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BiologyGuide.app > BIOL1 > Cell Structure

Cells

You need to be able to use your knowledge of the structure of cells and the function of the organelles to interpret electronmicrographs of cells. In particular the epithelial cells lining the small intestine. These are cells which are specialised for absorbing the products of digestion. They will therefore have a large surface area provided by the microvilli and due to the need for active transport across their cell membranes they will contain a large number of mitochondria providing them with ATP. Epithelial cells also secrete enzymes and other proteins. This means that they will have a large and visible endoplasmic reticulum, Golgi apparatus to allow protein production and secretion.

Below is a list of the most important organelles that you are required to know about. It is worth you using textbooks and perhaps even other websites such as www.cellsalive.com to look at actual images of different types of cells and their organelles.

Nucleus

Plasma Membrane

Microvilli

Lysosomes

Mitochondria

Ribosomes

Endoplasmic Reticulum (ER)

Golgi Apparatus

Techniques used in Cell Biology

Feature

Optical microscope

Electron microscope

Radiation

Light

Electrons

Magnification

400x (max1500)

≈500 000x

Resolution

2µm

1nm / 0,001µm
Electrons have a small wavelength
Thus, higher resolution

Vacuum in microscope

Absent

Present

Specimen is

- Alive or dead
- Stained

- Dead (vacuum!)

Transmission microscope:
Electrons pass through internal
structure of specimen

Scanning microscope:
Beams of electrons are reflected
off specimens surface. Allows a
three dimensional view

Cell Fractionation

To study the function of individual organelles large numbers of isolated organelles need to be obtained. Cell fractionation is used to gather these organelles.

It is worth looking on the internet or in your text books for a step by step diagram of the process to use alongside this explanation.