Intracellular Compartments and Protein Sorting: Part 2 Flashcards Preview

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Flashcards in Intracellular Compartments and Protein Sorting: Part 2 Deck (40):
1

What are the two different ways a single pass transmembrane protein can be oriented in the ER membrane?

1. with the carboxy end in the ER lumen
2. with the amino end in the ER lumen

2

What are the two sites of a translocator protein? Which way does the translocator open?

1. hydrophobic stop-transfer binding site
2. hydrophobic start-transfer binding site

opens laterally

3

The path of a transmembrane protein from translation to the PM goes from ______ --> ______ --> _______ --> ______

cytosol --> ER --> Golgi --> PM

4

What process occurs in the Golgi?

-glycosylation of lipids and proteins

5

What is the definition of the Golgi apparatus?

-receives proteins and lipids from ER, modifies them, and then dispatches them to other destinations in the cell

6

Where does protein glycosylation actually start? Which process occurs in the Golgi and is required for mature proteins?

1. ER
2. complex oligosaccharide processing

7

Golgi has different enzymes in each _____

cisterna

8

What does the process of membrane insertion result in?

-membrane protein asymmetry (each protein is inserted into the membrane in the ER in a specific manner)

9

How is protein asymmetry maintained?

through vesicular transport

10

What is an endosome?

-membrane-bound organelle that carries materials newly ingested by endocytosis and passes them to lysosomes for degredation

11

What is a lysosome?

-small sac of digestive enzymes that functions in degrading worn-out organelles, as well as macromolecules and particles taken into the cell by endocytosis

12

Where is endocytosed material found?

-in the early endosome

13

Lysosome proteins are delivered to _____ directly from the _____ in ______

endosome
Golgi
vesicles

14

Where are lysosome proteins found? What are the three compartments called?

-in heterogenous looking compartments
-late endosome, endolysosome, lysosome

15

Why do mature lysosomes fuse with endosomes?

-to recycle lysosomal proteins

16

Lysosomes are the main site of ______ _____ which contain approx. 40 types of _____ _____

intracellular digestion
hydrolytic enzymes

17

What type of environment do enzymes in lysosomes require? (high or low pH?) Why?

acidic environment/low pH; protects the contents of the cytosol from digestion

18

How are lysosomes acidified?

by a proton pump (V-type ATPase)

19

Lysosomal membrane proteins are _______ to protect them from proteases in the _______

glycosylated
lumen

20

What are some products of digestion that are transferred out of the lysosome to the cytosol?

AA, sugars, nucleotides

21

What are classical lysosomes?

-when the majority of endocytosed material has been digested

22

True or False.
Lysosomal proteins from the ER and Golgi are always incorporated into endosomes at the same stage.

False

23

Where are lysosomal hydrolases found?

early and late endosomes

24

How much of the cell volume do plant vacuoles occupy?

30-90%

25

List five processes/functions involving plant vacuoles.

1. digestion
2. nutrient storage
3. waste storage
4. increasing cell size
5. turgor pressure

26

What is turgor pressure?

-when vacuoles get much larger and push the cytoplasm gets against the membrane

27

The volume of a plant cell increases without increasing the volume of the ______

cytosol

28

What is the function of peroxisomes?

use molecular oxygen to oxidize organic molecules

29

What do oxidative reactions produce?

hydrogen peroxide

30

Where do peroxisomes function?

in the breakdown of long fatty acid chains

31

What kind of proteins are found in peroxisomes?

-proteins inserted into the ER
-proteins imported from the cytosol

32

Describe the movement of proteins (3 ways)

1. within cell, between different compartments
2. out of cell
3. into cell

33

Where is protein synthesis initiated?

cytosolic ribosomes

34

Describe the post-translational process. Which components are unfolded and which are folded?

-proteins are fully synthesized in the cytosol before sorting
-unfolded: mitochondria, plastids
-folded: nucleus, peroxisomes

35

How does a nuclear protein get into the nucleus? This process can be regulated by _______ _______

-gated transport; occurs through NPC
-intracellular signals

36

A protein with a normal nuclear import signal is found in the _____.
A protein with a mutated or deleted signal is found in the ______.

nucleus
cytosol

37

What are three additional factors required for transcription initiation?

1. activator
2. enhancer site
3. DNA loop

38

What is the estrogen receptor?

-a ligand-modulated regulator of transcription

39

What happens when estradiol is NOT present?

estrogen receptor remains in the cytosol

40

What happens when estradiol enters the cell?

-binds to estrogen receptor
-ligand-bound ER moves into the nucleus through NPCs
-binds to enhancer sites in the genome and activates transcription of target genes