23: Biochemistry
- Page ID
- 219335
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- 23.1: Diabetes and the Synthesis of Human Insulin
- The discovery of the link between insulin and diabetes led to a period of intense research aimed at understanding exactly how insulin works in the body to regulate glucose levels. Hormones in general act by binding to some protein, known as the hormone’s receptor, thus initiating a series of events that lead to a desired outcome. In the early 1970s, the insulin receptor was purified, and researchers began to study what happens after insulin binds to its receptor and how those events are linked t
- 23.2: Lipids
- Compounds isolated from body tissues are classified as lipids if they are more soluble in organic solvents, such as dichloromethane, than in water. Fatty acids are carboxylic acids that are the structural components of many lipids. They may be saturated or unsaturated. Lipids are important components of biological membranes. These lipids have dual characteristics: part of the molecule is hydrophilic, and part of the molecule is hydrophobic.
- 23.3: Carbohydrates
- All carbohydrates consist of carbon, hydrogen, and oxygen atoms and are polyhydroxy aldehydes or ketones or are compounds that can be broken down to form such compounds. Examples of carbohydrates include starch, fiber, the sweet-tasting compounds called sugars, and structural materials such as cellulose. The term carbohydrate had its origin in a misinterpretation of the molecular formulas of many of these substances.
- 23.4: Proteins and Amino Acids
- The proteins in all living species are constructed from the same set of 20 amino acids, so called because each contains an amino group attached to a carboxylic acid. The amino acids in proteins are α-amino acids, which means the amino group is attached to the α-carbon of the carboxylic acid. Humans can synthesize only about half of the needed amino acids; the remainder must be obtained from the diet and are known as essential amino acids.
- 23.5: Protein Structure
- Proteins can be divided into two categories: fibrous, which tend to be insoluble in water, and globular, which are more soluble in water. A protein may have up to four levels of structure. The primary structure consists of the specific amino acid sequence. The peptide chain can form an α-helix or β-pleated sheet, which is known as secondary structure and are incorporated into the tertiary structure of the folded polypeptide. The quaternary structure describes the arrangements of subunits.
- 23.6: Nucleic Acids- Blueprints for Proteins
- Nucleotides are composed of phosphoric acid, a pentose sugar (ribose or deoxyribose), and a nitrogen-containing base (adenine, cytosine, guanine, thymine, or uracil). Ribonucleotides contain ribose, while deoxyribonucleotides contain deoxyribose.
- 23.7: DNA Replication, the Double Helix, and Protein Synthesis
- Nucleotides are joined together to form nucleic acids through the phosphate groups. In DNA replication, each strand of the original DNA serves as a template for the synthesis of a complementary strand. In transcription, a segment of DNA serves as a template for the synthesis of an RNA sequence. In translation, the information in mRNA directs the order of amino acids in protein synthesis.