“Magnified” section of protein (unfolded) The “building blocks” are amino acids Recall Enzyme (and protein) structure This is the enzyme “catalase”, the enzyme found in liver
Protein Structure • Amino acids = “Building Blocks” of proteins. • 20 different ones • Each one has • an amino group, • a carboxyl group, • and an “R-group”. • The R-group of each amino acid is unique.
“Amino group”: common to all “Carboxyl group”: common to all “R group”: each is unique
General Structure Specific Examples
Making a protein • A protein is made by linking amino acids together in the correct order (sequence). • Reaction = condensation (aka: dehydration synthesis) reaction. • Many of these reactions occur, over and over, until the protein consists of 100+ amino acids linked together. • http://www2.nl.edu/jste/proteins.htm
Your Turn! • Draw a dipeptide that consists of serine and threonine.
Dipeptide a.a. #1 a.a. #2 Hydrolysis: “Digestion” reaction
Proteins serve multiple functions in organisms • 5 Examples of Protein Function • Enzymes-protein catalysts • Hormones-protein messengers in bloodstream • Neurotransmitters-protein messengers released by neurons; allow nerve cells to “communicate” • Receptors-membrane bound proteins that bind hormones and neurotransmitters • Transporters- integral membrane proteins act as “tunnels” or bind a substance and move it either in or out of the cell.
Hormones Enzymes Transporters Receptors Neurotransmitters
In all cases, the function of the protein depends on its shape (structure) • Recall: proteins are polymers of amino acids (polypeptides) • Each amino acid has a unique “R-group” that determines its chemical nature. • Amino acids are linked together in long chains by peptide bonds. • The sequence of the a.a. and the interactions of the R-groups cause the polypeptide to fold into a specific shape.
What determines the protein’s shape? • The number of amino acids • The type of amino acids (the R-groups) • The sequence of the amino acids (what order they’re bonded in) • Examples: • Leu-gly-ala-pro • Gly-pro-leu-ala • Result: different shapes
What determines these factors? • Recall: proteins are responsible for the phenotype (appearance) of an organism. • The phenotype is determined by the genotype (genes) • What molecule contains an organism’s genes?
DNA! (The “blueprints”) • Recall: DNA is a double-helix; it consists of 2 nucleotide chains. • The nucleotide chains are made up of nucleotides. These have one of 4 nitrogen bases: ATCG • A gene is a segment of the DNA that has a specific N-base sequence. (A gene is the sequence on one side of the helix.) • The order of the N-bases of a gene determines the order of the amino acids in a protein.
Making a protein • Recall: DNA is in the nucleus (architect’s office) • Proteins are made in the cytoplasm on ribosomes (construction site). • Problem: different locations. There must be a “messenger” that takes the blueprints to the construction site. • This is the job of RNA.
http://www.dnalc.org/view/16017-Francis-Crick-1952.html • http://www.dnalc.org/view/16025-Paul-Zamecnik-1956.html • http://www.dnalc.org/view/16028-Sydney-Brenner-1961.html • http://www.dnalc.org/view/15473-The-Central-Dogma-transcription-and-translation-James-Watson.html