Kotz and Triechel, Chemistry and Chemical Reactivity Chapter 24: Sections 1-5.
- 24.1 Proteins are condensation polymers, formed through peptide bond formatin from compounds that contain an amine group (NH2) and a Carboxylic acid group (COOH) with the general formula H3N-R-COOH. While there are hundreds of possible amino acids, twenty in particular are important to life on earth, forming the components of proteins according to the dictates of RNA codons transcribed from DNA templates. Peptide bonds form when the COOH group on one amino acid gives up an OH group, and the NH2 group on another amino acid gives up an H. The remaining C from the COOH group and the N from the NH2 group form a peptide bond. Because the bond formation results in the loss of a water molecule, this process is often called dehydration synthesis. The polypeptide chain formed by dehydration synthesis can be twisted and folded so that H-bonds formed between different sections, providing stability and rigidity that give the final form of the protein a specific shape and allow it to function as a catalytic enzyme.
- 24.2 Carbohydrates also form from monomer structures, usually isomers of glucose, through dehydration synthesis. Polysaccharide chains can branch or form H-bonds that create sheets of starches and cellulose, with different structural rigidity and chemical properties, to function in a variety of biological situations.
- 24.3 Nucleic acids inlude the purines cytosine and thymine and the pimiridines guanine and adenine. The difference in size of purines and pirimidines, and the difference in H-bonds formed by cytosine and guanine (3) compared to thymine and adenine (2) dictate that the formation of bonds between nucleic acids in DNA is limited to A-T or G-C combinations. RNA transcriptase "reads" the DNA sequence and maps the sequence to three-nucleic-acid codons. Outside the nucleus, ribosomes in the endoplasmic rheticulum map the codons to amino acids to create polypeptide chains that become proteins.
- 24.4 Lipids are combinations of hydrocarbon chains with glycerol "heads" to form molecules with distinct polar and non-polar regions. This combination allows molecules to arrange themselves into membranes that can contain special content for particular chemical reactions. Individual glycerol-hydrocarbons in the form of fatty acids and steroids act as hormones that can trigger or turn off metabolic processes.
- 24.5 Metabolic processes depend on energy and lipids provide a semi-permeable membrane that facilitate energy harvesting processes like electron transport and chemiosmosis, allowing cells to store and recover energy from ATP (adenosine triphosphate) through photosynthesis and cellular respiration:
C6H12O6 + O2 ⇔ CO2 + H2O
Running forward, the reaction is cellular respiration, harvesting energy from glucose. Running in reverse, the reaction is photosynthesis, storing light energy in glucose bonds.
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Videos for Chapter 24: Principles of Chemical Reactivity: Biochemistry
Review the Videos at Thinkwell Video Lessons.
- Under "BIOCHEMISTRY"
- Biological Molecules
- Nucleic Acids
Homework problems: See your Moodle assignment!
AP LAB #18 GUIDED INQUIRY — — GUIDED INQUIRY —
Titration quantitative analysis methods — Phase III
Complete any final experiments and data analysis, then post your formal report.
- APGIE Investigation 4: How much acid is in Fruit Juices and Soft Drinks
- APGIE Investigation 3: What Makes Hard Water Hard?
- IGHCE Lab 20.1 Quantitative Analysis of Vitamin C
- AP2009 8 Determination of Concentration by oxidation-reduction reactions
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