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65 Cards in this Set
- Front
- Back
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Changes in the levels of proteins or mutations in their structure can cause what 2 things?
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1. Altered function
2. Disease |
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What are the building blocks of proteins?
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Amino acids
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The general structure of an amino acid consists of what?
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A central alpha-carbon atom with attached carboxyl, amino, and hydrogen groups along with a specific functional group
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Depending on pH, the carboxyl and amino groups can be what?
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Charged!
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At neutral pH, amino acids are what? What does this mean?
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Zwitterions meaning they possess equal amounts of positive and negative charge.
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Why do zwitterions have equal positive and negative charge?
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Because at neutral pH, the carboxylic acid is unprotonated an the amino group is protonated
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How many amino acids are there?
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20
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What are the four groups in which Amino acids fall into?
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1. Nonpolar (hydrophobic)
2. Polar 3. Positively charged 4. Negatively charged |
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TRUE OR FALSE: Side chains on charged amino acids can contain functional groups that exhibit pH-dependent ionization.
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TRUE
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In addition to the 20 common amino acids, proteins can contain what?
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Derived amino acids which are the result of enzymatic actions on amino acids already incorporated into the protein.
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How are Proteins formed?
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Formed by the polymerization of amino acids in enzyme-catalyzed condensation reactions.
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The amino group of one peptide reacts with what?
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The carboxyl group of a second peptide eliminating a water molecule and resulting in a peptide bond.
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What is the primary structure of proteins?
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The exact linear sequence of amino acids
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Sickle cell anemia is caused by the substitution of what for what?
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Valine for glutamic acid in hemoglobin
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What can greatly alter the protein structure? Example?
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Changes in sequence like in Sickle Cell Anemia
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What is the Secondary Structure of proteins?
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The interactions within localized domains that result in a 3D arrangement (alpha helices and beta sheets)
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In the secondary structure of proteins, coiling and bending are caused by what?
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Hydrogen bonding between a carbonyl group on one amino acid and a secondary amine group on another.
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Bending of the polypeptide is constrained by what?
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The rotational angles of the covalent bonds in the chain.
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In the alpha-helix, each peptide forms what kind of bonds with what?
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Hydrogen bonds with the fourth amino acid above it and the fourth amino acid below it
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Which alpha helix is more stable: right hand or left hand spiral?
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Right handed spirals!
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How many amino acids are there per turn in an alpha helix?
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3.6
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Bonds between what two atoms constrains rotation, causing the polypeptide chain to behave as a chain of plates?
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C-N bonds
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What is a Beta-Strand?
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A region of polypeptide with an extended chain conformation.
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Beta sheets are stabilized by what?
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Hydrogen bonds between two or more beta strands
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What can cause a more random configuration in the secondary structure of proteins?
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Charge repulsion resulting from too many amino acids of like charge
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Tertiary structure refers to what?
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The 3D structure of the whole protein subunit
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What are the 4 types of chemical interactions between side chains in tertiary structures in proteins?
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1. Covalent disulfide bonds
2. Ionic interaction 3. Hydrogen bonds 4. Hydrophobic interactions |
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Covalent disulfide bonds can form between what?
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Cysteine residues
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Ionic interactions can occur between what?
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Positively charged side chains and negatively charged side chains
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Hydrogen bonds can occur between what?
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Polar amino acids and other amino acids
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Protein folding attempts to do what?
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Maximize exposure of polar groups to the aqueous environment while minimizing exposure of hydrophobic groups.
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Which kind of side chains are generally oriented toward the outside where they keep the molecule in solution and prevent aggregation?
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Polar and ionized side chains!
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Nonpolar residues are frequently dispersed among polar amino acids in order to do what?
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To minimize adverse effects because of their inability to interact with water.
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When hydrophobic amino acids are clustered on the outside, it is for what specific purpose?
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To bind to other polypeptides!
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When a charged amino acid is in the interior of the protein, it is for what specific purpose?
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Stabilizing the structure or forming an active binding site.
