Download The Cell Cycle

Why must cells divide?
MULTICELLULAR ORGANISMS GROW BY MAKING MORE CELLS
WHEN CELLS GET TOO BIG, THEIR MEMBRANES CANNOT
EXCHANGE WASTE AND NUTRIENTS FAST ENOUGH TO KEEP THEM
ALIVE
• DIVISION IS NEEDED FOR GROWTH (INCREASE IN SIZE),
HEALING, AND DEVELOPMENT (CHANGES IN BODY
STRUCTURE)
SOME ORGANISMS USE DIVISION TO REPRODUCE ASEXUALLY
BACTERIAL CELL GROWTH- BINARY
FISSION
• BACTERIAL CELLS DO NOT GROW IN SEPARATE STAGES.
• WHEN THEY HAVE GROWN LARGE ENOUGH, AND COPIED
THEIR DNA, THEY SPLIT THEIR CYTOPLASM IN TWO.
• HTTPS://WWW.YOUTUBE.COM/WATCH?V=DZZFTHKFZSG
• HTTPS://WWW.YOUTUBE.COM/WATCH?V=J3CO48TL8_A
The Cell Cycle
• THE LIFE OF A CELL CAN BE BROKEN DOWN INTO TWO MAJOR
STAGES: INTERPHASE AND CELL DIVISION (M PHASE)
• DURING INTERPHASE, THE CELL PERFORMS NORMAL FUNCTIONS
AND PREPARES FOR DIVISION
• INTERPHASE IS MADE UP OF THREE PHASES:
 G1 – CELL GROWS AND
MAKES MORE ORGANELLES
 S – A SECOND COPY OF THE
CELL’S DNA IS SYNTHESIZED
 G2 – THE CELL GETS READY
FOR DIVISION
The Cell Cycle
• CELL DIVISION (M PHASE) IS MADE UP OF TWO
PARTS:
 MITOSIS – DIVISION OF THE NUCLEUS TO CREATE
TWO IDENTICAL DAUGHTER NUCLEI
 CYTOKINESIS – SPLITTING OF THE MEMBRANE AND
CYTOPLASM TO FORM TWO IDENTICAL CELLS
Regulation of the Cell Cycle
• HEALTHY CELLS GROW, DIE, AND ARE REPLACED IN A
CONTROLLED WAY
• THE CELL CYCLE IS CONTROLLED AT THREE
CHECKPOINTS
• CHECKPOINT FAILURE MAY RESULT IN CANCER – A
DISEASE IN WHICH CELLS DIVIDE RAPIDLY AND
UNCONTROLLABLY
Regulation of the Cell Cycle
• Three checkpoints:
• End of G1 phase
• After G2 phase
• After Mitosis (Cell Division)
• HTTPS://WWW.YOUTUBE.COM/WATCH?V=OCIGJN8UJNQ
• PRE-MITOSIS VIDEO:
HTTPS://WWW.YOUTUBE.COM/WATCH?V=ZZ1G2W1JL7E