KEY CONCEPT Cells have distinct phases of growth ... Cells have distinct phases of growth, reproduction and normal functions. APK: Why do you always cut your hair? 5.1 The Cell Cycle

5.1 The Cell Cycle

KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions.

Objective: Cells have distinct phases of growth, reproduction and normal functions.

APK: Why do you always cut your hair?

5.1 The Cell Cycle

Cells double their DNA in order to divide and create two nearly identical duplicates or copies.

Divide – to separateDuplicate – an identical copyDouble – to increase twofoldCopy – a reproduction of an original

5.1 The Cell Cycle

• The cell cycle has four main stages.

– Gap 1 (G1): 2. cell growth and normal functions, double organelles

– DNA synthesis (S): 4. copies DNA, Replication

– Gap 2 (G2): 6. additional growth, normal functions

• The main stages of the cell cycle are

5.1 The Cell Cycle

• The cell cycle has four main stages.• The main stages of the cell cycle

• Take out a textbook and turn toCH 5.1 – page 134

Copy down the diagram (justlike the one to the right→) andmake sure to take detailed noteson what happens in each part ofthe cell cycle!

5.1 The Cell Cycle

• Cells divide at different rates.

• The rate of cell division varies with the need for those types of cells.

• Some cells are unlikely to divide (G0).

5.1 The Cell Cycle

• Cell size is limited.

• Volume increases faster than surface area.

5.1 The Cell Cycle

• Surface area must allow for adequate exchange of materials.

– Too small, not enough machinery– Too big, nutrients and waste can’t move in/out– Cell growth is coordinated with division.– Cells that must be large have unique shapes.

5.1 The Cell Cycle

• Mitosis occurs only if the cell is large enough and the DNA undamaged.

– Interphase– Mitosis (M): Cell division

includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)

– Prophase– Metaphase– Anaphase– Telophase– cytokinesis

5.1 The Cell Cycle

• What are the four main parts of the cell cycle?• What phase are cells in during the majority of

their life span?• Why would some cells have a shorter life cycle

than others?• Are there cells that rarely or never divide?

5.1 The Cell Cycle

Generalization

What is the purpose of the cell cycle?

5.1 The Cell Cycle

• Homework:

• Answer the following questions:

1. During which stage of the cell cycle is the DNA copied?2. Which stages of the cell cycle generally require about

the same amount of time in all human cells?3. What limits the maximum size of a cell?

5.2 Mitosis and Cytokinesis

KEY CONCEPT Cells divide during mitosis and cytokinesis.

Objective: Describe the structure of a chromosome.

APK: What would you do if you had to put a lot of clothes into a small suitcase?


• Chromosomes condense at the start of mitosis.

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

DNA doublehelix

DNA andhistones

Chromatin SupercoiledDNA


• 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.

Condensed, duplicated chromosome

chromatid

telomere

centromere

telomere


Parent cell

centrioles

spindle fibers

centrosome

nucleus withDNA

• Interphase prepares the cell to divide.

• During interphase, the DNA is duplicated.

• Mitosis and cytokinesis produce two genetically identical daughter cells.


• Mitosis divides the cell’s nucleus in four phases.– During prophase, chromosomes condense and

spindle fibers form.


• Mitosis divides the cell’s nucleus in four phases.– During metaphase, chromosomes line up in the

middle of the cell.


• Mitosis divides the cell’s nucleus in four phases.– During anaphase, sister chromatids separate to

opposite sides of the cell.


• Mitosis divides the cell’s nucleus in four phases.– During telophase, the new nuclei form and

chromosomes begin to uncoil.


• Cytokinesis differs in animal and plant cells.– In animal cells, the

membrane pinches closed.

– In plant cells, a cell plate forms.


• Generalization:

• Cells have distinct phases of growth, reproduction and normal functions.


• 5.2 Homework Check• 1. Draw what a chromosome looks like • during metaphase. Identify the chromatids • and the centromere.

• 2. Briefly explain why the daughter cells resulting from mitosis are genetically identical to each other and to the original cell.

• The independent variable is temperature and the dependent variable is the number of daily doublings.

• 3. How do prophase and telophase differ?• Prophase and telophase are opposites. The nuclear envelope fragments,

chromosomes condense, and spindle fibers start to assemble in prophase. In telophase , the reverse occurs: the nuclear envelope reforms, chromosome uncoil, and spindle fibers disassemble.

• 4. Using a light microscope you observe a cell that has no nucleus. What features would you look for to determine whether it is a eukaryotic cell undergoing mitosis or a prokaryotic cell?

• Other organelles should be visible in a eukaryotic cell along with (condensed) chromosomes and spindle fibers if it were undergoing mitosis.


• Homework for tomorrow:

•Read pages 144-147 and answer questions 1-3 on page 147

5.3 Regulation of the Cell Cycle

KEY CONCEPTCell cycle regulation is necessary for healthy growth.

Objective: Identify internal and external factors that regulate cell division.

APK: What is cancer?


• Internal and external factors regulate cell division.

• External factors include physical and chemical signals.• Growth factors are proteins that stimulate cell division.

– Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells.


• Two of the most important internal factors are kinases and cyclins.– Cyclin: group of proteins that triggers action of

kinases– Kinase: enzymes that affect molecule’s activity

- kin = Kinetics, kinein = “to move”- ase = enzyme

– Together these both help a cell advance to different stages of the cell cycle

• External factors trigger internal factors, which affect the cell cycle.

