Cellular Movements

Question 1

What is the cytoskeleton?

Answer 1

Network of protein fibers that help maintain the shape of the cell and secures some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable unicellular organisms to move independently.

Question 2

three types of fibers within the cytoskeleton

Answer 2

1. microfilaments
2. intermediate filaments
3. microtubules.

Question 3

Define actin

Answer 3

A globular structural protein that polymerizes in a helical fashion to form an actin filament (or microfilament)

Question 4

Define myosin

Answer 4

a large family of motor proteins found in eukaryotic tissues, allowing mobility in muscles

Question 5

Filamentous means what?

Answer 5

Having the form of threads or filaments.

Question 6

What is responsible for transport along microtubules? [2]

Answer 6

Microtubules provide long tracks along which a broad range of organelles and vesicles are transported by kinesin and dynein motors. Motor protein complexes also tether cargoes to cytoskeletal filaments, helping facilitate their interaction and communication.

Question 7

Discuss the microtubule’s structures.

Answer 7

A microtubule is a polar structure, its polarity arising from the head-to-tail arrangement of the α- and β-tubulin dimers in a protofilament. Because all protofilaments in a microtubule have the same orientation, one end of a microtubule is ringed by α-tubulin, while the opposite end is ringed by β-tubulin.

Question 8

What are cilia and flagella?

Answer 8

Cilia and flagella are hair-like structures that assist with locomotion in some cells, as well as line various structures to trap particles

Question 9

What are motor proteins and where are they found and what do they interact with?

Answer 9

Motor proteins are molecular motors that use ATP hydrolysis to move along cytoskeletal filaments within the cell. They fulfill many functions within biological systems, including controlling the sliding of filaments in muscle contraction and mediating intracellular transport along biopolymer filament tracks.

Question 10

Microfilaments, What are they?

Answer 10

Microfilaments, which are the thinnest part of the cytoskeleton, are used to give shape to the cell and support all of its internal parts.

Question 11

Describe the structure and function of microfilaments.

Answer 11

• Microfilaments assist with cell movement and are made of a protein called “actin” which works with another protein called “myosin” to produce muscle movements, cell division and cytoplasmic streaming.
• Microfilaments keep organelles in place within the cell. Microfilaments have a diameter of about 7 nm, and are made of two intertwined strands of a globular protein called actin. For this reason, microfilaments are also known as actin filaments.

Question 12

Fun fact on actin and myosin.

Answer 12

Actin and myosin are plentiful in muscle cells. When your actin and myosin filaments slide past each other, your muscles contract.

Question 13

Microfilaments can disassemble, why?

Answer 13

They can depolymerize (disassemble) and reform quickly, thus enabling a cell to change its shape and move. White blood cells (your body’s infection-fighting cells) make good use of this ability. They can move to the site of an infection and engulf the pathogen.

Question 14

Describe the roles of microtubules as part of the cell’s cytoskeleton.

Answer 14

are part of the cell’s cytoskeleton, helping the cell resist compression, move vesicles, and separate chromosomes at mitosis.

Question 15

How would you describe the structures of cilia and flagella?

Answer 15

: a “9+2 array,” meaning that a ring of nine microtubules is surrounding two microtubules.

Question 16

Microtubules important function

Answer 16

Microtubules attach to replicated chromosomes during cell division and pull them apart to opposite ends of the pole, allowing the cell to divide with a complete set of chromosomes in each daughter cell.

Question 17

Define microtubule

Answer 17

they are small hollow tubes made of protein and found in cells; part of the cytoskeleton.

Question 18

Define flagellum:

Answer 18

a flagellum is a lash-like appendage that protrudes from the cell body of certain prokaryotic and eukaryotic cells.

Question 19

More on cytoskeleton:

Answer 19

A cellular structure like a skeleton, contained within the cytoplasm.

Question 20

Describe the structure of microtubules.

Answer 20

• Microtubules are the largest element of the cytoskeleton.
• The walls of the microtubule are made of polymerized dimers of α-tubulin and β-tubulin, two globular proteins.
• Like microfilaments, microtubules can dissolve and reform quickly.
• Microtubules are hollow, with walls consisting of 13 polymerized dimers of α-tubulin and β-tubulin. They are also the structural elements of flagella, cilia, and centrioles.

Question 21

Intermediate Filaments.

Answer 21

• cytoskeletal components found in animal cells.
• Intermediate filaments contribute to cellular structural elements and are often crucial in holding together tissues like skin.
• Intermediate filaments have an average diameter of 10 nanometers.

Question 22

Flagella and Cilia

Answer 22

• Flagella are long, hair-like structures that extend from the plasma membrane and are used to move an entire cell (for example, sperm, Euglena). When present, the cell has just one flagellum or a few flagella.
• When cilia are present, however, many of them extend along the entire surface of the plasma membrane. Cilia are short, hair-like structures that are used to move entire cells (such as paramecia) or move substances along the outer surface of the cell (for example, the cilia of cells lining the Fallopian tubes that move the ovum toward the uterus, or cilia lining the cells of the respiratory tract that trap particulate matter [dust] and move it toward your nostrils.

Question 23

Flagella and Cilia share a common structural arrangement of microtubules called

Answer 23

“9 + 2 array.” —- a single flagellum or cilium is made of a ring of nine microtubule doublets surrounding a single microtubule doublet in the center.

Question 24

What are the two main systems in cellular movements:

Answer 24

1) specialized motor proteins & microtubules

2) actin microfilaments and myosin motor molecules.

Question 25

Intracellular Microtubule-based movement. Kinesins and dyneins

Answer 25

• Kinesins and dyneins are motor proteins that couple ATP hydrolysis to walk along the microtubules.

Question 26

Kinesins

Answer 26

• Kinesins move by hydrolyzing ATP to move forward and releases the nucleotide to release then move. Most move towards the plus end of the microtubules. Kinesins are biological motor proteins that are ATP-dependent and function to assist cells with the transport of molecules along microtubules. Simply put, these proteins, function as highways within cells as they allow for the transport of all sorts of cellular cargo. They play pivotal roles in mitosis (i.e. cell division) and in the trafficking of vesicles and organelles within the cell. FXNS: vesicle and organelle transport.during cell division for the assembly of
• spindles, separation of centrosomes and attachment of chromosomes to spindles.

Question 27

Dyneins/dynactin

Answer 27

complexes link to cargo vesicles and move towards the minus end of microtubules. Taken together, the endomembrane system moves on microtubules and motor proteins.

Question 28

Microtubule-based motility

Answer 28

• Cilia and flagella are driven by microtubules. Flagellum have a core axoneme and depend on protofilaments and dynein for movement (and linked by nexin).

Question 29

Actin-based cell movement

Answer 29

• The Myosins act as actin-based motor proteins.
• Skeletal muscle cells are made up of thick and thin filaments and are arranged into sarcomeres.
• Sarcomeres are made up as structural proteins and support proteins.

Question 30

Filament-based movement in muscles. Muscle contraction is a four-step cycle:

Answer 30

1) myosin binds loosely to actin filament;
2) the power stroke, a trigger of the conformational change associated with move of thick versus thin filament
3) binding of ATP leads to change in myosin and weaking of bond to actin (no ATP leads to rigor or stiffness).
4) ATP hydrolysis returns myosin to high energy state, ready for the next round of movement.

Question 31

actin-based motility in non-muscle cells

Answer 31

Actin microfilaments (MFs) drive cell migration through cycles of protrusion, attachment, 
translocation and detachment.