Cell Structure

1. Cell Structure OCR AS Biology Unit 1: Cells, Exchange and Transport

2. Cell theory • The cell is the fundamental unit of life. All organisms, whatever their type or size, are composed of cells. The modern theory of cellular organisation states:- • All living things are composed of cells and cell products. • New cells are formed only by the division of pre-existing cells • The cell contains inherited information (genes), which is used as instructions for growth, functioning and development. • The cell is the functioning unit of life; the metabolic reactions of life take place within the cells.

3. Plan Diagrams – dicotyledonous leaf

4. Cell Biology and Microscopy • When Scientists began to observe cells, they started with simple microscopes • There are two different types of microscope both use a form of radiation to create an image of the specimen: • Light microscope – uses light • Electron microscope – uses electrons

5. Using a light microscope • Magnification • Number of times larger an image is compared with the real size of the object • Resolution • The ability to distinguish between two separate points

6. Structure of a generalised animal cell (diameter ~ 20ųm)

7. Structure of a generalised plant cell

8. Examination cells -staining • What is the value of staining cells before you look at them under the microscope?

9. Microscopy and magnification OCR AS Biology

10. Microscopes • Light microscope • Long wavelength • Can only distinguish between two objects if they are 0.2µm apart. • Electron microscope • Shorter wavelengths • Can distinguish between objects 0.1nm apart

11. Magnification • How many times bigger the image is compared to original subject. • If asked to calculate the size of an object

12. Magnification • When calculating magnification make sure the units of length are the same for both object and image

13. Magnification - example • Object 100nm in length • How much is it magnified in a photo? • Measure object in photo (10mm long)

14. Magnification - example • The measurements need converting to the same unit (usually the smallest) • There are 10 000 000nm in 10mm • Magnification is: • 100 000 times

15. The effect of progressive magnification of a portion of human skin

16. Structure of plant and animal cells under an electron microscope OCR AS Biology

17. The Electron Microscope • Two main advantages • High resolving power (short wavelength of electrons) • As electrons negatively are charged the beam can be focused using electromagnets • As electrons are absorbed by molecules of air, a near-vacuum has to be created within the chamber of an electron microscope.

18. The Electron Microscope • Two types • Transmission Electron Microscope (TEM) • Scanning Electron Microscope (SEM)

19. Comparison of advantages and disadvantages of the light and electron microscopes

20. Comparison of advantages and disadvantages of the light and electron microscopes

21. Comparison of pathways of the light and electron microscopes

22. Learn to label! Ultrastructure of an animal cell as seen through an electron microscope

23. Ultrastructure of an Animal Cell

24. Ultrastructure of a plant cell as seen through an electron microscope

25. Ultrastructure of a Plant Cell

26. Revision Activity – Cell StructureAnimal Cell • On the NEXT few slides: • How many structures can you identify? • Look at the cells alive animation – how many have you correctly identified? • Label the paper copy of the diagram of an animal cell

28. Animal Cell

29. Animal cell - answers

30. Activity – Cell StructurePlant Cell • In pairs label the diagram of the plant cell given. • How many structures can you identify? • Look at the cells alive animation – how many have you correctly identified? • Label the paper copy of a diagram of a plant cell

32. Plant cell

33. Plant cell - answers

34. Activity:Introduction to organelle function • Using the cards, match up organelle, position and function.

36. Organelle Structure and function OCR AS Biology FOUNDATION

37. Nucleus

38. Structure of nucleus • Nuclear envelope • Nuclear pores • Nucleoplasm • Chromatin • nuceolus

39. Function of the nucleus • Acts as the control centre of the cell through the production of mRNA and protein synthesis • Retain genetic material of the cell (DNA / chromosomes) • Start the process of cell division

40. Structure of Nucleus • Chromatin • DNA and associated proteins, chromatin condenses into chromosomes when the cell divides. • nucleolus • Manufactures ribosomal RNA and assembles the ribosomes

41. Structure of Nucleus • Nuclear envelope • Controls entry and exit of materials • Outer membrane continuous with endoplasmic reticulum • Nuclear pores • Passage of large molecules (mRNA) out of nucleus

42. Chloroplasts

43. Structure and Function of Chloroplasts • Chloroplast envelope • Entry and exit of substances • Stroma • Enzymes for the light independent stages of photosynthesis • Grana (thylakoids/lamellae) • Light dependent stage of photosynthesis • Starch grains • Temporary stores of carbohydrates

44. Mitochondria

45. Structure of Mitochondria • Double membrane • Inner membrane folded into cristae which provide a large surface area • Matrix • DNA, enzymes and ribosomes

46. Function of Mitochondria • Site of Krebs cycle and oxidative phosphorylation in aerobic respiration • Production of energy rich ATP molecules from carbohydrates

47. Endoplasmic reticulum

48. Endoplasmic reticulum • Membranes spreading through the cytoplasm of cells, continuous with the nuclear membrane • Enclose flattened sacs called cisternae • Rough endoplasmic reticulum • Ribosomes present on outer surface of membrane • Smooth endoplasmic reticulum • No ribosomes, tubular in appearance.

49. Function of endoplasmic reticulum • RER • Provide LSA for synthesis of proteins • Provides a pathway for the transport of materials (esp. proteins) throughout the cell. • SER • Synthesis, stores and transports lipids and carbohydrates • Contains lytic enzymes (liver cells)

50. Ribosomes