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Exercise 9:
Cytoskeletal Structures
Announcements
• Post Lab 11 is due by your next lab.
• LNA Cytoskeletal Structure assigned today, and is due
next lab.
• Next Lab Exam 2 Review (week of April 17).
• Exam 2: Week of April 24. Your exam time for Exam 2
is the same as it was for Exam 1
• Final Exam: Friday, May 5 from 8 – 11 AM
• If you have a conflict with the Final Exam, you must fill
out the Conflict Final Exam Request Form found on the
Course Website by May 3 at 5 PM.
Goals
• Become familiar with the three different
cytoskeletal systems
• Understand the role and structures of the
mitotic spindle during cell division
Cytoskeleton
• Composed of three distinct systems
• (classified by size)
– Microfilaments (actin) - thinnest
– Intermediate filaments (lamin)
– Microtubules (tubulin)- thickest
Microfilaments (Actin)
Microfilaments
• Made up of strands of the protein actin and
often interact with strands of other proteins.
• They change cell shape and drive cellular
motion, including contraction, cytoplasmic
streaming, and the “pinched” shape changes
that occur during cell division.
• Microfilaments and myosin strands together
drive muscle action.
Intermediate Filaments (Lamins)
Intermediate filaments
• Made up of fibrous proteins organized into
tough, ropelike assemblages that stabilize
a cell’s structure and help maintain its
shape.
• Some intermediate filaments help to hold
neighboring cells together (Cell
junctions). Others make up the nuclear
lamina.
Microtubules (Tubulin)
Microtubules
• Long, hollow cylinders made up of many
molecules of the protein tubulin. Tubulin
consists of two subunits, a-tubulin and btubulin.
• Microtubules lengthen or shorten by
adding or subtracting tubulin dimers.
• Microtubule shortening moves
chromosomes.
• Interactions between microtubules drive
the movement of cells.
• Microtubules serve as “tracks” for the
movement of vesicles.
The Exercise
• Part I: Actin and Myosin Filaments
– View prepared slides of smooth, skeletal, and cardiac muscle
– Draw each muscle type and label nucleus, sarcomere, I-disk, A & I
bands
– You may find the Muscle Poster helpful
• Part II: Flagella and Cilia
– Prepare slides
– Observe the locomotion of each organism
– Also available as prepared slides if needed
• Part III: Mitotic Spindle in plant and animal cells
– View prepared slides of whitefish blastula and onion root tip
– Compare/Contrast mitotic spindles found in plant and animal cells
Part I: Muscle Cells
Skeletal: voluntary movement, breathing
Smooth: involuntary, movement of internal organs
Cardiac: beating of heart
Skeletal
Skeletal
Cardiac Muscle
• Each muscle cell contains only one nucleus.
• Adjoining cells interdigitate forming a meshwork
that is resistant to tearing (intercalated disk).
Smooth Muscle
• Long and spindled shaped.
• Each cell has a single nucleus
• Actin and myosin filaments are not
regularly arranged and therefore, do not
produce the striated appearance
Summary of Muscle Types
The Exercise
• Part I: Actin and Myosin Filaments
– View prepared slides of smooth, skeletal, and cardiac muscle
– Draw each muscle type and label nucleus, sarcomere, I-disk, A & I
bands
• Part II: Flagella and Cilia (microtubules)
– Prepare slides with Protoslo
– Observe the locomotion of each organism
– Also available as prepared slides if needed
• Part III: Mitotic Spindle in plant and animal cells
– View prepared slides of whitefish blastula and onion root tip
– Compare/Contrast mitotic spindles found in plant and animal cells
Protozoa Cultures
• Amoeba
• Ciliate
– Stentor
• Flagellate
– Euglena
Amoeba
Cilia
Stentor
Flagella
Euglena
#3
The Exercise
• Part I: Actin and Myosin Filaments
– View prepared slides of smooth, skeletal, and cardiac muscle
– Draw each muscle type and label nucleus, sarcomere, I-disk, A & I
bands
• Part II: Flagella and Cilia
– Prepare slides
– Observe the locomotion of each organism
• Part III: Mitotic Spindle in plant and animal cells
– View prepared slides of whitefish blastula and onion root tip
– Compare/Contrast mitotic spindles found in plant and animal cells
Mitotic Spindle
• Constructed to enable the separation of
the chromatids formed during replication
• Consists of microtubules radiating out from
the two centrosomes
• Centrosome consists of a pair of centrioles
Cell Division
The Mitotic Spindle Consists of
Microtubules