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Explore the chemical constituents of cells, including carbohydrates, lipids, proteins, nucleotides, and inorganic components. Discover the structural roles, functions, and characteristics of these key cellular elements.
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BIOLOGY AL Teaching Notes THE CHEMICAL CONSTITUENTS OF CELLS
CONSTITUENTS INCLUDE • Carbohydrates • Lipids • Proteins • Nucleotides and Nucleic acids • Inorganic components
Carbohydrates • compounds of Carbon, Hydrogen and Oxygen • source of energy in respiration • as structural materials in plants and insects • as storage materials
Monosaccharides • cannot hydrolyzed into simpler unit • sweet • soluble in water • can be crystallized • all are reducing sugars • e.g. Hexose and Pentose
Hexose include glucose, fructose and galactose glucose can be found in all living cells fructose can only be found in fruit and honey Hexose Glucose Galactose
Pentose • Pentose such as ribose found in nucleic acid
Disaccharides • made up of 2 monosaccharides joining together by glycosidic bond • sweet • soluble in water • can be crystallized • all are reducing sugars except sucrose
Sucrose • found in sugar cane and beet root • formed by condensation of glucose and fructose • is non reducing as the reducing groups are involved in the glycosidic bond Sucrose
Maltose • found in germination seeds • formed by condensation of two glucose compounds
Polysaccharides • made up of more than 10 monosaccharides from hydrolysis • tasteless • insoluble in water • cannot be crystallized • e.g. cellulose, starch and glycogen
Cellulose • found in plant cell wall only • formed by linear polymer of glucose • molecules are arranged in bundles of parallel chains by hydrogen bonding
Starch • carbohydrate stored in plants • formed by polymerization of glucose • exist in helical chain form • helical chains are folded and packed to form starch grain
Glycogen • food stored in animal • formed by polymerization of glucose • more highly branched than starch • exist as tiny granules in cytoplasm
Lipids • compounds of Carbon, Hydrogen and Oxygen with smaller proportion of Oxygen than Carbohydrates • insoluble in water • soluble in non polar solvents • esters of fatty acid and glycerol
Functions of Lipids • for energy production which have higher energy value than carbohydrate and protein • as structural materials in cell membrane • as stored energy in oils and fats • as good heat insulator to reduce heat loss • as constituent of vitamin D and hormones • as solvent for fat soluble vitamins
Phospholipids • found in cell membrane • as structural components of membrane
Triglycerides • As storage compounds
Proteins • make up of amino acids • 3-dimensional in shape
Properties of Proteins • colloidal in nature which can affect osmotic potential • denature under high temperature, extreme pH and presence of certain chemicals • amphoteric, can combine with acids and alkalis to stablize pH
Amino Acids • 20 kinds of amino acids • soluble in water • insoluble in non polar solvent
Essential & Non-essential Amino Acids • man can only synthesize about 10 kinds of amino acids • non-essential amino acids are those amino acids that can be synthesized by the body • essential amino acids are those amino acids that cannot be synthesized by the body and must obtain from other sources • plants can synthesize all amino acids
Nucleotides • consist of phosphoric acid, sugar backbone and nitrogenous base • two types of nitrogenous bases: pyrimidine base and purine base
Pyrimidine Bases Cytosine (C) Uracil (U) Thymine (T)
Purine Bases Adenine (A) Guanine (G)
Nucleic Acids • carry genetic information • determine the characteristics of an organism • are polymers of nucleotides • two types of nucleic acids: DNA and RNA
Deoxyribonucleic acid (DNA) - A double helix structure of DNA - The base A pairs with T and base G pairs with C
Ribonucleic Acid (RNA) - A Single strand RNA
Inorganic Components • ions • water
The Occurrence of Ions in Cells • soluble and can effect osmotic potential • can affect pH of cytoplasm • act as metabolites in biochemical reactions • activate enzymes • be constituents of biomolecules
The Biological Significance of Water • as the main constituent of protoplasm • as medium and metabolite in many biochemical reactions • as universal solvent to dissolve substances to aid absorption, excretion and transportation