Biology: Cell structure

There are two types of cell; Prokaryotic and eukaryotic.

Eukaryotic cells are full of organelles:

Organisms Can Be Prokaryotes or Eukaryotes:

1. Prokaryotic organisms are Prokaryotic cells 'Single Celled Organisms'

-Eukaryotic organisms are made up of Eukaryotic Cells

2. Both types contain Organelles 'Parts of cells'

Plant and Animal cells are both Eukaryotic

Eukaryotic cells:

Organelles and Functions:

• Involved in protein production

1. Proteins made at the RIBOSOMES

2. Ribosomes on the RER make proteins that are Excreted or attached to the cell membrane. Free ribosomes in cytoplasm make proteins that stay in cytoplasm

3. New proteins that are produced at the RER are FOLDED and PROCESSED in the RER

4. Then TRANSPORTED from the ER to GOLGI APPARATUS in VESICLES

5. Proteins undergo further processing at golgi apparatus

6. Enter more VESICLES to be transported around the cell.

E.g. Glycoproteins found in Mucus move to cell surface and are secreted.

1. Organelles are surrounded by CYTOPLASM. 'Network of protein threads and a solution of chemicals'

Protein threads = CYTOSKELETON

2. In Eukaryotic cells cytoskeleton arranged as MICROFILAMENTS and MICROTUBULES:

1. Microtubules and Microfilaments support Cell Organelles:

 'Keep them in position'

2. Strengthen cell and help maintain its shape.

3. Responsible for Transport of materials within cell.

E.g Movement of Chromosomes during cell division.

4. Proteins of cytoskeleton cause the cell to move.

 E.g Movement of Cillia and Flagella caused by the cytoskeletal protein filaments that run through them.

Single cells that have flagellum: Cytoskeleton propels whole cell!

Prokaryotes: Different kind of cell!

1. A tenth the size of Eukaryotic cells

2. Normal microscopes aren't powerful enough to see the internal structure.

3. Diagram showing a bacterial cell as seen under an ELECTRON MICROSCOPE

MAGNIFICATION: SIZE

RESOLUTION: DETAIL

MAGNIFICATION is how much BIGGER the image is than the specimen.

FORMULA:

RESOLUTION is how DETAILED the image is; How well the microscope DISTINGUISHES between TWO POINTS that are CLOSE TOGETHER

LIGHT MICROSCOPES

1. Light Microscopes use light

2. Have a LOWER RESOLUTION than electron microscopes.

Max resolution: 0.2 mirometres

3. Maximum useful MAGNIFICATION = x1500

Electron Microscopes use ELECTRONS instead of light.

Have a HIGHER RESOLUTION and give MORE DETAILED IMAGES.

TWO KINDS:

1. Transmission electron Microscope - Use ELECTROMAGNETS to focus a BEAM OF ELECTRONS then transmitted THROUGH the specimen. DENSER parts abosb MORE ELECTRONS - Look Darker Good: High Resolution images-- only used on THIN SPECIMENS.

MAX RESOLUTION: 0.0001 Micrometres MAX MAGNIFICATION: 0.005 Micrometres

2. Scanning Electron Microscope- SCAN a beam of electrons across a specimen. Images produced show the SURFACE of a specimen and can be 3D. -Lower Resolution Images than TEM's

MAX RESOLUTION: more than x1 000 000 MAX MAGNIFICATION: Less than x1 000 000

1. In light and TEM's, the beam of light passes through the object being viewed.

Image is produced because some parts ABSORB MORE LIGHT than others.

2. Sometimes the object is completely TRANSPARENT. The light rays then just pass STRAIGHT THROUGH and the whole thing just looks WHITE

3. To get around this the object can be STAINED: