Cell Functions ~ Growth and Mitosis ~. Section One Surface Area/Volume of Cells

Cell FunctionsCell Functions

~ Growth and Mitosis ~~ Growth and Mitosis ~

Section OneSection One

Surface Area/Volume of CellsSurface Area/Volume of Cells

How Large Can A Cell Grow?How Large Can A Cell Grow?• That is a very difficult question to answer.

• Use the following diagram to review some parts of a typical cell.

• Cell Membrane – The Container for the cell.

• Nucleus – Controls cell activity

• Chromosomes – Contain genetic information

• Cytoplasm – Living material between nucleus and membrane.

Cell MembraneCell Membrane• The cell membrane is the container for the cell• All nutrients that enter the cell must pass through the

cell membrane.• All wastes produced by the cell must pass through the

cell membrane.

• As the surface area of the cell membrane increases:

> More nutrients can enter.

< More wastes can leave.

Surface AreaSurface Area• Select the cell from the diagrams below that has the greatest

surface area.

A. Nerve Cell B. Adipose (Fat) Cell C. Plant Cell

• The answer is A – The nerve cell has the largest surface area.

• Which cell has the largest volume?

• The answer is B – Volume is a measure of the fluid part of the cell.

Review…Review…

As a cell grows, the surface area of the cell membrane increases.

As the same cell grows, the volume (amount) of cytoplasm increases.

As the volume increases, more nutrients and wastes must pass through the cell membrane.

Try These Questions:Try These Questions:Select the letter of the correct answer from the list below:

A. membrane D. volume

B. nutrient E. surface area

C. cytoplasm F. wastes

1. All materials needed by a cell must pass through the ______________.

2. The volume of a cell is a measure of the amount of ______________.

3. The ____________ amounts required by a cell increase as the cell grows.

4. The ____________ determines how much waste can leave the cell.

Answers:Answers:

1. All materials needed by a cell must pass through the ______________.

2. The volume of a cell is a measure of the amount of ______________.

3. The ____________ amounts required by a cell increase as the cell grows.

4. The ____________ determines how much waste can leave the cell.

membrane

cytoplasm

nutrient

surface area

Section TwoSection Two

Experimenting With The Size of CellsExperimenting With The Size of Cells

Section One Review…Section One Review…

Our last exercise showed that large cells may have large volumes but comparatively small surface areas.

The size of the cell determines the amount of nutrients required and the amount of wastes that are produced.

The surface area of the cell membrane determines the amount of nutrients that can enter and the amount of wastes that can leave the cell.

Surface Area vs. VolumeSurface Area vs. Volume• Does the surface area of a cell increase at the same rate as the

volume of the cell?• To answer this question, let’s look at an experiment in which

seven volumes of a growing cell were selected.

• Note: If the cell membrane cannot increase enough to support the increased size of the cell, the cytoplasm cannot get enough nutrients, and the cell dies.

• Information: Cell sizes are measured by using the micron (“μ”). One micron equals 0.001 millimeters. Volume (cytoplasm) is measured in cubic microns (μ3), and surface area (cell membrane) is measured in square microns (μ2).

Experimental ResultsExperimental ResultsCell Volume (μ3) Cell Surface Area (μ2) Ratio*

Volume/Surface Area(Cytoplasm/Membrane)

1 6 0.2 to 1

50 81 0.6 to 1

100 129 0.8 to 1

200 205 1.0 to 1

300 269 1.1 to 1

400 326 1.2 to 1

500 378 1.3 to 1

• The ratio* shows the balance between the cytoplasmic volume and the membrane’s surface area.• A ratio of 1.0 to 1 shows that the cytoplasmic volume is balanced by the surface area of the membrane.

Graph of Data:Graph of Data:• As the cell increases in size, the cytoplasmic volume increases faster than

the surface area of the cell membrane.• A graph of the results shown in the chart on the previous slide helps you

understand that cell growth is limited by the surface area of the cell membrane.

Membrane and Cytoplasm Changes with Cell Size

0

100

200

300

400

500

600

1 2 3 4 5 6 7

Cells (By Increasing Size)

Vo

lum

e /

Are

a

Cytoplasm Volume

Membrane Area

Results…Results…Membrane and Cytoplasm Changes with Cell Size

0

100

200

300

400

500

600

1 2 3 4 5 6 7

Cells (By Increasing Size)

Vo

lum

e /

Are

a

Cytoplasm Volume

Membrane Area

Note: When the size of the cell grows larger than the fourth selection, the area of the membrane is less than the volume of the cytoplasm.• Cells larger than your fourth selection have membranes too small to bring in enough nutrients and get rid of the wastes that build up in the cytoplasm.

Try This Question:Try This Question:

Which of the following becomes stale first?

