3-1 Chapter 3 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-2 Organic Chemistry All organic molecules contain carbon. – Inorganic molecules do not contain carbon. Biochemistry is the chemistry of living things.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-3 Carbon: The Central Atom Carbon is the central atom in all organic molecules. Carbon has unique bonding properties. – Can combine with other carbon atoms in long chains – Can form ring structures

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-4 Carbon: The Central Atom Carbon atoms participate in four covalent bonds. – Has four electrons in the outer energy level – Can double bond with oxygen – Can triple bond with other carbon atoms

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-5 Isomers Several factors determine the properties of an organic molecule. – The types of atoms in the molecule – The 3-D arrangement of atoms within the molecule Organic molecules can have the same number and composition of atoms, but can have different arrangements. – These are called isomers. Molecules with the same empirical formula but different structural formulas

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-6 Hexose Isomers

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-7 The Carbon Skeleton All organic molecules have a carbon skeleton. – This determines the overall shape of the molecule. Organic molecules differ in these ways: – The length and arrangement of the carbon skeleton – The kinds and location of atoms attached to it – How the attached atoms are combined together These combinations are called functional groups. Functional groups determine the chemical nature of the molecule.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-8 Functional Groups

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3-9 Macromolecules of Life Macromolecules are very large organic molecules. The most important organic compounds found in living things are: – Carbohydrates – Proteins – Nucleic acids – Lipids

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Polymers Carbohydrates, proteins and nucleic acids are polymers. Polymers are combinations of smaller building blocks. – The building blocks are called monomers. Polymers are built via dehydration synthesis. Polymers are broken apart via hydrolysis.

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Carbohydrates Organic molecules composed of carbon, hydrogen and oxygen All have the general formula CH 2 O Names end in –ose Serve as the primary energy source for most living things Also serve as structural support – Plant cell walls Important components of nucleic acids – DNA and RNA

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Simple Sugars Simple sugars are described by the number of carbons in the molecule. – Triose-3 carbons – Pentose-5 carbons – Hexose-6 carbons Examples of simple sugars: – Glucose – Fructose – Galactose

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Complex Carbohydrates When two or more simple sugars are combined, they form complex carbohydrates. – Formed via dehydration synthesis Disaccharides – Two simple sugars Sucrose Lactose Maltose Trisaccharides – Three simple sugars

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Polysaccharides Contain many simple sugars Examples of polysaccharides: – Starch and glycogen Used for energy storage in plants (starch) and animals (glycogen) – Cellulose Important component of plant cell walls Humans cannot digest cellulose; it is the fiber in our diet. – Helps facilitate movement of food through the digestive tract

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Proteins Proteins are polymers made of amino acids. An amino acid contains: – Central carbon – Amino group – Carboxyl group – Hydrogen There are 20 different amino acids.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Structure of Proteins Amino acids are joined via dehydration synthesis. – The bond formed between amino acids is called a peptide bond. Several amino acids joined together form polypeptide chains.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Primary Structure The sequence of amino acids in a polypeptide constitutes the primary structure of the protein. This sequence is dictated by information in genes (DNA). All levels of protein structure depend on the primary sequence.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Secondary Structure Polypeptides twist and fold into their secondary structure. – Some sequences of amino acids twist into a helix. This is called an alpha helix. – Some sequences of amino acids remain straight and fold back on themselves. This is called a beta-pleated sheet.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Tertiary Structure The various alpha helices and beta pleated sheets interact to form a globular structure. This globular structure is unique for each polypeptide.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Quaternary Structure Some proteins contain more than one polypeptide chain. Each of these polypeptides has its own unique tertiary structure. – These polypeptides interact to form a more complex globular structure. Quaternary structure can be stabilized by disulfide bonds.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Form and Function The protein’s overall shape determines its job. If a protein is not shaped properly, it likely will not work properly. Example: – Sickle cell anemia – A mutation in the gene causes the protein to have a different shape. – This shape change results in a change in function. Denaturation: – When heat or other environmental conditions break the bonds that stabilize tertiary structure.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Types of Proteins Structural proteins – Important in maintaining the shape of cells and organisms – Collagen Regulatory proteins – Determine what activities will occur in a protein – Enzymes and hormones Carrier proteins – Transport molecules from one place to another – Lipoproteins

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Nucleic Acids The largest biological molecules Store and transfer information within a cell Include DNA and RNA Are made of nucleotides – 5-carbon sugar – Phosphate group – Nitrogenous group

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display DNA Each DNA molecule is made of two strands. – Held together by hydrogen bonds between the nitrogenous bases – The bases pair according to base pair rules. Adenine - thymine Cytosine - guanine The two DNA strands are twisted on each other, forming a double helix. Each DNA strand is divided into segments. – Each segment forms a gene. – Genes are the recipes for proteins. The sequence of nucleotides in a gene dictate the order of amino acids in a polypeptide.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Structure of DNA

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display DNA and Chromosomes Each DNA strand has many genes. Each DNA strand is called a chromosome. Human cells have 46 chromosomes in each cell. – Each cell copies all of these chromosomes before it divides to pass along to daughter cells.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Functions of DNA DNA is able to: – Replicate itself – Store information and transmit it to offspring – Direct synthesis of proteins – Mutate (change chemically)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display The Functions of DNA

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display RNA RNA is a single-stranded molecule. Contains uracil instead of thymine Base pairs with itself and DNA – A-U – G-C RNA is found in three different forms: – mRNA (messenger RNA) – rRNA (ribosomal RNA) – tRNA (transfer RNA)

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Lipids Commonly called fats Large and nonpolar – Do not dissolve in water – Dissolve in other nonpolar molecules like acetone Usually have very few oxygen atoms There are three main types of lipids: – True fats (e.g., pork chop fat and oils) – Phospholipids (membrane components) – Steroids (most hormones)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display True (neutral) Fats Used to provide energy The building blocks of fats – A glycerol molecule – Three fatty acids

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Saturated vs. Unsaturated Lipids If the carbon skeleton of a fatty acid has as much hydrogen as possible, the fat is called a saturated fat. – Saturated fats are found in animal tissues and tend to be solid at room temperature. If the carbons of a fat have double-bonded carbon molecules in them, the fat is called unsaturated fat. – Unsaturated fats are frequently plant fats and are liquids at room temperature. – A polyunsaturated fat has several double bonds. – Fats are important energy storage molecules.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Saturated and Unsaturated Fatty Acids

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Phospholipids Are complex organic molecules that resemble fats but contain phosphate groups Phospholipids are the major components of cell membranes. – Some are known as lecithins.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Steroids Nonpolar molecules that are arranged in rings of carbon Steroids are important components of cell membranes. – Cholesterol Steroids often serve as hormones and serve in regulation of body processes. – Testosterone, estrogen

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