Featured: Osprey Viper 13 Hydration Pack – 100 fl. oz.

Tags: , , ,
Previous Post

SRAM R2C Aero Bar End Shifters Critique

Next Post

Louis Garneau Fit Sensor 7.5 Cycling Short – Women’s Recap


  1. Reply

    Which Cycling Hydration System Is Best ? I can’t see the difference between the expensive and cheaper brands . What should I consider. I don’t ride far, but waterbottle is not too good. Any advice would be welcome

    View Comment
    1. Reply

      I tend to use Camelback. They use an anti bacterial bladder that you can get spares for. However, it is more than just the hydration system. It is also the carrying capability. You don’t ride far, so an entry level 1.5 ltr system is fine. But what else do you want to carry>

      If you are looking at all day, then three ltrs and a reasonable amount of stowage is fine. I have the Camelback Mule NV for this sort of work.

      When I am riding to work I have a 2 ltr with a conventional backpack layout. This allows me to carry clothes and laptop.

      When racing, I don’t want to carry too much, but 1.5 ltrs will do fo rmost racing.

      So the question is what do you want to do with your hydration system, other than carry fluids.


      View Comment
    • Mac
    • February 9, 2014

    Cycling Hydration Pack? I’m looking into getting the Camelback Rogue hydration pack and I was wondering if color really matters. I thought about getting the red just so I would be more visible to motorists but does the color really matter?

    View Comment
    1. Reply

      I always go for bright colors for cycling gear for just that reason.

      Color does matter.

      View Comment
  2. Reply

    What Is The Krebs Cycle?

    View Comment
    1. Reply

      The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle) is a series of chemical reactions of central importance in all living cells that utilize oxygen as part of cellular respiration. In aerobic organisms, the citric acid cycle is part of a metabolic pathway involved in the chemical conversion of carbohydrates, fats and proteins into carbon dioxide and water to generate a form of usable energy. It is the second of three metabolic pathways that are involved in fuel molecule catabolism and ATP production, the other two being glycolysis and oxidative phosphorylation.

      The citric acid cycle also provides precursors for many compounds such as certain amino acids, and some of its reactions are therefore important even in cells performing fermentation.

      Contents [hide]
      1 History
      1.1 A simplified view of the process:
      2 Regulation
      3 Major metabolic pathways converging on the TCA cycle
      4 See also
      5 Reference(s)
      6 External links

      Molecule Enzyme Reaction type Reactants/
      Coenzymes Products/
      I. Citrate 1. Aconitase Dehydration H2O
      II. cis-Aconitate 2. Aconitase Hydration H2O
      III. Isocitrate 3. Isocitrate dehydrogenase Oxidation NAD+ NADH + H+
      IV. Oxalosuccinate 4. Isocitrate dehydrogenase Decarboxylation
      V. ?-Ketoglutarate 5. ?-Ketoglutarate
      dehydrogenase Oxidative
      decarboxylation NAD+ +
      CoA-SH NADH + H+
      + CO2
      VI. Succinyl-CoA 6. Succinyl-CoA synthetase Hydrolysis GDP
      + Pi GTP +
      VII. Succinate 7. Succinate dehydrogenase Oxidation FAD FADH2
      VIII. Fumarate 8. Fumarase Addition (H2O) H2O
      IX. L-Malate 9. Malate dehydrogenase Oxidation NAD+ NADH + H+
      X. Oxaloacetate 10. Citrate synthase Condensation

      The sum of all reactions in the citric acid cycle is:

      Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi + 3 H2O ->
      CoA-SH + 3 NADH + H+ + FADH2 + GTP + 2 CO2 + 3 H+
      Two carbons are oxidized to CO2, and the energy from these reactions is stored in GTP , NADH and FADH2. NADH and FADH2 are coenzymes (molecules that enable or enhance enzymes) that store energy and are utilized in oxidative phosphorylation.

      A simplified view of the process:
      The process begins with the oxidation of pyruvate, producing one CO2, and one acetyl-CoA.
      Acetyl-CoA reacts with the four carbon carboxylic acid, oxaloacetate–to form the six carbon carboxylic acid, citrate.
      Through a series of reactions citrate is converted back to oxaloacetate. This cycle produces 2 CO2 and consumes 3 NAD+, producing 3 NADH and 3 H+.
      It consumes 3 H2O and consumes one FAD, producing one FADH+.
      1st turn end= 1 ATP, 3 NADH, 1 FADH2, 2 CO2
      Since there are two molecules of Pyruvic acid to deal with, the cycle turns once more.
      The complete end result= 2 ATP, 6 NADH, 2 FADH2, 4 CO2
      Many of the enzymes in the TCA cycle are regulated by negative feedback from ATP when the energy charge of the cell is high. Such enzymes include the pyruvate dehydrogenase complex that synthesises the acetyl-CoA needed for the first reaction of the TCA cycle. Also the enzymes citrate synthase, isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase, that regulate the first three steps of the TCA cycle, are inhibited by high concentrations of ATP. This regulation ensures that the TCA cycle will not oxidise excessive amounts of pyruvate and acetyl-CoA when ATP in the cell is plentiful. This type of negative regulation by ATP is by an allosteric mechanism.

