Cell Functions

1
Cell Functions
Biology Basics
Review!

• Growth and Mitosis

2
Section One

• Surface Area/Volume of Cells

3
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.

4
Cell 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
• gt More nutrients can enter.
• lt More wastes can leave.

5
Surface 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.

6
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.

7
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

• All materials needed by a cell must pass through
  the ______________.
• The volume of a cell is a measure of the amount
  of ______________.
• The ____________ amounts required by a cell
  increase as the cell grows.
• The ____________ determines how much waste can
  leave the cell.

8
Answers
membrane

• All materials needed by a cell must pass through
  the ______________.
• The volume of a cell is a measure of the amount
  of ______________.
• The ____________ amounts required by a cell
  increase as the cell grows.
• The ____________ determines how much waste can
  leave the cell.

cytoplasm
nutrient
surface area
9
Section Two

• Experimenting With The Size of Cells

10
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.

11
Surface 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, lets 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).

12
Experimental Results
Cell 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
• membranes surface area.
• A ratio of 1.0 to 1 shows that the cytoplasmic
  volume is balanced by the
• surface area of the membrane.

13
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.

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Results

• 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.

15
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.

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Now, You Should Be Able To 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. The total amount of membrane area that
is exposed to the environment after division is
greater than before. Each new cell is now
better equipped 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.

17
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.

18
Try These Questions

• Select the letter of the correct answer from the
  list below

A. surface area D. slower B. faster E. volume C. division F. nutrients

• Cell _____________ increases the surface area of
  a cell.
• A cell increases its surface area to absorb more
  ____________ by dividing.
• The _____________ of the cell membrane limits
  cell growth.
• As the cell grows, the surface area increases
  ___________ than the volume.

19
Answers
division

• Cell _____________ increases the surface area of
  a cell.
• A cell increases its surface area to absorb more
  ____________ by dividing.
• The _____________ of the cell membrane limits
  cell growth.
• As the cell grows, the surface area increases
  ___________ than the volume.

nutrients
surface area
slower
20
Section Three

• Chromosomes in Cell Division

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What Makes One Organism 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
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Chromosomes

• 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.

13

• 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? ______

39
23
23
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.

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Try These Questions

• Select the letter of the correct answer from the
  list below

A. different D. the same B. membranes E. groups C. chromosomes F. pairs

• The ________________ contain all the information
  about an organism.
• The chromosomes within a cell are found in
  ________________.
• Different kinds of organisms have ___________
  numbers of chromosomes.
• All the cells making up an organism have
  ____________ number of chromosomes.

25
Answers
chromosomes

• The ________________ contain all the information
  about an organism.
• The chromosomes within a cell are found in
  ________________.
• Different kinds of organisms have ___________
  numbers of chromosomes.
• All the cells making up an organism have
  ____________ number of chromosomes.

pairs
different
the same
26
Drosophila

• 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.

27
Drosophila Dividing

• Lets look at two Drosophila cells in the process
  of dividing.
• Remember Only one of the two diagrams is
  correct!

2
1
Please Note The green chromosomes are identical
to the red ones.
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Diagram 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.

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Diagram 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.

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Mitosis

• 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.

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Replication

• How does a cell with four chromosomes give rise
  to two cells, each with four chromosomes?
• Copies of the parent cells chromosomes are
  formed.
• These exact copies then become part of the
  daughter cells.
• The formation of exact copies of the parent
  cells chromosomes is an important step in
  mitosis!
• It is called REPLICATION.

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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.

33
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.

34
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.

35
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
homologous
parent
daughter
36
Section Four

• Stages of Mitosis

37
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.

38
A Typical Animal Cell
Cell Membrane It is made of protein, lipid and
carbohydrate. It regulates the movement
of materials into and out of the cell.
Centrosome It is involved in mitosis and
usually is composed of a pair of centrioles that
appear later in mitosis. (Not Pictured.)
Nuclear Membrane It regulates the transport of
materials between the cytoplasm and the nucleus.
Chromosomes They are made of DNA and contain
the hereditary (genetic) information of the
organism.
Nucleolus This structure, found in the nucleus,
is involved in the manufacture of protein. It
disappears during mitosis. (Found in this area.)
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Stages of Mitosis

• When a cell undergoes mitosis, it goes through
  five stages.

Interphase
Prophase
Metaphase
Anaphase
Telophase
40
Five Stages of Mitosis
During interphase, the chromosomes replicate
(make exact copies of themselves). This is one
of the most important parts of mitosis. The
daughter cells eventually receive the same
information as contained in the parent cell.
41
Five Stages of Mitosis
During 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.
42
Five Stages of Mitosis
During 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.
43
Five Stages of Mitosis
Chromatids
Centromere
Notice that the pair of chromosomes (red and
yellow) are exact copies of each other.
44
Five Stages of Mitosis
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!
45
Five Stages of Mitosis
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.
46
Five Stages of Mitosis

• Study the animated diagram below. Can you
  identify the five stages of mitosis?

47
Five Stages of Mitosis

• Finally, 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)

48
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.

49
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.

Onion Root Tip Mitosis
Interphase Prophase Metaphase Anaphase Telophase
50
Try These Questions

• Select the letter of the correct answer from the
  list below

A. spindle D. metaphase B. centriole E. anaphase C. replication F. cell plate

• The ________________ of chromosomes occurs during
  interphase.
• A ________________ forms during the telophase of
  a plant cell.
• During anaphase, the chromosomes move along the
  ______________ fibers.
• Chromosomes line up along the equatorial plane
  during the ________________ stage.

51
Answers
replication

• The ________________ of chromosomes occurs during
  interphase.
• A ________________ forms during the telophase of
  a plant cell.
• During anaphase, the chromosomes move along the
  ______________ fibers.
• Chromosomes line up along the equatorial plane
  during the ________________ stage.

cell plate
spindle
metaphase
52
Section Five

• Testing Your Knowledge

53
This Is A Test of What You Have 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.

54
Select The Best Matching Choice
Answer Column Found outside the cell Attaches chromatids Forms spindle fibers In daughter cells only In plant cells only Formed by nucleolus Contains genes Unit of length

• Chromosome

Correct Answer G The chromosomes contain the
genes that may be expressed as traits
(characteristics) in the organism. The
information (as genes) is arranged in a
definite sequence along the chromosomes.

• Centromere

Correct Answer B The centromere attaches the
chromatids (chromosome pairs) to the spindle
fibers during mitosis. The chromosomes then are
drawn to opposite poles of the cell.
55
Select The Best Matching Choice

• Centriole

Answer Column Found outside the cell Attaches chromatids Forms spindle fibers In daughter cells only In plant cells only Formed by nucleolus Contains genes Unit of length
Correct Answer C The centriole is the cell
structure that produces astral rays and spindle
fibers. The chromosomes line up and travel along
the spindle fibers during mitosis. Centrioles
are produced by the centrosome.

• Micron

Correct Answer H A 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.
56
Select The Best Choice To Complete Each Analogy
telophase

• First is to last as interphase is to
  _______________.
• A. prephase
• B. prophase
• C. telophase
• D. metaphase
• E. anaphase

Since interphase is the beginning of mitosis, it
can be considered to be the first step.
Telophase is the last step in this process.
57
Select The Best Choice To Complete Each Analogy
gene

• Word is to page as ____________ is to
  chromosome.
• A. nucleus
• B. nuclear membrane
• C. centrosome
• D. centromere
• E. 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.
58
Fill In The Blanks
surface area
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 ____________.
divide
cell division
mitosis
59
Cell Functions
Biology Basics
Review!
You Have Completed...

• Growth and Mitosis