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THE CHEMICAL CONSTITUENTS OF CELLS

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

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THE CHEMICAL CONSTITUENTS OF CELLS

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  1. BIOLOGY AL Teaching Notes THE CHEMICAL CONSTITUENTS OF CELLS

  2. CONSTITUENTS INCLUDE • Carbohydrates • Lipids • Proteins • Nucleotides and Nucleic acids • Inorganic components

  3. Carbohydrates • compounds of Carbon, Hydrogen and Oxygen • source of energy in respiration • as structural materials in plants and insects • as storage materials

  4. Carbohydrates

  5. Monosaccharides • cannot hydrolyzed into simpler unit • sweet • soluble in water • can be crystallized • all are reducing sugars • e.g. Hexose and Pentose

  6. 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

  7. Pentose • Pentose such as ribose found in nucleic acid

  8. Disaccharides • made up of 2 monosaccharides joining together by glycosidic bond • sweet • soluble in water • can be crystallized • all are reducing sugars except sucrose

  9. 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

  10. Maltose • found in germination seeds • formed by condensation of two glucose compounds

  11. Polysaccharides • made up of more than 10 monosaccharides from hydrolysis • tasteless • insoluble in water • cannot be crystallized • e.g. cellulose, starch and glycogen

  12. Cellulose • found in plant cell wall only • formed by linear polymer of  glucose • molecules are arranged in bundles of parallel chains by hydrogen bonding

  13. 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

  14. Glycogen • food stored in animal • formed by polymerization of  glucose • more highly branched than starch • exist as tiny granules in cytoplasm

  15. 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

  16. 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

  17. Phospholipids • found in cell membrane • as structural components of membrane

  18. Triglycerides • As storage compounds

  19. Proteins • make up of amino acids • 3-dimensional in shape

  20. 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

  21. Amino Acids • 20 kinds of amino acids • soluble in water • insoluble in non polar solvent

  22. 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

  23. Nucleotides and Nucleic Acids

  24. Nucleotides • consist of phosphoric acid, sugar backbone and nitrogenous base • two types of nitrogenous bases: pyrimidine base and purine base

  25. Pyrimidine Bases Cytosine (C) Uracil (U) Thymine (T)

  26. Purine Bases Adenine (A) Guanine (G)

  27. Nucleic Acids • carry genetic information • determine the characteristics of an organism • are polymers of nucleotides • two types of nucleic acids: DNA and RNA

  28. Deoxyribonucleic acid (DNA) - A double helix structure of DNA - The base A pairs with T and base G pairs with C

  29. Ribonucleic Acid (RNA) - A Single strand RNA

  30. Inorganic Components • ions • water

  31. 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

  32. 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

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