Proteins: Molecules with Diverse Structures and Functions Unit 3: Biochemistry Honors Biology Monkemeier

Write down these questions: Answer them on lined paper after viewing the ppt and videos Draw and label the basic structure of an amino acid. Explain how the 20 different amino acids are different from each other. Explain and describe the four levels of organization within proteins. Mention appropriate bonding and interactions and provide specific examples. Explain the role of chaperonins. List and describe the different roles that proteins play within organisms. Explain how enzymes relate to chemical reactions. Use the terms: substrate, active site, allosteric site. How do the terms denaturation and dissociation relate to enzymes. Explain the effect of each of the following have upon enzymes: temperature, pH and concentration of substrate or enzyme?

Proteins Proteins are the most diverse group of biological macromolecules, both chemically and functionally.

Functions of Proteins Functions of proteins include: Enzyme catalysis Defense Transport Support Motion Regulation Storage

Structure of Proteins Amino acids are the subunits of proteins There are 20 different amino acids. All amino acids have the same basic structure. What is different among the amino acids is the “R” Group.

Amino Acid Structure The unique character of each amino acid is determined by its “R” Group. The “R” Group also determines the chemistry of amino acids.

Each amino acid affects the shape of a protein differently, depending upon the nature of the “R” Group

Building Proteins Amino Acids are bonded together to build proteins using dehydration synthesis. The covalent bond that results from dehydration synthesis is known as a PEPTIDE BOND. When bonding together amino acids to build proteins, the carboxyl group from one amino acid has to match up with the amino group of the next amino acid. This is so that dehydration synthesis can take place.

Dehydration Synthesis and Peptide Bonds

Polypeptide A protein is composed of one or more long unbranched chains. Each chain is called a polypeptide and is composed of amino acids linked together with peptide bonds.

Proteins Have Levels of Structure The shape of a protein determines the protein’s function. The structure of proteins has traditionally been discussed in terms of a hierarchy with four levels of structure: primary, secondary, tertiary and quaternary.

Primary Structure- Amino Acid Sequence The primary structure of a protein is its amino acid sequence. If one amino acid is substituted, deleted or added to a protein, the entire protein is affected. Any alteration in the normal sequence of amino acids can have drastic effects on the function of the protein.

Secondary Structure: Hydrogen bonding patterns. Hydrogen bonds can form between the different amino acids within the polypeptide chains. Alpha helix Beta Pleated Sheets

Secondary Structure: Alpha helix

Secondary Structure: Beta pleated sheet

Tertiary Structure: Folds and Links The final folded shape of a globular protein is called a protein’s tertiary structure. Ionic bonds between oppositely charged R groups, disulfide bridges between R groups containing sulfur, and weak forces of attraction called van der Waals forces all contribute to the folding of proteins.

Tertiary Structure: Folds and Links

Quarternary Structure: subunit arrangements When two or more polypeptide chains associate to form a functional protein, the individual chains are referred to as subunits of the protein. The arrangements of these subunits is termed the quarternary structure.

Quarternary Structure

Motifs Motifs are similar substructures within proteins. Even though two proteins may be different, they may contain similar motifs, or substructures that are the same.

Domains Domains are functional units within the larger structure or tertiary structure. Metaphor Amino acids are the letters in protein language Motifs are words or phrases Domains are paragraphs

Chaperone Proteins Chaperone proteins help other proteins fold correctly. Many cells produce chaperone proteins after a cell has been exposed to high temperatures, elevated temperatures, high pH, etc. The disease Cystic Fibrosis is a hereditary disorder which affects the chaperone proteins that help a vital protein that moves ions across cell membranes fold correctly. Protein clumping in the brain that causes Alzheimer disease may also be due to faulty chaperone proteins.

Denaturation Proteins function in optimum temperature and pH ranges. When proteins are exposed to temperatures and pH ranges ABOVE their optimum range, the protein can change shape. Changing the shape of the protein affects its ability to function properly. Changing the shape of the protein denatures the protein and sometimes renders it inactive.

Upcoming Discovering Factors that affect Enzymes Lab After our long weekend - Discovering Factors which affect enzyme activity. Determine if proteins are affected by changes in pH, temperature, concentration of enzyme, concentration or substrate. Enzymes can be denatured when exposed to temperatures and pH’s outside their optimum range. Enzymes that are denatured have changed their shape.