      Several enzymes are also negatively regulated when the level of reducing equivalents in a cell are high (high ratio of NADH/NAD+). This mechanism for regulation is due to substrate inhibition by NADH of the enzymes that use NAD+ as a substrate. This includes both the entry point enzymes pyruvate dehydrogenase and citrate synthase.

      Major metabolic pathways converging on the TCA cycle
      Most of the body’s catabolic pathways converge on the TCA cycle, as the diagram shows. Reactions that form intermediates of the cycle are called anaplerotic reactions.

      The citric acid cycle is the second step in carbohydrate catabolism (the breakdown of sugars). Glycolysis breaks glucose (a six-carbon-molecule) down into pyruvate (a three-carbon molecule). In eukaryotes, pyruvate moves into the mitochondria. It is converted into acetyl-CoA and enters the citric acid cycle.

      In protein catabolism, proteins are broken down by protease enzymes into their constituent amino acids. These amino acids are brought into the cells and can be a source of energy by being funnelled into the citric acid cycle.

      In fat catabolism, triglycerides are hydrolyzed to break them into fatty acids and glycerol. In the liver the glycerol can be converted into glucose via dihydroxyacetone phosphate and glyceraldehyde-3-phosphate by way of gluconeogenesis. In many tissues, especially heart tissue, fatty acids are broken down through a process known as beta oxidation which results in acetyl-CoA which can be used in the citric acid cycle. Sometimes beta oxidation can yield propionyl CoA which can result in further glucose production by gluconeogenesis in liver.

      The citric acid cycle is always followed by oxidative phosphorylation. This process extracts the energy from NADH and FADH2, recreating NAD+ and FAD, so that the cycle can continue. The citric acid cycle itself does not use oxygen, but oxidative phosphorylation does.

      The total energy gained from the complete breakdown of one molecule of glucose by glycolysis, the citric acid cycle and oxidative phosphorylation equals about 36 ATP molecules. The citric acid cycle is called an amphibolic pathway because it participates in both catabolism and anabolism.

      View Comment
    • Pete
    • February 11, 2014

    Waterproof, Large, Hydration Packs For Cycling? Hello,

    Can anyone tell me a large Hydration pack which is waterproof and suitable for cycling. I am talking 25L plus capacity with 3L water reservoir.

    I know about the Ergon BC3 (but i need other options). http://www.dotbike.com/p/5523?utm_source=google&utm_medium=base&utm_campaign=FGL

    Any advice is appreciated, thank you.
    also if not available in the UK i would buy online from other countries.

    View Comment
    1. Reply

      I don’t know if it has 25L but it has a 3L water reservoir, check out the Camelbak Mule This pack is made specifically for mountain biking. I have had mine for a couple of years, I love it! Carries enough water and has enough room for everything I need.

      Here’s the link


      View Comment
    • Tori
    • February 13, 2014

    HELP With The KREBS CYCLE??!!!!!? Ok.. all i need is some basic info on the krebs cycle process. please help because so many people have told me different answers and have just completely confused me so could you guys please help and try to make it less complicated. ty so very much :)))

    View Comment
    1. Reply

      Krebs cycle –

      – Condensation – Two carbon acetyl CoA combines with 4 carbon oxaloacetic acid in presence of enzyme citrate synthetase to form 6-carbon citric acid. Water molecule is used, CoA is released.

      – Dehydration -Citric acid undergoes dehydration to form a 6-carbon compound cis-aconitic acid in presence of enzyme aconitase and Fe++ ions.

      – Hydration – Cis-aconitic acid is converted to iso-citric acid by water molecule. Enzyme aconitase and Fe++ ions are used.

      – Dehydrogenation -Isocitric acid undergoes oxidation in presence of iso-citric dehydrogenase to form oxalo-succinic acid. This releases hydrogen atoms that are used for reduction of NAD and NADH2.

      – Decarboxylation – Oxalosuccinic acid, which is 6-carbon compound undergoes decarboxylation to form 5-carbon acid like alpha-ketoglutaric acid and carbondioxide. Enzyme used is decarboxylase with Mn++.

