Lessons 15–16 · 2 lessons · A. Zikiryayev, A. To‘xtayev, I. Azimov, N. Sonin. Biology. Basics of Cytology and Genetics, Grade 9, revised and expanded 5th edition. “Yangiyul Poligraph Service”, Tashkent, 2019
15
Prokaryotic and eukaryotic cells
Textbook: pp. 47–48
GoalCompare prokaryotic and eukaryotic cells, and plant, animal and fungal cells, naming similarities and differences.
Cellular life is divided into two groups: prokaryotes (bacteria, blue-green algae, i.e. cyanobacteria, and archaea) and eukaryotes (fungi, plants, animals). Both have a plasma membrane, cytoplasm, ribosomes, DNA and RNA; protein synthesis takes place on ribosomes and hereditary information is passed on by nucleic acids. Prokaryotes lack a formed nucleus and organelles such as mitochondria and endoplasmic reticulum: the circular DNA lies in the nucleoid zone of the cytoplasm, the cell is on average 1–10 µm, and instead of mitosis there is simple division into two. Eukaryotes have a nucleus, cells are usually larger (10–100 µm) and divide by mitosis. A plant cell has a cellulose wall, plastids and a large vacuole, which an animal cell lacks; a fungal cell has a chitin-like wall, no plastids and heterotrophic nutrition. When a plant cell divides, a partition forms across the middle, whereas in an animal cell the membrane pinches inward.
Worked examples
The bacterium Escherichia coli: circular DNA in the nucleoid, no mitochondria, multiplies by division into two: a prokaryote.
A mushroom cell: has a nucleus, a chitin-like wall, no chloroplasts, heterotrophic: a fungal eukaryote.
Class activity
“Venn diagram”. Draw two overlapping circles on the board (prokaryote, eukaryote). Place the feature cards (nucleus, ribosome, DNA, mitochondrion, circular DNA, plasma membrane) in the right region.
Practice
1
State two features common to prokaryotic and eukaryotic cells.
Both have a plasma membrane and ribosomes; both have DNA and RNA, and protein is made on ribosomes.
2
Write two differences between a fungal and a plant cell.