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The chemicals of Life

The chemicals of Life. Lesson 3. Learning Focus. Describe the structure of important biochemical compound – carbohydrates, protein, lipids, and nucleic acids and explain their function within the cells

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The chemicals of Life

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  1. The chemicals of Life Lesson 3

  2. Learning Focus • Describe the structure of important biochemical compound – carbohydrates, protein, lipids, and nucleic acids and explain their function within the cells • Identify common functional groups within biological molecules, and explain their contributions to the function of each molecule. • Identify and describe the main types of biochemical reactions: oxidation-reduction, hydrolysis, and condensation • Draw 3D molecular models of important biochemical compounds.

  3. Functional groups • A group of atoms within an organic compound that give it characteristic chemical and physical properties • Are reactive clusters where much of the bonding takes place in biological molecules. • They are attached to the carbon backbone of organic molecules

  4. Bonding Capacity • The structure of each of the functional groups show that they will always form the same number of covalent bonds with adjacent molecules. Therefore bonding capacity is the number of covalent bonds an atom can form with neighbouring atoms. • Hydrogen can bond with one other molecule, oxygen and sulphur with two, nitrogen with three, carbon with four and phosphorous with five.

  5. Bonding capacity - Tip • One way to remember the bonding capacity of the 4 most common elements in order is through the acronym HONC (pronounced “HONK”). H = 1, O = 2, N = 3, C = 4

  6. Redox reactions • Reactions that involve the transfer of electrons from one reactant to another • Oxidation occurs when there is a loss of electrons, • Reduction occurs when there is a gain of electrons (important in photosynthesis and cellular respiration) • Use mnemonic: LEO GER • LEO = loss of electrons = Oxidation • GER = gain of electrons = Reduction

  7. Redox Reactions

  8. Biological Macromolecules • Most important biological molecules are macromolecules. • They are large molecules which are usually composed of many repeating subunits

  9. Condensation (dehydration synthesis) and Hydrolysis Reaction • Various molecules are assembled and disassembled the same way • Condensation and hydrolysis reactions require enzymes to take place • Involves two different types of reactions • Condensation/dehydration –removal of water this is an anabolic reaction (build up of molecules) • Hydrolysis – addition of water this is a catabolic reaction (break down of molecules)

  10. Condensation or dehydration synthesis reactions (Anabolic) • Creates a covalent bond between 2 interacting subunits, • Link the 2 subunit at their functional groups • Involves the removal of H+ from the functional group of one subunit and a OH- from the other subunit’s functional group to form water. • Reaction produce larger molecules from smaller subunits and require energy to take place.

  11. Condensation of a glucose and Fructose molecule

  12. Hydrolysis Reactions (Catabolic) • Break molecules into their subunits • It is the reverse of condensation reactions • Water molecule is used to break a covalent bond – (hydro-lysis). • Water provides an “H” to one subunit and an “OH” to the other • Energy is released during the reaction • can break a triglyceride into its subunits by breaking the ester linkages

  13. http://www.tvdsb.on.ca/westmin/science/sbioac/biochem/condense.htmhttp://www.tvdsb.on.ca/westmin/science/sbioac/biochem/condense.htm

  14. Carbohydrates • Contain C, H, and O in a 1:2:1 ratio, i.e. (CH2O)n • Most common organic materials on earth • Produced by photosynthesis • Used by organisms for energy, and building materials within the cell, • Used for cell-to-cell identification during metabolic processes • Classified into: monosaccharides, oligosaccharides and polysaccharides

  15. Monosaccharides • Are simple sugars, mono – one, saccharum – sugar • Consist of a single chain of carbon atoms with an “OH” or hydroxyl group attached • They are distinguished by their carbonyl group, either an aldehyde (functional group CH=O) or Ketone (functional group C=O) and the number of carbons in their carbon backbone • E.g. a 5-carbon chained monosaccharide is called a pentose, 6-carbon is called a hexose

  16. Monosaccharide • Glucose a monosaccharide can be linear in its dry state or forms a ring in water. • If the OH group at carbon #1, is below the plane of the ring it is called α-glucose(alpha-glucose). If the OH group is above the plane of the ring, it is called β-glucose (beta-glucose)

  17. Alpha glucose • If the OH group at carbon #1, is below the plane of the ring it is called α-glucose (alpha-glucose)

  18. Beta Glucose • If the OH group is above the plane of the ring, it is called β-glucose (beta-glucose)

  19. If the OH group is above the plane of the ring, it is called β-glucose (beta-glucose) If the OH group at carbon #1, is below the plane of the ring it is called α-glucose (alpha-glucose)

  20. Figure 3: Glucose

  21. Common Saccharides

  22. Function of Carbohydrates Simple sugars (Mono and Disaccharides) • Primary function = energy source for the cell • Produced by photosynthesis • Converted into ATP by respiration Source: http://en.wikipedia.org/wiki/Image:CellRespiration.svg

  23. Oligosaccharides • Contains 2 or 3 simple sugars bonded together. • The covalent bond linking the two molecules is a glycosidic linkage. These bonds are formed by condensation reactions • E.g. maltose (2 α-glucose molecules joined), for sucrose ( α-glucose and α-fructose joined)

  24. Condensation of 2 alpha molecules to form Maltose

  25. Polysaccharides • They are complex carbohydrate composed of hundred to several thousand monosaccharide subunits, • They are joined by glycosidic linkages. • E.g. starch and glycogen used as energy storage • Cellulose and chitin used for structural support

  26. Glycogen • Stored in small amounts in humans and other animals in muscles and liver cells • Enzymes can hydrolyze glycogen into glucose for energy during physical activity.

