Exam #1: Cell Biology VI

Question 1

MAPs

Answer 1

Microtubule Associated Proteins

Question 2

MAP-T (Tau)

Answer 2

• Forms crosslinks between microtubules
• In Alzheimer’s Disease, hyperphosphorylated, leading to aggregation
• Histological “flame” appearance
• Eosinophilic

Question 3

Neurofibrillary Tangles

Answer 3

• Caused by Tau aggregates

- Will cause cell death, but remain as “ghost cells, or tombstones”

Question 4

Microfilaments

Answer 4

• Comprised of subunits of actin (have positive & negative end)
• Stained with Phallacidin conjugated with a green fluorescein dye

Question 5

Where do actin microfilaments grow & disassemble?

Answer 5

• Grow= positive end

- Disassemble= negative end

Question 6

Where are microfilaments found?

Answer 6

1) Microvilli
2) Cell Cortex
3) Adherens belt
4) Filopodia
5) Lamellipodium
6) Stress Fibers
7) Contractile Ring

Question 7

What drug inhibits actin polymerization?

Answer 7

Cytochalasins

Question 8

Thick Filaments

Answer 8

• Myosin subunits
• Darker staining band in striated muscle
• Interact with light staining band (thin filaments)

Question 9

What pathology does a mutation in myosin give rise to?

Answer 9

Cardiomyopathy

Question 10

What are the six differe types of Intermediate Filaments?

Answer 10

1) Cytokeratins
2) Desmin
3) GFAP
4) Neurofilament protein
5) Nuclear Lamin
6) Vimentin

Question 11

Cytokeratin

Answer 11

• Epithelial Tissue

- Glandular organs (liver & pancreas)

Question 12

Desmin

Answer 12

Muscle (smooth & striated)

Question 13

GFAP

Answer 13

• Glial Fibrillary Acidic Protein
• Astrocytic Glial Cells
• DO NOT cross link like neurofilaments

Question 14

Neurofilament Protein

Answer 14

• Neurons

- Cross-linking imparts great tensile strength

Question 15

Nuclear Lamin

Answer 15

Nucleus of all cells

Question 16

Vimentin

Answer 16

• Mesodermal Tissue
• Chondroblasts
• Fibroblasts

Question 17

What can you tell about a tumor by its intermediate filament composition?

Answer 17

Origin

Question 18

What do you know if a tumor expressed two different types of intermediate filaments?

Answer 18

The tumor is de-differentiating, which is an indication of a more aggressive type of tumor.

Question 19

Mallory Bodies

Answer 19

• Hallmark of alcoholic liver disease

- Caused by aggregation of cytokeratins in the liver

Question 20

Epidermoylsis Bullosa Simplex

Answer 20

• Mutations of cytokeratin fiber 14
• Separation of the epidermis where it connects to the dermis
• Causes severe skin blistering & sloughing of skin

Question 21

Rosenthal’s Fibers

Answer 21

• Aggregates of GFAP
• Seen in astrocytomas
• V. long & thick flame- like projection

Question 22

Centrosome

Answer 22

• MTOC (Mirotubule-organizing-center)

- Cytoplasmic region near nucleus containing two centrioles oriented perpendicularly

Question 23

Centriole

Answer 23

Comprised of microtubules in a 9 x 3 arrangement i.e. 9 triplet sets of microtubules

Question 24

How is nuclear appearance useful in diagnosis?

Answer 24

• Cancer
• Well differentiated tumor cells are less aggressive/ better prognosis
• Poorly differentiated tumor cells are more aggressive/ poorer prognosis

Question 25

Nucleolus

Answer 25

Site of ribosome synthesis & assembly

Question 26

Cajal Body

Answer 26

Contain molecular machinery involved in splicing pre-mRNA into mRNA

Question 27

PML Body

Answer 27

- Promylocytic Leukemia Body | - Function in DNA repair & apoptosis

Question 28

Nuclear Envelope

Answer 28

- Formed by two lipid bilayers, outer & inner - Space between is the perinuclear space - Contains protein complexes that form nuclear pores

Question 29

Outer Nuclear Membrane

Answer 29

- Typically continuous with the rER | - Ribosomes are often attached

Question 30

What can readily cross the nuclear pore complex?

Answer 30

Small molecular weight molecules

Question 31

What are nuclear lamins?

Answer 31

- Type of intermediate filament - Important in cell division - Form the nuclear lamina lattice

Question 32

Nuclear Import

Answer 32

- Protein w/ nuclear localization signal - Binds nuclear import receptor - Recognize the nuclear pore complex - Imported in - Energy dependent, GTP

Question 33

What is transported into the nucleus?

Answer 33

- Proteins to assemble ribosomal subunits

Question 34

What is exported from the nucleus?

Answer 34

- Ribosomal subunits

Question 35

Progeria

Answer 35

- Premature aging | - Caused by defect in nuclear lamins

Question 36

What is the role of lamins during mitosis?

Answer 36

- Prophase= phosphorylate lamins for disassembly of the nuclear envelope - Late Telophase= fuse/ reassemble nuclear envelope nuclear envelope fragments by dephosphorylating lamins

Question 37

Euchromatin

Answer 37

- Loosely coiled chromatin - Charge density is less packed - Basic - Less intense basophilic staining - Indication of how active the nucleus is i.e. Euchromatin is very actively transcribing

Question 38

Heterochromatin

Answer 38

- Tightly coiled chromatin - Charge density is tightly packed together - Basic - Causes very dense basic staining

Question 39

Chromatin

Answer 39

- DNA wrapped around histone proteins | - "Beads on a string"

Question 40

Barr Body

Answer 40

- "Drum-stick" that comes off the nucleus | - Indication of female cells

Question 41

Would you expect to see a nucleolus in a heterchromatic nucleus?

Answer 41

No, it would be very difficult to distinguish between them b/c both are going to stain very strongly

Question 42

Orphan Annie Eye Nuclei

Answer 42

- Hallmark histological sign of papillary thyroid cancer | - Nuclei appear empty