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Quaternary structure refers to what?
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The interactions between subunits or individual polypeptides in multichain proteins. Proteins interacting with other proteins, basically.
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What is Trypsin?
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Digestive enzyme that catalyzes the breakdown of proteins into amino acids so they can be absorbed in the intestines.
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The specificity of the enzyme trypsin results from what?
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Binding of the substrate in a particular site of the molecule
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The structure of the enzyme is organized such that the substrate-binding site has what?
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The molecular dimensions and arrangement of functional groups to mediate specific binding.
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If the secondary or tertiary structure of a protein was altered, what might happen?
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The substrate molecule might not be recognizable by the active site.
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Denaturation of the protein can result from changes in what 3 things?
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1. Temperature
2. pH 3. Ionic strength |
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What is the most abundant protein found in higher vertebrates?
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Collagen!
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Collagen is important why?
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It provides an important structural framework for most body structures including skeleton, skin, and blood vessels.
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What is the most abundant type of Collagen? How many other types are there?
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Collagen 1 is the most abundant but there are 19 total.
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What is Elastin?
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Important component of tissues like skin, blood vessels, ligaments, and lungs that require elasticity to function.
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Elastin is rich in what two types of amino acids?
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Glycine and proline
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Elastin chains are composed of what?
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Alternating segments of hydrophobic amino acids and segments rich in alanine and lysine.
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Rather than having a regular secondary structure like collagen, elastin exhibits what?
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An unordered coiled structure that is stabilized by formation of covalent cross-links between lysine residues.
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As Elastin fibers are stretched, what happens?
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the chains become aligned and the cross-links between lysine residues constrain further extension once the chains are straight
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When unloaded, elastin chains return to their original coiled states because of what?
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Because of intramolecular hydrophobic interactions.
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Multifunctionality of fibronectin is provided by what?
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Domains within the subunits having affinity for various molecules like cell surface receptors, collagen, and heparin.
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What is RGD?
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Arg-Gly-Asp is a important cell-binding tripeptide which in synergy with adjacent peptide sequences bind to specific cell surface receptors and results in cell adhesion.
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What is Fibrinogen?
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A large plasma protein that plays a critical role in blood clotting and other physiological processes.
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Fibrinogen is composed of what?
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2 identical subunits each consisting of 3 different polypeptide chains bound together in a central "disulfide knot".
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What are the three structural regions on Fibrinogen?
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1. 2 globular terminal D domains linked by
2. triple helix segments to a 3. Central E domain which contains disulfide knot |
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What are essential for the functional integrity of fibrinogen?
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Calcium ions!
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Fibronectin can be covalently linked to fibrinogen through what?
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An enzymatically catalyzed reaction between lysine residues on fibrinogen and glutamine residues on fibronectin.
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Cleavage products play important roles in what?
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Coagulation and inflammation
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The properties and functions of proteins like collagen, elastin, fibronectin, and fibrinogen are directly related to what?
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The intramolecular interactions resulting from their primary structures
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After secretion from cells, the propeptides are enzymatically cleaved from the procollagen to form what?
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Collagen!
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Collagen molecules undergo a self-assembly process to form what?
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Collagen fibrils!
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Collagen assembly results in a what?
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"Quarter-stagger" array of collagen molecules in which overlapping rows of molecules are staggered by about 1/4 of the length of an individual molecule to give collagen fibrils striations.
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What provides further stabilization of collagen structure?
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Formation of enzyme-catalyzed covalent cross-links among lysine residues!
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The highly organized structure of collagen fibrils and fibers give them what?
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High uniaxial tensile strength.
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What 4 forces stabilize protein structure? How can each type be disrupted?
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1. Hydrogen bonds - increased Temp
2. Ionic Bonds - increased [salt] or pH change 3. Hydrophobic interactions - chemicals that alter structure 4. Covalent bonds - peptide bonds cleaved by enzymatic action or disulfide bridges disrupted by reducing chemicals. |
