Chapter 7

1. Chapter 7 Cell Structure & Function, Part I

2. Cells… • Are so small that 50,000 can fit in this letter O • Build and break down macromolecules • Release energy from foods • Use energy to make cell parts

3. 7-1 Life Is Cellular Consider this statement: “The cell theory revolutionized how biologists thought about living things.”

4. Before microscopes… …people believed that diseases were caused by curses and supernatural spirits. No idea of organisms such as bacteria!

5. Anton van Leeuwenhoek (1600s) • First described natural (living) cells as seen through a simple microscope (a magnifying glass). Drew what he observed in a drop of water: “animalcules”.

6. Robert Hooke (1665) • First used the word “cells” to describe structure of slice of cork. Soon scientists accepted that cells were basic units of all forms of life.

7. Schleiden & Schwann (1830s) • Examined plants (Schleiden) and animals (Schwann) and concluded that “all living things are made up of cells”.

8. Rudolph Virchow • “Cells come from existing cells.”

9. Janet Plowe “The cell membrane is a defined physical structure.”

10. Review: Biologists and Their Discoveries That Led to The Cell Theory • First light microscope, cork made of “cells” • Simple microscope, living organisms in water • Plants made of cells • Animals made of cells • Cells come from existing cells • Cell membrane is physical structure • Robert Hooke • Anton van Leeuwenhoek • Matthias Schleiden • Theodor Schwann • Rudolph Virchow • Janet Plowe

11. The Compound Light Microscope • Has a series of lenses that magnify an object in steps. • Visible light is passed through the object and then through the lenses. • Allowed biologists to achieve greater magnification and see more details inside cells.

12. Magnification • The two lenses are called: • Eyepiece • Objective • The eyepiece has a magnification of “10x” • The magnification of the objective lenses vary and are marked on the lens • Total magnification = (Eyepiece) X (Objective) • Example: 10 X 40 = 400X

13. How Does a Microscope Work? the specimen the image the eye The image is always seen upside down and backwards from its actual position

14. The Parts of the Microscope and Their Function Maintains proper distance between lenses Magnification Hold objectives- rotates to change magnification Support body tube Magnification Supports slide Holds slide In place Focuses image Regulates amount of light Sharpens the image Reflects light towards eyepiece Supports microscope

15. Proper Procedures • Carry the microscope with one hand under the base while grasping the arm with the other hand • Place microscope ~5 inches from the edge of the table Be careful of the cord when moving around the lab tables!!

16. Proper Procedures 3. Rotate the nosepiece to obtain the proper objective lens Make sure the lens clicks into place!! 4. Look through the eyepiece and switch on the lamp This is your field of view!

17. Proper Procedures 5. Place slide on stage, center specimen over stage 6. Locate specimen on low power using coarse adjustment 7. Carefully switch to medium or high power 8. Focus image with fine adjustment Avoid damaging slide! Do not use course adjustment with high power!

18. Storing the Microscope Four steps prepare the microscope for storage: • the 10X objective is in place • the stage is all the way down • the power is off • the cord is wrapped around the base

19. The Cell Theory • All living things are composed of cells. • Larger organisms (like humans) many cells. • The cell is the basic unit of structure & function in living things. • Basic unit of matter --- atom. Basic unit of life --- cell. • New cells are produced from existing cells. • Cells come from the reproduction of previously existing cells making exact copies of themselves.

20. Basic Cell Structures in all Cells • Typical cells range in size from 5-50 micrometers. • Bacteria- 0.2 micrometers • Giant amoeba- 1000 micrometers (naked eye can see) • Cell membrane is thin, flexible barrier surrounding cell. Plants have strong cell wall to contain turgor pressure. • Protects cell while allowing interaction with environment.

21. Basic Cell Structures in all Cells • Nucleus or nucleoid- Structure or material that contains genetic material and controls activities. • Cytoplasm- “juice” material inside cell membrane- contains many important structures

22. Two Basic Cell Types: • Prokaryotes - no true nucleus or organelles • Eukaryotes - containing membrane-bound nucleus as well as membrane bound organelles

23. Prokaryotes • Organism with a cell that lacks internal structures surrounded by membranes. • Have cell membrane and cytoplasm • No nuclei, but contain DNA within cytoplasm • Most are single-celled organisms- smaller & simpler • All bacteria are prokaryotes • Carry out every activity associated with life • Grow, reproduce, respond to changes in environment

24. Eukaryotes • Vary in shape, some large • Have cell membrane and cytoplasm • Have nuclei and many other organelles • Some single-celled beings • Many multi-celled beings • All plants, animals, fungi, and many microorganisms are eukaryotes

25. 7-2 Eukaryotic Cell Structures

26. The Cell Membrane Location? • Outer boundary of animal and protist cells. Outer edge of cytoplasm. • Also called a plasmamembrane, it serves as the boundary between the cell and the external environment. • Flexible- allows cell to change its shape if needed. Function? • Controls the movement of materials that enter and exit the cell. • Oxygen Nutrients • Waste products Excess water

27. Cell Membrane cont’d • Some materials exit and enter through protein passageways. • Some materials pass directly through the membrane.