  27. Cellulose • Primary structural unit of plants cell walls. • Plants produce 200billion kg/yr – the most abundant organic substance on earth. • Consist of straight chain polymer of β-glucose molecules • Hydrogen bonding occurs between several straight chains to produce tight bundles called microfibrils. • Microfibrils intertwine to form tough, insoluble cellulose fibres • Humans cannot digest glycosidic linkages between β–glucose in cellulose. • We can digest starch, cellulose is a part of a healthy diet in humans

  28. Cellulose • Ruminants' have bacterial and protists in their guts that produce enzymes that break down β–glucose linkages • Therefore can digest cellulose, and use as energy source.

  29. Chitin • Makes up the exoskeleton of insects and crustaceans. • The second most abundant organic material on earth. • Use in contact lenses and biodegradable stitches.

  30. Polysaccharides • Energy storage molecules Example: • starch in plants • glycogen in animals • Structural molecules Example Cellulose = plant cell wall Chitin = Insect and Arthropod exoskeletons Source: http://en.wikipedia.org/wiki/Image:Chloroplasten.jpg Source: http://en.wikipedia.org/wiki/Image:Lyristes_plebejus.jpg

  31. Amylose Source: http://en.wikipedia.org/wiki/Image:Amylose.svg Complex carbohydrates: Examples: • Amylose (straight chain plant starch) • Amylopectin (branching plant starch) • Cellulose (plant cell walls) • Glycogen (animal starch) • Chitin (insect exoskeleton) Usually glucose molecules are bonded between C1 and C4 (straight chains). But bonding between C1 and C6 is possible (branching). Amylopectin Source: http://en.wikipedia.org/wiki/Image:Amylopektin_Sessel.svg Glycogen Source: http://en.wikipedia.org/wiki/Image:Glykogen.svg

  32. review • Textbook work for review • Page 34 #s – 2, 3, 5, 6, 8, 10

  33. Fats and Lipids • The most common energy storing molecule in organisms, 1g of fat =38kj (17kj of carbohydrates and proteins) • Excess carbohydrate is converted to fats for later energy usage. • Most common form of fat in plants and animals are Triglycerides. Fats are solid, and oils are liquid at room temp. • Lipids are hydrophobic, they are non polar, composed of C, H, O • Lipids are soluble in other non polar substances. (like-dissolves-like).

  34. Fats and Lipids • Lipids are energy storing like fats, • Used for building membranes and cell parts, • They are chemical signalling molecule because they transmit information between cells. • Also activate enzyme actions • Used as insulation layer for protection of organs • Are grouped into four: 1) fats, 2) phospholipids, 3) steroids, 4) waxes.

  35. Glycerol • It is a 3 carbon alcohol containing a hydroxyl (OH) group attached to each carbon. • Glycerol forms the backbone of triglyceride molecules.

  36. Fatty Acids • They are long hydrocarbon chains with a single carboxyl group (COOH) at one end. • They could be saturated, i.e. do not have double bonds between the carbon atoms in the chain. E.g. animal fat (butter, lard) • Mono-unsaturated – have one double bond (plant oils, e.g. oleic acid – liquid at room temp.) • Poly-unsaturated – have 2 or more double bonds. (plant oils – liquid at room temp)

  37. Page 43 diagram of stearic acid and Oleic Acid

  38. Hydrolysis of a triglyceride

  39. Phospholipids • They make up the cell membrane • Consist of a glycerol, 2 fatty acids and a polar phosphate group • Polar head is hydrophilic, • 2 non-polar tails are hydrophobic • When added to water, phospholipids form spheres called micelles

  40. phospholipids

  41. Phospholipids

  42. Steroids • Compact hydrophobic molecules made of 4 fused hydrocarbon rings, and different functional groups. • Cholesterol: important component of cell membranes and building block for other steroids in the body • High concentration of cholesterol in the bloodstream and a diet rich in saturated foods have been linked to atherosclerosis (blocking of blood vessels) which can lead to heart attack or stroke.

  43. Cholesterol

  44. Waxes • These are lipids containing long fatty acids linked to alcohols. • They are hydrophobic, firm and pliable. • Used by plants (cutin) and animals for water proofing.

  45. Proteins • They are the most diverse molecules in living organisms and among the most important • Act as structural building blocks, as functional molecules, • Involved in almost everything that a cell does • Different proteins perform specific task • More than 50% of the dry mass of cells is made up of protein • All enzymes (biological catalysts) are proteins

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