cells. by the end of this class you should understand: the three major parts of all cells the...
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By the end of this class you should understand:
• The three major parts of all cells• The primary structures found in prokaryotic
and eukaryotic cells• The major organelles found in all living things• The basic functions of membrane-bound
organelles found in eukaryotes
Parts of a Cell
• There are two major types of cells– Prokaryotic cell– Eukaryotic cell
• All cells have three parts:– Cell membrane– Genetic information– Cytoplasm
Prokaryotic Cells
• Prokaryotic cells are cells without a nucleus– All genetic info is bundled
but not separated from cytoplasm
• All known prokaryotes are single-celled bacteria– Prokaryotic cells are tiny!
Eukaryotic Cells• If every cell was a
company:– Prokaryotic cells are a 1-
man startup in a garage– Eukaryotic cells are a large
corporation
• Eukaryotic cells have organelles which each perform separate jobs
• Genetic info stored in nucleus
Eukaryotes
• Some eukaryotes are single celled organisms– One eukaryotic cell performs
all functions of life
• Some eukaryotes are multicellular– The different cells specialize in
different tasks– Each cell is still individually
alive!
Key Parts of Eukaryotic Cells
• Nucleus– Stores genetic information
• Cytoplasm– Composed of a liquid called
cytosol– Filled with various membrane-
bound organelles
• Cell Membrane– Often referred to as plasma
membrane
Key Parts of Prokaryotic Cells
• Cell membrane, nucleic acids, and cytoplasm– Same as eukaryotes
• Cytoplasm is much simpler– Prokaryotes have NO
membrane-bound organelles– They do have a cytoskeleton
and ribosomes!
Cell Membrane
• The cell membrane is a flexible, selectively permeable (or semipermeable) barrier
• Boundary of cell, visible under microscope only as border of cell
• NOT the same as a cell wall– Cell wall is rigid
Cell Membrane Structure• The cell membrane is
composed of phospholipids– Hydrophilic head,
hydrophobic tail
• The nonpolar tails orient themselves into a hydrophobic zone surrounding the cell– Essentially a thin bubble of oil
Cell Membrane Proteins
• Proteins are macromolecules constructed from many linked amino acids
• Some amino acids are hydrophobic and so mix with the inside of the cell membrane
• These proteins sit inside the cell membrane
Membrane Protein Functions
• Cell membrane proteins serve many vital functions:– Markers– Receptors– Channels
• Transporting things in and out of cells is a key function of life!– Will cover this more
tomorrow
Parts of the Eukaryotic Cell(organelles)
Nucleus Cell membrane Cytoskeleton Cytoplasm Mitochondria Ribosome Endoplasmic Reticulum Golgi Apparatus
Nucleus: The Library
The nucleus stores all the cell's genetic information in massive molecules of DNA
The DNA molecules are packed into many pairs of chromosomes
When a protein is needed, signals enter the nucleus and cause copies of the appropriate genes to be made with RNA
Key Nucleus Facts:
Every complete human cell has one nucleus Exception: red blood cells have no nucleus (also
have no other membrane-bound organelles) Exception: muscle cells are many cell fused
together and so have many nuclei Every nucleus has the complete human genome The nucleus has its own envelope to keep
unwanted things out
Cytoskeleton: The City Streets Every cell has long strands
of different kinds of proteins running through it
When organelles are moved they move along the cytoskeleton
If the cell moves under its own power it uses the cytoskeleton as well
Key Cytoskeleton Facts:
There are several different types of fibers and they have different functions
All cells must produce each of these fibers These fibers are made of different kinds of
proteins (keratin, collagen, actin, myosin, etc) If the genes for any of these fibers are no
good, no cells can form and the organism will never develop, grow or be born
This makes these genes essential for life
Cytoplasm: The Marketplace The liquid of the cell is called
cytosol Cytosol plus the organelles are
called cytoplasm All the cell's chemical reactions
and growth take place here Many exchanges are made Many chemicals are stored
in vesicles in the cytoplasm
Key Cytoplasm Facts:
Cytosol is a clear liquid but it is filled with salts and sugars
Cytoplasm is held within the cell membrane If the cell membrane develops a hole,
cytoplasm can leak out and the cell can die If the cell membrane bursts all at once, this is
called lysis and is instant cell death
Ribosome: The Machine Shop
Site of protein synthesis Some are free floating in
cytoplasm Some are attached to
membranes called the endoplasmic reticulum
Made with a combination of protein and RNA
Probably the first structure in the original cells
Key Ribosome Facts Ribosome is the site for proteins to be synthesized
That process will be discussed next week Cytoplasmic ribosomes make the cytoskeleton and
cell enzymes Rough endoplasmic reticulum produces proteins
that will enter the membrane or leave the cell Smooth endoplasmic reticulum is for synthesis of
other macromolecules such as lipids
Golgi Apparatus: The Shipping Center
• Vesicles from the endoplasmic reticulum are organized here
• Different vesicles have different destinations– The chemical reactions
that determine where these vesicles go occur here
Key Golgi Facts
• The Golgi manipulates cell membrane material into many types of vesicles– Peroxisomes contain peroxides– Lysosomes contain destructive enzymes (that can
lyse chemicals or even other cells)– Secretory vesicles are designed for exocytosis
(they will secrete their contents)
Mitochondria: The Power Plant
• Mitochondria (singular: mitochondrion) produce the cell's supply of energy molecules– Cells use a molecule called
ATP– Made using the energy from
blood sugar
• Must have oxygen to work– Process that requires oxygen
is called aerobic
Key Mitochondria Facts: Mitochondria were once bacteria
Captured/adopted by animal cells billions of years ago and now we work together
Mitochondria must have oxygen to burn sugar Produce CO2 as a waste product This is why we breathe in oxygen and breathe
out carbon dioxide Mitochondria sustain our high metabolic rate
Cyanide blocks mitochondrial activity, which is why it is a lethal poison to us
Mitochondria Activity
• Mitochondria perform aerobic respiration (requiring O2)– This is the key part of cellular respiration that will
be covered next week
• Prokaryotes have no membrane-bound organelles, therefore they do not have mitochondria– Some bacteria are aerobic, which means they
perform the same processes as a mitochondrion!
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