature on enzyme activity
The rate of reaction will increase up to maximum, known as optimum temperature.
After the optimum temperature around 37C-40C, the rate of reaction falls quickly because of the bonds maintaining the structure of the enzyme start to break and the active site loses its shape.
At 60C, enzyme activity will stop altogether because the enzyme is denatured
33. The effect of substrate concentration on enzyme activity
Increase the substrate concentration will increase the chance of enzyme-substrate collision, and the rate of reaction will increase.
Addition of substrate will not increase the rate of reaction anymore because the constant enzyme concentration becomes the limiting factor.
34. The effect of enzym concentration on enzyme activity
When the concentration of enzyme increase, there are more chance enzyme-substrate collision. The rate of reaction increase linearly as long as no other factors are limiting.
THE USES OF ENZYMES
Enzyme can extracted from any living organism, and used either at home or in industry
Enzymes that are commonly used in daily life are:
Papain-found in papaya used to tenderise meat
Protease-used to tenderise meat and remove hair from the skin etc.
35. CHEMICAL COMPOSITION OF THE CELL Compound