L2: Non-Membranous organelles & cell inclusion

Question 1

what are ribosomes?

Answer 1

They are non-membranous organelles that are responsible for protein synthesis.

Question 2

How are ribosomes seen under LM?

Answer 2

spherical small particles and they are basophilic as they contain phosphate groups in the RNA.

Question 3

How are Ribosomes seen under EM?

Answer 3

electron-dense granules of a diameter of 20-30 nm which consists of two subunits, each one consists of protein associated with rRNA.

Question 4

what is the function of ribosomes?

Answer 4

synthesis of protein.

Question 5

what are the types of ribosomes?

Answer 5

free ribosomes: responsible for protein synthesis within the cell for its usage.

attached ribosomes; Responsible for protein synthesis that are segregated in rER and transported to the outside of the cell.

Question 6

what are cytoplasmic fibres?

Answer 6

non-membranous organelles in the form of thread-like structures.

Question 7

what are the types of cytoplasmic filaments?

Answer 7

thin
thick
intermediate

Question 8

thin cytoplasmic filaments

Answer 8

Structure  Actin

Diameter  6-7 nm

Contractility  Contractile

Distribution & function  Microvilli for their movement.

 In cleavage furrow during cell division.

 In muscles for contraction.

Question 9

thick cytoplasmic filaments

Answer 9

Structure  Myosin

Diameter  Variable(12-16nm)

Contractility  Contractile

Distribution & function  In muscle associated with actin filaments

Question 10

Intermediate cytoplasmic filaments

Answer 10

Structure  5 types

Diameter  10-12nm

Contractility  Non-Contractile

Distribution&function

 In muscles (desmin), nerve cells (neurofilaments), and epithelial cells (cytokeratin).

 Support and maintain the shape of the cell.

 Important for identification of tumors.

 can be used as cell type specific markers for different types of tumors.

Question 11

What are microtubules?

Answer 11

They are non-membranous organelles in a pipe-like structure.

Question 12

what is the structure of microtubules?

Answer 12

tubulin protein

Question 13

what is the distribution and function of microtubules?

Answer 13

All over the cytoplasm and it is used in many functions like
 Components of the cytoskeleton which support, maintain, and stabilize the shape of the cell.

 They act as guiding tracks for transporting vesicles and organelles.

 Mitotic spindle formation.

 The main structural component of cilia, flagella and
centriole

Question 14

what is the length and diameter of microtubules?

Answer 14

25 nm in diameter but variable in length.

Question 15

How do cytotoxic drugs work?

Answer 15

They prevent the formation of new microtubules so they lead to the stoppage of mitosis and consequently the growth of cancer cells.

Question 16

what are centrioles?

Answer 16

They are non-membranous organelles that are responsible for cell division.

Question 17

how are centrioles seen under LM?

Answer 17

-they are seen as dark blue stained granules by iron hematoxylin.

Question 18

what is the site of centioles?

Answer 18

in non-dividing cells, it is present as a pair of centrioles in a juxtanuclear position associated with Golgi bodies.

Question 19

how are centrioles seen under EM?

Answer 19

• Each centriole is a short cylinder. (Perp. To each other)

-The wall of the cylinder is composed of 27 microtubules longitudinally arranged in 9 (nine) bundles.

-Each bundle consists of three micro-tubules (triplets) which are surrounded by fibrillar electron dense material.

Question 20

what are the functions of centrioles?

Answer 20

• Play an important role in cell division.

-In non-dividing cells, it serves as a center about which other cell organelles are polarized.

• Its location plays a key role in the three-dimensional organization of the cell as it regulates the location of the nucleus and different organelles.
• In ciliated cells, act as basal bodies of the cilia.

Question 21

what is cilia?

Answer 21

-they are Hair like processes projecting from the free surface of certain epithelial cells.

Question 22

what is the site of cilia?

Answer 22

-Respiratory system; trachea and bronchioles.
-Female genital system; uterus and fallopian tube.

Question 23

How are cilia seen under LM?

Answer 23

• Could be seen vaguely on the surface of the cell facing the lumen or cavity.

Question 24

what is the length and number of cilia?

Answer 24

10-15 micrometer - several hundred per cell

Question 25

How are cilia seen under EM?

Answer 25

Consists of:
1) The shaft: formed of microtubules (2 central singlets + 9 peripheral doublets)
2) The basal body: made of modified centriole.
3) The rootlets.

Question 26

what is the function of cilia?

Answer 26

Cilia are beating rhythmically in one direction to move a thin film of fluid or mucous which is present on the surface of the cell.

Question 27

what are flagella?

Answer 27

cytoplasmic processes like in the tail of sperm.

Question 28

What is the structure of flagella?

Answer 28

same as centrioles

Question 29

how many flagella per cell?

Answer 29

1

Question 30

how long is a flagellum?

Answer 30

Much longer than cilia 200 um

Question 31

How does a flagellum move?

Answer 31

Have whip-like swimming Movement

Question 32

Immotile cilia syndrome

Answer 32

❖ abnormality in proteins of the cilia and flagella.

❖ characterized by chronic respiratory infections caused by the lack of the cleansing action of cilia in the respiratory tract and male infertility due to immotile spermatozoa.

Question 33

How is cell coat seen under EM?

Answer 33

-It is seen as moderate electron dense fuzzy coat over the surface of microvilli of the cells.

Question 34

What is microvilli?

Answer 34

-Finger-like processes projecting from the surface of cells and contain actin filaments.

Question 35

Polyribosome

Answer 35

Electron dense granules are attached together by thin electron dense filament of mRNA forming whorls figures on the outer surface of rER.

Question 36

What kind of electron microscopes are used to examine cilia and microvilli?

Answer 36

SEM

Question 37

Difference between cilia and microvilli

Answer 37

Cilia; of large size and projecting on the free border of some cells. Microvilli; smaller in size and projecting on the free border of other cell.

-The microvilli are smaller in diameter and have a core of electron dense microfilaments.

Question 38

Light band

Answer 38

Actin

Question 39

Dark band

Answer 39

Actin and myosin

Question 40

H-zone

Answer 40

Myosin

Question 41

What is cell inclusion?

Answer 41

-It is non-living material in the cytoplasm.

Question 42

What does cell inclusion include?

Answer 42

-Stored food
-Pigments
-Crystals

Question 43

What is stored food as cell inclusion?

Answer 43

Carbohydrates and lipids.

Question 44

How are carbohydrates stored as cell inclusion?

Answer 44

In the form of glycogen granules.

Question 45

Where are carbohydrates stored?

Answer 45

In liver and muscles.

Question 46

How are lipids stored as cell inclusion?

Answer 46

As small droplets in liver cells and large globules in connective tissue fat cells.

Question 47

What are pigments?

Answer 47

They are colored substances that can be seen without staining

Question 48

What are types of pigments?

Answer 48

-Exogenous and Endogenous

Question 49

What are examples of exogenous pigments?

Answer 49

1) Lipochrome pigments: e.g. carotene.

2) Dust: -Small dust particles are continuously inhaled and enter the respiratory system.

-They are phagocytosed by
macrophages in the lung and cause
black pigmentation.

3) Minerals.

4) Tattoo marks.

Question 50

What are examples of endogenous pigments?

Answer 50

1) Hemoglobin.

2) Hemoglobin derivatives e.g. bilirubin.

3) Melanin.

4) Lipofuscin pigment: (golden brown):
- Present in cardiac muscle fibers, nerve cells and hepatocytes.

• Considered as wear and tear pigment or as residual bodies that are not hydrolyzed by lysosomal enzymes.

-They increase with age