Cells
The Basic Unit of Life
Organelles
• Special structures that perform specific
functions in cells
• Cell Animations
Nucleus
• Has a double-layered porous (with pores - very
tiny holes) membrane
• Contains DNA (deoxyribonucleic acid), DNA
forms chromatin (long strands) and has
instructions to assemble the necessary substances
for building the cell and making it work
• Has a nucleolus, a dark structure that
manufactures ribosomes
Cytoplasm
• The area outside the nucleus and inside the
cell membrane. The cell membrane
separates the cell contents from its
surroundings.
• Jelly-like material
• Supports nucleus and other organelles
Ribosomes
• Structures that make protein
• Protein is used to make enzymes, muscle
tissue, and other important structures
Endoplasmic Reticulum
• Series of canals
• Canals are used to transport materials to
different parts of the cells
• Rough Endoplasmic reticulum has
ribosomes attached
Mitochondria
• Transform energy for the cell
Golgi Bodies
• Package useful materials and secrete them
to the outside of the cell for use elsewhere
Vacuoles
• Fluid-filled storehouses that contain water,
food, wastes and other materials
Lysosomes
• Break down food and digest wastes and
worn out cell parts
The Cell Cycle
• Cell division allows organisms to grow and
develop
• When cells divide, they must have a
complete nucleus, so all the instructions in
the DNA are reproduced
• The process that makes this happen is
MITOSIS
Before Mitosis
• Cells copy the chromatin so there are two
sets of DNA
• The chromatin coils up to form doublestranded chromosomes, joined by a
centromere
• Copy Figure 1.9 on page 17
Phases of Mitosis
•
•
•
•
Remember PMAT
Four major phases
Results in two complete sets of DNA
Prophase, Metaphase, Anaphase, Telophase
Prophase
• Chromosomes visible with a microscope
• Nuclear membrane disappears
• Spindle fibres form and stretch across the
cell
• Spindle fibres attach to centromeres
Metaphase
• Spindle fibres pull chromosomes into a line
across the middle of the cell
Anaphase
• Spindle fibres shorten
• Centromeres are pulled apart
• Chromosomes move to the opposite (ends)
poles of the cell
Telophase
• Final phase of mitosis
• Spindle fibres disappear
• Nuclear membrane forms around each set of
chromosomes
• Nucleolus appears
• Single stranded chromosomes uncoil into
strands of chromatin
• The cell is ready to divide-cytokinesis
Cell Division
• After telophase
• Animal cells - the membrane pinches together and
the cell divides
• Plant cells - a cell plate develops across the centre
of the cell forming a new cell wall
• Two new cells- daughter cells
• Number of chromosmes in the nucleus of each
cell is identical to the number in the original cell
Interphase
•
•
•
•
•
•
•
•
Inter- between
Cell growth, replication of DNA
Prepares for mitosis
Refer to the cell cycle pie graph on page 23
Mitosis is ____ h
Rapid growth is ____ h
Growth and DNA replication is ____h
Growth and preparation for division is ____ h