Lecture 4/ Chapter 4 Flashcards Preview

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Flashcards in Lecture 4/ Chapter 4 Deck (29):

What are the 4 fates of proteins made on a free floating ribosome in the cytoplasm?

Noblemen married pretentious crooks.

1) Nucleus
2) Mitochondria
3) Peroxisomes
4) Cytoplasm


What are the 5 fates of proteins made on membrane bound ribosomes of ER?

1) ER
2) Plasma membrane
3) Secretory vesicles
4) Lysosomes
5) Golgi


If the peptide is hydrophobic, it signals translation to stop in the cytoplasm and move to the ___



What do signal sequences that import proteins into the nucleus contain?

They have short, basic aa sequences. Usually made up of lysine and arginine


What do signal seq importing into mito have?

They are long, 70-80 amino acids near the N terminus that tell where in the mito to go. They might also have sequences that tell where in the mito to go. Some mitochondriopathies occur d/t errors in this sequence


What do signal sequences importing into peroxisomes have?

They have SKL. This is Serine, Lysine, Leucine


What is KDEL?

It is a tetra peptide signal sequence that tells the protein to return the ER*** ON THE TEST. Also may play a role in some forms of dilated cardiomyopathy


What are some properties of chaperone proteins?

Widely conserved from bacteria to humans, many are HSP, they can be induced by conditions hat cause unfolding of newly synthesized proteins, they can bind to mis-folded and aggregated proteins; chaperone them to proteasome for degradation. They are also found in many cellular compartments: cytosol, golgia, nucleus, mito, ER, peroxisomes


How are chaperone proteins induced?

They can be induce by conditions that cause unfolding of newly synthesized proteins (eg. elevated temp and toxins)


What do peroxisomes do?

They neutralize free oxygen radicals using super oxidize dimutase


What type of disease is Zellweger syndrome and neonatal adrenoleukodystrophy?

They are diseases of defective peroxisomal targeting.


What is the mechanism behind Zellweger. syndrome and neonatal adrenoleukodystrophy (NALD)

There is a defective SKL signal sequence that is mutated. This causes peroxisomal bound proteins not to make it in.


What is the purpose of a start-transfer sequence?

It is located on a transmembrane protein; It functions to stop threading into the lumen-- however-- IT DOES NOT stop translation from occurring


What end of the Golgi is closest to the nucleus?

This Cis


What end of the Golgi is farthest from the nucleus

The trans


Does translation of proteins occur in the Golgi?

NO-- in ER


Where does protein sorting, addition and trimming of sugar occur?

in ER and throughout the GOLGI


Where does phosphorylation of lysosomal proteins occur?

ONLY in the CIS golgi


What occurs in the cis golgi

Phosphorylation of lysosomal proteins


Where does trimming/adding/sorting proteins occur in the Golgi?

In the medial part. the Golgi stack


Where does protein processing and sorting occur?

In the trans golgi


What are the destinations of proteins being excreted from the Golgi?

1- lysosome
2- PM
3- Secretory vesicle


Lysosomes are full of what kind of proteins?

-- nucleases, proteases, glycosides, lipase, phosphatase, sulfates, phospholipases


what kind of pump maintains acidity of the lysosome?

It is a H+ pump that utilizes ATP


What is the pH of the interior of a lysosome?



How are lysosomes generated?

Lysosomal enzymes in the golgi body are phosphorylated in the cis golgi.

clathrin coated pits containing M6P receptors bind to the phosphorylated enzyme, isolating it from other proteins in a transport vesicle.

This vesicle can join with existing lysosomes, join with other vesicles to generate new lysosomes, or be secreted.


characteristic of I cell disease

defect in phosphotransferase enzyme that phosphorylates the 6 position on specific mannose residues. This is the targeting signal for ALL lysosomal enzymes, which are ALL secreted outside the cell In this disease.

As a result, lysosomes are clogged with un degraded substances, and appear as dark "inclusion bodies" under a microscope


lysosomal diseases where no enzyme is made

Tay-Sachs, Hurler, Sandhof, Pompe


mannose 6 phosphate

targets proteins to lysosome, only non peptide address label