Chapter 15 Biochemistry: A Molecular View of Life Chemistry for Changing Times 10th edition Hill/Kolb Chapter 15 Biochemistry: A Molecular View of Life Daniel Fraser University of Toledo, Toledo OH ©2004 Prentice Hall

Biochemistry Chemistry of living things and life processes Cell: structural unit for all living things Cell membrane defines cell and lets material flow into and out of cell Plant cells: also have walls made of cellulose Animal cells: do not have cell walls Chapter 15

Plant Cells vs. Animal Cells Contain cell wall Contain chloroplast Large central vacuole Generally much larger in size Lack cell wall No chloroplasts Small vacuoles Tend to be smaller than plant cells Chapter 15

Plant Cells Chapter 15

Animal Cells Chapter 15

Major Internal Structures Cell nucleus: contains material that controls heredity Ribosomes: carry out protein synthesis Mitochondria: produce energy Chloroplasts: only in plant cells Convert solar energy into chemical energy Chapter 15

Metabolism Series of coordinated reactions that keeps cells alive Catabolism: reactions that break down molecules for energy Anabolism: synthesize molecules of living systems Chapter 15

Building Blocks of Organisms Carbohydrates Lipids Proteins Nucleic Acids Chapter 15

Carbohydrates Sugars, starches, and cellulose General formula: Cx(H2O)y Sugars: sweet tasting carbohydates Aldoses: aldehyde functional group Ketoses: ketone functional group Monosaccharides: simplest sugars Chapter 15

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Polysaccharides Contain two or more monosaccharides Main energy storage system: starch Plants use them for cell walls: cellulose Both are polymers of glucose Difference in way they are linked together Determines chemistry Chapter 15

Polysaccharides Chapter 15

Starch Two kinds in plants Amylose: straight chain Both made of glucose Amylose: straight chain Amylopectin: branched chain Chapter 15

Lipids Defined by solubility Fats are largest subgroup of lipids Insoluble in water Fats are largest subgroup of lipids Made up of fatty acids and glycerol Chapter 15

Some Naturally Occurring Fatty Acids Chapter 15

Saturated vs. Unsaturated Fats Saturated fats have no C=C bonds Saturated with hydrogen Unsaturated fats have C=C bonds May have more than one double bond Can add more hydrogen to fats React readily with iodine, bromine, and chlorine Chapter 15

Iodine Number Iodine Number: number of grams of iodine consumed by 100 g of fat Chapter 15

Proteins Serve as structural material for animals Required in all living cells Composed of carbon, hydrogen, oxygen, and usually sulfur Chapter 15

Amino Acids Building blocks for polymers called proteins Contain an amino group, –NH2, and a carboxylic acid, –COOH Can form zwitterions: have both positively charged and negatively charged groups on same molecule 20 required for humans Chapter 15

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Peptide Bond Connect amino acids from carboxylic acid to amino group Produce amide linkage: -CONH- Holds all proteins together Indicate proteins by 3-letter abbreviation Chapter 15

Sequence of Amino Acids Amino acids need to be in correct order for protein to function correctly Similar to forming sentences out of words Chapter 15

Structure of Proteins Four organizational levels Primary structure: amino acid sequence Secondary structure: arrangement of chains around an axis Pleated sheet Alpha helix: right-handed helix Chapter 15

Pleated Sheets Chapter 15

Alpha Helix Chapter 15

Tertiary Structure Spatial relationships of amino acids relatively far apart in protein chain Globular proteins: compact spherical shape Chapter 15

Quaternary Structure Structure when two or more amino acid sequences are brought together Hemoglobin has four units arranged in a specific pattern Chapter 15

Intermolecular Forces in Proteins Hydrogen bonding Ionic bonds Disulfide linkages Dispersion forces Chapter 15

Enzymes Biological catalysts produced by cells Nearly all are proteins Enormous catalytic power Reactions occur at lower temperatures and at higher rates Ordinarily highly specific Chapter 15

Induced-Fit Model of Enzymes Explains how enzyme works Substrate: reacting substance Active site: where chemical reaction takes place and where substrate fits Chapter 15

Cofactors Something other than polypeptide chain required by enzyme May be metal Iron in hemoglobin May be organic cofactor Coenzyme Apoenzyme: does not have cofactor Chapter 15

Inhibition of Enzymes Lets cell control when an enzyme works Inhibitor binds to allosteric site Prevents substrate from binding Chapter 15

Nucleic Acids Serve as information and control center of the cell Deoxyribonucleic acid (DNA) Carries blueprint for proteins Found in cell nucleus Ribonucleic acid (RNA) Carries out protein assembly Found in all parts of the cell Chapter 15

Nucleotides Three components Sugar Phosphate unit Nucleic acid Either ribose or deoxyribose Phosphate unit Nucleic acid Purines: two fused rings Pyrimidines: one ring Chapter 15

Nucleotides Four bases in DNA Pair up in a specific pattern Chapter 15

DNA When all base pairs are paired up with second strand – form double helix Held together by hydrogen bonding Chapter 15

RNA Tends to form single strand May pair up with itself Chapter 15

Genetic Information Chromosomes: hereditary material, concentrated in long threadlike bodies 46 in humans Made of protein and DNA Gene: basic unit of heredity Section of DNA Genome is complete set of genes for an organism Chapter 15

Information Pathway DNA mRNA tRNA ribosome protein Chapter 15

Self-Replication Occurs every time a cell divides Chapter 15

Transcription Converts DNA code to RNA Must occur before protein synthesis Can make multiple copies to make multiple copies of the protein Chapter 15

Translation Converts code on RNA into protein Read using base triplet Code for amino acids Some redundancy Chapter 15

Polymerase Chain Reaction (PCR) Method to rapidly amplify any DNA present in sample Can use very small amounts of DNA Allows for genetic testing Cut DNA into relatively small sizes Amplify it to see any pattern Chapter 15

Recombinant DNA Allows for addition of genes to organisms Make microorganisms produce useful drugs All insulin is made this way Rapidly change genetics of plants Treat genetic disorders in humans Chapter 15

Gene and plasmid are fused together with DNA ligase Plasmid and gene of interest are both treated with the same restriction enzyme to create “sticky ends” Gene and plasmid are fused together with DNA ligase Newly formed plasmid is put into a new bacterium by heat shock or electroporation Bacterium reproduces, each new clone carries a copy of the gene Purify protein encoded by the gene Chapter 15

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