CHAPTER 4

CHEMICAL COMPOSITION OF THE CELL

4.1 The Chemical Composition of The Cell

1. Elements form the basic building block of all matter

2. There are about 92 elements occurring naturally in nature

3. 25 elements are needed to build living organisms

4. There are main elements (CHON) that most frequently found elements in cells forming about 96% of the human body.

5. Trace elements are elements found in small quantities in cells, but are important for many biological processes. [Calcium(P), Potassium(P), Phosphorus(P), Sulphur(S), Sodium(Na), Chlorine(Cl), Magnesium(Mg) and Iron(Fe)]

Common elements found in cells

CHEMICAL SYMBOL

Hydrogen H

Carbon C

Oxygen O

Nitrogen N

6. Organic compounds : Chemical compounds that contain the element carbon.

(Except carbon monoxide, carbon dioxide, carbides and carbonates which typically considered as inorganic)

7. Inorganic compounds : Chemical compounds that do not contain carbon

8. There are 4 main groups of organic compounds in cells;

a) Carbohydrates (15%)b) Lipids (10%)c) Proteins (50%)d) Nucleic acids (18%)e) Other organic and inorganic molecules (7%)

9. Water is an inorganic compound which is composed of hydrogen and oxygen.

THE IMPORTANCE OF ORGANIC COMPOUNDS IN THE CELL

1. THE IMPORTANCE OF CARBOHYDRATES1) Glucose is the carbohydrates used to produced

energy during respiration. (major source of energy)

2) Carbohydrates used to stored energy glycogen – in animals/humanstarch - plants

3. Polysaccharides used to construct supporting structures in living organisms

a) Cellulose cell walls – in plants which support and give shape to plants

b) Chitin (modified form of glucose) – exoskeletons of crabs and insects, cell wall of fungi

4. The five-carbon sugar(ribose), form parts of the nucleotide of deoxyribonucleic acid (DNA) ribonucleic acid (RNA)

2. THE IMPORTANCE OF NUCLEIC ACIDS1.Nucleic acid are compounds of carbon, hydrogen, oxygen, phosphorus and nitrogen.2.Two types of nucleic acids :

Deoxyribonucleic acids (DNA)Ribonucleic acid (RNA)

3. Nucleotides are the basic building units of nucleic acids. 4.Each nucleotide has a nitrogen base, a sugar and a phosphate group

5. In DNA, 4 different nitrogenous bases are adenine, thymine, cytosine and guanine.

6. Two DNA strands lie alongside but upside down to each other, joining the bases.

7. Twisting the two DNA stands will give us the typical spiral staircase-like double helix DNA molecules.

8.

Nucleic acids are importance becausea)Store genetic informationb)Stable storagec)Transmission of genetic informationd)Easy to duplicate for transmission

3. THE IMPORTANCE OF PROTEINS

Importance in living organisma)Provide structure and shape such as collagen and keratinb)Movement – muscles cells contractc)Body defence system – antibodies are special proteinsd)Enzymese)hormones

f) Haemoglobing) Coagulative proteins – thrombin and

fibrinogen so that we will not bleedh) Membrane proteins /carrier proteinsi) Energy storage

4. THE IMPORTANCE OF WATER

1. Solvent – dissolves most substances2. Transport – transport dissolved substances3. Coolant – high specific heat capacity 4. Reagent – reactant for chemical reaction5. Insulator – able to absorb/release heat6. Structure and support – hydrostatic skeleton

jelly fish, earth-worm, mechanical support for plant cell