      – Dehyrogenation and Decarboxylation – 4-carbon succinyl CoA is formed by oxidation decarboxylation alpha-ketoglutaric acid. In this step one molecule of NAD is reduced to NADH2 and Carbondioxide is released. One molecule of CoA is used and alpha-ketoglutaric dehydrogenase catalyses the reaction.

      – Formation of GTP -Succinyl CoA is hydrolysed to succinic acid in presence of enzyme succinnc thiokinase. GDP is converted to GTP. water molecule is used up and CoA is given out.

      – Dehydrogenation -Succinic acid undergoes dehydrogenation in presence of enzyme succinic acid dehydrogenase to form fumaric acid. Hydrogen atom released are accepted by FAD and gets reduced to FADH2.

      – Hydration – With inclusion of a molecule of water in presence of enzyme fumarase, fumaric acid is converted into malic acid.

      – Dehydrogenation -Malic acid undergoes dehydrogenation to produce oxaloacetic acid which combines with acetyl CoA to produce citric acid. Hydrogen released is used to reduce NAD.
      – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

      View Comment
    • Boom
    • February 15, 2014

    What Steps In The Citric Acid Cycle Are Reversible And Irreversible?

    View Comment
    1. Reply

      There are eight steps in the cycle, all except three are reversible.

      Step-wise reactions of the TCA cycle

      1. Aldol condensation of oxaloacetate with acetylCoA followed by hydrolysis of CoASH to give citrate. Enzyme: citrate synthase. This is the first irreversible step

      2. Dehydration followed by hydration leads to interchange of -H and -OH and isomerization of citrate to isocitrate. Enzyme called aconitase because of formation of intermediate called cis-aconitate.

      3. Oxidative decarboxylation of isocitrate is catalyzed by isocitrate dehydrogenase to form ?-keto-glutarate. This is the second irreversible step. NAD+ is reduced to NADH and one C is removed as CO2.

      4. This is the second oxidative decarboxylaion and 3rd irreversible step catalyzed by a-ketoglutarate dehydrogenase. The enzyme is a complex similar to PDH and the coenzymes TPP, lipoamide and FAD are required. CO2 is removed, NADH is formed from NAD+ and a thioester bond is formed with CoASH to form succinylCoA.

      5. Hydrolysis of the thioester of Succinyl CoA releases ~31 kJ/mol which is captured for the synthesis of GTP. The enzyme is succinyl CoA synthetase.

      6. Succinate is oxidized to fumarate by succinate dehydrogenase. A double bond is introduced between the 2 central carbons and FAD is reduced to FADH2 Succinate .Dehydrogenase is an electron carrier of the ETC and is the only enzyme of the TCA cycle present on the inner mitochondrial membrane rather than in the matrix.

      7. Fumarate is hydrated to malate by the enzyme fumarase.

      8. In the final step, malate is oxidized to oxaloacetate with the coupled reduction of NAD+ to NADH by the enzyme malate dehydrogenase

      o Overall reaction: AcetylCoA + 3NAD+ + FAD + GDP + Pi + 2H2O AE 2CO2 + CoASH + 3NADH+ 2H+ + FADH2 + GTP

      View Comment
  3. Reply

    Preventing Windburn While Cycling? Now that the weather has gotten colder, I need some advice on preventing windburn on my face. I have very fair and sensitive skin, and after my last two rides with temps in the low 60’s, my face has gotten windburned. Anyone know how to prevent this?
    Ok folks, I know all about the face masks, but I think wearing that when it’s in the 60’s Fahrenheit is a bit much! I’d pass out from heat exhaustion with something that heavy on! I am looking for something like a cream or lotion I can put on….

    View Comment
    1. Reply

      B-vitamins, lotion, and hydration all make for healthy durable skin. Other than that, cover up with something. If your skin is dry, sunscreen may help some too because often windburn is combined with light sunburn.

      I get it sometimes in the cooler months on the bike but usually not too bad. I get it a lot worse when hiking/backpacking above treeline and sometimes it takes days to heal. Just keep your skin moist if you can and be sure to get a healthy balanced diet.

      Good luck! :o)

      View Comment
  4. Reply

    Hydration Drinks For Long Distance Cycling? I usually just drink water on long cycling rides, but hear that drink mixes are essential. Doing a 100 mile ride this weekend and would like to hear what you use and how you like it? when do you drink it, how often, etc.

    I am looking at getting Cytomax?


    View Comment
    1. Reply


      I drink energy drinks on rides over fifty miles. I take GU gels with me. I prefer Good n Plenty pre-peeled and in a baggie in my jersey pocket. Fresh fruit- make mine banana, Many of my friends like to take M&M’s and Trail Mix with them. Stop along the way as many times as needed for bringing on more water or food breaks.

