Chapter 15: Intracellular Compartments and Protein transport Flashcards
(49 cards)
1
Q
Cytosol
A
- contains many metabolic pathways
- protein synthesis
- the cytoskeleton
2
Q
Nucleus
A
- contains main genome
- DNA and RNA synthesis
3
Q
Endoplasmic reticulum
A
- synthesis of most lipids
- synthesis of proteins for distribution to many organelles and the plasma membrane
4
Q
Golgi apparatus
A
- modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another organelle
5
Q
Lyosomes
A
intracellular degradation
6
Q
Endosomes
A
sorting of endocytosed material
7
Q
Mitochondria
A
ATP synthesis by oxidative phosphorylation
8
Q
Chloroplasts (in plant cells)
A
- ATP synthesis and carbon fixation by photosynthesis
9
Q
Peroxisomes
A
- oxidative breakdown of toxic molecules
10
Q
Name the three types of protein transport and how they sort
A
- transport through nuclear pores
- transport across membranes
- transport by vesicles
(signal sequences direct proteins to the correct compartment)
11
Q
Transport through nuclear pores
A
- maintains folding
- proteins can get into nucleus if they have NLS
(protein with NLS can possibly drag others without NLS in with them) - NLS recognized by import receptor, protein translated into cytosol
12
Q
NLS
A
nuclear localization signal
13
Q
How does nuclear transport happen?
A
- energy supplied by GTP hydrolysis
14
Q
Explain nuclear transport
A
- Ran protein (small GTPase) either carries GTP or GDP, converted when needed by accessory proteins
- Ran-GAP found in cytosol converts GTP to GDP
- Ran-GEF found in nucleus release GDP and uptake GTP
- GTP important in nucleus, so nuclear import receptors can bring in and attach nuclear proteins
- binding of Ran-GTP with receptor and its nuclear protein releases the nuclear protein into nucleus
- import receptor leaves nucleus through pore into cytosol with Ran-GTP still attached, hydrolyzes to GDP and falls off to bind to another protein
15
Q
Transport across membranes
A
- proteins unfold to cross the membrane of mitochondria and chloroplasts
- proteins can cross the membrane of the endoplasmic reticulum while being synthesized
16
Q
Describe transport into mitochondria
A
- mitochondrial precursor proteins are unfolded during import
- must cross mitochondrial outer and inner membrane
- receptor with TOM on outer membrane recognizes mito. precursor protein, transports signal sequence to intermembrane space
- 2nd receptor with TIM on inner membrane recevies signal as well
- together they push signal across membranes to unfold protein
- signal sequence cleaved off by peptidase in mito matrix
17
Q
Describe endoplasmic reticulum transport
A
- an ER signal sequence and an SRP direct a ribosome to the ER membrane
- SRP binds to exposed ER signal sequence and ribosome, which slows ribosome protein synthesis
- SRP/ribosome complex binds to SRP receptor in ER membrane
- SRP released and ribosome passes from SRP receptor to protein translocator in ER membrane
- protein synthesis resumes, translocator starts to transfer growing polypeptide across lipid bilayer
18
Q
TIM/TOM description
A
- translocator of inner membrane
translocator of outer membrane
19
Q
Describe Protein sorting: vesicular transportq
A
- allows materials to exit or enter the cell through endocytosis and exocytosis
- carry soluble proteins and membrane between compartments
20
Q
endocytosis
A
- coming in, brought into cell
21
Q
exocytosis
A
- going out, vesicles fuse with plasma membrane and contents released to outside cell
22
Q
Transport vesicles
A
- bud from one membrane and fuse with another, carrying membrane components and soluble proteins between compartments of the endomembrane system and the plasma membrane
- orientation of compartments with cytosolic side facing cytosol and noncytosolic side facing lumen or outside cell
23
Q
Describe endocytic pathway
A
- extracellular molecules ingested in vesicles from plasma membrane
-delivered to early endosomes, and then from endosomes to lysosomes
24
Q
Describe outward secretory pathway
A
- protein molecules transported from ER, through golgi apparatus, to plasma membrane or endosomes to lysosomes
- some vesicles shuttle between golgi, that’s why they end up there
separate retrieval pathway returns materials from golgi to ER that are supposed to stay in the ER
25
Vesicle budding
- in vesicular transport, driven by assembly of protein coat clathrin
26
Clathrin-coated vesicles
- transport selected cargo molecules and shapes membrane into bud
- bud from golgi apparatus on outward secretory pathway and from plasma membrane on inward endocytic pathway
27
Clathrin coated vesicle transport
- adaptins bind clathrin olecules to cytosolic surface of budding vesicle
- dynamin proteins assemble around neck of budding vesicle
- dynamin molecules hydrolyze their bound GTP, with help from other proteins it pinches vesicle off
- after budding, coat proteins removed and naked vesicle fuses with target membrane
28
Vesicular transport docking
- depends on Rab proteins, tethers, and SNAREs
- all help direct transport vesicles to their target membranes
- all carry unique combination of Rab proteins, which serve as molecular markers for each membrane type(Rab and tether work together)
29
Rab proteins
-monomeric GTPases
