Adenosine triphosphate (ATP) is the energy-carrying molecule found in the cells of all living things. ATP captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular processes. ATP is a nucleotide that consists of three main structures: the nitrogenous base, adenine; the sugar, ribose; and a chain of three phosphate groups bound to ribose. The phosphate tail of ATP is the actual power source which the cell taps. Available energy is contained in the bonds between the phosphates and is released when they are broken, which occurs through the addition of a water molecule (a process called hydrolysis). Usually only the outer phosphate is removed from ATP to yield energy; when this occurs ATP is converted to adenosine diphosphate (ADP), the form of the nucleotide having only two phosphates.
The importance of ATP (adenosine triphosphate) as the main source of chemical energy in living matter and its involvement in cellular processes has long been recognized. The primary mechanism whereby higher organisms, including humans, generate ATP is through mitochondrial oxidative phosphorylation. For the majority of organs, the main metabolic fuel is glucose, which in the presence of oxygen undergoes complete combustion to CO2 and H2O:
C6H12O6 + 6O2 \(\longrightarrow\)6O2 + 6H2O + energy
The free energy (ΔG) liberated in this exergonic (ΔG is negative) reaction is partially trapped as ATP in two consecutive processes: glycolysis (cytosol) and oxidative phosphorylation (mitochondria). The first produces 2 mol of ATP per mol of glucose, and the second 36 mol of ATP per mol of glucose. Thus, oxidative phosphorylation yields 17-18 times as much useful energy in the form of ATP as can be obtained from the same amount of glucose by glycolysis alone.
he efficiency of glucose metabolism is the ratio of amount of energy produced when 1 mol of glucose oxidised in cell to the enthalpy of combustion of glucose. The energy lost in the process is in the form of heat. This heat is responsible for keeping us warm.
Q 1. Cellular oxidation of glucose is a:
A. spontaneous and endothermic process
B. non spontaneous and exothermic process
C. non spontaneous and endothermic process
D. spontaneous and exothermic process
Q 2. What is the efficiency of glucose metabolism if 1 mole of glucose gives 38ATP energy?(Given: The enthalpy of combustion of glucose is 686 kcal, 1ATP= 7.3kcal)
A. 100%
B. 38%
C. 62%
D. 80
Q 3.Which of the following statement is true?
A. ATP is a nucleoside made up of nitrogenous base adenine and ribose sugar.
B. ATP consists the nitrogenous base, adenine and the sugar, deoxyribose.
C. ATP is a nucleotide which contains a chain of three phosphate groups bound to ribose sugar.
D. The nitrogenous base of ATP is the actual power source.
Q 4. Nearly 95% of the energy released during cellular respiration is due to:
A. glycolysis occurring in cytosol
B. oxidative phosphorylation occurring in cytosol
C. glycolysis in occurring mitochondria
D. oxidative phosphorylation occurring in mitochondria
Q 5. Which of the following statements is correct:
A. ATP is a nucleotide which has three phosphate groups while ADP is a nucleoside which three phosphate groups.
B. ADP contains a nitrogenous bases adenine, ribose sugar and two phosphate groups bound to ribose.
C. ADP is the main source of chemical energy in living matter.
D. ATP and ADP are nucleosides which differ in number of phosphate groups.
