CELLS
Mrs. Mandi O’Mara, M. Ed Science
History:
Hooke (1665) – observed cork –
named the cell
What Hooke saw:
Leeuwenhoek (1674) – observed
living cells in pond water
:
Schleiden (1838) – plants are
made of cells
Schwann (1839) – animals are
made of cells
Virchow (1855) – cells come only
from other cells
The Cell Theory
• 1) All living things are composed of
one or more cells
• 2) Cells are the basic units of
structure and function in living
things
• 3) New cells are produced only
from existing cells
Basic Cell Structures:
Cell/Plasma Membrane
Cytoplasm
DNA
Ribosomes
Basic Cell Structures
• 1) Cell Membrane – thin, flexible
barrier around the cell
• 2) Cell Wall – strong layer around cell
membrane
• 3) Nucleus – contains cell’s genetic
material and controls the cell’s
activities
• 4) Cytoplasm – the fluid material
inside of the cell membrane (does not
include the nucleus)
PROKARYOTES
• No nucleus or membrane bound
organelles
• · small and simple
•
•
•
•
·
·
·
·
unicellular
single, circular molecule of DNA
oldest known cells
Ex: bacteria
prokaryote
EUKARYOTES
• Have a nucleus and membrane
bound organelles
• contains organelles (structures
specialized to perform specific
functions within the cell)
• unicellular/multicellular
eukaryotes
Cell Structures
• Cell Wall – provides support and
protection for the cell; allow water,
oxygen, carbon dioxide and other
substances to pass through
• found in plants, algae, fungi, most
prokaryotes
• animal cells DO NOT have a cell wall
• mostly made of cellulose and protein
• *Cellulose is the main component of
wood and paper*
• lies outside cell membrane
• Nucleus – controls cell processes and
contains genetic information
• Chromatin – protein with DNA bound
to it
• Chromosomes – chromatin condensed;
distinct, threadlike structure
containing genetic information
• Nucleolus – small, dense region within
nucleus; ribosomes made here
• Nuclear Envelope – double membrane
layer that surrounds nucleus; contains
thousands of “nuclear pores” for
material to move in and out of the
nucleus
• Cytoskeleton – a network of protein
filaments that help cell to maintain
its shape; also involved in cell
movement
• Cytoskeleton is made up of:
• Microtubules – hollow tubes of
protein; they maintain cell shape
and serve as “tracks” for
organelles to move
• Microfilaments – long, thin
fibers that function in movement
and support of cell
Organelles (little organs)
• Ribosomes – site of protein synthesis;
found free or attached to ER
• Endoplasmic Reticulum – transport
system
• Rough ER – ribosomes are attached;
parts of cell membrane are made here;
proteins are modified
• Smooth ER – does not have ribosomes
attached; contains enzymes to perform
specialized tasks; makes lipids
• Golgi Apparatus (Golgi Body) –
packaging and distribution of proteins
• Lysosomes – contains digestive
enzymes to break down food and old
organelles
• Vacuoles – stores water, food and
waste
• Plants have single large central
vacuole
• Smaller vacuoles involved in
transport are called vesicles
• Chloroplasts – site of
photosynthesis
• contains green pigment,
chlorophyll
• has double membrane
• not found in animal cells
• Mitochondria – produces
energy through respiration
• “powerhouse” of the cell
• has double membrane