CELL STRUCTURE
&
FUNCTION
CHAPTER 4
CELLS
• ALL LIVING THINGS ARE MADE UP OF ONE
OR MORE CELLS
• A CELL IS THE SMALLEST UNIT THAT CAN
CARRY ON ALL OF THE PROCESSES OF LIFE.
DISCOVERY OF CELLS
*Robert Hooke (mid-1600s)
– Observed sliver of cork from the bark of a cork oak tree.
– Saw “row of empty boxes”
– Coined the term cell (reminded him of the cubicles or
“cells” where monks live.)
• Anton van Leewenhoek (1673)
– First person to observe living cells.
– Able to observe cells with green stripes from an alga of
the genus spirogyra and bell shaped cells on stalks of a
protist of the genus vorticella
CELL THEORY
• (1839)Theodor Schwann & Matthias
Schleiden
“ all plants are made up of
cells”
“ all animals are made up of
cells”
• (50 yrs. later) Rudolf Virchow
“all cells come from cells”
• These three observations
Were combined to form a basic
Theory about the cellular nature of
Life.
CELL THEORY:
• All living things are made of
cells
• Smallest living unit of
structure and function of all
organisms is the cell
• All cells arise from
preexisting cells
CELL DIVERSITY
Cell Shape:
• The diversity in cell shapes reflects
the different functions of cells.
• Each cell has a shape designed to
allow the cell to perform its function
effectively.
Cell Size:
• The size of a cell is limited by the relationship of the
cell’s outer surface area to its volume..
Characteristics of All Cells
• ALL CELLS HAVE THREE BASIC FEATURES IN
COMMON:
Plasma membrane (cell membrane) – cell’s
outer boundary, acts as a barrier between the
inside and the outside of a cell
Cytoplasm- region of the cell within plasma
membrane that includes fluid, cytoskeleton,
and all organelles except nucleus.
Control center (nucleus)- contains DNA
TWO BASIC TYPES OF CELLS
Prokaryotic Eukaryotic
• First cell type on earth
• Cell type of Bacteria and
Archaea
• No membrane bound
nucleus
• Nucleoid = region of DNA
concentration
• Organelles not bound by
membranes
• Nucleus bound by
membrane
• Include fungi, protists,
plant, and animal cells
• Possess many organelles
that perform specific
functions in the cell
• Usually much larger than
prokaryotic cells
http://www.youtube.com/watch?v=
yWy4o_UfZ4A&feature=related
ORGANELLES
&
THEIR FUNCTION
Plasma Membrane
• Functions: 1) allows only certain molecules in or
out of a cell 2) separates internal metabolic
reactions from external environment 3) allows
cell to excrete wastes and interact with its
environment.
• Made primarily of phospholipids
: Phospholipid B-Layer
• Membrane Proteins: Plasma membranes contain
specific proteins embedded within the lipid bilayer called integral proteins.
• Integral proteins play important roles in actively
transporting molecules into the cell.
Nucleus
• Most of the functions of a eukaryotic cell are controlled
by the nucleus, and houses/protects the cells genetic
information.
• Nucleoplasm- jellylike liquid which holds the contents of
the nucleus.
• Nuclear envelope – double membrane that surrounds
nucleus. Made up of two phospholipid b-layers.
• Nucleolus – Dense area where DNA is concentrated.
Mitochondria
• Tiny organelles that transfer energy from organic
molecules to adenosine triphosphate (ATP),
which powers the cell.
• Mitochondrial DNA –mitochondria
have their own DNA and can
reproduce only by the division of
preexisting mitochondria.
Ribosomes
• Small roughly spherical organelles that are
responsible for building protein. Ribosomes do
not have a membrane, they are made of protein
and RNA molecules.
Endoplasmic Reticulum
• System of membranous tubes and sacs, called
cisternae.
• Functions: intracellular highway, a path along which
molecules move from one part of the cell to another.
• Two types of ER:
- Rough endoplasmic reticulum – system of
interconnected flattened sacs covered with
ribosomes, which produces proteins.
- Smooth endoplasmic reticulum- lacks ribosomes
which has a smooth appearance and builds lipids.
Golgi Apparatus
• system of flattened sacs that receive vesicles
from the ER containing newly made proteins or
lipids. The Golgi apparatus labels and packs
cellular products and prepares them for export.
• The “mail man” of the cell
Vesicles
• Lysosomes- vesicles that bud from the Golgi
apparatus and contain digestive enzymes that
break down large molecules. Lysosomes also
digest worn-out organelles (autophagy), and
break down cells (autolysis).
• Peroxisomes- abundant in liver and kidney cells
where they detoxify alcohol and other drugs.
Cytoskeleton
• Network of thin tubes and filaments that
crisscross the cytosol, which give shape to the
cell.
CILIA & FLAGELLA
• CILIA & FLAGELLA: hair
like structures that extend
from the surface of the
cell, where they assist in
movement.
• Cilia are short and a re
present in large numbers
on certain cells whereas
flagella are longer and far
less numerous.
PLANT CELLS
• Cell wall – rigid layer that lies outside the cell’s
plasma membrane, which contain a carbohydrate
called cellulose.
• Central vacuole – A large, fluid-filled organelle
that stores water, enzymes, metabolic wastes, and
other materials.
• Chloroplasts – use light energy to make
carbohydrates from carbon dioxide and water.
Contains chlorophyll ( molecules that absorbs
light and captures light energy for the cell)