PROTEINS L3 BIOLOGY

FACTS ABOUT PROTEINS: Contain the elements Carbon, Hydrogen, Oxygen, and NITROGEN Polymer is formed using 20 different amino acids (monomers) What foods contain proteins?

Polypeptides are DIVERSE! Every different polypeptide has a unique combination (order) of amino acids Each Protein folds to form a unique structure that is directly related to its function. As a result, every living organism has thousands of different proteins!

Proteins are essential to the structures and functions of life 1. Structural proteins provide associations between body parts and contractile proteins are found within muscle 2. Enzymes, proteins that serve as metabolic catalysts, regulate the chemical reactions within cells Copyright © 2009 Pearson Education, Inc.

Protein Roles, cont. 3. Defensive proteins include antibodies of the immune system, and signal proteins are best exemplified by the hormones 4. Receptor proteins serve as “antenna” for outside signals, and transport proteins carry oxygen in the blood

Examples of AMINO ACIDS- what part(s) do they have in common?

3.12 Proteins are made from amino acids linked by peptide bonds Amino acids, the building blocks of proteins, have an amino group and a carboxyl group – Both of these are covalently bonded to a central carbon atom – Also bonded to the central carbon is a hydrogen atom and some other chemical group symbolized by R – the R group is the unique part of each amino acid that gives it distinct chemical properties Copyright © 2009 Pearson Education, Inc.

Carboxyl group Amino group Draw it and then build it!! Use an H for the R group

3.12 Proteins are made from amino acids linked by peptide bonds Amino acids are classified as hydrophobic or hydrophilic – Some amino acids have a nonpolar R group and are hydrophobic (water fearing!) – Others have a polar R group and are hydrophilic, which means they easily dissolve in aqueous solutions (water loving) Copyright © 2009 Pearson Education, Inc.

Leucine (Leu) Hydrophobic Serine (Ser) Hydrophilic Aspartic acid (Asp)

Carboxyl group Amino group Build it!! Use an H for the R group

3.12 Proteins are made from amino acids linked by peptide bonds Amino acid monomers are linked together to form long polypeptides – This is accomplished by an enzyme-mediated dehydration synthesis reaction – This links the carboxyl group of one amino acid to the amino group of the next amino acid – The resulting covalent linkage is called a peptide bond Copyright © 2009 Pearson Education, Inc.

How does Dehydration Synthesis link Amino Acids? (TRY it on your paper !)

Carboxyl group Amino acid Amino group Amino acid Peptide bond Dipeptide Dehydration reaction

Some animations… /bio20/mm/m7/hydrolysis/Bio20_H ydrolysis_Final.swf amino acid basics

Proteins: It’s ALL about the 3-D Structure!! Polypeptides are NOT functional molecules.  They need to FOLD correctly to become a protein that works!!!

3.13 A protein’s specific shape determines its function A polypeptide chain contains hundreds or thousands of amino acids linked by peptide bonds – The amino acid sequence causes the polypeptide to assume a particular shape – The shape of a protein determines its specific function Copyright © 2009 Pearson Education, Inc.

3.14 A protein’s shape depends on four levels of structure A protein can have four levels of structure – Primary structure – Secondary structure – Tertiary structure – Quaternary structure Copyright © 2009 Pearson Education, Inc.

3.13 A protein’s specific shape determines its function If for some reason a protein’s shape is altered, it can no longer function – Denaturation will cause polypeptide chains to unravel and lose their shape and, thus, their function – Proteins can be denatured by changes in salt concentration and pH and temperature Copyright © 2009 Pearson Education, Inc.

How does a Protein form the right structure to function? Primary – the sequence of amino acids; determined by the genes! Called the Polypeptide (not a protein!)

Protein Structure, cont. Secondary – coils and folds due to hydrogen bonding along the chain (backbone) of AA’s; -Local structure! -Alpha Helix or Beta pleated sheet

Protein Structure, cont. Tertiary – 3 D structure of the WHOLE protein; interactions among side chains (R groups) of various amino acids in the protein (hydrophilic, hydrophobic, disulfide bridges, etc); NOW it’s a PROTEIN & can get to work!

Protein structure, cont. Quarternary – multiple proteins interacting; 3D relationships of different polypeptide chains in a protein complex; This applies to SOME proteins (not all!)

Four Levels of Protein Structure Amino acids Primary structure Alpha helix Hydrogen bond Secondary structure Pleated sheet Polypeptide (single subunit of transthyretin) Tertiary structure Transthyretin, with four identical polypeptide subunits Quaternary structure

Some animations… amino acid basicsamino acid basics and protein structure imat/proteins/protein%20structure.swf ve/animations/hires/a_proteo1_h.htmlwww.learner.org/courses/biology/archi ve/animations/hires/a_proteo1_h.html

html?pop=yes&pid=815# html?pop=yes&pid=815# Annenberg Proteins video

YOU BUILD THEM!