Chapter 2 (Part 3): The Cell: Bascic Unit of Structure and Function (Cell Life Cycle)

Life Cycle of the Cell

It has 2 PHASES: INTERPHASE & MITOTIC PHASE

Interphase

time between divisions

• Maintenance (resting) phase

• Normal metabolic activities

• May prepare for a future cell division

Mitotic phase

division for growth or cell replacement

• Division produces two identical daughter cells

Interphase

Most cells spend majority of their lives in in this phase

There are three stages: G1, S, G2

G1 Phase

Cells grow, produce organelles and proteins

Near end of this, cells replicate centrioles for future division

• Nondividing cells (e.g., neurons) never finish this phase- they remain arrested in G0

S Phase

“Synthesis” phase where DNA replicates in preparation for cell division

G2 Phase

Centriole replication is completed

Organelles and enzymes needed for cell division are produced

Mitotic (M) Phase

produces two daughter cells that are genetically identical to the original (parent) cell

Two events occur:

• MITOSIS (PMAT): Division of the NUCLEUS

• CYTOKINESIS: Division of the CYTOPLASM

Stages of Mitosis (P-M-A-T)

Prophase, Metaphase, Anaphase, Telophase

Prophase

“before”

Chromatic supercoils→ forming chromosomes

Duplicate, identical sister chromatids are joined at crentromere

Elongated microtubules called spindle fibers grow from each centriole

The end of is marked by dissolution of nuclear envelope

Metaphase

M-Middle

Chromosomes line up along equatorial plate

Spindle fibers attach to centromeres of chromosomes, and form an oval structure called the mitotic spindle

Anaphase

A-Apart

Spindle fibers pull sister chromatids apart to opposide ends of the dividing cell

Telophase

NUCLEAR ENVELOPE form around each set of chromosomes

Chromosomes begin to UNCOIL and mitotic spindle disapears

CLEAVAGE FURROW (indentation) appears as cytoplasm divides