Cell Growth and Division CHAPTER 10 EQ Why do cells grow and divide?
DID YOU KNOW THAT The adult human body produces roughly 2 TRILLION cells every day.
WHY DO CELLS REPRODUCE? So that the organism can grow and develop As multicellular organisms grow larger, its cells reproduce and increase in number.
WHY DO CELLS REPRODUCE? Replacement of dead/damaged cells To prevent cell overload
CELL MEMBRANE OVERLOAD Cell size is limited by the cell membrane (surface area) Everything must enter and leave through the cell membrane. Compared to smaller cells, larger cells must take in more nutrients, process (break down) them, and get rid of more waste. Too large = TRAFFIC JAM!
What does the work of cells? What provides the instructions for proteins? DNA Larger cells require more proteins! DNA OVERLOAD Proteins If cell get too large, DNA cannot be copied fast enough to make proteins.
DNA OVERLOAD Gene a unit of heredity that consists of DNA that codes for a protein The activity of the cell is directed by the DNA because it contains the instructions for making proteins.
CHROMOSOMES OR CHROMATIN??? Chromatin loose and stringy DNA Most of the time DNA exists as chromatin because it is easier to copy the instructions for the proteins when loose.
CHROMOSOMES OR CHROMATIN??? Chromosome DNA tightly coiled (wrapped) around proteins called histones When the cell gets ready to reproduce, the chromatin condenses into chromosomes because it is easier to move the chromosomes when they are packed up.
CHROMOSOMES OR CHROMATIN??? What form is the DNA in when the cell is dividing? Chromosome What form is the DNA in when it is being used to make proteins? Chromatin
CHROMOSOME STRUCTURE Chromatid one of the two strands of a duplicated chromosome A single long molecule of DNA Sister chromatids identical chromosome pairs that are still connected together Centromere the region of the chromosome that holds the sister chromatids together during cell division sister chromatids
CHROMOSOME STRUCTURE When sister chromatids are connected, they are considered one chromosome. When sister chromatids are separated during cell division (mitosis), they are considered two individual chromosomes.
PREPARING FOR CELL DIVISION Recall All cells are produced by the division of preexisting cells. The parent cell must give each daughter cell all the equipment it needs to survive. Organelles and DNA
PROKARYOTIC REPRODUCTION Once a bacterium has doubled in size, the cell will divide. Prokaryotes copy the DNA and divide the cytoplasm. Process called binary fission
CELLSALIVE.COM CELLS ALIVE - REVIEW Under the first box Interactive Cell Models Click on PLANT/ANIMAL CELL Click START THE ANIMATION (red box). Follow the directions on the worksheet. Answer the questions on notebook paper (answers only).
THE EUKARYOTIC CELL CYCLE Ch. 10 Sec. 2 EQ How does the cell prepare for division?
Cell cycle a repeating sequence of cellular growth and division during the life of the cell. EUKARYOTIC CELL CYCLE
The cell is not dividing INTERPHASE The cell is growing and preparing to divide How long does interphase last? The majority of the cell s life Skin cells short interphase Nerve cells most of life (most of your life)
Divided into 3 parts: G 1 Phase growth S Phase DNA synthesis Synthesis to make G 2 Phase Growth and preparation for division INTERPHASE
CELL DIVISION Two Processes: Mitosis and Cytokinesis During these phases, the cell s DNA and cytoplasm divide Cytoplasm includes the fluid and organelles
G 1 PHASE Carries out normal cell activities Cell grows by building more organelles DNA exists as chromatin so that it can be used to make proteins Most of a cell s life is spent in this phase Cells that do not divide remain in this phase (G 0 ) Brain cells
S (SYNTHESIS) PHASE DNA replicates (gets copied). At the end of S, the nucleus holds twice as much DNA DNA now exists as sister chromatids that are attached at the centromere.
G 2 PHASE Cell continues to grow and prepares to divide Special structures (centrioles and microtubules) that help the cell divide are assembled.
Mitosis the process of dividing the nucleus into two daughter nuclei Mitosis is divided into 4 phases: prophase metaphase anaphase telophase MITOSIS At the beginning of mitosis (prophase), the DNA is packaged into chromosomes.
CYTOKINESIS Cytokinesis the process of separating the organelles and the cytoplasm Occurs during telophase of mitosis.
WHERE DO THE NEW CELLS GO? Back to G 1! Start the process again!