crassulacean acid metabolism

(noun)

A carbon fixation pathway that evolved in some plants as an adaptation to arid conditions, in which the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO2).

Related Terms

  • C4 carbon fixation
  • Crassulacean acid metabolism (CAM).
  • C4 Carbon Fixation

Examples of crassulacean acid metabolism in the following topics:

  • CAM and C4 Photosynthesis

    • Xerophytes, such as cacti and most succulents, also use phosphoenolpyruvate (PEP) carboxylase to capture carbon dioxide in a process called crassulacean acid metabolism (CAM).
    • In contrast to C4 metabolism, which physically separates the CO2 fixation to PEP from the Calvin cycle, CAM temporally separates these two processes.
    • CAM plants store the CO2 mostly in the form of malic acid via carboxylation of phosphoenolpyruvate to oxaloacetate, which is then reduced to malate.
    • Plants that do not use PEP-carboxylase in carbon fixation are called C3 plants because the primary carboxylation reaction, catalyzed by RuBisCO, produces the three-carbon 3-phosphoglyceric acids directly in the Calvin-Benson cycle.
    • Cross section of a CAM (crassulacean acid metabolism) plant, specifically of an agave leaf.
  • Connecting Proteins to Glucose Metabolism

    • Metabolic pathways should be thought of as porous; that is, substances enter from other pathways and intermediates leave for other pathways.
    • 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.
  • Pyruvic Acid and Metabolism

    • The Brønsted–Lowry conjugate base, CH3COCOO−, is known as pyruvate, and is a key intersection in several metabolic pathways.
    • It is the output of the anaerobic metabolism of glucose known as glycolysis.
    • These reactions are named after Hans Adolf Krebs, the biochemist awarded the 1953 Nobel Prize for physiology, jointly with Fritz Lipmann, for research into metabolic processes.
    • Pyruvate is a key intersection in the network of metabolic pathways.
    • Therefore, it unites several key metabolic processes.
  • Organic Acid Metabolism

    • Microbes can harness energy and carbon derived from organic acids by using a variety of dedicated metabolic enzymes.
    • The most commonly metabolized organic acids are the carboxylic acids, which are organic acids containing at least one carboxyl (-COOH) group.
    • Many types of carboxylic acids can be metabolized by microbes, including:
    • Formate metabolism is important in methylotrophic organisms.
    • Give examples of types of organic acid metabolism that are used by microorganisms for a sole source of energy
  • Lipid Metabolism

    • Among these, lipids can be metabolized by microbes for use as a primary energy source.
    • Although not stated explicitly, the "Organic Acid Metabolism" atom in this module introduces the concept of lipid metabolism by describing the process of fatty acid metabolism through β-oxidation.
    • When metabolized, fatty acids yield large quantities of ATP, which is why these molecules are important energy sources.
    • The metabolic process by which fatty acids and their lipidic derivatives are broken down is called β-oxidation.
    • Activation: Before fatty acids can be metabolized, they must be "activated. " This activation step involves the addition of a coenzyme A (CoA) molecule to the end of a long-chain fatty acid, after which the activated fatty acid (fatty acyl-CoA) enters the β-oxidation pathway.
  • Disorders of Acid-Base Balance

    • Acid-base imbalances, including metabolic acidosis and alkalosis, can produce severe, even life-threatening medical conditions.
    • Acid–base imbalance is an abnormality of the human body's normal balance of acids and bases that causes the plasma pH to deviate out of normal range (7.35 to 7.45) .
    • In medicine, metabolic acidosis is a condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body.
    • Metabolic alkalosis is a metabolic condition in which the pH of tissue is elevated beyond the normal range (7.35-7.45 ).
    • Describe the types of disorders of acid-base balance that can occur
  • Chemical Composition of Bone

    • Acid-base imbalances, including metabolic acidosis and alkalosis, can produce severe, even life-threatening medical conditions.
    • Acid-base imbalance is an abnormality of the human body's normal balance of acids and bases that causes the plasma pH to deviate out of normal range (7.35 to 7.45) .
    • In medicine, metabolic acidosis is a condition that occurs when the body produces too much acid or when the kidneys are not removing enough acid from the body.
    • Metabolic alkalosis is a metabolic condition in which the pH of tissue is elevated beyond the normal range (7.35 to 7.45).
    • Differentiate among the acid-base disorders: metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis
  • Inhibiting Essential Metabolite Synthesis

    • An antimetabolite is a chemical that inhibits the use of a metabolite, a chemical that is part of normal metabolism.
    • An antimetabolite is a chemical that inhibits the use of a metabolite, a chemical that is part of normal metabolism.
    • The second type of antimetabolite antibiotics consist of pyrimidine analogues which mimic the structure of metabolic pyrimidines .
    • The purine analogues are the third type of antimetabolite antibiotics and they mimic the structure of metabolic purines .
    • Purine analogues disrupt nucleic acid production.
  • Connecting Lipids to Glucose Metabolism

    • Like sugars and amino acids, the catabolic pathways of lipids are also connected to the glucose catabolism pathways.
    • Thus, synthesis of cholesterol requires an intermediate of glucose metabolism.
    • Triglycerides, a form of long-term energy storage in animals, are made of glycerol and three fatty acids.
    • Animals can make most of the fatty acids they need.
    • Fatty acids are catabolized in a process called beta-oxidation that takes place in the matrix of the mitochondria and converts their fatty acid chains into two carbon units of acetyl groups, while producing NADH and FADH2.
  • Acetyl CoA and the Citric Acid Cycle

    • The citric acid cycle is a key component of the metabolic pathway by which all aerobic organisms generate energy.
    • Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism; it may have originated abiogenically.
    • The name of this metabolic pathway is derived from citric acid, a type of tricarboxylic acid that is first consumed and then regenerated by this sequence of reactions to complete the cycle.
    • The citric acid cycle is a key component of the metabolic pathway by which all aerobic organisms generate energy.
    • The product of this reaction, acetyl-CoA, is the starting point for the citric acid cycle.
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