Lab 7: Flagellar Regeneration in Euglena Sp.

Question 1

long hollow protein tubules made of tubulin dimers are called ____

Answer 1

microtubules

Question 2

a microtubule consists of 13 _____

Answer 2

protofilaments

Question 3

what are protofilaments made of?

Answer 3

alpha beta tubulin dimers, which alternate along the filament.

Question 4

microtubules and each protofilament has a positive and negative end, which end is the end of protofilament growth?

Answer 4

the protofilament extends from the positive end.

Question 5

roles of microtubules

Answer 5

plays important roles in the cytoskeleton, helps form centrioles and cilia and flagella

Question 6

structure of a flagella

Answer 6

consists of 9 doublets (9x2) microtubules, and another doublet in the middle of the ring. also has associated MAPs. Flagella are extensions from the cell and grow from the addition of tubulin dimers to the distal end of the flagellum (tail end)

Question 7

How do flagella grow?

Answer 7

Flagella are extensions from the cell and grow from the addition of tubulin dimers to the distal end of the flagellum (tail end)

Question 8

The _____ end of the flagellum is anchored in to the cytoplasm of the cell via the ______ (type of MTOC)

Answer 8

The PROXIMAL end of the flagellum is anchored in to the cytoplasm of the cell via the BASAL BODY (type of MTOC)

Question 9

How are tubulin polymers (protofilaments) connected to each other

Answer 9

via non covalent interactions of the protofilaments

Question 10

regeneration of flagella occurs via _____

Answer 10

non-covalent polymerization of microtubules

Question 11

Effects of colchicine on flagellar growth

Answer 11

immediate decrease in regrowth compared to control-deflagellated Euglena. However, the regrowth is recoverable to normal levels after time passes.

Question 12

Mechanism for colchicine and how it prevents flagellar growth

Answer 12

colchicine imediately inhibits microtubule polymerization by binding to free tubulin in cytosol, therefore, there is no tubulin available for re-polymerization

colchicine inhibitory mechanism is temporary however, as Euglena would begin to produce more tubulin that is not bound to the colchicine, and the new tubulin can help form the flagella.

recap : colchicine immediately but temporarily affects flagellar re-growth

Question 13

Effects of cyclohexamide on flagellar regrowth

Answer 13

late onset but Permanent effect. Flagella will never grwo back to original lengths.

Question 14

Mechanism as to how cyclohexamide impacts flagellar regrowth

Answer 14

interferes with translation process in protein synthesis, preventing any tubulin from being formed. Intereferes with flagellar formation on a genetic level.

Question 15

Why do you not seen the affects of cyclohexamide immediately on flagellar regrowth?

Answer 15

effects are not seen early on because there is extra free cytosolic tubulin that flagella can be formed from. After the cytosolic tubulin is used, flagellar regeneration is halted because tubulin cannot be made.

Question 16

Would would happen to a deflagellated Euglena if you treated it with both Colchicine and Cyclohexamide?

Answer 16

would see and immediate and permanent decrease in flagellar length

• immediate decrease due to colchicine and how it binds to cytosolic tubulin
• permanent due to cyclohexamide preventing the translational process of tubulin protein formation on a genetic level, preventing any more tubulin from being synthesized.