Starter

1. Starter Using page 19 first few paragraphs under the prokaryotic cells title work out the answers to the following • Give definitions of the terms prokaryotic and eukaryotic cells • Which do you think evolved first eukaryotic or prokaryotic cells?

2. Learning objectives • Recall the differences between prokaryotic and eukaryotic cells • Describe the differences in the DNA of these cells • Create a hypothesis of eukaryotic cell evolution - hwk

3. Bacterial cells –prokaryotic • Still show all the characteristics of living things • Sheet to fill in as we go through the differences in the structure

4. Membrane • Prokaryotic cells have only one membrane at the surface – cell surface membrane • You should be able to put 7 no’s in the prokaryotic column of your table • Nuclear membrane, mitochondria, chloroplasts, ER, golgi, nucleus and golgi vesicle

5. Cell wall – always present • Made of peptidoglycan instead of cellulose • Peptidoglycan often called murein

6. Ribosomes – always present • Smaller than those of a eukaryotic cell • 20nm in prokaryotes (70s) • 30nm in eukaryotes (80s)

7. DNA • In the form of a single loop = circular • Eukaryotic DNA is in strands = linear • Many prokaryotes have additional loops of DNA called plasmids (not essential for life) • In eukaryotic cells histone proteins attach to the DNA strand • In prokaryotic cells no histone proteins • No nucleus in prokaryotic cells but general area that the main DNA is found is called the nucleoid

8. Energy production • No mitochondria but energy needs to be released just the same • Cell surface membrane has infolded regions called mesosomes • Enzymes for respiration

9. Some can photostnthesise • No chloroplasts Photosynthetic forms do have membraneous vesicles where photosynthetic pigments (chlorophyll molecules) are located. These structures are called thylakoids.

10. Flagella • Eukaryotic and prokaryotic flagella have different internal structures • Function is the same – movement of cell

11. 3 main differences • Nucleus • DNA • Organelles

12. Typical exam questions • Complete the table to show 3 ways in which prokaryotic and eukaryotic organisms differ in the structure of their cells

13. The table below compares the features of typical eukaryotic and prokaryotic cells • Complete the table by placing a tick, cross or sometimes present (4) • Outline the roles of the golgi apparatus and the ribosomes (2)

14. The following table compares some of the features of prokaryotic and eukaryotic animal cells Complete the table using ticks and crosses

15. The problem with plasmids

16. Homework – on paper • Mitochondria and chloroplasts contain small loops of DNA. They also contain ribosomes that are the same size as prokaryotic ribosomes. • Suggest an explanation for these features