Organic Molecules

• Molecules unique to living systems contain carbon and are referred to as organic molecules

• Carbon, needing 4 more valence electrons, forms covalent bonds (either polar or non-polar) readily with:– Carbon– Hydrogen– Oxygen– Nitrogen

• Small groups of covalently bonded atoms arranged in a very specific manner

• Parts of large compounds (carbohydrates, proteins, fats and nucleotides)

• Determine the chemical properties of large compounds (polar vs nonpolar, acid vs base)

• React with functional groups on other compounds

Functional Groups

Macromolecules

• Most of the anatomy and physiology of the body is provided by 4 different classes of organic molecules – Carbohydrates– Lipids – Proteins– Nucleic acids

• Each class consists of small molecular subunits called monomers (one unit)– smallest subunits of macromolecules that exhibit

chemical properties of the macromolecule– able to function individually or in covalently bound

groups

Monomers of Macromolecules

• Monosaccharides– basic (smallest) unit of carbohydrates (sugars)

• Amino acids– basic (smallest) unit of proteins

• Fatty acids– basic (smallest) unit of lipids (fats)

• Nucleotides– basic (smallest) unit of nucleic acids

Synthesis Reactions of Macromolecules

• Monomers can be covalently bound to one another to create a molecule gets progressively larger resulting in a polymer (many units)

• Two or more small molecules combine to form a larger one

Dehydration Synthesis

• 2 monomers are covalently bonded together to form a a new molecule that is larger and structurally more complex by the removal of a water molecule (dehydration)

Decomposition Reactions

• Large polymer molecules can be reduced down to the individual monomers by breaking the covalent bond between monomers through a decomposition reaction

Hydrolysis

• Splitting a polymer by the addition of a water molecule

Carbohydrates

• “hydrated (H2O) carbon”

• Contain carbon, hydrogen, and oxygen• Carbohydrate names end in the suffix “-ose”

– glucose, maltose, amylose, fructose, sucrose• The monomer of carbohydrates is the

monosaccharide (one sugar) of which there are a number of types – glucose is the most biologically important

• Carbon:Hydrogen:Oxygen in a 1:2:1 atomic ratio

– glucose = C6H12O6

• Because they contain oxygen, they are polar molecules (hydrophilic or lipophobic)

Monosaccharides• Simplest molecular form of carbohydrates• Three major monosaccharides

– obtained by the digestion (hydrolysis) of dietary polysaccharides

– major function is to supply a source of cellular fuel for the creation of chemical energy (adenosine triphosphate ATP)

• Structural isomers (same formula (C6H12O6), different structure

Disaccharides

• Pairs of monosaccharides covalently bonded together• Three major disaccharides

– sucrose • glucose + fructose

– lactose• glucose + galactose

– maltose• glucose + glucose

Polysaccharides• Starch (amylose)

– form of stored carbohydrates produced by plants– hydrolyzed to glucose molecules during digestion

• Cellulose– molecule that gives support to cell walls in plants

Polysaccharides

• Glycogen– form of stored carbohydrates in animal cells

Nucleic Acids

• Largest molecules in the body • Molecules of instruction and heredity• Two major classes

– deoxyribonucleic acid (DNA)– ribonucleic acid (RNA)

• The monomers of nucleic acids are nucleotides

Nucleotides• A nucleotide has 3 parts

– a nitrogen containing base (arranged in a ring(s)) – a sugar– a phosphate group

• 5 different nucleotides are used to make nucleic acids– Each nucleotide is different based on 2 criteria:

• the identity of the nitrogen base–double ringed bases are called purines

• adenine (A) and guanine (G)–single ringed bases are called pyrimidines

• cytosine (C), thymine (T) and uracil (U) • the identity of the sugar (DNA uses deoxyribose

while RNA uses ribose)• Nucleotides are covalently bound to one another

between the sugar of one nucleotide and the phosphate of another nucleotide to make long straight (linear) molecules referred to as nucleic acid strands

DNA• Double-stranded helical molecule

– looks like a ladder that has been twisted– each strand is between 100 million to 1 billion

nucleotides in length– 2 strands are held together by H-bonds between

complimentary nucleotides on opposite strands • H-bonds can only be made between a purine on

one strand and a pyramidine on the other strand–A can only bind with T–G can only bind with C–U is NOT part of DNA (only found in RNA)

• The sequence of nucleotides in one of the strands contains the genetic code

• the amino acid sequence of all proteins

Structure of DNA

RNA

• Single-stranded molecule – made from the nucleotides A, U, G and C

• Three varieties of RNA: – messenger RNA– transfer RNA– ribosomal RNA

Structure of RNA

Adenosine Triphosphate (ATP)

• Source of immediately usable energy for the cell• Nucleotide derivative bound to 3 phosphate groups

– second and third phosphate groups are attached by high energy covalent bonds• phosphate groups are negatively charged and

naturally repel each other• Enzymes that hydrolyze the high energy bond of ATP

produces releases chemical energy – ATP → ADP + P + energy

• the body can convert the ADP and P back into ATP using the energy stored in the covalent bonds of carbohydrates and lipids as a fuel

