im gonna put all my notes on IA so we can all read together lol and also so i dont have to flip between .doc files. thank you for your patronage


Cell Structure and Function
Historical Overview
• Robert Hooke
– 1600s
– First to view plant cells

Historical Overview
• Matthias Schleiden and Theodor Schwann
– Mid 1800s
– All living things composed of cells

Historical Overview
• Rudolf Virchow
– Cells arise only from other cells
– Theory of spontaneous generation challenged
Cell Theory
• Every organism is composed of one or more cells

• The cell is the smallest unit having the properties of life

• The continuity of life arises directly from the growth and division of cells
Cell Size
Cell Shape
Prokaryotic Organisms
• Single cells
• No nucleus or organelles
• Smaller, less complex




Surface to Volume
Volume increases faster than surface area





Basic Features of All Cells
• Plasma membrane
• Nucleus (or nucleoid)
• Cytoplasm

Plasma Membrane
• Cell membrane

• Encloses the cell

• Mediates interactions between the cell and its environment
Nucleus (nucleoid)
• Nucle = pit or kernel

• Control center of the cell

• Houses DNA
Cytoplasm
• Cyto = cell
• Plasm = shaped, molded

• Between cell membrane and nucleus

• Major functional area

• Site where most cellular activities occur
Nucleus
• Control center
– Computer
– Design department
– Construction boss
– Board of directors
• Nuclear envelope
• Nucleoli
• DNA + Nucleoplasm
• Nucleolus is the site of ribosome assembly
Nuclear Envelope
• Double membrane barrier

• Each membrane is a phospholipid bilayer

• Fluid-filled space between each membrane (perinuclear cisterna)

• Fuse – nuclear pores
– Allows transport of large molecules

• The nuclear envelope allows selective exchange of materials

• Chromatin contains DNA, which codes for the synthesis of proteins





Cytoplasm
• Cytosol
• Organelles
• Inclusions
Cytosol
• Viscous (thick fluid)
– Mostly water
• Semitransparent
• Suspension
– Organelles
– Inclusions
– Soluble proteins
– Salts
– Sugars

Organelles
• Metabolic machinery

• Specific functions
Inclusions
• Chemical substances

• Varies between types of cells
Organelles
• Endoplasmic reticulum
– Smooth
– Rough
• Golgi Body
• Ribosomes
• Mitochondria
• Lysosomes
• Vacuoles

• Central Vacuole
• Chloroplasts
• Plastids









Cytoskeleton
• Unique to eukaryotic cells

• This structure acts as both muscle and skeleton, for movement and stability

• The long fibers of the cytoskeleton are polymers of subunits

Cytoskeletal Elements
Microtubules
• Largest elements
• Composed of tubulin
• Arise from microtubule organizing centers (MTOCs)
• Microtubules act as a scaffold to determine cell shape, and provide a set of "tracks" for cell organelles and vesicles to move on
• Microtubules also form the spindle fibers for separating chromosomes during mitosis
• When arranged in geometric patterns inside flagella and cilia, they are used for locomotion

Microfilaments
• Composed of actin
– Most abundant cell protein
• Microfilaments' association with the protein myosin is responsible for muscle contraction
• Microfilaments can also carry out cellular movements including gliding, contraction, and cytokinesis.

Intermediate Filaments
• Only in animal cells of certain tissues
• Most stable cytoskeletal elements
• Provide tensile strength for the cell

Motor Proteins
• Kinesin and Dynein move along microtubules
• Myosin move along microfilaments


Motor Proteins
• Kinesin and Dynein move along microtubules

• Myosin move along microfilaments

• http://www.sciencemag.org/feature/data/1049155.shl

Flagella and Cilia
• Structures for cell motility
• 9 + 2 internal structure


Pseudopods (False Feet)
• Temporary
• Irregular lobes
• Project from body
• Locomotion
• Catch prey
• Amoebas
• Macrophages





Cell Membrane Structure and Function
Plasma Membrane
• The plasma membrane isolates the cell while allowing communication with its surroundings

• Membranes are “fluid mosaics” in which proteins move within layers of lipids

• The phospholipid bilayer is the fluid portion of the membrane

Lipid Bilayer
• Main component of cell membranes
• Gives membrane its fluid properties
• Fatty acid tails sandwiched between hydrophilic heads

Phospholipids


Fluid Mosaic Model
• Membrane is a mosaic of
– Phospholipids
– Glycolipids
– Sterols
– Proteins
• Most phospholipids and some proteins can drift through membrane

Adhesion Proteins
• Help cells adhere (stick) to one another or to proteins

Communication Proteins
• Match up with identical proteins of an neighbor cell and form a channel

• Connects the cytoplasm of the two cells

• Chemical and electrical signals pass through these channels
Receptor Proteins
• Docking station for hormones or other signals

• The docking of hormones (or others) cause the cell to change its activities
Recognition Proteins
• Cell ID

• Identifies the cell as belonging to a body or tissue

• Or identifies the cell as foreign

• Movement across membranes occurs by both passive and active transport

• Molecules in fluids move in response to gradients


Passive Transporters

• Passive transport includes simple diffusion, facilitated diffusion, and osmosis
– Plasma membranes are selectively permeable to diffusion of molecules
– Some molecules move across membranes by simple diffusion

• Channels that allow specific solutes to move through without an energy cost

• Diffusion

• Concentration or electric gradients
Concentration Gradient
• Means the number of molecules or ions in one region is different than the number in another region

• In the absence of other forces, a substance moves from a region where it is more concentrated to one where it’s less concentrated - “down” gradient
Selective Permeability
Diffusion
• The net movement of like molecules or ions down a concentration gradient

• Although molecules collide randomly, the net movement is away from the place with the most collisions (down gradient)
Factors Affecting
Diffusion Rate
• Steepness of concentration gradient
– Steeper gradient, faster diffusion
• Molecular size
– Smaller molecules, faster diffusion
• Temperature
– Higher temperature, faster diffusion
• Electrical or pressure gradients











Osmosis
• Across a membrane
• Water molecules tend to diffuse down water concentration gradient
• Total number of molecules or ions dictates concentration of water
• Tonicity - relative solute concentrations
Tonicity


Fluid Pressure
• Hydrostatic pressure
– Fluids exert pressure to any contact surface
– When at rest (static) it acts with equal magnitude in all directions.
• Osmotic pressure
– Hydrostatic pressure produced by osmosis
• Turgor pressure
– Turgidity
– Positive internal pressure in a cell resulting from osmotic pressure

Active Transporters
• Pumps specific solutes across the membrane

• Works against a concentration gradient
• Uses energy
Transport Proteins
• Span the lipid bilayer
• Interior is able to open to both sides
• Change shape when they interact with solute
• Move water-soluble substances across a membrane




Membrane Cycling
Exocytosis and endocytosis continually replace and withdraw patches of plasma membrane
Passive and Active Transport
• Doesn’t require energy inputs
• Solutes diffuse through a channel inside the protein’s interior
• Net movement is down concentration gradient
Cell Junctions
• Communication centers
• Send and receive signals
• Send and receive materials
• Recognition of same cell type
• Join cell of same type