24: Lipid Metabolism
- Page ID
- 86362
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- 24.1: Digestion of Triacylglycerols
- This page explains lipid digestion and transport. It begins in the small intestine, where bile emulsifies fats for pancreatic lipases to convert triglycerides into smaller components. Long-chain fatty acids and monoacylglycerides form micelles for absorption by intestinal cells, where they are reassembled into triglycerides. These are encased in chylomicrons and enter lacteals, leading to their transport into the bloodstream through the lymphatic system.
- 24.2: Lipoproteins for Lipid Transport
- This page reviews the five lipoprotein classes critical for lipid transport in the bloodstream: chylomicrons, VLDLs, IDLs, LDLs, and HDLs. It explains their compositions, functions, and the distinction between "good" HDL and "bad" LDL cholesterol. The page underscores the importance of managing cholesterol levels and recommends omega-3 fatty acids for better LDL and HDL balance.
- 24.3: Triacylglycerol Metabolism - An Overview
- This page discusses triacylglycerols, which are vital for energy storage, insulation, and protection in the body. They can be ingested or synthesized from excess nutrients and are transported in chylomicrons. Lipoprotein lipase breaks them down into fatty acids and glycerol for energy or storage. When energy is needed, stored triacylglycerols are hydrolyzed in adipose tissue, releasing fatty acids and glycerol, with glycerol also potentially participating in glycolysis or gluconeogenesis.
- 24.5: Oxidation of Fatty Acids
- This page explains fatty acid oxidation, a process that begins in the cytosol and produces ATP in the mitochondria. Fatty acids are activated to fatty acyl-CoA using ATP and transported into the mitochondria for beta-oxidation. This four-step cycle generates acetyl-CoA and reduces coenzymes NADH and FADH2, yielding a total of 129 ATP from palmitic acid, with an efficiency of about 41%. Additionally, the process produces water, which can be advantageous for some animals.
- 24.6: Ketone Bodies and Ketoacidosis
- This page explains the structure and function of ketone bodies—acetoacetate, β-hydroxybutyrate, and acetone—produced in the liver from acetyl-CoA during fatty acid oxidation. During prolonged starvation or diabetes, increased fatty acid oxidation leads to elevated ketone levels and ketosis. This condition can cause acidosis, reducing blood pH and impairing hemoglobin function, resulting in health complications like lethargy and dehydration, which may necessitate urgent medical care.
- 24.7: Biosynthesis of Fatty Acids
- This page discusses the synthesis and breakdown of fatty acids, focusing on lipogenesis in the cytoplasm and endoplasmic reticulum. It explains the construction of fatty acids from acetyl-CoA, highlighting acetyl-CoA carboxylase as a critical regulatory enzyme. Additionally, the page covers elongation and desaturation processes in the endoplasmic reticulum, noting that certain essential fatty acids must be acquired from the diet due to human enzymatic limitations.