Biology Cell Structure

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BiologyCell Structure Function
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What is a cell?

• The smallest unit that is capable of performing
  life functions.
• After observing many cells, scientists came up
  with the cell theory
• All living things are made of 1 or more cells.
• Cells are the basic units of structure and
  function in organisms.
• All cells come from existing cells.

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Cell Size

• To function efficiently, cells must be small.
  Why?
• If a cell is the shape of a cube and has 1 mm
  sides, calculate the surface area of the cube
  using the formula 6S2. Also, calculate the
  volume using the formula S3. What is the surface
  area to volume ratio?
• Do the same calculations for a cell having 2 mm
  sides.
• What happens to the SA/volume ratio as the cell
  gets bigger? Why is this bad?

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2 Main Cell Types

• Prokaryotic

• Eukaryotic

• Originated approximately 1.5 billion years ago
• 2-100µm typical plant/animal cell is 10-50µm
• Organized- Have a nucleus and other organelles
  (structures that carry out specific functions for
  the cell)
• DNA is in the form of chromosomes
• Example- animal and plant cells

• Originated approximately 3.5 billion years ago
• 0.5- 2µm (µ is the symbol for micro which means
  1/1,000,000
• Simple- no nucleus nor other special compartments
• Single, circular DNA molecule
• Example- bacterium

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Prokaryotic Bacterial Cell
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Eukaryotic Plant Cell
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Eukaryotic Animal Cell
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Characteristics of ALL Cells

• All pro and eukaryotic cells have the following
• Cell membrane- An outer boundary which is also
  called the plasma membrane
• Cytoplasm- The interior of a cell just the
  liquid is called cytosol.
• Cytoskeleton (microtubules/microfilaments)-
  Protein filaments (thread-like structures) that
  are important in cell movement, shape and
  division
• Ribosomes- Structures that do not have a membrane
  and make proteins
• DNA- hereditary information

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Eukaryotic Organelles
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Organelles that Surround the Cell

• Cell membrane- Selects what can enter and leave
  the cell. More about this later!
• Cell wall
• Most commonly found in plant cells and bacteria-
  NOT IN ANIMAL CELLS!
• Surrounds the cell membrane and provides
  structure and support
• Made of cellulose- long carbohydrate chain
• Cilia- Short, numerous hairs that move the cell
  and/or substances outside the cell
• What human cells have cilia?

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• Flagella- Long tail(s) that moves the cell and/or
  substances outside the cell
• Both cilia and flagella are made of protein
  filaments like the cytoskeleton.
• What human cell has a flagellum?

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Organelles inside the cell

• Nucleus
• Directs the cells activities
• Houses DNA
• Houses the nucleolus
• where ribosomes are made
• Surrounded by a double membrane called the
  nuclear envelope
• controls what exits the nucleus like ribosomes
  and RNA
• has openings called nuclear pores

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• Endoplasmic reticulum
• System of membranes that move proteins around
  inside the cell- intracellular highway
• Can be smooth or rough
• rough has ribosomes attached to it and smooth
  does not
• ribosomes can also be found in the cytosol
• Golgi apparatus
• Flattened sacs
• Processes proteins into vesicles (membrane bound
  sacs)

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• Mitochondria
• Produces ATP- form of energy that can be used by
  the cell. What cells of the body have lots of
  mitochondria?
• Has a double membrane
• Outer membrane is smooth and the inner membrane
  (cristae) is folded.
• Has its own DNA
• Chloroplast
• In plants, some protists and some bacteria- NOT
  IN ANIMAL CELLS!
• Where photosynthesis occurs
• Has its own DNA and a double membrane

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Mitochondria
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Chloroplast
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• Lysosome
• Spherical organelle where digestion occurs
• Remove the web between fingers of a fetus
• Usually in animal cells
• Central Vacuole
• Large
• Stores water, nutrients and waste
• Only in plant cells
• Animal cells have vacuoles- but not central
  vacuoles

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Typical Animal Cell
http//web.jjay.cuny.edu/acarpi/NSC/images/cell.g
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Typical Plant Cell
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How do animal and plant cells differ?

• Animal

• Plant

• Spherical
• Might have flagella or cilia

• Rectangular
• Have a cell wall
• Have chloroplasts
• Have a central vacuole

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Evolution of the Eukaryotic Cell

• A possible explanation for how eukaryotic cells
  came into existence is the endosymbiotic theory.
• Symbiosis is a relationship between organisms
  where every member benefits.
• The endosymbiotic theory states that chloroplasts
  and mitochondria were once prokaryotic bacteria.
  They entered a larger prokaryotic cell and all
  parties benefited.
• The chloroplast and mitochondria got extra
  protection and the larger cell developed the
  ability to make its own food and energy.

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Evidence of the endosymbiotic theory

• Both chloroplasts and mitochondria have their own
  circular DNA (like prokaryotic cells).
• Both chloroplasts and mitochondria have a double
  membrane.
• Mitochondria are approximately the size of
  bacteria.

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Game to Review Organelles