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21 fall: Biochem > Test 2 Lecture 34-35 > Flashcards

Test 2 Lecture 34-35 Flashcards

1
Q

Each organelle is surrounded by its own ___

A

membrane

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2
Q

These membranes divide the cell into ___ that have different internal environments specialized for different organelle functions.

A

compartments

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3
Q

Cells employ complex mechanisms to ___ molecules between compartments.

A

transport

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4
Q

which organelle is used for protein modification, sorting, and packaging for secretion or delivery to other organelles

A

golgi appartatus

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5
Q

Which organelle is used for protein synthesis and distribution, lipid synthesis

A

ER
endoplasmic reticulum

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6
Q

which organelle is used for degradation and recycling

A

lysosomes

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7
Q

which organelle is used for sorting of materials taken up from the extracellular environment

A

endosomes

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8
Q

which organelle is used for oxidation of toxic molecules

A

peroxisomes

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9
Q

three types of transport

A

gated transport
transmembrane transport
vesicular transport

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10
Q

___ involves binding of ____ on a protein with a translocator in the membrane to be crossed.

A

protein sorting through selective transport

sorting signals (signal sequences)

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11
Q

where does protein synthesis take place

A

on ribosomes, either free floating or attached to the endoplasmic reticulum.

in the cytoplasm

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12
Q

After synthesis in the ___, proteins get sorted and transported to their destinations in different intracellular compartments

A

cytoplasm

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13
Q

free floating ribosomes will produce proteins which will be transported to the

A

nucleus

mitochondria

chloroplasts

peroxisomes

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14
Q

ER bound ribosomes will produce protein that will ___

A

be transported to the plasma membrane

secretory vesicles

lysosomes

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15
Q

signal patch vs signal sequence

A

patch- several parts of protein have to come together to trigger signal that tells protein where to go

sequence- single part usually at end of protein that tells the protein where to go

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16
Q

Signal sequences are recognized by ____ receptors that guide proteins to their appropriate destinations.

A

complementary sorting

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17
Q

gated transport

A

transport of proteins into nucleus

nucleus has “nuclear pores”

karyopherins will release FG repeats (phenylalanine/glycine) these will bind to protein and transport through pore

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18
Q

nuclear transport receptors are known as

A

karyopherins

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19
Q

the fibrils of nuclear pores contain ___

A

phenylalanine/glycine repeats (FG repeats

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20
Q

Proteins synthesized on soluble ribosomes are targeted to ___ post- translationally

A

mitochondria

will form alpha helix with +, - (hydrophobic) and neutral charges on different sides

uses alot of ATP

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21
Q

two types of receptors in mitochondria

A

TOMs (translocators on the outer membrane)

TIMs (translocators on the inner membrane)

energy demanding process- uses alot of ATP

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22
Q

Peroxisomes contain ≥50 different enzymes involved in ____ reactions.

A

oxidative

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23
Q

Peroxisomes ___ various toxic molecules that enter the bloodstream, e.g., phenols, formic acid, formaldehyde, alcohol, acetaldehyde.

A

detoxify

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24
Q

Peroxisomes detoxify and are involved in ___ and breakdown of fatty acids

A

lipid synthesis

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25
Q

Proteins are recognized by ___ to come into the peroxisomes. Import is helped by ___

A

C-terminal import signal sequence: -Ser-Lys-Leu-COO-

import involves the activity of peroxins (soluble cytoplasmic proteins)

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26
Q

“empty” peroxisomes; hereditary disease

A

Zellweger syndrome

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27
Q

Zellweger syndrome

A

“empty” peroxisomes; hereditary disease

enlarged liver, high levels of iron and copper in the blood stream, and vision disturbances.

Symptoms at birth may include a lack of muscle tone, an inability to move and glaucoma. Other symptoms may include unusual facial characteristics, mental retardation, and seizures.

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28
Q

The ER is a network of membrane-bounded branching tubules that extends from the nuclear membrane throughout the cytoplasm, enclosed by a ___.

A

continuous membrane

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29
Q

The ___ is the largest organelle in most eukaryotic cells, enclosing ~10% of the cell volume.

A

endoplasmic reticulum

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30
Q

___ is a major site of protein synthesis:

A

ER

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31
Q

Protein synthesized on the ER will travel to :

A

ER

Golgi

Lysosomes

Plasma membrane

Secreted outside the cell

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32
Q

why are there so many ribosomes attached to ER

A

ribosomes produce protein, protein has ER signal sequence and binds to ER, as protein is made it is pushed into ER, holding ribosome in place

the same strand of mRNA can have many ribosomes coding for proteins at the same time

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33
Q

ER signal sequence is

A

20 amino acids long

hydrophobic residues

34
Q

Peroxisome signal sequence

A

C-terminal import signal sequence: -Ser-Lys-Leu-COO-

import involves the activity of peroxins (soluble cytoplasmic proteins)

35
Q

nucleus signal

A

+ charge

Nuclear localization signal -Pro-Pro-Lys-Lys-Lys-Arg-Lys-Va l -

36
Q

explain ER transport

A

SRP binds to ER targeting signal of nascent peptide chains.

