Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 3 Lecture Slides

3.1 Polymers Are Built of Monomers Organic molecules make up the bodies of living organisms  have a carbon-based core  the core has attached groups of atoms called functional groups the functional groups confer specific chemical properties on the organic molecules

Figure 3.2 Five principal functional groups

3.1 Polymers Are Built of Monomers The building materials of the body are known as macromolecules because they can be very large There are four types of macromolecules: 1.Proteins 2.Nucleic acids 3.Carbohydrates 4.Lipids Macromolecules are actually assembled from many similar small components, called monomers  the assembled chain of monomers is known as a polymer

3.1 Polymers Are Built of Monomers All macromolecules are assembled the same way  a covalent bond is formed between two subunits by removing a hydroxyl group (OH) from one subunit and a hydrogen (H) from another subunit  because this amounts to the removal of a molecule of water (H 2 O), this process is called dehydration synthesis

Figure 3.4(a) Dehydration synthesis

3.1 Polymers Are Built of Monomers The process of disassembling polymers into component monomers is essentially the reverse of dehydration synthesis  a molecule of water is added to break the covalent bond between the monomers  this process is known as hydrolysis

Figure 3.4(b) Hydrolysis

3.2 Proteins Proteins are complex macromolecules that are polymers of many subunits called amino acids Figure 3.3(a) Polymers are built of monomers: protein

3.2 Proteins Amino acids are small molecules with a simple basic structure, a carbon atom to which three groups are added an amino group (-NH 2 ) a carboxyl group (-COOH) a functional group (R) The functional group gives amino acids their chemical identity  there are 20 different types of amino acids

Figure 3.6 Basic structure of an amino acid

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3.2 Proteins The covalent bond linking two amino acids together is called a peptide bond The assembled polymer is called a polypeptide

Figure 3.7 The formation of the peptide bond

3.2 Proteins Protein structure is complex  the order of the amino acids that form the polypeptide affects how the protein folds together  the way that a polypeptide folds to form the protein determines the protein’s function some proteins are comprised of more than one polypeptide

3.2 Proteins There are four general levels of protein structure 1.Primary structure 2.Secondary structure 3.Tertiary structure 4.Quaternary structure

3.2 Proteins Primary structure – the sequence of amino acids in the polypeptide chain This determines all other levels of protein structure Figure 3.8 Levels of protein structure: primary structure

3.2 Proteins Secondary structure – the initial folding of the amino acid chains Occurs because regions of the polypeptide that are non- polar are forced together The folded structure may resemble coils, helices, or sheets Figure 3.8 Levels of protein structure: secondary structure

3.2 Proteins Tertiary structure – the final 3-D shape of the protein The final twists and folds that lead to this shape are the result of polarity differences in regions of the polypeptide Figure 3.8 Levels of protein structure: tertiary structure

3.2 Proteins Quaternary structure – the spatial arrangement of component polypeptides in proteins comprised of more than one polypeptide chain Figure 3.8 Levels of protein structure: quaternary structure

4.2 Protein Changes to the environment of the protein may cause it to unfold or denature  increased temperature or lower pH affects hydrogen bonding, which is involved in the folding process  a denatured protein is inactive

Figure 3.9 Protein denaturation

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4.2 Proteins The shape of a protein affects its function  proteins that serve architectural and structural roles are often long and cable-like  Proteins that act as enzymes are globular, having a special 3-D shape that fits precisely with another chemical they cause the chemical that they fit with to undergo a reaction

Figure 3.10 Protein structure determines function

3.3 Nucleic Acids Nucleic acids are very long polymers that store information  comprised of monomers called nucleotides Figure 3.3(b) Polymers are built of monomers: nucleic acid

3.3 Nucleic Acids Each nucleotide has 3 parts 1.a five-carbon sugar 2.a phosphate group 3.an organic nitrogen-containing base  there are five different types of nucleotides information is encoded in the nucleic acid by different sequences of these nucleotides

Figure 3.11 The structure of a nucleotide

3.3 Nucleic Acids There are two types of nucleic acids  Deoxyribonucleic acid (DNA)  Ribonucleic acid (RNA) RNA is similar to DNA except that  it uses uracil instead of thymine  it is comprised of just one strand  it has a ribose sugar

Figure 3.12 How DNA structure differs from RNA

3.3 Nucleic Acids The structure of DNA is a double helix because  there are only two base pairs possible Adenine (A) pairs with thymine (T) Cytosine (C) pairs with Guanine (G)  the bonds holding together a base pair are hydrogen bonds  a sugar-phosphate backbone comprised of phosphodiester bonds gives support

Figure 3.13 The DNA double helix

3.3 Nucleic Acids The structure of DNA helps it to function  the hydrogen bonds of the base pairs can be broken to unzip the DNA so that information can be copied each strand of DNA is a mirror image so the DNA contains two copies of the information  having two copies means that the information can be accurately copied and passed to the next generation

3.4 Carbohydrates Carbohydrates are used for energy or sometimes as structural molecules  a carbohydrate is any molecule that contains the elements C, H, and O in a 1:2:1 ratio  the sizes of carbohydrates varies simple carbohydrates – made up of one or two monomers complex carbohydrates – long polymers Figure 3.3(c) Polymers are built of monomers: carbohydrate

3.4 Carbohydrates Simple carbohydrates are small  monosaccharides consist of only one monomer subunit an example is the sugar glucose (C 6 H 12 O 6 )  disaccharides consist of two monosaccharides an example is the sugar sucrose, which is formed by joining together two monosaccharides, glucose and fructose

Figure 3.14 The structure of glucose

3.4 Carbohydrates Complex carbohydrates are long polymer chains  because they contain many C-H bonds, these carbohydrates are good for storing energy these bond types are the ones most often broken by organisms to obtain energy  the long chains are called polysaccharides

3.4 Carbohydrates Plants and animals store energy in polysaccharide chains formed from glucose  plants form starch  animals form glycogen Some polysaccharides serve structural functions and are resistant to digestion by enzymes  cellulose is found in the cell walls of plants  chitin is found in the exoskeletons of many invertebrates and in the cell walls of fungi

Table 3.1 Carbohydrates and their functions

3.5 Lipids Lipids – fats and other molecules that are not soluble in water  lipids are nonpolar molecules  lipids include fats, phospholipids, and many other molecules Figure 3.3(d) Polymers are built of monomers: lipid

3.5 Lipids Fats are used for long-term energy storage  fats have two subunits 1.fatty acids 2.glycerol  fatty acids are chains of C and H atoms  Glycerol contains three carbons and forms the backbone to which three fatty acids are attached

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3.5 Lipids Fatty acids have different chemical properties due to the number of hydrogens that are attached to chain of carbons  if the maximum number of hydrogens are attached, then the fat is said to be saturated  if there are fewer than the maximum attached, then the fat is said to be unsaturated

Figure 3.17 Saturated and unsaturated fats

3.5 Lipids Biological membranes involve lipids  phospholipids make up the two layers of the membrane  cholesterol (a steroid) is embedded within the membrane Lipids also include oils, other steroids, rubber, waxes, and pigments Figure 3.16 Lipids are a key component of biological membranes

Inquiry & Analysis Which of the three pH values represents the highest concentration of hydrogen ions? How does pH affect the release of oxygen from hemoglobin? How Does pH Affect a Protein’s Function?