Something to Think About !!!!

How does the size of your cells now compare to the size of your cells

when you were a baby?

Answers to Think About It:

The cells of an adult organism are no larger than those of a young organism –there are just more of them.

One More Thing To Think About ……

Why do cells make so many new cells instead of just having their cells get

larger and larger?

Reason # 1 DNA Overload

1.The information that controls a cell’s function is stored in DNA

2.DNA is able to meet the cell’s need when cells are small

3.If a cell were to grow too large, there is not enough information in the DNA molecule to control the larger cell and it is called DNA overload.

Reason # 2 Exchanging MaterialsIf cells were larger, the surface area to volume ratio would become too small and the cell wouldn’t be able to move materials fast enough across the cell membrane.

There would be traffic jams similar to the Thruway toll booths on a holiday weekend!

When do new cells need to be produced?

1.Replacement

• Cells get damaged and need to be replaced.

• Not all cells can be reproduced.

2.Growth

• The addition of more cells to make the organism larger.

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Life Span of Various Human Cells

Cell Type

Lining of esophagus

Lining of small intestine

Lining of large intestine

Red blood cells

White blood cells

Smooth muscle

Cardiac muscle

Skeletal muscle

Nerve cells

Life Span Cell Division

2-3 days Can divide

1-2 days Can divide

6 days Can divide

Less than 120 days Cannot divide10 hours to

decades Cannot divide

Long-lived Can divide

Long - lived Cannot divide

Long-lived Cannot divide

Long-lived Most do not divide

The cell cycle is a series of events that cells go through as they grow. It consists of four phases.

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G1 Phase

S Phase

G 2 Phase

M Phase

Cells spend 90 % of their time in Interphase.

Mitosis (M Phase)

•The M phase is brief and consists of a division of the cell’s nucleus and cytoplasm that results in two identical daughter cells.

•The identical daughter cells have the same number of chromosomes and the same genetic composition as the starting parent cell.

• In human cells, which have 23 pairs of chromosomes, the number of chromosomes (2n = 46) remains unchanged from the beginning till the end of mitosis.

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Mitosis has Four Phases

❖ Prophase❖ Metaphase❖ Anaphase❖ Telophase (Cytokinesis)

❖Memory helper: PMAT

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Prophase • 1st and longest phase of mitosis• Nuclear membrane (envelope) disappears• Chromosomes condense and you can see sister

chromatids and centromeres• Spindle fibers form. They are a microtubule structure

that helps separate the chromosomes.

Sister Chromatids

Centromere

Nuclear membraneSpindle

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The four C’s Vocabulary

Chromatin – The relaxed state that the DNA is in during interphase. It can look like a tangled up mess of spaghetti or string.

Centromere - the part of a chromosome that links sisterchromatids. During mitosis, spindle fibers attach to thecentromere and help to split the sister chromatids apart.

Sister Chromatids - They are created when a singlechromosome is replicated into two copies of itself. They areconnected by a centromere.

Centrioles– They assist in mitosis by allowing the spindle fibersto attach to them. They are not visible when the cell is not dividing

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Metaphase

• Chromosomes move to the middle of the cell• Each sister chromatid is attached to spindle

with a centromere

Spindle

centromere

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Metaphase

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Anaphase• Centromeres split• Sister chromatids are pulled apart to

opposite sides of the cell• Each chromatid is now a separate

chromosome

Sister Chromatids

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Anaphase

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Telophase• Two nuclear membranes (envelopes) reform• Chromosomes begin to uncoil and relax

reverting back to the chromatin state.

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Telophase

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Cytokinesis• Cytoplasm divides• Two new daughter cells are now separate• Cytokinesis occurs at the end of telophase.

Pinching in of cell membrane

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Okay, Now it’s your turn!

Interphase? Prophase? Metaphase? Anaphase? Telophase?

1 2 3 4

5 6 7

AnaphaseTelophase MetaphaseTelophase

Prophase Anaphase Interphase

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What is a Tumor ?

