Cells

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Chapter 2

• Cells

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Comparing Cells

• Cells differ in size and shape depending on their
  function
• Ex nerve cell needs to communicate between
  places, so it is a long cell
• Ex a muscle cell can contract and change its
  shape
• Two cell types
• Prokaryotic lack membrane-bound internal
  structures
• Eukayrotic contain membrane-bound internal
  structures

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Cell Organization

• Cell wall
• Tough, rigid outer coverings that protect the
  cell and give it shape
• Made of cellulose
• Only in plants, algae, fungi and most bacteria
• frame of a house
• Cell Membrane
• A protective layer around all cells
• Inside the cell wall, if it is present
• Allows food and gasses into the cell and waste
  products out of the cell
• the bouncer

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Cell Structures

• Cytoplasm
• A gelatin-like substance inside the cell membrane
• Medium for things to move about in the cell
• Cytoskeleton
• Scaffolding-like structure in cytoplasm which
  helps cell keep its shape
• Organelles
• Membrane bound structures inside eukaryotic cells
  that helps the cell perform life processes

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Cell Structures

• Nucleus
• Organelle that directs all cell activities
• Contains instructions for everything a cell does
  (within the DNA)
• foreperson

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Cell Structures

• Chloroplasts
• Organelles in plants and a few bacteria that help
  the organism make food
• Photosynthesis occurs here
• Mitochondria
• Organelles in all eukaryotes that release the
  energy from food and turn it into something the
  organism can use
• powerhouse

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Cell Structures

• Ribosomes
• Organelles that make proteins
• Produced in the nucleus
• Endoplasmic Reticulum (ER)
• Series of folded membranes from the nucleus to
  the cell membrane
• Moves materials around in a cell
• Two types of ER
• Rough ribosomes are attached
• Smooth no ribosomes attached
• Material movement and lipid processing

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Cell Structures

• Golgi Bodies
• Sort proteins and other cellular substances and
  package them into membrane-bound structures
  called vesicles
• post office
• Vacuoles
• Organelles that serve as temporary storage for
  materials
• Can be water, waste products, food, etc.
• Vacuoles make up most of the volume of plant cells

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Cell Structures

• Lysosomes
• Organelles that contain digestive chemicals that
  help break down food molecules, cell wastes, and
  worn-out cell parts
• recycler

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From Cell to Organism

• Cell
• Tissues
• Groups of similar cells working together on one
  job
• Ex muscle tissue, nervous tissue
• Organ
• Different types of tissues working together
• Ex muscle, brain

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From Cell to Organism

• Organ System
• A group of organs working together on a
  particular function
• Ex muscular system, nervous system
• Organism
• All of organ systems working together to create a
  particular organism

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Review Questions

1. Explain the important role of the nucleus in the
   life of a cell.
2. Compare and contrast the energy processing
   organelles.
3. Why are digestive enzymes in a cell enclosed in a
   membrane-bound organelle?
4. How are cells, tissues, organs and organ systems
   related?
5. How is the cell of a one-celled organism
   different from the cells in many-celled
   organisms?
6. What are some differences between plant and
   animal cell?
7. List 3 organelles and give their functions.

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Early Microscopes

• Dutch reading glass maker put two lenses at ends
  of a tube (1500s)
• Larger image
• Antonie van Leeuwenhoek (Dutch fabric merchant)
• First simple microscope (p. 50 in book)
• Could magnify up to 270 times

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Modern Microscopes

• Use lenses to bend light
• A simple microscope has one lens while a compound
  microscope (what we have here) has mulitple
  lenses
• Ex one lens at 10x 10 times bigger
• Two lenses at 10x 100 times bigger
• Stereomicroscopes have two eyepieces, which
  create a three-dimensional image

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Electron Microscopes

• Use a magnetic field inside a vacuum to bend
  electronic beams
• Scanning Electron Microscope (SEM) bounce
  electrons off the sample to create a 3-D image
• Transmission Electron Microscope (TEM) send
  electrons through a sample to see internally
• Either way, electons then end up on a screen to
  produce an image (kind of like older TVs)

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Cell Theory

• 1665, Robert Hooke looked at cork under a
  microscope
• Made of little boxes he named cells
• 1830s, Matthias Schleiden studied plant parts
• Concluded all plants are made of cells

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Cell Theory

• Theodor Schwann looked at animal cells
• Concluded all animals are made up of cells
• Rudolf Virchow
• Said that cells come from other cells that
  already exist

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Cell Theory

• All organisms are made up of one or more cells
• The cell is the basic unit of organization in
  organisms
• All cells come from pre-existing cells

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Review Questions

1. Explain why the invention of the microscope was
   important in the study of cells.
2. What is stated in the cell theory?
3. What is the difference between a simple
   microscope and a compound microscope?
4. What was Virchows contribution to the cell
   theory?
5. How do electron microscopes work?
6. Why would it be better to look at living cells
   rather than dead cells?

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Cell Processes

• Passive Transport the movement of substances
  through a cell membrane without the use of energy
• Diffusion or Osmosis
• Active Transport the movement of substances
  through the cell membrane using energy
• Endocytosis Exocytosis vesicles transport
  large materials into (endocytosis) and out of
  (exocytosis) the cell

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Cell Processes

• Photosynthesis
• The process plants and other organisms use to
  convert sunlight energy into chemical energy or
  sugars to be used as food
• Respiration
• The process in which chemical reactions break
  down food molecules into simpler substances and
  release stored energy
• Fermentation
• Cells that do not have enough oxygen for
  respiration use this process to release some of
  the stored energy in glucose molecules

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Cell Processes

• Cell Division process where one cell splits
  into two cells
• Mitosis process in which the nucleus divides to
  form two identical nuclei
• Four stages Prophase, Metaphase, Anaphase,
  Telophase
• Happens during growth of organism or during
  asexual reproduction
• Meiosis process in which the nucleus divides to
  form cells with half the genetic material of the
  original
• Eight Stages Prophase I, Metaphase I, Anaphase
  I, Telophase I, Prophase II, Metaphase II,
  Anaphase II, Telophase II
• Happens when an organism produces gametes (sex
  cells) for sexual reproduction

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Review Questions

1. What is active transport?
2. What are the two main types of passive transport?
3. How do cells get large materials out?
4. What is photosynthesis?
5. What is respiration?
6. What is mitosis and when does it happen?
7. What is meiosis and when does it happen?