introduction to the cell ch.3 in online textbook
TRANSCRIPT
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Introduction to the Cell
Ch.3 in online textbook
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Discovery of Cell
• Robert Hooke – looked at cork cells and saw tiny units of life named them cell.
• Leeuwenhoek – invented a microscope to look at cells.
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The Cell Theory
• Schwann and Schleiden• Proposed:– All living things are made of cells.– Basic building blocks of life.Virchow discovered:- Cells come from other cells.
- These scientists came up with the cell theory.
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Cell Theory states:
• All organisms are made of one or more cells.• All the life functions of organisms occur within
cells.• All cells come from already existing cells.
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Microscopes
• Light microscopes – view organisms by shining light through them. Must be a small slice of the organism.
• Electron microscope – uses a beam of electrons to observe extremely small objects.– Allowed scientists to see
organelles.
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Cell size• To carry out cell functions they must be able
to quickly pass substances into and out of cell.• Anything that enters or leaves a cell must
cross its outer surface.• This limits how large a cell can be.
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Surface Area : Volume
• The larger the cube (cell) the smaller surface area to volume ratio.
• Cells can’t get too large because they need enough surface area on the cell membrane to allow substances in and out.
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Cell Shape
• Cells with different functions have different shapes.
• Function determines shape.
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Parts of all cells• The plasma membrane (also called the cell membrane)
is a thin coat of lipids that surrounds a cell. It forms the physical boundary between the cell and its environment, so you can think of it as the “skin” of the cell.
• Cytoplasm refers to all of the cellular material inside the plasma membrane. Cytoplasm is made up of a watery substance called cytosol and contains other cell structures such as ribosomes.
• Ribosomes are structures in the cytoplasm where proteins are made.
• DNA is a nucleic acid found in cells. It contains the genetic instructions that cells need to make proteins.
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Two Types of Cell
• Prokaryotic cells are cells without a nucleus. The DNA in prokaryotic cells is in the cytoplasm rather than enclosed within a nuclear membrane.
• Eukaryotic cells are cells that contain a nucleus.
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Organelle
• Structure within the cytoplasm that performs a specific job in the cell.
Organelles:Mitochondria ChloroplastNucleus LysosomeVacuole Cell membraneSmooth Endoplasmic ReticulumRough Endoplasmic Reticulum Golgi Apparatus
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Viruses
• Contain DNA• Lack the other parts
shared by all cells like, plasma membrane, cytoplasm, and ribosomes.
• Viruses are not cells.• They are not considered
living, but its debatable in the science community.
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Cell Structures
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Plasma Membrane
• Forms a barrier between the cytoplasm inside the cell and the outside.
• Protects and supports the cell and controls everything that enters and leaves the cell.
• Allows only certain substances to pass through, while keeping others in or out.
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Phospholipid bilayer
• Molecule with a head and two tails.• Head “loves” water, hydrophilic.• Tails “hate” water, hydrophobic.
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Crash course – the cell
• https://www.youtube.com/watch?v=cj8dDTHGJBY