● A tumor is a mass of cells that results from uncontrolled cell division.

● Think of it as mitosis gone bad!

● There are 2 types of tumors:1. Benign

2.Malignant

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Benign Tumors

• A benign tumor is a mass of cells that lacks the ability to invade neighboring tissue or metastasize.

• Metastasize is the spread of a cancer from one organ or part to another organ or part.

• They are considered to be non-cancerous.

Moles are benign tumors Lymphatic system tumor

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Joseph Merrick August 5,1862 – April 11,1890‘The Elephant Man’

In 2001 it was proposed that Merrick had suffered from a combination of neurofibromatosis type I and Proteus syndrome. DNA tests conducted on his hair and bones have proven inconclusive.

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Benign Facial Tumors(neurofibromatosis)

James O’Neal (2008-2009)

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Malignant Tumors

• They invade surrounding tissues, and can spread to distant tissues and organs, which means that they can metastasize.

• They are considered to be cancerous.

• Cancer is uncontrolled cell division (mitosis) that can’t be stopped.

Melanoma Mouth Cancer

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Cancerous Cells Affects Homeostasis

•Interferes with nervous system tissue and blocks important nerve connections.

•Cancer cells absorb nutrients needed by the healthy cells.

•Prevent organs from functioning properly.

Lung Cancer

Asexual Reproduction

It Only Takes One !

Characteristics of Asexual Reproduction

● Only one parent is involved.

● Offspring are genetically identical to their parents.

● There are different types of asexual reproduction.

Type # 1 Binary Fission● Binary fission is when an organism divides by

mitosis to form two daughter cells of equal size.

● The nucleus and cytoplasm divide equally.

● All cells that come from a single cell are genetically identical to each other

● It occurs in single-celled organisms like Amoebas, paramecia, and bacteria

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Binary Fission in Paramecium

Binary Fission in Bacteria

Type # 2 Budding

● Budding is when a new organism arises as an growth of an older organism.

● The new organism is called the bud.

● The bud is a duplicate of the parent. It may separate or remain attached to form a colony.

● In budding there is an equal division of the nucleus, but unequal division of cytoplasm. So, one of the daughter cells is larger than the other.

● It occurs in multicellular organisms such as yeast, hydra and some cacti.

Hydra Budding

Yeast Budding

Desert Cactus

Type # 3 Sporulation

•Spores are specialized sex cells that contain a nucleus and small amount of cytoplasm.

•Spores are produced in large numbers by mitosis.

•They are surrounded by a tough protective coat that enables them to survive extreme conditions such as heat or cold.

•When conditions are favorable, the spores develop into a new organism.

•Bread mold, mushrooms, mosses, and ferns reproduce this way

Spores on a Fern leaf

Spore Pods

Moss Sporulation

Type # 4 Regeneration

● Regeneration is the development of a new organism from a part of a parent organism

● It occurs in starfish, planaria,hydra,crayfish, salamanders,newts

● Regeneration can also replace lost body parts like tails, claws, legs,and arms.

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Type # 5 Vegetative Propagation

•It is the process by which new plants develop from the roots, stems, or leaves of the parent plant.

•There are many different ways for this type of reproduction to occur:

1. runners

2. bulbs

3. tubers

4. cuttings

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Runners

•Stems that grow over the surface of the soil and at certain points the runner puts down roots and new plants grow from there.

•Examples: strawberries, blackberries, spider plants, mint , ivy

Ivy Plant

Strawberry Plant

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Bulbs

• A bulb is a short underground stem surrounded by thick leaves and contains stored food. As the plant grows it produces new bulbs which will grow into new plants.

Examples: Onions tulips lilies

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Tubers• A tuber is an enlarged part of an underground

stem that contains stored food.

• Potatoes are tubers. The have eyes, or tiny buds that can form a new potato plant.

• Carrots and radishes are also examples.

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Cuttings

A cutting is when a piece of roots, stems, or leaves develop into new plants.

Cutting Rooting Planting