SRP (RNA protein complex)

SRP then drags the entire peptide with bound ribosomes- mRNA complex to the SRP recognition protein in the rough ER

this is close by to a protein translocator channel (hole), protein will go through hole as it is translated

SRP and SRP receptor are broken off once protein goes through channel

signal peptide is cleaved off by a specific signal peptidase.

Translation continues until the entire polypeptide is synthesized and the newly synthesized polypeptide resides in the lumen of ER.

37
Q

In ER tranport, After the N-terminus of the nascent peptide enters the ER channel, peptide chain elongation continues and the signal peptide is cleaved off by a ____

A

specific signal peptidase.

38
Q

Role of Stop Transfer signals in the generation of ___ proteins in the ER

A

transmembrane

protein starts synthesis into ER, then a stop transfer signal (mostly hydrophobic) will cause the protein to get stuck and rest of protein will translate into the cytoplasm

39
Q

When sorting in the ER: Secreted or lumenal proteins are___, their signal peptides are cleaved, and the soluble proteins are released.

A

translocated,

40
Q

when sorting proteins in the ER, Integral membrane proteins remain embedded in the ER membrane. Key is a ___ of hydrophobic amino acids

A

stop-transfer sequence

41
Q

Proteins undergo specific modifications (____) in the ER as part of sorting and packaging for transport to their destination

A

glycosylation

42
Q

what are two types of glycosylation

A

N linkage (asparagine)

O linkage (serine)

43
Q

N linked glycosylation

A

happens to proteins in the ER- way of marking for transport

14 sugar residues is transferred to specific
asparagine residues in the growing polypeptide chain, while translation is still in
progress.

The recognition sequence for addition of N-linked sugars is Asn-X-Ser/Thr.

44
Q

ER tranport disease

A

cystic fibrosis

45
Q

cystic fibrosis

A

inherited disease

Involves accumulation of a slightly misfolded protein important for Cl- transport in the ER
lumen

Patients suffer from the formation of thick, sticky mucus lining the respiratory and gastrointestinal tracts. Symptoms in children and adults range from mild to severe

46
Q

___ is delivery to the cell exterior of the macromolecules produced in the cell.

A

Secretory pathway (exocytosis)

47
Q

___ is uptake of macromolecules and delivery of these molecules to lysosomes, which contain digestive enzymes.

A

Endocytic pathway (endocytosis):

48
Q

basics of vesicle transport

A

donor compartment will bud off and transport to target compartment, the vesicle will bind/fuse with the target compartment and release its contents

49
Q

Types of proteins that promote budding

A

COP

clathrin (endocytosis- outside to the golgi)

COPI (Golgi cisternae and out)

COPII (ER to golgi)

50
Q

docking mechanism for vesciles

A

SNARE proteins

lives on outside and grabs floating vesicle with same piece, pull vesicle close enough that it will fuse with target compartment

to recycle snares lots of energy and adaptor proteins are needed

51
Q

Golgi apparatus has a __ face, that is closer to the nucleus and a __ face that is farther away from the nucleus

A

cis

trans

52
Q

The Golgi has a distinct morphology - flattened membrane-enclosed ___ or stacks.

A

cisternae,

53
Q

Vesicles bud from the ER, and are then transported to the ___, where they fuse with the ___ membrane.

A

Golgi

Golgi

54
Q

ER proteins are recognized by a ___ receptor in the Golgi, and are transported via vesicle exchange.

A

KDEL

55
Q

As proteins move from the cis to the ___of golgi the proteins are changed/processed and sorted

A

trans cisterna

56
Q

Three major pathways for proteins from trans golgi network:

A

trafficking to lysosomes

regulated secretion

bulk flow

57
Q

Lysosomes

A

acidic (lower pH then rest of cell)- maintains low pH through hydrogen ATPase pumps- uses ATP to pump hydrogen into lysosome

acid hydrolases

contains transporters for final products of the digestion of macromolecules

stomachs of cell- breaks down unwanted stuff

58
Q

three pathways of degradation in lysosomes

A

endocytosis- small particles

phagocytosis- big thing

autophagy- breakdown mitochondria

59
Q

explain how lysosome is formed

A

hydrolase comes for ER to golgi

phosphate and sugar added (mannose 6- phosphate- M6P)

moved through golgi and binds to M6 receptor this triggers COT protein Clath to bind to outside of golgi, forcing it to bend and eventually bud off and transport to the late endosome

late endosome pumps H in and gathers lysosomal hydrolase until it gets enough and is a lysosome

60
Q

disease caused by missing lysosomal enzymes responsible for the breakdown of glucosaminoglucans.

