Bio 21 Cell Biology
List of Terms and Study Guide 5
For MiniExam 3, 9 April 2001
traffic through pores (active transport vs diffusion)
NLS (nuclear localization signal)
nuclear import receptor
nuclear pore fibrils
mitochondria and chloroplasts
signal sequence cleaved
resorting within mitochondria
ER signal sequence
membrane-bound ribosomes vs free ribosomes
signal recognition particle
protein translocation channel
start and stop transfer signal sequences
single-pass vs multi-pass transmembrane proteins
Membrane transport: Carrier proteins
cations (inside vs outside cell)
passive transport (facilitated diffusion)
transport of glucose
Na+-K+ pump or Na+-K+ ATPase
Ion Channels and Membrane potential
neurons (nerve cells)
voltage-gated Na+ channels
voltage-gated K+ channels
action potential (nerve impulse)
(Na+ channels) closed --> open --> inactivated --> closed
voltage-gated Ca++ channels
electrical signal --> chemical signal
presynaptic vs postsynaptic cell
chemical signal --> electrical signal
excitatory vs inhibitory neurons/inputs
G-protein and Enzyme-linked Receptors
seven-pass transmembrane receptor proteins
cyclic AMP (cAMP)
cyclic-AMP-dependent protein kinases (A-kinase)
gene regulatory protein (transcription factor)
IP3 (inositol triphosphate)
protein kinase C
growth factor receptor
receptor tyrosine kinase
kinases I, II, and III (MAP kinases)
1. Be able to describe the various ways in which proteins can be sorted. Know the different mechanisms by which proteins leave the cytosol and enter (1) the nucleus, (2) the mitochondria, and (3) the ER. How do signal sequences mediate this process? What kinds of experiments would reveal the role and identity (amino acid sequence) of the sorting signals? What would happen to a protein if a sorting signal was mutated?
2. Be able to compare and contrast carrier proteins and ion channels in terms of structure and function. Know how levels of ions outside the cell contrast with those inside the living cell. Know how these concentration gradients are maintained by the cell and how the cell utilizes these gradients to do useful work, such as active transport and signal transduction.
3. Be able to describe the process of neuronal signalling in a typical vertebrate neuron, from receiving the initial stimulus, through propagation along the axon, to what happens when the signal reaches the nerve terminal. How is the signal transmitted from the presynaptic cell to a post-synaptic cell? Understand how an action potential is generated.
4. Know how cellular communication ligands are classified (e.g. hormone, paracrine, juxtacrine, neuronal).
5. Know the major differences in mechanism of action for lipophilic/hydrophobic and hydrophilic signal ligands. Know where the receptors are located and how they transduce the signal.
6. Know the 3 classes of membrane-bound receptor and be able to give an example of each.
7. Understand the following statements well enough to explain them and give a real (or hypothetical) example:
a. Receptors are specific for their ligands.
b. Any given receptor can have different effects in different cells.
c. Each cell contains receptors for many different ligands, and the responses may synergize or interfere with one another.
d. Each receptor-signal transduction system often produces a set of cellular responses, rather than a single response.
e. On the other hand, often a single cell will integrate information from different signals to produce an "all or none" response.
8. Understand the basic structure of G-proteins in their inactivated and activated states. Understand how they become activated and inactivated.
9. Be able to recognize each of the steps of the cAMP and IP3 second messenger systems. Know how each component is turned on and off. Know which interactions represent allosteric modulation and which represent phosphorylation. Which steps are capable of amplifying the signal and which are not? Explain.
10. Know how protein kinase A, protein kinase C, and CAM-kinase are activated. In what ways do these kinases play a centrally important role in their signaling pathways?
11. Understand the mechanism of action of enzyme-linked receptors. Why are they called "enzyme-linked"? How are they turned on and off?
12. What kinds of cellular functions are most frequently facilitated by enzyme-linked receptors?
13. Be able to explain the role of Ras in normal and cancerous cells.