Cytoplasm Lecture

Question 1

Is the cell a bag of cytoplasm?

Answer 1

NO

Question 2

What is the cytoskeleton?

Answer 2

Skeleton + muscle of cells

Protein polymers -> shape + motility of cells

COMPOSED-> microtubules, microfilaments (Actin), intermediate filaments

Question 3

What are microtubules?

Answer 3

Tubulin dimers of alpha-tubulin + beta-tubulin (tubulin is GTPase)

• Hollow w/ diameter of 24 nm
• MAPS (MT associated proteins) stabilize

HIGHLY DYNAMIC

Question 4

What is a polarized polymer? Microtubule

Answer 4

+ and a - end

+ is dynamic (lengthens + shortens)

motor protein reads and moves according to polarity

Question 5

What makes up the mitotic spindle and determines cell shape? Backbone for cilia + flagella?

Answer 5

Microtubules

Question 6

What are microtubules composed of?

Answer 6

13 +/- protofilaments (stacks of tubulin dimers)

Leads to MT DYNAMIC INSTABILITY

Question 7

What are microtubule associated motor proteins? What direction do they move?

Answer 7

Structural non-motor proteins

Dynenin (- end directed)

Kinesin (+ end directed)

Question 8

What is the nucleation center?

Answer 8

The centrosome

Question 9

What is nucleation? Where does it occur?

Answer 9

genesis of cytoskeletal polymer

Nucleation occurs at centrosome

Question 10

What is polymerization

Answer 10

The elongation of cytoskeletal polymer following the initial nucleation

Question 11

What is the centrosome structure?

Answer 11

+ end furthest away
- end closest to the center

Gamma tubulin required for nucleation

Question 12

What are cilia and sperm tails composed of?

Answer 12

Microtubule based structures for movement

Question 13

Where do you find cilia?

Answer 13

Lung epithelium, trachea, fallopian tube

Question 14

What is a basal body?

Answer 14

A microtubule organizing center for cilia and flagella (- end is closest to basal body)

Question 15

What is an axoneme composed of?

Answer 15

9 +2 microtubule of cilia + flagella

MT doublet + dynenin drives axnomenal motility

Question 16

What is immotile cilia syndrome?

Answer 16

Malfunction w/ microtubule

Body wide defect in axonemal structure leading to Obstructive Lung Disease + sterility in males

Question 17

What is Kartagener’s syndrome?

Answer 17

Situs inversus (reversal of normal body symmetry) + immotile cilia

Question 18

What is cancer in regards to microtubules?

Answer 18

disrupt MT dynamics to block cell division

Question 19

What is Lissencephaly?

Answer 19

Mutation in microtubule protein LISI and doublecortin

Question 20

What is Charcot-Marie-Tooth disease type 2A?

Answer 20

Mutation in kinesin (mitofusion2, a protein of mitochondria)

Question 21

What are neurodegenerative disorders?

Answer 21

Abnormalities of tau, dynenin, kinesis, spastin

Question 22

What are microfilaments?

Answer 22

Actin filaments w/ NONhollow polymers of actin

Question 23

What is actin?

Answer 23

microfilaments
ATPase (helical)

Dynamic (rapid assembly + disassembly)
-Regulated by accessory proteins

Substrate for myosin to move and carry

UNLIKE MICROTUBULES, NO SPECIFIC ORGANIZING CENTER LIKE CENTROSOME (nucleate almost anywhere in cell)

Question 24

What is F-Actin?

Answer 24

Helical, bound by accessory proteins

3 isoforms (Alpha, beta, gamma)

Question 25

Where is F-Actin Alpha found? What about beta and gamma?

Answer 25

Alpha -> muscle Beta + gamma -> most cells

Question 26

What are actin filament dynamics?

Answer 26

Polymerization is ATP hydrolysis dependent

Question 27

What end of Actin filament is preferred for polymerization?

Answer 27

BARBED

Question 28

What does nucleation lead to in actin filament?

Answer 28

Polymerization

Question 29

What does ARP2/3 lead to in actin filament nucleation?

Answer 29

branched filaments

Question 30

What does formins + spire lead to in actin filament nucleation?

Answer 30

Bundled linear filaments

Question 31

What are myosin?

Answer 31

F-actin associated force generating mechanoenzymes w/ roles in contractility and intracellular transport? Myosin II -> skeletal muscle?

Question 32

What end does myosin move towards on filaments?

Answer 32

Barbed end

Question 33

What are cytokines?

Answer 33

F-actin and myosin II at contractile ring during cell division

Question 34

What are microvilli?

Answer 34

Actin based epithelial projections

Question 35

Where are microvilli found?

Answer 35

Small intestine, sensory organs (ears -> STEROCILIA)

Question 36

What are cytoskeleton and cell attachment to the ECM?

Answer 36

Physical link between

Question 37

In the erthocyte skeleton, what is the scaffold?

Answer 37

F-actin is scaffold for spectrin web

Question 38

What is hereditary spherocytosis?

Answer 38

Fragile spheres of blood bc spectrin is weak binding

Question 39

What is hereditary elliptocytosis?

Answer 39

Fragile ellipocytes because incomplete form of spectrin

Question 40

What is the actin reason for breast cancer?

Answer 40

Tensins -> intern receptors to actin cytoskeleton (disrupted)

Question 41

What is familial hypertrophic cardiomyopathy?

Answer 41

Mutations in specific cardiac actin (cause of sudden death in athletes)

Question 42

What are mutations in skeletal muscle actin associated with?

Answer 42

Abnormalities of muscle + muscle weakness

Question 43

What does myosin VI mutation cause?

Answer 43

Deafness

Question 44

What does Myosin VII mutation cause?

Answer 44

Deafness, neuro disroder, blindness (usher syndrome type 1)

Question 45

How do pathogens use actin?

Answer 45

Usurp the endogenous machinery to translocate w/i cell

Question 46

What is phalloidin?

Answer 46

Binds to and stabilzies actin filaments | next to a pic of a mushroom named amanita phalloides

Question 47

What are intermediate filaments?

Answer 47

Molecularly related but diverse filaments

Question 48

What is the structure of intermediate filaments?

Answer 48

Non-polarized, NON-DYNAMIC (more stable)

Question 49

What are the functions of intermediate filaments

Answer 49

Space filling, tensile strength IMPORTANT AT CELL JUNCTIONS LESS CONSERVED THAN MICROTUBULES + MICROFILAMENTS USED AS CELL MARKERS

Question 50

What are intermediate filaments type 1/type 2?

Answer 50

Epithelial cells (hair nails) smallest Type 1 acid Type 2 basic

Question 51

What are type 3 intermediate filaments?

Answer 51

vimentin + desmin, glial fibrillary acidic protein (cells of mesenchymal origin -> fibroblasts) muscle + glial

Question 52

What are type IV neurofilament proteins?

Answer 52

Neurons

Question 53

What are type V intermediate filaments?

Answer 53

Nuclear lamina of all nucleated cells

Question 54

What is epidermolysis bullsosa simplex?

Answer 54

Intermediate filament based cellular structure Mutation in keratain- > very sensitive to mechanical injur

Question 55

What is progeria?

Answer 55

Fast aging disease w/ nuclear lamina protein

Question 56

What is the overall structure of cytoskeleton?

Answer 56

Protein polymers Actin-> actin filaments Tubulin -> microtubules Intermediate filaments