10.1 Limits to Cell SizeName:

Biology 6.0Date: Period:

The Story of the Three Cells

One reason cells are small is that, as they grow, their volume increases faster than their surface area. Before starting take a moment to think about what problem this causes the cell?

Once upon a time there was a family of three cells. There was baby, momma and poppa cell. They all lived together in the town of human body, however there was a problem. Momma and Poppa cell could never find enough food to be full, but baby cell for some reason was always fine.

Use a surface area to volume ratio to explain this problem. Here are some formulas to remember:

Volume=

Surface Area =

Ratio is found when Surface Area is divided by Volume

Calculate the Volume, Surface Area and Ratio using the given measurements.

Baby Cell / Momma Cell / Poppa Cell
L = 1mm, H = 1mm, W = 1mm / L = 3mm, H = 3mm, W = 3mm / L = 9mm, H = 9mm, W = 9mm
Volume = / Volume = / Volume =
Surface area = / Surface area = / Surface area =
Surface area to volume ratio = / Surface area to volume ratio = / Surface area to volume ratio =
  1. Which cell has the greatest volume?
  2. Which cell has the smallest volume?
  3. Which cell has the greatest surface area?
  4. Which cell has the smallest surface area?
  5. Which cell has the greatest surface area to volume ratio?
  6. How many small cubes do you think it would take to fill the medium cube?
  7. What would the surface area be if L = 2cm, W = 3cm and H = 7cm?
  8. What is the volume of a cube with sides L = 3cm, W = 2cm, and H = 7cm?

Why are cells so small?

Think about this: even though a whale is much larger than a human and a human is much larger than a tulip, their cells are all roughly the same size. Whales donʼt have larger cells than humans, just more of them.

There is a very specific reason why cells are the size they are. Anytime this cell interacts with its environment, it does so at its membrane. The more membrane a cell has, the more exchange it can perform with its environment. (This exchange can include activities such as obtaining nutrients or getting rid of wastes.) We refer to the amount of surface that an object has as its surface area (SA).

Once materials get inside the cell, they move via diffusion. Diffusion is the random movement of particles that results in their dispersion in the cytoplasm. A drop of food coloring in a beaker of water will diffuse until the entire beaker is the same color. This type of movement occurs inside cells as a way of dispersing molecules. Diffusion works best over short distances. Imagine how long it would take food coloring molecules to diffuse in a water glass vs. in a swimming pool. Because the water glass has less volume (V), diffusion is more efficient.

Cells try to maximize their surface area (in order to improve exchange) and minimize their volume (to make diffusion more efficient). A basketball-sized cell would have lots of surface area (good), but also lots of volume (bad). Think about how long it would take molecules to diffuse from the outer portion of the ball to the center. A ping-pong ball or a marble would be better choices. When we discuss the interplay of these two quantities, we use the ratio of surface area to volume (abbreviated SA/V). Ideal cells have large SA values, but small V values.

Instructions:

First, look at the photos of the cells. These are very young embryos from sea urchins, marine organisms that you may have seen in nature documentaries or possibly along a rocky coastline. These photos were taken over a span of 105 minutes, beginning immediately after fertilization (Panel 1). The fertilized egg then divided once (Panel 3) to produce a two cell embryo (Panel 4), and then again (Panel 5) to produce a 4-cell embryo (Panel 6).

Eventually, hundreds of divisions would result in a tiny sea urchin larva that would settle to the sea bed and grow into a mature urchin (see photo to right).

Embryonic cells such as these are convenient to use as models for cell size because they are nearly perfect spheres.

  1. To maintain life, and carry out cellular functions, materials must be able to move into and out of the cell. Also, material needs to be able to move within the cell. What might be the advantage of having a large surface area?
  1. What might be the disadvantage of having a large volume?
  1. Explain how a small change in cell size can have a huge impact on the cell and its normal functions.
  1. So why are cells so small?

10.1 Cell Growth, Division, and ReproductionName:

BiologyDate: Period:

Limits to Cell Size

For Questions 1–4, write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true.

1. As a cell’s size increases, its amount of DNA also increases.

2. The amount of activity in a cell is related to its volume.

3. The smaller the cell, the smaller its ratio of surface area to volume.

4. The information crisis in a cell is solved by the replication of the DNA

before cell division.

  1. In the visual analogy of the growing town, what does the library represent? Identify two characteristics that make it a good choice for this analogy.
  1. How does the analogy of a cell to a town help you understand why cells divide?

The chart below shows key terms from the lesson with their definitions. Complete the chart by writing a strategy to help you remember the meaning of each term. One has been done for you.

Term / Definition
A cell divides into two new daughter cells
Reproduction involving only one parent organism
Reproduction in which cells from two different parents join to form a new organism

Cell Division and Reproduction

  1. is the formation of new individuals.
  2. For single-celled organisms, cell division is a form of reproduction.
  3. Most multicellular organisms reproduce by reproduction.
  4. Vascular tissue helps plants transport water against the force of gravity. Because of this, plants that lack vascular tissue do not grow very tall. How is this situation similar to the information you have learned in this lesson? Explain.

