Kreb's cycle

(noun)

The Kreb's cycle is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidization of acetate derived from carbohydrates, fats and proteins into carbon dioxide.

Related Terms

Examples of Kreb's cycle in the following topics:

  • Internal Respiration

    • A diagram of cellular respiration including glycolysis, the Krebs cycle (also called the citric acid cycle), and the electron transport chain.

  • Muscle Fatigue

    • In aerobic respiration, pyruvate produced by glycolysis is converted into additional ATP molecules in the mitochondria via the Krebs Cycle.
    • With insufficient oxygen, pyruvate cannot enter the Krebs cycle and instead accumulates in the muscle fiber.
    • Lactic acid is transported to the liver where it can be stored prior to conversion to glucose in the presence of oxygen via the Cori Cycle.

  • Muscle Metabolism

    • Mitochondria in the muscle fibers can convert pyruvate into ATP in the presence of oxygen via the Krebs Cycle, generating an additional 30 molecules of ATP.
    • Cellular respiration is limited by oxygen availability, so lactic acid can still build up if pyruvate in the Krebs Cycle is insufficient.

  • Absorptive State

    • The liver deaminates amino acids to keto acids to be used in the Kreb's cycle in order to generate energy in the form of ATP.

  • Energy Requirements

    • The produced pyruvate can then be burned aerobically in the citric acid cycle (also known as the tricarboxylic acid cycle or Krebs cycle), liberating a significant amount of energy.

  • Slow-Twitch and Fast-Twitch Muscle Fibers

    • The ATP required for slow-twitch fiber contraction is generated through aerobic respiration (glycolysis and Krebs cycle), whereby 30 molecules of ATP are produced from each glucose molecule in the presence of oxygen.
    • While this may seem counter-intuitive, it is a feedback cycle in place to protect the muscles from over-exertion and resultant damage.

  • Homeostatic Responses to Shock

    • Since oxygen is not abundant, the Kreb's cycle is slowed resulting in lactic acidosis (the accumulation of lactate).

  • Uterine (Menstrual) Cycle

    • The uterine cycle describes a series of changes that occur to the lining of the uterus, or endometrium, during a typical menstrual cycle.
    • Several changes to the uterine lining, or endometrium, occur during the menstrual cycle, referred to as the uterine cycle.
    • Menstrual cycles are counted from the first day of menstrual bleeding and are typically 28 days long.
    • This is referred to as an anovulatory cycle.
    • Anovulatory cycles commonly occur before menopause and in women with polycystic ovary syndrome.

  • Ovarian Cycle

    • The menstrual cycle is the scientific term for the physiological changes that can occur in fertile women for the purposes of sexual reproduction and fertilization.The menstrual cycle, under the control of the endocrine system, is necessary for reproduction.
    • Menstrual cycles are counted from the first day of menstrual bleeding.
    • Ovulation also occurs in the estrous cycle of other female mammals, which differs in many fundamental ways from the menstrual cycle.
    • The luteal phase (or secretory phase) is the latter phase of the menstrual or estrous cycle.
    • The ovarian cycle is the series of changes that occur in the ovary during the menstrual cycle that cause maturation of a follicle, ovulation, and development of the corpus luteum.

  • Periodic Abstinence

    • It was based on knowledge of the menstrual cycle.
    • The first day of red bleeding is considered day one of the menstrual cycle.
    • Days 1 to 7 of a woman's menstrual cycle are considered infertile.
    • Calendar-based methods use records of past menstrual cycles to predict the length of future cycles.
    • However, mid-cycle or anovulatory bleeding can be caused by a number of factors.