Lecture Materials

Unit V: Biochemistry of Complex Systems

Lecture 9 - Membrane Channels & Pumps

With this lecture we begin a unit a that looks at proteins as complex machines. We will look first at the intrinsic membrane proteins that are responsible for moving material across membranes. Those that require a source of free energy to carry out the transport are called active transport systems. Some of these are directly coupled to the hydrolysis of ATP, while others are coupled to a second concentration gradient that flows across the cell in a favorable direction. We will also look at gated passive transport systems, which, while requiring no external source of free energy, are far from from being just simple channels.

Lecture 10 - Signal Transduction Pathways and Sensory Systems

Here we look at the movement of a signal from the outside of a cell to its inside, where it elicits changes within the cell. These changes are usually mediated by protein kinases, which phosphorylate enzymes to turn them on or off. We will focus on three examples; the β-adrenergic receptor, which is involvesd in the “flight or fight response, the insulin receptor, which is involved in regulating blood glucose levels, and the epidermal growth factor (EGF) receptor, which triggers cell growth in response to injury. Each example presents common themes such as secondary messengers, the amplification of a signal, and the activation of protein kinases. These signal pathways also provide examples of how multiple proteins can work together in complex ways to produce a concerted result. After learning about signal transduction pathways, we then consider how they are put to use in a way that allows us to sense the world around us.

Lecture 11 - Molecular Motors

For living cells, location means everything. In multicellular organisms location determines what a cell does and how it interacts with its neighbors. Many organisms, both multicellular and unicellular, must also be able to move in order to locate foods sources and to avoid dangerous situations. Location is also important at the intracellular level, where the cellular components must be able to locate themselves where they are needed for the cell to function properly. In this section we will examine the molecular motors that are used to move the components within a cell as well as whole organisms. There are many common themes for these molecular motors, such as movement along tracks, including actin filaments and microtubules, and the use of nucleotide triphosphates to both influence the polymerization of these tracks and to fuel the movement along them. We will also look at the bacterial flagella, which looks and functions remarkably like an electrical motor, but which derives its free energy not from the hydrolysis of nucleotides, but from and ion gradient across the cell membrane.

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