U2-L5 Cellular organelles

Question 1

Answer 1

Question 2

endomembrane system

Answer 2

works as a dynamic network (exchange of materials)
1. vesicle formation by budding from a membranous compartment
2. transport of the vesicle through tracks formed by the cytoskeleton
3. fusion with membrane of a different compartment

Question 3

endocytosis and exocytosis pathways coverage in the endomembrane system

Answer 3

flow of proteins, lipids and carbs

Question 4

secretory pathway

Answer 4

= exocytosis
synthesis of materials in the ER –> modification as it passes through the AG –> transport along the cytoplasm with different destinations

Question 5

endoplamis reticulum (ER)

Answer 5

• most of the endomembrane system
• network of sacs and cisterns with a high amount of protein and lipids

Question 6

2 types of endoplasmic reticulum

Answer 6

1. rough ER (RER)
   * with ribosomes attached to the surface
   * protein synthesis, maturation and transport
   * attached to the nucleus
   * the attachment of ribosomes to the surface is temporary
2. smooth ER (SER)
   * without ribosomes on the surface
   * synthesis of lipids

Question 7

destinations of proteins

Answer 7

Inside proteins:
* Nucleus, mitochondria or peroxisomes

Outside proteins:
* Secretion, cell membrane, or degradation (lysosomes)

All protein synthesis initiates on ribosomes that are free in the cytosol
After the first few aa emerge, the ribosome either:
* stay in the cytosol for inside proteins
OR
* is targeted to the RER for outside proteins

A signal sequence emerges from the growing protein to target the ribosome to the RER

Question 8

Post-translational protein modifications

Answer 8

• The proteins synthesized in the RER undergo modifications before reaching their mature state
• Post-translational modifications help proteins acquire their functional form and direct their fate

Question 9

lipid synthesis

Answer 9

the lipid that form the plasma membrane are synthesized in the SER

Question 10

SER functions

Answer 10

1. lipid synthesis
2. unsaturation of fatty acids
3. detoxification
4. muscle contraction

Question 11

golgi apparatus

Answer 11

• formed by flattened cisterns that are grouped forming dictyosomes
  2 faces:
  1. cis face (Close to Er): receiving face
  2. trans face (close to plasma mb): delivering face

Question 12

golgi apparatus function

Answer 12

1. protein maturation - Post translational modifications –> Proteolysis, glycosylation
2. protein sorting and delivery - Proteins are organized and classified to be sent to their final destination

Question 13

lysosomes

Answer 13

• They originate from the golgi apparatus
• Responsible for the intracellular digestion of macromolecules
• Very abundant in macrophages (cells of the immune system that degrade microorganisms)

Question 14

lysosomes classification

Answer 14

1. primary
   * they have not been fused with another vesicle
   * content is released outside the cell
   * bone remodelling
   * breakdown of outer mb of human egg (sperm cell acrosome)
2. secondary
   * fusion of a 1ary lysosome with another vesicle (with intra- or extracellular content)
   types:
   * autophagic lysosome - intracellular content (mitochrondria)
   * heterophagic lysosome - extracellular content (bacteria)

Question 15

perixisomes function

Answer 15

1. oxidation of some toxic substance ex. alcohol –> enzyme oxidase
2. elimination of toxic cellular H202 –> enzyme catalyze