Glenco chapter 7
A TOUR OF THE CELL
Cell: The basic unit of living matter separated from it’s environment by a
plasma membrane.
CELL THEORY
All living organisms are composed of cells
Cells are the basic unit of structure
Cells came from previously existing cells
THE STUFF INSIDE
Cytoplasm: Everything inside the cell between the plasma membrane and the
nucleus.
Organelle: (small organ) A cellular structure with a specialized function.
PROKARYOTIC CELLS
Prokaryotic cells: (pro: before + karyon: kernel) lacks true nucleus.
DNA is coiled into a nucleoid region.
Very small; averaging about 1/10 the size of eukaryotic cells.
Mainly bacteria
PROKARYOTES
DNA is in direct contact with cytoplasm.
Plasma membrane encloses cytoplasm.
Most bacteria have a chemically complex bacterial cell wall surrounding the
plasma membrane
EUKARYOTIC CELLS
Eukaryotic cells: (eu: true + karyon: kernel) Have a true membrane-bound
nucleus.
All eukaryotic cells are fundamentally similar.
Membranes portion the cytoplasm into compartments (membranous organelles)
Cell Membrane
Phospholipid bilayer
hydrophilic head (Polar)
hydrophobic tail (nonpolar)
Lipid Bilayer
Main component of cell membranes
Gives membrane its fluid properties
Fatty acid tails
sandwiched between hydrophilic heads
Fluid Mosaic Model
Membrane is a mosaic of
Phospholipids
Glycolipids
Sterols
Proteins
Most phospholipids and some proteins can drift through membrane
Membrane Proteins
Functions:
Enzyme activity
Cell-to-cell recognition
Cell-to-cell signaling
Transport of materials
Membranes & Movement
Equilibrium: Equal concentrations of solute on both sides of the membrane
Selectively permeable: Allows some substances to pass through the membranes
and stopping others
Transport Across Cell Membrane
Passive transport: The diffusion of a substance across the cell membrane. No
energy needed!
Diffusion: The tendency for particles to spread out from where they are more
concentrated to less concentrated. Driven by Entropy.
Concentration Gradient
The concentration gradient is when one side of the membrane has a greater
concentration and the substance diffuses across the membrane until it reaches
equilibrium.
Facilitated Diffusion
The diffusion of a substance across the cell membrane through a transport
protein.
Still passive transport because no energy is used.
Osmosis
The diffusion of water
Hypertonic: Solution with a higher solute concentration
Hypotonic: Solution with a lower solute concentration
Isotonic: Solutions with equal solute concentrations
Active Transport
The movement of molecules across the cell membrane using energy to pump the
substance through a transport protein.
ATP is usually the source of energy.
ATP
Adenosine triphosphate: Almost all energy for cellular work comes from ATP.
Transporting Large Molecules
Extocytosis: The export of large material out of the cell.
Endocytosis: The import of large molecules into a cell.
Nucleus
Stores genetic material
DNA
In the form of chromatin
Nucleolus
Where ribosomes are made
Ribosomes
Found on the rough ER and in the cytoplasm, Where proteins are produced,
Rough & Smooth ER
Rough ER: Has ribosomes on it, Where proteins are made
Smooth ER: No ribosomes
Where lipids are produced
Golgi Apparatus
Stores and/or modifies products of the endomembrane system, Named after
Camillo Golgi
Lysosomes
Greek meaning “breakdown body”, Breaks down waste products using hydrolytic
enzymes
Endomembrane System
The compartmentalization of the cells organelles using membranes
Transfer of material in membranous sacs called vesicles
Smooth & rough ER, Golgi apparatus, lysosomes, vacuoles
Chloroplasts
Chloroplasts are found in plants and some protists
Chloroplasts convert solar energy to chemical energy in sugars, Site of
photosynthesis
Mitochondria
Cells energy factory, ATP synthesis
Mitochondrial matrix
Inner compartment
Cristae
Folds in the inner membrane
Cytoskeleton
Network of fibers throughout the cytoplasm
Support
Motility
Regulation of biochemical activities
Microtubules, microfilaments, intermediated filaments
Movement
Flagella: Long, thin, whip-like structure with a core of microtubules used
for movement
Cilia: Shorter and more numerous bundles of microtubules used for movement