Download Cell Growth and Reproduction

Cell Growth and
Reproduction
Biology Agriculture
Cell Growth
 All cells come in different sizes and
shapes.
 Diffusion in fast and effective over short
distances.
 It become slow and inefficient over long
distances.
 If a cell and a mitochondria 20cm in diameter –
it would take months before it would receive
molecules that entered the cell membrane.
Cell Growth
 Surface area-to-volume ratio
 Area: the surface included in a set of lines.
 Volume: space occupied as measured in
cubic inches.
 Ratio: the relationship in quantity, amount, or
size between two or more things.
Cell Growth
 Due to the surface area-to-volume ratio
cells divide before they become to large.
 DNA is what directs the cell when it is
becoming to large.
Cell Reproduction
 Cell division in necessary to form
multi-cellular organisms.
 Asexual Reproduction:
 Production of offspring from one parent cell.
 Sexual Reproduction:
 Formation of offspring from the union of two
gamete cells .
Asexual Reproduction
 Steps:
 Chromosomes duplicate (called
replication)
 Both attach to a site located in the cell
 They are forced apart.
 Cell membrane constricts them till they
separate.
Asexual Reproduction
 Some examples include:
 Strawberry Runners
 Potatoes
 Star Fish
Sexual Reproduction
 Results from the joining of two highly
specialized cells.
 Sperm Cells
 Ovum Cells or Egg Cell
 Fertilization:
 Sperm cell and ovum combine to form a
Zygote.
Chromosomes
 Chromatids:
 Long strands of DNA.
 Chromosomes:
 Made of two sister chromatids.
 Held together by a centromere
Diploid (2n) Cells
 A cell with two of each kind of
chromosomes are called Diploid Cells.
Haploid (n) Cells
 A cell with one kind of each chromosome
is called a Haploid cell.
Mitosis
 Cells undergo mitosis as they reach their
maximum cell size.
 There are four steps in mitosis:
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Prophase
Metaphase
Anaphase
Telophase
Mitosis:
 Stage 1 – Prophase.
 Chromatids coil up into visible
chromosomes.
 Nucleus Disappears
 Centrioles migrate to the polar ends of
the cell
 Spindle Fibers begin to form.
Mitosis:
 Stage 2 – Metaphase
 Chromosomes become attached to the
spindle fibers by their centromeres.
 They are lined up across the center of
the cell.
Mitosis:
 Stage 3 – Anaphase
 Sister chromatids begin to separate
 Chromatids are pulled apart, and
separate from each other.
Mitosis:
 Stage 4 – Telophase
 New cells prepare for their new
existence.
 Chromosomes uncoil and direct
metabolic activity
 Spindle Fibers break down
 Nucleolus reappears
 Double membrane forms between them
Mitosis
 Cytokinesis
 Animals – Plasma Membrane pinches
in along the equator of the cell.
Mitosis
 Cytokinesis
 Plants - Cell Plate is laid across the
equator.
 Cell walls form around the plate
Results of Mitosis
 As a result,
 Each daughter cell receives and exact
copy of the chromosomes present in the
parent cell.
 They copy their chromosomes during
Interphase.
 They become a diploid cell 2n
 The process can then start over.
Results of Mitosis
 Process that guarantees that genetic
continuity.
 The two new cells formed will carry out
the same functions of the parent cell.
 They will grow and divide just like the
parent cells.
Results of Mitosis
 As a result of cell division we have
groups of cells working together, until
they create and organism, i.e.

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Cells
Tissues
Organs
Organs Systems
Organisms
The Cell Cycle
 Cell Cycle:
 The sequence of growth and division in
the cell.
 A cell goes though two periods:
 A period of growth
 A period of division
The Cell Cycle
Prepare
for cell
division
2 hours
DNA Synthesis
and Replication
10 Hours
INTERPHASE
Rapid Growth and
Metabolic Activity
9 hours
Interphase
 The busiest part of the cell cycle
 Part I: Cell grows and protein
production is high.
 Part II: Cell copies its chromosomes
 Part III: Parts manufactured for cell
division.
The Cell Cycle
 The cell cycle is controlled by;
 Proteins
 Enzymes
 Area – to – Volume Ratio
 Occasionally, cells lose control.
 Cancer, malignant growth resulting from
uncontrolled cell division.
Cancer – A mistake in the
cell cycle!
 Tumors
 Masses of tissue that deprive normal cells of
nutrients.
 Cancer is the second leading cause of
death in the United States, exceeded
only by heart disease.
Meiosis
 Meiosis forms haploid daughter cells
from diploid parent cells.
 Meiosis is divided into two parts;
 Meiosis I
 Meiosis II
Meiosis I
 Synapsis
 Homologous Chromosomes line up
next to each other.
 Forming a structure called a tetrad.
Meiosis I
 Meiosis I is divided into four stages;
 Prophase I
 Metaphase I
 Anaphase I
 Telophase I
Meiosis I
 Prophase I
 Homologous Chromosomes are
formed
 Spindle fibers form
 Tetrads are visible and have lined up
along the equator.
Meiosis I
 Metaphase I
 Each tetrad becomes attached to the
spindle fibers
Meiosis I
 Anaphase I
 Homologous chromosomes are pulled
apart.
 One pair goes to the on polar end while
the other goes to the other end.
Meiosis I
 Telophase I
 Cytokinesis takes place.
 The cell divides.
Meiosis I
 At the end of Meiosis I;
 One chromosome from each parent cell is
present in the daughter cell.
 Meiosis I is a reductive division;
 Reduce the chromosomes from diploid (2n)
to a haploid (n).
Meiosis II
 Each daughter cell produced in
Meiosis I undergoes another
division.
 Meiosis II is very similar to Mitosis
except, it is not proceeded by a
replication of the chromosomes.
Meiosis II
 There are four stages;
 Prophase II
 Metaphase II
 Anaphase II
 Telophase II
Meiosis II
 Resulting in;
 Four daughter cells
 Each daughter cell produced is
haploid.
 Each cell has four chromosomes.
 One from each of the homologous
pairs of parent cells.
Meiosis II
 Prophase II
 New spindle fibers form
chromosomes.
around the
Meiosis II
 Metaphase II
 Chromosomes line up along the
equator.
 Attach the centromere to the spindle
fibers
Meiosis II
 Anaphase II
 The centromere divides and the
chromatids separate.
 Each chromatids becomes it on
chromosomes with their own
centromere.
Meiosis II
 Telophase II
 The nuclear envelope forms
around each set of chromosomes.
 Cell undergoes Cytokinesis.
Meiosis – Why?
 The result;
 Cells used for reproduction
 Sperm Cells
 Ovum Cells