Bio 21 Cell Biology
List of Terms and Study Guide 5
For MiniExam 3, 9 April 2001

Protein Sorting

protein sorting

post-translational modifications

cleavage

glycosylation

phosphorylation

sorting signals

nuclear envelope

nuclear pores

traffic through pores (active transport vs diffusion)

signal sequence

NLS (nuclear localization signal)

nuclear import receptor

nuclear pore fibrils

GTP hydrolysis

 

protein translocators

mitochondria and chloroplasts

protein unfolding

receptor

translocator complex

signal sequence cleaved

chaperone

resorting within mitochondria

 

endoplasmic reticulum

lumen

membrane

ER signal sequence

rough ER

membrane-bound ribosomes vs free ribosomes

signal recognition particle

SRP receptor

protein translocation channel

start and stop transfer signal sequences

single-pass vs multi-pass transmembrane proteins

 

Membrane transport: Carrier proteins

 

simple diffusion

cations (inside vs outside cell)

anions

carrier proteins

channel proteins

passive transport (facilitated diffusion)

active transport

electrochemical gradient

concentration gradient

membrane potential

Na+ gradient

H+ gradient

transport of glucose

coupled transporters

symport

antiport

uniport

Na+-K+ pump or Na+-K+ ATPase

 

Ion Channels and Membrane potential

 

ion selectivity

gated channels

voltage-gated

ligand-gated

stress-activated

neurons (nerve cells)

dendrite

cell body

axon

nerve terminal

voltage-gated Na+ channels

voltage-gated K+ channels

resting potential

depolarization

hyperpolarization

threshold

action potential (nerve impulse)

self-amplifying

millisecond

(Na+ channels) closed --> open --> inactivated --> closed

voltage-gated Ca++ channels

electrical signal --> chemical signal

target cell

synapse

presynaptic vs postsynaptic cell

synaptic cleft

neurotransmitter

synaptic vesicles

transmitter-gated channels

chemical signal --> electrical signal

neuromuscular junction

acetylcholine receptor

excitatory vs inhibitory neurons/inputs

 

 

G-protein and Enzyme-linked Receptors

 

signal transduction

hormonal

paracrine

juxtacrine

neuronal

local mediators

contact-dependent signaling

receptor protein

competence

hydrophobic signals

steroid hormones

thyroid hormone

intracellular receptors

 

hydrophilic signals

peptide hormones

cell-surface receptors

ion-channel-linked receptors

G-protein-linked receptors

enzyme-linked receptors

signaling cascades

target proteins

secondary messengers

 

seven-pass transmembrane receptor proteins

G-protein

binary switch

a subunit

GTP

GTP hydrolysis

ßg complex

adenylate cyclase

cyclic AMP (cAMP)

cyclic-AMP-dependent protein kinases (A-kinase)

serine/threonine kinase

gene regulatory protein (transcription factor)

phospholipase C

PIP2

IP3 (inositol triphosphate)

diacylglycerol (DAG)

protein kinase C

Ca++

endoplasmic reticulum

calmodulin

CaM-kinases

photoreceptor

rhodopsin

transducin

 

amplification

allosteric modulation

protein phosphorylation

 

enzyme-linked receptor

growth factor receptor

receptor tyrosine kinase

dimerization

Ras

Ras-activating protein

kinases I, II, and III (MAP kinases)

oncogene

proto-oncogene

 

 

LEARNING OBJECTIVES:

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.