Fatty Acids, Fermentation, Cell Cycle, and Genetics

Posted on Mar 22, 2025 in Biology

September 3rd Notes: Biochemistry Topics

B1OA: Fatty Acids

  1. Fatty acids are monoenoic organic acids that are present in fats. They are rarely found free and are usually esterified to glycerol and, occasionally, other alcohols. They typically have straight chains with an even number of carbon atoms. Fatty acids can be saturated, unsaturated, or polyunsaturated.
  2. Functions of Fatty Acids:
    • Energy Reserve: They are an important energy source for biological use.
    • Structural Function: The bipolar nature of some (amphipathic) fatty acids allows them to organize into lipid bilayers.
    • Protective Function: Fats act as insulators, accumulating under the skin of birds and mammals.
    • Transport Function: Plasma lipoproteins are globular particles that facilitate lipid transport.
    • Biocatalytic Function: Steroid hormones and fat-soluble vitamins facilitate chemical reactions in living organisms.
  3. Steroid hormones are an example of a Biocatalytic Function.

B2OB: Fermentation

  1. Fermentation is a type of partial catabolism characterized as an incomplete oxidation process, typical of anaerobic organisms. It occurs without the intervention of oxygen. During fermentation, energy is derived, as in aerobic respiration, from the oxidation-reduction reactions that occur during glucose catabolism (glycolysis). However, the reduced coenzymes in fermentation do not yield their electrons to a chain where the final acceptor is oxygen. Instead, they donate them directly to an organic compound, which is reduced and becomes a characteristic product of each type of fermentation (e.g., lactic, alcoholic).
  2. The metabolic process in bread making is alcoholic fermentation. It is mediated by yeast and some bacteria possessing the enzyme alcohol dehydrogenase. Glucose molecules (present in the dough) undergo glycolysis, resulting in pyruvic acid. This pyruvic acid is decarboxylated under anaerobic conditions to form acetaldehyde, which is then reduced to ethyl alcohol by the action of NADH. The final electron acceptor from the NADH obtained in glycolysis is acetaldehyde.
    • Pyruvic acid → Acetaldehyde + CO2
    • Acetaldehyde + NADH → Ethanol + NAD+
  3. The metabolic process in yogurt development is lactic fermentation. It is carried out by lactic acid bacteria due to the presence of the enzyme lactate dehydrogenase. In this type of fermentation, pyruvic acid from glycolysis accepts electrons and is converted into lactic acid.
    • Pyruvic acid + NADH → Lactic acid + NAD+
  4. For both yeasts and bacteria performing these metabolic processes, ATP is the major product obtained in glycolysis. Alcohol, lactic acid, and CO2 are waste products.
  5. In both cases, fermentation takes place in the cytoplasm. This is because it’s the only location in bacteria (which lack organelles), and in eukaryotes (which, despite having mitochondria, carry out fermentation in the cytoplasm).

B3OB: Cell Cycle

  1. The cell cycle is the process through which a cell passes each time it divides. It consists of a series of steps during which chromosomes and other cellular material duplicate to make two copies. The cell then divides into two daughter cells, each receiving a duplicate copy of the material. The cell cycle is complete when each daughter cell is surrounded by its own outer membrane. It is also called the mitotic cycle. The phases include Interphase (G1 phase, S period, G2 phase) and Mitosis.
  2. Mitosis is involved in the growth of multicellular organisms and the asexual reproduction of organisms. In mitosis, stem cells may be haploid or diploid. Meiosis occurs in all life cycles involving sexual reproduction. In meiosis, stem cells are diploid.

B4QA: Genetics

  1. A gene is a DNA sequence that constitutes the functional unit for the transmission of hereditary characteristics. A codon is a triplet in messenger RNA (mRNA) that encodes the specific amino acid to be incorporated during protein biosynthesis. An anticodon is a sequence of three nucleotides in a transfer RNA (tRNA) that recognizes the corresponding codon in mRNA.