      Eat a big Pasta meal tonight. In the A.M. oatmeal, fresh fruit, o.j. and coffee.

      Enjoy the ride! Should be a great day.


      View Comment
  5. Sick Baby… Hydration Overnight? My daughter is 12months and quite sick at the minute ith a tummy bug. She hasn’t vomited too much and not at all in the last 24 hours but she still had diarrhea. She is taking water well…I cannot get her to take pedialite and the doc has told me that so far, it isn’t necessary in her case. She is relatively well hydrated….still having wet nappies but not quite as wet, her mouth is not dry and her skin elasticity is ok.

    My question is, do you think it is necessary to wake her overnight to give her fluids. I prob should’ve asked the doc this but just didn’t think about it. I can call the nurse hotline if no-one has an answer for me but thought I’d try this first because it is often a big wait.

    Chance are it wont matter anyways because she will probably wake a fair bit and I’ll offer her water then, but just wondering what your thoughts were if she did happen to sleep well tonight
    Thanks…she drinks commercial rice milk anyways because she is dairy and soy intolerant…so that’s great to know. Yeah I don’t think I’ll wake her. If she was showing more signs of dehyrdration I would…well then again…I’d prob have her at the hospital if it got to the point where I thought it necessary to wake her

    View Comment
    1. Reply

      You could send her to bed with a sippy cup so that she has it if she wakes thirsty. If you have a humidifier, running that in her room will help prevent some dry mouth type of dehydration.

      If you can catch her in her light sleep cycles where she is just barely asleep, you could go ahead and wake her up a bit and offer her a drink then. But, you might want to be careful about waking her from a deep sleep since you may cause more problems than you’d fix by giving her a drink.

      I’m sure I read this on http://rehydrate.org , but I can’t find it there right now. Rice water/milk can help with rehydration or preventing dehydration. If you feel up to it, you can combine 1/4 cup uncooked brown rice with 4 cups of water, bring to a boil, reduce heat and simmer for 1 hour, then pour the entire thing (it’ll be hot, so be careful) into a blender. Blend it, then strain out the left over rice. The rice water/milk can be sweetend with a bit of sugar and vanilla, doesn’t taste too awful, and has some good rehydrating properties.
      I’ll see if I can find some sort of resource for that.

      Edit: Okay, here we go.

      “The following traditional remedies make highly effective oral rehydration solutions and are suitable drinks to prevent a child from losing too much liquid during diarrhoea:

      * Breastmilk
      * Gruels (diluted mixtures of cooked cereals and water)
      * Carrot Soup
      * Rice water – congee”

      Here’s a recipe for actual congee, but it would appear really gross to me compared to actual rice water.
      And here’s a recipe for rice water/milk

      View Comment
  6. Reply

    Why Are Cycles Are Important In Metabolism? Hey everyone,
    Why do we have metabolic cycles and not, say, a chain of linear reactions? If anyone has a detailed explanation, or something ton contribute, I’d really appreciate it!

    View Comment
    1. Reply

      The reason there are cycles rather than a linear chain of reactions in metabolic processes is because each component of the cycle is a substrate for the subsequent reaction in the cycle. A great example of this is the Krebs cycle.

      At the beginning of the cycle, a transfer between a two carbon acetyl group from acetyl-CoA (acetyl coenzyme A) and oxaloacetate form citrate. Then, throughout the cycle, the citrate reacts with different enzymes and releases water and CO2 as it goes, and also picks up/releases electrons from a compound nicknamed NADH or NAD (depending upon if it is oxidized or reduced with a hydrogen ion). Finally, the substrate fumerate reacts with the enzyme fumerase to form the product malate (by means of a hydration reaction). The malate combines with NAD and the enzyme malate dehydrogenase to form oxaloacetate, which brings us to the end of the first cycle of the Krebs cycle. As you know, the oxaloacetate produced at the end of the cycle will react with the acetyl group in acetyl-CoA to form citrate. Thus, the start of the second cycle of the Krebs cycle.

      The reason there are 2 cycles in this metabolic process is because two acetyl-CoA molecules are produced from a each glucose molecule formed in glycolysis (which is a preceding metabolic process to the Krebs cycle). Since 2 glucose molecules are produced from glycolysis, two cycles are required per glucose molecule.

      So, in conclusion, the Krebs cycle starts with oxaloacetate and acetyl-CoA to form citrate. The citrate is reacted with other enzymes to form other compounds that eventually brings us to the formation of malate, which reacts with the enzyme malate dehydrogenase to form oxaloacetate, which will react with the other molecule of acetyl-CoA, thus beginning the second turn of the Krebs cycle.

      Hopefully I didn’t confuse you =]

      View Comment

Leave a Reply