A T-chart is a way to organize information. One way to make a T-chart is to write the textbook headings in the left column of the chart. Rewrite these headings as questions in the right column. Then, as you read, answer the question in your own words. As you read the lesson, complete the T-chart.

Headings / Questions and Answers
Limits to Cell Size
Cell Growth and Reproduction / Why are cells limited in size?
______
______
______
Why are cell division and reproduction important?
______
______
______

Venn Diagram In the space where the circles overlap, write the features that the topics share. In the space where the circles do not overlap, write the features that are unique to each topic. Complete the Venn diagram below to compare asexual and sexual reproduction.

Asexual Sexual

Limits to Cell Size - Ratio of Surface Area to Volume

  1. Draw a line from the edge of Circle A to the dot in the center of Circle A. Do the same with Circle B. Which line looks longer?
  2. Look at the triangles in each circle. Suppose they have to move to the dot in the center. (Assume the triangles are traveling at the same speed.) Which triangles would get to the center faster—those in Circle A or those in Circle B? Explain your reasoning.
  3. Imagine that Circle A and Circle B are cells. The triangles are materials the cells need to move in or out, or exchange. Which cell would have a greater problem exchanging materials? Explain your reasoning.

10.2 The Process of Cell DivisionName:

BiologyDate: Period:

Chromosomes

For Questions 1–5, complete each statement by writing the correct word or words.

  1. Cells carry genetic information in packages of DNA called .
  2. Most have only one circular strand of DNA.
  3. In eukaryotic cells, the genetic structure consists of DNA and a tightly wound protein, which together form a substance called .
  4. The beadlike structures formed by DNA wrapped around proteins are called nucleosomes.
  5. ______make possible the precise separation of DNA during cell division.

The chart below shows key terms from the lesson with their definitions. Complete the chart by writing a strategy to help you remember the meaning of each term. One has been done for you.

Term / Definition
Series of events a cell goes through as it grows and divides
Area where two sister chromatids are attached.
One of two identical “sister” parts of a replicated chromosome
A combination of DNA and protein found in eukaryotic cells
Made up of DNA; contains the genetic information needed to make new cells and carry out cell functions
Part of the eukaryotic cell cycle during which the cytoplasm divides
Long period of the cell cycle between one cell division and the next
Part of the eukaryotic cell cycle during which the nucleus divides

The Prokaryotic Cell Cycle

The diagram on the left shows how a prokaryotic cell divides. The stages of cell division are shown in order they happen. Use the flowchart on the right to describe the steps in prokaryotic cell division. In a flowchart, arrows connect one step to the next. Write the stages in prokaryotic cell division in order in the flowchart.

Cell DivisionFlowchart

  1. The process of cell division in prokaryotic cells is called .
  2. Will the new cells have the same genetic material as the parent cell, or will each cell have different genetic material?
  3. Is this asexual or sexual reproduction?
  4. An example of an organism that reproduces with this kind of reproduction is a

© Pearson Biology1

a) salamander.

b) histone.

c) red blood cell.

d) bacterium.

© Pearson Biology1

The Cell Cycle

  1. What happens during interphase?
  2. Complete the cell cycle diagram by writing the correct name of a phase on each line.
  1. Color the phase in which most cell growth occurs blue.
  2. Color the phase in which DNA replication occurs red.
  3. Color the phase in which preparation for mitosis occurs yellow.
  4. Color the phase in which mitosis and cytokinesis occur orange.
  1. Which three phases make up interphase?
  2. The division of the cell nucleus during the M phase of the cell cycle is called
  3. In eukaryotic cells, what happens in the G1 phase that differs from the G2 phase?
  4. In eukaryotic cells, what are the two main stages of cell division?
  5. Match the process with the correct phase.

SA. Cells do most of their growing.

G2B. Chromosomes are replicated, and the synthesis of DNA molecules takes place

G1C. Many of the organelles and molecules required for cell division are produced.

Mitosisis the process by which the nucleus of most eukaryotic cells divides. Mitosis has four phases: prophase, metaphase, anaphase, and telophase.

  1. Label the four phases of mitosis in the diagram.
  2. Label the spindles and centrioles in one of the phases.
  3. Color each chromosome in prophase a different color. Follow each of these chromosomes through mitosis. Show this by coloring the correct structures in each phase of mitosis.

  1. In which phase do the chromosomes line up in the middle of the cell?
  2. In which phase do the chromosomes become visible?
  3. In which phase do the chromosomes move until they form two groups near the poles of the spindles?
  1. During prophase, when cell chromosomes become visible, what are the duplicated strands of DNA called? What is the name for the area in which these duplicated strands are joined?
  1. What structures are spindle fibers attached to that help pull the paired chromosomes apart?

