Chapter 9: Cellular Respiration: Harvesting Chemical Energy
Overview: Before getting involved with the details of cellular respiration and photosynthesis, take a second to look at the big picture. Photosynthesis and cellular respiration are key ecological concepts involved with energy flow. Use Figure 9.2 to label the missing parts below.
See page 163 of your text for labeled figure.
Concept 9.1 Catabolic pathways yield energy by oxidizing organic fuels 1.
Explain the difference between fermentation and cellular respiration. Fermentation is a partial degradation of sugars or other organic fuel that occurs without the use of oxygen. Cellular respiration consumes oxygen as a reactant along with the organic fuel.
Give the formula (with names) for the catabolic degradation of glucose by cellular respiration. Organic Compounds + Oxygen Carbon dioxide + Water + Energy
Both cellular respiration and photosynthesis are redox reactions. In redox, reactions pay attention to the flow of electrons. What is the difference between oxidation and reduction? In a redox reaction, the loss of electrons from one substance is called oxidation, and the addition of electrons to another substance is known as reduction.
The following is a generalized formula for a redox reaction:
Xe– + Y X + Ye–
Draw an arrow showing which component (X or Y) is oxidized and which is reduced. Xe- is the reducing agent in this reaction, and Y is the oxidizing agent. 5.
When compounds lose electrons, they lose energy; when compounds gain electrons, they gain energy.
In cellular respiration, electrons are not transferred directly from glucose to oxygen. Following the movement of hydrogens allows you to follow the flow of electrons. The hydrogens are held in the cell temporarily by what electron carrier? What electron carrier is hydrogen transferred to first? NAD+
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7. The correct answer to question 6 is NAD+. It is a coenzyme. What is a coenzyme? What are coenzymes? (If you have forgotten, look back to a few pages in Chapter 8.)
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions. 8.
Describe what happens when NAD+ is reduced. What enzyme is involved? The enzymatic transfer of 2 electrons and 1 proton (H+) from an organic molecule in food to NAD+ reduces the NAD+ to NADH; the second proton (H+) is released. The enzyme involved is dehydrogenase.
It is essential for you to understand the concept of oxidation/reduction and energy transfer. For the following pair, which molecule is the oxidized form, and which is reduced? Which molecule holds higher potential energy? Which is lower in potential energy?
Oxidized or Reduced?
Higher Energy/Lower Energy
10. What is the function of the electron transport chain in cellular respiration? The electron transport chain shuttles electrons down a series of redox reactions that release energy used to make ATP.
11. Electron transport involves a series of electron carriers. Where are these found in eukaryotic cells? Membrane of the mitochondria Where are these found in prokaryotic cells? Plasma membrane
12. What strongly electronegative atom, pulling electrons down the electron transport chain, is the final electron acceptor?
13. Understanding the overall map of how cellular respiration works will make the details easier to learn. Use Figure 9.6 to label the missing information in the figure that follows. See page 167 in your text for the labeled figure.
14. Three types of phosphorylation (adding a phosphate) are covered in the text, and two of these occur in cellular respiration. Explain how the electron transport chain is utilized in oxidative phosphorylation. This mode of ATP synthesis is powered by the redox reactions of the electron...
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