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Biology B2

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  1. Biology B2 Lesson 2: Bacteria

  2. Connect: Exam Practice • (a) The diagrams show a bacterial cell, a plant cell and an animal cell. Structure X is found in all three cells. • (i)   Complete the sentence by choosing the correct answer. Structure X is the (1): • A  cell membrane B  cell wall • Ccytoplasm Dnucleus

  3. Connect: Exam Practice • (ii)  Many bacteria have one or more flagella whereas most animal cells have no flagella. State one other difference between a bacterial cell and an animal cell. (1) • (b) (i) Scientists use microscopes to magnify cells. Choose from the following words to complete the sentences. (2) • Focusing wheel less objective lens • Light more • The magnification of a light microscope can be varied by changing the ______________. The electron microscope can magnify images _____ than the light microscope.

  4. Connect: Exam Practice • (ii)  The diagram shows a sperm cell that has been magnified 100000 times. • Calculate the actual length of the sperm cell. (2) • Length of sperm cell = .................................................................... mm • (iii) Explain why a human sperm cell contains more mitochondria than most other types of cell in the human body. (2)

  5. Connect: Exam Practice • (a) (i) A (1) • (a) (ii) Any one of the following points • bacterial cells have a cell wall (animal cells do not) (1) • bacterial cells do not have a nucleus (animal cells do) (1) • bacterial cells have circular DNA / chromosomal DNA (animal cells do not) (1) • bacterial cells have plasmids (1)

  6. Connect: Exam Practice • (b) (i)objective lens (1) more (1) (2) • (b) (ii)calculation (1) correct answer (1) • = 0.00130 / 1.3 × 10-3(2) • (b)(iii)An explanation including two of the following points: • mitochondria are sites of respiration for energy (1) • sperm requires a lot of energy (1) • for movement / swimming / to move the flagellum (1)(2)

  7. What Are We Learning • By the end of this lesson, you should: • Be able to describe the structure of a bacterial cell. • Relate the structure to the function of a bacterial cell.

  8. SMSC & RWCM • During this lesson, you will be developing social skills by working in groups. • We will be developing listening skills and will be using key words in the correct context.

  9. Today’s Learning Progress Step 1: Label the key parts of a bacterial cell Progress Step 2: Explain the function of the key part of a bacterial cell Progress Step 3: Compare the function of electron and light microscopes Increasing Difficulty

  10. Think • Plant and animal cells have organelles. • Plant cells have some additional organelles to animal cells. • What does a bacterial cell look like? • How can we see bacteria and other cells so clearly?

  11. Bacterial Cells • Bacterial cells are more simple than animal and plant cells. • They have cytoplasm, a cell membrane, a cell wall and genetic material. • Draw what you think a bacteria looks like.

  12. This bacterial cell has a FLAGELLUM which could be used for movement or to damage other cells with.

  13. Genomic deoxyribonucleic acid is CHROMOSOMAL DNA. It contains the biological information that is passed on from one generation to the next. It is separate from Plasmid DNA.

  14. A plasmid is a small DNA strand that is separate from the CHROMOSOMAL DNA. Plasmid DNA is able to replicate and carries genes that may aid the survival of the organism. For example: antibiotic resistance.

  15. Note: This bacterial cell has NO distinct NUCLEUS due to its lack of a nuclear membrane.

  16. Many flagella

  17. Examiners Tip! Bacterial cells have a cell wall and only one circular chromosome but no nucleus. Bacteria don’t always have a flagellum

  18. TASK: • Draw a bacterial cell and label it with the following key words: Cell Membrane Cell Wall Cytoplasm Chromosomal DNA Flagellum Plasmid DNA

  19. Task: Copy And Complete

  20. Task: Copy And Complete

  21. Simple Microscopy Seeing the bigger picture.

  22. Magnification x1500 Magnification X2 000 000 Light Microscope Electron Microscope Light passes through the specimen and then through the magnifying lenses so you can see the object much bigger. Passes a beam of electrons through the specimen to magnify it

  23. A light microscope shows us bacteria don't have a nucleus. An electron microscope shows us that bacteria have two types of DNA, chromosomal and plasmid DNA.

  24. Task • Complete Worksheet 2.2d. • Stick the completed sheet into your exercise book. • Try worksheet 5.4 ‘Cell Structure’.

  25. What Are We Learning • By the end of this lesson, you should: • Be able to describe the structure of a bacterial cell. • Relate the structure to the function of a bacterial cell.

  26. Reflection: What Do You Know Now? Bacteria