Senin, 23 September 2013

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Glycolysis-Aerobic Respiration

Glycolysis-Aerobic Respiration

Glycolysis is a process that breaks down glucose into 2 pyruvate molecules. Glycolysis occurs in some stages. Look at Glycolysis Phase

Stage 1  Glucose entering the  cell  is phosphorylated  with the help of hexokinase enzyme  to form glucose 6-phosphate. The reaction requires energy which is obtained from  the conversion  of ATP  into ADP.

Stage 2  Phosphoglucoisomerase  converts glucose 6-phosphate  into its  isomer,  fructose 6-phosphate

Stage 3  The enzyme  phosphofructokinase uses another ATP molecule to transfer  a phosphate group to fructose 6-phosphate  to form  fructose  1, 6-biphosphate.

Stage 4 Fructose  1,6-biphosphate  (6 carbon molecules)  is broken  down into 3 carbon molecules, namely glyceraldehide-8- phosphate (G3P or PGAL).

Stage 5  Each glyceraldehide-3-phosphate changes  into  lr3-biphosphoglycerate (PGAP)  by  triose phosphate dehydrogenase. In this stage,  there also occurs electron transfer so that NAD changes  into NADH. and  the binding of, anorganic phosphate  from  cytoplasm.

Stage 6  The change of  1,3-bisphosphate- glycerate  into 3-phosphoglycerate  (PGA) occurs by the help of phosphoglycerokinase. In the  stage, the formation  of 2 ATP molecules also occurs by using  available phosphate group in the previous  stage.

Stage 7 The change of 3-phosphoglycerate  into 2-phosphoglycerate occurs because phosphoglyceromutase  relocates  its phosphate  group.

Stage 8 The  change of 2-phosphoglycerate  into 2-phosphoenol-pyruvate (PEP) occurs because of enzyme enolase's help which  releases 2 water molecules.

Stage 9 2-phosphoenol pyruvate changes  into pyruvic acid with the help of pyruvatkinase  enzyme  and produces  2 ATP molecules

Based on those stages, from  the first  to the  fourth  stages  are energy utilization stages producing  2 ATP. Meanwhile, from the fifth to the ninth phases are energy production  phases producing 4 ATP. It can be concluded that a single glucose molecule  in glycolysis produces  a total of 2 molecules of pyruvic acid, 2 molecules  of ATP, and 2 molecules of NADH. Then, each pyruvic acid  is ready to enter  Krebs cycle  in mitochondria

The Input And Output At Glycolysis

Source: Biology. Concepts & connection, 2006.

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