Download Cell Size Limitations

Cell
Reproduction
EQ: Why do cells double their DNA
before they divide?
Remember the Cell Theory…
All living things are made of cells.
Cells are the basic unit of structure and
function.
All new cells come from pre-existing
cells.
Let’s figure out how that
happens!
Let’s start with the basics…
Every cell in an organism must have
the same number of chromosomes.
(Except sex cells)
If a cell doesn’t, it will not be able to
function properly.
Human body cells have 46 (2n or
diploid) chromosomes
More basics…
Before a cell divides, the DNA must
replicate or make a copy of itself…
46 chromosomes
46 chromosomes
46 chromosomes
…so each new cell will have the correct
number of chromosomes (DNA)
Cell Reproduction
 The process of producing new cells from
existing cells
 This is asexual reproduction (only one
parent cell involved)
 New cells are genetically identical to
parent cell
Parent cell
Daughter cells
Parent cell
Daughter cells
Why Do Cells Divide?
1) Cell is too big
2) To replace damaged or
dead cells
3) For growth and development
(embryo)
How can a cell be too
big? Look at the 3 cells below. Which one
looks like it would be most efficient at
transporting nutrients within and
removing waste from the cell?
Cell Size Limitations
Ratio of surface area to volume
Surface area is the area covered by the cell
membrane.
Volume is the space taken up by the inner contents
of the cell.
As the cell gets bigger, its volume increases faster
than its surface area.
Cells with a larger surface area: volume ratios
(smaller cell) can sustain themselves more easily.
Cell Size Limitations
Cell Reproduction through
Mitosis: For Eukaryotes Only!
Advantages are….
Replacement
Speed
Preserving desirable characteristics
The Cell Cycle
• A series of events that takes place during
the life of a eukaryotic cell
Interphase
The Cell Cycle
• Interphase = G1, S, G2
• G1 – (Gap 1) Growth and
development
• S – (synthesis) DNA
Replication
• G2 – (Gap 2) Growth and
development, prepare for
mitosis
• G0 – Resting phase
Interphase
G0
The Cell Cycle
• A series of events that
takes place during the life
of a eukaryotic cell
• Most of the cell cycle is
called Interphase, a time
of growth and development
• The “M” phase is Mitosis
& Cytokinesis, a time
when the nucleus and cell
divides
Interphase