Biological Macromolecules A B C D Carbohydrates Lipids

Biological Macromolecules A. B. C. D. Carbohydrates Lipids Proteins Nucleic acids

A. Carbohydrates General properties – Composed mostly of carbon, hydrogen, and oxygen – Large number of –OH groups attached to the carbons – Functions • Energy source for living cells • Certain structural components of cells

A. Carbohydrates Monosaccharides – “Simple sugars” – Monomer unit of carbohydrate group – Examples: glucose, fructose Disaccharides – Composed of two monosaccharide units joined together – Examples: sucrose, lactose Polysaccharides – Composed of multiple monosaccharide units (100 s – 1000 s)

B. Lipids General properties – Biological compounds with hydrophobic components in their molecular structures – Functions • Energy storage • Structural components Glycerides – A major class of lipid – Composed of a glycerol molecule attached to one, two, or three fatty acid molecules

B. Lipids – Generalized structure of a triglyceride:

B. Lipids Fatty acid saturation – Fatty acids with greater saturation have fewer C=C double bonds; Have higher melting points – Fatty acids with less saturation have more C=C double bonds; Have lower melting points

B. Lipids Phospholipids – A lipid molecule (for example, a diglyceride) with a hydrophilic group attached via a phosphate linkage – Found in membrane structure (details later in course) Other lipids – Sterols: cholesterol and steroid hormones – Waxes

C. Proteins General properties – Composed of chains of amino acids – There are 20 different amino acids, each with distinctive chemical properties – A protein molecule may contain several hundred amino acids – Each different protein has its own order, or “sequence, ” of amino acids – The correct sequence of amino acids is essential for the protein’s function

C. Proteins Functions – Enzymes: enzymes are biological catalysts that control almost every reaction in living systems – Cellular recognition and communication – Structural components of living cells

C. Proteins Amino acid structure – To the central carbon atom, four things are attached: • • Hydrogen atom Amino group Carboxylic acid group Side chain “R” group – Twenty different “R” groups, with different chemical properties

C. Proteins Peptides – Chains of amino acids attached by peptide bonds – May be named by number of amino acids: dipeptide, tripeptide, tetrapeptide, pentapeptide, etc. ; Polypeptide

C. Proteins Protein: – A polypeptide chain with a specific biological function – Most proteins have from about 50 up to several hundred amino acids in their structure

C. Proteins Levels of protein structure – Primary structure: amino acid sequence – Secondary structure: localized folding of a chain into regions of helix or sheet structure – Tertiary structure: folding of a single polypeptide chain into a three-dimensional structure – Quaternary structure: only in proteins with more than one polypeptide chain; Folding

D. Nucleic Acids General properties – Composed of chains of nucleotides – There are 4 different nucleotides – A nucleic acid molecule may contain several thousands or millions of nucleotides – Each nucleic acid molecule has its own order, or “sequence, ” of nucleotides – The correct sequence of nucleotides is essential for the nucleic acid’s function

D. Nucleic Acids Overall function. • The sequence of nucleotides in a nucleic acid molecule serves as a blueprint to encode the correct sequence of amino acids for a protein. The code for a specific protein is called a “gene. ” • Deoxyribonucleic acid (DNA): DNA molecules (chromosomes) serve as the “master blueprint” for all of the cell’s proteins. The DNA molecules are transmitted to offspring during reproduction. • Ribonucleic acid (RNA): RNA molecules serve as “working copies” of the genes for the proteins that the cell is making at any given

D. Nucleic Acids Nucleotide structure – A nucleotide consists of: • Nitrogenous base • Pentose sugar • Phosphate group – Nitrogenous bases: • Purines: adenine & guanine • Pyrimidines: cytosine, thymine (in DNA), & uracil (in RNA) – Pentose sugars: • Ribose (found in RNA) • Deoxyribose (found in DNA)