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The Chemical Building Blocks of Life

Chapter 3

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Outline

• Biological Molecules– Macromolecules

ProteinsStructure and Denaturation

Nucleic AcidsDNA and RNA

LipidsFats and Phospholipids

CarbohydratesTransport and Storage

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Biological Molecules

• The framework of biological molecules consists of carbon bonded to other carbon molecules, or other types of atoms.

– Hydrocarbons consist of carbon and hydrogen.

Covalent bonds store considerable energy.

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Biological Molecules

• Functional groups– specific groups of atoms attached to

carbon backbones retain definite chemical properties

• Macromolecules.– proteins– nucleic acids– lipids– carbohydrates

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Macromolecules

• Macromolecules are often polymers.– long molecule built by linking together

small, similar subunits Dehydration synthesis removes OH and

H during synthesis of a new molecule. Hydrolysis breaks a covalent bond by

adding OH and H.

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Proteins

• Protein functions:– enzyme catalysis– defense– transport– support– motion– regulation– storage

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Amino Acids

• contain an amino group (-NH2), a carboxyl group (-COOH) and a hydrogen atom, all bonded to a central carbon atom

– twenty common amino acids grouped into five classes based on side groups

nonpolar amino acids polar uncharged amino acids charged amino acids aromatic amino acids special-function amino acids

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Amino Acids

• Peptide bond links two amino acids.– A protein is composed of one or more long

chains of amino acids linked by peptide bonds (polypeptides).

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Protein Structure

• Protein function is determined by its shape.– Protein structure

primary - specific amino acid sequence secondary - folding of amino acid chains motifs - folds or creases

supersecondary structure

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Protein Structure

tertiary - final folded shape of globular protein

domains - functional units quaternary - forms when two or more

polypeptide chains associate to form a functional protein

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Chaperone Proteins

• Chaperone proteins are special proteins which help new proteins fold correctly.

– Chaperone deficiencies may play a role in facilitating certain diseases.

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Unfolding Proteins

• Denaturation refers to the process of changing a protein’s shape.

– usually rendered biologically inactive salt-curing and pickling used to preserve

food

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Nucleic Acids

• Deoxyribonucleic Acid (DNA)– Encodes information used to assemble

proteins.• Ribonucleic Acid (RNA)

– Reads DNA-encoded information to direct protein synthesis.

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Nucleic Acid Structure

• Nucleic acids are composed of long polymers of repeating subunits, nucleotides.

– five-carbon sugar– phosphate– nitrogenous base

purinesadenine and guanine

pyrimidinescytosine, thymine, and uracil

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Nucleic Acid Structure

• DNA exists as double-stranded molecules.– double helix– complementary base pairing

hydrogen bonding• RNA exists as a single stand.

– contains ribose instead of deoxyribose– contains uracil in place of thymine

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Structure of DNA

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Lipids

• Lipids are loosely defined as groups of molecules that are insoluble in water.

– fats and oils• Phospholipids form the core of all biological

membranes.– composed of three subunits

glycerol fatty acid phosphate group

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Fats and Other Lipids

• Fats consist a of glycerol molecule with three attached fatty acids (triglyceride / triglycerol).

– Saturated fats - all internal carbon atoms are bonded to at least two hydrogen atoms

– Unsaturated fats - at least one double bond between successive carbon atoms

Polyunsaturated - contains more than one double bond

usually liquid at room temperature

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Fats as Energy Storage Molecules

• Fats, on average, yield about 9 kcal per gram versus 4 kcal per gram for carbohydrates.

– Animal fats are saturated while most plant fats are unsaturated.

Consumption of excess carbohydrates leads to conversion into starch, glycogen, or fats for future use.

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Carbohydrates

• Carbohydrates are loosely defined as molecules that contain carbon, hydrogen, and oxygen in a 1:2:1 ratio.

– monosaccharides - simple sugars– disaccharides - two monosaccharides

joined by a covalent bond– polysaccharides - macromolecules made

of monosaccharide subunits isomers - alternative forms of the same

substance

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Carbohydrate Transport and Storage

• Transport disaccharides– Humans transport glucose as a simple

monosaccharide.– Plants transform glucose into a

disaccharide transport form.• Storage polysaccharides

– plant polysaccharides formed from glucose - starches

most is amylopectin

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Structural Carbohydrates

• Cellulose - plants– alpha form or beta form of ring

• Chitin - arthropods and fungi– modified form of cellulose

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Summary

• Biological Molecules– Macromolecules

ProteinsStructure and Denaturation

Nucleic AcidsDNA and RNA

LipidsFats and Phospholipids

CarbohydratesTransport and Storage

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