A Spotlight on Research

CELLULAR ORGANELLES

What are organelles?

Organelles are membrane-bound structures inside cells that carry out specific functions.

Today we will learn the functions of the organelles by studying real scientific research.

Scientific Research

Scientists perform experiments to test hypotheses. Scientific theories explain phenomena or events in nature. Theories are

based on evidence.

The NUCLEUS:The nucleus was the first

organelle discovered. It was observed by Anton van Leeuwenhoek in 1719.

The nucleus is the control center of the cell, where genetic information is stored as DNA.

RIBOSOMES:

Ribosomes are organelles made from RNA and proteins.

They are made in a part of the nucleus called the nucleolus.

Ribosomes are important for making proteins from instructions stored in DNA.

RIBOSOMES:While they are represented as dots on

many cell diagrams, ribosomes actually have a very complex structure.

3 scientists won the 2009 Nobel Prize in Chemistry for discovering the structure of ribosomes. Scientists had been trying to do this since the 1960’s.

RIBOSOMES:Ribosomes are located in 2 places inside

the cell:

Membrane-bound ribosomes are found in the endoplasmic reticulum.

Free ribosomes are found in the cytoplasm.

The ENDOPLASMIC RETICULUM (ER)Scientists believe that the ER developed

from infoldings of the plasma membrane.There are two types of ER:

1) Rough ER contains ribosomes and makes proteins.

2) Smooth ER has no ribosomes and makes lipids.

The GOLGI BODY:

The Golgi body is responsible for processing and packaging proteins.

Proteins from the Golgi go on to either the cell membrane or other organelles.

The GOLGI BODY:Scientists use a protein called Green

fluorescent protein (GFP) to “track” the movement of proteins through the cell.

The CELL MEMBRANE:The cell membrane is composed of a lipid

bilayer with some proteins on its surface

The CELL MEMBRANE:Gorter & Grendel performed an

experiment that proved the existence of a bilayer.

They found the area of red blood cell membranes was two times the area of the cells themselves.

The CELL MEMBRANE:Functions of the cell membrane:

1) Separates the cell from its surroundings

2) Selectively permeable – lets some things in and keeps other things out

3) Structure

The MITOCHONDRION:Mitochondria are the energy producing

organelles in all eukaryotic cells.The energy in mitochondria is in the form

of adenosine triphosphate (ATP).

The MITOCHONDRION:

Research provides evidence for the endosymbiotic theory, the idea that mitochondria and some other organelles originated as prokaryotes that were engulfed b a eukaryotic cell.

Click this link:Video on evidence for the endosymbiotic the

ory

The CHLOROPLAST:Found only in plant cells.The chlorophyll in chloroplasts provide

plants’ green color.Chloroplasts absorb energy from the sun

to make glucose (sugars).This process is called photosynthesis.

The VACUOLE:While they exist in both plant and animal

cells, plants have a large, central vacuole.

Plant vacuoles can occupy as much as ninety percent of the cell.

The VACUOLE:

Three functions: 1) Water storage 2) Contains chemicals that protect

the plant 3) Water pressure in the vacuole

supports the cell wall

The CELL WALL:Cell walls, found in

plant cells, are located outside the plasma membrane.

The cell wall was the first structure to be viewed with a microscope.Robert Hooke’s

observation of cork in 1665.

The CELL WALL:Freeze-fracture techniques and electron

microscopy were used to determine how the cell wall is produced.

Other Important Organelles:Lysosomes – Digest waste and cellular

debrisCytoskeleton – Provide structure and

serve as a transport network for proteins in the cellMolecular motors

Centriole – Specialized organelle used in cell division

Cilia & Flagella – Specialized parts of the cytoskeleton that allow cells to move.