CELL STRUCTURE & FUNCTION
CELL THEORY The cell theory is a fundamental
concept in biology. It states:
All living things are composed of cells. The cell is the basic structural unit of all
living things. All cells arise from pre-existing cells.
TWO TYPES OF CELLS PROKARYOTIC
Lack a “true” nucleus Do not have organelles Bacteria is the most common example
EUKARYOTIC Have a nucleus Contain organelles separated by
membranes Much larger than prokaryotic cells
TWO TYPES OF EUKARYOTIC CELLS
Animal Cells
Plant Cells
COMMON ORGANELLES
1. CELL MEMBRANE The “skin” of the cell; it holds everything inside. It is SEMIPERMEABLE which means it allows
certain things to go through it.2. NUCLEUS
The “control centre” or “brain” of the cell. Usually the largest organelle. Where DNA is stored. DNA contains the
chromosomes which is where all genetic information is found.
3. CYTOPLASM A “jelly-like” substance composed of
mostly water that surrounds and protects the organelles.
4. VACUOLES “Sac-like” containers made from pieces of
cells membrane.
5. RIBOSOMES The “builders” of protein. They are dark looking dense granules that
can be free floating in the cytoplasm or attached to the endoplasmic reticulum.
Composed of RNA and PROTEIN.6. ENDOPLASMIC RETICULUM
A series of “canals” or small tubules that branch out from the nucleus.
ROUGH ER has ribosomes attached. SMOOTH ER has no ribosomes.
7. GOLGI APPARATUS Looks like a flattened stack of pancakes. Where protein is stored until needed. If the protein is needed outside of the cell,
the GA packages it into a vacuole and sends it to the cells membrane for transport.
8. MITOCHONDRIA The “powerhouse” of the cell. The site of CELLULAR RESPIRATION in cells
which use glucose and oxygen to make carbon dioxide, water and ATP (energy).
9. LYSOSOMES Membrane bound sacs that aid in
digestion. Certain types of human white blood cells
use lysosomes to destroy invading bacteria. For this reason they have the nickname “SUICIDE CELLS”.
They also function in breaking down damaged organelles in a cell.
DIFFERENCES
Despite the fact that plant and animal cells contain the above 9 organelles in common they have some significant difference as well.
PLANT CELLS ANIMAL CELLS
Angular in shape Irregular in shape
Tightly packed Loosely gathered
Large vaculoles Small vaculoles
Contain cell wall No cell wall
Contain chloroplasts No chloroplasts
No centrioles Contain centrioles
CELL WALL Made from a rigid material called CELLULOSE. They provide plants with structural support and
allow them to grow tall without falling over. CHLOROPLASTS
These organelles capture energy from the sun and convert it into chemical energy in a process called PHOTOSYNTHESIS.
They are composed of a double membrane and an internal membrane system that contains CHLOROPHYLL which is a light capturing molecule.
CENTRIOLES Centrioles organize the spindle apparatus
on which the chromosomes move during mitosis.
They are critical to cell division.