Cell ultrastructure

Question 1

Define the term “limit of resolution”

Answer 1

The minimum distance at which two objects can be distinguished

Question 2

Why do electron microscopes have finer resolution than light microscopes?

Answer 2

Electrons have a shorter wavelength than visible light. As wavelength decreases, resolution increases

Question 3

Describe the differences between prokaryotic and eukaryotic cells

Answer 3

Prokaryotes have an external membrane but no internal membranes. All biochemical processes occur in the same compartment
Eukaryotes are compartmentalised by internal membranes
ensure can draw both types of cell

Question 4

Describe the structure and function of the plasma membrane (plasmalemma)

Answer 4

A selective, structural barrier between the cell and outside area. Formed of a phospholipid bilayer embedded with peripheral proteins, integral proteins and cholesterol.
Functions:
-cell-cell recognition
-transport into and out of the cell: selective permeability
-in exocytosis and endocytosis
-intercellular adhesion
-as a receptor site for signalling proteins
-impermeable barrier to most water-soluble molecules
-initiator and controller of second-messenger systems

Question 5

Describe the structure and function of the glycocalyx

Answer 5

The ‘cell coat’. Made up of oligosaccharide and polysaccharide side chains on the outside of the plasma membrane,

Question 6

Describe the structure and function of the nucleus

Answer 6

Inner and outer nuclear membrane. Outer membrane is studded with ribosomes, and is in places continuous with the rough endoplasmic reticulum. Nulcear pores are created in areas where the two membranes fuse, and these permit communication between the nucleoplasm and cytoplasm.
The nucleus has chromosomes and is the site of RNA transcription (tRNA, mRNA and microRNA).
The nucleolus is the site of rRNA transcription, and is the site of assemly of ribosomal proteins and rRNA into the small and large ribosomal subunits.