BiologyUNIT 5- CELLS
History of Cell Theory
Until the invention of microscopes, scientists did not
know the world of microorganisms that existed.
This research was pioneered by Anton Van
Leeuwenhoek in the 1600’s.
We now have compound light microscopes which can
magnify objects up to 1500 times.
The History of Cell Theory
Robert Hooke also studied in the 1600’s
Studied oak bark and found many small
compartments.
Named the compartments cells after the rooms monks
lived in.
Parts of the Cell Theory
All organisms are made of one or more cells.
The cell is the basic unit for structure of living things.
All cells come from pre-existing cells.
Electron Microscopes
Electron microscopes use a beam of electrons to
magnify objects up to 500,000 times.
2 Cell Types
Prokaryote
Mostly unicellular
No organelles
Circular DNA
Smaller of the 2
Eukaryote
Mostly Multi-cellular
Membrane bound organelles
DNA contained in Nucleus
Larger of the 2
Plasma Membrane
Cells need nutrients and it is the job of the plasma
membrane to allow these nutrients to come into the
cell.
This is done through selective permeability.
Selective permeability allows some molecules to come
in while leaving others out.
Structure of the Plasma Membrane
Made of a phospholipids.
In a phospholipid, a fatty acid is replaced by a
phosphate.
Phospholipids form 2 layers
Phospholipid Bilayer
Phosphate is polar while the lipid sections are nonpolar.
The polar phosphate is what lets water in and out of the
cell.
Because the non-polar lipids do not like water, they fold
to the inside of the membrane.
Cell Barriers
Cell walls: Rigid layer outside plasma membrane.
Provide extra support and structure.
Not found on animal cells.
Organelles for Cell Control
Nucleus: Contains chromatin, where the strands of DNA
are kept. Also bound in a membrane.
Nucleolus: Inside nucleus, makes ribosomes.
Ribosomes: Organelles that use directions from DNA to
make protein.
Cytoplasm: Clear, gelatinous fluid inside a cell. Allows
for transport within the cell.
Organelles for Assembly and Transport
Endoplasmic Reticulum (ER): Site of cellular chemical
reactions, most importantly protein synthesis.
Rough: Ribosomes attached
Smooth: No ribosomes attached
Golgi Body: (Cellular UPS) Packs newly made proteins
into packages called vesicles, to be sent to the
appropriate location in the cell.
Organelles for Storage
Vacuole: Membrane bound compartments for
temporary storage of materials.
Store food, enzymes, and other materials needed by a
cell.
Lysosomes: Organelles that contain digestive enzymes.
Digest worn out organelles, food particles, bacteria or
viruses.
Organelles Used for Energy
Chloroplasts: Used in plants and green algae to
capture light energy and turn it into sugar.
Mitochondria: Places where cellular respiration takes
place.
Produces ATP (cellular energy)
Support and Locomotion
Cytoskeleton: Support structure within the cytoplasm.
Cilia: Hair-like projections used for locomotion.
Flagella: Whip-like projections used for locomotion.
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