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General Characteristics of Biological Molecules Carbon based Interact by means of functional groups Assembled or disassembled by adding or removing water
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Biological Molecules
Mad Cow CluesIn The News
General Characteristics of Biological Molecules
• Carbon based• Interact by means of functional groups• Assembled or disassembled by adding
or removing water
Carbon and Biological Molecules
• Able to form 4 stable bonds• Organic Compounds – contain carbon• Few inorganic compounds contain carbon
C
Functional Groups• Group with distinct chemical properties
• Carbon is skeleton holding groups of atoms
• Chemical reactions within organisms involve transfer of a functional group
• Macromolecules –many functional groups
Changing Molecules• Assembling molecules
– Growth and repair– Producing molecules essential for
chemical reactions to take place
• Disassembling molecules– Digestion – Providing molecules that can enter cells
Assembly: Dehydration Synthesis
• Monomers = building blocks
• Monomers are linked with covalent bonds
• Polymers = chain-like molecules
Dehydration Synthesis• One molecule of
water is removed
• Two monomers are joined– One loses
hydroxyl group– Other loses
hydrogen
Disassembly: Hydrolysis
• Hydrolysis is opposite of dehydration
• Covalent bonds broken with addition of H2O
• Energy in bond is released
Major Classes of Biological Molecules
Carbohydrates• Contain C,H, & O• H:O = 2:1• Primary role is for energy• Breaking bonds releases energy
Glucose
Carbohydrate Example: Glucose
Monosaccharides• Simplest carbohydrates• Individual sugar molecules
Disaccharide• Monosaccharides linked together• Less readily broken during transport
Polysaccharides• Long polymers of sugars• Insoluble• Called complex carbohydrates
Common Polysaccharides
• Starches– Stored energy in
plants
• Glycogen– Animal energy
storage
Some Carbohydrates are Used for Structure
• Cellulose – plant cell wall material• Chitin – in insects, fungi
Lipids• H:O ratio higher
than 2:1
• Not dissolved in water
• Categories of lipids– Oils, fats & waxes– Phospholipids– steroids
Fats• Non-polar & insoluble• Work well for storage• More energy than equivalent
carbohydrates
• Two types of subunits– Glycerol – Fatty acids
Triglyceride• Molecule with 3 fatty acids• Includes most dietary fat
Triglycerides • Saturated – carries as many H as possible
Triglycerides • Unsaturated – double bond replaces H• Polyunsaturated – more than 1 double bond
Differences in Fats & Oils• Polyunsaturated
– Plant oils– Fish oils
• Saturated– Animal fats
• There are exceptions
Waxes• Chemical backbone differs from fats & oils
• One carbon chain
• Water resistant
Phospholipids• Phosphate group replaces a fatty acid • Key component of cell membrane
Steroids• With 4 carbon rings• Important for membranes
Proteins• Transport other molecules• Provide for muscle contraction• Help protect body• Play role in nerve transmission• Control growth• Serve as enzymes• Act as chemical messenger
Protein Structure• Chain of amino acids• Polypeptide bond
Protein Synthesis & Hydrolysis
Protein Levels of Structure• Primary structure = amino acid sequence
• Secondary structure = shape– Coils– Folds
• Tertiary structure = complex shape caused by hydrogen bonds
Protein Function• Dependent upon 3-dimensional structure• Can be degraded by heat
Nucleic Acids• Composed of nucleotides• Stores information
Forms of Nucleic Acid• DNA = deoxyribonucleic acid• RNA = ribonucleic acid
End Chapter 4
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