Week 4 cells

Question 1

Phases of cell division

What are the first 3 phases called collectively?

Answer 1

1. G1 Phase: monitor cell size
2. S Phase: DNA replication
3. G2 Phase
4. M Phase: chromatin gets condensed, nuclear division, cytokinesis

Phase 1-3: interphase

Question 2

What are tumours called?

Answer 2

Benign

Malignant: break through basal lamina, invasive -> cause metastasis

Question 3

Phases that occur during M phase of cell division

Answer 3

1. Prophase: nuclear membrane dissolves
2. Prometaphase
3. Metaphase: chromosomes align, attached to mitotic spindle
4. Anaphase
5. Telophase

Question 4

How many checkpoints are there during cell cycle?

Answer 4

3

1. during G1, before entering S phase
2. during G2, after S phase and before entering mitosis
3. Mitotic checkpoint: before anaphase (are chromosomes properly aligned to mitotic spindle?)

Question 5

What are the master regulators of the cell cycle checkpoints? How do they function?

Answer 5

Cyclin-dependent kinases (Cdks):
function by binding with cyclin -> form Cyclin-cdk complex that phosphorylates different target proteins

Question 6

3 Mechanisms of regulation of Cdk activities

Answer 6

1. Periodic synthesis & degradation of cyclin -> regulate cyclin levels
2. Phosphorylation/dephosphorylation by other kinases/phosphatases
3. Cdk inhibitors (CKIs)

Question 7

What are the 2 classes of CKIs?

Answer 7

1. CIP/KIP:
   CDK-interacting protein/kinase inhibitory protein -> inhibit all classes of Cdks
2. INK4 proteins:
   only inhibit Cdk4/6 in G1 checkpoint

Question 8

Where is the site for rRNA (ribosomal RNA) synthesis and ribosome assembly? Where do they go afterwards?

Answer 8

Nucleolus in the nucleus

assembled ribosomal subunits are transported out of nucleus to be assembled as functional ribosomes

Question 9

Two types of chromatin and their differences:

Answer 9

Heterochromatin: less active in gene transcription
Euchromatin: active in gene transcription

Question 10

3 Functions of golgi apparatus

Answer 10

1. Modification and packaging of proteins
2. Formation of lysosomes and secretory vesicles
3. Recycling of cell membrane

Question 11

3 Major types of cytoskeletons and their functions

Answer 11

1. Microfilament/Actin - alteration of cell shape, movement (e.g. cell crawling)
2. Intermediate filament - withstand physical force -> structural maintenance
3. Microbtubules - fixation of cell nucleus with actin and intermediate filaments, transportation of organelles/proteins attached to it

Question 12

What are the 2 ends of microtubules?

Answer 12

+ end: undergoing polymerization

- end: undergoing depolymerization

Question 13

2 Types of motor proteins attached to microtubules?

Answer 13

1. kinesins: move towards + end

2. dyneins: move towards - end

Question 14

6 main types of intermediate filaments

Answer 14

1. Vimentin - fibroblasts
2. Glial filaments - glial cells
3. Cytokeratin - epithelial cells
4. Desmin - muscle cells
5. Neurofilament - neurons
6. Nuclear lamin - inner nuclear membrane