CELLULAR BIOLOGY Flashcards

- Cell Cycle - Cell Death

1
Q

What are the phases of the cell cycle?

A
  • G1 phase
  • S phase
  • G2 phase
  • M phase
  • G0 phase
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2
Q

Which phases of the cell cycle are collectively referred to as interphase?

A
  • G1 phase
  • S phase
  • G2 phase
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3
Q

What is the G0 phase of the cell cycle

A

A non-dividing state

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4
Q

What is quiescence?

A

Cells in G0 phase temporarily and can return to G1 phase in response to external stimuli

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5
Q

List the different tissue categories based on the rate those tissues undergo cell division/go through the cell cycle

give examples for each

A
  • Labile tissues: frequently dividing cells e.g. skin cells
  • Stable tissues: cells which divide in response to stimuli e.g. liver cells
  • Permanent tissues: non-dividing cells e.g. neurones, skeletal muscle and cardiac muscle cells
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6
Q

What is senescence?

A

Cells is senescence are metabolically active but can no longer divide

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7
Q

How do cells enter senescence?

A

Telomeres one each end of the chromosomes shorten with each cell division, eventually these telomeres are shortened so much that the cell stops dividing and enters senescence

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8
Q

Which cell types do not enter senescence?

A
  • Stem cells
  • Pathogenic cells
  • Neoplastic cells
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9
Q

How do certain cells prevent senescence?

A

The telomerase enzyme synthesises telomeres back onto each end of the chromosomes

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10
Q

How does the G1 checkpoint regulate the cell cycle?

A

Checks for:
- cell growth
- nutrients
- presence of growth factors (mitogens)
- DNA damage/mutations

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11
Q

How does the G2 checkpoint regulate the cell cycle?

A

Checks for:
- Completion of DNA replication
- DNA damage/mutations

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12
Q

How does the M checkpoint regulate the cell cycle?

A

Checks for:
- chromosome attachment to spindle fibres at the metaphase plate during metaphase

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13
Q

What are the two tumour suppressor proteins?

A
  • p53
  • pRb (retinoblastoma)
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14
Q

How does p53 regulate the cell cycle?

A
  1. DNA damage/mutations stimulate p53
  2. p53 stimulates the cell to enter G0 phase (to allow for DNA repair) or apoptosis
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15
Q

How does pRb (retinoblastoma) regulate the cell cycle?

A
  1. Un-phosphorylated Rb inhibits the transcription factor E2F
  2. The presence of mitogens stimulates cyclin D synthesis
  3. Cyclin D forms are activated complex with CDK-4 and CDK-6 known as the Cyclin D/CDK-4&6 complex
  4. This complex phosphorylates Rb, causing the transcription factor E2F to dissociate from Rb and activate gene transcription, allowing the cell to move from G1 to S phase
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16
Q

What are the different types of cell death?

A
  • Apoptosis
  • Necrosis
17
Q

Which physiological processes require homeostasis?

A
  • Homeostasis
  • Animal development
  • Immune system
18
Q

List apoptotic stimulants

A
  • DNA damage/mutations
  • Growth factor (mitogen) withdrawal
  • Hypoxia
  • Ishcaemia
19
Q

Describe the process of apoptosis

A
  1. Chromatin condenses
  2. Cytoplasm shrinks and the cell membrane ‘blebs’
  3. Cell contents is packaged into membrane bound apoptotic bodies
  4. Phosphatidyl-serine is exposed on the surface and recognised by macrophages which engulf the cell fragments
20
Q

What is the key group of enzymes required for apoptosis?

A

Caspases

21
Q

List necrotic stimulants

A
  • Oxygen deprivation
  • Physical agents (mechanical trauma, extreme heat, radiation, electric shock)
  • Chemical agents/drugs
  • Pathogenic agents
22
Q

Describe the process of necrosis

A
  1. Chromatin clumps together
  2. Cell and organelles swell, causing the cell to lyse
  3. Cell contents is spilled out into the surroundings, triggering an immune response