abscisic acid

Examples of abscisic acid in the following topics:

• Abscisic Acid, Ethylene, and Nontraditional Hormones

  • All physiological aspects of plants are affected by plant hormones, including abscisic acid, ethylene, and nontraditional hormones.
  • In addition to the growth hormones auxins, cytokinins, gibberellins, there are two more major types of plant hormones, abscisic acid and ethylene, as well as several other less-studied compounds that control plant physiology.
  • The plant hormone abscisic acid (ABA) was first discovered as the agent that causes the abscission or dropping of cotton bolls.
  • Ethylene stimulates the conversion of starch and acids to sugars.
  • For example, chewing of tomato plants by caterpillars leads to an increase in jasmonic acid levels, which in turn triggers the release of volatile compounds that attract predators of the pest.

• The Evolution of Seed Plants and Adaptations for Land

  • Furthermore, seeds remain in a state of dormancy induced by desiccation and the hormone abscisic acid until conditions for growth become favorable.

• Auxins, Cytokinins, and Gibberellins

  • Five major plant hormones are traditionally described: auxins, cytokinins, gibberellins, ethylene, and abscisic acid.
  • While many synthetic auxins are used as herbicides, indole acetic acid (IAA) is the only naturally-occurring auxin that shows physiological activity.
  • Abscisic acid is a strong antagonist of GA action.
  • In grapes, application of gibberellic acid increases the size of fruit and loosens clustering.

• Connecting Proteins to Glucose Metabolism

  • However, if there are excess amino acids, or if the body is in a state of starvation, some amino acids will be shunted into the pathways of glucose catabolism.
  • The remaining atoms of the amino acid result in a keto acid: a carbon chain with one ketone and one carboxylic acid group.
  • The keto acid can then enter the citric acid cycle.
  • When deaminated, amino acids can enter the pathways of glucose metabolism as pyruvate, acetyl CoA, or several components of the citric acid cycle.
  • The carbon skeletons of certain amino acids (indicated in boxes) are derived from proteins and can feed into pyruvate, acetyl CoA, and the citric acid cycle.

• Amino Acids

  • An amino acid contains an amino group, a carboxyl group, and an R group, and it combines with other amino acids to form polypeptide chains.
  • Amino acids are the monomers that make up proteins.
  • The name "amino acid" is derived from the amino group and carboxyl-acid-group in their basic structure.
  • Each amino acid is attached to another amino acid by a covalent bond, known as a peptide bond.
  • The carboxyl group of one amino acid is linked to the amino group of the incoming amino acid.

• Lipid Molecules

  • Stearic acid and palmitic acid, which are commonly found in meat, are examples of saturated fats.
  • Oleic acid is an example of an unsaturated fatty acid.
  • Essential fatty acids are fatty acids required for biological processes, but not synthesized by the human body.
  • Omega-3 fatty acid, or alpha-linoleic acid (ALA) , falls into this category and is one of only two fatty acids known to be essential for humans (the other being omega-6 fatty acid, or linoleic acid).
  • Alpha-linolenic acid is an example of an omega-3 fatty acid.

• Acetyl CoA to CO2

  • The acetyl carbons of acetyl CoA are released as carbon dioxide in the citric acid cycle.
  • Acetyl CoA links glycolysis and pyruvate oxidation with the citric acid cycle.
  • In addition to the citric acid cycle, named for the first intermediate formed, citric acid, or citrate, when acetate joins to the oxaloacetate, the cycle is also known by two other names.
  • The TCA cycle is named for tricarboxylic acids (TCA) because citric acid (or citrate) and isocitrate, the first two intermediates that are formed, are tricarboxylic acids.
  • Describe the fate of the acetyl CoA carbons in the citric acid cycle

• Lipid-Derived, Amino Acid-Derived, and Peptide Hormones

  • All hormones in the human body can be divided into lipid-derived, amino acid-derived, and peptide hormones.
  • The amino acid-derived hormones are relatively small molecules derived from the amino acids tyrosine and tryptophan .
  • If a hormone is amino acid-derived, its chemical name will end in "-ine".
  • The structure of peptide hormones is that of a polypeptide chain (chain of amino acids).
  • Amino acid-derived and polypeptide hormones are water-soluble and insoluble in lipids.

• Nitrogenous Waste in Birds and Reptiles: Uric Acid

  • In contrast, mammals (including humans) produce urea from ammonia; however, they also form some uric acid during the breakdown of nucleic acids.
  • Uric acid is a compound similar to purines found in nucleic acids.
  • Uric acid is also less toxic than ammonia or urea.
  • Uric acid is released in hypoxic conditions.
  • These include (a) ammonia, (b) urea, and (c) uric acid.

• Peptide Bonding between Amino Acids

  • The peptide bond is an amide bond which links amino acids together to form proteins.
  • A peptides is a molecule composed of two or more amino acids.
  • The bond that holds together the two amino acids is a peptide bond, or a covalent chemical bond between two compounds (in this case, two amino acids).
  • The peptide bond (circled) links two amino acids together.
  • Identify the amino acids that were combined to create a peptide.