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Unit 2: The Molecules of Life

Last updated

May 15, 2022
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- 1.8: pH
- 2.1: Organic Molecules

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2.1: Organic Molecules
This page outlines various functional groups in organic chemistry, including hydroxyl, carboxyl, carbonyl, and amino groups, along with examples like alcohols (methanol, ethanol), carboxylic acids, aldehydes (formaldehyde), ethers, esters, ketones, amines, and amides. Each group's connection to organic molecules and their biological significance is emphasized. The content is attributed to John W. Kimball, licensed under CC BY 3.0.
2.2: Hydrocarbons
This page discusses hydrocarbons, organic compounds made of carbon and hydrogen, categorized into aliphatic (linear chains) and aromatic (ring structures). Aliphatic hydrocarbons include saturated compounds like methane and unsaturated types like ethylene. Aromatic hydrocarbons are based on benzene rings and occur in biological molecules, including amino acids, cholesterol, and hormones. Beta-carotene is highlighted as a hydrocarbon containing both aliphatic and aromatic components.
2.3: Fats
This page explains the composition of fat molecules, highlighting that they consist of glycerol and three fatty acids, forming triglycerides. It distinguishes between saturated and unsaturated fats, noting that animal fats are usually more saturated. It describes how hydrogenation alters liquid oils to solid fats, producing trans fatty acids.
2.4: Phospholipids
This page describes phospholipids as fat derivatives with a phosphate group and nitrogen-containing molecule replacing one fatty acid, creating an amphiphilic structure. An example given is phosphatidyl ethanolamine (cephalin). These molecules are crucial for cell membranes, forming a bilayer with hydrophilic heads facing water and hydrophobic tails inward.
2.5: Cholesterol
This page discusses the importance of cholesterol as a vital steroid for life, its role in cell membranes and hormone production, and the risks of high LDL levels. Desirable cholesterol levels for adults are below 200 mg/dl. Strategies for managing cholesterol include diet, exercise, and medications such as statins, particularly for those at risk of heart disease. It also highlights the complex relationship between dietary fats and cholesterol, noting that unsaturated fats can be beneficial.
2.6: Carbohydrates
This page explains carbohydrates as polymers of glucose, including starch and cellulose. It details monosaccharides like glucose, galactose, and fructose, which combine into disaccharides like sucrose and lactose through glycosidic bonds. Carbohydrates are key energy sources in diets. Starch is formed in amylose (linear) and amylopectin (branched) forms, while cellulose serves a structural role in cell walls with its rigid fibrils.
2.7: Amino Acids
This page explains that amino acids, the building blocks of proteins, come in 20 types. Each has a unique "R" group affecting its properties, with nine essential amino acids required from the diet, including histidine and leucine. It highlights the importance for vegetarians to ensure sufficient intake of lysine and tryptophan, which are commonly deficient in plant proteins.
2.8: Enantiomers
This page explains the tetrahedral arrangement of carbon atoms forming four covalent bonds, exemplified by methane. It discusses how the presence of different groups around carbon can lead to enantiomers, using alanine as an example of L- and D- formations, emphasizing the predominance of L amino acids in protein synthesis. Chirality's importance is highlighted, noting that a protein's functionality depends on its shape.
2.9: Polypeptides
This page explains that the amino acid sequence in polypeptides is dictated by codons in mRNA, which originate from the DNA sequence, and that proteins are made up of one or more polypeptide chains.
2.10: Proteins
This page discusses the importance of proteins, essential macromolecules made of amino acids, for various cellular functions. Their structure, including primary, secondary, tertiary, and quaternary forms, is crucial for functionality, with molecular chaperones aiding proper folding. Disruption of structure leads to denaturation, impacting activities like enzymatic reactions. Mutations can lead to diseases such as Creutzfeldt-Jakob.
2.11: Rules of Protein Structure
This page explains that a protein's function is dependent on its three-dimensional shape, determined by its amino acid sequence encoded in DNA. Factors such as pH, salt concentration, and temperature can denature proteins. Some proteins can regain their shape and function when conditions return to normal, assisted by molecular chaperones. Ultimately, the amino acid sequence, governed by genes, dictates a protein's structure and function.
2.12: Glycoproteins
This page discusses glycoproteins, which are proteins with carbohydrate attachments via glycosylation. It highlights Glycophorin A, a significant glycoprotein in red blood cells that has O-linked and N-linked chains, influencing hydrophilicity and protein folding. Two polymorphic variants of glycophorin A are associated with blood groups M and N. Furthermore, this glycoprotein acts as an important entry point for the malaria parasite, Plasmodium falciparum, into red blood cells.
2.13: Nucleotides
This page explains the structure of nucleic acids, highlighting that they are linear polymers made of nucleotides, which include a five-carbon sugar (deoxyribose for DNA and ribose for RNA) and nucleobases. DNA has adenine, guanine, cytosine, and thymine, while RNA has adenine, guanine, cytosine, and uracil.
2.14: Proteomics
This page explains the distinctions between a genome, transcriptome, metabolome, and proteome. The genome consists of all genes in an organism; the transcriptome encompasses all RNA, mainly mRNA for protein synthesis. The metabolome includes all metabolic components, while the proteome represents the diverse proteins produced from the genome, influenced by factors like alternative splicing.

Contributors and Attributions

John W. Kimball. This content is distributed under a Creative Commons Attribution 3.0 Unported (CC BY 3.0) license and made possible by funding from The Saylor Foundation.
Thumbnail: Cellulose molecular structure (CC BY-SA 3.0 Unported; Pintor4257 via Wikipedia)

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