Cell Cycle

Cell cycle

growth and division of a cell that is tightly controlled

Aspects at which cells divides

• developmental stage

• nutritional status

• metabolic status

• wound response

• dna damage

• pathogenesis (disease developing)

• senescence (deterioration with age)

What are the 4 phases of Cell Cycle

G1,S,G2 (interphase) and M (mitosis)

What happens in G1

organelle replicate, cell grow in size, nutrients accumulate for DNA replication

What happens in S phase

chromosomes replicate and centrosome duplicate

What happens in G2 phase

organelle biosynthesis and cell growth

What happens in G0 phase

permanent state and they will never divide again

What happens in M phase

Mitosis and cytokinesis

What are the name of stages in mitosis

Prophase

Prometaphase

Metaphase

Anaphase

Telophase

What happens in each of the steps of Mitosis

• Prophase: Chromosomes condense, transcription stops, spindle apparatus begins to form

• Prometaphase: Nuclear envelope breaks down, microtubules contact to chromosome at kinetochores

• Metaphase: Chromosomes line up in middle of cell, pulled by microtubules

• Anaphase: Sister chromatids separate, pulled to opposite poles of cell

• Telophase: Chromosome decondenses, nuclear envelope reforms

What happens in cytokinesis

Cytoplasm divides, 2 daughter cells form

How does cytoplasm differ in animals and plants

Animals: A ring of actin and myosin filaments contracts inside the cell membrane, causing it to pinch inward in a cleavage furrow

Plants: Vesicles are transported to the middle of the dividing cell along microtubules. These vesicles fuse to form a cell plate

What has to proceed chromosomal segregation during mitosis

Chromosomal condensation

Nuclear envelope breakdown

Centrosome migration to distant parts of the cell

Spindle apparatus formation

What are the 3 major checkpoints

G1, G2, M aka G1/S, G2/M

What happens in each of the major cell cycle checkpoints to pass

G1:cell size is adequate, nutrients are sufficient, organelles replicate, growth signals are present, DNA is undamaged.

G2: chromosomes have replicated successfully, DNA is undamaged

M:all chromosomes are attached to spindle apparatus

What are at the core of checkpoint control

cyclin dependent kkinases

explain what happens to CDK in cycle

1) cycle binds to CDK to control progression through cell cycle

2) CDK phosphorylates target proteins involved in promoting cell division

Thus key feature of cell cycle is control of cyclin accumulation

retinoblastoma protein (Rb) does what to checkpoints? How do Cyclin CDKs stop this

• locks the Regulatory transcription factors E2F and DP(drive transcription gene for S phase) in an inactive state, preventing them from activating S-phase transcription.

• Cyclin-CDK phosphorylates RB, inactivating the RB protein

What is MPF

Mitosis promoting factor , and it drives the cell trough the G2/M checkpoint(mitosis),controlled by cyclin accumulation.

How does MPF drive mitosis

by triggering the events that occur during mitosis through protein phosphorylation

Why do we need targeted cyclin degradation

regulating the cell cycle and preventing uncontrolled cell growth, particularly relevant in cancer.

A common and permanent way to inactivate proteins is

proteolytic degradation

The proteasome

The proteasome is a large protein complex that degrades unneeded or damaged proteins within cells

Steps in proteasome with ubiquition

E1: bound to ubiquitin

E2:grabsubiquitin fromE1;bindstoactivatedE3

E3: grabs a specific substrate (cyclin); E2 transfers ubiquitin to substrate

Centromere

attachment point for spindle fibers during cell division

Centrosome

An organelle essential for microtubule formation and cell division

spindle apparatus

a structure composed of microtubules

chromosome

structure within a cell nucleus that carries genetic information in the form of DNA

ubiquitin

acts as a molecular tag

Ubiquitin ligase

a cellular pathway responsible for degrading proteins