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1. PURPOSE

  1. Glycolysis and the TCA cycle are the major pathways of energy production in the body.

  2. The body can't just rely on glucose—other carbohydrates, proteins, and lipids are also important sources of energy

  3. The next 4 chapters will cover these additional pathways involved in energy production and storage

  4. Diseases resulting from dysfunction of these side pathways are a big part of how the Step 1 likes to test metabolism

2. STRATEGY

  1. Each side pathway has a function: What does the body need it for?

  2. Symptoms often relate to limiting the body's ability to perform this function

  3. Don't memorize every enzyme/step of the pathways—focus on the 1–2 enzymes per pathway that are tested

  4. Use mnemonics for groups of diseases like glycogen storage, and make your own if you need to

3. OVERVIEW OF METABOLIC PATHWAYS

  1. Chapter 5 focused on the main path from glucose to ATP production (glycolysis, TCA cycle, and oxidative phosphorylation) as well as glucose synthesis by gluconeogenesis

  2. Chapter 6 focuses on other carbohydrates

    1. Fructose and galactose are common dietary carbohydrates that enter into the glycolysis pathway for energy production

    2. Glycogen is a polysaccharide, consisting of multiple glucose subunits, for energy storage

Table 6-1.Summary of pathways.
Figure 6-1.

Overview of metabolic pathways.

Figure 6-2.

Links between glucose metabolism and other carbohydrates.

4. FRUCTOSE METABOLISM

  1. Fructose is found in “naturally sweet” things—e.g., fruit, honey

  2. Both fructose and galactose (next section) follow very similar process that you can think of in 2 main steps

    1. First, like glucose they have to be phosphorylated and trapped in the cell: Fructokinase does this

    2. Then, it is converted by aldolase B (and others) through intermediates into a compound used in glycolysis (glyceraldehyde-3-P)

  3. The actual process has more steps in ...

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