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Phase 1 > Intracellular Processes > Flashcards

Intracellular Processes Flashcards

1
Q

What are intracellular processes?

A

Processes that take place within a cell.

Each cellular process involves 1000s of chemical reaction however many are incompatible.

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2
Q

What are the two major strategies to segregate molecules for correct chemical reactions in the cell?

A
  1. Multicomponent complexes

2. Compartmentalisation into membrane-bound organelles

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3
Q

What is an organelle?

A

A cellular structure (subunit) that performs a specific function in a cell.

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4
Q

what do the specific proteins in the membrane of an organelle require?

A
  • need to be replenished and maintained

- transferred from cytosol (where they are made) to the compartment where they are used (organelle)

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5
Q

What is protein sorting?

A

proteins are transferred from cytosol (where they are made) to the compartment where they are used (organelle)

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6
Q

What are the three steps to proteins getting to the right place in the cell?

A
  1. proteins need to be synthesised
  2. proteins are dispatched to different locations in the cell
  3. Once at correct address proteins enter the organelle
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7
Q

How are proteins synthesised?

A
  • Process starts in the Cytosol (on Ribosomes = multicomponent complex of RNA and proteins)
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8
Q

How are proteins sent to different locations in the cell?

A

Done according to the specific ‘address labels’ contained in their amino acid sequence.

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9
Q

What are the stages of protein synthesis: translation?

A

Translation takes place at the ribosomes.
Ribosome = proteins + ribsoomal RNA and two subunits.
Ribosomes = 80S
The TRNA attaches to the MRNA creating a amino acid chain and eventually becoming polypeptide (protein)

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10
Q

Why are ribosomes the main target for antibiotic of a bacterial cell?

A

Because the Ribosome is whre protein synthesis takes place and therefore it prevents the polypeptide chain elongating and
spreading.

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11
Q

what are the 3 mechanisms of proteins getting into organelles?

A
  1. Nuclear pores - selective gates for nuclear proteins
  2. Protein translocators - for proteins moving from cytosol into ER, mitochondria, peroxisomes
  3. Transport vesicles - for proteins moving from ER onwards.
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12
Q

Why is it a challenge for proteins to get into organelles?

A

Hydrophilic (water-loving) proteins need to get across the hydrophobic (water-hating membrane) of organelle

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13
Q

What is the final destination of DNA polymerase?

A

Nucleus

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14
Q

What is the final destination of Epidermal growth factor?

A

Extracellular

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15
Q

What is the final destination of Keratin?

A

Cytosol

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16
Q

What is the final destination of melanin?

A

Melanosomes

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17
Q

What is the difference between smooth and rough ER?

A

Rough has ribosomes

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18
Q

How do ribosomes know to go to the ER?

A

The signal peptide on the protein being made.

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19
Q

What is a signal peptide?

A

A specific sequence on the N-terminal amino acid

20
Q

What is the N-terminal of an amino acid?

A

It is the start of the polypeptide (protein). The free group.

21
Q

How is the signal peptide guided to the ER membrane?

A
  • Signal-recognition particle (SRP)

- SRP receptor

22
Q

What is the SRP?

A

in the cytosol and binds to the ER signal peptide when it is exposed on the ribosome

23
Q

Where is the SRP receptor?

A

Embedded on the ER membrane.

24
Q

What happens in the translocan of the ER membrane?

A

polypeptide created is threaded through the in the ER membrane.

25
Q

What is the golgi apparatus?

A

The sorting organelle of the cell.

26
Q

Why is the golgi apparatus the post office of the cell?

A

Because it recieves proteins from one location and targets them for delivery to a second location.

27
Q

What are the three components of the golgi apparatus?

A
  1. Cis Cisterna
  2. Medial and Trans Cisternae
  3. Trans golgi network
28
Q

How are proteins sent from the ER to the golgi apparatus?

A

Carried in vesicles that fuse to become the cis cisternae

29
Q

What occurs to the proteins according to the Cis maturation model?

A

They move through the golgi stack and as they do they undergo enzymatic modification, which labels them for a specific destination.

30
Q

How does transport from the ER to the golgi and golgi to other compartments occur?

A

Continual budding and fusion of transport vesicles.

31
Q

What are the two pathways for the transport vesicles after they budded of from golgi apparatus?

A
  • Exoctyosis

- Endocytosis

32
Q

What occurs in exocytosis?

A

proteins remain anchored to ER membrane
vesicles from the ER fuse with the plasma membrane
stop translocation signal causes this.

33
Q

What occurs in Endocytosis ?

A
  • occurs due to specific address label added in golgi apparatus for lysosomal (specific sugar chain), mannose-6-phosphate
  • proeins labelled with M6P bind to specfic receptor in golgi membrane
  • intial destination = endosome which matures to become lysosome
34
Q

What are post-transitional modifications?

A

as proteins are transported along the pathway they undergo modifications.

35
Q

What are proteoglycans?

A

proteins that are extensively glycosylated

36
Q

What are glycoproteins?

A

Proteins with small sugar component.

37
Q

What does the post-transitional modifcation phosphorylation do?

A

Adds a phosphate group.

Alters activity of protein.

38
Q

What does the post-transitional modifcation acetylation do?

A

Adds Acetyl group.

In histones - regulation of gene expression

39
Q

What does the post-transitional modifcation Farnesylation do?

A

Adds Farnesyl group.

Targets proteins to cytoplasmic face of plasma membrane.

40
Q

What does the post-transitional modifcation Ubiquitination do?

A

adds upiquitin chain.

Targets protein for degradation.

41
Q

What is protein degradation used for?

A
  • required for proteins past their sell by date.
  • proteins that are faulty
  • proteins that are foreign to the cell
42
Q

What are two mechanisms for protein degradation?

A
  1. lysosomal degradation

2. Proteasomal degradation

43
Q

What are the characteristics of lysosomal degradation?

A
  • long half life protein (>20 hours) = auophagy
  • carried out by lysosomal enzymes.
    used for:
  • proteins with a long half life
  • membrane proteins brought into cell via endocytosis
  • extracellular proteins brought into cell via receptor-mediated endocytosis.
  • pathogenic proteins brought into the cell via phagocytosis.
44
Q

What are the characteristics of proteasomal degradation?

A
  • short half life. (seconds or minutes)
  • takes place in the cytosol of proteasomes
  • Proteins with specific PEST sequence
  • proteins tagged with ubiquitin
45
Q

How does proteasomal degradation occur in the proeasomes?

A
  • in the cytosol
  • walls formed by an proease enzyme - the active site is inside cylinder
  • protein stoppers at either end have to open to allow protein that is going to be degraded to get in
  • ATP-dependent.

Phase 1 (4 decks)

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