Unit 2:The Cell
Section 3: Organelle Structure and Function
Mrs. McNamara
Biology

Organelle-cell part that performs a
specific function for the cell
 Most are surrounded by a
membrane
 Each helps to maintain life of the
cell
Organelle:Cell::Organ:Human Body
Parts of the Cell
Cell Membrane Model
Phospholipids and proteins move
laterally ( side to side) for short
distances.
 Proteins make a pattern on the surface
known as the fluid mosaic model.

CELL MEMBRANE or PLASMA
MEMBRANE
Mainly made of phospholipids and
proteins.
 HYDROPHOBIC “tails” of phospholipids
make molecules line up as a LIPID
bilayer (double layer).
 POLAR head facing out and NONPOLAR tails facing in.

Membranes are selectively permeable they allow certain molecules to pass
through, but keep others out.
 In plants and bacteria, this is within
the cell wall.
 Cytoplasm is the “gel-like material and
organelles” between the nucleus and cell
membrane.

NUCLEUS AND NUCLEOLUS
NUCLEUS IS:
•Separated
from cytoplasm by nuclear membrane
(nuclear envelope).
•Nuclear pores allow molecules in and out.
•Serves as the COMMAND CENTER OF CELL; directs
cell’s activities.
•CONTAINS CELL’S GENETIC MATERIAL (DNA).
•Contains NUCLEOLUS (dark spot) which makes
RIBOSOMES which make proteins.


DNA is scrunched up as chromosomes in
DIVIDING CELLS.
DNA is spread out as chromatin in
NON-DIVIDING CELLS.
RIBOSOMES
Can be free in the cytosol or bound
to the surface of Rough ER.
 MADE OF proteins and RNA
FUNCTION: make protein for use in
the cell (free) or for export (bound).

ENDOPLASMIC RETICULUM (ER)
ROUGH ER/SMOOTH ER
 Rough ER has ribosomes on its surface, while smooth
does not; ER is continuous with nuclear envelope.


FUNCION ROUGH ER: Internal delivery system of
the cell; makes, processes, and transports proteins to
be exported outside the cell.
FUNCTION SMOOTH ER (no ribosomes): produce
lipids, involved in carbohydrate metabolism, and
detoxification of drugs and poisons.
GOLGI APPARATUS (BODY)
Looks like a stack of flattened sacs.
FUNCTION: Modify, sort, and package proteins and
lipids made by ER for transport out of cell. Enclose
digestive enzymes into membranes to form
lysosomes.

MITOCHONDRION (plural: MITOCHONDRIA)






Surround by double membrane.
Contains its own DNA.
Called the powerhouse of cell.
Site of cellular respiration (use glucose to produce
cell energy - ATP).
Permeable outer membrane.
Folded inner membrane = cristae (increases
surface area for more chemical reactions).
Lysosome

Sac containing digestive enzymes.
FUNCTION:
 Digests: food particles, disease-causing
bacteria and viruses, and worn out or broken
cell parts.

Plays a role in apotosis “programmed cell death”.


Cell suicide for the good of the organism.
Transports undigested material to cell
membrane for removal.
CYTOSKELETON



Cell’s skeleton.
Made of PROTEINS called microtubules and
microfilaments.
FUNCTION: Give the cell shape, strength and
the ability to move.


Microfilaments: contribute to cell movement and
muscle contraction.
Microtubules: assist in chromosome movement during
cell division (form spindle fibers).
CILIA and FLAGELLA
Made of PROTEINS called microtubules organized in a
nine/two arrangement that help with movement.
FUNCTION: external appendages from the cell membrane
that aid in locomotion (movement) of the cell, feeding, and
protection.

CENTRIOLES
Made of PROTEINS called
microtubules.
 Found only in animal cells.
 FUNCTION: aid in movement of
chromosomes during cell division.

VACUOLE



Animal:
 Sac for storage, digestion, and waste removal.
 Contains water solution.
Plant:
 Large, central vacuole; stores water and
nutrients needed by cell.
 Help support the shape of the cell.
Huge in plant cells, small in animal cells, NOT in
prokaryotic cells.
PLASTIDS




Surrounded by two membranes
Contains DNA, divides on its own.
CHROMOPLAST: make and store pigments
(flowers, fruits, etc). (red, yellow, orange)
LEUCOPLAST: store starch, lipids, proteins
AND…
CHLOROPLASTS




Where photosynthesis takes place (produces
plant food (sugars) and oxygen gas.
Contains green pigment, chlorophyll.
Flattened membrane sacs called thylakoids
contain CHLOROPHYLL ; stacks of thylakoids
called grana. Gel like material around thylakoids
called stroma.
FOUND ONLY IN plant CELLS.
CELL WALL



Found OUTSIDE the cell membrane in plant
cells and bacteria only.
Contains cellulose that provides support
(rigidity) and protection.
Bacteria have cell walls made of sugar and
proteins instead of cellulose.
PROKARYOTES


Bacteria are the most common
prokaryotic cell. They do not have a
nucleus, but do contain a single loop
made of DNA.
Like all cells, bacteria are
surrounded by a cell membrane
which contains the gel-like
cytoplasm of the cell.