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Date: January 14, 2016
Aim #46: Why do cells need to divide?
Do Now: Warm-Up Notebook
Date
Title of Activity
1/14
Surface Area to Volume Ratio
Page #
79
HW:
1) Read Chapter 10-1 (Cell Growth) pages 241-243
2) Quarterly Exam Tuesday 1/26 (periods 1 & 7) and
Wednesday 1/27 (period 5)
3) Plant Packet due Monday, February 1st!!! (follow
calendar of deadlines)
Aim #46: Why do cells need to divide?
Compare the size of these organisms
Vs.
Vs.
1) Do these organisms have different size cells?
No, the cells of a large organism are
the same size of a small organism.
2) How do organisms get so big?
Cell
Division
3) Why do cells divide rather than grow in size?
XX
XX
XX
XX
XX
XX
XX
XX
+
XX
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DNA “Overload”
Small Town
DNA Library
The larger the cell, the greater the
demands on the DNA library. Eventually,
the cell’s DNA would no longer be able
to serve the increasing needs of the
growing cell.
City
4) Exchange of Materials
What part of the cell is responsible for the
exchange of materials in and out of the cell?
Cell Membrane
The rate at which particles are able to move across the cell
membrane depends on the surface area of the cell
(the amount of the cell surface exposed to the environment).
SA
Rate of Exchange
5) Surface Area
Small particles have a relatively larger surface area than
large particles.
Why?
What will melt first?
The smaller chips
have more surface
area.
Vs.
Ice Cube
Ice Chips
Smaller cells have more surface area
and can exchange materials across
membrane more efficiently.
6) What is Cell Division?
The process by which
a cell divides into
2 new daughter cells.
7) What happens to chromosomes
before a cell divides?
Replication is the
The chromosomes are replicated process by which DNA
before a cell divides.
makes a copy of itself
9) Why is it beneficial for daughter cells to
be smaller?
Smaller size of daughter cells increases
the surface area and increases rate of
exchange of materials across the
membrane.
Chromosomes
What are chromosomes made
up of?
DNA and Protein
The chromosomes are replicated
before a cell divides.
Centromere
Chromatids
Chromosome
Replication
Chromosome
2 Chromatids
+ Centromere
When do cells divide?
Organism Growth
Cells at the root tips divide very rapidly
When do cells divide?
Repair
12) What tissues in our body need
to undergo a lot of cell division?
Skin
Stomach
Why?
Bone
The cells of these tissues are
constantly growing or repairing
themselves.
Cell Cycle
1) G1 Phase- Cells increase in size and
synthesize new proteins and organelles.
2) S Phase- DNA (chromosomes) are
replicated.
3) G2 Phase- Many of the molecules and
organelles for cell division are produced.
4) M Phase- the cell undergoes cell division.
Does anybody know what the “M” stands for?
Mitosis
Chromosomes
Mitosis Images
Spindle Fibers
Mitosis is the process that divides the cell’s nucleus into two,
each with a complete set of genetic material from the parent cell.