Question

in a 1200 word report, give an overview of the biochemical events that occur at the start point of a running race (that is, before the runner has commenced running), during the race, after 5 minutes and after 45 minutes, in terms of:

• ● the processes involved in the mobilisation and/or use of both types of fuels (carbohydrates and lipids).

• ● a brief overview of the biochemical pathways used to degrade these fuel molecules

• ● a comparison of the yield of ATP for both fuels

take into account answering the following in the report:

• What are the main time points you have to cover?

• ● What fuels are used at each time point?

• ● What pathways are required to mobilize the fuel?

• ● What pathways are involved in breakdown of the fuel?

• ● What cellular compartment and tissue types are involved?

• ● What are the inputs and outputs of each pathway?

• ● How much energy is derived from each fuel?

Answer 1

ANSWER : Fuel metabolism is highly regulated to ensure adequate energy for cellular function. The contribution of the major metabolic fuels-glucose, lactate, and fatty acids- often reflects their circulating levels. Carbohydrates are the sugars, starches, fibers found in fruits, grains, vegetables and milk products. Whereas, Lipids are molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells. Carbohydrates provide fuel for the central nervous system and energy for working muscles.The four primary functions of carbohydrates in the body are to provide energy, store energy, build macromolecules, and spare protien and fat for other uses. Lipids, also known as fats, play many important roles in your body, from providing energy to producing hormones. You wouldn't be able to digest and absorb food properly without lipids. The primary functions of lipids include storing energy, signaling, and acting as structural components of cell membranes. Carbohydrate metabolism is the whole of the biochemical processes responsible for the metabolic formation, breakdown and interconversion of carbohydrates in living organisms. Glycolysis is the process of breaking down a glucose molecule into two pyruvate molecules, while storing energy released during this process as ATP and NADH. Nearly all organisms that break down glucose utilize glycolysis. In some tissues and organisms, glycolysis is the sole method of energy production. This pathway is common to both anaerobic and aerobic respiration. Digestion is the first step to lipid metabolism, and it is the process of breaking the triglycerides down into smaller monoglyceride units with the help of lipase enzymes. Digestion of fats begin in the mouth through chemical digestion by lingual lipase.The catabolic pathways for all of these molecules eventually connect into glycolysis and the Krebs cycle. Several types of lipids can be microbially degraded. Triglycerides are degraded by extracellular lipases, releasing fatty acids from the glycerol backbone. For each molecule of glucose that is broken down, two molecules of pyruvate, two molecules of ATP, and two molecules of NADH are produced. While a total of four ATPs are produced by glycolysis, two are needed to begin glycolysis, so there is a net yield of two ATP molecules. If we consider lipids, for example, an 18 carbon fatty acid (stearic acid) yields 146 ATPs, while a 20 carbon fatty acid will yield 163 ATPs. In the fatty acid spiral, there is only one reaction which directly uses ATP and that is in the initiating step. A large amount of energy is released and restored as ATP during the oxidation of fatty acids. Carbohydrates are covalently linked to protiens (glycoprotiens) or lipids (glycolipids) and also an important part of cell membranes and function as adhesion and address loci for cells. The Fluid Mosaic Model describes membranes as a fluid lipid bilayer with floating protiens and carbohydrates. Membrane lipids are a group of compounds which form the double-layered surface of all cells. The three major classes of membrane lipids are phospholipids,glycolipids and cholesterol. One gram of carbohydrates provides four calories of energy. Maximal glycogen storage is approximately 15 grams per kilogram of body weight. Whereas, the amount of lipids stored as an energy reserve far exceeds the energy stored as glycogen since the human body is simply not capable of storing as much glycogen compared to lipids. Lipids yield 9 kcal of energy per gram.