Module 2 section 1: Cell structure

What’s cell ultrastructure?

The organelles and internal mechanisms of a cell, as seen through an electron microscope.

Function of the nucleolus?

Makes ribosomes.

Where are ribosomes usually located?

Floating in the cytoplasm, or attached to the rough endoplasmic reticulum.

Function of the rough endoplasmic reticulum?

Fold and process proteins made in the ribosomes.

Function of the smooth endoplasmic reticulum?

Synthesize and process lipids.

How are lsyosomes and vesicles different?

Lysosomes are specialised organelles that digest cellular components, whilst vesicles simply act as the method of transportation for the cell.

Golgi apparatus function?

Processes and packages proteins/lipids. Also makes lysosomes.

What are centrioles?

Small cylinders made of microtubules, that aid during cell division.

Describe protein production.

Proteins produced by ribosomes on the RER surface, where they are processed and packaged by the rough ER. They are then transported to the Golgi apparatus via vesicles, where they are further processed, and they can now be transported around the cell using vesicles.

What is the cytoskeleton comprised of, and what are its functions?

Made of microtubules and microfilaments, and is used to keep the cell in position, move cellular components around, strengthen the structure of the cell and allow it to move around in space.

What are some characteristics of prokaryotic cells?

They have no membranous organelles, their cell wall is made of polysaccharides (not chitin). They feature circular DNA, that isn’t bound in a nucleus.

What does resolution describe in microscopy?

How detailed an image is. More specifically, it describes the relative ease to distinguish different cellular components from each other.

How do TEMs work?

Fire a beam of electrons at a dead specimen, to view cellular components in 2D. Have the highest resolution of all microscopes, but require an ultra-thin sample to be observed properly

How are SEMs and TEMs different?

SEMs scan a beam of electrons on the dead specimen, with reflected electrons collected in a cathode ray tube to form a 3D image.

How are specimens treated for observation for electron microscopes?

Specimen is dead, and coated in heavy metal ions like lead to allow electrons to scatter correctly.

What is an eyepiece graticule, and why does it require calibration?

It is small ruler fixed onto the eyepiece, and measures in arbitrary units, and as such needs calibration using a stage micrometer. This means you can now use it to measure the size of the samples you’re observing.