Post on 17-Aug-2020
Chapter 10
Cell Growth and Division
Cell Growth
A. Limits to Cell Growth
1. Two main reasons why cells divide:
a. Demands on DNA as the cell get too large
Cell Growth
b. Moving nutrients and waste across the cell membrane
2. DNA “overload”
a. The DNA in a small cell is able to meet the cell’s needs
Cell Growth
b. A larger cell does not get information fast enough to survive.
3. Exchanging materials
a. Food, oxygen, and water enter and waste exits through the cell membrane.
Cell Growth
b. The rate at which this happens depends on the surface area of the cell
c. The rate at which food and oxygen are used and waste produced depends on the cell’s volume
Cell Growth
4. Ratio of Surface area to volume
a. Surface area of a cube = L x W x # of sides
Example #1
Example #2
Cell Growth
b. Volume = L x W x H
c. Volume increases faster than surface area
Example #1
Example #2
Surface area to Volume examples
Cell Growth
B. Division of the cell
1. Cell division – process by which a cell divides into two new daughter cells.
Cell Growth
a. Cell replicates its DNA so each daughter cell gets a copy
b. Allows for efficient exchange of materials with the environment.
Cell Division
A. Cell Division
1. Prokaryotes
a. DNA replicates
b. Cell separates the contents into two
Cell Division
2. Eukaryotes
a. Mitosis – first stage, division of the cell nucleus
b. Cytokinesis – second stage, division of cytoplasm
Cell Division
B. Chromosomes
1. Chromosomes are copied before the cell can divide
2. Chromatid – identical copies of each chromosome
a. When the cell divides one chromatid goes to each new cell
Cell Division
3. Centromere – area where the chromatids are attached.
Cell Division
C. The Cell Cycle
1. Interphase – period of growth in between the cell dividing.
Cell Division
2. Cell cycle – series of events that cells go through as they grow and divide.
a. Four phases – G1, S, G2, M
Cell Division
D. Events of the Cell Cycle
1. Interphase – G1, S, G2a. G1 – Cells do most of their growing, synthesize new proteins and organelles.
Cell Division
b. S – chromosomes are replicated, synthesis of DNA, proteins associated with chromosomes are synthesized.
Cell Division
c. G2 – Organelles and molecules required for cell division are produced.
E. Mitosis – prophase, metaphase, anaphase, telophase
Cell Division
1. Prophase – 1st and longest phase of Mitosis
a. Chromosomes become visible.
b. Centrioles separate and go on opposite sides of the nucleus.
Cell Division
c. Spindle – fanlike microtubule structure that helps separate chromosomes
d. Chromosomes attach to spindles.
Cell Division
e. Plants do not have centrioles
f. Nucleolus disappears
g. Nuclear membrane breaks down.
Cell Division
2. Metaphase – 2nd phase
a. Chromosomes line up down the center of the cell
b. Microtubules connect the centromere to the spindles
Cell Division
3. Anaphase – 3rd phase
a. Centromere joining the sister chromatids splits
b. Chromosomes continue to move until they are separated near the poles of the spindles
Cell Division
c. Anaphase ends when the chromosomes stop moving.
Cell Division
4. Telophase – 4th phase
a. Chromosomes unravel
Cell Division
b. Nuclear membrane re-forms around each cluster of chromosomes
c. Spindles break apart
d. Nucleolus becomes visible in each daughter nucleus
Cell Division
F. Cytokinesis
1. Usually occurs at the same time as telophase
2. Animals
a. Cell membrane is drawn inward and pinched off into nearly equal parts.
Cell Division
b. Each part contains its own nucleus and organelles
3. Plants
a. Cell plate forms the nuclei
b. Cell plate develops into the cell wall
Regulating the Cell Cycle
A. Controls on cell division
1. Cell continue to grow until they come in contact with other cells
a. Example: cut in the skin
Regulating the Cell Cycle
B. Cell Cycle Regulators
1. Cyclin – protein that regulates the timing of the cell cycle in eukaryotic cells
Regulating the Cell Cycle
C. Uncontrolled Cell Growth
1. Cancer – disorder in which some of the body’s cells lose the ability to control growth
Regulating the Cell Cycle
a. Cancer cells do not respond to the signals that regulate the growth of most cells
b. Divide uncontrollably and form masses of cells called tumors
Regulating the Cell Cycle
c. Cancer cells may break off and spread through the body
2. Defect in gene p53
a. Normally halts the cell cycle until all chromosomes have been properly replicated