metabolism

Examples of metabolism in the following topics:

• Metabolic Pathways

  • A metabolic pathway is a step-by-step series of interconnected biochemical reactions that convert a substrate molecule or molecules through a series of metabolic intermediates, eventually yielding a final product or products.
  • For example, one metabolic pathway for carbohydrates breaks large molecules down into glucose.
  • Another metabolic pathway might build glucose into large carbohydrate molecules for storage.
  • Consequently, metabolism is composed of these two opposite pathways:
  • Chemical reactions in metabolic pathways rarely take place spontaneously.

• The Role of Energy and Metabolism

  • All organisms require energy to complete tasks; metabolism is the set of the chemical reactions that release energy for cellular processes.
  • Metabolism is the set of life-sustaining chemical processes that enables organisms transform the chemical energy stored in molecules into energy that can be used for cellular processes.
  • Animals consume food to replenish energy; their metabolism breaks down the carbohydrates, lipids, proteins, and nucleic acids to provide chemical energy for these processes.
  • All of the chemical reactions that take place inside cells, including those that use energy and those that release energy, are the cell's metabolism.
  • Many cellular process require a steady supply of energy provided by the cell's metabolism.

• Cell Signaling and Cellular Metabolism

  • The rush of adrenaline that leads to greater glucose availability is an example of an increase in metabolism.
  • As the environments of most organisms are constantly changing, the reactions of metabolism must be finely regulated to maintain a constant set of conditions within cells.
  • Metabolic regulation also allows organisms to respond to signals and interact actively with their environments.
  • Two closely-linked concepts are important for understanding how metabolic pathways are controlled.
  • The result of one such signaling pathway affects muscle cells and is a good example of an increase in cellular metabolism.

• Connecting Other Sugars to Glucose Metabolism

  • Metabolic pathways should be thought of as porous; that is, substances enter from other pathways, and intermediates leave for other pathways.
  • Infants have an enzyme in the small intestine that metabolizes lactose to galactose and glucose.
  • Fructose is absorbed from the small intestine and then passes to the liver to be metabolized, primarily to glycogen.
  • Although the metabolism of fructose and glucose share many of the same intermediate structures, they have very different metabolic fates in human metabolism.

• 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.
  • When deaminated, amino acids can enter the pathways of glucose metabolism as pyruvate, acetyl CoA, or several components of the citric acid cycle.

• Cell Structure, Metabolism, and Motility

  • Protists are an incredibly diverse set of eukaryotes of various sizes, cell structures, metabolisms, and methods of motility.
  • The vesicle containing the ingested particle, the phagosome, then fuses with a lysosome containing hydrolytic enzymes to produce a phagolysosome, which breaks down the food particle into small molecules that diffuse into the cytoplasm for use in cellular metabolism.
  • Describe the metabolism and structure of protists, explaining the structures that provide their motility

• Metabolism of Carbohydrates

  • When these molecules are broken down during metabolism, the energy in the chemical bonds is released and can be harnessed for cellular processes.
  • The metabolism of any monosaccharide (simple sugar) can produce energy for the cell to use.
  • Excess carbohydrates are stored as starch in plants and as glycogen in animals, ready for metabolism if the energy demands of the organism suddenly increase.
  • The breakdown of glucose during metabolism is call cellular respiration can be described by the equation:

• Connecting Lipids to Glucose Metabolism

  • Thus, synthesis of cholesterol requires an intermediate of glucose metabolism.

• Peroxisomes

  • Peroxisomes neutralize harmful toxins and carry out lipid metabolism and oxidation reactions that break down fatty acids and amino acids.
  • Peroxisomes perform important functions, including lipid metabolism and chemical detoxification.
  • Reactive oxygen species (ROS), such as peroxides and free radicals, are the highly-reactive products of many normal cellular processes, including the mitochondrial reactions that produce ATP and oxygen metabolism.
  • Peroxisomes are membrane-bound organelles that contain an abundance of enzymes for detoxifying harmful substances and lipid metabolism.

• Hormone Functions

  • The endocrine system plays a role in growth, metabolism, and other processes by releasing hormones into the blood.
  • By releasing hormones, the endocrine system plays a role in growth, metabolism, and sexual development.
  • Examples of endocrine glands include the adrenal glands, which produce hormones, such as epinephrine and norepinephrine that regulate responses to stress, and the thyroid gland, which produces thyroid hormones that regulate metabolic rates.