#2.2. Cell structure - Syllabus 2016 - 2018

1.1 The microscope in cell studies

1.2 Cells  as the  basic units of living  organisms

All organisms are composed of cells. Knowledge of their structure and function  underpins much of biology. The fundamental differences between eukaryotic and prokaryotic cells are explored and provide useful biological background for the section on Infectious disease. 

Viruses are introduced as non-cellular structures, which gives candidates the opportunity to consider whether cells are a fundamental property of life.

The use of light microscopes is a fundamental skill that is developed in this section and applied throughout several other sections of the syllabus. Throughout the course, photomicrographs and electron micrographs from transmission and scanning electron microscopes should  be studied.

Learning Outcomes

Candidates should  be able to:

1.1 The microscope in cell studies

An understanding of the principles  of microscopy shows why light and electron microscopes have been essential in improving our knowledge of cells.
a)   compare the structure of typical animal and plant cells by making temporary preparations of live material  and using photomicrographs
b)   calculate the linear magnifications of drawings, photomicrographs and electron micrographs
c)   use  an eyepiece graticule  and stage micrometer scale to measure cells and be familiar with units (millimetre, micrometre, nanometre) used in cell studies
d)   explain and distinguish between resolution and magnification, with reference to light microscopy and electron microscopy
e)   calculate actual sizes  of specimens from drawings, photomicrographs and electron micrographs

1.2 Cells  as the  basic units of living  organisms

The cell is the basic  unit of all living organisms. The interrelationships between these cell structures show how cells function  to transfer energy, produce biological molecules including proteins and exchange substances with their surroundings.

Prokaryotic  cells and eukaryotic cells share some features, but the differences between them illustrate  the divide between these two cell types.

a) describe and interpret electron micrographs and drawings of typical animal and plant cells as seen with the electron microscope

b) recognise the following cell structures and outline  their functions:

•   cell surface membrane
•    nucleus, nuclear  envelope and nucleolus
•   rough endoplasmic reticulum
•   smooth endoplasmic reticulum
•   Golgi body (Golgi apparatus or Golgi complex)
•   mitochondria (including small circular DNA)
• ribosomes (80S in the cytoplasm and 70S in chloroplasts and mitochondria)
•   lysosomes
•    centrioles and microtubules
•   chloroplasts (including small circular DNA)
•   cell wall
•   plasmodesmata
•   large permanent vacuole  and tonoplast of plant cells

c) state that  ATP is produced in mitochondria and chloroplasts and outline  the role of ATP in cells

d) outline  key structural features of typical prokaryotic  cells as seen in a typical bacterium (including: unicellular, 1-5µm diameter, peptidoglycan cell walls, lack of organelles surrounded by double  membranes, naked  circular DNA, 70S ribosomes)

e) compare and contrast the structure of typical prokaryotic  cells with typical eukaryotic cells (reference to mesosomes should not be included)

f) outline  the key features of viruses as non-cellular structures
(limited to protein  coat and DNA/RNA)