PROKARYOTIC CELLS Topic 2.2 IB Biology Miss Werba

TOPIC 2 - CELLS 2.1 CELL THEORY 2.2 2.5 CELL DIVISION PROKARYOTIC CELLS 2.3 EUKARYOTIC CELLS 2.4 MEMBRANES 2.5 CELL DIVISION J WERBA – IB BIOLOGY 2

THINGS TO COVER Ultrastructure of a prokaryotic cell Functions of cell structures Structures identifiable under an EM Binary fission J WERBA – IB BIOLOGY 3

PROKARYOTIC CELLS What differences can you see? 2.2 PROKARYOTIC CELLS What differences can you see? J WERBA – IB BIOLOGY 4

PROKARYOTIC CELLS Prokaryotic cells were the first to evolve 2.2 PROKARYOTIC CELLS Prokaryotic cells were the first to evolve Perform all functions of life Remember: MRS C GREN They have no nucleus They have no membrane-bound organelles J WERBA – IB BIOLOGY 5

BINARY FISSION Command term = STATE 2.2.4 BINARY FISSION Command term = STATE Prokaryotic cells divide by binary fission Basically, one cell splits into two! DNA replicates and attaches to cell membrane Cell growth pulls DNA loops apart (cytokinesis) Cell wall growth between loops separates cell into two. J WERBA – IB BIOLOGY 6

PROKARYOTIC CELLS E. coli 2.2.3 PROKARYOTIC CELLS E. coli J WERBA – IB BIOLOGY 7

PROKARYOTIC CELLS E. coli 2.2.1 PROKARYOTIC CELLS E. coli ribosome (70S) cell membrane cell wall slime capsule flagellum cytoplasm plasmid nucleoid region (DNA) pili J WERBA – IB BIOLOGY 8

PROKARYOTIC CELLS E. coli 2.2.1 PROKARYOTIC CELLS E. coli J WERBA – IB BIOLOGY 9

PROKARYOTIC CELLS Cell wall Cell membrane Cytoplasm Nucleoid Plasmid 2.2.2 PROKARYOTIC CELLS Cell wall A rigid outer layer that maintains shape and protects the cell from damage or bursting if internal pressure is high Cell membrane Semi-permeable barrier that controls the entry and exit of substances Cytoplasm Fluid component which contains enzymes needed for cell metabolism Nucleoid Region of the cytoplasm which contains the DNA Plasmid Additional DNA molecule that can exist and replicate independently - it can be transmitted between bacterial species Ribosome Protein synthesis (prokaryotic ribosomes smaller than eukaryotic - 70S) J WERBA – IB BIOLOGY 10

PROKARYOTIC CELLS Slime Capsule Flagella (sing. flagellum ) 2.2.2 PROKARYOTIC CELLS Slime Capsule Protects against desiccation (drying out) and phagocytosis Flagella (sing. flagellum ) Long, slender projection which spins like a propeller, enabling movement Pili (sing. pilus) Hair-like extensions which can serve for attachment or communication. Attachment pili: Shorter in length, allow adhesion to other bacteria or surfaces Communication pili: Longer in length, allow for the exchange of plasmids J WERBA – IB BIOLOGY 11

QUESTION 1 The diagram below shows a bacterium. What structure does the part labelled X identify?

QUESTION 1 - answer X = Nucleoid

QUESTION 2 Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks)

What does the ‘OUTLINE’ command term ask for? QUESTION 2 Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks) Step 1: Command term What does the ‘OUTLINE’ command term ask for?

QUESTION 2 Give a brief account or summary. Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks) Give a brief account or summary. May or may not involved a diagram.

What vocab words would be relevant? QUESTION 2 Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks) Step 2: Relevant words What vocab words would be relevant?

Capsule Cell membrane Cell wall Cytoplasm QUESTION 2 Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks) Capsule Cell membrane Cell wall Cytoplasm Flagella Naked DNA Nucleoid Pili Plasmids Ribosomes

Can you put some order to your ideas? QUESTION 2 Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks) Step 3: Order ideas Can you put some order to your ideas?

QUESTION 2 Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks) Might be good to make a little flowchart or for this question, work from the outside in or vice versa

Step 4: Check the mark allocation QUESTION 2 Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks) Step 4: Check the mark allocation Do you have enough to get all the marks?

QUESTION 2 9 marks = 9 separate statements Escherichia coli is a unicellular organism, so each cell must carry out all of the processes required for life. Outline the functions of each of the structures in the cells of Escherichia coli. (9 marks) 9 marks = 9 separate statements There were at least 10 words on the list!

QUESTION 2 - answer cell wall protects the cell from damage; cell wall prevents the cell from bursting; plasma membrane pumps substances/carries out active transport; plasma membrane controls entry and exit of substances; cytoplasm contains enzymes that carry out metabolism; pili are used to connect bacterial cells/can pull bacteria closer together; flagella used for locomotion/movement of the bacterial cell; ribosomes synthesize proteins; (naked) DNA of main chromosome is located in the nucleoid (region); nucleoid initiates reproduction/binary fission; (naked) DNA/chromosome/nucleoid controls/determines cell structure/function; plasmids confer (luxury) functions such as disease resistance/antibiotic resistance/other; capsule protects cell/promotes adherence; If the answer includes any eukaryotic structures, award [8 max].