Chapter 19 – Flashcards with Answers
75 test answers
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| what are the amino acids found in proteins called? |
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| alpha amino acids |
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| why are they called alpha amino acids> |
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| because they are attached to the alpha carbon |
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| what is the alpha carbon? |
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| the carbon next to the carboxylate group |
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| what gives an amino acids its unique characteristics |
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| the R group (or side chain) |
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| what four categories are amino acids broken up into? |
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| neutral with nonpolar side chains, neutral with polar side chains, basic side chains and acidic side chains |
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| acidic side chains contain a (blank) group |
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| carboxylate |
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| basic side chains contain an (blank) group |
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| amino group |
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| what is the simplest amino acid |
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| glycine |
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| with the exception of glycine, what is true of the alpha carbons in amino acids? |
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| they are chiral |
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| are most amino acids found in the D or L form? |
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| L |
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| what is a zwitterion? |
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| a dipolar ion that carries both a positive and negative charge as a recult of an internal acid-base reaction in an amino acid molecule |
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| what is the net charge of a zwitterion? |
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| zero |
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| what happens to a zwitterion if an acid is added? |
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| then the COO- picks up a hydrogen |
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| what happens to a zwitterion if a base is added? |
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| then the amino group loses a hydrogen |
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| what is the isoelectric point? |
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| the pH at which the zwitterion forms |
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| what is the only sulfhydryl containing amino acid? |
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| cysteine |
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| what chemical property do cysteine have that other amino acids don't? |
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| they are able to be oxidized to form a disulfide bond |
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| what is the product of oxidizing a cysteine? |
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| a disulfide compound, cystine |
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| what functional group reacts when two amino acids are put together? |
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| the carboxylate group |
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| what are dipeptides? |
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| compounds made up of two amino acids |
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| what kind of bonds peptide bonds? |
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| amide linkages |
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| does the order amino acids are in matter? |
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| yes |
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| alyclalamine and alanylglycine are (blank) isomers of each other. |
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| structural |
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| peptide |
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| an amino acid polymer of short chain length. |
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| polypeptide |
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| an amino acid polymer of intermediate chain length containing up to 50 amino acid residues |
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| protein |
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| an amino acid polymer made up of more than 50 amino acids |
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| amino acid residue |
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| an amino acid that is part of a peptide, polypeptide or protein chain |
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| N-teminal residue |
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| an amino acid on the end of a chain that has an unreacted or free amino acid |
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| C-terminal residue |
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| an amino acid on the end of a chain that has an unreacted or free carboxylate group |
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| which side is the N-terminal on? |
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| the left |
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| disulfide bridge |
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| a bond produced by the oxidation of -SH groups on two cysteine residues. The bond loops or holds two peptide chains together. |
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| what is the difference in the structure of vasopressin and oxytocin? |
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| two amino acids |
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| are proteins relatively large or small molecules? |
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| large |
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| what is one of the most important properties of proteins that is based on its R group? |
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| acid base behavior |
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| what determines at what pH a protein will clump together? |
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| the charge on the R group |
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| name eight functions of proteins in the body: |
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| catalysts, structural, storage, protective, regulatory, nerve impulse transmission, movement, and transport |
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| what are two types of proteins that are based on their structural shape? |
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| fibrous and globular |
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| fibrous proteins |
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| made up of long rod shaped molecules that can intertwine with one another and form strong fibers. |
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| are fibrous proteins water soluble? |
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| no |
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| where are fibrous proteins usually found? |
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| tissue, hair and skin |
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| globular proteins |
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| more spherical |
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| are globular proteins soluble in water? |
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| yes, they either dissolve or form colloidal dispersions in water |
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| what are the two types of proteins based on composition? |
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| simple and conjugated |
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| simple proteins |
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| contain only amino acid residues |
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| conjugated proteins |
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| contain amino acid residues and other organic or inorganic compounds |
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| prosthetic group |
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| the non amino acid parts of conjugated proteins |
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| what do all proteins have in common? |
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| carbon nitrogen backbone |
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| what does the primary structure of a protein tell you? |
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| the order in which amino acid residues are linked together |
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| what causes a protein chain to fold and curl into distinctive shapes that in turn enables the protein to function properly. |
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| the sequence of amino acids |
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| when a primary structure folds and becomes aligned in a certain orderly pattern, this is called... |
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| secondary structure |
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| what kind of bonding makes secondary structures? |
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| hydrogen |
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| what are the two forms secondary structures can take? |
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| alpha helix and beta sheets |
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| in an alpha helix, what compounds are hydrogen bonded? |
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| the carbonyl oxygens and amide hydrogens |
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| are all amide groups or all carbonyl oxygens involved in hydrogen bonding? |
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| all amide groups |
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| what is the less common structure: alpha helix or beta sheets |
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| beta sheets |
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| where is the only place beta sheets are found extesively? |
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| silk proteins |
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| what are hydrogen bonded in beta sheets? |
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| the amide carbonyl oxygens and amide hydrogens |
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| what is tertiary structure? |
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| the bending and folding of the protein into specific three dimensional shape. |
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| the tertiary structure results from the interactions between |
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| the R side chains and the amino acid residues |
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| what are the four types of R group interactions |
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| disulfide bridges, salt bridges, hydrogen bonds, and hydrophobic interactions |
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| what two residues can a disulfide linkage occur between |
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| cysteine |
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| are disulfide linkages present in secondary structures? |
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| no |
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| what are salt bridges? |
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| a result of ionic bonds that form between the ionized side chain of an acidic amino acid and the side chain of a basic amino acid |
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| what is the difference between the hydrogen bonds of the tertiary structure and the hydrogen bonds of the secondary structure? |
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| in the secondary structure the bonding is between backbone carbonyl and amide groups, in the tertiary structure, it is between the R groups |
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| hydrophobic interactions |
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| result when nonpolar groups are either attracted to one another or forced together by their mutual repulsion of an aqueous solution |
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| what is the weakest of the four types of bonds? |
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| the hydrophobic interactions |
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| quaternary structure |
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| arrangement of subunits |
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| what is a subunit |
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| a polypeptide chain |
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| if proteins are exposed to physical or chemical conditions such as extreme temperatures or pH values, what happens? |
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| denaturation |
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| what happens during denaturation? |
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| folded structure breaks down and the protein takes on a random disorganized conformation |
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| what else, besides heat and pH cause denaturation? |
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| heavy metal ions |
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