Lecture 9

Question 1

List the 4 major functions of the Golgi apparatus.

Answer 1

1. Processing newly synthesised secretory products
   o Proteins
   o Glycoproteins
   o Mucopolysaccharides (glycosaminoglycans; GAGs)
2. To act as a centre for redistribution of cell membranes
3. The production of primary lysosomes
   o Contain hydrolytic enzymes
   o Released at trans-face
4. As a site of carbohydrate synthesis
   (Mainly oligosaccharides)

Question 2

What is the structure of the cytoskeleton?

Answer 2

• An array of fibrous proteins (filaments)
• Three families of protein filaments:
o Actin filaments
o Microtubules
o Intermediate filaments

Question 3

What is the function of the cytoskeleton?

Answer 3

Cytoskeleton systems perform spatial and mechanical functions in living cells

Question 4

Function of the actin filaments?

Answer 4

Determine the shape of the cell’s surface and are necessary for whole-cell locomotion; they also drive the division of one cell into two

Question 5

Function of the microtubules?

Answer 5

Maintain the positions of membrane-enclosed organelles, directs intracellular transport, and form the mitotic spindle during cell division

Question 6

Function of the intermediate filaments?

Answer 6

Provide mechanical strength

Question 7

Where does the Golgi apparatus reach it’s greatest size and complexity?

Answer 7

In secretory and storage cells

Question 8

Is the Golgi apparatus found in all eukaryotic cells? If so, where are they found in them?

Answer 8

Yes.

• In animal cells it is found near the nucleus in an area called the centrosome
• In plant cells there are many Golgi bodies dispersed through the cytoplasm, where they are called dictyosomes

Question 9

What does the Golgi apparatus consists of?

Answer 9

An ordered series of curved and parallel compartments, the cisterna or sacs

Question 10

Associated with the cisternae are small vesicles (20-50nm diameter) that…

Answer 10

• Enter or leave cis-face from/to the ER

- In the trans-face, vesicles containing cargo exit the Golgi Complex

Question 11

The location of the Golgi apparatus?

Answer 11

• Usually located between the ER and the plasma membrane
• The face that is closest to the ER is known as the cis face
• The trans face lies at the plasma membrane side

Question 12

What kinda of protein is required for the positioning of the Golgi apparatus near the cell centre of animal cells?

Answer 12

Motor proteins

Question 13

What is the function of a lysosome?

Answer 13

• “Suicide bags”

- Powerful digestive enzymes (hydrolytic) that digest pathogens and cellular debris

Question 14

Where do lysosomes originate from?

Answer 14

The Golgi apparatus

Question 15

How do lysosomes work?

Answer 15

• They are vesicles with TEM imaging compartments that separate powerful digestive enzymes from the rest of the cell
• Multiple pathways deliver materials to lysosomes
• After a lysosome takes in material to be digested, it changes it’s shape

Question 16

Late endosomes?

Answer 16

Secreted by the Golgi Apparatus and contain the enzymatic packages for lysosomes

Question 17

Endolysosome?

Answer 17

• The product of the fusion of an endosome and a lysosome during endocytosis
• Digestion occurs when a lysosome fuses with another vesicle

Question 18

What do indigested or indigestible molecules accumulate as?

Answer 18

Residual bodies

Question 19

The cis face of the Golgi complex is most directly involved in which process?

Answer 19

Accepting vesicles from the ER

Question 20

The trans face of the Golgi complex is most directly involved in which process?

Answer 20

Releasing vesicles that were originally received from the ER

Question 21

Endoplasmic reticulum (ER) which is attached to ribosomes is called what?

Answer 21

Golgi apparatus

Question 22

Which strategy is the most effective for larger cells to have an effective surface area to volume ratio?

Answer 22

Having thin, finger-like projections

Question 23

What is the main function of the Golgi apparatus?

Answer 23

Packaging of material in membranes for transport out of the cell

Question 24

Pinocytosis?

Answer 24

• Cell drinking
• Fluid molecules bind to receptors on the plasma membrane, and the membrane that selectively engulfs it completely pinch off and go into the cell as a vesicle

Question 25

Phagocytosis?

Answer 25

• Cell eating
• Molecules bind to receptors on the plasma membrane, and the membrane that selectively engulfs it completely pinch off and go into the cell as a food vacuole

Question 26

Two forms of endocytosis?

Answer 26

Phagocytosis and Pinocytosis

Question 27

Receptor-mediated endocytosis?

Answer 27

• The specified molecule binds to a receptor on the plasma membrane
• The molecule-bound receptor migrates along the membrane to a region containing a clatherine-coated pit (Clathrin is a protein)
• After molecule-receptor complexes accumulate in the clatherine-coated pit, the pit region forms an invagination that is internalised by endocytosis
• A clatherine-coated vesicle is formed, which encapsulates the ligand-receptor complex and extracellular fluid.
• The clatherine-coated vesicle fuses with an endosome in the cytoplasm and the clatherine coating is removed.
• The receptor can be enclosed in a lipid membrane and recycled back to the plasma membrane.
• If not recycled, the specified molecule remains in the endosome and the endosome fuses with a lysosome.
• Lysosomal enzymes degrade the specified molecule and deliver the desired contents to the cytoplasm.

Question 28

Tay Sachs?

Answer 28

• Lysosomal storage disease

- Absence of one of the digestive enzymes (hexosaminidase A), resulting in accumulation of component to be digested