Starter Using page 19 first few paragraphs under the prokaryotic cells title work out the answers to the following 1. Give definitions of the terms prokaryotic and eukaryotic cells 2. Which do you think evolved first eukaryotic or prokaryotic cells?

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

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

Membrane Prokaryotic cells have only one membrane at the surface – cell surface 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 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 Nuclear membrane, mitochondria, chloroplasts, ER, golgi, nucleus and golgi vesicle

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

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

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

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

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

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

3 main differences Nucleus Nucleus DNA DNA Organelles Organelles

Typical exam questions 1. Complete the table to show 3 ways in which prokaryotic and eukaryotic organisms differ in the structure of their cells prokaryoticeukaryotic

2. The table below compares the features of typical eukaryotic and prokaryotic cells (i) Complete the table by placing a tick, cross or sometimes present (4) (ii) Outline the roles of the golgi apparatus and the ribosomes (2) Eukaryotic cell Prokaryotic cell Cell wall Sometimes present √ Nuclear envelope √ Golgi apparatus X Ribosomes√ flagellum Sometimes present

3. The following table compares some of the features of prokaryotic and eukaryotic animal cells Complete the table using ticks and crosses Prokaryotic cells Eukaryotic cells DNA present √√ Nuclear envelope present Cell wall present Plasmids present in cytoplasm Naked DNA present

The problem with plasmids

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