ATP

Proteins (Peptides)

• Polymer (chain) of amino acids which are bonded together through covalent bonds called peptide bonds

• 20 different amino acids are used to create proteins

Amino Acids• Each of the 20 different amino acids have similar

structural components– a central carbon atom with an attached:

• an amino (NH2) group• a carboxyl (COOH) group• a hydrogen atom

• Each amino acid unique due to the functional group located at the R position attached to the central carbon atom

Amino Acids

• The 20 amino acids can also be divided into 2 groups based on their solubility in water

• The molecular composition of the R group determines whether an amino acid is – polar– nonpolar

• The polarity of amino acids play a crucial role in determining the overall 3 dimensional structure of proteins which in turn determines its biological function

Protein Structure• The 20 different amino acids can be joined by peptide

bonds with an almost infinite number of combinations• Proteins vary greatly in size

– some are as small as 3 amino acids in length– some are as large as 34350 amino acids in length

• 4 levels of structural complexity in proteins• Primary structure

– the amino acid sequence of the protein – glutamic acid – histidine – proline is the amino acid

sequence of thyrotropic releasing hormone– determined genetically and is required for proper

protein function• a single amino acid deletion or substitution could

lead to a completely dysfunctional protein– since each protein has a unique amino acid

sequence, each protein is structurally and functionally unique

Protein Structure• Secondary structure

– simple shapes that segments of amino acids make within the protein• α helix (coiled), β-pleated sheet (folded) shapes

are held together by intramolecular hydrogen bonds between nearby amino acids

• Tertiary structure– the overall 3 dimensional shape of the protein – determined by polar and nonpolar interactions

between the amino acids of the protein and the surrounding water

– stabilized by intramolecular hydrogen bonds and disulfide bridges

• Quaternary structure– two or more separate polypeptide chains interacting

with one another to create a functional unit

Protein Conformation and Denaturation• Conformation

– overall 3 dimensional shape (tertiary/quaternary) that is required for function (activity)

– the function of some proteins requires an ability to change their conformation

• Denaturation– drastic conformational change in a protein caused

by the breaking of hydrogen bonds within a protein• increases in temperature• increases or decreases in pH

– can be partial or complete• when a protein is partially denatured, its function

is impaired• when a protein is completely denatured, its

function is lost

Protein Types and FunctionsPROTEINS PERFORM ALL BODY FUNCTIONSProteins are categorized into 2 groups• Globular proteins are water soluble and function in:

– Catalysis• enzymes speed up biochemical reactions

– Communication• hormones and neurotransmitters act as signaling

molecules between cells – Cell Membrane Transport

• channels allow substances to enter/exit cells • Fibrous proteins are insoluble in water and function in:

– Structural integrity• collagen and elastin hold body parts together

– Movement• actin and myosin allow for muscle contraction

Lipids

• Nonpolar organic molecules made mostly of carbon and hydrogen

• Energy rich molecules that can be used for energy– typically occurs when there is an absence of usable

carbohydrates in the body• Major molecule that provides structure to biological

membranes• Used as signaling molecules for communication

between cells (steroid hormones)

Fatty Acids

• Hydrocarbon chains of 4 to 24 carbon atoms (always an even number) bound to hydrogen atoms

• Has more energy per molecule than glucose• 2 different functional groups are at each end

– carboxylic acid group• provides acidic properties to the molecule

– methyl group

Types of Lipids

• The fatty acids (1, 2 or 3) may be found in the body bound to a molecule of glycerol (glucose derived molecule)– monoglyceride– diglyceride– triglyceride

Fatty Acids

• 2 different types– Saturated

• solid at room or body temperature (RT/BT)– Unsaturated

• some are solid but most are liquid at RT/BT• Saturated fatty acid

– each carbon in the hydrocarbon chain is saturated with hydrogen (bonded to 2 hydrogens)• no double bonds between carbons (C=C)

• Unsaturated fatty acid– each carbon in the hydrocarbon chain is not

saturated with hydrogen • contains at least one C=C

• Functions– energy storage in adipose (fat) tissue

• each fatty acid of a triglyceride contains approximately 4 times more energy than a single molecule of a monosaccharide (glucose)

Phospholipids

• Similar in structure to a triglyceride consisting of:– 1 glycerol– 2 fatty acids– 1 phosphate group (PO4

-) with attached nitrogen-containing group

• Amphiphilic (both loving) molecule– has BOTH polar and nonpolar portions

• Hydrophobic “tails” consist of two fatty acids • Hydrophilic “head” consists of a negatively

charged phosphate and nitrogen-containing groups

• Found in a liquid state at body temperature• Predominant molecule in cellular membranes

Phospholipid Structure

Arrangements of Phospholipids in Water

Lipid Related Molecules• The hydrocarbons in a

molecule of cholesterol are arranged in a 4 ringed structure

• Cholesterol is used to make steroid hormones including:– cortisol– aldosterone– estrogen– testosterone

• Cholesterol is an important component in cellular membranes to keep them in a fluid state