The Chemistry of Life

Part Two

ProteinsElements• C, H, O, N, STypes• All proteins are long chains of amino acids.

Changes in amino acid order create enormous variation.* Even more complexity arises when proteins fold and combine with other proteins.

Functions1. Part of the cell membrane (for transport, etc.)2. Provide support and shape to cells3. Hormones to send chemical messages4. Speed chemical reactions (as enzymes)5. Energy supply

ProteinsMonomerAmino acids act as monomers in protein synthesis. There are 20 standard amino acids.

PolymerAmino acids are added together. Because water is a byproduct, this is called dehydration synthesis or condensation.

Amino Group

Carboxylic Acid Group

Side Chain

Peptide BondA molecule of water is removed from two

amino acids to form a peptide bond

…

Amino Acids (six of twenty)

Glycine Alanine Valine

Leucine Methionine Isoleucine

Twenty Standa

rd Amino Acids

A small protein (polypeptide)

Nucleic AcidsElements• C, H, O, N, PTypes• DNA

(deoxyribonucleic acid)

• RNA (ribonucleic acid)

Functions1. Stores genetic

blueprint as DNA2. RNA is used as the

blueprint for proteins

base pairs

Adenine Thymine

Guanine Cytosine

Sugar phosphate backbone

Nucleic AcidsMonomerNucleotides are monomers made of 3 parts: phosphate, sugar, nitrogenous base. The sugar is ribose in RNA and deoxyribose in DNA.

PolymerNucleic acids form when many nucleotides join. Only certain pairings of bases occur: adenine (A) with thymine (T), cytosine (C) with guanine (G).In RNA, thymine is replaced with uracil (U).As with amino acids, different combinations of nucleotides allows for enormous variety.

Phosphate group

Sugar

Nitrogenous base

Nucleic Acids

P – phosphateS – sugar

(deoxyribose)A – AdenineT – ThymineC – CytosineG – Guanine

To form a large DNA polymer, nucleotides join via dehydration synthesis

Nucleotide

Sugar-phosphate backbone

base pairs

Hydrogen bonds

Sugar-phosphate backbone

Base pair

Part Two Answers: 1 – 101. F – nucleic acids (& some lipids) have N (6) 2. T – proteins are used as an energy source (2) 3. T – “there are 20 standard amino acids” (3)4. T – look at the six examples: one has S (4)5. F – notice the general formula contains N (3)6. F – proteins can range from a few amino

acids to thousands. “A small protein” suggests that many proteins are larger (5)

7. T – amino acid monomers join to form protein polymers (3)

8. F – only DNA stores genetic information (6)9. T – this is true for all monomers (3)10. T – this is true for all monomers (8)

Part Two Answers: 11 – 2011. F – enzymes are proteins (2)12. T – all nucleotides have a phosphate group,

sugar, & base; the sugar in RNA is ribose (7)13. F – adenine does not pair with cytosine (7)14. T – adenine pairs with thymine (7,8)15. F – most hormones are proteins (or lipids) (2)16. F – although proteins and lipids are found in

membranes, nucleic acids are not (6)17. F – U (i.e. uracil) is only in RNA, not DNA (7)18. T – the “backbone” is phosphate and sugar;

the “steps” are the nitrogenous bases (6,8)19. T – polymers form from many monomers

(3...)20. F – RNA = ribonucleic acid (6)

Answers: 1 – 2C O H P S N

carbohydrateslipidsproteinsnucleic acids

x

1.

x x x x x (x) (x)

x x x (x) x x x x x x

Monomers Polymerscarbohydrates

lipidsproteinsnucleic acids

fructose, glucose

2. cellulose, chitin

glycogen, starch, polysaccharide

fatty acid, glycerol triglycerideamino acids

nucleotide

polypeptideDNA, RNA

Answers: 4

O

NH2

SHO

NH

OHCH3O

NH

O

NH

CH3O

NH

CH3 CH3

OH

A) lipid B) carbohydrate

C) nucleic acid

E) lipidD) carbohydrate

F)protein

Answers: 3 – 53. Lipids (triglycerides and phospholipids)

are made from glycerol.4. A) lipid (triglyceride)

B) carbohydrate (disaccharide)C) nucleic acidD) carbohydrate (monosaccharide)E) lipid (steroid)F) protein

5. Saturated fatty acids have only C-C single bonds (saturated with H), which means they are straight and more likely to form solid fats.Unsaturated fatty acids have at least one C=C double bond, are bent, and tend to form oils.

Answers: 66. a) proteins

b) lipidsc) lipidsd) carbohydratese) proteinsf) proteinsg) carbohydratesh) nucleic acidsi) nucleic acidsj) lipidsk) nucleic acids

Answers: 7 – 117. A monosaccharide (e.g. glucose) is a single

monomer, whereas a disaccharide (e.g. sucrose) contains two monomers.

8. A phosphate group, a sugar (deoxyribose or ribose), and a nitrogenous base (adenine, cytosine, guanine, thymine, or uracil).

9. A C A G G T C G T A A C | | | | | | | | | | | | T G T C C A G C A T T G

10. Yes, because A is always paired with T.11. 20 % A (same as T), 30% C, 30% G (all must

add to 100%; C and G must be the same).