What is Cycle: Definition and 673 Discussions

The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea (NH2)2CO from ammonia (NH3). This cycle occurs in ureotelic organisms. The urea cycle converts highly toxic ammonia to urea for excretion. This cycle was the first metabolic cycle to be discovered (Hans Krebs and Kurt Henseleit, 1932), five years before the discovery of the TCA cycle. This cycle was described in more detail later on by Ratner and Cohen. The urea cycle takes place primarily in the liver and, to a lesser extent, in the kidneys.

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  1. Astronuc

    What are the common challenges and pitfalls in the software development cycle?

    1. Programmer produces code he believes is bug-free. 2. Product is tested. 20 bugs are found. 3. Programmer fixes 10 of the bugs and explains to the testing department that the other 10 aren't really bugs. 4. Testing department finds that five of the fixes didn't work and discovers 15...
  2. R

    Duty Cycle and Frequency of PWM: Explained

    I am getting confused between duty cycle and frequency of a pwm. Isn't duty cycle related to frequency? Can someone explain? Thanks & regards
  3. N

    Diesel Cycle - Heat Engines - Thermo.

    Hello, If anybody could answer this question for me that would be great. I have been wondering about it all morning. In the Diesel cycle for heat engines, on the second stage of operation, the Volume increases while pressure stays the same. I understand how this can be accomplished by raising...
  4. N

    Diesel Cycle - Heat Engines - Thermo.

    Hello, If anybody could answer this question for me that would be great. I have been wondering about it all morning. In the Diesel cycle for heat engines, on the second stage of operation, the Volume increases while pressure stays the same. I understand how this can be accomplished by raising...
  5. Andre

    Geology and Physics, the 100,000 cycle of the ice age.

    ... asked what to study if he wanted to investigate creationism versus evolution. I advised continuing physics and chemistry and avoid having to learn flawed theories as paradigms. So, predictably, I was challenged to expose some of them. I choose for the problems in the 100,000 "ice age" cycle...
  6. J

    Need your help about this – monthly cycle

    How big is possibility to get pregnant if you had unsafe intercourse on 3rd day after your period. Please, please answer me! Thank you !
  7. D

    Carnot Cycle: Understanding Why Real Engines Fall Short

    Why do real engines never attain the efficiency of the Carnot cycle?
  8. M

    What Is the Maximum Work a Carnot Engine Can Perform?

    Pls who can help me with this following problem? A real heat engine operates between temperatures Tc and Th. During a certain time, an amount Qc of heat is released to the cold reservoir. During that time, what is the maximum amount of work that the engine might have performed? Thank you
  9. M

    What is the significance of pursuing reversibility in power plant processes?

    Carnot Cycle is the ideal heat engine cycle with maximum efficiency. We use Rankine Cycle as the working cycle for steam power plant which has significantly lower efficiency that Carnot Cycle. My question is why we don't adopt Carnot Cycle as ideal Steam Power Plant cycle? Thanks in advance!
  10. E

    Calculating Net Power for a Heat Pump Cycle

    Here's my problem: A heat pump cycle whose coefficient of performance is 2.5 delivers energy by heat transfer to a dwelling at a rate of 20 kW. a) Determine the net power required to operate the heat pump, in kW. b) Evaluating electricity at 8 cents per kWh, determine the cost of electricity...
  11. R

    Biochem Help: Cell Cycle Protein Synthesis Q&A

    Biochem help :(?? Hi :smile: I have seen great people on this forum, can anybody please help me with this question? Q- The majority of cellular proteins and RNA are synthesized throughout the cell cycle and are only interrupted briefly during M phase. Synthesis of which of the following...
  12. S

    Humanure and the Human Nutrient Cycle

    For the living, three things are inevitable: death, taxes, and sh1t." Dan Sabbath and Mandel Hall in End Product http://www.weblife.org/humanure/images/fig2-4.jpg When crops are produced from soil, it is imperative that the organic residues resulting from those crops, including...
  13. G

    Hormones in the menstrual cycle

    A few questions on hormones (again :biggrin: ): What stimulates oestrogen production? Is it FSH and LH, or just FSH Does oestrogen inhibit or stimulate LH production? The material I got says that ostrogen inhibits both FSH and LH but from the Edexcel board in the mark scheme it...
  14. M

    Adiabatic Processes in the Carnot Cycle

    I'm not sure I understand why the Carnot cycle involves adiabatic processes at all. I can't seem to find a reason. Also on a related note, how exactly does a Carnot heat pump (refrigerator type) work? Is the sequence the same as a Carnot heat engine?
  15. Loren Booda

    The Impact of Society on Paranoia: A Chicken or the Egg Dilemma

    A person unwillingly projects fear into the hearts of others. Look at his/her eyes, listen to his/her voice, observe the way he/she acts. But which came first, the chicken or the egg? Society is willing to make scapegoats, including those individuals who are forced to endure paranoia. Can...
  16. F

    Carnot cycle, heat and monatomic ideal gas

    Hi, I would appreciate any help with this: A monatomic ideal gas is used as the working substance for the Carnot cycle. Processes A => B and C => D are isothermal, while processes B => C and D => A are adiabatic. During process A => B, there are 400 J of work done by the gas on the...
  17. P

    What factors can affect the efficiency of soxhlet extraction?

    I have a trouble with soxhlet extraction cycle. Liquid in the middle section of soxhlet appratus should returen to the bottom section of soxhlet appratus when it reaches an appropriate height. The question is :The return did not appearence in the whole cycle but the liquid level actually...
  18. Monique

    The Science Behind Menstrual Cramps: Understanding the Role of Prostaglandins

    For the ladies: monthly cycle :) I wonder if this topic will catch on in a male dominated forum, but worth the try :) I actually just found out what the cause is of those very annoying cramps and why women can get sick when their period starts, I thought it is an interesting point to be...
  19. G

    Cardiac Cycle, Tissue Fluid and Oxygen Dissociation Curve

    Hello people I am currently having problems doing my AS exam paper. Can you please help? The question is: During the cardiac cycle, the pressure in the left ventricle falls to a much lower level than in the aorta. Give an explanation for this difference? I have no idea about this...
  20. Another God

    Eukaryotic Cell Cycle Revision

    OK, i need to know everything about the Eukaryotic Cell Cycle : In detail. So this is whereI am going to post what I learn as I go, and where any of you lovely people can post stuff that you know that you think might help me If you have any links to good cell cycle websites, then feel free...
  21. HBar

    The Phosphorus Cycle: Gas or No Gas?

    My last chemistry class was in the 7th grade (currently 10th grader) so bear with me. Last year duing a biology class we were talking about ecology and how phosphorus would cycle through the environment. The reason that the phosphorus cycle is interesting is because phosphorus cannot be a gas...
  22. L

    Carnot Cycle and Line Integrals

    I have to corellate the Carnot cycle with line integrals. This makes sense to me as line integrals can be used to find the work done by a vector field on an object traveling along a certain path. The Carnot cycle places a limit on the efficiency of an engine cycle. My question, how could I...
  23. R

    Does the Corioulis force effect our blood cycle?

    Does the Corioulis force effect our blood cycle[?]
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