Discovering Cells

1
Table of Contents

• Discovering Cells
• Looking Inside Cells
• Chemical Compounds in Cells
• The Cell in Its Environment

2
Development of the Cell Theory
- Discovering Cells

• The cell theory states the following
• All living things are composed of cells.
• Cells are the basic units of structure and
  function in living things.
• All cells are produced from other cells.

3
Light Microscopes
- Discovering Cells

• The lenses in light microscopes magnify an object
  by bending the light that passes through them.

4
Sequencing
- Discovering Cells

• Construct a flowchart showing how the work of
  Hooke, Leeuwenhoek, Schleiden, Schwann, and
  Virchow contributed to scientific understanding
  of cells.

Discovering Cells
Hooke sees cells in cork.
Leeuwenhoek sees many one-celled organisms.
Schleiden concludes that all plants are made of
cells.
Schwann concludes that all animals (and all
living things) are made of cells.
Virchow proposes that new cells form only from
cells that already exist.
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Links on Cell Theory
- Discovering Cells

• Click the SciLinks button for links on the cell
  theory.

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End of SectionDiscovering Cells
7
Nucleus
- Looking Inside Cells

• The nucleus is the cells control center,
  directing all of the cells activities.

8
Mitochondrion
- Looking Inside Cells

• Mitochondria are known as the powerhouses of
  the cell because they convert energy in food
  molecules to energy the cell can use to carry out
  its functions.

9
Endoplasmic Reticulum
- Looking Inside Cells

• The endoplasmic reticulum is similar to the
  system of hallways in a building. Proteins and
  other materials move throughout the cell by way
  of the endoplasmic reticulum. The spots on this
  organelle are ribosomes, which produce proteins.

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Plant and Animal Cells
- Looking Inside Cells
11
Golgi Body
- Looking Inside Cells

• The Golgi bodies receive proteins and other newly
  formed materials from the endoplasmic reticulum,
  package them, and distribute them to other parts
  of the cell.

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Plant and Animal Cells Activity
- Looking Inside Cells

• Click the Active Art button to open a browser
  window and access Active Art about plant and
  animal cells.

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Previewing Visuals
- Looking Inside Cells

• Before you read, preview Figure 12. Then write
  two questions you have about the illustrations in
  a graphic organizer like the one below. As you
  read, answer your questions.

Plant and Animal Cells
Q. How are animal cells different from plant
cells?
A. Plants cells have a cell wall and
chloroplasts, which animal cells to not have.
Q. What do mitochondria do?
A. Mitochondria convert energy in food molecules
to energy the cell can use.
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The Cytoplasm and Organelles
- Looking Inside Cells

• Click the Video button to watch a movie about
  cytoplasm and organelles.

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Specialized Cells
- Looking Inside Cells

• Click the Video button to watch a movie about
  specialized cells.

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End of SectionLooking Inside Cells
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Elements and Compounds
- Chemical Compounds in Cells

• Carbon dioxide, which is found in gas bubbles, is
  a chemical compound. So is water.

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Compounds in Bacteria and Mammals
- Chemical Compounds in Cells

• All cells contain carbohydrates, lipids,
  proteins, and nucleic acids, as well as water and
  other inorganic compounds. But do all cells
  contain the same percentages of these compounds?
  The graph compares the percentage of some
  compounds found in a bacterial cell and a cell
  from a mammal.

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Compounds in Bacteria and Mammals
- Chemical Compounds in Cells

• Reading Graphs
• What do the red bars represent? What do the blue
  bars represent?

• Red bars represent percentages of compounds in
  bacterial cells blue bars represent percentages
  of compounds in mammalian cells.

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Compounds in Bacteria and Mammals
- Chemical Compounds in Cells

• Interpreting Data
• What percentage of a mammalian cell is made up of
  water? How does this compare to the percentage of
  water in a bacterial cell?

• About 70 the percentages are the same.

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Compounds in Bacteria and Mammals
- Chemical Compounds in Cells

• Interpreting Data
• Which kind of compoundproteins or nucleic
  acidsmakes up the larger percentage of a
  mammalian cell?

• Proteins

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Compounds in Bacteria and Mammals
- Chemical Compounds in Cells

• Drawing Conclusions
• In general, how do a bacterial cell and mammalian
  cell compare in their chemical composition?

• They are similar, though mammalian cells have a
  lower percentage of nucleic acids, and bacterial
  cells have a lower percentage of lipids and fewer
  proteins.

23
Water and Living Things
- Chemical Compounds in Cells

• About two-thirds of the human body is water.

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Comparing and Contrasting
- Chemical Compounds in Cells

• As you read, compare and contrast carbohydrates,
  proteins, and lipids in a table like the one
  below.

Type of Compound
Elements
Functions
Store and provide energy and make up cellular
parts
Carbon, hydrogen, oxygen
Carbohydrate
Make up much of the structure of cells and speed
up chemical reactions
Carbon, hydrogen, oxygen, nitrogen, and sometimes
sulfur
Protein
Carbon, hydrogen, oxygen
Lipid
Store energy
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Links on Proteins
- Chemical Compounds in Cells

• Click the SciLinks button for links on proteins.

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End of SectionChemical Compounds in Cells
27
Ratios
- The Cell in Its Environment

• The concentration of a solution can be expressed
  as a ratio. A ratio compares two numbers. It
  tells you how much you have of one item in
  comparison to another. For example, suppose you
  dissolve 5 g of sugar in 1 L of water. You can
  express the concentration of the solution in
  ratio form as5 g1 L, or 5 g/L.
• Practice Problem
• Suppose you dissolve 7 g of salt in 1 L of water.
  Express the concentration of the solution as a
  ratio.

• 7 g1 L or 7 g/L

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A Selective Barrier
- The Cell in Its Environment

• The cell membrane protects the contents of the
  cell and helps control the materials that enter
  and leave.

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Diffusion
- The Cell in Its Environment

• In diffusion, molecules move from an area of
  higher concentration to an area of lower
  concentration.

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Osmosis
- The Cell in Its Environment

• In osmosis, water diffuses through a selectively
  permeable membrane.

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Passive and Active Transport
- The Cell in Its Environment

• Passive and active transport are two processes by
  which materials pass through the cell membrane.
  Active transport requires the cell to use its own
  energy, while passive transport does not.

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Building Vocabulary
- The Cell in Its Environment

• A definition states the meaning of a word or
  phrase. After you read the section, reread the
  paragraphs that contain definitions of Key Terms.
  Use all the information you have learned to write
  a definition of each Key Term in your own words.

Key Terms
Examples
selectively permeable
The cell membrane is selectively permeable, which
means that some substances can pass through the
membrane while others cannot.
The movement of dissolved materials through a
cell membrane without using cellular energy is
called passive transport.
diffusion
Diffusion is the process by which molecules move
from an area of higher concentration to an area
of lower concentration.
Active transport is the movement of materials
through a cell membrane using cellular energy.
osmosis
Osmosis is the diffusion of water molecules
through a selectively permeable membrane.
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More on Cellular Transport
- The Cell in Its Environment

• Click the PHSchool.com button for an
  activityabout cellular transport.

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End of SectionThe Cell in Its Environment
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Graphic Organizer
Organic Compounds
Carbo-hydrates
Nucleic acids
Lipids
Proteins
Amino acids
Fats, oils, and waxes
DNA
RNA
Starches
Sugars
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End of SectionGraphic Organizer