The Cell Cycle & Mitosis

Chapter 5

5.1 – The Cell Cycle

• Key Concept:– Cells have distinct phases of growth,

reproduction, and normal functions.

The cell cycle has 4 main stages.• The cell cycle is a regular pattern of

growth, DNA replication, and cell division.

The main stages of the cell cycle are Gap 1, Synthesis, Gap 2, & Mitosis.

• Gap 1 (G1): cell growth and normal functions, copy organelles

• Synthesis (S): copies DNA• Gap 2 (G2): additional growth• Mitosis (M): includes division of the cell

nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)–Mitosis occurs only if the cell is large

enough and the DNA undamaged.

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Cells divide at different rates.• The rate of cell division varies with the need for

that type of cell.

• Some cells are unlikely to divide (in Gap 0/G0 of the cell cycle)– Example: neurons

Cell size is limited.• Volume increases faster than surface

area.– Cells need to stay small to allow

diffusion and osmosis to work efficiently.

• Surface area must allow for adequate exchange of materials.– Cell growth is coordinated with division.– Cells that must be large have unique

shapes.

Stop & Review• ________: cell growth and normal functions, copy organelles• Gap One• __________: copies DNA• Synthesis• _________: additional growth• Gap Two• ________: includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)• M phase (mitosis)

– Mitosis occurs only if the cell is ______ enough and the _____ undamaged.– Large DNAThe rate of cell division varies with the .Need for that type of cell

• Volume increases faster than ___________________.• Surface Area

– Cells need to stay ___________ to allow ___________ and __________ to work efficiently.– Small diffusion osmosis

• ______________________ must allow for adequate exchange of materials.• Surface Area

– Cell growth is coordinated with _____________.– Division– Cells that must be large have unique _____________.shapes

5.2 – Mitosis & Cytokinesis

• Key Concept:– Cells divide during mitosis and

cytokinesis.

Chromosomes condense at the start of mitosis.

• DNA wraps around proteins (histones) that condense it.

• DNA plus proteins is called chromatin.

• One half of a duplicated chromosome is a chromatid.

• Sister chromatids are held together at the centromere.

• Telomeres protect DNA and do not include genes.

Mitosis and cytokinesis produce two genetically identical daughter cells.

• Interphase prepares the cell to divide.

• During interphase, the DNA is duplicated.

Box 1: Interphase

Mitosis divides the cell’s nucleus in four phases.

• Prophase (Box 2)– Chromosomes condense, spindle fibers

form, and the nuclear membrane disappears

Mitosis divides the cell’s nucleus in four phases.

• Metaphase (Box 3)– Chromosomes line up in the middle of

the cell

Mitosis divides the cell’s nucleus in four phases.

• Anaphase (Box 4)– Sister chromatids are pulled apart to

opposite sides of the cell

Mitosis divides the cell’s nucleus in four phases.

• Telophase (Box 5)– Two nuclei form at opposite ends of the

cell, the nuclear membranes reform, and the chromosomes uncoil back into chromatin

Cytokinesis differs in animal and plant cells.

• Cytoplasm separates– Animal cells: membrane

pinches the two new cells apart

– Plant cells: a cell plate (new cell wall) separates the two new cells

Stop & Review

• Chromosomes ____________ at the start of mitosis.• Condense• DNA wraps around proteins (____________) that condense it.• Histones• DNA plus proteins is called ______________.• Chromatin• One half of a duplicated chromosome is a _______________.• Chromatid• Sister chromatids are held together at the ________________.• Centromere• _____________ protect DNA and do not include genes.• Telomere

Stop & Review (cont)• ______________ prepares the cell to divide and is when the DNA is duplicated.• Interphase• _____________ is when chromosomes condense, spindle fibers form, and the nuclear

membrane disappears• Prophase• _______________ is when chromosomes line up in the middle of the cell• Metaphase• _____________ is when sister chromatids are pulled apart to opposite sides of the cell• Anaphase• _____________ is when two nuclei form at opposite ends of the cell, the nuclear membranes

reform, and the chromosomes uncoil back into chromatin• Telophase• __________ is when the cytoplasm separates• Cytokinesis

– ___________ cells: membrane pinches the two new cells apart– Animal – ___________ cells: a cell plate (new cell wall) separates the two new cells– Plant

5.3 – Regulation of the Cell Cycle

• Key Concept:– Cell cycle regulation is necessary for

healthy growth.

