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Peer Review

Krebs citric acid cycle

by John Kyrk


Overall Numeric Rating:

4.5 stars
Content Quality: 3.5 stars
Effectiveness: 3.5 stars
Ease of Use: 5 stars
Reviewed: Dec 17, 2012 by Biology Editorial Board
Overview: This site contains an animation of the energy-generating series of chemical reactions of the Krebs citric acid cycle used by eukaryotes. It begins with a written explanation of the generation of 2 molecules of pyruvate from 1 molecule of glucose. In the next diagram, the pyruvate is processed into acetyl coA which provides the substrate for the first step of the Krebs cycle. With the click of the mouse, the subsequent chemical reactions are shown including both three-dimensional cartoons as well as two-dimensional chemical structures of the molecules involved. The animation also includes an image of an energy meter to show the accumulation of electron acceptors at the relevant steps and how many ATP molecules these electron acceptors will generate. The animations are rudimentary (by the author’s own admission) but demonstrate a complicated topic in a clear and accessible way. It would help if detailed written explanations and a small icon of an actual cycle/ circle with the particular step highlighted accompanied every step of the cycle
Type of Material: Interactive Flash animation.
Recommended Uses: This site could be used (a) in a class lecture to demonstrate glucose metabolism, a concept that is difficult to visualize, (b) as an out of class assignment when combined with a worksheet/take-home quiz or (c) a study aid for students
Technical Requirements: Flash plug-in
Identify Major Learning Goals: Students will learn and be able to visualize the chemical reactions and molecules involved in the generation of ATP via the Krebs cycle. Students will also be able to identify which reactions generate electrons and how this translates to ATP production.
Target Student Population: These animations are appropriate for advanced high school students and undergraduate students who are studying biochemistry/ cell biology.
Prerequisite Knowledge or Skills: The animations require basic knowledge of glucose metabolism, including some basic biochemistry

Evaluation and Observation

Content Quality

Rating: 3.5 stars
Strengths: • Clearly demonstrates chemical reactions of each step that are difficult to visualize • Providing the actual chemical structures enriches the animation • Demonstrates the steps of the cycles more precisely than any textbook illustration could • Excellent graphics and interactivity. Well annotated. Accurate and complete.
Concerns: • Animations are rudimentary

Potential Effectiveness as a Teaching Tool

Rating: 3.5 stars
Strengths: • Puts the individual reactions of the Krebs cycle into context of ATP production • Provides material for potential quiz/ test questions • Very thorough and well written. Diagrams and animations are well done. Could easily create assignments based on the animations.
Concerns: • An inset image of the cyclic nature of the Krebs cycle could be included that highlights each step as it is presented so that students may put the series of reactions into context of the cycle. It is not obvious which step begins the Krebs cycle. • The last step of malate generating oxaloacetic acid, which is a substrate for the first step of the Krebs cycle, is not included. This step is critical to understand the cyclical nature of this important metabolic process. • More text explanations of each step would greatly increase the effectiveness of this teaching tool

Ease of Use for Both Students and Faculty

Rating: 5 stars
Strengths: Extremely easy to use, just click to advance the slide • No defective links or bugs • Animations loaded instantaneously • The side bar with the individual steps of the cycle make it easy to navigate through the entire cycle • The author should be commended for providing the animation in 7 different languages!
Concerns: • Clearer instructions indicating that one can rollover the energy meter to see how many ATP are generated from NADH+H+ and FADH2 would help.