A. A loaf of bread sliced into two pieces.

B. A loaf of bread sliced into many pieces.

C. An uncut loaf of bread.

• The answer is B – As the bread is divided into more pieces, the surface area of the bread increases and more of the bread is exposed to the air.

Now, You Should Be Able To Now, You Should Be Able To Answer This Question…Answer This Question…

What does the cell do to increase its surface area when it grows too large?

ANSWER: The cell increases its surface area by dividing. Thetotal amount of membrane area that is exposed to the environmentafter division is greater than before. Each new cell is now betterequipped to absorb nutrients and get rid of waste.

Cell division increases the surface area of cells so that: More nutrients now can enter the cells. More wastes now can leave the cells.

Review…Review…

As the cell increases in size, more nutrients are needed, and more wastes are produced.

When the cell membrane is too small to support the volume of cytoplasm, the cell divides.


A. surface area D. slower

B. faster E. volume

C. division F. nutrients

1. Cell _____________ increases the surface area of a cell.

2. A cell increases its surface area to absorb more ____________ by dividing.

3. The _____________ of the cell membrane limits cell growth.

4. As the cell grows, the surface area increases ___________ than the volume.

Answers:Answers:

1. Cell _____________ increases the surface area of a cell.

2. A cell increases its surface area to absorb more ____________ by dividing.

3. The _____________ of the cell membrane limits cell growth.

4. As the cell grows, the surface area increases ___________ than the volume.

division

nutrients

surface area

slower

Section ThreeSection Three

Chromosomes in Cell DivisionChromosomes in Cell Division

What Makes One Organism What Makes One Organism Different From Another?Different From Another?

Study the following chart.

Organism Backbone Habitat Chromosome Number

Frog Yes Water 26

Cat Yes Land 38

Dog Yes Land 78

Human Yes Land 46

Shrimp No Water 254

Garden Pea No Land 14

ChromosomesChromosomes• Of the three categories listed on the previous slide, which one

best determines what the organism looks like?Answer – Chromosome Number.

• Chromosomes have the information for the structure of the organism, and how the organism functions.

• Notice that each type of organism has a characteristic number of chromosomes.

• These chromosomes are found in pairs.

How many pairs of chromosomes are found in each frog cell? ______

How many pairs of chromosomes are found in each dog cell? ______

How many pairs of chromosomes are found in each human cell? ______

13

39

23

Review…Review…

Chromosomes contain information that determines what the organism looks like and how it functions.

Each type of organism has a definite number of chromosomes in each cell.

Chromosomes are found in pairs.


A. different D. the same

B. membranes E. groups

C. chromosomes F. pairs

1. The ________________ contain all the information about an organism.

2. The chromosomes within a cell are found in ________________.

3. Different kinds of organisms have ___________ numbers of chromosomes.

4. All the cells making up an organism have ____________ number of chromosomes.

Answers:Answers:

1. The ________________ contain all the information about an organism.

2. The chromosomes within a cell are found in ________________.

3. Different kinds of organisms have ___________ numbers of chromosomes.

4. All the cells making up an organism have ____________ number of chromosomes.

chromosomes

pairs

different

the same

DrosophilaDrosophila• Each chromosome has genes (information) for many different traits.

• For example, the small fruit fly called Drosophila has 4 pairs of chromosomes in each cell.

• Look at the genes found on part of one of the chromosomes.

eye color

wing shape

body color

bristle shape

• The other chromosome of the pair () also has genes for the same traits.• Pairs of chromosomes that contain genes for the same traits are called homologous chromosomes.

DrosophilaDrosophila Dividing… Dividing…• Let’s look at two Drosophila cells in the process of

dividing.• Remember – Only one of the two diagrams is correct!

Please Note: The green

chromosomes are identical to the red ones.

Diagram #1Diagram #1• How many chromosomes are found in each cell in

Diagram #1 on the previous slide?• Answer: Four – The new cells shown in Diagram

#1 have only half the number of chromosomes of the original cell.

• The new cells are called daughter cells.• The original cell is called the parent cell.• Diagram #1 shows two daughter cells with only

half of the genes that were found in the parent cell.

Diagram #2Diagram #2• How many chromosomes are found in each new cell

in Diagram #2 on the previous slide?• Answer: Eight – Diagram #2 shows that each

daughter cell has the SAME number of chromosomes as the parent cell.

• The new cells in Diagram #1 have lost chromosomes.

• The chromosome number of the new cells in Diagram #2 is the same as the number in the parent (original) cell.

MitosisMitosis• Mitosis is the process that ensures the exact

duplication of the chromosomes in the nucleus during cell division.

• From this information, which diagram correctly shows mitosis?

