27: Biomolecules - Lipids
- Page ID
- 448857
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- When you have completed Chapter 27, you should be able to
- fulfill all of the detailed objectives listed under each individual section.
- distinguish among fats and oils, phospholipids, prostaglandins, terpenes and steroids, and be familiar with the sources and biological roles of these substances.
- define, and use in context, the key terms introduced in this chapter.
Lipids are organic compounds with limited water solubility and can be extracted using nonpolar solvents. They include fats, oils, waxes, vitamins, hormones, and nonprotein components of cell membranes. Unlike carbohydrates and proteins, lipids are characterized by their solubility rather than their structure. Key types of lipids discussed in this context include triacylglycerols, eicosanoids, terpenoids, and steroids.
- 27.0: Why This Chapter?
- This chapter introduces lipids, essential biomolecules that play critical roles in biological systems, including energy storage, membrane structure, and signaling. It highlights the diversity of lipid structures, their classifications, and their functional significance in living organisms. Understanding lipids is crucial for comprehending their involvement in health, disease, and biochemistry.
- 27.1: Waxes, Fats, and Oils
- This section discusses waxes, fats, and oils, which are types of lipids distinguished by their structures and properties. Waxes are long-chain fatty acids esterified to long-chain alcohols, providing waterproofing. Fats and oils are triglycerides, formed from glycerol and fatty acids. The key difference lies in saturation: fats (saturated) are solid at room temperature, while oils (unsaturated) are liquid. Their biological roles include energy storage and insulation.
- 27.2: Soap
- This section explores soap, a product derived from the saponification process, where triglycerides react with a strong base, producing glycerol and soap. Soaps consist of long-chain fatty acids with a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail, enabling them to emulsify fats and oils in water. This property makes soap effective for cleaning. Additionally, the section discusses different types of soaps and their roles in personal care and household cleaning.
- 27.3: Phospholipids
- Phospholipids are essential components of cellular membranes, composed of two fatty acids, a glycerol backbone, and a phosphate group. Their structure creates a hydrophilic (water-attracting) "head" and two hydrophobic (water-repelling) "tails," allowing them to form bilayers in aqueous environments. This unique arrangement is crucial for membrane fluidity and permeability, facilitating cellular processes like signaling and transport. Phospholipids are involved in the formation of liposomes.
- 27.4: Prostaglandins and Other Eicosanoids
- Prostaglandins were first discovered and isolated from human semen in the 1930s by Ulf von Euler of Sweden. Thinking they had come from the prostate gland, he named them prostaglandins. It has since been determined that they exist and are synthesized in virtually every cell of the body. Prostaglandins, are like hormones in that they act as chemical messengers, but do not move to other sites, but work right within the cells where they are synthesized.
- 27.5: Terpenoids
- Prostaglandins and other eicosanoids are signaling molecules derived from fatty acids, particularly arachidonic acid. They play crucial roles in various physiological processes, including inflammation, pain, fever, and regulation of blood flow. Prostaglandins are synthesized through cyclooxygenase enzymes, leading to diverse biological effects. Eicosanoids can also influence immune responses and are implicated in numerous diseases.
- 27.6: Steroids
- Steroids are a class of lipids characterized by a core structure of four fused carbon rings. They function as hormones and signaling molecules, influencing various biological processes, including metabolism, immune response, and reproductive functions. Examples include cholesterol, which is vital for cell membrane structure and as a precursor to other steroids, and sex hormones like estrogen and testosterone. Understanding steroids is essential for exploring their roles in health and disease.
- 27.7: Biosynthesis of Steroids
- Steroid biosynthesis involves complex biochemical pathways that convert cholesterol into various steroid hormones. Key enzymes, such as cytochrome P450s, play crucial roles in the oxidation and rearrangement of steroid precursors. The process is regulated by factors like hormonal signals and tissue specificity, leading to the synthesis of hormones like cortisol, testosterone, and estrogen. Understanding steroid biosynthesis is vital for insights into metabolic disorders.
- 27.8: Chemistry Matters—Saturated Fats, Cholesterol, and Heart Disease
- This section discusses the relationship between saturated fats, cholesterol, and heart disease. It highlights how high levels of saturated fats can increase low-density lipoprotein (LDL) cholesterol, contributing to atherosclerosis. The text emphasizes the importance of dietary choices, suggesting that replacing saturated fats with unsaturated fats may reduce heart disease risk. It also covers the complexities of cholesterol's role in the body.
- 27.10: Summary
- The summary of the chapter on lipids highlights the diverse roles of lipids in biological systems, including energy storage, membrane structure, and signaling. It covers different types of lipids, such as fatty acids, triglycerides, phospholipids, and steroids, emphasizing their unique structures and functions. The chapter also discusses the importance of dietary fats and the implications of lipid metabolism for health.