regulation of animal cell shape

Question 1

What’s inside the cell in terms of an animal cell?

Answer 1

cytoskeleton
- it supports and helps with mobility
- can attach cells to the extracellular matrix and to each other by using cell junctions

Question 2

What’s outside the cell in terms of an animal cell?

Answer 2

there is an extracellular matrix of glycoprotein

Question 3

what is the cytoskeleton and what are its functions?

Answer 3

• helps maintain cell shape and position of organelles within cells.
• the cytoskeleton rapidly disassembles and reassembles (unlike the body’s skeletal system).
• this ability allows rapid changes in cell shape
• the cytoskeleton are highly dynamic but still provides stability

Question 4

what is the cytoskeleton made of?

Answer 4

The Cytoskeleton is made of three main components:
- microtubules - tube shaped
- microfilaments - thin rope shaped
- intermediate filaments - coil shaped

Question 5

what are the microtubules?

Answer 5

• Microtubules are composed of tubulin subunits.
• They may radiate out from an organizing center (centrosome).
• Microtubules resist compression & help maintain cell shape

Question 6

what provides cell motility? what motion do flagella and cilia have?

Answer 6

Microtubules can also provide cell motility.
Flagella: “snake-like” motion
Cilia: “rowing-like” motion

Question 7

how do microtubules work?

Answer 7

• Microtubules are also involved in organelle motility within the cell
• ATP-powered motor proteins can “walk” organelles along microtubules
• Allows vesicles, or other organelles, to be transported to specific targets within the cell

Question 8

what are microfilaments?

Answer 8

• Microfilaments are a double chain of actin subunits
• Microfilaments resist tension
• The cortical network under the plasma membrane helps make this region less fluid and thus maintains cell shape

Question 9

how do microfilaments form?

Answer 9

Microfilaments form:
- linear strands
- and 3-dimensional networks (using branching proteins)

Question 10

what supports cell movement?

Answer 10

• Interactions between actin and motor proteins such as myosin support cell movement
• Actin-myosin interactions allow muscle contraction

Question 11

what are intermediate filaments made up of?

Answer 11

Are made of various proteins including:
- keratins in hair.
- lamins in the nucleus.
- neurofilaments in neurons

Question 12

what are intermediate filaments formed by?

Answer 12

Intermediate Filaments form relatively permanent cellular structures

Question 13

what are the functions of intermediate filaments?

Answer 13

• Intermediate filaments help:
  § Maintain cell shape.
  § Anchor organelles.
• They may also remain after the cell that made them has died, as in your hair and outer layer of skin

Question 14

which one of the three cytoskeleton components resists tension the most/is the least dynamic?

Answer 14

intermediate filament because of its coil-like shape

Question 15

How Are Cells Joined Together?

Answer 15

through cell junctions

Question 16

what are the three major types of cell junctions?

Answer 16

Three major types of Cell Junctions:
- Tight Junctions
- Desmosomes
- Gap Junctions
- Each differs in structure and function.

Question 17

what are tight junctions?

Answer 17

• Hold neighboring cells tightly pressed together
• May form a continuous seal
• Prevents movement of fluid across cell layers

Question 18

what are desmosomes?

Answer 18

• Anchoring junction
• Provide attachments between sheets of cells e.g. muscle
• Act like rivets (a “torn muscle” is a torn desmosome)
• Connected into the cell by intermediate filaments

Question 19

what are gap junctions?

Answer 19

• A point of cytoplasmic contact between two cells
• ions and small molecules can pass from cell to cell
• Allows rapid cell to cell (intercellular) communication

Question 20

How Are Cells Joined Together?

Answer 20

by the extracellular matrix

Question 21

what lies within an ECM?

Answer 21

• Cells lie within an Extracellular Matrix (ECM) the composition of which varies between tissues

Question 22

what is ECM composed of?

Answer 22

composed of material secreted by cells

Question 23

how does the secretion of cells in ECM happen?

Answer 23

secretion occurs by constitutive exocytosis

Question 24

what are most ECM? and what is the most abundant ECM gylcoprotein?

Answer 24

• Most ECM proteins are glycoproteins (proteins with added carbohydrates)
• The most abundant ECM glycoprotein is collagen

Question 25

what are the collagen fibers embedded in?

Answer 25

• The collagen fibers are embedded in a proteoglycan complex matrix
• Collagen fibers have a great tensile strength

Question 26

what is Proteoglycans?

Answer 26

• Proteoglycans are proteins with extensive sugar additions.
• Proteoglycans trap water within the ECM

Question 27

how does proteoglycan help resist compression?

Answer 27

• Proteoglycans trap water within the ECM
• Water resists compression and thus helps retains tissue shape

Question 28

what is the cytoskeleton and what are its functions?

Answer 28

• helps maintain cell shape and position of organelles within cells.
• the cytoskeleton rapidly disassembles and reassembles (unlike the body’s skeletal system).
• this ability allows rapid changes in cell shape
• the cytoskeleton is highly dynamic but still provides stability

Question 29

what does microtubules, microfilaments and intermediate filaments resist?

Answer 29

microtubules = compression
microfilaments & intermediate filaments = tension