Chapter 3 Part 2 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.

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

Nucleotides 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) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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

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