Energy transformations

Glycolysis, Respiration, Anaerobic Pathways

Glycolysis is a 10 step process made up of nine reactions that are each gathered or assembled by a specific enzyme. EVERY organism has glycolysis developing in its cytoplasm and the literal meaning of glycolysis is “splitting sugars”

In this process, glucose, which is a six-carbon sugar, is divided in two so that it creates two three-carbon sugars. Glycolysis generates two molecules of ATP, two molecules of NADH, which are high energy, and two molecules of pyruvic acid. It is possible for glycolysis to happen with oxygen, known as the first stage of cellular respiration, or without oxygen, which is known as fermentation.

Let’s list some important facts about glycolysis.

1) It makes two pyruvic acid molecules after the six-carbon glucose is split into two three-molecule carbons in step 4 of glycolysis.

2) ATP is required in steps 1 and 3 but is also produced twice in each; steps 6 and 9. So, Steps 1 & 3 = -2 ATP but Steps 6 & 9 = +4 ATP Thus the net energy that is being produced is 2 ATP.

3) All of the steps of glycolysis take place in the cytoplasm of the cell.

4) Glycolysis that involves oxygen (aerobic) is 4 times more productive than that which doesn’t involve oxygen (anaerobic).

Cellular respiration is the most effective method for cells, both prokaryotic and eukaryotic, to gather energy. Glycolysis is the first of the three main stages of cellular respiration. The following two are the citric acid cycle and electron transport.

The Citric Acid Cycle, also known as the Krebs Cycle, starts after the two three-carbon sugar molecules are changed to a slightly different compound in the glycolysis stage. Some compounds that are able to store high energy electrons are produced with two ATP molecules. These compounds which are know as NDP and FDP. These carry the high energy to the next phase. This cycle only happens if oxygen is present but doesn’t utilize it.

Photosynthesis

What is photosynthesis? Well, this is the way in which green plants use the sunlight to make sugar. This sugar is then used by cellular respiration to convert into ATP. This process happens in the chloroplasts which contain chlorophyll. Chlorophyll is the substance that gives a plant its green colour.

The chlorophyll takes in sunlight and integrates it with carbon dioxide and water in order to make sugar and oxygen. The plant then uses the sugar and gives off oxygen as a by-product. This is the only way oxygen is made for humans and other animals to breathe so photosynthesis is crucial to life as we know it. The chemical reaction can be represented as follows:

6H2O + 6CO2 -> C6H12O6 + 6O2

Or in other words:

6 molecules of water and 6 molecules of carbon dioxide makes 1 molecule of sugar and 6 molecules of oxygen.

Continue to Cell Devision study guide page



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