The Chemical Building Blocks of Life

Chapter 3

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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

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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)

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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

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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.

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What are Carbohydrates?

Molecules with a 1:2:1 ratio of carbon, hydrogen, oxygen

- empirical formula: (CH2O)n

- examples: sugars, starch, glucose

C – H covalent bonds hold much energy

Carbohydrates are good energy storage molecules.

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Carbohydrates-MonosaccharideGlucose

-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

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Carbohydrates-Disaccharide-2 monosaccharides linked together by dehydration synthesis

-used for sugar transport or energy storage

-examples: sucrose, lactose, maltose

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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)

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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

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Nucleic Acids

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Nucleic Acids

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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

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Other Nucleic Acids

Other nucleotides

-ATP: adenosine triphosphate

-primary energy currency of the cell

-NAD+ and FAD: electron carriers for many cellular reactions

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Proteins

Proteins are polymers of amino acids.

Amino acids

-20 different amino acids

-joined by dehydration synthesis

-peptide bonds form between adjacent amino acids

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Proteins

Amino acid structure

-central carbon atom surrounded by

-amino group

-carboxyl group

-single hydrogen

-variable R group

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ProteinsThe 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

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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 cloths5. Motion proteins are actin and mysosin which help the muscles to contract6. Regulation – Hormones serve as intercellular messengers7. Storage- Calcium and iron bind to storage proteins as ions

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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

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Proteins

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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.

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Additional structural units

Motifs are common elements of secondary structure seen in many polypeptides.

Domains are functional regions of a polypeptide.

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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

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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

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Types of lipids

Triglycerides (fats)-composed of 1 glycerol + 3 fatty acids

Fatty acids are long hydrocarbon chains which may be-saturated -unsaturated -polyunsaturated

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Saturated and Unsaturated fats

Saturated fatty acids without double bond

Unsaturated fatty acid with one or more double bond

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Triglycerides

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

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Phospholipids

Phospholipids -composed of:

-1 glycerol

-2 fatty acids

-a phosphate group

Phospholipids contain polar “heads” and nonpolar “tails”.

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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

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Carbohydrates

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Carbohydrates

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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

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Proteins

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