Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOL2200 > Module 1: Organelles > Flashcards

Module 1: Organelles Flashcards

1
Q

Allosteric Regulation I

A

Change in protein structure/function due to non-covalent binding by a ligand (eg. calcium, nucleotides, another protein!)

Ca2+ interactions changes calmodulin (CaM) tertiary structure to allow binding to a target protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Allosteric Regulation II

A

Guanosine‐triphosphate (GTP) binding changes protein structure to increase enzymatic activity (on)

Guanine nucleotide exchange factor (GEF) – switch out GDP for GTP

GTPase Activating Protein – increase GTPase - which is an enzyme that bind to GTP and hydrolise it to GDP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Post-translational Modifications (PTM)

A

Covalent modifications that changes protein structure with varied consequences.
* Changed activity
* Target for degradation (protein death)
* Changed cellular location
* Changed structure or organisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Common protein PTMs:

A
  • Nitrosylation
  • Glycosylation
  • Methylation
  • Acetylation
  • Lipidation
  • Proteolysis
  • Ubiquitination

GLAM-PUN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The Nucleus

A

DNA within codes most proteins in a cell

Transcription determines the nature of cell/organism

Complex organisation

Nuclear transport essential to link the process of transcription and translation which are separated by nuclear membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Nuclear Architecture - Membrane

A

Membrane—2 membranes and a nuclear lamina (nuclear envelope)

Inner membrane defines nucleus

Outer membrane continuous with rough ER

Lamina is a meshwork of filaments for structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Nucleolus/nucleoli

A

Sub-organelle

No membrane

Site of ribosome biogenesis (the process of creating ribosomes in a highly regulated manner)

Formed around regions of DNA encoding ribosomal RNA (rRNA)

Specifically tandem repeated clusters of rRNA genes – Nucleolar Organizer Regions (NOR).
* Hotspot of transcriptional activity (~80% of total RNA in cell is rRNA).
* Thus, nucleoli are genetically defined structures formed as a result of
making ribosomes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Nuclear Architecture - Nuclear bodies

A

Membraneless nuclear sub compartments

Concentrated regions of protein and RNA

Associated with transcriptional RNA processing activitie

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Chromatin

A

Packaging of over 2m of DNA within nucleus

Dynamic structure (extended or condensed)

Structure determines gene expression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Regulation of Chromatin Structure

A

Histone tails (N- or C-term) extending from nucleosome can be targets of several PTMs

HETEROCHROMATIN

Unacetylated: chromatin is highly condensed (transcriptionally inactive)

EUCHROMATIN

Acetylation – chromatin is less condensed (transcriptionally active)

Histone PTMs represents a “histone code” to determine gene expression
(The “histone code” is a hypothesis which states that DNA transcription is largely regulated by post-translational modifications to these histone proteins.)

Proteins that modify histones control chromatin structure and access of DNA to replication, transcriptional and repair machinery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Transcriptional Machinery

A
  1. Transcriptional activators bind to DNA to recruit chromatin remodelling complexes to “open up” chromatin structure
  2. They also recruit a protein bridge (mediator) to help recruit transcription factors to a promoter sequence
  3. Mediator complex facilitates assembly of the preinitiation complex that includes loading a RNA polymerase (RNA pol II) on DNA
  4. After initiation, transcription is paused by an elongation factor complex (NELF/DSIF)
  5. Elongation pause is relieved by phosphorylation and remodelling of the elongation factors by a cdk/cyclin pair (P-TEFb)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The Nuclear Pore Complex (NPC

A

Spans both nuclear membranes

Sole gateway in/out of nucleus

Allows passive diffusion of small molecules

Human NPCs are large— ~125MDa

Comprised of ~30 nucleoporins (Nups)

Different Nups are repeated 8, 16, 32 or 64 times

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Laminopathies - nuclear diseases

A

Genetic mutations that impact lamins, nuclear membrane proteins connected to lamins or proteins involved in processing or maturation of lamins

  • Premature Ageing
  • Peripheral and sensory neuropathies
  • Familial Partial Lipodystrophy
  • Muscular Dystrophies and cardiomyopathies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The ER

A

Largest continuous membrane structure in a cell

Extensive lace-like network roughly divided into smooth and rough ER

Surface of Rough ER membranes decorated with ribosomes and sites of protein synthesis (translation)

The life of secreted and plasma membrane proteins start at ER: secretory pathway

Nascent proteins folded, modified and assembled within ER lumen

Important roles in protein quality control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

ER Organisation

A

Rough ER has sheet-like structure or “cisternae” (flattened membrane)

Smooth ER has a highly branched, “tubular” morphology

The whole thing (along with nuclear membrane) is one continuous network with common luminal space.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Shaping of ER Membrane

A

Reticulons are responsible for membrane curvature

Reticulons are inserted into ER membranes in a wedge-like conformation to curve the bilayer

17
Q

Getting a Protein into the ER Lumen

A

Requires targeting signal

For secreted proteins, ER signal located at N-terminus of nascent polypeptide

Cleaved following targeting

ER targeting happens at the same time as protein synthesis—”Cotranslational Translocation”

18
Q

Cotranslational Translocation

A

Adaptor complex, the signal recognition particle (SRP)

Binds to both the large ribosomal subunit and the signal sequence of the growing peptide

Receptor for SRP in the ER membrane

Translation is halted until the ribosome gets to ER translocon

Docking of the SRP to its receptor opens up a channel allowing the translocation of the newly synthesised peptide

Signal peptidase in the ER cleaves the signal sequence off the polypeptide

Poly peptides fold with the lumen of the ER

19
Q

ER Membrane Proteins

A

Classified by topology

Peptide synthesis is unidirectional, so different mechanisms are required for different membrane topologies

