Non-membranous Organelles

Question 0

Cytoskeleton function

Answer 0

Determines the shape of the cell

Plays an important role in the movements of organelles and cytoplasmic vesicles

Allows the movement of entire cells

Question 1

Cytoskeleton structure

Answer 1

Microfilaments (actin filaments)
Intermediate filaments
Microtubules

Question 2

Microfilaments (structure)

Answer 2

Made of thin twisted strands of protein molecules that lie parallel to the long axis of the cell.

Composed of actin, a contractile protein.

Question 3

Microfilaments (function)

Answer 3

They play a role in moving or shifting cytoplasmic components

Question 4

Actin filaments (function)

Answer 4

Cause contractile movements of cells and cell membrane stabilization

Question 5

Actin filaments (properties)

Answer 5

Actin filaments are present in all type of cells

Found in microvili

They are found in skeletal muscle cells where they form a stable arrangement of bundles with another type of filamentous protein, myosin
Contraction occurs when actin and myosin filaments slide relatively to one another

Question 6

Cell cortex (structure)

Answer 6

Beneath the plasma membrane, actin, in association with various proteins, forms a layer: the cell cortex

Question 7

Cell cortex (function)

Answer 7

Provides mechanical support to the cell membrane

Allows changes in cell shape (as in endocytosis and exocytosis)

Question 8

Intermediate filaments (structure)

Answer 8

They are intermediate in size between microfilaments and microtubules

Question 9

Intermediate filaments (function)

Answer 9

Play a supporting or general structural role

Question 10

Intermediate filaments (classes)

Answer 10

Six major classes on the basis of protein composition and cellular distribution:

Cytokeratin (in epithelial cells)
Vimentin (in mesenchymal cells)
Desmin (in muscle cells)
Neurofilaments (in neurones)
Gilal filaments (in gilal cells)
Lamin (form a structural layer on the inner side of the nuclear membrane)

Question 11

Cytokeratin or Keratin

Answer 11

Accumulate in the differentiation process called keratinization to form an outer layer of non-living skin cells that reduces deshydration and provides some protection (nails, feathers, beaks, horns…)

Question 12

Microtubules (structure)

Answer 12

Consists of protein called tubulin, which polimerize to form a hollow tubule

Question 13

Microtubules (function)

Answer 13

Involved in intracellular transport and cell motility

Question 14

Microtubules (properties)

Answer 14

Found in cytoplasmic processes, cilia and flagella, which are motile processes, covered by cell membrane with highly organized microtubule core

Question 15

Flagella

Answer 15

Longer than cilia
Moves the cell itself in wave-like fashion
Usually one per cell
Example: sperm cell

Question 16

Cilia

Answer 16

Shorter than flagella, appendages projecting from cell surface
Capable of movement, moves material over the cell surface
Many per cell
Example: cilia in respiratory system

Question 17

Microvilli (structure)

Answer 17

Extension of plasma membrane

Contains actin filaments

Question 18

Microvilli (function)

Answer 18

Increases the cell surface area for absorption

Question 19

Microvilli (properties)

Answer 19

Usually found in line intestine
Normally many on each cell
Doesn’t move

Question 20

Ribosomes (structure)

Answer 20

RNA rich cytoplasmic granules, in addition of approximately 80 different proteins

Question 21

Ribosomes (function)

Answer 21

Fixed ribosomes bound to rough endoplasmic reticulum are the site of protein synthesis
Free ribosomes scattered in cytoplasm act as reserve

Question 22

Centrioles (structure)

Answer 22

Small cylindrical-shaped structures found just outside and near the nucleus

Question 23

Centrioles (function)

Answer 23

Production of microtubules that help moving chromosomes during cell division

Question 24

Proteasomes (structure)

Answer 24

Abundant cytoplasmic protein complexes mot associated with membrane

Question 25

Proteasomes (function)

Answer 25

Remove proteins no longer needed by the cell

Provide important mechanism for restricting activity of a specific protein to a certain window of time

Question 26

Lysosomes vs Proteasomes comparison

Answer 26

Whereas lysosomes digest bulk material introduced into the cells, or whole organelles and vesicles, proteasomes deal primarily with proteins as individual molecules

Question 27

Failure of proteasomes

Answer 27

Failure of proteasomes or other aspects of a cell’s protein quality control can allow large aggregates of protein to accumulate in affected cells
Example: Alzheimer’s disease

Question 28

Inclusions (function)

Answer 28

Cytoplasmic inclusions have little or no metabolic activity but serve as storage material

Question 29

Inclusions (classes)

Answer 29

Lipids
Glycogen
Proteins