External growth factors

Cyclins

Kinases

Triggered cell cycle activities


– a normal feature of healthy organisms– caused by a cell’s production of self-destructive

enzymes– occurs in

developmentof infants

webbed fingers

• Apoptosis is programmed cell death.


• Cell division is uncontrolled in cancer.

• Cancer cells form disorganized clumps called tumors.

cancer cell bloodstre

am

normal cell

– Benign tumors remain clustered and can be removed.– Malignant tumors metastasize, or break away, and can

form more tumors. (noun = metastasis)


• Different growth patterns of tumors


• Cancer cells do not carry out necessary functions.

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


• Carcinogens are substances known to promote cancer.– UV radiation– Smoking– Other forms of radiation (nuclear radiation, x-rays,

etc.)• Standard cancer treatments typically kill both cancerous

and healthy cells.


• Viruses can also cause cancer!


• How are cancers named? Type of tissue of origin:• Carcinoma: tumor of the internal or external lining of the

body (skin & covering and lining of organs and internal passageways).

• Sarcoma: cancer that originates in supportive and connective tissues such as bones, tendons, cartilage, muscle, and fat.

• Leukemias ("liquid cancers" or "blood cancers") are cancers of the bone marrow (the site of blood cell production).

• Lymphomas develop in the glands or nodes of the lymphatic system, a network of vessels, nodes, and organs.


• How are cancers named? First site of origin:


APPLICATION

1. Explain the process of how cancer begins and causes metastasis.

2. What are some external and internal factors that cause the cell cycle to go wrong?


• Generalization:

• Why is cell cycle regulation necessary for healthy growth?


• Homework Check• 1. Describe what a growth factor is and how it influences

the cell cycle.• A growth factor is an external signal that stimulates

growth and division of cells.• 2. Explain how cancer cells differ from healthy cells.• Cancer cells have uncontrolled division, grow rapidly

without many growth factors, can form tumors, can metastasize and do not contribute to the body’s functions.

• 3. How do benign and malignant tumors differ?• Benign tumors, cancer cells clustered together and

relatively harmless.• Malignant tumors, cancer cells can metastasize and form

more tumors.


• Homework for Friday October 30th• Read pages 148-150 and answer questions 1-3 on page

150.

5.4 Asexual Reproduction

Many organisms reproduce by cell division.

GOAL:

● Compare and contrast binary fission and mitosis.

● Describe how some eukaryotes reproduce through mitosis.

APK:

What is asexual reproduction?


Sexual Reproduction- joining of an egg and sperm cell, one from each of two parents.

• Offspring are genetically unique• Have a mixture of genes from both parents

Asexual Reproduction- creation of offspring from a single parent and does not involve the joining of gametes.

• Offspring are genetically identical to each other and the single parent.


• Most prokaryotes reproduce through binary fission.

Binary fission- asexual reproduction of a single celled organism by division into two daughter cells genetically identical to the parent cell.

parent cell

DNA duplicates

cell begins to divide

daughter cells


Mitotic Reproduction

Some eukaryotes reproduce through mitosis. - Usually simple plants and animals

There are three types:

• Budding

• Fragmentation

• Vegetative Reproduction


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

bud

Hydra

Yeast


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.


What are other advantages for asexual reproduction?

All organisms can potentially reproduce.

- Male and female have offspring

Don’t have to look for a mate.

- takes time, energy - need specific structures, signals, and behaviors


APPLICATION

• Record in a t-chart the advantages and disadvantages of asexual reproduction


GENERALIZATION

Why do some organisms reproduce asexually?


HOMEWORK

1. Explain how mitosis differ from binary fission.

2. Briefly explain why cutting s flatworm into pieces would not kill it.

5.5 Multicellular Life

Objective: Identify the importance of stem cells.

APK: What do you know about stem cells?


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.

❖ Organ systems work together to help organisms maintain homeostasis.


Specialized cells perform specific functions.• Cell differentiation- Process where cells develop into their mature forms.• Cells differ because different combinations of genes are expressed.• A cell’s location in an embryo helps determine how it will differentiate.

Outer: skin cellsPrevent infection, dehydration

Middle: bone cellsSupport, protect organs

Inner: intestinesIncrease absorption


• Stem cells are unique body cells.• Stem cells have the ability to

– divide and renew themselves– remain undifferentiated in form– develop into a variety of specialized cell types


Stem cells are classified into three types

– Totipotent- can grow into any other cell type– Pluripotent- can grow into any cell type but a totipotent cell– Multipotent- can grow into cells of a closely related cell

family


First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.

Stem cells come from adults and embryos

Adult stem cells – can be hard to isolate and

grow.– may prevent transplant

rejection.– Limited cell type potential

Embryonic stem cells – Raise ethical issues– are pluripotent and

can be grown indefinitelyin culture

– May be rejected by a patients body


The use of stem cells offers many currently realized and potential benefits.

– used to treat leukemia and lymphoma.

– may cure disease or replace damaged organs.

– may revolutionize the drug development process.


APPLICATION

• 1. List treatment benefits and risks of both types of stem cells.

• 2.What are the defining charactertics of stem cells?


• GENERALIZATION• Cells work together to carry out complex functions

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KEY CONCEPT Cells have distinct phases of growth ... Cells have distinct phases of growth, reproduction and normal functions. APK: Why do you always cut your hair? 5.1 The Cell Cycle