Term
| Proteins are made of _______ |
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Definition
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Term
| Amino acids vary in structure and function because _________ |
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Definition
| their side chains vary in composition |
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Term
| The structure of a protein can be analyzed at four levels that form a hierarchy— ________ |
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Definition
| the amino acid sequence, substructures called α-helices and β-pleated sheets, interactions between amino acids that dictate a protein’s overall shape, and combinations of individual proteins that make up larger, multiunit molecules. |
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Term
| During enzyme catalysis, the reactants bind to ________ |
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Definition
| an enzyme’s active site in a way that allows the reaction to proceed efficiently |
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Term
To test whether the first steps of chemical evolution could have occurred on ancient Earth, Stanley Miller combined methane (CH4), ammonia (NH3), and hydrogen (H2) in a closed system with water, and applied heat and electricity as an energy source
The products that resulted from Miller’s experiment included ________ |
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Definition
| hydrogen cyanide (HCN) and formaldehyde (H2CO), important precursors for more-complex organic molecules and amino acids. |
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Term
| All proteins are made from just ______ |
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Definition
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Term
| All amino acids have a central carbon atom that bonds to ________, ________, _______, and ______ |
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Definition
| NH2 (an amino functional group); COOH (a carboxyl functional group); H; a variable side chain |
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Term
| In water (pH7), the amino and carboxyl groups ionize to NH3+ and COO–, respectively, which helps ________ |
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Definition
| amino acids stay in solution and makes them more reactive |
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Term
| Amino acids with hydroxyl, amino, carboxyl, or sulfhydryl functional groups in their side chains are _____ than those with side chains composed of only carbon and hydrogen atoms. |
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Definition
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Term
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Definition
| molecules with the same molecular formula but different structures |
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Term
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Definition
| have the same atoms but differ in the arrangement of atoms, or groups, around a carbon atom that has four different groups attached |
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Term
| amino acids ______ to form proteins. ________ reactions require energy and are not spontaneous. |
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Definition
| polymerize; polymerization |
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Term
| Monomers polymerize through ________, also known as ______, which release a water molecule. |
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Definition
| condensation reactions; dehydration reactions |
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Term
| In ________, water reacts with a polymer to release a monomer. |
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Definition
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Term
| In the prebiotic soup,______ would predominate over ________ because it is energetically favorable. |
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Definition
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Term
| Condensation reactions bond the carboxyl group of one amino acid to the amino group of another to form a _______ |
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Definition
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Term
| A polypeptide is _______ & has ________ (the N-terminus has a free amino group and the C-terminus has a free carboxyl group), and its side chains extend out from the backbone |
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Definition
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Term
| A protein's primary structure is _________ |
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Definition
| its unique sequence of amino acids |
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Term
| Secondary structure of a protein results in part from _______ |
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Definition
| hydrogen bonding between the carboxyl oxygen of one amino acid residue and the amino hydrogen of another. |
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Term
| A protein's secondary structure increases its ________ — although each hydrogen bond is very weak relative to a covalent bond, the large number of hydrogen bonds makes these structures highly stable. |
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Definition
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Term
| The tertiary structure of a polypeptide results from ________ |
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Definition
| interactions between R-groups or between R-groups and the peptide backbone |
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Term
| R-group interactions include _________ |
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Definition
| hydrogen bonds, van der Waals interactions, covalent disulfide bonds, and ionic bonds |
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Term
| van der Waals interactions are ________. Although these interactions are weak, the large number of van der Waals interactions in a polypeptide significantly increases stability. |
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Definition
| electrical interactions between hydrophobic side chains |
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Term
| the bonding of two or more subunits produces _______ in a protein |
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Definition
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Term
| Protein folding is often spontaneous, because _______ |
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Definition
| the hydrogen bonds and van der Waals interactions make the folded molecule more stable energetically than the unfolded molecule. |
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Term
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Definition
| lowers the activation energy of a reaction by lowering the free energy of the transition state; do not change ΔG; not consumed in the reaction |
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Term
| Substrates bind to the ________, and interactions between the enzyme and the substrate stabilize the transition state and lower the activation energy required for the reaction to proceed. |
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Definition
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Term
| R-groups in the active site may form short-lived covalent bonds that assist with the transfer of atoms or groups of atoms from one reactant to another. The presence of acidic or basic R-groups allows the reactants to gain or lose a proton more readily |
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Definition
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Term
| Enzymes induce the formation of the transition state to increase reaction rates. ______ have a low affinity for the active site and are therefore released from the enzyme. |
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Definition
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Term
| Enzyme catalysis has three steps: During initiation, ______; during transition state facilitation, ________; and during termination, ________ |
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Definition
| reactants are precisely oriented as they bind to the active site; interactions between the substrate and active site R-groups lower the activation energy; reaction products are released from the enzyme |
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Term
| Some enzymes require _______ to function normally. These are either ______ or small organic molecules called ______. The cofactors usually are in _______ and are involved in transition state stabilization. |
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Definition
| cofactors; metal ions; coenzymes; the active site |
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Term
| Competitive inhibition occurs when _______ |
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Definition
| a molecule similar in size and shape to the substrate competes with the substrate for active site binding |
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Term
| Allosteric regulation occurs when a molecule causes a change in enzyme shape by binding to the enzyme at a location other than the active site. Allosteric regulation either ______ depending on the way in which ________ |
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Definition
| increases or decreases enzyme activity; enzyme shape changes |
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Term
| In enzymatic reactions, the rate of product formation increases linearly for a given increase in ______ at low substrate concentrations, but ______ at high substrate concentrations |
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Definition
| substrate concentration; levels out |
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Term
| * Enzymes with high substrate affinity rapidly achieve their maximum reaction rate as substrate concentration increases, whereas enzymes with low affinity for their substrate require ________ concentrations before they reach their maximum rate. |
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Definition
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Term
| Temperature affects the movement of substrates and enzyme; pH affects the enzyme's ________. |
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Definition
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Term
| Several observations argue that the first self-replicating molecule on Earth was a protein |
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Definition
| (1) Amino acids were abundant in the prebiotic soup, (2) proteins are the most efficient catalysts known, and (3) a self-replicating molecule had to act as a catalyst for the assembly and polymerization of its copy. |
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Term
| chemical evolution hypothesis |
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Definition
| Complex organic compounds formed from water and atmospheric gases present on early Earth |
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Term
| At which step of chemical evolution did life become possible? |
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Definition
| evolution of an information-containing, self-replicating molecule |
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Term
| What is one example of the many critical functions of proteins in organisms? |
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Definition
| They impart mobility to cells and entire organisms. |
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Term
| Monomers join to form polymers under what chemical conditions? |
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Definition
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Term
| What types of interactions are responsible for the secondary structure of a protein? |
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Definition
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Term
| protein primary structure |
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Definition
| The sequence of amino acids in a polypeptide |
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Term
| quaternary structure of a protein |
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Definition
| shape produced when two or more polypeptides associate to form a functional protein |
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Term
| secondary structure of a protein |
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Definition
| formation of a-helices and b-pleated sheets |
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Term
| tertiary structure of a protein |
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Definition
| overall three-dimensional shape of a polypeptide |
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Term
| how do prions cause disease? |
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Definition
| They cause changes in the shape of normal protein molecules that lead to disintegration of mammalian brains. |
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Term
| In what important way does a competitive inhibitor differ from an allosteric inhibitor> |
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Definition
| A competitive inhibitor binds to the active site, whereas an allosteric inhibitor binds to a site other than the active site. |
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Term
| How does ATP provide the chemical energy to drive many endergonic reactions? |
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Definition
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