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.