Molecules to cells

Question 1

What occurs to the nuclear envelope during the cell cycle?

Answer 1

It is disassembled and later reassembled via phosphorylation and dephosphorylation of nuclear pore proteins and lamins.

Question 2

Origin of nuclear envelope and ER

Answer 2

Invagination of the plasma membrane into the cytosol

Question 3

main difference between mitochondria, chloroplasts and golgi, ER and lysosomes.

Answer 3

mitochondria and chloroplasts arent part of the vesicular transport network

Question 4

Co-translational translocation

Answer 4

Process by which proteins are threaded across the ER membrane during polypeptide synthesis

Question 5

Main property of ER signal sequence

Answer 5

Made up of string of hydrophobic amino acids

Question 6

Main property of Nuclear localisation signal sequence

Answer 6

made up of string of basic amino acids

Question 7

stop-transfer sequence

Answer 7

signal on integral membrane proteins which enables them to be integrated into the membrane

Question 8

ER targeting signal

Answer 8

Signal sequence on proteins which enables them to be sent to the ER.

Question 9

What do N-terminal signal sequences, stop-transfer sequences and signal-anchor sequences all have in common?

Answer 9

Made from hydrophobic amino acids, which makes them all recognizable by Sec61 complex

Question 10

protein modifications at ER

Answer 10

1) cleavage of signal sequence
2) Disulphide bond formation
3) glycosylation

Question 11

Protein disulphide isomerase

Answer 11

catalyses disulphide bond formation inside the ER lumen and ensures correct and appropriate bonds form.

Question 12

Glycan

Answer 12

oligosaccharide present in ER lumen which modifies proteins by N-linked glycosylation

Question 13

Dolicol

Answer 13

Lipid donor which provides an anchor for preformed N-linked glycans at the ER membrane

Question 14

N-glycosidic bond of N-glycosylation

Answer 14

Carbon atom of first N-acetylglucosamine sugar of glycan to the nitrogen atom of asparagine

Question 15

co-translational translocation

Answer 15

when a protein is translocated whilst still being synthesised

Question 16

BiP

Answer 16

Heavy chain binding protein that acts as a chaperone using ATP to promote protein folding

Question 17

Calnexin

Answer 17

ER chaperone that specifically assists in folding of N-glycosylated proteins

Question 18

Scramblases

Answer 18

Enzyme that mediates flip-flopping of newly made lipids from cytosolic side of ER membrane to luminal side.

Question 19

if you remove the KDEL retention signal from the ER resident protein BiP it will be:

Answer 19

secreted from the cell

Question 20

If you add a KDEL signal to the C-terminus of a secretory protein like insulin it will be:

Answer 20

Retained in the ER

Question 21

What is a key function of the cis-golgi?

Answer 21

Protein sorting

Question 22

Examples of proteins which are secreted unconventionally

Answer 22

FGF2

IL 1β

Question 23

What sorts cargo entering the cell?

Answer 23

the endosome

Question 24

What does the endocytic pathway do?

Answer 24

Deliver lipids and proteins to endosomes so they can be re-used

Question 25

Pinocytosis

Answer 25

Non-selective uptake of fluid and small particles by endocytic vesicles

Question 26

During LDL endocytosis, what occurs to the receptor following uptake in the endosome and why?

Answer 26

It dissociates from the LDL due to an acidic pH. it is then recycled to the cell surface.

Question 27

Addition of a mannose-6-phosphate signal to a protein will result in it being:

Answer 27

- Retained at the ER - Sorted to secretory vesicles - Trafficked to the lysosome

Question 28

Phagocytosis

Answer 28

Uptake of large particles and microorganisms by specialised cells such as macrophages

Question 29

Autophagy

Answer 29

removal of obsolete parts of the cells and damaged organelles.

Question 30

what enzyme catalyses the fusion of autophagosomes with lysosomes?

Answer 30

SNARE proteins

Question 31

flippases

Answer 31

enzymes localised in golgi which selectively redistribute lipids in order to create specific phospholipid asymmetry across the bilayer

Question 32

Peripheral membrane proteins

Answer 32

proteins associated with the plasma membrane via binding to an integral transmembrane protein

Question 33

What is the route of protein destined for the plasma membrane?

Answer 33

ER -> golgi -> plasma membrane

Question 34

Common features of mitochondrial signal sequences

Answer 34

High content of Arg and Ser/Thr | Tendency to form amphiphillic alpha helices

Question 35

Congenital lactic acidosis

Answer 35

inherited metabolic disorder causes by a point mutation of residue 10 of pyruvate dehydrogenase subunit E1α, resulting in inefficient import of the pyruvate dehydrogenase complex causing reduced levels of PDH.

Question 36

Precursor of insulin

Answer 36

preproinsulin

Question 37

Types of preproinsulin mutation

Answer 37

Arg to Cys/His | Ala 24 converted to Asp

Question 38

Arg to Cys/His preproinsulin mutation

Answer 38

Prevents signal sequence interacting with Sec61 translocon. | Protein accumulates in cytosol causing gradual aggregation and death of pancreatic beta cells.

Question 39

Mutation which causes early onset diabetes

Answer 39

Ala24 to Asp

Question 40

Ala24 to Asp preproinsulin mutation

Answer 40

Inhibits cleavage of signal sequence causing improper folding causing ER stress due to accummulation in ER lumen. Blocks export of wild type insulin from ER.

Question 41

Mutation which causes late onset diabetes

Answer 41

Arg to Cys/His

Question 42

mylolactone is a polyketide toxin which acts to inhibit the :

Answer 42

Sec61 translocon

Question 43

70% of cases of CF is caused by which mutation

Answer 43

The loss of a phenylalanine at residue 508 of CTFR - functions as a Cl- pump.

Question 44

Molecular chaperones

Answer 44

Help proteins to fold correctly and prevent them from aggregating

Question 45

BiP in the ER lumen is an example of a...

Answer 45

Molecular chaperone

Question 46

What happens when a molecular chaperone is bonded for a prolonged period of time?

Answer 46

Causes mutant protein to be recognised as misfolded

Question 47

What happens to misfolded proteins retained at the ER

Answer 47

They are eventually degraded by a ER associated degradation

Question 48

Proteosomes and ubiquisination occurs within the ER lumen. TRUE/FALSE

Answer 48

Not present in ER lumen. | Only occurs in cytosol

Question 49

THe most common form of CF is the result of a mutation that prevents

Answer 49

CFTR protein trafficking out of the ER

Question 50

Effects of carbamazepine

Answer 50

Enhance the proteasomal and autophagic disposal of the α1-AT Z mutant - reducing the proteotoxic load on cells

Question 51

Ways membrane bound organelles can import proteins

Answer 51

nuclear pores translocation across membrane vesicular transport

Question 52

What is the role of adaptins?

Answer 52

Bind cargo receptors during formation of a transport vesicle

Question 53

CM retention disease

Answer 53

preChylomicrons accumulate in the ER and are unable to reach the golgi

Question 54

What causes chlomicron retention disease?

Answer 54

Defective Sar1 GTPase

Question 55

what increases the risk of alzheimers disease

Answer 55

Cleavage of APP producing large and long amounts of A beta peptide

Question 56

potential therapies for AD

Answer 56

Stop or reduce Aβ prod. | Reverse Aβ aggregation