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Chapter 7
Cell Structure and
Function
All living things are made
up of small individual units
called cells.
Historical Background
Robert Hooke (1600’s)- examined
slices of cork with a magnifying
glass and observed box-like
structures which he called cells
(See Figure 7-1 in text).
Historical Background
Improvement in microscopes in the
last four centuries has allowed
scientists to better develop the cell
theory.
On the left is a
picture of an
electron
microscope. It
can magnify up
to one million
times.
Cell Theory
1. Cells are the structural
units of living things.
2. Cells are the functional
units of living things.
3. All cells arise from
preexisting cells.
Exceptions to the Cell
Theory:
1. Viruses
a) are living
b) are not made up of
cells
c) contain genetic
material
2. Where did the first cell come
from?
Cell Categories
Prokaryotes: Prokaryotic cells have
genetic material (e.g. DNA) that is not
contained in the nucleus.
On the right is a
bacteria. It is an
example of a
prokaryotic cell.
What makes a
bacteria a prokaryote?
It does not have
a nucleus.
Cell Categories (Part 2)
Eukaryotes: Eukaryotic cells contain a
nucleus in which their genetic material
is separated from the rest of the cell.
On the left is an
example of an animal
cell. It is a eukaryotic
cell. What makes the
cell eukaryotic?
It has a nucleus.
Cell structure
1. Cell membrane- also
known as the plasma
membrane, it surrounds
the cell and controls what
goes into and out of the
cell.
It is a double-layered,
semi permeable membrane
composed of lipids and
proteins.
a) Phagocytosis
The “engulfing” of material by
the cell
Phagocytosis website
b) Pinocytosis
The “cell drinking” of material
by the cell
2. Cell Wall
Found only in plants
It is a nonliving supportive
structure found outside the
cell membrane
Composed of cellulose
Primary function is to
support and protect the cell
3. Cytoplasm
Fluid-like material that fills the
space between the cell
membrane and the nucleus of
the cell
Contains the organelles
Many biochemical processes
occur in the cytoplasm
4. Nucleus
Control center of the cell
Contains DNA and
hereditary material
Surrounded by a nuclear
membrane.
5. Nucleolus
Structure that is the site
of ribosome synthesis
6. Ribosomes
Site of protein synthesis
May be found in the
cytoplasm or attached to
the membrane of the
endoplasmic reticulum
7. Endoplasmic
reticulum
System of fluid-filled canals
Associated with synthesis,
storage, and transport of
materials within the cell
8. Lysosomes
Membrane-bounded sacs that
contain digestive enzymes
Involved in the digestion of
food in unicellular organisms
Destroy damaged or old cell
parts in multicellular
organisms
9. Vacuoles
Fluid-filled sacs found in the
cytoplasm
Contain stored materials,
such as food and wastes
Contractile vacuole- used to
pump excess water out of
cell
10. Mitochondria
Powerhouse of the cell
The site of respiration
producing energy for the
cell
11. Centrioles
Found only in animal
cells, not plant cells
Located near the nucleus
Play a role in cell division
12. Chloroplast
Found only in plant cells
Contain chlorophyll
pigment
Site of photosynthesis
13. Cilia and Flagella
Organelles responsible
for cell movement
Animal Cell
Plant Cell
Passive Transport
vs.
Active
Transport
Diffusion
The movement of
particles from an area of
high concentration to an
area of low concentration
Active Transport
A type of transport
requiring energy to move
materials across the cell
membrane
(low concentration to high
concentration)
Concentration
Gradient
The difference in concentration
between a region of high
concentration and a region of
low concentration
Cell membrane
Made up of proteins and lipids
Also known as :
- plasma membrane
- selective membrane
- semipermeable
membrane
Water molecules are small
enough to easily diffuse across
the cell membrane
Osmosis
The diffusion of water across a
semipermeable membrane
from a region of high
concentration to a region of
low concentration
Example of Passive transport
Process of Osmosis
Osmotic Pressure
The pressure that results from the build
up of water in the plant cell and pushes
the cell membrane of the plant cell
against the cell wall.