The Chemical Building Blocks of Life Chapter 3

2 How Carbon forms the framework of Biological Molecules? Biological molecules consist primarily of Carbon -carbon bonded to carbon, or -carbon bonded to other molecules. Carbon can form up to 4 covalent bonds. Carbon may be bonded to functional groups with specific properties

3 Biological Molecules Large molecules constructed from smaller subunits. Monomer: single subunit (mono = 1; -mer = unit) Polymer: many units (poly = many) Carbohydrates (sugars), nucleic acids (nucleotides), proteins (amino acids) and fats (fatty acids)

4 Making and Breaking Macromolecules Dehydration synthesis: formation of large molecules by the removal of water -monomers are joined to form polymers Hydrolysis: breakdown of large molecules by the addition of water -polymers are broken down to monomers

5 What are Isomers? Isomers are molecules with the same structural formula and exist in different forms. -Structural isomers -Stereoisomers Chiral molecules are mirror-images of each other.

6 What are Carbohydrates? Molecules with a 1:2:1 ratio of carbon, hydrogen, oxygen - empirical formula: (CH 2 O) n - examples: sugars, starch, glucose C – H covalent bonds hold much energy Carbohydrates are good energy storage molecules.

7 Carbohydrates-Monosaccharide Glucose -a monosaccharide – simple/single sugar -contains 6 carbons -very important in energy storage -fructose is a structural isomer of glucose -galactose is a stereoisomer of glucose

8 Carbohydrates-Disaccharide -2 monosaccharides linked together by dehydration synthesis -used for sugar transport or energy storage -examples: sucrose, lactose, maltose

9 Carbohydrates-Polysaccharide Polysaccharides -long chains of sugars linked by dehydration synthesis -plants use starch; animals use glycogen (for energy purposes) -plants use cellulose; animals use chitin (for structural purposes)

10 What are Nucleic Acids? Nucleic acids are polymers of nucleotides. -nucleotides: sugar + phosphate + nitrogenous base -sugar is deoxyribose in DNA or ribose in RNA -Nitrogenous bases include -purines: adenine and guanine -pyrimidines: thymine, cytosine, uracil

11 Nucleic Acids

12 Nucleic Acids

13 Ribonucleic Acids RNA -contains ribose instead of deoxyribose -contains uracil instead of thymine -single polynucleotide strand -functions: -read the genetic information in DNA -direct the synthesis of proteins

14 Other Nucleic Acids Other nucleotides -ATP: adenosine triphosphate -primary energy currency of the cell -NAD + and FAD: electron carriers for many cellular reactions

15 Proteins Proteins are polymers of amino acids. Amino acids -20 different amino acids -joined by dehydration synthesis -peptide bonds form between adjacent amino acids

16 Proteins Amino acid structure -central carbon atom surrounded by -amino group -carboxyl group -single hydrogen -variable R group

17 Proteins The structure of the R group dictates the chemical properties of the amino acid. Amino acids can be classified as: 1. nonpolar- CH2 or CH3 in their R group 2. polar- O or OH in R group 3. charged-Capable of undergoing ionization 4. aromatic-ring structures with double/single bonds 5. special function- chemical properties to form links

18 Functions of Proteins Protein functions include: 1. Enzyme are biological catalysts that lead chemical reactions 2. Defense are proteins are present in immune and endocrine systems 3. Transport molecules and ions. Example: Haemoglobin 4. Support - structural proteins like keratin in hair, fibrin in blood cloths 5. Motion proteins are actin and mysosin which help the muscles to contract 6. Regulation – Hormones serve as intercellular messengers 7. Storage- Calcium and iron bind to storage proteins as ions

19 Structure of Proteins The shape of a protein determines its function. -Primary structure – sequence of amino acids -Secondary structure – interaction of groups in the peptide backbone -a helix -b sheet

20 Proteins

21 Structure of Proteins Protein structure (continued) -Tertiary structure – folded shape of the polypeptide chain -Quaternary structure – interactions between multiple polypeptide subunits Protein folding is aided by chaperone proteins.

22 Additional structural units Motifs are common elements of secondary structure seen in many polypeptides. Domains are functional regions of a polypeptide.

23 Denaturation of Proteins Denaturation is a change in the shape of a protein. - caused by changes in the protein’s environment -pH -temperature -salt concentration -causing loss of function. -may involve complete unfolding - Renaturation is refolding into natural shape

24 What are lipids? Lipids are a group of molecules that are insoluble in water. A high proportion of nonpolar C – H bonds causes the molecule to be hydrophobic. Two main categories: -fats (triglycerides) -phospholipids

25 Types of lipids Triglycerides (fats) -composed of 1 glycerol + 3 fatty acids Fatty acids are long hydrocarbon chains which may be -saturated -unsaturated -polyunsaturated

26 Saturated and Unsaturated fats Saturated fatty acids without double bond Unsaturated fatty acid with one or more double bond

27 Triglycerides -an excellent molecule for energy storage -store twice as much energy as carbohydrates -animal fats are usually saturated fats and are solid at room temperature -plant fats (oils) are usually unsaturated and are liquid at room temperature

28 Phospholipids Phospholipids - composed of: -1 glycerol -2 fatty acids -a phosphate group Phospholipids contain polar “heads” and nonpolar “tails”.

29 Phospholipids Phospholipids spontaneously form micelles or lipid bilayers. These structures cluster the hydrophobic regions of the phospholipid toward the inside and leave the hydrophilic regions exposed to the water environment

30 Carbohydrates

31 Carbohydrates

32 Deoxyribonucleic Acid DNA -nucleotides connected by phosphodiester bonds - double helix: 2 polynucleotide strands connected by hydrogen bonds -polynucleotide strands are complementary -genetic information is carried in the sequence of nucleotides

33 Proteins

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