cell theory and structure - biology
TRANSCRIPT
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Cell Theory and Structure
Discoveries
What are Cells?
Cell Theory
Cell Structures
Organelles
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Discoveries
What he saw reminded him of the rooms in a monastery, so he called what he saw under the microscope a “cell” (Latin for ‘room’)
In 1665 Robert Hooke observed a thin slice of cork from an oak tree
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Discoveries
He saw living creatures that we now call single celled organisms
In 1670 Anton van Leeuwenhoek used the first “real” microscope to view pond water
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What are cells?
• Cells are the smallest unit of life that can carry out all the functions of a living organism
• Cells were not discovered until the invention of the microscope
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What are cells?
• Some living organisms are unicellular (only made of only 1 cell)
• They are the smallest of all living organisms
−Examples: some bacteria, many protists
−These are what Leeuwenhoek noticed under the microscope in 1670
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What are cells?
Some living organisms are multicellular (made of many cells)
Examples: Plants, Animals, Fungi
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What are cells?
Shape is related to Function
Blood Cell-hemocyte; round to move through vessels
Nerve-neuron; long to carry message to spinal cord
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Cell Theory
• M. Schleiden 1838, botanist, “all plants are made of cells”
• T. Schwann 1839, zoologist, “all animals/organisms are made of cells”
• R. Virchow 1855, physician, “all new cells come from existing cells” (biogenesis)
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Cell Theory
1. Cells are the basic units of all life
2. All organisms are made of one or more cells
3. All new cells come from existing cells
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Cell Structure
• Many components make up a cell and carry out specific activities
• Each component works together with the others to keep the cell functioning
• These components are called organelles
Just as many organs work together to make your body function, organelles work together to make a cell function
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• All cells have cell membranes
• All cells have genetic material:
DNA and ribosomes
• All cells have cytoplasm:
the interior portion of the cell
Common features in cells
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Types of cells: Prokaryotic
• have genetic material but no nucleus.
• NO membrane bound organelles except
ribosomes
Simplest cellular organisms. Example: bacteria
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Types of cells: Eukaryotic
• More complex, organized cells
• Has a true nucleus and other
organelles
• About 10X bigger than prokaryotic
cells
–Ex. - plant and animal cells
• The cells in your body are eukaryotic!
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Organelles: Cell Membrane
Structure: Made of phospholipids and proteins
• Phospholipid bi-layer
• Semipermeable (selectively permeable)
• Hydrophilic (H2O loving) head
• Hydrophobic
(H2O fearing) tail
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Organelles: Cell Membrane
Function: maintain homeostasis
• Controls what enters and leaves
• Boundary separating the cell from its environment
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Organelles: Cell Wall
Structure:
• Found only in plant cells
• composed of proteins and cellulose
Function:
• Provides support and protection
• Helps maintain square shape
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Organelles: Cytoplasm
Structure:
• Jelly like base throughout the cell
• consists of mainly water and cytosol (an organic compound)
• contains the cytoskeleton
Function:
• Contains or “suspends” organelles inside the cell
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Organelles: Cytoskeleton
Structure
• composed of protein fibers
– Actin fibers: contract and expand to give the cell flexibility
– Microtubules: transport information from nucleus to other parts of the cell (like neurons)
– Intermediate fibers: framework of metabolic pathways for ribosomes/enzymes
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Organelles: Cytoskeleton
Function
•provides support and a place to anchor other structures
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Organelles: Nucleus
Structure:
• Found in the cytoplasm
• Contains the genetic material (chromosomes made of DNA & proteins)
• Surrounded by a nuclear envelope (double membrane)
• Contains the nucleolus that makes ribosomes
Function:
• Control headquarters for the cell (brain)
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Organelles: Nucleolus
• Located inside the nucleus
Structure
• Knot of chromatin
Function
• Produces ribosomes
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Organelles: Ribosomes
Structure • spheres composed of RNA and protein Function • site of protein synthesis
– Free ribosomes make proteins that remain inside the cell
– Attached ribosomes make proteins that become part of the cell or are exported from the cell (usually attached to the ER)
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Organelles: Endoplasmic Reticulum
• Rough ER: has ribosomes attached
• Smooth ER: does NOT have ribosomes
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Organelles: Rough ER
Structure:
• Network of folded membranes near nucleus
• Contains ribosomes on surface
Function:
• Transports proteins that were made by the attached ribosomes through the cell to the golgi
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Rough Endoplasmic
Reticulum (ER)
Ribosomes-
make proteins
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Organelles: Smooth ER
Structure:
• Network of folded membranes throughout cell
• Contains NO ribosomes on surface
Function:
• Makes lipids and breaks down toxic substances
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Organelles: Golgi
Structure
• Closely stacked, flattened membrane sacs
• Found in the cytoplasm near nucleus
Function
• Stores, packages, and transports products inside for use outside
• Releases vesicles (a bit of the golgi pinched off) for transport of stored materials.
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Golgi Apparatus-packaging
and distribution center of the
cell.
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Organelles: Vesicles
Structure
• bits of membrane from the plasma membrane or from the golgi
• found inside or outside of the plasma/cell membrane
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Organelles: Vesicles
Function
• Vesicles fuse with the cell membrane
• may be used to release or transport chemicals in or out of the cells:
– Exocytosis out of the cell
– Endocytosis into the cell
• Transports chemicals to lysosomes or vacuole
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Organelles: Lysosomes
Structure
• found only in animal cells
• sac-like
• contain digestive enzymes
Function
• digests food particles and old organelles
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Organelles: Vacuole
Structure
• Located in cytoplasm
• Sac of fluid surrounded by a membrane
• Plant cells have one large central vacuole
• Animal cells have many small vacuoles
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Organelles: Vacuole
Function
• Stores water, ions and some nutrients
• Help plant cells maintain turgor pressure
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Organelles: Mitochondria
• Found in plant and animal cells
Structure
• A complex matrix of folded membranes to increase surface area
– Chemical processes in organisms occur across membrane surfaces
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Function
• Powerhouse of the cell
• Converts stored energy (glucose) into useable energy (ATP)
– Glucose is a product of photosynthesis
– ATP is a product of cellular respiration
Organelles: Mitochondria
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Organelles: Chloroplast
Structure
• Found only in plant cells (and some
protists)
• Double phospholipid bilayer
– Stacks = grana
– Non stacked area = stroma
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Organelles: Chloroplast
Function
• Capturing radiant energy and converting it to chemical energy during photosynthesis
• Chlorophyll is the green pigment that traps the energy from the sun
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Organelles: Flagella
Structure
• long whip-like tail
Function
• Locomotion (movement)
• one big wave motion will cause a large movement
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Organelles: Cilia
Structure
• Surrounds outside of the cell
• short hair-like
Function
• locomotion (movement)
• tiny flutters of movement
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Organelles: Centrioles
Structure
• Found only in animal cells
• Made of protein fibers
Function
• Aid in the division of chromosomes during mitosis