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BIOL 436 > Cell Biology of Neurons (4/5) > Flashcards

Cell Biology of Neurons (4/5) Flashcards

1
Q

What key features are important for neuron function?

A
  1. Electrical excitability 2. Polarization
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2
Q

What are the two compartments of the neuron?

A

The somatic dendritic compartment consists of the dendrites and cell body. The axonal comparment consists of initial axonal segment (hillock) and axon.

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3
Q

What are the two compartments of the epithelial cell?

A

The baso-lateral compartment. Faces more cells. The apical compartment consists of tight junction and microvilli. Faces lumen.

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4
Q

What are the stages of development of neurites

A
  1. Lamellipodia 2. Immature neurites 3. Axon formation 4. Dendrite formation 5. Further maturation
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5
Q

During neuronal migration, what do the neurons use to migrate along the radial cell?

A

Leading process

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6
Q

What does the leading process develop into?

A

Dendrites

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7
Q

What does the trailing process develop into?

A

Axon

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8
Q

How is neuronal polarity established and maintained?

A
  1. Selective delivery of protein 2. Selective fusion of membrane 3. Selective retention of protein
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9
Q

What proteins are selectively delivered to dendrites?

A

Neurotransmitter receptors

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10
Q

What proteins are selectively delivered to axons?

A

Voltage-gated Na/K channels

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11
Q

What proteins mediate vesicle fusion with the plasma membrane?

A

SNARE proteins

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12
Q

What restricts unwanted mixing between proteins of the axon and dendrite?

A

Diffusion barrier at axon initial segment

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13
Q

How is neuronal polarity maintained when neuron is young?

A

A lot can move around early. 1. lateral diffusion 2. endocytosis 3. retention in lipid rafts

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14
Q

How is neuronal polarity maintained when neuron is older?

A

Membrane protein-cytoskeletal interactions at axon hillock prevent lateral mixing of membrane proteins between axons and dendrites

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15
Q

Describe organelles in axons vs dendrites

A

Axons do not have all organelles. Dendrites have most

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16
Q

Describe protein difference in axons vs dendrites

A

Axons have tau protein; dendrites have MAP2 (microtubule associated proteins)

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17
Q

What are general cellular components of a neuron?

A

Plasma membrane, cytosol, cytoskeleton

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18
Q

What are microtubules?

A

Part of cytoskeleton; They are tubes of 13 protofilaments made from alpha, beta dimers (50 kD each)

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19
Q

What is beta tubulin?

A

Subunit in MT; GTP or GDP Binding; plus end

20
Q

What is alpha tubulin?

A

Subunit in MT; GTP binding; minus end

21
Q

What influences growth of microtubules.

A

When rate of subunit addition exceeds rate of GTP hydrolysis it leads to a growing microtubule
When rate of GTP hydrolysis exceeds rate of subunit addition it leads to a shrinking microtubule

22
Q

What is the function of microtubules in neurons?

A

Functions for axonal growth and guidance. Provides tracks for long-range protein and organelle transport between the neuronal cell body and the nerve terminal.

23
Q

What molecular motors mediates organelle transport between the neuronal cell body and the nerve terminal?

A

Kinesin motors: mediate either plus or minus end-oriented transport. Dynein motors: mediate only minus end-oriented transport

24
Q

Describe microtubule polarity in axons

A

all MT plus ends are oriented towards terminal

25
Q

Describe microtubule polarity in dendrites

A

mixed MT polarity in higher organisms

26
Q

What is F-actin and its structure?

A

Part of cytoskeleton; this conserved and abundant protein is made from two parallel protofilaments which is made from a globular monomer

27
Q

What is the filament polarity of F-actin?

A

plus end is the growing end

28
Q

What determines the rate of assembly of F-actin

A

Free monomer concentration and actin-associated protein determine the rate of assembly. Only when ATP bound. If ADP bound they will dissassemble

29
Q

What are neurofilaments and structure?

A

third type of cytoskeleton; this ropelike filament is made of eight tetramers

30
Q

What is neurofilament function?

A

This abundant fibrillar component provides strength in axons

31
Q

T/F: Some genetic information is stored in the mitochondria

A

True

32
Q

Where does transcription and RNA processing occur?

A

The nucleus

33
Q

T/F: Proteins are only made in the cell body and dendrites

A

False: there is evidence for protein synthesis in axon and nerve endings

34
Q

Cytosolic proteins are translated on free ____________; secretory and membrane proteins are synthesized by _____________

A
  1. ribosomes 2. Rough ER
35
Q

The classical ER retention signal is the C-terminal ______ sequence

A

KDEL

36
Q

What are the co- and post-translational modifications?

A
  1. Glycosylation (N-linked or O-linked) 2. Phosphorylation/Dephosphorylation 3. N-acetylation 4. Isoprenylation 5. Ubiquitination
37
Q

Why glycosylation?

A

Affects molecular recognition

38
Q

Why phosphorylation?

A

Signaling molecules that affect protein function

39
Q

Why N-acetylation?

A

Affects protein binding affinity to membrane

40
Q

Why isoprenylaton?

A

Affect membrane association like N-acetylation

41
Q

Why isoprenylaton?

A

Affect membrane association like N-acetylation

42
Q

Why ubiquitination?

A

Causes protein to be degraded

43
Q

What are the two major functions of the Golgi complex

A
  1. Modifications of proteins 2. Sorting and targeting of proteins into different vesicles
44
Q

What is the purpose of endocytosis?

A
  1. Recycling of synaptic vesicles
  2. Keeping the neuron surface area at the same size
  3. Regulating the amount of membrane proteins or receptors
45
Q

What mediates endocytosis?

A

Clathrin.

46
Q

What experimental approaches led to the discovery of axonal transport?

A
  1. Paul Weiss (1948) tied off sciatica nerve and observed accumulation of axoplasm proximal to the ligature
  2. Radioactive labeling of neuronal proteins
  3. Video enhanced differential interference contrast (DIC) light microscopy
  4. Fluorescent labeling techniques combined with photobleaching and photoactivation
47
Q

Why do the axon, terminals, and growth cone produce proteins?

A

To have rapid local responses to changes in the environment of the cell

BIOL 436 (33 decks)

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