Cell Energy

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Associate Program Material

Cell Energy Worksheet

Answer the following questions:

Cellular respiration:

What is cellular respiration and what are its three stages?

Cellular respiration is the aerobic harvesting of energy from food molecules. The first stage of cellular respiration is Glycolysis. The second stage of cellular respiration is the citric acid cycle. Lastly, the third stage of cellular respiration is the electron transport.

What is the role of glycolysis? Include the reactants and the products. Where does it occur?

The role of glycolysis is to split the sugars. During this process a six-carbon glucose molecule is broken in half leaving two three-carbon molecules. The three-carbon molecules then donate high-energy electrons to NAD+, the electron carrier, forming NADH. Glycolysis also makes four ATP molecules directly when enzymes transfer phosphate groups from fuel molecules to ADP. It produces a net of two molecules of ATP per molecule of glucose. At the end of glycolysis there are two molecules of pyruvic acid that holds most of the energy of glucose which is harvested in the second stage of cellular respiration.

What is the role of the citric acid cycle? Include the reactants and the products. Where does it occur?

The role of the citric acid cycle is to finish extracting the energy of sugar by breaking the acetic acid molecules all the way down to CO2. During this process acetic acid joins a four carbon acceptor molecule to form a six-carbon product called citric acid. For every acetic acid that enters the cycle as fuel two CO2 molecules eventually exit as a waste product. As this process continues citric acid harvests energy from the fuel. Some of this energy is used to produce ATP directly, but the cycle captures much more energy in the form of NADH and FADH. All the carbon atoms that entered the cycle as fuel are accounted for as CO2 exhaust, and the four-carbon acceptor molecule is recycled. The citric...
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