how does an organism grow?!. cell cycle/cell reproduction all change is a miracle to contemplate;...
TRANSCRIPT
How does an organism grow?!
Cell Cycle/Cell Reproduction
All Change is a miracle to contemplate; but it is a miracle taking place every second. –Henry David Thoreau
Do cells grow? Yes, but just enough to have double of
what is needed. Organelles, cytoplasm, membrane, etc
All cells are generally the same size. A small plant and a large plant have the
same size cells. The muscle tissue on an elephant and the
muscle tissue of a mouse have the same size cells.
Why do cells have to divide? Because growing too big has
consequences. Becomes less efficient in 3 ways… 1. DNA becomes overworked. 2. Small cells are much easier/faster to
replicate. 3. The main consequence is that it is
much harder to move materials across the cell membrane. Surface Area : Volume
High Surface Area to Volume Ratio
Surface Area/Volume (Look on Test) The smaller the cell is, the greater the
surface area to volume ratio. This means there is more area for materials
to be transported through the membrane. What the cell wants is a higher Surface
Area than the volume.BUT…
Volume increases faster than Surface Area.
Cell Size
Surface Area (length x width x 6)
Volume (length x width x height)
Ratio of Surface Area to Volume
What is the cell cycle? It is the series of events that cells go
through in order to grow and divide.
Called a “cycle” because it is an ongoing/continuous process.
3 Basic Types 1. Cell Division in prokaryotes (Bacteria) 2. Cell Division in eukaryotes for the
purpose of growth and repair. 3. Cell division that produces sex cells
(gametes)
Prokaryotic Cell Division Relatively simple… These cells reproduce through binary
fission. First: the genetic information is copied. Then the cell divides in two. Each new cell receives an exact copy of
the genetic information. These daughter cells are exactly
identical.
Eukaryotic Cell Division 2 distinct part to the Cell Cycle
1. Interphase (Between phase) 2. M Phase (Mitosis and cytokinesis)
Interphase Resting Stage
Looks like the cell is resting.
Majority of time is spent here.
DNA Chromatin
3 phases of Interphase G1 phase: the cell grows &
carries out routine functions. (increase in size)
2. S phase: chromosomes are copied. Critical: because each
daughter cell needs a complete set.
The number of chromosomes in cells is constant within a species.
Humans= 46 chromosomes or 23 pairs
3. G2 phase: cell prepares for nucleus to divide. Cell grows & produces
additional organelles & cytoplasm.
M Phase Mitosis Division of the nucleus to form two
nuclei. Ensures each new cell gets a copy of
every chromosome. Takes the least amount time, but has
the most action.
Mitosis - GeneralChromosomes have replicated & are visible# of centromeres = # of chromosomes
Centromere – area where the chromatids of a chromosome are
attached
Mitosis – General Cont’d
Each daughter cell receives its own copy of the parent cell’s DNA
Occurs in body cells – somatic cells
Cytokinesis Still a part of the M phase…but NOT a part of mitosis! This is the division of the organelles and cytoplasm.
Disruptions in the cell cycle…
We are made up of many kinds of specialized cells. Skin cells, muscle cells, red blood cells,
liver cells, it goes on and on.Cell divide to make other cells, like
themselves. Cells continue to grow until they touch another cell. The cell cycle is controlled by proteins call cyclins.
Continued… Disruptions lead to diseases, such as…
Cancer Causes abnormal cells to form or an unusually large
number of cells to form. If these cells join together into a large mass, it is
called a tumor. Many have a defect in a gene called p53.
The cell cycle can be disrupted when… DNA is not copied correctly. Environmental factors: radiation, tobacco smoke,
other pollutants.
Cancer
Loss of control during the cell cycle can lead to cancer
Cancer cells do not show contact inhibition and they divide uncontrollably
Can result from a single nucleotide change in the DNA!
Cancer Cells YouTube
1. In which phase of the eukaryotic cell cycle is the genetic material duplicated?A. G1 phase C. G2 phase
B. 2nd- S phase D. M phase (MITOSIS)
2. Which two phases of the cell cycle make up cell division?A. G1 & Cytokinesis C. G2 phase & Cytokinesis
B. Interphase & mitosis D. Mitosis & Cytokinesis