UNIT II: Cells
A. Living Things
➢ All living things are composed of cells
➢ According to cell theory, the cell is life’s basic unit of structure and function
○ Cell is the smallest unit of living material that can carry out all the activities necessary for
life
➢ Why not be a GIANT CELL?
○ Specialization
○ Must maintain high surface area:volume ratio to allow cellular exchanges across the
membrane!
■
B. Types of Cells and Organelles
➢ Invention of electron microscopes allowed scientists to figure out the exact functions of cells
➢ Prokaryotic cells
○ Only in domains Bacteria and Archaea
○ Smaller
○ Simpler
○ Circular DNA
■ In nucleoid region
■ NO NUCLEUS
○ Cell wall
■ Made up of peptidoglycans that surround a lipid layer called the plasma
membrane
○ Filled with semi-fluid cytosol
○ Have ribosomes
○ Can have flagella
■ Long tails used for motility
○ May have a thick capsule outside their cell wall to give them extra protection
○ No membrane-bound organelles
➢ Eukaryotic cells
○ More complex
○ Organized into smaller structures called organelles
○ DNA in nucleus bounded by a membranous nuclear envelope
○ Cytoplasm between plasma membrane and nucleus
C. Organelles
➢ Each organelle has its own special task
➢ Plasma Membrane
○ Outer envelope
○ Complex
○ Phospholipid bilayer
○ Encloses vacuole
○ Regulates movement in/out of cell
○ Flexible due to weak bonds holding it together
, ■ Higher fluidity when more phospholipids have double bonds (causing a bend in
the tail) since the molecules aren’t as packed
○ Semipermeable
■ Only small hydrophobic molecules can pass through unaided
■ Anything large/hydrophilic must pass through active/passive transport
■ Water can’t move through easily due to its polarity
○ Fluid-mosaic model
■ Peripheral proteins are loosely associated with the lipid bilayer
● Located on inner/outer surface of membrane
■ Integral proteins are firmly bound into the plasma membrane
● Amphipathic to allow anchoring
● Some extend all the way through the membrane
■ Membrane peppered with different proteins/carb chains
○ Adhesion proteins
■ membrane proteins form junctions between adjacent cells
○ Receptor proteins
■ Serve as docking sites for arrivals at the cell
■ Ex. hormones
○ Transport proteins
■ Form pumps that use ATP to actively transport solutes across the membrane
■ Hydrophilic channel that certain molecules/ions can use as a tunnel
■ Specific for substance it moves
○ Carrier Proteins
■ Bind to molecules and change shape to sh1uttle them across the membrane
○ Channel proteins
■ Selectively allow the passage of ions/molecules
A. Living Things
➢ All living things are composed of cells
➢ According to cell theory, the cell is life’s basic unit of structure and function
○ Cell is the smallest unit of living material that can carry out all the activities necessary for
life
➢ Why not be a GIANT CELL?
○ Specialization
○ Must maintain high surface area:volume ratio to allow cellular exchanges across the
membrane!
■
B. Types of Cells and Organelles
➢ Invention of electron microscopes allowed scientists to figure out the exact functions of cells
➢ Prokaryotic cells
○ Only in domains Bacteria and Archaea
○ Smaller
○ Simpler
○ Circular DNA
■ In nucleoid region
■ NO NUCLEUS
○ Cell wall
■ Made up of peptidoglycans that surround a lipid layer called the plasma
membrane
○ Filled with semi-fluid cytosol
○ Have ribosomes
○ Can have flagella
■ Long tails used for motility
○ May have a thick capsule outside their cell wall to give them extra protection
○ No membrane-bound organelles
➢ Eukaryotic cells
○ More complex
○ Organized into smaller structures called organelles
○ DNA in nucleus bounded by a membranous nuclear envelope
○ Cytoplasm between plasma membrane and nucleus
C. Organelles
➢ Each organelle has its own special task
➢ Plasma Membrane
○ Outer envelope
○ Complex
○ Phospholipid bilayer
○ Encloses vacuole
○ Regulates movement in/out of cell
○ Flexible due to weak bonds holding it together
, ■ Higher fluidity when more phospholipids have double bonds (causing a bend in
the tail) since the molecules aren’t as packed
○ Semipermeable
■ Only small hydrophobic molecules can pass through unaided
■ Anything large/hydrophilic must pass through active/passive transport
■ Water can’t move through easily due to its polarity
○ Fluid-mosaic model
■ Peripheral proteins are loosely associated with the lipid bilayer
● Located on inner/outer surface of membrane
■ Integral proteins are firmly bound into the plasma membrane
● Amphipathic to allow anchoring
● Some extend all the way through the membrane
■ Membrane peppered with different proteins/carb chains
○ Adhesion proteins
■ membrane proteins form junctions between adjacent cells
○ Receptor proteins
■ Serve as docking sites for arrivals at the cell
■ Ex. hormones
○ Transport proteins
■ Form pumps that use ATP to actively transport solutes across the membrane
■ Hydrophilic channel that certain molecules/ions can use as a tunnel
■ Specific for substance it moves
○ Carrier Proteins
■ Bind to molecules and change shape to sh1uttle them across the membrane
○ Channel proteins
■ Selectively allow the passage of ions/molecules
