Lecture 21 - Endocytosis, Autophagy, Cytoskeleton

Question 1

Two-layered coat consists of

Answer 1

Clathrin, AP complex, AP/Clathrin

Question 1

describe Clathrin (2 pts)

Answer 1

• coat protein (outer layer)
• Vesicle formation &
  structure

Question 2

AP complex =

Answer 2

Clathrin Adaptor Protein complex (inner layer)
- 3 different AP complexes
- Select cargo
- Different complexes
associated with different
trafficking routes

Question 3

describe AP/Clathrin

Answer 3

coated vesicles move from TGN to other compartments (e.g.,
lysosomes, endosomes,
plant vacuoles)

Question 4

AP/Clathrin-coated vesicles form

Answer 4

endocytic vesicle to
move material from plasma membrane / extracellular
environment into cell (e.g.,
to endosomes and lysosomes

Question 5

Lysosomes, Function: what is Autophagy?

Answer 5

Normal disassembly of unnecessary or
dysfunctional cellular components—organelle turnover.

Question 6

in Autophagy, Isolation membrane derived from ER engulf target organelles to form what

Answer 6

an autophagosome (also known as autophagic vesicle)

Question 7

in Autophagy, Lysosome fuses with ER-derived autophagic vesicle to form

Answer 7

an autolysosome

Question 8

Content of autolysosome is enzymatically…

Answer 8

digested and released

Question 9

Lysosome function: explain degradation of internalized material

Answer 9

Recycling of plasma membrane components like receptors and
extracellular material

Question 10

Degradation of internalized material Destroys pathogens like…

Answer 10

bacteria and viruses but only in phagocytic cells

Question 11

Pathogen (e.g., bacteria) is
internalized by a specialized cell
called what

Answer 11

phagocytic cell.

Question 12

The pathogen is degraded by lysosomes that associate with what vesicle

Answer 12

pathogen-containing vesicle

Question 13

Hydrolytic enzymes inside
lysosomes degrade and kill the pathogen. What is released outside the cell?

Answer 13

debris

Question 14

Bacteria produce ________ for which neutrophils (white blood cells) have receptors. This allows the neutrophils to move in the direction of the _______ ________

Answer 14

chemoattractants, target bacteria

Question 15

what are Vacuoles

Answer 15

fluid-filled, membrane-
bound. They can take up ~90% of the cell’s volume

Question 16

Vacuoles are involved in the regulation of _________ _____, sequestration of toxic ions, regulation of cell turgor (rigidity), storage of _______ _____, sugars, and CO2 in the form of ______

Answer 16

cytoplasmic pH, amino acids, malate

Question 17

what is Tonoplast

Answer 17

Vacuolar membrane
that contains active transport systems that allows ion and molecule transport

Question 18

Function of Plant Vacuoles (3)

Answer 18

1. Intracellular digestion
2. Mechanical support
3. Storage

Question 19

what does Plant Vacuole Storage entail?

Answer 19

• Solutes and
  macromolecules
• Chemical storage (toxic
  compounds as well as
  pigments like
  anthocyanin).

Question 20

what does Plant Vacuole Mechanical support entail?

Answer 20

turgor pressure
* Gives rigidity to plant —supports soft tissues
* Stretches cell wall during growth

Question 21

what does plant vacuole Intracellular digestion entail

Answer 21

comparable to
lysosomes—slightly low pH (5.0), acid hydrolases

Question 22

the cytoskeleton is a Dynamic network of interconnected _______ and _______ that extends
throughout the ______ (and some organelles) of eukaryotes.

Answer 22

filaments, tubes, cytosol

Question 23

Functions of the cytoskeleton: (4)

Answer 23

1) structural support, 2) spatial organization within
cell, 3) intracellular transport, and 4) contractility and motility.

Question 24

what is Extension
of neurites

Answer 24

projections from
neuronal cell body
that develops into
dendrites / axons

Question 25

Components of the Cytoskeleton (3)

Answer 25

1) microfilaments
2) microtubules
3) intermediate filaments

Question 26

characteristics of Axonemal MT

Answer 26

• Highly organized, stable
• Part of structures (axoneme) involved in cell
  movement (e.g., cilia, flagella)

Question 27

characteristics of Cytoplasmic MT

Answer 27

• Loosely organized, very dynamic
• Located in cytosol

Question 28

characteristics of Microtubules (MT) (2)

Answer 28

• Largest cytoskeletal element (25 nm diameter).
• Polymer of two different proteins (monomers):
  α-tubulin and β-tubulin.

Question 29

describe Microtubules Structure

Answer 29

• α/β heterodimers
  polymer
• α/β heterodimers form long protofilaments
• 13 protofilaments form longitudinal array creating
  an hollow cylinder

Question 30

Microtubules Structure: Heterodimers are aligned in the same direction
(head to tail) creating ________ ________ (________)

Answer 30

structural polarity
(orientation)

Question 31

MTs have a fast-growing _____ _____ and a slow-
growing ______ _____.

Answer 31

‘plus’ end, ‘minus’ end

Question 32

This _______ _______ is very important for MT
growth and the direction of movement of _______
along MT

Answer 32

structural polarity, material

Question 33

Microtubule-Organizing Center (MTOC) is the central site of what

Answer 33

MT assembly (microtubule)

Question 34

MTOC is only found in

Answer 34

eukaryotic cells

Question 35

Best studied MTOCs are (2 pts)

Answer 35

1) the basal bodies associated with cilia and flagella

2) the centrosome associated with spindle formation.

Question 36

what do Microtubule-Associated Proteins (MAPs) do

Answer 36

• Modulate assembly, function
• Mediate interactions with other cellular structures (e.g., vesicles/organelles)
• bind MTs

Question 37

Two main types of Motor Proteins. name them

Answer 37

kinesin and dynein

Question 37

name the two major classes of MAPs

Answer 37

Non-Motor Proteins and Motor proteins

Question 38

different MAPs are expressed in different cell types this contributes to what

Answer 38

the growth disassembly of Mts

Question 38

what do MT-Associated Non-Motor Proteins do

Answer 38

• Control MT organization in cytosol (e.g., Tau protein in neurons).
• Defective Tau protein → neurofibrillary tangles → Alzheimer’s disease [and
  other neurodegenerative disorders (tauopathies)]
• Stabilize MTs or stimulate assembly

Question 39

what do kinesin and dynein do?

Answer 39

• Use ATP to generate force.
• Can move material along MT track.
• Can generate sliding force between MTs

Question 40

Kinesin
_____ end-directed

Dynein
____ end-directed

Answer 40

plus, minus