Chapter 7: A View of the Cell

1. Chapter 7: A View of the Cell Chapter 7: A View of the Cell

2. Section 1: The Discovery of Cells

3. Microscopes enabled scientists to view and study cells, the basic units of living organisms. • In the 1600s, Anton von Leeuwenhoek described living cells as seen through a simple light microscope.

4. Robert Hooke was the first scientist to show evidence that organisms are made up of cells. • He used a compound microscope to magnify a thin slice of cork.

5. Two German scientists, Matthias Schleiden and Thomas Schwann developed the cell theory. • The cell theory is made up of three main ideas: 1) All organisms are composed of one or more cells. 2) The cell is the basic unit of structure and organization. 3)All cells come from preexisting cells.

6. Think about this! ?? • Which is NOT a way that the figure above is a model of cellular theory? • a. bricks are small units in a building • b. bricks are solid • c. there are many bricks in a building • d. bricks are organized to make a larger unit

7. Think about this! ?? • Which is NOT a way that the figure above is a model of cellular theory? • a. bricks are small units in a building • b. bricks are solid • c. there are many bricks in a building • d. bricks are organized to make a larger unit

8. A electron microscope is an instrument that allows scientists to magnify, view, and photograph dead cells or organisms by using a beam of electrons instead of light.

9. SEM (scanning electron microscope) are used by scientists to scan the surfaces of cells to learn their three-dimensional shape. • TEM (transmission electron microscope) allows scientists to study the structure contained within a cell. • STM (scanning tunneling microscope) uses the flow of electrons to create computer images of atoms on the surface of a molecules. Burdock weed embryo Gold

10. Small specialized structures in cells are called organelles. • The two basic kinds of cells are prokaryotic and eukaryotic. Prokaryotic Eukaryotic

11. A prokaryote is an organism with a cell that lacks internal structures surrounded by membranes. • Most of these organisms are unicellular.

12. A eukaryote is an organism that has cells containing internal, membrane-bound structures. These structures are called organelles. • The central membrane-bound organelle that manages or controls cellular functions is the nucleus.

13. Section 2: The Plasma Membrane

14. Your cells need nutrients such as glucose, amino acids, and lipids to function. • Plasma membrane- the flexible boundary between the cell and its environment that allows a steady supply of nutrients to come into the cell.

15. The process of maintaining balance in the cell’s environment is homeostasis. • Selective permeability is a process in which a membrane allows some molecules to pass through while keeping others out. Click here for video

16. Water enters the molecule freely through the plasma membrane. • Other particles must be allowed into the cell only at certain times and in certain amounts and through certain channels. • The plasma membrane is composed of a phospholipid bilayer, which has two layers of phospholipids back-to-back.

17. Carbohydrate Transport protein Phospholipid polarhead Phospholipid nonpolar tail Cholesterol Plasma Membrane

18. Cholesterol helps to stabilize the phospholipids by preventing their fatty acid tails from sticking together. • High levels of cholesterol in blood are associated with reduced blood flow in blood vessels.

19. Transport proteins move needed substances or waste materials through the plasma membrane.

20. Section 3: Eukaryotic Cell Structure

21. Cell Boundaries • The plasma membrane is a flexible boundary of cell. • Plant cells, fungi, bacteria, and some protists have an additional boundary, cell wall.

22. The cell wall is a fairly rigid structure located outside the plasma membrane that provides additional support and protection. • A plant cell wall is composed of a carbohydrate called cellulose which forms a thick tough mesh of fibers.

23. The Nucleus and Cell Control • The nucleus is the leader of the eukaryotic cell because it contains the directions to make proteins.

24. Nuclear Membrane- Surrounds nucleus- Composed of two layers- Numerous openings for nuclear traffic Nucleolus- Spherical shape- Visible when cell is not dividing- Contains RNA for protein manufacture Nuclear Membrane Nucleolus

25. Every part of the cell depends on proteins, so by containing the blueprint to make proteins the nucleus controls the activity of the organelles. • The master set of directions for making proteins is contained in chromatin, which are strands of the genetic material, DNA.

