Cambridge Pre-U Biology - 1.2 Prokaryotic Cells

This is part of the PowerPoint that covers section 1.2 in the Cambridge Pre-U Biology course. The full PowerPoint covers the following topics: Prokaryotic cell structure, asexual reproduction, introduction to antibiotics, bacterial pathogens.

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1. All cells can be split into two categories. 2 1 .2 Prokaryotic Cells Introduction Prokaryotic Cells Eukaryotic Cells The major difference is that prokaryotes don ’ t have a nucleus whereas eukaryotes do.

2. Animals, plants, fungi and protoctists are all made of eukaryotic cells, but we believe they all evolved from simpler cells that lack a nucleus called prokaryotic cells. Prokaryotic cells have some features in common with eukaryotic cells but also many differences. All bacteria are examples of prokaryotic cells. 3 1 .2 Pro karyotic Cells Introduction

3. Although they are basic organisms they are very important in biology. They can be found in a huge range of environments. They are responsible for the decay of organic material. They are pathogens of many organisms. We can exploit them and use them for processes in biotechnology. They contribute significantly to your health. 4 1 .2 Pro karyotic Cells Introduction

4. Structure of prokaryotic cells Antibiotics Reproduction Pathogenic bacteria 5

5. Outline key structural features of prokaryotic cells including: unicellular, 1-5 m diameter, peptidoglycan cell walls, lack of membrane-bound organelles, naked circular DNA, 70S ribosomes. Outline the structure of the cell walls of Gram-positive and Gram-negative bacteria and the significance of the structure for the use of antibiotics. Explain the mode of transmission and infection of Agrobacterium tumefaciens as an example of a bacterial pathogen. E xplain the mode of action of penicillin on bacteria (as an example of an antibiotic) and explain why penicillin does not affect viruses. O utline the mechanism of asexual reproduction by binary fission in a typical prokaryote. 1.2 Prokaryotic Cells Objectives

6. 1.2 Prokaryotic Cells Structure 7 Prokaryotes come in many shapes and sizes but the two main groups are the c occi (round) and bacilli (rod shaped). This often forms part of their binomial name e.g. Lactobacillus used to make yogurt.

7. 1.2 Prokaryotic Cells Structure 8 Here is a scanning electron micrograph of Escherichia coli bacteria Prokaryotes are very small ( 1 – 5 m m diameter ) compared to a typical eukaryotic cell (can be up to 40 m m in diameter ).

8. 1.2 Prokaryotic Cells Structure 9 You can see the size difference nicely on this image of a squamous epithelial cell from a human which is covered with many L actobacillus bacteria.

9. 1.2 Prokaryotic Cells Structure 10 These bacteria are called Staphylococcus aureus and will be discussed later in the course.

10. All prokaryotes possess the following structures : These additional structures are sometimes present: 1.2 Prokaryotic Cells Structure Cell wall Cell membrane Cytoplasm DNA Ribosomes 11 Capsule Infolding of membrane Plasmids Flagella P ili

11. Prevents the cell bursting and gives bacteria it’s shape. Made of murein which is peptidoglycan (a combination of polysaccharide and protein .) There are two types of cell wall which are discussed further in this section. 1.2 Prokaryotic Cells Structure – Cell Wall Cell wall 12

12. The cell membrane is broadly the same as the cell membrane in eukaryotes. The detailed structure of membranes is discussed in section 1.2. The cytoplasm is also similar but does not contain a cytoskeleton . 1.2 Prokaryotic Cells Structure – Cell membrane and cytoplasm Cell membrane 13 Cytoplasm

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