A

Hurler’s disease:

61
Q

Hurler’s disease:

A

missing lysosomal enzymes responsible for the breakdown of glucosaminoglucans.

symptoms including grotesque skeletal and facial deformities, skin and cardiac changes, clouding of the cornea, and mental deficiency. Also known as gargoylism; lipochondrodystrophy.

62
Q

disease from all the hydrolytic enzymes are missing from lysosomes because of a defect in GlcNAc phosphotransferase, which results in secretion of these enzymes out of the lysosomes.

A

Inclusion cell-disease (I-cell disease)

63
Q

Inclusion cell-disease (I-cell disease)

A

all the hydrolytic enzymes are missing from lysosomes because of a defect in GlcNAc phosphotransferase, which results in secretion of these enzymes out of the lysosomes.

hydrolytic enzymes stuck in golgi, never make it to the lysosome

Onsets in early childhood with symptoms including gum hypertrophy, thoracic dysplasia, congenital hip dislocation, and mental retardation

64
Q

___ is the uptake of macromolecules and particulates by the cell, and the trafficking of these from the plasma membrane to the lysosome.

A

Endocytosis

65
Q

two types of endocytosis

A

pinocytosis (drinking) -uptake of fluids and solutes via small vesicles.

Phagocytosis (eating) involves the uptake of larger particles such as microorganisms.

66
Q

Phagocytosis

A

involves the uptake of larger particles such as microorganisms.

can only be done by specialized cells such as macrophages, dendritic cells and neutrophils.

Involves activation of receptors on the surface of phagocytes

67
Q

Pinocytosis

A

“drinking”

involves the uptake of fluids and solutes via small vesicles.

Most eukaryotic cells undergo continual pinocytosis

formation of clathrin-coated pits

68
Q

Pinocytosis is a ___

Cells can ingest 100% of their plasma membrane in less than ___.

A

continuous process.

30 min.

69
Q

Endocytosis through pinocytosis of membrane internalization must be balanced by addition of cell membrane by ___.

A

exocytosis

70
Q

endocytic-exocytic cycle.

A

endocytosis through pinocytosis and exocytosis must be balanced and results in renewal of plasma membrane every 30 minutes

71
Q

Receptor-Mediated Endocytosis

A

Macromolecules from the extracellular fluid bind to specific cell-surface receptors, and these receptor accumulate in coated pits. The molecule-receptor complexes enter the cell in clathrin-coated vesicles.

Use of a specific receptor allows the cell to increase the efficiency of ligand uptake more than 1,000-fold over fluid phase endocytosis.

More than 25 different receptors function in receptor- mediated endocytosis

72
Q

explain LDL uptake into cell

A

LDL floats in ECM

LDL receptor on plasma membrane attaches to LDL

this attachment recruits adaptin and clathrin

more clathrin causes membrane to curve and eventually bud off into cell with help from dynamin

LDL will go to early endosome and be broken down by lysosomes

rececptor will be recycled and placed back onto membrane to capture more LDL

things go bad if receptor doesn’t work or too much LDL- LDL then floats in ECM and clumps together

73
Q

___ is the major coating protein for the endocytic vesicles.

A

clathrin

74
Q

what is the protein that helps bud off clathrin vesicles

A

dynamin

75
Q

familial hypercholesterolemia

A

Endocytosis-related disease

Inability of LDL to bind its receptor

things go bad if receptor doesn’t work or too much LDL- LDL then floats in ECM and clumps together : formation of atherosclerotic plaques; heart disease

76
Q

steps of secretory vesicles

A

golgi to outside

Aggregation/clumping of the secretory proteins mediated by signaling patches.

Budding of the secretory vesicles from the TGN.

Concentration of the contents of secretory vesicles through membrane recycling

77
Q

formation of synaptic vesicles in neurons

A
78
Q

Cystic fibrosis:

A

Inherited disease

Involves accumulation in the ER of a protein important for Cl- transport that is slightly misfolded

Clinical manifestation: formation of thick sticky mucus lining the respiratory and gastrointestinal tracts

79
Q

Lysosomal storage diseases:

A

The I-cell disease: missorting of lysosomal hydrolases to the plasma membrane due to a loss in the activity of a transferase responsible for the synthesis of Mannose-6-phosphate tag; substrates of hydrolases accumulate in lysosomes. Results in the pathological consequences in the nervous system

Hurler’s disease; defect in lysosomal hydrolases

80
Q

The I-cell disease:

A

The I-cell disease: missorting of lysosomal hydrolases to the plasma membrane due to a loss in the activity of a transferase responsible for the synthesis of Mannose-6-phosphate tag; substrates of hydrolases accumulate in lysosomes. Results in the pathological consequences in the nervous system

81
Q

Hurler’s disease

A

defect in lysosomal hydrolases

hydrolase does not make it out of golgi to the lysosome

Lysosomal storage diseases:

82
Q

Zellweger syndrome:

A

“empty” peroxisomes; abnormalities in brain, liver, kidneys

21 fall: Biochem (44 decks)

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