What is Metabolism: Definition and 29 Discussions

Metabolism (, from Greek: μεταβολή metabolē, "change") is the set of life-sustaining chemical reactions in organisms. The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to building blocks for proteins, lipids, nucleic acids, and some carbohydrates; and the elimination of metabolic wastes. These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transport of substances into and between different cells, in which case the above described set of reactions within the cells is called intermediary metabolism or intermediate metabolism. In various diseases, such as type II diabetes, metabolic syndrome, and cancer, normal metabolism is disrupted.Metabolic reactions may be categorized as catabolic – the breaking down of compounds (for example, the breaking down of glucose to pyruvate by cellular respiration); or anabolic – the building up (synthesis) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy.
The chemical reactions of metabolism are organized into metabolic pathways, in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts – they allow a reaction to proceed more rapidly – and they also allow the regulation of the rate of a metabolic reaction, for example in response to changes in the cell's environment or to signals from other cells.
The metabolic system of a particular organism determines which substances it will find nutritious and which poisonous. For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The basal metabolic rate of an organism is the measure of the amount of energy consumed by all of these chemical reactions.
A striking feature of metabolism is the similarity of the basic metabolic pathways among vastly different species. For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all known organisms, being found in species as diverse as the unicellular bacterium Escherichia coli and huge multicellular organisms like elephants. These similarities in metabolic pathways are likely due to their early appearance in evolutionary history, and their retention is likely due to their efficacy. The metabolism of cancer cells is different from the metabolism of normal cells, and these differences can be used to find targets for therapeutic intervention in cancer.

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  1. mktsgm

    Metabolism and energy currency

    This question might sound silly, but I think I am really missing some points about the energy requirements of metabolism. Please help me to understand better. It is said that all catabolic (break down) reactions are inherently exergonic, ie., they release energy. Similarly, all anabolic...
  2. D

    How does the body speed up metabolism?

    Hi everyone Could someone explain what happens in the body when metabolism speeds up? For example, does it produce more stomach acid? Or does it produce more concentrated stomach acid? Thanks
  3. DennisN

    Metabolic pathways - Interactive map

    Are you like me and think biology can be messy and difficult? Well, you're right. :nb) Here is a very cool, very large interactive map of metabolic pathways, which a friend of mine sent to me today: http://metabolic-pathway.com/fullMap.html And if you want to be extremely careful with your...
  4. K

    Cell Metabolism and Static, Unidirectional Magnetic Fields

    Can anyone explain why an artificial magnetic field may or may not promote an increase in cellular metabolism?
  5. mktsgm

    Medical Are there any other Macronutrients?

    I have a few questions on energy from foods. Do we have any other macronutrients that contribute energy to the body other than carbohydrates, proteins and fats in our body? What is the role of Hydrochloric acid (HCL) in our stomach? Is the HCL involved in all three above macronutrient digestion?
  6. L

    Glucose Metabolism- correct or is my understanding flawed?

    I am trying to understand about glucose metabolism! I have been researching this stuff forever! X( Would you see if my explanations are right, and if not, tell my why? Thank you SO much! That would be a HUGE help! Is it true that uptake and release of gas/nutrients only occur in the...
  7. E

    Carbon monoxide metabolism

    Carbon monoxide can make carboxyhemoglobin in the human body. Do plants have a similar composition? Would smoke from fires and exhaust from fossil fuel engines have an effect on a plants ability to absorb the CO2 or O2 it needs?
  8. U

    Metabolism of HFCS & Margarine: Health Impacts

    Hello, I'm asked to write about the following: "High fructose corn syrup and margarine are two commonly used food ingredients that contribute to both inflammation and obesity." Write one page each on the metabolism of each of these foods in your body, and cite at least one recent paper...
  9. S

    Thought Experiment: Should Atheists End all Metabolism in Their Brain?

    Hello, I'm an atheist: a mentally disabled one with depression and no future. So perhaps this may bias my point of view: When we atheists die, we will have no memories and conscious awareness of our success and failures in life because our consciousness and memories are lost for eternity...
  10. S

    What is the total basal metabolism of this man over a 24 hour period?

    Homework Statement A model for the basal metabolism rate, in kcal/h, of a young man is given by the formula below, where t is the time in hours measured from 5:00 AM. What is the total basal metabolism of this man over a 24 hour period? R(t) = 85 - 0.18cos (Pi*t/12) ∫(0to24) R(t)dt= ...
  11. G

    Cell adhesion intimately linked to metabolism?

    Integrin-PI3K-Akt signal transduction is well known. Akt signaling has been heavily reviewed and is well known to play a role in metabolism. So why do I have difficulty finding any research that has linked cell adhesion to metabolism? It would make sense. If a cell became cancerous, one way...
  12. N

    Local Anaesthetic Metabolism

    I am having a little difficulty understanding this concept, and was hoping someone might be able to help me. If this is not the cost appropriate section for this question, I apologise in advance! What I was wondering is, what happens to a local anaesthetic molecule after it dissociates from...
  13. S

    What does one carbon metabolism of folic acid mean?

