Session 1: Cell Ultrastructure

Question 1

What is histology?

Answer 1

The study of tissues

Question 2

What is histopathology?

Answer 2

The study of diseased tissues

Question 3

What are the four fundamental tissue types?

Answer 3

1. Epithelial
2. Muscle
3. Nervous
4. Connective

Question 4

What are tissues?

Answer 4

Functional arrangement of cells

Question 5

What is the importance of the cell membrane?

Answer 5

Compartmentalisation

Question 6

What does the nucleus contain?

Answer 6

Genomic DNA and nucleolus

Site of m-RNA transcription

Question 7

What surrounds the nucleus?

Answer 7

Double-membrane nuclear envelope which is continuous with the RER and supported by intermediate filaments.

Question 8

What is the function of the nucleolus?

Answer 8

Site of ribosomal RNA (r-RNA) synthesis

Initial assembly of ribosome occurs here

Question 9

What is the Rough Endoplasmic Reticulum (RER) associated with?

Answer 9

Ribosomes

Question 10

What is the site of protein synthesis in the cytoplasm?

Answer 10

Rough Endoplasmic Reticulum (RER)

Question 11

Where can an abundance of RER be found?

Answer 11

In biosynthetic cells (e.g., pancreatic acinar cells - exocrine cells)

Question 12

How does RER stain with basic dyes?

Answer 12

Basophilic RER stains strongly with basic dyes such as haematoxylin

Question 13

What are ribosomes?

Answer 13

Electron-dense particles (20-30 nm in diameter) composed of r-RNA and ~75 different proteins

Question 14

What is the diameter of ribosomes?

Answer 14

20-30nm

Question 15

What are ribosomes made up of?

Answer 15

rRNA and proteins (~75 types)

Question 16

What is the difference between free polyribosomes and membrane-bound ribosomes?

Answer 16

Polysomes synthesize proteins destined to remain inside the cell; membrane-bound ribosomes synthesize proteins to be secreted out of the cell.

Question 17

What is the Smooth Endoplasmic Reticulum (SER) associated with?

Answer 17

Not associated with ribosomes (smooth appearance)

Question 18

What is the site of lipid, phospholipid, and steroid synthesis?

Answer 18

Smooth Endoplasmic Reticulum (SER)

Question 19

Where can an abundance of SER be found?

Answer 19

Liver and mammary gland for lipid biosynthesis; ovary, testis, adrenal gland for steroidogenesis; muscle for calcium ion storage.

Question 20

What is the name of the structure in the endoplasmic reticulum that creates a continuous intracellular compartment?

Answer 20

Cisternae (sacs)

Question 21

What is the Golgi Apparatus?

Answer 21

Stack of membranes that modifies, sorts, and packages proteins from the endoplasmic reticulum (ER)

Question 22

What are the three functional compartments of the Golgi apparatus?

Answer 22

1) Nuclear-facing cis face
2) The central medial Golgi
3) The trans Golgi network

Question 23

What are the five main types of vesicles found in a cell?

Answer 23

1) Cell surface-derived endocytic vesicles
2) Golgi-derived transport/secretory vesicles
3) ER-derived transport vesicles
4) Lysosomes
5) Peroxisomes

Question 24

What are lysosomes?

Answer 24

Organelles containing digestive enzymes called acid hydrolases

Question 25

What adaptations make lysosomes efficient?

Answer 25

1) Protons actively pumped across membrane to maintain acidic pH 2) Highly glycosylated membrane proteins to protect from hydrolytic enzymes

Question 26

What is the function of lysosomes?

Answer 26

Break down non-functioning organelles/cellular components and recycle digested products

Question 27

Describe the process of autophagy.

Answer 27

1) **Organelle engulfed by SER** to form autophagosome 2) **Autophagosome fuses with lysosome** to form **phagolysosome** 3) **Acid hydrolases breakdown the organelle** and recycle products

Question 28

What are residual bodies?

Answer 28

Remnants of phagolysosomes containing indigestible material in the cell

Question 29

What can defects in hydrolytic enzymes in lysosomes lead to?

Answer 29

Lysosomal storage disorders (LSDs)

Question 30

Name two lysosomal storage disorders (LSDs).

Answer 30

1) Hurler syndrome 2) Tay-Sachs disease

Question 31

What is Hurler syndrome?

Answer 31

Lysosomal storage disorder with **accumulation of dermatan sulphate** in **lysosomes**

Question 32

What is Tay-Sachs disease?

Answer 32

Lysosomal storage disorder due to lack of **β-hexosaminidase-A enzyme** leading to an **accumalation of GM2-Ganglioside** in nerve cells

Question 33

What are peroxisomes?

