Transcript 7.3 Structures and Organelles

Objectives:
• 4(A) Compare and contrast prokaryotic and eukaryotic cells.
• 4(B) Investigate and explain cellular processes, including homeostasis,
energy conversions, transport of molecules, and synthesis of new
molecules.

The environment enclosed by the plasma
membrane is a semifluid material called
cytoplasm.
 In prokaryotes, all the chemical processes of the
cell take place directly in the cytoplasm.
 In eukaryotes, these cell processes take place
within organelles in the cytoplasm.

The cytoskeleton is a supporting network of
long, thin protein fibers that form a
framework for the cell and provide an anchor
for organelles.
 Microtubules are long, hollow protein cylinders
that form a rigid skeleton for the cell and assist in
moving substances within the cell.
 Microfilaments are thin protein threads that help
give the cell shape and enable part or the entire
cell to move.

The nucleus
 Contains most of the cell’s DNA, which stores
information used to make proteins that determine
a cell’s growth, function, and reproduction.
 Surrounded by a double membrane called a
nuclear envelope.

Ribosomes
 Organelles that manufacture proteins.
▪ Not membrane-bound like other organelles.
▪ Produced inside the nucleus in the nucleolus.

Endoplasmic reticulum (ER)
 A membrane system of folded sacs and
interconnected channels that serves as the site for
protein and lipid synthesis.
 Two types: rough ER and smooth ER

Golgi apparatus
 A flattened stack of membranes that modifies,
sorts, and packages proteins.
 Proteins are packaged into sacs called vesicles,
which can fuse to the plasma membrane and
release the proteins to the environment.

Lysosome
 Are vesicles that contain substances that digest
excess or worn-out organelles and food particles.
 Also digest bacteria and viruses that invade the
cell.

Centrioles
 Organelles made of microtubules that function
during cell division.
 Located in the cytoplasm.

Mitochondria
 Convert food particles into usable energy.
 Have an outer membrane and a highly folded
inner membrane that provides surface area for
breaking the bonds in sugar molecules.

Vacuoles
 A membrane bound sac used for temporary
storage
 Store food, enzymes, or waste.
 Found only in plant cells.

Chloroplasts
 Found in plant cells and some other eukaryotes.
 Capture light and convert it into chemical energy
during photosynthesis.
 Contain multiple small disks called thylakoids,
which contain the light capturing pigment
chlorophyll.

Cell Wall
 Found in plant cells.
 A thick rigid, mesh of fibers that surround the
outside of the plasma membrane.
▪ Protects the cell ad gives it structure.
▪ Made from a carbohydrate called cellulose.

Cilia and Flagella
 Cilia are short, numerous projections that look like
hair.
▪ Move in tandem like oars in a rowboat.
 Flagella are longer and less numerous than cilia.
▪ Move with a whip-like motion.
 Both are made of microtubules.

Features plant cells have that animal cells
generally do not:
 Chloroplasts/chlorophyll
 Vacuoles
 Cell walls


An understanding of different organelles allows
for an understanding of cellular processes.
Example: Protein synthesis:
 Begins in the nucleus with information contained in
DNA.
 RNA and ribosomes leave the nucleus and produce a
protein on the ER.
 Proteins produced in the ER are sent to the Golding
apparatus for packaging.
 Packaged proteins are delivered to other organelles
where they serve a variety of functions.