Cell division is uncontrolled in cancer.• Cancer cells form disorganized

clumps called tumors.– Benign tumors remain clustered and can

be removed.–Malignant tumors metastasize, or break

away, and can form more tumors.

Apoptosis is programmed cell death.

• Some cells need to grow and divide but other cells need to die.

• Apoptosis is the process of programmed cell death.– Normal feature in healthy organisms– Caused by a cell’s production of self-

destructive enzymes– Occurs during fetal development

(responsible for separation of fingers and toes)

• Cancer cells do not carry out normal cell functions.

• Cancer cells come from normal cells with damage to genes involved in cell-cycle regulation.

• Carcinogens are substances known to cause cancer (they damage those genes)– Chemicals, tobacco smoke, X-rays, UV rays

• Standard cancer treatments typically kill both cancerous and normal, healthy cells.

Stop & Review• Cancer cells form disorganized clumps called

__________________.• Tumors

– _________________ tumors remain clustered and can be removed.

– Benign– _________________ tumors metastasize, or break away, and can

form more tumors.– Malignant

• __________________ is the process of programmed cell death.

• Apoptosis

5.4 – Asexual Reproduction

• Key Concept:–Many organisms reproduce by cell

division.

Binary fission is similar to mitosis.

• Asexual reproduction is the creation of offspring from a single parent.– Binary fission produces

two daughter cells genetically identical to the parent cells.

– Binary fission occurs in prokaryotes.

Some eukaryotes reproduce by mitosis.

• Budding forms a new organism from a small projection growing on the surface of the parent.

• Fragmentation is the splitting of the parent into pieces that each grow into a new organism.

• Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.

Stop & Review• _______________ _______________ is the creation of offspring from a single parent.• Asexual Reproduction• ___________ _______________ is asexual reproduction in prokaryotes and produces

two daughter cells genetically identical to the parent cells.• Binary Fission• Asexual Reproduction In Eukaryotic Organisms• _____________ forms a new organism from a small projection growing on the

surface of the parent.• Budding• __________________ is the splitting of the parent into pieces that each grow into a

new organism.• Fragmentation• ____________ _________________ forms a new plant from the modification of a

stem or underground structure on the parent plant.• Vegetative Reproduction

5.5 – Multicellular Life• Key Concept:– Cells work together to carry out complex

functions.

Multicellular organisms depend on interactions among different cell

types.• Tissues are groups of cells that perform a similar function.

• Organs are groups of tissues that perform a specific or related function.

• Organ systems are groups of organs that carry out similar functions.

Specialized cells perform specific functions.

• Cells develop into their mature forms through the process of cell differentiation.

• Cells differ because different combinations of genes are expressed.

• A cell’s location in an embryo helps determine how it will differentiate.

Specialized cells develop from a single zygote.

• Organisms are made up of specialized cells.

red blood cell nerve cell

• Zygotes first divide into embryonic stem cells. • Stem cells develop in two stages. – determination,

or committing to become one cell type

– differentiation, or acquiring specialized structures and functions

cell

Specialized cells function together in tissues, organs, organ systems, and the whole organism.

• Specialized cells perform specific tasks.

• Tissues are groups of similar cells working together.

tissue

– epithelial tissue – connective

tissue – muscle tissue – nervous tissue

• There are 11 major organ systems in the human body.

Ted Ed Video

http://ed.ted.com/lessons/making-sense-of-how-life-fits-together-bobbi-seleski

STOP & REVIEW• Specialized cells develop from a single _______.• zygote• Zygotes first divide into embryonic ____________.• Stem cells• Stem cells develop in two stages.

– ___________, or committing to become one cell type– determination– ____________, or acquiring specialized structures and functions.– differentiation

• The five levels of biological organization are (in order)• Cells• Tissue• Organ• Organ System• Organism