• Answer: Diagram #2 – This diagram shows that each daughter cell has the same number of chromosomes, and the same information, as the parent cell.

• During mitosis, the daughter cells must receive the same information (genes on chromosomes) as the parent cell.

ReplicationReplication

• How does a cell with four chromosomes give rise to two cells, each with four chromosomes?

• Copies of the parent cell’s chromosomes are formed.

• These exact copies then become part of the daughter cells.

• The formation of exact copies of the parent cell’s chromosomes is an important step in mitosis!

• It is called: REPLICATION.

Replication of Chromosomes:Replication of Chromosomes:

• Keeps the chromosome number the same in each cell.

• Ensures that the information found in the genes is the same within each cell of the organism.

• Is an important step in the process of mitosis.

Review…Review…Homologous chromosomes are pairs of

chromosomes having genes (information) for the same traits.

Mitosis is a process that maintains the same number of chromosomes.

Replication is the formation of exact copies of the original chromosomes during the process of mitosis.

The parent cell is the original cell in cell division.Daughter cells are the two new cells that result from

the process of cell division.

Quiz:Quiz:Fill in the blanks in the following passage.

Every species (type) of plant or animal has a characteristic chromosome __________ that is the same for all members of that species. The chromosomes replicate during the process of mitosis and are found in pairs. The pairs of chromosomes containing genes for the same traits are called ___________ chromosomes. They are passed on from the original _________ cell to the new _________ cells during the process of cell division.

Quiz Answers:Quiz Answers:Fill in the blanks in the following passage.

Every species (type) of plant or animal has a characteristic chromosome __________ that is the same for all members of that species. The chromosomes replicate during the process of mitosis and are found in pairs. The pairs of chromosomes containing genes for the same traits are called ___________ chromosomes. They are passed on from the original _________ cell to the new _________ cells during the process of cell division.

number

homologousparent

daughter

Section FourSection Four

Stages of MitosisStages of Mitosis

Section Three Review…Section Three Review… During mitosis, the chromosomes in the nucleus of

the parent cell replicate into two identical sets. Each chromosome is made of DNA, which controls

all cell activities. DNA also controls the transfer of traits from parent to

offspring. When a cell undergoes mitosis, the chromosomes in

each daughter cell are exact copies of the parent cell.Although you began as a single cell, mitosis has

produced billions of cells of which you are composed. Every body cell contains chromosomes that are

identical to the original cell.

A Typical Animal Cell…A Typical Animal Cell…Cell Membrane: It is made ofprotein, lipid and carbohydrate.It regulates the movement ofmaterials into and out of the cell.

Centrosome: It is involved in mitosisand usually is composed of a pair ofcentrioles that appear later in mitosis.(Not Pictured.)

Nuclear Membrane: It regulates thetransport of materials between thecytoplasm and the nucleus.

Chromosomes: They are made ofDNA and contain the hereditary (genetic)information of the organism.

Nucleolus: This structure, found inthe nucleus, is involved in themanufacture of protein. It disappearsduring mitosis. (Found in this area.)

Stages of MitosisStages of MitosisWhen a cell undergoes mitosis, it goes

through five stages.

Five Stages of MitosisFive Stages of Mitosis

During interphase, the chromosomesreplicate (make exact copies ofthemselves). This is one of the mostimportant parts of mitosis.

The daughter cells eventually receivethe same information as contained inthe parent cell.

Five Stages of MitosisFive Stages of MitosisDuring prophase, the centrosome divides into two centrioles.

Fibers arise from the centrioles. These fibers are called astral rays.

Fibers also appear between the two centrioles and become the spindle.

The replicated chromosomes thicken and can easily be seen.

The nucleolus disappears.

The nuclear membrane disappears.

The centrioles continue to move to opposite ends of the cell.

The spindle forms from spindle fibers between the centrioles.

Five Stages of MitosisFive Stages of MitosisDuring metaphase, the chromosomes begin to line up along the middle of the spindle.

The imaginary center line of the spindle is called the equatorial plane.

Notice that each chromosome is securely attached to its replicated partner by a small structure called a centromere (small dot between pairs).

The centromere attaches each chromosome pair to the spindle fiber.

The replicated chromosomes, held by the centromere, are called chromatids.


Centromere

Chromatids

Notice that the pair of chromosomes (redand yellow) are exact copies of each other.


During anaphase, the chromosome pairs separate and move to opposite poles (ends) of the cell.

Notice that each pole has exactly the same chromosome pairs!


During telophase, the chromosomes become thin and long, as they did in interphase.

A new nuclear membrane forms.

The nucleolus reappears.

The final stage of mitosis occurs when the membrane pinches in. The two cells are called daughter cells. These cells are exact copies of the parent cell, and have the same information.