    What does that mean. Transfer of 1-carbon unit. What is a 1-carbon unit, are they referring to carbon number 1(according to nomenclature) of the molecule being transferred or a single carbon atom from the molecule is transferred? Can anyone explain. Thanks :smile:
  14. N

    Chemistry Question on metabolism of glucose

    Homework Statement The metabolism of glucose, C6H12O6, yields Co2(g) and H2O(l) as products. Heat released in the process is converted to useful work with about 70% efficiency. Calculate the mass of glucose metabolized by a 59.0-kg person in climbing a mountain with an elevation gain of...
  15. G

    Flicks diffusion equation - metabolism rate

    So i have an organic chemical in a bio-film reactor being diffused into a bio-film and also being metabolized at constant rate R by bacteria. the concentration into the reactor Cin = 2mg/L with f-in at 20 m^3/hr the concentration in the reactor is C1 C3 is the concentration in the...
  16. D

    Humans & Cellulose Metabolism: Are There Documented Cases?

    As a species evolves away from maladaptive forms, there may be occasional reversions. A well-known example is the tail in humans. A very small percentage of humans are born with a tail. My question is this. The appendix is possibly a vestige of an era when human ancestors were able to digest...
  17. B

    Energy Metabolism: Catabolic & Anabolic Reactions

    Is it safe to assume that catabolic reactions are always exergonic and anabolic reactions are always endergonic? Also, I had a question on energy metabolism. Since the mitochondria is where energy is stored, does that mean that metabolic (energy) pathways only occur in the mitochondria? Or is...
  18. J

    Metabolism of Body Fat: Process & Effects

    Hi, Does anybody know or have a link on the chemical/metabolic pathways for human body fat? I've been trying to look this up and can't seem to find an answer. I'm curious about this concept. Human body fat is a form of animal fat, so metabolizing it should raise your LDL cholesterol...
  19. C

    Help with undstanding Metabolism?

    I am studying for an exam tomorrow and am having a hard time understanding a couple of things. What exactly if the difference in the chemistry and metabloic role of NADH and NADPH? and How are metabolic pathways (glycolysis, PPP, gluconeogenesis, citrc acid cycle, and oxid...
  20. N

    Boosting Metabolism: Low Calories & Exercise

    When a person consumes less than 1000-1200 for a long period of time, their body inturn goes to starvation mode right? And your metabolic rate slows down? Then, by exercising your metablism will increase. If you lower your intake but increase the amount of exercise (or even taken to the extreme...
  21. L

    When does your metabolism slow down?

    When does your metabolism typically begin to slow down and gaining weight becomes easier?
  22. G

    How Can P450 Enzyme Activity Be Inhibited for Slowing Drug Metabolism?

    Anyone know any good ways to inhibit the P450 enzyme in order to slow down drug metabolism? I know that cannabidiols can be used to inhibit P450, but are there any other ways?? Anyone have any good journal references (I don't have access to scifinder)? Any help would be appreciated...
  23. T

    How Much Water Evaporates to Remove Heat from Basal Metabolism?

    I can't seem to get this problem to work out...any suggestions? -HOw much water would have to evaporate from the skin/min to take away all of the heat generated by basl metabolism (60kcal/hr) for a 65Kg person.
  24. A

    Maximizing Metabolism: The Truth About Eating Frequency and Weight Loss

    Hey guys; I've always heard things similar to that instead of eating three meals a day, you should spread the same amount of food over say five meals a day. Eat smaller portions, but more often. I don't understand why (if) this works. If you keep eating small amounts all day long, you...
  25. C

    Solving High Metabolism & Hunger Problems in Athletes

    Hello. Lately, every night before I slept, I felt very hungry. It use to be solved by just eating a piece of bread. But now, I ate a very big serving for dinner and is still hungry before I slept, even toasting some bread wouldn't help. Not just in the evening, now, when I wake up, afternoon, I...
  26. M

    Maximizing Your Metabolism: Tips for Losing Inches in a Short Timeframe

    Hey there, My boyfriend is going to be coming home in roughly 3 weeks. I was wondering if it would be possible to lose and inch or so off my waist before he comes home. Is that a realistic achieveable goal? :uhh: Your thoughts would most appreciated. Suggestions on how to do this would be...
  27. S

    Heredity, containment, metabolism.

    Not sure you guys have seen or talked about this already, but I just got on-line access to New Scientist Magazine. The Feb 12 2005 issue was about creating artificial life. Here's a short summary about a Los Alamos team's attempt to do so: The key difference between life and non-life is...
  28. J

    Bacterial metabolism, Questions ?

    Please help, I have some problems with understanding bacterial metabolism. If we have bacteria who for example gets energy by oxidizing H2S to S, and than we have one that gets it’s energy by reducing S to H2S, doesn’t that seems like perpetuum mobile. I’m probably missing something here, but I...
  29. STAii

    Does Breaking Chemical Bonds Produce Energy in Catabolism?

    Greetings. Recently, my Biology teacher was explaining about metabolism (unlike my other teachers, this one is a good teacher). He said : "catabolism produces energy on the form of ATP because it involves breaking chemical bonds". Now i feel a little confused about this. As far as i know...
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