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Uni year 1 > Cell Biology - cell communication and division > Flashcards

Cell Biology - cell communication and division Flashcards

1
Q

What are protein kinases?

A

kinases phosphorylate proteins on serine, threonine or tyrosine residues - these all have hydroxyl side chains

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2
Q

Features of G-protein coupled receptors

A
  • single polypeptide - 7 pass transmembrane protein
  • binding ligand induces conformational change
  • alpha, beta and gamma subunits - alpha dissociates when binding occurs
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3
Q

How is growth of epithelial cells regulated?

A

main pathway - epidermal growth factor (EGF) which signals via an EGFR which is an example of an enzyme coupled receptor.

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4
Q

How are receptor tyrosine kinases activated?

A
  • dimerisation caused by binding of growth factor

- this causes transphosphorylation within the cell

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5
Q

Receptor tyrosine kinase signalling post transphosphorylation

A
  • Grb2 (an adapter protein) binds to phosphotyrosine
  • Ras (an activating protein) is recruited which promotes exchange of GDP for GTP
  • Conformational changes in Ras causes activation of downstream proteins
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6
Q

MAP kinase signalling cascade

A
  • Raf interacts with Ras
  • This activates Mek and becomes phosphorylated
  • This activates Erk
  • Erk has a number of targets including trasncription factors - entry into the cell cycle
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7
Q

When is cell proliferation required?

A
  • embryogenesis
  • tissue maintenance
  • repairing damaged tissue
  • adaptation to the environment
  • fighting infections
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8
Q

What stimulates cell proliferation?

A

Mitogenic signals from surrounding tissue

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9
Q

What do cyclin-dependent kinases do?

A
  • regulate the cell cycle by phosphorylating proteins that are important to specific cell cycle phases
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10
Q

How are Cdks activated?

A

by heterodimeric binding partner from the cyclin family

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11
Q

What are the 6 essential steps of the cell cycle?

A
  1. increased cell and organelle size (G1)
  2. overcome restriction point (G1)
  3. replicate chromosomes once (S)
  4. make sure chromosomes are fully duplicated (G2)
  5. separate duplicated chromosomes (M)
  6. separate daughter cells by cytokinesis
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12
Q

Where is the restriction checkpoint?

A

G1

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13
Q

What is required for cells to pass through restriction checkpoint?

A

mitogenic growth factor

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14
Q

What is stimulated by mitogenic growth factor?

A
  • induces transcription of immediate early genes including transcription of cyclin D
  • protein kinase sequence - map pathway via Erk into the nucleus
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15
Q

What does G1-Cdk phosphorylate?

A

retinoblastoma protein

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16
Q

What happens at the R checkpoint?

A
  • pRb acts

- ensures cells duplicate chromosomes only if stimulated by mitogens

17
Q

What happens at the G2 checkpoint?

A
  • cells cant enter mitosis until chromosomes are completely replicated in S phase
  • cells held at G2 until fully replicated
18
Q

Which Cdk does mitosis require?

A

M-Cdk which comprises of Cdk 1 and M cyclin

19
Q

What is chromosome replication triggered by?

A

S-Cdk

20
Q

What occurs at the mitotic checkpoint?

A
  • chromosomes with unattached kinetochore prevent anaphase occurring
21
Q

What occurs in prometaphase?

A

mitotic spindles attach to kinetochores

22
Q

What would happen if the mitotic checkpoint failed?

A
  • chromosomes would not segregate into daughter cells properly
  • altered chromosome number - aneuploidy
23
Q

What does p21 do?

A

inhibits Cdk activities to allow DNA to repair

24
Q

When is apoptosis induced?

A
  • when cells are no longer required
  • when cells are dangerous (infections)
  • following irreversible cell damage
25
Q

What are the steps of apoptosis?

A
  • initiator caspases activated
  • cell breaks up into membrane bound fragments called apoptotic bodies, by executioner caspases
  • dead cells removed by phagocytosis
26
Q

How are caspases activated?

A

activated from procaspases by having the prodomain removed. This activates executioner caspases.

27
Q

What is G1-Cdk formed from and what does it do?

A

cyclin D combines with cdk-4 or cdk-6 G1-Cdk

G1-cdk monophosphorylates pRb

Uni year 1 (19 decks)

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