25: Protein and Amino Acid Metabolism
- Page ID
- 86383
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 25.1: Digestion of Proteins
- This page explains protein digestion, starting in the stomach with gastric juice that contains HCl and pepsin, hydrolyzing about 10% of peptide bonds. HCl denatures proteins, and pepsin activates specific peptide linkages. The process continues in the small intestine with pancreatic enzymes activated by enteropeptidase, further breaking down peptides, while aminopeptidases finalize the digestion, releasing free amino acids for absorption into the bloodstream for protein synthesis.
- 25.2: Amino Acid Metabolism - An Overview
- This page explains the significance of amino acids in the body, detailing the amino acid pool from dietary proteins, liver production, and recycling. It highlights their primary role in synthesizing proteins and nitrogen compounds, with energy production as a secondary function. It covers protein turnover variation and classifies amino acids into essential and nonessential types, affecting protein completeness.
- 25.3: Amino Acid Catabolism - The Amino Group
- This page covers amino acid metabolism, emphasizing nitrogen conservation and the liver's role in amino acid breakdown through transamination and oxidative deamination of glutamate. It describes how transamination aids glucose or fat synthesis, particularly during fasting, and details the production of ammonium ions for urea formation. Additionally, it stresses the reverse synthesis of glutamate, incorporating inorganic nitrogen necessary for the creation of various amino acids.
- 25.4: The Urea Cycle
- This page explains the urea cycle, a vital biochemical process in mammals that transforms toxic ammonia from amino acid breakdown into urea for excretion, mainly in the liver. It outlines the five enzyme-catalyzed steps of the cycle, which take place in both mitochondria and the cytosol. The page highlights that high blood urea nitrogen (BUN) levels may signal kidney problems, and discusses the connection between uric acid, gout, and dietary effects on nitrogenous waste management.
- 25.5: Amino Acid Catabolism - The Carbon Atoms
- This page explains how amino acids are metabolized into intermediates of the citric acid cycle following amino group removal. It distinguishes between glucogenic amino acids, which can be converted to glucose, and ketogenic amino acids, which are transformed into acetoacetyl-CoA or acetyl-CoA for ketone synthesis. Leucine and lysine are identified as exclusively ketogenic. A summary figure illustrates the various metabolic fates of the carbon skeletons of the 20 amino acids.
- 25.6: Biosynthesis of Nonessential Amino Acids
- This page discusses the synthesis of nonessential amino acids by humans, highlighting glutamate, glutamine, and proline as examples that share a common anabolic pathway. It emphasizes glutamine's role in ammonia detoxification and notes that other nonessential amino acids like alanine and aspartate arise from different metabolic pathways. Additionally, the page explains that essential amino acids, vital for metabolism, require complex synthesis processes typically carried out by microorganisms.
Thumbnail: Tryptophan is an α-amino acid that is used in the biosynthesis of proteins. It is an essential amino acid, which means that the human body cannot synthesize it for itself, and need to be provided by the diet.