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KCUMB Molecular Biology > EXAM II Theisen > Flashcards

EXAM II Theisen Flashcards

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1
Q

What percentage of the genome is encoded in our DNA?

A

Around 1.5%

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2
Q

Mitochondria undergo fusion and fission depending on environmental conditions. Which protein is important during fission, which results in two separate mito?

A

Dynamin-1

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3
Q

Why are there a lot of diseases associated with mitochondria?

A

Mito contain no DNA repair mechanisms, which results from tRNA problems which is involved with translation

Mito holds a tRNA genes

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4
Q

What are the 2 major types of responses that occur from signal transduction (cell signaling)? Which one involves proteins, which one involves gene transcription?

A

Fast Response = change in activity or function of enzymes or proteins, i.e cAMP

Slow Response = change in protein amount or gene expression

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5
Q

What are the 3 types of cell signaling receptors that are located within the plasma membrane?

A

Ion-channel coupled receptors (common in nervous tissue)

GPCRs - 7-pass transmembrane proteins

Enzyme-coupled receptors - i.e. tyrosine kinase

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6
Q

T/F Heterotrimeric (alpha,beta,gamma) G-proteins have intrinsic catalytic activity

A

False; NO intrinsic catalytic activity

3 components of receptor; EC domain, TM domain, cytosol domain (associates w/ G proteins)

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7
Q

Cholera toxin modifies G protein, causing increasing cAMP activity, which subunit of the G protein does cholera modify?

A

Keeps G-alpha in the GTP active form indefinitely

Leads to 100-fold increase in cAMP

PKA phosphorylates the CFTR Cl- channel = water secretion

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8
Q

Define desensitization of a signal

A

The ability to turn off or reject a signal (important for cancer)

Potentiate = to turn up
Attenuate = to turn down
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9
Q

What is the role of G-protein receptor kinase in signal desensitization?

A

GRKs phosphorylate the receptor such that another protein (i.e. arrestin) will bind to the 3rd intracellular loop of GPCR preventing G-alpha from interacting with the third loop

The result is that the G-alpha-GDP does not get converted to G-alpha-GTP

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10
Q

Which receptor creates docking sites for other proteins?

a. GPCR
b. Enzyme coupled receptors (i.e. tyrosine kinase)
c. Ion-channel coupled receptors
d. all of the above

A

Enzyme-coupled receptors (tyrosine kinase)

JAK-STAT Receptors
Serine/Threonine kinases, etc.

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11
Q

Where is the enzymatic domain of enzyme-coupled receptor tyrosine kinase? What are other features of this receptor?

A

Cytoplasmic tail of the integral membrane protein

Single pass transmembrane domain

Ligand binding induces dimerization of two receptor monomers

Autophosphorylation = recruits SH2 DOMAIN of Grb2 = binds phosphotyrosine

Important for growth factors

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12
Q

What are some basic functions of the cytoskeleton?

A

Changes cell shape
Moves the cell
Supports plasma membrane
Muscle cell contraction

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13
Q

List the 3 types of cytoskeleton proteins

A

Microtubules

Actin filaments

Intermediate filaments

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14
Q

Function of microtubules

A

Determines the positions of membrane-enclosed organelles and direct intracellular transport

Makes up centrioles and mitotic spindle

Cilia and flagella

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15
Q

Function of actin filaments

A

Determines the shape of cell’s surface; whole-cell locomotion, secretion, endocytosis

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16
Q

Function of intermediate filament

A

Mechanical strength

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17
Q

Cytoskeletal filaments undergo a lag phase, growth phase, and equilibrium (steady state) phase. What is required in order for it remain in the steady phase?

A

Critical concentration (Cc) - the rate of addition of new subunits balances the rate of dissociation

18
Q

Tubulin is a heterodimer containing alpha and beta-tubulin, what do they have binding sites for?

What binding sites are locating in the actin monomers?

A

GTP; the GTP in alpha-tubulin is never hydrolyzed

Longitudinal contact = alpha-beta
Lateral contact = alpha-alpha, beta-beta

Actin monomers = ATP binding sites; arranged head to tail (flexible, easily bent)

19
Q

What is the rate limiting step in the formation of the cytoskeleton?

A

Nucleation (via gamma-tubulin)

20
Q

ARP proteins, which are accessory proteins of actin filaments contains Arp2/3 complex, what allows them to bypass the rate-limiting step of filament nucleation?

A

When the complex binds to the activating factor which induces a conformational change; repeated rounds of branching can occur creating a highly branched web of actin filaments

Works similar to gamma-TuRC = nucleation at (-) end

21
Q

While ARP2/3 complex creates branched actin filaments, formins create what type of pattern?

