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The Scientists…
Robert Hooke (1665) Viewed cork under a
microscope Called the chambers he
saw “cells” Anton van
Leeuwenhoek (1674) First to see living
organisms in a drop of water
The Scientists…
Matthias Schleiden (1838)All plants are made of cells
Theodor Schwann (1839)All animals are made of cells
Rudolf Virchow (1855)All cells come from preexisting
cells
The Cell Theory
All living things are composed of cells
Cells are the basic units of structure and function in living things
New cells are produced from existing cells
Unicellular vs. Multicellular
Unicellular – single-celled organism
Multicellular – many-celled organismCell specialization – cells are
specialized to perform certain functions
Cells → Tissues → Organs → Organ systems → Organism
Prokaryotes vs. Eukaryotes Prokaryotes
Have a cell membrane & cytoplasm, but do not have a nucleus
Ex. Bacteria such as E.coli Eukaryotes
Have a nucleus, cell membrane, cytoplasm & organelles
Ex. Plants, Animals, Fungi
Basic Cell Structures
Cell membrane – thin, flexible barrier around the cell; protects the cellPresent in all cells
Cytoplasm – material inside the cell membrane (not including the nucleus)Prokaryotes & Eukaryotes
Cell Wall
Found in many organisms, including plants, algae, fungi and nearly all prokaryotes
Not found in animal cells Lies outside the cell membrane Main function is to provide
support & protection for the cell
Nucleus
Almost all eukaryotic cells, including plants and animals have a nucleus
Prokaryotes do not have a nucleus
Controls most cell process and contains the DNA
Nucleolus and Nuclear Envelope
Nucleolus: Inside the nucleusWhere ribosomes are made
Nuclear Envelope:Double-membrane layer around
the nucleusAllows material to move into and
out of the nucleus
Cytoskeleton
Found in all eukaryotic cells Not found in prokaryotes A network of protein filaments
that helps the cell maintain its shape
It also is involved in cell movement
Ribosomes
Found in all cells Main function is to make
proteins Can be found floating in the
cytosol or attached to endoplasmic reticulum
Endoplasmic Reticulum (ER)
Found only in eukaryotic cells Where components of the cell
membrane are assembled Two kinds: Smooth ER & Rough
ERSmooth ER: no ribosomes; makes
lipidsRough ER: has ribosomes; involved
in making proteins
Golgi Apparatus
Found only in eukaryotic cells
Enzymes attach carbohydrates & lipids to proteins
Send proteins to their final destination
Lysosomes
Found in animal cells only Break down lipids,
carbohydrates & proteins from food into particles that can be used by the cell
Also break down “dead” organelles
Vacuoles
Not found in prokaryotes Animal cells have small or no
vacuoles Plant cells have a large central
vacuole Store materials such as water,
salts, proteins & carbohydrates
Chloroplasts
Found in all plant cells Some prokaryotes have them,
but most do not Use the energy from sunlight to
make energy-rich food molecules during photosynthesis
Cell Membrane
Regulates what enters and leaves the cell (selectively permeable)
Provides protection and support Lipid bilayer – two layers of lipids
Proteins run through the layersCarbohydrates are attached to
some of the proteinsFluid Mosaic Model
Diffusion
Molecules move from an area of high concentration to an area of low concentration
Movement continues until equilibrium is reached
Many substances move across the membrane by diffusion
Does not require energy (passive transport)
Osmosis
The diffusion of water Isotonic – equal concentration
Nothing happensHypertonic – higher concentration
Water moves out of the cellHypotonic – lower concentration
Water moves into the cell No energy is required
Osmotic Pressure
In pure water, an animal cell would burst
Plant cells are protected by their cell wall
Some freshwater organism have special structures like contractile vacuoles to get rid of extra water
Facilitated Diffusion
Some molecules cannot cross the membrane without help
Some of the proteins in the membrane form protein channels
Materials still move from higher to lower concentrations
No energy is required
Active Transport
Materials move from lower concentration to higher concentration
Requires an input of energy
Works kind of like a pump
Transport of Large Amounts
Endocytosis – movement into the cellPhagocytosis – “cell eating” – solid
particlesPinocytosis – “cell drinking” –
particles dissolved in water Exocytosis – movement out of
the cell
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