Lecture 9 Flashcards
List the 4 major functions of the Golgi apparatus.
- Processing newly synthesised secretory products
o Proteins
o Glycoproteins
o Mucopolysaccharides (glycosaminoglycans; GAGs) - To act as a centre for redistribution of cell membranes
- The production of primary lysosomes
o Contain hydrolytic enzymes
o Released at trans-face - As a site of carbohydrate synthesis
(Mainly oligosaccharides)
What is the structure of the cytoskeleton?
• An array of fibrous proteins (filaments) • Three families of protein filaments: o Actin filaments o Microtubules o Intermediate filaments
What is the function of the cytoskeleton?
Cytoskeleton systems perform spatial and mechanical functions in living cells
Function of the actin filaments?
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
Function of the microtubules?
Maintain the positions of membrane-enclosed organelles, directs intracellular transport, and form the mitotic spindle during cell division
Function of the intermediate filaments?
Provide mechanical strength
Where does the Golgi apparatus reach it’s greatest size and complexity?
In secretory and storage cells
Is the Golgi apparatus found in all eukaryotic cells? If so, where are they found in them?
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
What does the Golgi apparatus consists of?
An ordered series of curved and parallel compartments, the cisterna or sacs
Associated with the cisternae are small vesicles (20-50nm diameter) that…
- Enter or leave cis-face from/to the ER
- In the trans-face, vesicles containing cargo exit the Golgi Complex
The location of the Golgi apparatus?
- 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
What kinda of protein is required for the positioning of the Golgi apparatus near the cell centre of animal cells?
Motor proteins
What is the function of a lysosome?
- “Suicide bags”
- Powerful digestive enzymes (hydrolytic) that digest pathogens and cellular debris
Where do lysosomes originate from?
The Golgi apparatus
How do lysosomes work?
- 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
Late endosomes?
Secreted by the Golgi Apparatus and contain the enzymatic packages for lysosomes
Endolysosome?
- The product of the fusion of an endosome and a lysosome during endocytosis
- Digestion occurs when a lysosome fuses with another vesicle
What do indigested or indigestible molecules accumulate as?
Residual bodies
The cis face of the Golgi complex is most directly involved in which process?
Accepting vesicles from the ER
The trans face of the Golgi complex is most directly involved in which process?
Releasing vesicles that were originally received from the ER
Endoplasmic reticulum (ER) which is attached to ribosomes is called what?
Golgi apparatus
Which strategy is the most effective for larger cells to have an effective surface area to volume ratio?
Having thin, finger-like projections
What is the main function of the Golgi apparatus?
Packaging of material in membranes for transport out of the cell
Pinocytosis?
- 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
Phagocytosis?
- 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
Two forms of endocytosis?
Phagocytosis and Pinocytosis
Receptor-mediated endocytosis?
- 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.
Tay Sachs?
- Lysosomal storage disease
- Absence of one of the digestive enzymes (hexosaminidase A), resulting in accumulation of component to be digested