28. Cell Wall • Location? • Outer most boundary in plant, bacteria and fungi cells • In plants, cell walls contain cellulose molecules which form fibers to protect the cell & give it support. • In fungi, walls made of chitin, a nitrogen-containing polysaccharide. • Function? • Provides support and protection for the cell • Helps maintain cell shape

29. Nucleus • Function? • Is the organelle that manages cell function in a eukaryotic cell. • Surrounded by a nuclear envelope, four layers thick. Large pores allow materials to pass between the nucleus and the rest of the cell. • Contains DNA, the master instructions for building proteins. Stores hereditary information of DNA • Location? • In all cells but bacteria cells • Often most prominent structure in center of cell

30. Nucleus cont’d • DNA forms strands of chromatin, which is packed into chromosomes at reproduction. • Also inside the nucleus is the nucleolus, which produces tiny cell particles. These particles are ribosomes, which are the sites where proteins and enzymes are assembled. Ribosomes do not have a membrane.

31. Nucleolus Location? • Dark spherical mass inside the nucleus Function? • Assembly of ribosomes begin here

32. Nuclear Envelope Location? • Surrounds nucleus Function? • Double membrane layer that contains pores which allow material to move into and out of the nucleus • Steady stream of RNA and other info-carrying molecules to the rest of the cell

33. Assembly, Transport & Storage • Most cells need to make proteins and store other materials. Most of this work is done in the fluid of the cell- the cytoplasm.

34. Cytoplasm Location? • The clear fluid composing about 50% of the cell. • Contains many structures called organelles • Some cells may contain cytoskeleton Function? • Establishes living condition to supply and transport materials for cell activities

35. Assembly and Transport (cont’d) • Endoplasmic reticulum (ER): a folded system of membranes where the cell’s chemical reactions take place. Enzymes to make lipids are also found here Location? • Extend from nuclear envelop to cell membrane Description? Rough E.R.– contain ribosomes Smooth E.R. – do not contain ribosomes Function? • Transport materials • Rough E.R. modify proteins for secretion • Smooth E.R. contains enzymes that make lipids

36. Ribosome Location? • In nucleus, cytoplasm, and Rough E.R. Function? • Produce proteins following coded instruction that come from the nucleus

37. Protein Storage • Golgi apparatus: a series of membrane sacs that take lipids and proteins made on the ER and distributes them where needed- to other organelles and the cell membrane. Proteins travel in little packages called vesicles. • Vesicles may be sent out of the cell, absorbed into other organelles, or stay at the Golgi until needed.

38. Vacuoles Location? • Saclike structures in the cytoplasm Description? Animal & Protists – Small, multiple vacuoles Function? • Store materials such as water, salts, proteins and carbohydrates • Remove excess water from cell (contractile vacuole)

39. Plant Vacuoles Location? • Saclike structure in the cytoplasm Description? Plant cells – Single, large central vacuole Function? • Store materials such as water, salts, proteins and carbohydrates • Pressure in plant vacuole aid in support of plant cell (lack of water – wilting)

40. Lysosomes: Location? • Throughout the cytoplasm of the cell • Rare in plant cells • Function? • Small organelles filled with enzymes that break down lipids, carbohydrates and proteins from food into particles that can be used by the rest of the cell. • Also a “cell cleaner” to break down old organelles and dead pathogens.

41. Energy Transformers: Mitochondria Location? • Throughout the cytoplasm • More numerous in cells that have high energy requirements. Function? • Organelles that release energy in the form of ATP from stored food molecules (glucose) • The name of this process? Cellular Respiration Note: Mitochondria contain some of their own genetic info or DNA that is essential to the function of the mitochondrion.

42. Chloroplasts • Location? • Found in cytoplasm of plants, some protists and bacteria Chlorophyll pigment transforms light energy directly into chemical energy and stores it as sugars and starches. Chloroplasts contain stacks of sacs called grana surrounded by a fluid called stroma. • Function? • Use energy from sunlight to make energy-rich food molecules (glucose). • The name of this process? Photosynthesis Note: Chloroplasts contain some of their own genetic info or DNA that is essential to the function of the chloroplast.

43. Plant Mitochondria

44. Human Liver Cell Mitochondria

45. Structures for Support & Locomotion • Cytoskeleton: a framework of tiny rods and threads within the cytoplasm. • Provides support for organelles. • Helps maintain cell wall shape. • Composed of microtubules (hollow) and microfilaments (solid).

46. Structures for Support & Movement Location? • Extending from nucleus to cell membrane in some cells Description? • Made up of protein filaments called microtubules and microfilaments Function? • Helps cell maintain shape and involved in many forms of cell movement

47. Cilia & Flagella • Both are structures adapted for movement. • Cilia are short hairs that beat in a “wave”. Moves fluids over surface rather than moving cell itself. • Flagella are larger, whiplike projections.

48. Structures for Reproduction: Centrioles Location? • Paired structures just outside the nuclear envelope in the cytoplasm • Only in animal cells Function? • During cell division, centrioles separate and take up positions on opposite sides of the nucleus • Help organize the spindle that separate the chromosomes

49. Review: Cell Structures and Functions

50. Cell Quiz Answer Key E Smooth E.R. J Ribosome D Rough E.R. K Lysosome (Special vesicle) M Vesicle/Vacuole C Chromosome H Nucleus I Nucleolus E Smooth E.R. A Cell Membrane B Centriole F Golgi Apparatus G Mitochondrion M Vesicle/Vacuole