26. When a cell divides, the chromatin condenses to form chromosomes. • Chromosomes- Usually in the form of chromatin • Contains genetic information- Composed of DNA- Thicken for cellular division- Set number per species (i.e. 23 pairs for human)

27. Within the nucleus is a prominent organelle called the nucleolus, which makes ribosomes. • Ribosomes are simple structures made of RNA and proteins.

28. Ribosomes • - Each cell contains thousands- Miniature 'protein factories'- Composes 25% of cell's mass- Stationary type: embedded in rough endoplasmic reticulum- Mobile type: injects proteins directly into cytoplasm Ribosome

29. Assembly, Transport, and Storage • Endoplasmic reticulum (ER), is the site of cellular chemical reactions. • The ER is arranged in a series of highly folded membranes in the cytoplasm.

30. Endoplasmic reticulum- Tubular network fused to nuclear membrane- Goes through cytoplasm onto cell membrane- Stores, separates, and serves as cell's transport system- Smooth type: lacks ribosomes- Rough type (pictured): ribosomes embedded in surface

31. Ribosomes in the cytoplasm are attached to the surface of the endoplasmic reticulum, called rough endoplasmic reticulum, where they carry out the function of protein synthesis. • The ribosome’s job is to make proteins.

32. Areas of the ER that do not have ribosomes are known as smooth endoplasmic reticulum • The smooth ER is involved in numerous biochemical activities, including the production of lipids.

33. After proteins are made they are transferred to another organelle called the Golgi apparatus. • The Golgi apparatus is a flattened stack of tubular membranes that modifies the proteins. • It sorts proteins into packages and packs them into membrane-bound structures called vesicles, to be sent to the appropriate destination.

34. Golgi apparatus • - Protein ‘packaging plant’- A membrane structure found near nucleus- Composed of numerous layers forming a sac

35. Vacuoles are membrane-bound compartments for temporary storage. It is used to store food, enzymes, and other materials needed by a cell. - Membrane-bound sacs for storage, digestion, and waste removal- Contains water solution- Contractile vacuoles for water removal (in unicellular organisms)

36. Lysosomes are organelles that contain digestive enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria. Lysosome- Digestive 'plant' for proteins, lipids, and carbohydrates- Transports undigested material to cell membrane for removal- Vary in shape depending on process being carried out- Cell breaks down if lysosome explodes

37. Energy Transformers • Protein production, modification, transportation, and digestion—all require energy.

38. Chloroplasts are cell organelles that capture light energy and convert it to chemical energy. • Chloroplasts contain the green pigment chlorophyll, which traps light energy and gives leaves and stems their green color.

39. Chloroplasts- A plastid usually found in plant cells • Contain green chlorophyll where photosynthesis takes place • The chemical energy generated by chloroplasts is stored in the bonds of sugar molecules until they are broken down by mitochondria.

40. Mitochondria are membrane-bound organelles in plant and animal cells that transform energy for the cell.

41. Mitochondria- Second largest organelle with unique genetic structure- Double-layered outer membrane with inner folds called cristae- Energy-producing chemical reactions take place on cristae- Controls level of water and other materials in cell- Recycles and decomposes proteins, fats, and carbohydrates, and forms urea

42. Cell biologists have discovered that cells have a support structure call the cytoskeleton. • The cytoskeleton is a network of tiny rods and filaments called microtubules and microfilaments.

43. Cytoskeleton - Composed of microtubules- Supports cell and provides shape- Aids movement of materials in and out of cells

44. Centrioles are organelles found in the cells of animals and most protists. • Centrioles play an important role in cell division.

45. Centrioles- Paired cylindrical organelles near nucleus- Composed of nine tubes, each with three tubules- Involved in cellular division- Lie at right angles to each other

46. Cilia are short, numerous projections that look like hairs. Paramecium

47. Flagella are longer projections that move with a whip-like motion.