Cell Structure

1
Cell Structure Function
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Cells the basic units of life.

• The cell theory, set forth in the 1850s, says
  that
• All living things are composed of cells.
• The cell is the smallest unit that retains the
  properties of life.
• Under current conditions, all cells come from
  preexisting cells.

3
Question

• Which of the following statements is NOT part of
  the cell theory?
• All living things are composed of cells.
• All cells are surrounded by an outer membrane.
• The cell is the smallest unit that retains the
  properties of life.
• Under current conditions, all cells come from
  pre-existing cells.

All cells DO have an outer membrane (called the
plasma membrane), but this observation is not
considered part of the cell theory.
4
Light Microscope(LM)

• Shows the entire cell and its interior

5
Scanning Electron Microscope (SEM)

• Shows a cells surface structure

6
Transmission Electron Microscope(TEM)

• Shows internal details of a preserved cell

7
Question

• Biologists generally rely on the ________
  microscope to study the surface structures of
  cells and the ________ microscope to study the
  internal structure of cells.
• light electron
• light transmission electron
• scanning electron transmission electron
• transmission electron scanning electron

Specimens for both types of electron microscopes
must be killed and preserved before they can be
examined. For this reason, light microscopes are
still useful for observing living cells.
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Basic Cell Structure
9
Question

• Which of the following correctly labels the
  three major parts of the cell shown below?
• 1-nucleus, 2-cytoplasm, 3-plasma membrane
• 1-cytoplasm, 2-plasma membrane, 3-nucleus
• 1-plasma membrane, 2-nucleus, 3-cytoplasm
• 1-nucleus, 2-plasma membrane, 3-cytoplasm

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Internal Cell Structures

• Cell membranes divide the cytoplasm of eukaryotic
  cells into functional compartments called
  organelles.
• Organelle mini organs

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Plant Cell Structures
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Animal Cell Structures
13
Eukaryotic vs. Prokaryotic
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Internal Cell Membranes

• Organelle membranes physically separate important
  chemical reactions in the cytoplasm and allow
  them to take place in an orderly fashion.

15
Selective permeability

• Cell membranes are said to be selectively
  permeable membranes, meaning that they allow
  some, but not all, materials to simply pass
  through them.

16
Question

• Which of the following is NOT an accurate
  analogy for a cell membrane?
• a window screen
• the US Mexico border
• the Kansas Colorado border
• a university admissions department

The Kansas Colorado border is a permeable
barrieranyone can cross the border at any time.
All of the other barriers in the list are
selectively permeable because they allow some
things but not others to pass through.
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Membrane Composition

• A phospholipid bilayer forms the basic unit of
  the cell membrane.

18
Question

• Where in this diagram of a cell membrane would
  you expect to find the FEWEST water molecules?

A
The fatty acid tails of the phospholipids are
hydrophobic. They would repel any water
molecules that came into that area of the
membrane.
B
C
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Membrane Composition

• Proteins embedded in the bilayer help the cell
  transport materials in and out.
• Carbohydrate chains attached to some membrane
  proteins help the cell communicate with other
  cells.

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Structure of the Cell Membrane
21
Question

• What type of membrane molecules are responsible
  for cell-to-cell communication?
• lipids
• proteins
• phospholipids
• carbohydrates

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A Fluid Membrane

• The lipid molecules have hydrophilic
  (water-loving) heads and hydrophobic
  (water-hating) tails.
• Therefore, if you puncture a membrane, it will
  come together and seal itself.

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Cell Membrane Analogy

• The cell membrane is similar to the walls that
  surround a house.

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Both help protect the inside from the outside.
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A house needs a way of receiving fuel and power
from the outside. Supply lines pass through the
walls of the house to bring in these materials.
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A cell receives fuel and power from the outside
through protein channels in the membrane.
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Doors are sometimes needed to bring in food and
take out the trash.
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Channels in the membrane allow the cell to bring
in food and get rid of waste.
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People in a house also need to communicate with
the outside.
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Carbohydrates in the membrane allow the cell to
communicate with other cells.