Life Science
Chapter 7
Cell Structure, Function, Bacteria, Virus
Name ____________________________
1. Cell – The basic unit of structure and function in a living thing is called a cell. Every cell
can grow, respond, use energy, and reproduce. All cells have a cell membrane, organelles,
cytoplasm, and DNA. Even though all cells are similar they also all have their own unique
structure and function (136).
2. Robert Hooke – Robert Hooke was an English scientist who was the first person to see
and identify cells in 1663. He was looking at a piece of cork. Cork is actually the bark
from a tree and it consists of cells that are no longer alive. (137)
3. Anton Van Leeuwenhoek – Dutch glasses maker that built the first simple microscope with a
glass bead. (137)
4. Compound Light Microscope & Zacharias Janssen – A microscope that uses two
lenses, light, and an objective to magnify cells so that they can be seen is called a
compound light microscope. Zacharias Janssen is credited with making the first
compound light microscope in 1590.
5. Matthais Schleiden & Theodore Schwann – These were two German scientists that
concluded in 1869 that all plants and animals were made of cells. Schleiden worked with
plant cells and Schwann worked with animal cells. (137)
6. Rudolf Virchow – A German physician that concluded in 1855 that all cells come from
other cells. (138)
7. Cell Theory – The theory that explains the relationship between cells and living things is
called the cell theory. The cell theory states: (1) All living things are made from one or
more cells. (2) Cells come only from other cells that already exist. (3) All of an
organism’s life functions occur with-in cells. (4) Cells contain the hereditary material for
controlling the function of the cell, and transmitting information to the next generation of
cells. (138)
8. Cell Membrane – A separating barrier that controls movement of materials into and out
of the cell is called the cell membrane. It is made from lipids and proteins. It is the
“gatekeeper of the cell”. (139)
9. Organelle – A structure inside a cell that helps it perform its functions is called an
organelle. (139)
10. Cytoplasm – A fluid gel-like mixture that fills the cell and contains the organelles and
the compounds the cell needs is called the cytoplasm. (139)
11. DNA & Chromosomes – All cells have DNA. The DNA contains the instructions for
making new cells, as well as for controlling the cell. DNA is found inside the nucleus in
long strands of material called chromosomes (sometimes called chromatin). (139)
12. Prokaryotic Cell – A cell that does not have a nucleus or membrane covered organelles
is called prokaryotic. They are very small, very simple cells like bacteria. The name in
Greek means “before nucleus”. Because they have no nucleus the DNA is just bunched
up in the cytoplasm. They are believed to have originated 3.5 billion years ago. (140)
13. Eukaryotic Cell – A cell that does have a nucleus and membrane covered organelles is
called eukaryotic. They are usually ten times larger, more complex cells then
prokaryotic. The name in Greek means “true nucleus”. The DNA is contained in the
nucleus. They are believed to have originated 2 billion years ago. (140)
14. Nucleus & Nuclear Membrane– The largest and most visible organelle in the cell is the
nucleus. It controls the activities of the cell and contains the DNA. It is the “brain” of the
cell. It is surrounded by the nuclear membrane. The nuclear membrane controls the
movement of materials in and out of the nucleus. It is the “gatekeeper” of the nucleus.
15. Nucleolus – Found inside the nucleus is the nucleolus. It makes ribosomes and then
helps the ribosomes make protein. It also stores materials that are used by other
organelles. (144)
16. Endoplasmic Reticulum (ER) – A folded network of passageways (tunnels) that move
and transport materials like protein and fat (lipids) around inside the cell are called the
Endoplasmic Reticulum. They are the “highways” of the cell. Rough endoplasmic
reticulum has ribosomes along it. Smooth endoplasmic reticulum has no ribosomes along
it. (143)
17. Ribosomes – The protein factories that make protein for the cell are called ribosomes.
They look like tiny dense dots and are found along the endoplasmic reticulum, or simply
floating in the cytoplasm. (143)
18. Golgi Bodies – Golgi bodies receive and packages materials like protein from the ER and
sends them to various parts of the cell. They also release materials out of the cell. They are
the “shipping stations” for the cell. (146)
19. Mitochondria - The rod-shaped (sausage shaped) “powerhouses” of the cell are called
the mitochondria. They produce most of the cell’s energy using sugar and oxygen.
Muscle cells work hard and have many mitochondria. (145)
20. Lysosomes – Lysosomes contain chemical (enzymes) that break down and digest food
particles and worn out cell parts. Many of these things can then be reused by the cell.
They are the “custodial staff” of the cell. (146)
21. Cytoskeleton – The cytoskeleton gives the cell shape and provides strength and
structure. They are fibers made from proteins. They are the “walls and studs” of the cell.
22. Vacuoles – Vacuoles store water, food, and waste in the cell. (145)
23. Large Central Water Vacuole – A large central water vacuole is found only in plant cells.
It stores mainly water (cell sap) and helps create pressure that “inflates” the cell. This also
helps the plant stay upright. (145)
24. Chloroplasts – Chloroplasts are found only in plant cells. They capture the suns energy
and convert the light energy into chemical energy so that the plant can store it and make
sugar. Chloroplasts contain a green pigment called chlorophyll . Chlorophyll helps trap
the sun’s energy so that the plant cell can make sugar during photosynthesis. (148)
25. Cell Wall – Cell walls are also found only on plant cells. A cell wall surrounds the cell
membrane. It protects the cell and provides rigid structure. It is made up of a
carbohydrate called cellulose. (148)
26. Bacteria – The only single-celled prokaryotic cells that exist are called bacteria.
Bacteria are different from plant and animal cells for this reason (they are not
eukaryotic). Some bacteria are photosynthetic and produce their own food like a plant.
Most bacteria are decomposers and get their food by breaking down dead organisms. This
is good for the environment because it replaces nutrients. Some bacteria cause disease
(strep throat, cholera, typhoid, ear infections, etc.). We use antibiotics to kill bacterial
infections. (178)
27. Viruses & Host Cells – A tiny, nonliving particle of genetic material (DNA) surrounded
by a protein coat is called a virus. By itself a virus can do nothing. It cannot eat, produce
its own food, or reproduce. However they cause infection when they get inside a cell. The
infected cell is called a host cell. (184)
28. Stages of Infection – The stages of viral infection are as follows: 1) the virus is drawn
into the cell, or fuses to the cell membrane. 2) The viral DNA is released into the cell. 3)
The viral DNA commands the cell into making more virus parts. 4) The cell dies, bursts
open, and releases many new viruses. (185)
29. Immunity – Viruses must be identified and fought off by the body. A doctor cannot do
this. The body makes its own antibodies that destroy the viruses and the cells that are
infected with them. This is done by the immune system. Once you have fought off a virus
the antibodies stay in your system so that you cannot by sickened by that virus again.
This is called immunity. A vaccine is a dose of weakened viruses, or their empty protein
coats. When injected into the blood they “fool” the body into producing antibodies to kill
an infection even though you are not sick. This also creates immunity to that disease (flu,
mumps, measles, etc.). (186)