section 10.4 biology book

8/18/2019 Section 10.4 Biology Book

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Lesson OverviewLesson Overview Cell DifferentiationCell Differentiation

Lesson OverviewLesson Overview

10.4 Cell Differentiation10.4 Cell Differentiation


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THINK ABOUT IT

The human body contains hundreds of different cell types, and

every one of them develops from the single cell that starts the

process. How do the cells get to be so different from each

other


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From One Cell to Many

How do cells become speciali!ed for different functions


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"ll organisms start life as #ust one cell.

$ost multicellular organisms pass through an early stage of

development called an embryo, which gradually develops into an

adult organism.


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During development, an organism%s cells become more

differentiated and speciali!ed for particular functions.

&or e'ample, a plant has speciali!ed cells in its roots, stems, and

leaves.


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Defining Differentiation

The process by which cells become speciali!ed is (nown as

ifferentiation!

During development, cells differentiate into many different types

and become speciali!ed to perform certain tas(s.

Differentiated cells carry out the #obs that multicellular organisms

need to stay alive.


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Differentiation in Mammals

Cell differentiation in mammals is controlled by a number of

interacting factors in the embryo.

"dult cells generally reach a point at which their differentiation is

complete and they can no longer become other types of cells.


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#tem Cells an Develo"ment

*hat are stem cells


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+ne of the most important uestions in biology is how all of the

speciali!ed, differentiated cell types in the body are formed from

#ust a single cell.

-iologists say that such a cell is toti"otent, literally able to doeverything, to form all the tissues of the body.

+nly the fertili!ed egg and the cells produced by the first few cell

divisions of embryonic development are truly totipotent.


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H$man Develo"ment

"fter about four days of development, a human embryo forms

into a blasto%yst, a hollow ball of cells with a cluster of cells

inside (nown as the inner cell mass.

The cells of the inner cell mass are said to be "l$ri"otent, whichmeans that they are capable of developing into many, but not all,

of the bodys cell types.


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#tem Cells

#tem %ells are unspeciali!ed cells from which differentiated

cells develop.

There are two types of stem cells/ embryonic and adult stem

cells.


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&mbryoni% #tem Cells

mbryonic stem cells are found in the inner cells mass of the

early embryo.

mbryonic stem cells are pluripotent.

esearchers have grown stem cells isolated from human

embryos in culture. Their e'periments confirmed that embryonic

stem cells have the capacity to produce most cell types in the

human body.


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A$lt #tem Cells

"dult organisms contain some types of stem cells.

"dult stem cells are m$lti"otent! They can produce many types

of differentiated cells.

"dult stem cells of a given organ or tissue typically produce only

the types of cells that are uniue to that tissue.


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Frontiers in #tem Cell 'esear%(

*hat are some possible benefits and issues associated with stem

cell research


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&t(i%al Iss$es

$ost techniues for (arvesting, or gathering, embryonic stem

cells cause destruction of the embryo.

3overnment funding of embryonic stem cell research is an

important political issue.

3roups see(ing to protect embryos oppose such research as

unethical.

+ther groups support this research as essential to saving human

lives and so view it as unethical to restrict the research.

C ff


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Section 10-1: Cell Growth The larger a cell becomes, the more demands the cell places on its DNA and the moretrouble the cell has moving enough nutrients and wastes across the cell membrane.

Section 10-2: Cell DivisionDuring the cell cycle, a cell grows, prepares for division, and divides to form two daughtercells, each of which then begins the cycle again.Biologists divide the events of mitosis into four phases: prophase, metaphase, anaphase,

and telophase.During prophase in animal cells, the centrioles separate and take up positions on oppositesides of the nucleus.During metaphase, the chromosomes line up across the center of the cell. icrotubulesconnect the centromere of each chromosome to the poles of the spindle.During anaphase, the centromeres that !oin the sister chromatids split, allowing the sisterchromatids to separate and become individual chromosomes."n telophase, the chromosomes, which were distinct and condensed, begin to disperse into

a tangle of dense material.#ytokinesis is the division of the cytoplasm.

Section 10-3: Regulating the Cell Cycle#yclins regulate the timing of the cell cycle in eukaryotic cells.#ancer cells do not respond to the signals that regulate the growth of most cells. As aresult, they form masses of cells called tumors that can damage the surrounding tissues.

C ll Diff ti ti


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section 10.4 biology book

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