Carbohydrates “hydrated (H 2 O) 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 = C 6 H 12 O 6 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 (C 6 H 12 O 6 ), different structure

Disaccharides Pairs of monosaccharides covalently bonded together Three major disaccharides –sucrose glucose + fructose –lactose glucose + galactose –maltose glucose + glucose

Polysaccharides Long chains of glucose form polysaccharides Starch (amylose) –form of stored carbohydrates produced by plants –the main source of dietary carbohydrates –hydrolyzed to glucose molecules in the digestive tract then distributed to all cells of the body

Polysaccharides Excess glucose in the body following the hydrolysis of dietary carbohydrates is taken up by the liver and is used to synthesize the polysaccharide glycogen –the liver gradually hydrolyzes glycogen to glucose between meals and releases it into the bloodstream for distribution to all cells of the body

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

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

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

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) –insulation prevents excessive heat loss from the body –protection provides shock absorption for organs that are surrounded by adipose tissue

Phospholipids Similar in structure to a triglyceride consisting of: –1 glycerol –2 fatty acids –1 phosphate group (PO 4 - ) 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

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

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 by the body –11 of the 20 amino acids (nonessential) can be synthesized within the body and therefore do not need to be supplied by the diet –9 of the 20 amino acids (essential) cannot by can synthesized by the body and therefore need to be obtained through hydrolysis of dietary proteins during the digestive process

Amino Acids Each of the 20 different amino acids have similar structural components –a central carbon atom with an attached: an amino (NH 2 ) 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 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 Functions PROTEINS PERFORM ALL BODY FUNCTIONS Proteins 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

Characteristics of Enzymes Enzymes are chemically specific for a particular substrate (chemical on which an enzyme acts upon) –each enzyme can only act upon one substrate Enzymes are unchanged by reactions that they catalyze and are able to repeat the process many times over Enzymes increase the rate of a chemical reaction by lowering the activation energy of the reaction Enzymes are frequently named for the type of reaction they catalyze or by their substrate Enzyme names usually end in the suffix -ase

Enzymes and Activation Energy

The region of an enzyme that recognizes a substrate is called the active site –recognizes the specific molecular structure of a substrate An enzyme temporarily binds its substrate(s) and allows the appropriate chemical reaction proceed –Synthesis –Decomposition –Exchange –RedOx Enzyme Structure and ActionAction

Enzymatic Catalysis of a Biochemical ReactionCatalysis

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

Nucleotides

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

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