CELL GROWTH & DIVISION

Chapter 10 & 11.4

LIMITS TO CELL SIZE

• INFORMATION OVERLOAD

• AS A CELL INCREASES IN SIZE IT DOESN’T MAKE MORE DNA

• IF A CELL GROWS TOO LARGE, NEW ORGANELLES CAN’T

GET THE INSTRUCTIONS THEY NEED TO FUNCTION

LIMITS TO CELL SIZE

• EXCHANGING

MATERIALS • MATERIALS GO IN AND OUT

DEPENDING ON SURFACE AREA

• FOOD & OXYGEN IS USED UP DEPENDING ON VOLUME

• AS A CELL GETS LARGER, VOLUME INCREASES MUCH MORE RAPIDLY THAN SURFACE AREA. • IF A CELL BECOMES TOO

BIG, IT CANNOT EXCHANGE MATERIALS ACROSS THE MEMBRANE FAST ENOUGH.

LIMITS TO CELL SIZE

• DIVISION OF THE CELL

• BEFORE A CELL

BECOMES TOO

LARGE, IT DIVIDES

FORMING TWO

“DAUGHTER” CELLS

• PROCESS IS CALLED

CELL DIVISION

CELL DIVISION

• BEFORE A CELL CAN DIVIDE, IT MUST REPLICATE

THE DNA. THE DNA IS THEN PACKAGED INTO

CHROMOSOMES.

• PROKARYOTIC CHROMOSOMES EXIST AS A

SINGLE, CIRCULAR LOOP

• EUKARYOTES HAVE MULTIPLE CHROMOSOMES • DURING THE INTERPHASE PART OF THE CELL CYCLE,

THE CHROMOSOMES EXIST AS CHROMATIN

• WHEN THE CELL IS READY TO DIVIDE, THE

CHROMOSOMES CONDENSE INTO SUPERCOILED

CHROMATIN.

CELL DIVISION

EUKARYOTIC CELL CYCLE

• LENGTH OF THE CELL

CYCLE VARIES DEPENDING

ON THE TYPE OF CELL

• ALL CELLS GO THROUGH

FOUR PHASES

• G1 – CELL GROWTH

• S – DNA REPLICATION

• G2 – PREPARATION FOR

DIVISION

• M – CELL DIVISION

MITOSIS

• MITOSIS IS DIVIDED INTO 4 STAGES IN WHICH THE

DUPLICATED CHROMOSOMES LINE UP IN THE MIDDLE OF

THE CELL.

• EACH COPY IS PULLED TO OPPOSITE ENDS OF THE CELL.

DRAW

CYTOKINESIS

• CYTOKINESIS IS THE PROCESS OF CELL DIVISION

• IN ANIMAL CELLS, THE CELL MEMBRANE PINCHES INWARD

UNTIL TWO NEARLY IDENTICAL CELLS ARE FORMED.

• IN PLANT CELLS, A CELL PLATE FORMS IN THE MIDDLE OF

THE LARGE CELL, DIVIDING IT IN TWO.

CHROMOSOME NUMBER

• HOW MANY SETS OF GENES ARE FOUND IN MOST ADULT

ORGANISMS?

• EACH ORGANISM INHERITS ONE CHROMOSOME FROM

ONE PARENT AND ONE CHROMOSOME FROM THE OTHER.

CHROMOSOME NUMBER

• HUMANS HAVE 23 PAIRS OF CHROMOSOMES, FRUIT

FLIES HAVE 4 PAIRS

• HOMOLOGOUS = CHROMOSOMES THAT EACH HAVE

A CORRESPONDING CHROMOSOME FROM THE

OPPOSITE-SEX PARENT

CHROMOSOME NUMBER

• DIPLOID (2N) = TWO SETS OF CHROMOSOMES

• ALMOST ALL CELLS ARE DIPLOID

• CELLS THAT DIVIDE BY MITOSIS ARE DIPLOID

• HAPLOID (N) = ONE SET OF CHROMOSOMES

• ONLY GAMETES ARE HAPLOID

• WHAT ARE GAMETES?

MEIOSIS

• MEIOSIS = PROCESS OF

FORMING SEX CELLS,

“REDUCTION AND DIVISION”

• BEGIN WITH DIPLOID CELLS (2N)

• CHROMOSOMES HAVE ALREADY BEEN REPLICATED

• EACH CHROMOSOME PAIRS UP WITH ITS HOMOLOGOUS CHROMOSOME

MEIOSIS

• AT THE BEGINNING OF MEIOSIS, CHROMATIDS CROSS

OVER ONE ANOTHER, EXCHANGING GENETIC INFO.

(CROSSING-OVER)

MEIOSIS

• AFTER CROSSING OVER, THE HOMOLOGOUS

CHROMOSOMES SEPARATE MOVING TO

OPPOSITE ENDS OF THE CELL. THEN THE CELL

DIVIDES PRODUCING 2 HAPLOID CELLS.

• THE CELLS WILL DIVIDE ONCE AGAIN,

PRODUCING 4 HAPLOID CELLS.

MEIOSIS

MITOSIS VS MEIOSIS

CELL REGULATION

• CONTROLS ON CELL DIVISION

• WHEN CELLS COME INTO CONTACT WITH

OTHER CELLS THEY RESPOND BY NOT

GROWING

• CONTROLS ON CELL GROWTH AND CELL

DIVISION CAN BE TURNED ON AND OFF

CELL REGULATION

• WITH AN INJURY, CELLS AT EDGE OF INJURY ARE

STIMULATED TO DIVIDE RAPIDLY TO BEGIN

HEALING

CELL REGULATION

• CELL CYCLE REGULATORS

• REGULATORS = RESPOND TO EVENTS TO SPEED UP OR SLOW DOWN CELL CYCLE

• CYCLINS = PROTEINS THAT CONTROL THE TIMING OF THE CELL CYCLE IN EUKARYOTIC CELLS

CELL REGULATION • GROWTH FACTORS – STIMULATE GROWTH & DIVISION

IMPORTANT IN EMBRYONIC CELLS AND WOUND

HEALING

• UNCONTROLLED CELL GROWTH

• CANCER = A DISEASE OF THE CELL CYCLE

• CANCER CELLS DO NOT RESPOND TO SIGNALS THAT

REGULATE GROWTH OF MOST CELLS

• TUMORS = MASSES OF CELLS THAT DAMAGE THE

SURROUNDING TISSUE

• WHEN A CANCER METASTASIZES, CELLS HAVE BROKEN OFF

THE TUMOR AND TRAVELED TO OTHER PARTS OF THE BODY

• KNOWN CAUSES – SMOKING, TOBACCO, RADIATION

EXPOSURE, VIRAL INFECTION

STEM CELLS

• 3-5 AFTER FERTILIZATION, A HUMAN EMBRYO IS A

MASS OF CELLS CALLED STEM CELLS

• STEM CELLS ARE PLURIPOTENT = THEY ARE NOT

SPECIALIZED AND HAVE THE ABILITY TO

DIFFERENTIATE (DEVELOP INTO ANY SPECIALIZED

CELL, EX: NERVE CELL)

STEM CELLS

• THREE CURRENT SOURCES:

• ADULT STEM CELLS (BONE MARROW, HEART, BRAIN, LUNGS)

• EMBRYONIC STEM CELLS (DISCARDED EMBRYOS FROM FERTILITY TREATMENT)

• UMBILICAL CORD BLOOD

• POTENTIAL TREATMENTS

• ALZHEIMER’S DISEASE

• HEART DISEASE

• LIMB REGENERATION

• ORGAN TRANSPLANTS