18: Amino Acids, Proteins, and Enzymes
- Page ID
- 15937
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\(\newcommand{\ket}[1]{\left| #1 \right>} \)
\( \newcommand{\bra}[1]{\left< #1 \right|} \)
\( \newcommand{\braket}[2]{\left< #1 \vphantom{#2} \right| \left. #2 \vphantom{#1} \right>} \)
\( \newcommand{\qmvec}[1]{\mathbf{\vec{#1}}} \)
\( \newcommand{\op}[1]{\hat{\mathbf{#1}}}\)
\( \newcommand{\expect}[1]{\langle #1 \rangle}\)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Proteins may be defined as compounds of high molar mass consisting largely or entirely of chains of amino acids. Their masses range from several thousand to several million daltons (Da). In addition to carbon, hydrogen, and oxygen atoms, all proteins contain nitrogen and sulfur atoms, and many also contain phosphorus atoms and traces of other elements. Proteins serve a variety of roles in living organisms and are often classified by these biological roles. Muscle tissue is largely protein, as are skin and hair. Proteins are present in the blood, in the brain, and even in tooth enamel. Each type of cell in our bodies makes its own specialized proteins, as well as proteins common to all or most cells. We begin our study of proteins by looking at the properties and reactions of amino acids, which is followed by a discussion of how amino acids link covalently to form peptides and proteins. We end the chapter with a discussion of enzymes—the proteins that act as catalysts in the body.
- 18.0: Prelude to Amino Acids, Proteins, and Enzymes
- This page discusses the Nobel Prizes awarded for insulin research: Banting and Macleod received the 1923 Medicine Prize for insulin's discovery, while Sanger won the 1958 Chemistry Prize for his work on protein structure related to insulin. Insulin plays a vital role in glucose regulation and its isolation in 1921 revolutionized diabetes treatment, underscoring its importance to health.
- 18.1: Properties of Amino Acids
- This page discusses amino acids, the 20 building blocks of proteins with distinct classifications based on side chains: nonpolar, polar (uncharged), negatively charged, and positively charged. Humans can synthesize approximately half of these amino acids, while others are essential and must be acquired through diet. Additionally, most amino acids are chiral and predominantly found in the L-enantiomeric form in proteins, with glycine as the exception, being non-chiral.
- 18.2: Reactions of Amino Acids
- This page discusses the dual functionality of amino acids as acids and bases due to their amino and carboxyl groups. At the isoelectric point (pI), amino acids predominantly exist as zwitterions. pI values differ among amino acids, with neutral ones ranging from 5.0 to 6.5, and basic or acidic ones having higher or lower pIs, respectively. The reactive functional groups of amino acids are essential for peptide and protein formation, which can be analyzed using techniques like the ninhydrin test.
- 18.3: Peptides
- This page explains that peptides are formed through peptide bonds between amino acids, releasing water in the process. The sequence of amino acids is critical for protein function, with even slight variations potentially causing diseases like sickle cell anemia. While "peptide" is a broader term, proteins or polypeptides typically include 50 or more amino acids, emphasizing the importance of the correct amino acid order for physiological activity.
- 18.4: Proteins
- This page explains that proteins are complex molecules made of amino acids, categorized as fibrous or globular, and structured in four levels: primary, secondary, tertiary, and quaternary. Stability arises from various interactions, including ionic and hydrogen bonds. Denaturation can disrupt protein structure and function due to heat, pH changes, or heavy metals, though some proteins can refold and regain functionality under suitable conditions.
- 18.5: Enzymes
- This page discusses enzymes as biological catalysts that accelerate chemical reactions at body temperature and physiological pH without undergoing changes. Highly specific to certain substrates, they play a key role in drug development like AIDS treatments targeting HIV enzymes. Enzymes are categorized into six groups based on their reactions, following a systematic naming system by the International Union of Biochemistry that includes a four-digit classification and an '-ase' suffix.
- 18.6: Enzyme Action
- This page discusses how enzymes bind substrates at their active sites to convert them into products via reversible interactions. It explains the induced-fit model, which describes the conformational change of enzymes during substrate binding for improved catalysis. Enzyme specificity varies; some target single substrates while others are selective for related molecules, influenced by the structure of their active sites.
- 18.7: Enzyme Activity
- This page discusses how enzymes enhance reaction rates in living organisms, affected by pH, temperature, and concentrations of substrates and enzymes. It notes that reaction rates rise with increasing substrate concentration until saturation, and with enzyme concentration when substrates are plentiful.
- 18.8: Enzyme Inhibition
- This page explains enzyme inhibition mechanisms, contrasting irreversible inhibitors, which form strong covalent bonds, with reversible inhibitors that utilize temporary interactions. It discusses competitive inhibitors like malonate and highlights penicillin's role in inhibiting bacterial growth by targeting enzymes essential for cell wall synthesis, alongside antibiotic resistance issues.
- 18.9: Enzyme Cofactors and Vitamins
- This page discusses vitamins as essential organic compounds for normal metabolism, categorized into fat-soluble (A, D, E, K) and water-soluble (B complex, C) types. Water-soluble vitamins often act as coenzymes, and their deficiency can lead to diseases. The roles of key vitamins include supporting vision, bone health, and providing antioxidant protection against free radicals, with vitamins C and E specifically noted for mitigating free radical damage to cells and membranes.
- 18.E: Amino Acids, Proteins, and Enzymes (Exercises)
- This page explores amino acids, peptides, proteins, and enzymes, detailing their structures, properties, and interactions. It covers enzyme activity, focusing on how substrate concentration, pH, and temperature affect reactions, alongside the roles of coenzymes and inhibitors. Additionally, it highlights the characteristics of certain peptides and carbohydrates related to solubility and reaction rates, emphasizing enzyme saturation effects.
- 18.S: Amino Acids, Proteins, and Enzymes (Summary)
- This page discusses proteins, large polymers formed from 20 amino acids, with half being essential. Amino acids function as zwitterions, acting as acids or bases. Proteins are categorized by structure and function, featuring four organizational levels: primary, secondary, tertiary, and quaternary. It highlights enzymes as biological catalysts that interact with substrates at active sites and can be inhibited.