Five Stages of MitosisFive Stages of MitosisStudy the animated diagram below. Can

you identify the five stages of mitosis?

Five Stages of MitosisFive Stages of MitosisFinally, click on the link below to view an animated

(Macromedia Flash) presentation of Mitosis. This will require a connection to the internet. This is an excellent resource – you can click on specific stages of mitosis or play the entire animation. It also shows you what an actual cell would look like in each stage. (Link should automatically open in a web browser.)

CellsAlive! Mitosis(Click on Link)

Review…Review… Interphase

• The chromosomes replicate.• The centrioles begin to move apart.

Prophase• Chromosomes are visible and thick.• Nuclear membrane/nucleolus disappear.• Astral rays and spindle fibers form.

Metaphase• Chromosome pairs line up at midline.

Anaphase• Chromosome pairs separate and move to opposite poles.

Telophase• Nucleolus/nuclear membrane reappear.• Cell membrane pinches in.

Plant Cells…Plant Cells…• Plant cells are similar to animal cells, with two exceptions:

Plant cells have no centrosomes and do not form astral rays. The plant membrane does not pinch in. A cell plate forms

between the two daughter cells. By adding cellulose to the plate, a new cell wall is formed.

Interphase Prophase Metaphase Anaphase Telophase


A. spindle D. metaphase

B. centriole E. anaphase

C. replication F. cell plate

1. The ________________ of chromosomes occurs during interphase.

2. A ________________ forms during the telophase of a plant cell.

3. During anaphase, the chromosomes move along the ______________ fibers.

4. Chromosomes line up along the equatorial plane during the ________________ stage.

Answers:Answers:

1. The ________________ of chromosomes occurs during interphase.

2. A ________________ forms during the telophase of a plant cell.

3. During anaphase, the chromosomes move along the ______________ fibers.

4. Chromosomes line up along the equatorial plane during the ________________ stage.

replication

cell plate

spindle

metaphase

Section FiveSection Five

Testing Your KnowledgeTesting Your Knowledge

This Is A Test of What You Have This Is A Test of What You Have Learned…Learned…

• There are 10 questions on this test.

• Try to correctly answer all of the questions.

• If you miss a question, watch the screen for an explanation of the correct answer.

Select The Best Matching Choice:Select The Best Matching Choice:

Answer Column:

A. Found outside the cell

B. Attaches chromatids

C. Forms spindle fibers

D. In daughter cells only

E. In plant cells only

F. Formed by nucleolus

G. Contains genes

H. Unit of length

Chromosome:Correct Answer: GThe chromosomes contain the genes that may beexpressed as traits (characteristics) in the organism.The information (as genes) is arranged in a definitesequence along the chromosomes.

Centromere:Correct Answer: BThe centromere attaches the chromatids(chromosome pairs) to the spindle fibers duringmitosis. The chromosomes then are drawn to opposite poles of the cell.

Select The Best Matching Choice:Select The Best Matching Choice:

Answer Column:

A. Found outside the cell

B. Attaches chromatids

C. Forms spindle fibers

D. In daughter cells only

E. In plant cells only

F. Formed by nucleolus

G. Contains genes

H. Unit of length

Centriole:Correct Answer: CThe centriole is the cell structure that produces astral rays and spindle fibers. Thechromosomes line up and travel along the spindle fibers during mitosis. Centrioles areproduced by the centrosome.

Micron:Correct Answer: HA micron is the unit of length most frequently used when describing cell size. Square microns are used for area, and cubic microns are used for volume. A micron equals one millionth of a meter.

Select The Best Choice To Select The Best Choice To Complete Each Analogy:Complete Each Analogy:

First is to last as interphase is to _______________.

A. prephase

B. prophase

C. telophase

D. metaphase

E. anaphase

telophase

Since interphase is the beginning of mitosis, it can be considered to be the first step. Telophase is the last step in this process.

Select The Best Choice To Select The Best Choice To Complete Each Analogy:Complete Each Analogy:

Word is to page as ____________ is to chromosome.A. nucleus

B. nuclear membrane

C. centrosome

D. centromere

E. gene

gene

Since a word is a small piece of information that appears on a page, it is most like a gene (which also contains a small piece of information) on a chromosome.

Fill In The Blanks…As a cell grows, it increases its ________________ by increasing its cell membrane so that it may absorb more nutrients and get rid of more wastes. When a cell reaches its maximum size, it must ______________ by the process of ______________. Before the cell does this, it doubles the number of chromsomes during the process of ____________.

surface area

dividecell division

mitosis

Cell FunctionsCell Functions

~ Growth and Mitosis ~~ Growth and Mitosis ~

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Cell Functions ~ Growth and Mitosis ~. Section One Surface Area/Volume of Cells