Chapter 4- Cells Organisms are composed of one to many microscopic cells Unicellular Multicellular Multicellular organisms are composed of one or more types of tissues Different types of tissues are grouped to form organs The Two Major Types of Cells The Three Domains of Life Domain Bacteria Domain Archaea •Prokaryotic cells
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Chapter 4- Cells
Organisms are composed of one to many microscopic cells
Unicellular
Multicellular
Multicellular organisms are composed of one or more types of tissues
Different types of tissues are grouped to form organs
The Two Major Types of Cells
The Three Domains of Life
Domain Bacteria Domain Archaea
•Prokaryotic cells
Domain Eukarya includes all of the eukaryotic organisms.
Domain Eukarya
Protists (multiple kingdoms) Kingdom Plantae
Kingdom Fungi Kingdom Animalia
•Eukaryotic cells
Diagram of a plant cell
All eukaryotic cells and prokaryotic cells have at least three components in common:
The plasma membrane
Prokaryotic flagella
Nucleoid region (DNA)
Ribosomes Plasma membrane
Cell wall
Capsule
Pili
The plasma membrane is composed of phospholipids, proteins, and
other materials.
The cytoplasm consists of the entire region of the cell between the nucleus and plasma membrane
Ribosomes, are composed of protein and RNA.
Cell Membrane Structure and Function
The membranes of cells are composed of:
•The lipids belong to a special category called phospholipids
The cell membrane is described as selectively permeable
because it allows free passage of some materials and not
others.
Hydrophilic head
Hydrophobic tail
Outside cell
Cytoplasm (inside cell)
(a) Phospholipid bilayer of membrane
Hydrophilic region of protein
Phospholipid bilayer
Hydrophobic region of protein
(b) Fluid mosaic model of membrane
The cytosol is the cellular fluid.
-Larger molecules and ions (molecules with an
electrical charge) do not pass through the cell
membrane without specific membrane transport
proteins.
-Very small, uncharged molecules can easily pass through the membrane
Selective membrane permeability is the basis for osmosis.
Osmosis and Water Balance in Cells
Osmosis is the diffusion of water across the cell
membrane in response to differences in concentrations of
solutes (dissolved substances) such as sugars or ions.
Diffusion
Water, like many substances, will move from where it is
more concentrated to where it is less concentrated.
If the concentration of solutes inside and outside the cell is the same, then the cell is
osmotically balanced.
If the solute concentration is lower outside a cell than inside,
Osmosis and Water Balance in Cells
Prokaryotes, protists, fungi, and plants have cell walls that limit
the increase of cell volume through the uptake of water.
If the concentration of solutes outside the cells is higher than inside, water leaves the cell and the cytoplasm shrinks.
Eukaryotic cells share some features that prokaryotes lack
All eukaryotic cells have a:
The nucleus is the major site of genetic information (DNA) storage in eukaryotic cells.
The nuclear envelope
Nuclei also contain nucleoli (nucleolus, sing.),
Ribosomes Chromatin Nuclear envelope
Nucleolus Pore
Eukaryotic nuclear DNA is combined with proteins to
form chromosomes.
•Many of the membranous organelles in the cell belong to the endomembrane system
The endoplasmic reticulum (ER)
Nuclear envelope
Ribosomes
Rough ER Smooth ER
Rough ER
•The “roughness” of the rough ER is due to ribosomes that
stud the outside of the ER membrane
Ribosomes
Small globular structures composed of protein and RNA
that generate proteins from amino acids.
Transport vesicle buds off
Ribosome Secretory protein inside transport vesicle
Protein
Rough ER
Polypeptide
1 2
3
4
After the rough ER synthesizes a molecule it packages
the molecule into transport vesicles
Smooth ER
lacks the surface ribosomes of rough ER Nuclear envelope
Ribosomes
Rough ER Smooth ER
The Golgi apparatus
Works in partnership with ER
The Golgi apparatus of a cell consists of 1 or more Golgi bodies.
The cytoskeleton consists of three major types of long, thin, protein fibers:
Flagella and Cilia
Eukaryotic flagella typically contain a pair of single microtubules, surrounded by a
cylinder of nine paired microtubules (9 + 2 arrangement).
Mitochondria
Peroxisomes
-surrounded by single membrane
Components of cell walls: Cellulose
Non-cellulose components of plant cell walls
Plant cell walls also contain other polysaccharides such as:
Plant cells are distinguished from most other eukaryotic cells by:
Plant cells
Hemicellulose is a polymer of glucose and other sugars.
Each mitochondrion is enclosed by an envelope
composed of an outer membrane and a highly folded
inner membrane.
Cellulose is a polymer of glucose units, but the glucose monomers are linked together in different orientation.