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 (G2) • More growth• Another check

point

1.Gap 1 (G1) - 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 Type Approx. Life

Span

Skin Cell 2 weeks

Red Blood Cell 4 months

Liver Cell 300-500 days

Intestine – internal lining

4-5 days

Intestine – muscle and other tissue

16 years

Nerve cell As 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” (G1, S, G2) 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 cycleEx. Growth factors/hormonesEx. 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 oxygenMuscle 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