Cells
What is a cell?
• Structural and functional unit of all organisms.
• Some can work independently (on their own) to
carry out all of life’s processes.
• Some cells have organelles, some don’t.
Organelles are small, specialized cellular subunits
separated from the rest of the cell by
membranes.
• Organelles help a cell to move molecules, create
and store energy, and store information.
Important People and Cells
• Robert Hooke (1665) – coined the word “cell”
to describe what he saw when looking at
slices of cork under a microscope.
• Antony Van Leeuwenhoek (1600s) – invented
the microscope.
• Schwann (animal cells), Schleiden (plant
cells), and Virchow – Between the 3 of them
they came up with the Cell Theory.
The Cell Theory
• All living things are made of cells.
• Cells are the basic unit of all living things.
• All cells come from other living cells of the
same kind.
Basic Cell Structure (Three Basic Parts)
• Cell Membrane. A thin, flexible boundary
surrounding the cell.
• Cytoplasm. The watery, jelly-like part of the
cell that contains salts, minerals, and the cell
organelles.
• Genetic Material. The area of the cell where
the DNA (deoxyribonucleic acid) is stored. It
regulates all cell activities.
Diagram of a typical animal (eukaryotic) cell,
showing subcellular components.
Organelles:
(2) nucleus
(11) cytoplasm
Microscopes
Compound Light Microscope
Scanning Electron Microscope
• Invented in the
1590s.
• Allows limited view
of a cell.
• Invented in 1920s.
• Allows us to see
individual organelles.
• Transmission electron
microscope allows
scientists to see cells in
greater detail; it uses a
beam of electrons to take
3-D pictures of cells.
Prokaryotic vs. Eukaryotic Cells
Prokaryotic
• Does not have a true
nucleus.
• Genetic material is not
enclosed in a membrane.
• They have no membranebound organelles.
• Bacteria are prokaryotic
cells.
Eukaryotic
• Has nucleus surrounded by
membrane.
• DNA is located in nucleus.
• Has several membranebound organelles.
• Tend to be larger than
prokaryotes.
• Plants and animal cells are
both eukaryotic.
Parts of a Eukaryotic Cell
• Plastid – structures used in photosynthesis
and product storage. Only in plants.
• Cell Wall – Rigid membrane around plant cell;
provides shape and support. In plants only.
• Vacuoles – spherical storage sac for food and
water; larger in plants.
• Golgi Apparatus – flattened membrane sacs
for synthesis, packaging, and distribution.
Parts of Eukaryotic Cells (cont’d)
• Mitochondria – Rod-shaped double
membranous structures where cellular
respiration (energy release) takes place.
• Endoplasmic Reticulum – Folded membranes
having areas with and without ribosomes used
for transport of RNA and proteins.
• Nucleus – control center of the cell; location
of hereditary material (DNA); surrounded by
nuclear envelope/membrane.
Parts of Eukaryotic Cells (cont’d)
• Ribosomes – structures that manufacture
proteins; found on endoplasmic reticulum and
floating in cytoplasm.
• Lysosomes – sperical sac containing enzymes
for digestive functions; recycling center of cell.
• Cell membrane – Membrane surrounding the
cell that allows some molecules to pass
through; also called bilipid layer.
Parts of Eukaryotic Cells (cont’d)
• Cytoplasm – Jelly-like substance in the cell
around the nucleus and organelles; site of
many metabolic cycles and protein synthesis.
• Microfilaments/Microtubules – fibers and
tubes of protein that move internal cell parts.
• Nucleolus – inside nucleus; site of ribosome
production.
• Nuclear envelope/membrane – double
membrane that surrounds nucleus.
Parts of Eukaryotic Cells (cont’d)
• Centrioles – short tubes necessary for cell
reproduction in some cells. In animal cells
only.
• Cilia – Short, hair-like extensions on the
surface of some cells; used for movement and
food gathering. Animal cells only.
• Flagella – Long, whip-like extension on the
surface of some cells; used for movement.
Animal cells only.