20
Q

Insertion of Type I Membrane Proteins (single transmembrane α-helix protein)

A

Initial steps are identical to translocation of secreted proteins

Insertion into membrane requires a “stop-transfer anchor” (STA) signal

Hydrophobic amino acids (20-25) that em-beds into lipid bilayer

21
Q

Insertion of Type II Membrane Proteins (polytopic transmembrane α-helical protein)

A

DO NOT have a cleavable N-terminus signal sequence

Translation initially occurs in cytoplasm

Internal ER targeting sequences is then recognised by SRP and directed to ER translocon

Internal targeting sequence also doubles as a “Signal-anchor sequence” (SA)

Once SA sequence is embedded, it is moved laterally along the bilayer and ribosome continues cotranslation into ER lumen

22
Q

Insertion of Type III Membrane Proteins (transmembrane β-sheet protein)

A

Same topology as Type I but translocation mechanism is similar to Type II

Does not have a cleavable N-term signal sequence

Uses a signal-anchor sequence but positioned very close to N-terminus

23
Q

Protein Folding and Quality Control

A

Protein folding and quality control

Newly synthesized proteins in ER undergo several modifications

Fold and assemble properly into mature complex prior to leaving ER (QC) to the Golgi (logistics)

Improperly folded proteins are targeted for destruction

Principal modifications include:

Glycosylation. Covalently linked with oligosaccharides (sugar polymers or glycans)

  • Disulphide bond formation
  • Protease cleavage (Proteolysis)
  • Assembly quaternary structures
24
Q

Glycosylation

A

Many secretory proteins and membrane proteins are sugar-modified (glycoproteins)

Transfer of a chain of sugars (glycans) from a precursor catalysed by glycosyltransferases

Glycans can be further modified after initial transfer.

25
Q

The Mitochondria

A

Multi-membrane organelle

Site of aerobic oxidation

Powerhouse of the cell

Plant equivalent is chloroplast

Have their own DNA

Size and coding capacity of mtDNA vary between organisms

Always code mitochondrial proteins

The rest coded by nuclear DNA and imported

mtDNA is inherited cytoplasmically
mtDNA is inherited maternally

Evidence suggests that mitochondria evolved from bacteria that were endocytosed by ancestral cells for mutual benefit: endosymbiosis

26
Q

Mitochondrial Organisation

A

Outer membrane –smooth

Inner membrane – has invaginations called cristae

Intermembranous space occurs between the outer and inner membranes

Lumen within the inner membrane – matrix

Matrix contains the mitochondrial DNA and mitochondrial ribosomes

Can vary from individual spheroid/ovoids to …

27
Q

Mitochondrial Fission/Fusion

A

Mitochondrial morphology related to balance of fusion and fission events

Fission: Mitochondrial Fission Factors (MFF)

  • Recruit G-proteins (DRP-1) that hydrolyse GTP to constrict or pinch membranes

Fusion: Mitofusins (MFN)

  • G-proteins that hydrolyse GTP to help membrane fusion
  • Different MFNs on outer and inner mito-membrane
  • Mito fusion is a two step process: outer membrane fusion followed by inner membrane fusion
28
Q

Golgi apparatus

A

a basket or ribbon like organelle located near the perinuclear region

organised around the centrosome/ MTOC

distinct from nuclear, er and plasma membranes

29
Q

Golgi organisation: stacked cisternae

A

distinctive morphology in vertebrate cells characterised by parallel stacks of flattened membrane disks (citernae) connected to form ribbons

in lower eukaryotes (e.g. yeast), it sless organised. dispersed “mini stacks” in cytoplasm instead of ribbon

some prokaryotes lack golgi altogether

30
Q

Golgi organisation: modular compartments

A

parallel cisternae are distinct from one another and organised into cis, medial and trans compartments

flanked on two sides by fenestrated tubular networks; cis golgi network (CGN) and the trans golgi network (TGN)

thus golgi is polarised

CGN received vesicles from ER - which are processed/modified/tagged as they move through the stack

secratory cargo is packaged and leaves golgi from trans face (TGN)

31
Q

Golgi Machinery: GRASPS

A

Golgi Reassembly and Stacking Proteins.
(stacking proteins that hold parallel cisternae together)
membrane associated proteins that dimerize/oligomerize

32
Q

Golgi Machinery: Golgins

A

coiled coil protein with extended rod-like conformation (tethering)

33
Q

Golgi Machinery: Requirement for microtubules

A

intact microtubule network is required to maintain
1. ribbon structure
2. perinuclear organisation

During mitosis, the reorganisation of microtubules into spindles is accompanied by restructuring of the golgi.
- temporarily fragmented into mini stacks and individual cisternae

34
Q

Formation of the golgi ribbon

A
  1. microtubule network and microtubule dependent transport clusters golgi mini-stacks at the perinuclear region
  2. tethering proteins (golgins) then draw mini stacks close to one another to allow membrane fusion
  3. golgi membrane fusion - likely by SNARE mediated docking mechanism as with vesicle membrane fusion
35
Q

Golgi transport: ER to Golgi

A
36
Q

anterograde transport

A

COPII coated vesicles move from the ER to the golgi

37
Q

retrograde transport

A

COPI vesicles move from golgi to ER

38
Q

coat proteins and sorting (signals)

A

Coat proteins not only bud off these vesicles but they also sort specific cargo into those vesicles for transport

they know to do this by sorting signals
sorting signals are on the cytoplasmic domain of membrane cargo proteins which are recognised by coat proteins

BIOL2200 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions