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Ochem > 7.21-7.30 > Flashcards

7.21-7.30 Flashcards

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1
Q

primary site of synthesis of cell’s phospholipids

A

ER

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2
Q

what pathway is used to make phospholipids?

A

Kennedy pathway

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3
Q

Kennedy pathway

A

2 fatty acyl CoA attached to glycerol 3-P to form diacylglycerol, which is hydrophobic enough to insert in c-face of membrane

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4
Q

how are polar heads added to DAG

A

head group is phosphorylated first by CDP, then head group + P is transferred to DAG, releasing CMP

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5
Q

most abundant membrane p-lipid

A

phosphatidylcholine

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6
Q

what bond is formed between fatty acids and glycerol

A

ester linkage

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7
Q

other types of phospholipids made by Kennedy pathway

A

phosphatideylethanolamine, phosphatidyl inositol, and sometimes phosphatidylserine

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8
Q

where can PE also be made?

A

mitochondria - from modifying PS that came from ER

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9
Q

what is responsible for transport of PS from ER to mito?

A

mitochondrial associated membrane

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10
Q

mitochondrial associated membrane

A

specialized ER that is very close to mito, making close contact with its membrane

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11
Q

where does most sterol (cholesterol) synthesis occur?

A

ER

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12
Q

following phospholipids’ synthesis in the ER, some must be transferred to ____ other membranes in the cell _______ _____________

A

all, not randomly

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13
Q

phospholipid transfer proteins

A

thought to move lipids from one bilayer to another
- can’t account for membrane growing, after they bring lipid to membrane they leave with a different one

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14
Q

flippases

A

needed to flip about half of newly-synthesized lipids from ER c-face to non-c-face

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15
Q

are flippases random?

A

can be, but other phospholipid translocators must be more selective

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16
Q

ex. of phospholipid concentration difference in membrane

A
  • non-c-face of PM: PC
  • c-face: PS, PE, PI (except for GPI-anchored)
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17
Q

morphological characteristics of ER

A
  • large, flat sheets (cisternae) - RER
  • long, curving tubules - SER
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18
Q

where are the sheets of the ER usually found

A

next to nuclear envelope

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19
Q

where do tubules of ER extend

A

in network throughout cell, contacting other organelles and PM

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20
Q

RER

A

especially abundant in cells which secrete proteins like Ig (plasma B cells) and hormones (B-islets of Langerhans)

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21
Q

what is SER responsible for

A
  • lipid metabolism steroid synthesis
  • glycogen metabolism
  • drug detoxification
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22
Q

SER is especially abundant in which cells?

A
  • those that secreted steroid hormones (Leydig cells, ovary follicular cells)
  • liver hepatocytes
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23
Q

true or false: SER increases with increase in drug use

A

true

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24
Q

SR (sarcoplasmic reticulum)

A

in skeletal muscle cells, stores intracellular Ca2+, contains calsequestrin

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25
calsequestrin
protein that has several Ca2+ binding sites in SR
26
other examples of Ca2+-binding protein in non-ms. cells
- calreticulin - calnexin - BiP - PDI
27
calreticulin is both a _____________ and a ___________________
glycoprotein chaperone and a Ca2+-binding protein
28
BiP, calnexin, calreticulin function __________ efficiently when ER Ca2+ stores are depleted
less
29
prolonged calcium depletion in the ER can induce what?
UPR
30
how is UPR induced?
1. Ca2+ ER stores deplete3d 2. BiP, calreticulin, etc. less efficient 3. less chaperones to fold proteins 4. induce UPR to make chaperonins
31
Ca2+ release from ER is sometimes implicated in triggering _____________
apoptosis
32
tubular elements of the ER are in continual flux, and are often aligned to _____________
cytoskeleton
33
true or false: cytoskeleton not required for formation of tubules/networks in vitro
true
34
cytoskeleton role for ER networks
after it forms, it is properly distributed
35
cells are able to regulate the ________ and ________ of their ER (rapidly)
size, shape
36
response of cell to increase in drug like phenobarbital
SER expands to remove the drug
37
ex. of cells regulating size/shape of ER
- drug increase - B-cell activation - mitosis/meiosis
38
what happens to RER when B-cell activated and differentiation to plasma and memory B-cells occurs
plasma-B cells proliferate their RER to secrete large amounts of Ig proteins
39
when does the ER sometimes fragment
during mitosis/meiosis, then partitioned into progeny cells
40
signal sequence for nucleus
internal signal patches consisting of non-contiguous aa residues brought together by tertiary/quaternary structure
41
true or false: nuclear localization signals are removed after import through nuclear pore complexes
false
42
why are NLS not removed?
1. many proteins might need signal again if they are outside after telophase 2. difficult to remove internal signals
43
which organelles can import folded proteins
nucleus, peroxisome
44
which organelles must imported unfolded proteins
mitochondria, chloroplasts
45
TOM
translocase of outer membrane (mito)
46
TIM
translocate of inner membrane (mito)
47
mitochondrial targeting signal
N-terminal amphipathic alpha-helical stretch of 20-50 aa residues - hydrophobic sequences on side of helix, basic aa residues on other side
48
what is required to get into the matrix
ATP and charge difference (electrochemical gradient)
49
what is necessary to prevent folding of protein prior to translocation for both mito and chloro
chaperone cytosolic hsp70
50
true or false: protein going into mito is 100% unfolded
false - still need to keep alpha-helical stretch - unfolded right as going into translocase
51
purpose of TOM and TIM being in close proximity
so proteins don't dissociate into intermembrane space
52
mtHsp70
binds protein as it emerges from channel - acts as ratchet or motor - requires ATP energy
53
where does membrane potential across inner membrane come from
ETS
54
what are mt-signal sequences cleaved by
soluble mitochondrial processing protease (MPP)
55
Oxa1p pathway
integrates transmembrane IMPs in mt-inner membrane from mito matrix
56
true or false: first targeting sequence is removed once protein gets into mito matrix
true
57
how many signals to get to mito matrix from cytosol
1
58
how many signals to get to inner membrane from cytosol
2
59
TOC
translocon of outer envelope of chloroplasts - met by pre protein first
60
TIC
translocon of inner envelope of chloroplasts - attached to TOC
61
TAT (Twin-Arginine-translocation) system
uses second signal sequence once protein in storm to get protein into thylakoid membrane or lumen
62
what does translocation across thylakoid membrane require
- electrochemical gradient - pH gradient
63
PTS1 signal
peroxisome C-terminal
64
PTS2
peroxisome N-terminal
65
what happens to peroxisomal signal receptor
carried into peroxide also, then exported alone to be used again
66
why does peroxisome translocation need to be tightly regulated
internal environment of peroxisomes would be toxic to the cell

Ochem (22 decks)

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