© Pearson Biology1

Event

______1.

______2.

______3.

______4.

______5.

______6.

______7.

______8.

______9.

______10.

______11.

______12.

______13.

______14.

______15.

______16.

______17.

______18.

______19.

______20.

______21.

______22.The chromosomes separate and begin to move to opposite sides of the cell.

______23.The chromosomes become visible. The centrioles take up positions on opposite sides of the nucleus.

______24.A nuclear envelope re-forms around each cluster of chromosomes. The nucleolus becomes visible in each daughter nucleus.

______25.The chromosomes line up across the center of the cell.

Phase of Mitosis

  1. Telophase
  2. Prophase
  3. Metaphase
  4. Anaphase

© Pearson Biology1

  1. The four circles below represent the nucleus of a cell going through mitosis. Draw four chromosomes as they go through each phase. Label each phase and describe what is happening to the DNA.

© Pearson Biology1

Cytokinesis

  1. What is cytokinesis?
  2. Use the Venn diagram to compare and contrast cytokinesis in animal cells with cytokinesis in plant cells.

10.3 Regulating the Cell CycleName:

Biology 6.0 Date: Period:

Lesson Objectives

  • Describe how the cell cycle is regulated.
  • Explain how cancer cells are different from other cells.

Lesson Summary

Controls on Cell Division - Dozens of proteins regulate the cell cycle.

  • Cyclins are proteins that regulate the timing of the cell cycle in eukaryotic cells.
  • Regulatory proteins work both inside and outside of the cell.
  • Internal regulators allow the cell cycle to proceed when certain events have occurred within a cell.
  • External regulators called growth factors stimulate the cell cycle. Other external regulators cause the cell cycle to slow down or stop.
  • Apoptosis is programmed cell death that plays a key role in the development of tissues and organs.

Cancer: Uncontrolled Cell GrowthCancer is a disorder in which cells divide uncontrollably, forming a mass of cells called a tumor.

  • Cancers are caused by defects in genes that regulate cell growth.
  • Treatments for cancer include:
  • removal of cancerous tumors.
  • radiation, which interferes with the copying of DNA in multiplying cancer cells.
  • chemotherapy, which is the use of chemicals to kill cancer cells.

Controls on Cell Division

Write True if the statement is true. If the statement is false, change the underlined word or words to make the statement true.

______1.Cells tend to continue dividing when they come into contact with other cells.

______2.Cell division speeds up when the healing process nears completion.

______3.Proteins called growth factors regulate the timing of the cell cycle in eukaryotic cells.

______4.If chromosomes have not attached to spindle fibers during metaphase, an internal regulatory protein will prevent the cell from entering anaphase.

______5.Growth factors are external regulatory proteins that slow down the cell cycle.

______6.Once apoptosis is triggered, a cell proceeds to self-destruct.

Complete the cause-and-effect chart by giving an example of an effect caused by each type of regulatory protein.

Factors Affecting the Cell Cycle
Cause / Effect
Cyclins
Internal regulatory proteins
External regulatory proteins

Cancer: Uncontrolled Cell Growth

1.

2.

3.

4.

5.

6.

7.What is cancer?

8.What are the two basic types of tumors? Explain how they are different.

9.What is the cause of cancer?

10.Fill out the flowchart by completing each statement with the correct word or words.

11.Hair grows from hair follicles, pockets of continually dividing cells in the outer layer of the skin. New cells are added to the base of a hair shaft, inside each follicle. Use what you have learned in this lesson to explain why cancer patients often lose their hair when receiving chemotherapy and grow more hair after chemotherapy stops.

11.4 MeiosisName:

BiologyDate: Period:

BUILD Vocabulary - The chart below shows key terms from the lesson with their definitions. Complete the chart by writing a strategy to help you remember the meaning of each term. One has been done for you.

Term / Definition
Crossing-over / Exchange of DNA by the chromatids in a tetrad
Two sets of chromosomes, one from each parent
One set of chromosomes
Chromosomes in which one set comes from the female parent and one from the male parent
Cell division in which gametes are produced
A set of four chromatids formed by two pairs of replicated chromosomes
Cell produced by the union of egg and sperm

Compare/Contrast - make a compare/contrast table to show the differences between mitosis and meiosis. Use the terms or phrases to complete the compare/contrast chart. Write the terms or phrases in the correct column.

Mitosis / Meiosis

Phases of Meiosis - During meiosis, haploid gametes are produced from diploid cells. At the end of meiosis, the number of chromosomes in gametes is half the number of chromosomes in body cells.

Draw two homologous pairs of chromosomes (in different colors) in these diagrams to illustrate what happens during these three phases of meiosis. Do NOT leave this blank!!


  1. Identify which phase of meiosis is shown in the diagrams below.


  1. What does the diagram on the right show?
  1. During what phase of meiosis does this process occur?
  1. What is the result of this process?

Comparing Meiosis and Mitosis - Complete the table to compare meiosis and mitosis.