Transcript Cell Size Limitations

Cell Growth
and
Reproduction
Cell Size Limitations
Cell Size Limitations
 Although it is the smallest
unit of life, a cell still has all
of the characteristics of life. A
cell is able to grow, but it is
limited in how big it can grow
because of the necessary
functions it carries
out…Remember organelles???
Cell Size Limitations

The plasma membrane lets nutrients
into the cell and allows wastes to leave.
Inside the cell, nutrients and wastes
move by diffusion. Diffusion limits cell
size because it is a fast and efficient
process only over short distances.
Cell Size Limitations

Remember, a cell has a lot of cell
parts or organelles to perform
specialized functions. In order for
them to work together quickly and
efficiently, they need to be able to
transport things VERY QUICKLY
therefore they have to be VERY small.
Let’s take a look at our example…
Cell Size Limitations
Cell Size Limitations

Because a cell’s size can slow down
the rate of diffusion, cells have to
have a way of limiting their growth.
Cells divide before they become too
big and therefore unable to function
well:

The cell would either starve to death or
be poisoned from the buildup of waste
products.
Why Divide???

Cells divide in organisms for:
1.
2.
3.
Cell repair
Cell replacement
Growth (lengthening of bones, etc)
Cell Reproduction

When cells divide, two new cells are
produced from one cell.
Remember the cell theory?

Part 3 of the cell theory stated that all
cells come from pre-existing cells.
Cell Reproduction
-
Cell Reproduction, or cell division is
the process by which new cells are
produced from one cell.
- Cell division results in two cells that
are identical to the original, called a
parent cell. The two new cells are
called the daughter cells. When exact
copies are made of “body” (not
sperm or egg) cells, this is called
MITOSIS.
Cell Reproduction-Important Structures

Organisms could not grow or function
properly if the genetic material encoded
in DNA was not passed from cell to cell.
So when cells reproduce by dividing, they
also pass along their DNA.
But how???
Cell Reproduction-Important Structures

Chromosome: the carrier of the genetic material
that is copied and passed from generation to
generation of cells; formed during cell division, it is
only seen right before and right after cell division.
*It has to be accurate (mistakes =
mutations)
*It is a rod-shaped structure made
of tightly coiled DNA and protein
Cell Reproduction-Important Structures

Chromatin: long strands of DNA coiled
in a ball in the nucleus

for most of a cell’s lifetime, chromosomes are
found in this form (looks like Ramen Noodles)
Cell Reproduction-Important Structures

Chromatid: half of the chromosome
(individual sides).

each part is called a sister chromatid
Cell Reproduction-Important Structures

Centromere: a part of the chromosome
that holds sister chromatids together;
helps move the chromosome during cell
division
Centromere
Sister
chromatids
Chromosome
Supercoil
within
chromosome
Continued
coiling within
supercoil
Histone
DNA
Cell Reproduction-Important Structures
Chromosome
centromere
sister chromatids
The Cell Cycle (in Eukaryotes)


The cell cycle is the sequence of growth
and division of a cell. Cell division is
ONE stage. A cell will divide many times
in its lifetime before it dies and is
replaced by a new cell.
There are three stages of the cell cycle:
1. The time BETWEEN cell divisions is
called interphase.
2. The time OF cell division is called
mitosis.
3. When the cytoplasm divides and you
officially have 2 new cells, it is called
cytokinesis.
The Cell Cycle
Growth
Division
2 New Cells
The Cell Cycle (in Eukaryotes)
IPeedMadlyAtTheCrapper-
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
The cell cycle and Mitosis (in Eukaryotes)
Cell division occurs in a series of
stages, or phases.
The cell cycle and Mitosis (in Eukaryotes)
1st: Interphase
Copied
Chromatin
Sister chromosome
Centromere
***Interphase is the longest and busiest
phase of the cell cycle.
Why do you think chromosomes are copied before
cell division happens?
The cell cycle and Mitosis (in Eukaryotes)
2nd: Prophase
Mitosis
Centrioles
Spindle fibers: pull apart the
sister chromatids.
spindle fibers
What happens:
Chromatin condenses to form chromosomes so this
is where chromosomes appear.
The cell cycle and Mitosis (in Eukaryotes)
3rd: Metaphase
spindles
Chromatids
What happens:
The chromosomes line up in the middle of the cell.
The cell cycle and Mitosis (in Eukaryotes)
4th: Anaphase
Separate
Opposite
What happens:
Centromeres split and sister chromatids are pulled
apart to the opposite sides of the cell.
The cell cycle and Mitosis (in Eukaryotes)
5th: Telophase
Nuclei
Threads
Rods
Mitosis
What happens:
Two new nuclei are formed and a double membrane
begins to form around them.
The cell cycle and Mitosis (in Eukaryotes)
6th: Cytokinesis
Daughter
Nucleus
Chromosomes
What happens:
The cell’s cytoplasm divides and separates into two
new identical cells.
Mitosis in a Plant & Animal Cell
CELL PLATE
CLEAVAGE
The Results of Mitosis
= Organization
Cells working
together for
the same
function are
called tissues
Similar
tissues
will form
an organ
Several organs
working together
make up an
organ system
The results of mitosis: Cancer
• Cancer is cell reproduction gone wrong:
- It occurs when a cell loses control of its
division and starts making cells even if they are
not needed
• Cancer can be caused by 3 major things:
1. UV radiation & radiation (too much sun,
radiation exposure)
2. Environmental influences (ex. air pollution,
smoking)
3. Viruses (a viral infection can damage genes)
Cancer Prevention
• Diets low in fat and high in fiber
• Daily exercise
• Not using tobacco
Question 1
The structures in the cell nucleus that contain
DNA are __________.
A. centromeres
B. chromosomes
C. genes
D. chlorophylls
Question 2
Look at the diagram and identify the stage of
mitosis that is depicted.
Centromere
Sister
chromatids
A. prophase
C. anaphase
B. metaphase
D. telophase
Question 3
What is the process by which a cell's cytoplasm
divides?
A. cytokinesis
B. telekinesis
C. meiosis
D. mitosis
Question 4
What is the name of the object that glues/holds
sister chromatids together?
A. centrioles
B. centromeres
C. tissues
D. cell cycles
Question 5
Magnification of a plant cell reveals centromeres
that have split and sister chromatids being pulled
to opposite poles of the cell. This cell is in which
phase of mitosis?
A. prophase
B. metaphase
C. anaphase
D. telophase
Question 6
Which phase of mitosis is depicted in this
diagram?
Spindle Fibers
Doubled
chromosome
Disappearing
nuclear envelope
A. prophase
C. anaphase
B. metaphase
D. telophase
Question 7
What is the term used for the period of the cell
cycle represented by the red arrow in this graph?
A. prophase
B. metaphase
C. centrophase
D. interphase
DNA synthesis
and replication
Centrioles
replicate; cell
prepares for
division
Rapid growth
and metabolic
activity
Mitosis
Cytokinesis
Question 8
What phase of mitosis
is shown in this
picture?
A. Prophase
B. Metaphase
C. Interphase
D. Telophase
Question 9
What process is being
represented by the
blue arrow? (the
pinching in of the cell
membrane)
A. Pinching
B. Cleavage
C. Cell Plate
D. Cheeking
Question 10
• What is the sentence we say to remember
the phases in order? Please write out the
sentence and place the correct phase next
to it.