18: Amino Acids and Proteins
- Page ID
- 86306
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 18.1: An Introduction to Biochemistry
- This page provides an introduction to biomolecules, vital for the structure and function of living organisms. It classifies biomolecules into four types: carbohydrates, proteins, lipids, and nucleic acids, emphasizing their complexity and the importance of smaller molecules and ions in cellular functions. Readers are encouraged to leverage their knowledge of chemistry to understand biomolecules and their properties in living cells.
- 18.2: Proteins and Their Functions- An Overview
- This page explores proteins as vital organic molecules in cells, detailing their structural and functional classifications into fibrous, globular, and membrane proteins. Fibrous proteins offer structural support, globular proteins are compact and often water-soluble for functions like enzyme activity and transport, and membrane proteins engage with lipid bilayers for cellular processes. The content highlights the relationship between protein structure and their specific roles.
- 18.3: Amino Acids
- This page covers the structure and classification of amino acids, the building blocks of proteins. It details the 20 common amino acids, each with an amino group, carboxyl group, and unique side chain classified based on polarity and charge. Glycine is highlighted for lacking a chiral center. The page also emphasizes essential amino acids that must be acquired through diet and mentions amino acid derivatives like hydroxyproline found in proteins.
- 18.4: Acid-Base Properties of Amino Acids
- This page discusses the dual functionality of amino acids as acids and bases, influenced by pH levels. It defines the isoelectric point (pI) where amino acids exist as zwitterions. Fluctuations in pH affect the charge of amino acids by altering hydrogen ion presence. The properties of their functional groups, typical of carboxylic acids and amines, are essential in peptide synthesis and are applicable in chemical tests, such as the ninhydrin test for identifying amino acids.
- 18.5: Peptides
- This page explains how peptides are formed from amino acids via peptide bonds, emphasizing the importance of the amino acid sequence for protein functionality. A change in the order can disrupt protein activity, as demonstrated by the example of bradykinin, where reversing the sequence negates its effects. Overall, the specific arrangement of amino acids is essential for creating functional proteins.
- 18.6: Protein Structure- An Overview and Primary Protein Structure
- This page details the primary structure of proteins, emphasizing how unique amino acid sequences shape their three-dimensional form and function. It explains the importance of these structures, defining primary structure as the arrangement of amino acids in polypeptide chains connected by peptide bonds. Human insulin is cited as an example, showcasing how specific amino acid sequences influence the protein's role in biological processes like glucose metabolism.
- 18.7: Secondary Protein Structure
- This page explores the configurations of protein molecules, emphasizing secondary structures like the α-helix and β-pleated sheet. It explains that the α-helix is stabilized by hydrogen bonds between amino acids and features a specific turn pattern, while the β-pleated sheet involves aligned polypeptide chains connected by interchain hydrogen bonds. These structures are essential for protein function, illustrated by examples such as silk and enzymes.
- 18.8: Tertiary Protein Structure
- This page discusses the tertiary structure of proteins, highlighting its importance in biochemical function due to its unique three-dimensional shape. It outlines key interactions that stabilize this structure, including ionic bonding between charged amino acids, hydrogen bonds between polar side chains, disulfide linkages from cysteine oxidation, and dispersion forces from transient polarizations of nonpolar atoms.
- 18.9: Quaternary Protein Structure
- This page explains the quaternary structure of proteins, which involves multiple polypeptide chains (subunits) such as hemoglobin, made of four subunits. It notes that the stabilizing interactions in quaternary structure are akin to those in tertiary structure. Additionally, the page outlines the hierarchy of protein structure from primary (amino acid sequence) to secondary (α-helix) and tertiary (folded polypeptide chains).
- 18.10: Chemical Properties of Proteins
- This page explains protein hydrolysis and denaturation, focusing on how alterations in proteins' three-dimensional structures affect their function. Denaturation can result from heat, chemicals, or pH changes, with examples like cooked egg whites. It notes that while primary structures are stable, higher structures are more vulnerable. Some proteins may refold and regain functionality, suggesting that their primary structure is crucial in determining their three-dimensional shape.