Professor Saltzman continues his discussion of cell communication in the body, extending the description to the nervous and immune system. Professor Saltzman describes the mode of signal transmission in neurons: action potential in the axon, and neurotransmitter release at the synaptic cleft. He also introduces elements of the innate and adaptive immune system. The adaptive immune system is presented as a host/foreign antigen recognition system involving immune cells (T, B, and macrophages), antibodies, and the major histocompatibility complex 1 and 2.

Professor Saltzman describes the processes of fertilization and embryogenesis. Professor Saltzman then talks about the definition and classification of different types of stem cells, where stem cells are found in the body, and the potential for use of stem cells in treating diseases. Some challenges in this type of therapy are also discussed. Finally, Professor Saltzman introduces the exponential equation for cell growth, dX/dt = e^μt, and the concept of cell “doubling time.”

Professor Saltzman continues his presentation on DNA technology by discussing control of gene expression using two methods of RNA silencing: anti-sense therapy and RNA interference. Molecular cloning techniques to mass-produce proteins using plasmid, restriction enzymes, ligase, and antibiotic selection in bacteria are discussed. Steps and molecules involved in polymerase chain reaction are also described. Professor Saltzman explains how to detect mutations in genomic DNA, such as in sickle cell anemia patients, by gel electrophoresis and Southern blotting.

Class begins with discussion of students’ answers to the two questions given as assignment in the previous lecture. Professor Saltzman talks about the basic concept of biomedical engineering and two separate aspects of it: gaining better understanding of human physiology and developing ways to improve human health. He then introduces the termhomeostasis, and talks about parameters that are involved in controlling this state. Finally, the structure of the phospholipid is discussed and how it constitutes the cell membrane.

Professor Bailyn begins the class with a discussion of a recent New York Times article about the discovery of a new, earth-like planet. He then discusses concepts such as epicycles, dark energy and dark matter; imaginary ideas invented to explain 96% of the universe. The Anthropic Principle is introduced and the possibility of the multiverse is addressed. Finally, biological arguments are put forth for how complexity occurs on a cosmological scale. The lecture and course conclude with a discussion on the fine differences between science and philosophy.