- are recognized by tethering proteins
30
tethering proteins
- on cytosolic surface of target membrane
31
SNAREs
- additional recognition transmembrane protein
- tethering protein that has grabbed its Rab protein, v-SNAREs (snares on vesicle) interact with t-SNAREs (target membrane) to dock vesicle in place
32
How Rab proteins, tethering proteins, and SNAREs work together
- a tethering protein on membrane binds to a Rab protein on vesicle surface
- vesicle docks on target membrane
- v-SNARE on vesicle binds to complimentary t-SNARE on target membrane
- Rab and tethering proteins provide initial recognition, complementary SNARE proteins ensure transport vesicles dock at appropriate target membranes(catalyze final fusion of two membranes)
33
Secretory pathway
- operates in all eukaryotic cells
-contiously supplies plasma membrane with newly synthesized lipids and proteins
- regulated and constitutive pathways of exocytosis diverge into thr trans Golgi network
34
trans Golgi network
- diverted into secretory vesicles, where proteins are concentrated and stored until an extracellular signal stimulates their secretion
35
Exocytosis pathway
- endoplasmic reticulum
-vesicle
-golgi
-vesicle
-plasma membrane
-exit from endoplasmic reticulum is controlled to ensure protein quality(avoids bad formations)
- accumulation of misfolded proteins in endoplasmic reticulum triggers unfolded protein response(recognized by diff. types of transmembrane sensor proteins in ER membrane)
36
UPR
- unfolded protein response
- receptors span membrane, signal misinformation, and slow down translation
37
UPR in C. elegans nematode
- if you feed them glucose, they will undergo apoptosis because of unfolded protein response
- glucose causes increase in amount of insulin needed to bring glucose into the cell
- since its a secreted protein, cells translate insulin in RER
- high sugar diet leads to increased insulin, causing unfolded protein response that may contribute to diabetes
38
Options of UPR
- try to refold proteins or destroy them(make more chaperone proteins)
- try to stop the proteins from being made(slow translation)
- make more ER
- worse case scenario: cell wall undergoes apoptosis or programmed cell death
39
Phagocytosis
specialized cells take of pathogens or large particles
40
Receptor mediated endocytosis
molecules bind to receptors and taken up by cells
this is how viruses can enter cells(ex: low PH of lysosomes allows release of viral genome in to cytoplasm)
41
Pinocytosis
fluid and macromolecules from outside the cell are taken up by cells
42
LDL
- enter cells via receptor mediated endocytosis
- internlized by clathrin coated vesicles
-
43
Lysosome degredation
- materials destined for degredation in lysosomes follow different pathways to get there
- extracellular particles are taken up into phagosomes, which fuse with lysosomes, and that extracellular fluid and macromolecules are taken up into smaller endocytic vesicles, which deliver their contents to lysosomes via endosomes
autophagy- cell eats itself
44
Lysosomes
- break down worn out organelles and material endocytosed in to the cell
- enzymes are only active at low pH
-membrane compartment serves to break down a variety of molecules
- lysosome breaks, enzyme becomes inactive
45
Zellweger's syndrome
Zellweger's syndrome is a rare genetic disorder related to cell biology, specifically peroxisome biogenesis. In individuals with this syndrome, the peroxisomes, cell organelles responsible for various metabolic processes, fail to form properly. This deficiency results in the impaired breakdown of fatty acids and the accumulation of toxic substances in cells, leading to severe neurological and developmental abnormalities.
46
Phagocytic cells defense against infection
Phagocytic cells, such as macrophages and neutrophils, are essential components of the immune system. These cells possess the ability to engulf and digest foreign particles, including bacteria, viruses, and other pathogens, through a process called phagocytosis. By engulfing and destroying these invaders, phagocytic cells help defend the body against infections and play a vital role in the immune response.
47
Defects in receptor mediated endocytosis of cholesterol
Receptor-mediated endocytosis is a cellular process where specific molecules, like cholesterol, are taken up by cells via receptor proteins on their surface. Defects in this process can lead to the accumulation of cholesterol in the bloodstream, contributing to diseases like familial hypercholesterolemia. In this condition, faulty or absent receptors fail to properly regulate cholesterol levels, increasing the risk of cardiovascular diseases due to elevated levels of LDL ("bad") cholesterol in the blood.
48
Unfolded protein response can cause diabetes
The unfolded protein response is a cellular stress response mechanism triggered when the endoplasmic reticulum (ER) is overwhelmed by unfolded or misfolded proteins. In the context of diabetes, prolonged ER stress can impair the insulin-producing beta cells in the pancreas. This dysfunction can lead to inadequate insulin secretion, contributing to the development of diabetes, as insulin is crucial for regulating blood glucose levels.
49