Answer 33

Small spherical membrane-bound organelles containing oxidase enzymes

Question 34

Where can abundant peroxisomes be found?

Answer 34

Liver and kidney cells

Question 35

What do peroxisomes detoxify?

Answer 35

Ethanol, phenols, formic acid, formaldehyde

Question 36

What disorder is caused by **impaired β-oxidation of fatty acids** within peroxisomes?

Answer 36

**Adrenoleukodystrophy** A little defect in peroxisomes A - Adreno L -Leuko D - Dystrophy

Question 37

What are mitochondria?

Answer 37

Double-membraned organelles measuring 0.5-2 µm, site of ATP synthesis

Question 38

What disorder is caused by s**pecific mutations in mitochondrial DNA**?

Answer 38

**Kearns-Sayre syndrome** Keep slaying sister

Question 39

What types of cells have abundant mitochondria?

Answer 39

Cells with high energy requirements such as cardiac muscle and sperm flagellum

Question 40

What is the cytoskeleton made up of?

Answer 40

1) Microtubules 2) Microfilaments 3) Intermediate filaments

Question 41

What are microtubules made of?

Answer 41

Tubulin

Question 42

What is the diameter of microtubules?

Answer 42

25nm

Question 43

What are microfilaments made of?

Answer 43

Actin

Question 44

What is the diameter of microfilaments?

Answer 44

5nm

Question 45

What are intermediate filaments made of?

Answer 45

Various proteins e.g., keratin

Question 46

What is the diameter of intermediate filaments?

Answer 46

10nm

Question 47

What are microfilaments?

Answer 47

Fine, threadlike actin-based proteins found in the cell's cytoskeleton

Question 48

What is filamentous actin (F-actin)?

Answer 48

Twisted strand composed of two rows of globular G-actin molecules to form a double helix

Question 49

What is the special arrangement of microtubules in a cilium or flagellum?

Answer 49

9+2 arrangement

Question 50

What do microtubules associate with for movement of cilia and flagella?

Answer 50

Motor proteins

Question 51

What are some functions of microtubules?

Answer 51

- Mitotic spindle apparatus - Allow synaptic vesicles to move along axons - Form 'tracks' for organelle movement

Question 52

What are the names of the motor proteins that associate with microtubules?

Answer 52

- Kinesin - Dynein

Question 53

What are intermediate filaments?

Answer 53

Threadlike proteins in the cell's cytoskeleton that provide structural support

Question 54

What are examples of intermediate filaments?

Answer 54

Epithelial cells = keratin; Mesenchymal cells = vimentin; Muscle cells = desmin

Question 55

What do mutations in basal keratin genes cause?

Answer 55

Skin blistering due to loss of cohesion between basal epithelial cells and the basement membrane

Question 56

At which anatomical sites might you expect cells to contain an abundance of SER? Enterocytes of the gut [...] Mammary gland [...] Ovaries [...] Skeletal muscle [...] Adrenal cortex [...] Testis [...] Islets of Langerhans of the pancreas [...] Thyroid gland [...] Liver [...] Kidney tubules [...]

Answer 56

Enterocytes of the gut No Mammary gland Yes Ovaries Yes Skeletal muscle Yes Adrenal cortex Yes Testis Yes Islets of Langerhans of the pancreas No Thyroid gland No Liver Yes Kidney tubules No

Question 57

Identify the features in the diagram showing Golgi body profiles in an islet cell of the pancreas.

Answer 57

A) A Golgi body's cis face B) A Golgi body's trans face C) A vesicle budding from the trans face of a Golgi body D) A mitochondrion

Question 58

What are the roughly spherical inclusions common in adipocytes and steroidogenic cells? a. Lipid droplets b. Endosomes c. Secretory vesicles d. Lysosomes e. Peroxisomes

Answer 58

a. Lipid droplets

Question 59

Identify the features in the TEM image of RER in a plasma cell.

Answer 59

A) The intracisternal space of the RER B) A nuclear pore C) The double membrane of the nuclear envelope

Question 60

Identify the features in the TEM image of a nucleus.

Answer 60

A) Nuclear envelope B) Nucleolus C) Rough Endoplasmic Reticulum E) Euchromatin F) Mitochondrion G) Heterochromatin

Question 61

What cytoskeletal component allows the movement of pseudopodia in macrophages?

Answer 61

b) Microfilaments

Question 62

Identify the features in the TEM image of RER in a plasma cell.

Answer 62

A. The intracisternal space of the RER B. A nuclear pore C. The double membrane of the nuclear envelope