A

Straight/unbranched actin filaments

Dimeric proteins; binds (+) end (OPPOSITE from gamma-TuRC)

22
Q

How is there a large pool of actin polymers always kept available when all the nucleation of actin filaments occurring in the cell? Which accessory protein is important here?

A

Thymosin - keeps actin monomers soluble so that they are readily available for generating filaments

When monomers are bound to thymosin, they can’t associate with actin filaments

23
Q

Define catastrophe of stability, which proteins are involved

A

Change from growth to rapid shrinkage

Kinesin-13

XMAP215

24
Q

Alpha-actinin vs. Fimbrin (cross-linking proteins)

A

alpha-actinin = cross-linkage, loose bundles, allowing myosin II to enter; contractile

Fimbrin = cross-linkage into tight bundles, excluding myosin II; parallel bundles

25
Q

List the 3 plasma membrane protrusions

A

FLiP - dense core of actin filaments, no organelles

  1. Filopodia - via migrating fibroblasts
  2. Lamellipodia - via epithelial cells, fibroblasts, neurons
  3. Pseudopodia - via ameobae & neutrophils
26
Q

What are the 3 distinctive activities that occur during cell crawling? PAR

A
  1. Polarization & protrusion - actin rich structures pushed out at front of cell
  2. Adhesion and traction - adhere to ECM or adjacent cells via TM receptors
  3. Retraction - adhesion disassembly at rear
27
Q

What are the two main ways to connect animal cells and to provide the strength to connect?

A

Connective Tissue

Epithelial Tissue

28
Q

List the 4 types of cell-cell junctions

A
  1. Anchoring - adherins (actin), desmosomes & hemidesmosomes (intermediate)
  2. Occluding - tight junctions
  3. Channel-forming - gap junctions
  4. Signal relating
29
Q

State 3 features of tight junctions

A
  1. Forms a seal/barrier between cells
  2. Forms a fence between membrane domains - limits lateral diffusion of lipids/proteins b/w apical/basolateral domains
  3. Recruits cytoskeleton and signaling molecules at the cytoplasmic side
30
Q

What are the 3 polarity proteins involved in the polarization process of the epithelial cells?

A

Eating a Par Sandwich

  1. Par
  2. Scribbles - cytoplasmic
  3. Crumbs - apical membrane determinant
31
Q

What are the two main classes of extracellular macromolecules that the lamina consists of?

A
  1. GAGs

2. Fibrous protein

32
Q

What are the 4 common glycoproteins that laminin contains?

A
  1. Type IV collagen
  2. Laminin - primary organizer of the sheet structure; creates heterophilic contacts for diff proteins
  3. Nidogen
  4. Perlecan
33
Q

Define focal adhesion = integrins!!!!!!

A

Prominent and durable actin-linked cell-matrix adhesions (integrins!!!!!!!!) formed when fibroblasts have sufficient time to form the strong attachment to the rigid surface

Common in hemidesmosomes w/ keratin filaments attached in intracellular domain

Defects = blistering

34
Q

What structures interact in focal contacts?

A

ECM

Integrins

Cell cytoskeleton

35
Q

What protein is prominent in focal adhesions?

A

FAK = focal adhesion kinase = cytoplasmic protein tyrosine kinase, recruited by talin/paxillin = MAXIMAL ACTIVATION = PHOSPHYLATION VIA SRC

Related to Src and docking sites for Src-family kinases = helps regulate cell division, growth, survival

36
Q

What cell type makes/secretes the ECM that’s located in the ECM?

A

Fibroblasts!!!!!!

37
Q

Basic collagen structure, which amino acids make it up?

A

Triple-stranded helical structure - 3 polypeptide chains

Proline and glycine

38
Q

What is the importance of hydroxyl groups in fibroblasts?

A

Create affinity = strong binding between fibers

39
Q

Importance of prolyl/lsyl hydroxylases in collagen?

A

Provides strong binding b/w Hydrogen fibers = allows superhelix to remain tightly bound

40
Q

List the 3 morphologies of common cell lines and describe their shapes

A
  1. Fibroblastic cells - bipolar/multipolar w/ elongated shapes, grow attached to a substrate
  2. Epithelial-like cell - polygonal, grows attached to a substrate in discrete patches
  3. Lymphoblast-like cells - spherical, usually grown in suspension w/out attaching to a surface
41
Q

List advantages and disadvantages of cultured cells lines

A

Advantages = no use of animals, good reproducibility b/w experiments, control of environment, can expose cultures to reagents

Disadvantages = costly, must dev standardized techniques, time to learn aseptic technique, limited quantity, dedifferentiation & selection can occur and many original cellular mech can be lost

KCUMB Molecular Biology (6 decks)

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