Cytoplasmic Organelles

• Plastids• Plant organelle that may take many forms. • Examples include chloroplast, leukoplasts

(which store food), & chromoplasts (which store pigment molecules).

Cytoplasmic Organelles

• Cytoskeleton • (It has replaced the idea of “protoplasm”) • 2 main components:

• (1) Microtubules—support cell shape and help organelles move through the cell.

• (2) Microfiliments—function in movement of both the cytoplasm and the cell.

Cytoplasmic Organelles: Centrioles

Tools of a BiologistMICROSCOPY

Two factors play an important role in microscopy:

1. Magnification compares real size of a specimen with the one viewed with microscope.

2. Resolution (resolving power) refers to the clarity of the specimen viewed under the

microscope.

Tools of a BiologistCOMPOUND LIGHT MICROSCOPE

•The most commonly used microscope.

• Cells and small organisms can be observed while they are still alive.

•Light microscopes are limited to about

1000 times magnification due to the limit of resolution.

Tools of a Biologist

COMPOUND LIGHT MICROSCOPE

•Limit of resolution is the point of magnification beyond which images

become blurry and lose detail.

•This occurs because light passing through a lens is scattered, making it hard to form a clear image.

Tools of a BiologistCOMPOUND LIGHT MICROSCOPE

•Limit of resolution is the point of magnification beyond which images become blurry and lose detail.

•This occurs because light passing through a lens is scattered, making it hard to form a clear image.

•For standard light microscopes, the limit of resolution is about 0.2 micrometers.

Tools of a BiologistELECTRON MICROSCOPES

•These microscopes use a beam of electrons and magnets instead of light and lenses.

• They have a shorter wave length (0.2 nanometers) than a light microscope.

•Because of the high-energy particles involved, these microscopes cannot view

living specimens.

Tools of a BiologistTransmission Electron Microscope (TEM)

TEM transmits a beam of electrons through a very thinly sliced specimen.

TEM can magnify objects up to 1,000,000 times.

The electron beam can also be used to expose photographic film to produce a permanent image.

Tools of a BiologistScanning Electron Microscope (SEM)

• SEM get their name from a pencil like beam of electrons that scans back and forth

across the surface of a specimen.

•Electrons that bounce off the specimen are picked up by detectors that provide

information to form a three-dimensional picture.

•SEM can magnify objects up to 300,000 times.

Tools of a BiologistPROBE MICROSCOPES

• A new class of microscopes developed in the 1980s.

•They do not use lenses to produce images.

• These instruments trace the surfaces of a sample with a fine tip known as a probe.

•They are called scanning probe microscopes.

Tools of a BiologistPROBE MICROSCOPES

•Scanning probe microscopes have even made it possible to observe single atoms.

• Unlike electron microscopes, scanning probe microscopes do not require that specimens be placed in a vacuum.