Organelles

Question 1

What are the jobs of the RNAs?

Answer 1

mRNA determines the AA sequence, tRNA puts the AA, rRNA fixes the tRNA in its place.

Question 2

Where do ribosomal proteins (proteins for the ribosome) get synthesized?

Answer 2

In the ribosomes but are then thrown back to the nucleus to combine with the rRNA to form ribosomes.

Question 3

What are structures formed during high levels of protein synthesis? How do we know of their existence using tracing techniques?

Answer 3

Polyribosomes, the RNA that they carry are anionic –extremely basophilic – and are very visible when stained using blue methylene, blue toluidine, and others.

Question 4

What is the flow of protein elimination in cells?

Answer 4

Misfolded proteins are ubiquitaned on their lysine residues, forming polyubiquitin and being targeted by proteosomes.

Question 5

True or false

Prokaryotes do not have polyribosomes!

Answer 5

False, they do.

Question 6

What are the 2 types of endoplasmic reticulum?

Answer 6

The rough and smooth

Question 7

What is the purpose of RER? Correlate this with cells which you can commonly find RER in!

Answer 7

RER synthesizes protein and are therefore apparent in acini cells, plasma cells, and fibroblasts.

Question 8

What is the difference between RER RPs and cytoplasmic RPs?

Answer 8

RER RPs are made for membrane-bound organelles, membrane protein, and exocytosis

Cytoplasmic RPs are made for internal cell usage and to be sent to the nucleus (not fused)

Question 9

What is a signal sequence in polypeptides?

Answer 9

When translated from 5’ to 3’, the 5’ (N-terminus) sequence of the mRNA will be translated to 6 or more hydrophobic amino acids, this sequence of amino acids is what we call a signal sequence.

Question 10

What do these signal sequences get attached by? What is the significance of that?

Answer 10

Signal recognizing proteins (SRPs).

SRPs are important since they avoid premature polymerization.

Question 11

What is the flow of RER RPs translation?

Answer 11

mRNA is attached to the ribosome, the signal sequence is translated and attracts signal recognizing proteins which then go on and attach to ER SRP-receptors as the 60S subunit of the ribosome attaches to the ribosome receptor. The SRP is then released and the signal sequence portion of the polypeptide is translocated into the translocon of the ER membrane

Question 12

Apa lima modifikasi protein pada RER?

Answer 12

Glikosilasi — N-terminus of residu aspargine diberi olisakarida.

Pelipatan — Protein dilipat menjadi bentuknya.

Disulfilasi — Gugus sistein diberikan gugus sulfur untuk memperkuat struktur tersier dan tertier.

Lipidisasi — Terutama di protein terkait-membran.

Assembly — Penyusunan dan pembentukan protein yang sifatnya multimerik.

Question 13

Bagaimana cara RE kasar menanggulangi kesalahan pelipatan protein?

Answer 13

Sistem ER-associated degradation yang mampu mendegradasi protein yang salah lipat.

Question 14

Apa akibat defisiensi ERAD?

Answer 14

Osteogenesis imperfekta bisa menjadi akibat dari keburukan kualitas prokolagen akibat kegagalan ERAD.

Question 15

True or False

Smooth ERs can be stained by methylene blue!

Answer 15

False, they aren’t basophilic since they don’t contain polyribosomes, therefore they don’t contain basophilic rRNAs.

Question 16

Apa tiga fungsi utama SER? Jelaskan kaitannya dengan sel-selnya!

Answer 16

1. Produksi fosfolipid dan steroid — banyak ditemukan di korteks adrenal.
2. Penyimpanan dan pelepasan kalsium — banyak ditemukan di retikulum sarkoplasma.
3. Detoksifikasi (salah satunya oleh sitokrom P450) — banyak ditemukan di hepatosit.

Question 17

What is PLTP and its function?

Answer 17

Phospholipid transfer proteins that transfer phospholipids to HDL to modulate their size.

Question 18

What is neonatal jaundice typically caused by?

Answer 18

Failure of SER to convert bilirubin into an excretable bilirubin.

Question 19

Where does the golgi complex stay in most cells?

Answer 19

Near nuclei.

Question 20

Where do transport vesicles join the golgi apparatus?

Answer 20

The cis face

Question 21

What is the difference between transporter and secretory vesicles?

Answer 21

Transporter vesicles enters the cis face and goes through the middle cisterni, secretory vesicles pop from
the trans face.

Question 22

What are the protein coats that regulate anterograde and retrograde flow of vesicles?

Answer 22

COPII protein complex (anterograde) and COPI protein complex (retrograde).

Question 23

How do lysosomes form?

Answer 23

Lysozymes are produced in RER and transported into the Golgi aparratus, it then buds off as the lysosome immediately.

Question 24

What happens at the cis golgi?

Answer 24

1. Cleaving of N-oligosaccharides.
2. Addition of mannose-6-phosphate to N-oligosaccharides of lysozymes.

Question 25

What happens at the medial cisternae of Golgi apparatus?

Answer 25

1. N-terminal oligosaccharides are modified further. 2. Glycosilation of the —OH of certain lipids and serine & threonin residues. 3. Glycoprotein and glycolipids are grouped in specific proteins.

Question 26

What happens at the trans cisternae of the Golgi apparatus?

Answer 26

1. Sialic acid is used as a terminal sugar for certain oligosaccharides; 2. Sulphatization of certain treonine residues; 3. Specific vesicles are chosen and separated.

Question 27

Why don’t lysozymes destroy the cell it inhabits immediately?

Answer 27

The cytoplasm is at a pH of 7.2, unlike the optimal activity of lysozymes (5.0)

Question 28

What is the temporary organelle which results from the fusion of lysosome and phagosomes?

Answer 28

Heterolysosomes.

Question 29

What about the macromolecules that aren’t digestible by lysosomes?

Answer 29

They form residual bodies.

Question 30

What about indigestible material in amitotic and old-aged cells?

Answer 30

In old aged cells like neurons and cardiomiocytes, the form bodies called lipofuscin which can impair the cell’s function.

Question 31

What is the function of lysosomes other than to digest exogens?

Answer 31

They digest organelles that no longer work, creating organelles called autophagosomes.

Question 32

How does ERAD eliminate misfolded proteins?

Answer 32

Sends it to the cytosol.

Question 33

What is the structure of the proteosome?

Answer 33

4 rings of proteins (7 proteins each) with each cylinder containing ATPases and recognizing ubiquitin containing chaperones.

Question 34

What exactly are endosomes?

Answer 34

A combination of multiple vesicles

Question 35

What is a rare mitochondrial disorder?

Answer 35

MERRF (myoclonic epilepsy with ragged red fibers) - tRNA of lysine mutation on skeletal muscles

Question 36

What disease can lipofuscin cause?

Answer 36

Alzheimers and Huntington’s disease.

Question 37

Why is the inner mitochondrial membrane impermeable?

Answer 37

Cardiolipin makes it impermeable, ensuring chemical and electrical insulation.

Question 38

What does catalase do as a peroxidase?

Answer 38

Eliminate H2O2 created by oxidase activity.

Question 39

Where does peroxisome come from?

Answer 39

The ER releases two preperoxismal vesicles containing lipids and membrane proteins that make up two distinct translocon monomeres. These two vesicles combine to form the peroxisome with one translocon which enables protein intake from the cytosol.

Question 40

True or False? The peroxisome, like the mitochondria is divisible!

Answer 40

True