This week’s main focus is metabolism, which can be defined as “the sum of all chemical reactions in a cell”. A broad topic, surely! Metabolism can be separated into two broad categories: Anabolism = reactions that build new molecules needed for cell growth and maintenance, and Catabolism = reactions by which cells extract the energy needed to make anabolic reactions proceed exergonically.

ATP is a key molecule in metabolism. Phosphate groups are readily released from ATP (and ADP), along with lots of energy. Most anabolic reactions are coupled to an ATP reaction – we will see this in more detail when we study protein synthesis in a couple of weeks. Our main focus here will be on the resulting problem of regenerating new ATP supplies. Every breath we take, for example, has only one metabolic role – to bring in new Oxygen molecules used in ATP synthesis, and to get rid of CO₂ molecules produced as a byproduct of ATP synthesis.

Key concepts for this week: ATP, Oxidation, Glycolysis, Fermentation, Respiration.

Our second focus this week will be to examine how cells respond to specific signals. Each cell in a multicellular organism is, in many ways, an island. Its membrane barrier insulates it from the activities of surrounding cells, and each cell is entirely responsible for expressing selected genes and controlling its biochemical and structural activities. These activities must be regulated with great precision in order for the organism to function, and cells are constantly exposed to chemical signals that arrive in the form of hormones, neutrotransmitters, and other signals to change behavior minute by minute. We shall study in some detail the marvelous machinery by which these chemical signals are detected, transduced, and amplified to create rapid and dramatic changes inside the receiving cell.

See the link at bottom of each page of lecture notes.

Online quiz 5 will become available at 8 a.m. on Tuesday, Oct. 1, and remain available until 8 a.m. on Wednesday, Oct. 2. At some time during this 24 hour time window you must log in to your WebCT account and take the quiz. Quiz deadlines are firm and will not be extended for any reason, so please don’t ask – consult the syllabus if you have any questions about timing, grades, and number of quizzes you are required to take.

You will be allowed 12 minutes to complete the 10 questions. The quiz is “open book” – you are allowed to use your text and notes. However, you must take the quiz by yourself, not with the assistance of another person. Once you have completed your quiz, you will be able to see your grade. If you wish to retake a quiz on this material, you may do so once, as long as you are still within the 24 hour time window – in that case, your quiz grade will be the higher of the two quiz grades.

Each quiz is generated randomly from a large database of questions. As a result, no two quizzes will be identical, and it is quite possible that many if not all of the questions you would see in comparing two different quizzes will be entirely different. Each quiz will cover only the material from the assigned chapters – e.g., Quiz 5 will be based entirely of questions drawn from chapters 9 and 11 (more from 9, since this has more material).