6 A Tour of the Cell Flashcards
Define Magnification.
The ratio of an object’s image size and its real size.
Define Resolution.
The smallest distance two points can be separated yet still discernable.
What are the forms of electron microscopy?
SEM (scanning electron microscope) and TEM (transmission electron microscope).
How do SEM microscopes operate?
In SEM the sample is coated in gold and electrons are fired at it. This stimulates the gold atoms to release secondary electrons which are detected.
How do TEM microscope operate?
Electrons are passed through the sample which has been stained with heavy metals so that certain regions have a higher electron density. The electrons from the TEM that pass near these regions are scattered more, allowing an image to be formed.
How can the various parts i.e. organelles of a cell be separated?
They can be ‘homogenised’ in a blender to disconnect all the parts and then placed in a centrifuge to separate them based on density.
What may be on the surface of a bacterium?
Cillia, Flagella and Fimbriae.
What are Cillia?
Fine projections on the surface of the bacterium that can be moved, like oars, for propulsion.
What are flagella?
A long projection that can be moved to propel the bacterium.
What are Fimbriae?
Fine projections that can be used to attach to things like limpets on a rock.
What structures of a prokaryote are used for protein synthesis?
- The nucleiod is where the DNA is located but is not membrane bound.
- Like eukaryotes, prokaryotes have ribosomes for protein synthesis.
Do prokaryotes have a cytoplasm?
Yes.
What surrounds the cytoplasm of a prokaryote? (in order from inside to out)
- A plasma membrane which surrounds the cytoplasm.
- Cell wall - a tough rigid structure
- Capsule - a jellylike outer coating found on some bacteria.
Which cells are typically large: prokaryote or eukaryote?
Eukaryote.
How large are bacteria typically?
1-5 micrometers in diameter.
How large is a typical eukaryotic cell?
10-100 micrometers in diameter.
What is the function of the plasma membrane?
To surround and protect the cytoplasm and its components and to regulate the intake and release of substances such as oxygen, nutrients and wastes.
Why are cells so small?
To provide them with a greater surface area to volume ration and thus allow rapid diffusion and thus exchange with their surroundings.
How can the SA/V ratio be maximised?
- Small cells
- Highly folded structures i.e. the cerebrum.
- Fine projections on the surface known as microvilli (not necessarily intestinal)
How does a eukaryote fundamentally differ from a prokaryote?
It has membrane bound organelles.
What are most biological membrane composed of?
A phospholipid bilayer i.e. two layers of phospholipids.
Where are flagella seen in eukaryotes?
In the sperm of plants and animals etc.
What are the basic organelles/structures which are present in both plant and animal cells?
Nucleus, Endoplasmic Reticulum, Cytoskeleton, Peroxisome, Mitochondria, Golgi apparatus and Ribosomes.
What is the nucleus composed of?
The nuclear envelope, the nucleolus and chromatin.