Chapter 5 – Cell Growth and Division

The cell cycle is the regular pattern of growth for cells and has 4 main phases 3.Gap 2 (G 2 ) More growth Another check point 1.Gap 1 (G 1 ) - longest Normal functions Cell increases in size More organelles made 2. Synthesis (S) Synthesizes (makes) more DNA 4.Mitosis (M) Mitosis divided cells nucleus Cytokinesis divides cytoplasm 2 identical daughter cells result

Cells divide at different rates depending on needs Example: Cell TypeApprox. Life Span Skin Cell2 weeks Red Blood Cell4 months Liver Cell days Intestine – internal lining 4-5 days Intestine – muscle and other tissue 16 years Nerve cellAs long as you live

Cell size is limited by 2 main things: DNA, and nutrient/waste movement The cell has to have enough DNA to run the cell Surface area and volume have to work together to get food in and waste out

Chromosome – long continuous thread of DNA Histone – group of proteins Chromatin = chromosome + histone Chromo copied during S phase Chromatid – ½ of duplicated chromo Centromere - holds 2 halves together Telomeres - on end of chromo to keep from attaching

Cell division = dividing to form two “ daughter cells ” Must go through “interphase” (G 1, S, G 2 ) first

3.Anaphase Chromos split up Spindles pull to opposite sides 1.Prophase- longest Chromos condense Nuclear envelope breaks down Centrioles move to sides Spindles show up 2. Metaphase - short Chromos line up Spindle attach to centromeres 4.Telophase New envelopes form at each end Chromos disperse Spindles break up Mitosis is where the cell is actually dividing

last step of cell cycle Cytokinesis = division of cytoplasm Animal cells get “pinched in” Plant cells form a cell plate

Regulating the cell cycle is important External regulators = outside of cell  Speed up/slow down cycle Ex. Growth factors/hormones Ex. Cell-to-cell contact

Ex. Kinases & Cyclins Internal regulators = inside the cell  help double check cell cycle

Apoptosis = programmed cell death Depending on the situation some cells need to die  Their parts usually get recycled

Cancer = uncontrolled cell division forms tumors Benign = usually harmless Malignant = bad HPV

Asexual reproduction is similar to mitosis Ex. Binary fission

Multicellular organisms have lots of specialized cells Blood cells carry oxygen Muscle cells help move Skin cells help prevent infection

Levels of organization in multicellular life 1. Cells 2. Tissues – cells working together

3. Organs – tissues working together 4. Organ system – organs working together