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BiochemistryCarbon and the Molecular Diversity of Life

Carbon Compounds and Life

Aside from water, living organisms consist mostly of carbon-based compounds

Carbon is unparalleled in its ability to form large, complex, and diverse molecules

A compound containing carbon is said to be an organic compound

Carbohydrates – carbon, hydrogen, oxygen

Lipids – carbon, hydrogen, oxygen

Proteins – carbon, hydrogen, oxygen, nitrogen, and sulfur in trace amounts

Nucleic acids – carbon, hydrogen, oxygen, nitrogen, and phosphorus

These molecules are often called macromolecules

Four Main Groups of Organic Molecules

Carbon atoms can form diverse molecules by bonding to four other atoms

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Hydrogen

(valence 1)

Carbon

(valence 4)Nitrogen

(valence 3)Oxygen

(valence 2)

The electron configuration of carbon gives it covalent compatibility with

many different elements

Molecular Diversity Arising from Variation in Carbon Skeletons

Carbon chains form the skeletons of most organic molecules

Carbon chains vary in length and shape

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Organic molecules consisting of only carbon and hydrogen

Organic molecules contain hydrocarbon components

Undergo reactions that release a large amount of energy

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Hydrocarbons

Butane

Functional Groups

Functional groups are the components of organic molecules that are most commonly involved in chemical reactions

The number and arrangement of functional groups give each molecule its unique properties

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Chemical Group

Hydroxyl group ( OH)

Compound Name Examples

Alcohol

Ketone

Aldehyde

Methylated

compound

Organic

phosphate

Thiol

Amine

Carboxylic acid,

or organic acid

Ethanol

Acetone Propanal

Acetic acid

Glycine

Cysteine

Glycerol

phosphate

5-Methyl cytosine

Amino group ( NH2)

Carboxyl group ( COOH)

Sulfhydryl group ( SH)

Phosphate group ( OPO32–)

Methyl group ( CH3)

Carbonyl group ( C O)

This Organic Molecule is Super Special

Adenosine triphosphate (ATP), is the primary energy-transferring molecule in the cell

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Macromolecules are polymers, built from monomers

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Unlinked monomerShort polymer

Longer polymer

Dehydration Reaction: Synthesizing a Polymer

Dehydration removesa water molecule,forming a new bond.

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Hydrolysis: Breaking Down a Polymer

Hydrolysis addsa water molecule,breaking a bond.

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Carbohydrates

Carbohydrates

Carbohydrates include sugars and the polymers of sugars

The simplest carbohydrates are monosaccharides, or simple sugars

Carbohydrate macromolecules are called polysaccharides

Carbohydrate polymers may be linear or branched

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1–2glycosidic

linkage

Glucose

Sucrose

Fructose

Glycosidic Linkage

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Linear and Ring Forms of Glucose

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Polysaccharides

Storage

• Starch (Amylose):plants

• Glycogen: animals, liver and muscle cells

• Both are stored sugars for later use

Structural

• Cellulose: plant cell walls

• Chitin: exoskeletons of arthropods, fungi cell walls

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Starch granules

in a potato tuber cell

Cellulose microfibrils

in a plant cell wall

Glycogen granules

in muscle

tissue

Cellulose

moleculesHydrogen bonds

between —OH groups

(not shown) attached to

carbons 3 and 6

Starch (amylose)

Glycogen

Cellulose

Glucose

monomer

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(c) Cellulose: 1–4 linkage of glucose monomers

(b) Starch: 1–4 linkage of glucose monomers

(a) and glucose ring structures

Glucose Glucose

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Lipids

Lipids

Lipids do not form true polymers and are hydrophobic

The most biologically important lipids are fats, phospholipids, and steroids

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Fat molecule: Triglyceride

Glycerol

Fatty acid

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Saturated and Unsaturated Fats

• Differences in saturation determine the structure and function of lipids

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Saturated Fats

• Fatty acid chains contain carbon-to-carbon single covalent bonds

• Solid at room temperature

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Unsaturated Fats

• Fatty acid chains contain at least one carbon-to-carbon double covalent bond

• Liquid at room temperature

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Phospholipids

• Composed of two fatty acid chains and a single phosphate group attached to a glycerolmolecule

• Major component of all cell membranes

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Phospholipids

Steroids

Steroids are lipids characterized by a carbon skeleton consisting of four fused rings

Cholesterol, an important steroid, is a component of animal cell membranes

Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease

Steroid hormones include estrogen, testosterone, and cortisol

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Steroid Molecule

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Cholesterol

• Cholesterol helps the lipid bilayer stay fluid in different environmental conditions

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Proteins

Proteins

Proteins account for more than 50% of the dry mass of most cells

Protein functions include defense, storage, transport, cellular communication, movement, and structural support

The properties of the amino acids of a protein determine how the protein will fold into its functional 3-dimensional structure

Protein shape determines function

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Protein Monomer: Amino Acid

• Amino acids have directionality, with an amino (NH2) terminus and a carboxyl (COOH) terminus

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New peptide

bond forming

Peptide bond

Side

chains

Back-

bone

Amino end Carboxyl endPeptide

bond

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Amino Acids to Polypeptides

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Amino acids are grouped according to the properties of their side chains (R group)

Hydrophobic (Nonpolar Side Chains)

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Amino acids are grouped according to the properties of their side chains (R group)

Hydrophilic (Polar Side Chains)

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Amino acids are grouped according to the properties of their side chains (R group)

Ionic (Electrically Charged Side Chains)

Negative Positive

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Protein Folding

• The interactions of the R groups of amino acids determine the structure and function of that region of the protein

• Proteins have primary, secondary, tertiary and quaternary structures

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Protein Structure

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Hydrogen

bond

Disulfide

bridge

Polypeptide

backbone

Hydrophobicinteractions andvan der Waalsinteractions

Ionic bond

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Enzymatic: Accelerate chemical reactions

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Defense: Protect against disease

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Storage: Store amino acids

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Transport: Transport molecules across cell membrane and within living organisms

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Hormonal: Coordination of an organism’s functions, regulate body processes

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Receptor: Response of cell to chemical stimuli

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Contractile: Movement within cells and cell parts

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Structural: Support

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Misfolded Proteins May Cause Disease

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Nucleic Acids

Nucleic Acids

There are two types of nucleic acids

Deoxyribonucleic acid (DNA)

Ribonucleic acid (RNA)

DNA provides directions for its own replication

DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis

Nucleotide Nucleotides are the monomers of nucleic acids

Consist of a nitrogenous base, a five-carbon sugar, and a phosphate group

Nucleotides are joined together by covalent bonds

Polymer: Nucleic Acid

Nucleic acids have a linear sequence of nucleotides that have ends, defined by the 3' hydroxyl and 5‘ phosphates of the sugar in the nucleotide

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Purines and Pyrimidines

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Nucleotide Pairing

• Purines pair with pyrimidines

• Number of hydrogen bonds differs between each pairing

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Directionality influences structure and function of polymers

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Structural Similarities and Differences