Download CELLS

CELLS
Structure
Cell Membrane



Surrounds the cell to separate it from its external
environment; it gives support and protection to the cell
Composed of a double layer of phospholipids called the
lipid bilayer; it also has proteins embedded in it
The membrane acts as a selective barrier by controlling
what substances enter and leave the cell
Cell Walls
Found outside the cell membrane
 Function to give support and protection to
the cell
 Found in plants, algae, fungi, and several
prokaryotes

Cell Interior
 The
cell has two major divisions:
Cytoplasm
Nucleus
Cytoplasm



A semi-fluid substance in which all
of the cell’s organelles are
suspended
Located between the nucleus and
the cell membrane
Contains the cytoskeleton, a
network of microtubules that support
the cell and give it shape
Nucleus

The control center of the cell and where
the cell’s DNA is located; is divided into 3
parts:
 Nuclear
Membrane: Separates the nucleus
from the cytoplasm and contains pores so
that substances may enter or leave the
nucleus
 Nucleolus: structure within the nucleus that
is responsible for making rRNA
 Nucleoplasm: similar to the cytoplasm, it is a
semifluid substance in which the DNA and
nucleolus are suspended
Organelles

Endoplasmic reticulum (ER):
 Extensive
 There are
network of membranes
2 types:
 Rough ER: contains ribosomes that
make proteins destined to leave the
cell
 Smooth ER: makes lipids, steroids,
and is involved in detoxification;
important in cells that are
responsible for ridding the body of
toxic substances (i.e. liver)
Organelles (cont.)

Ribosomes:
 Structures
involved in protein
synthesis
 Found attached to the RER or
suspended in the cytoplasm


Mitochondria: take the energy
stored in food and transforms it into
chemicals the cell can use
Golgi apparatus:
 Series
of flat membrane-bound sacs
 Packages proteins made from the
RER and sends them in membranebound vesicles to their destination
Organelles (cont.)

Lysosome:
 Membrane-bound
organelles filled with
enzymes
 These enzymes are used to break down
lipids, carbohydrates, and proteins for
use by the cell
 They also break down old organelles
that no longer function
Organelles (cont.)

Vacuole:
 Membrane-bound
compartment that serves many
functions (i.e. absorbs water, stores proteins, stores
wastes, etc.)
 Plant cells have one large central vacuole
 Animal cells contain several small vacuoles
Organelles (cont.)

Chloroplasts: plant cells have these
organelles that absorb the energy from
sunlight and transform it into chemical
energy through the process of
photosynthesis