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PowerLecture: Chapter 3

PowerLecture: Chapter 3. Cells and How They Work. Learning Objectives. Understand the basic parts of eukaryotic cells. Understand the essential structure and function of the cell membrane.

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PowerLecture: Chapter 3

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  1. PowerLecture:Chapter 3 Cells and How They Work

  2. Learning Objectives • Understand the basic parts of eukaryotic cells. • Understand the essential structure and function of the cell membrane. • Know the forces that cause water and solutes to move across membranes passively and by active transport. • Understand how material can be imported into or exported from a cell by being wrapped in membranes.

  3. Learning Objectives (cont’d) • Describe the nucleus of eukaryotes with respect to structure and function. • Describe the organelles associated with the endomembrane system, and tell the general function of each. • Describe the cytoskeleton of eukaryotes and distinguish it from the endomembrane system. • Define a metabolic pathway and the types of substances that participate in it.

  4. Learning Objectives (cont’d) • Characterize an enzyme and what type of cofactors may be needed for its functioning. • Define ATP and describe the pathways for its formation within the cell. • Describe the process of cellular respiration with special reference to the quantity of ATP produced.

  5. Impacts/Issues When Mitochondria Spin Their Wheels

  6. When Mitochondria Spin Their Wheels • Mitochondria are specialized compartments in the cell that produce energy. • Mitochondrial disorders can cause reduced energy for cell use. • Luft’s syndrome is a rare disorder in which the mitochondria are misshapen and do not produce enough ATP. • Many mitochondrial disorders exist, but are rare; this means that pharmaceutical companies have little financial incentive to develop drugs for treatment.

  7. How Would You Vote? To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu. • Should pharmaceutical companies receive financial incentives (such as tax breaks) to search for cures for diseases that affect only a small number of people? • a. Yes, those that suffer from any disease, even if it is rare, deserve treatment. • b. No, the public shouldn't subsidize this research - let market forces take their course.

  8. Section 1 What Is a Cell?

  9. What is a Cell? • The cell theory has three generalizations: • All organisms are composed of one or more cells. • The cell is the smallest unit having the properties of life. • All cells come from pre-existing cells. Figure 3.3

  10. What is a Cell? • All cells are alike in three ways. • A plasma membrane separates each cell from the environment, but also allows the flow of molecules across the membrane. • DNA carries the hereditary instructions. • The cytoplasm containing a semifluid matrix (cytosol) and organelles is located between the plasma membrane and the region of DNA.

  11. What is a Cell? • There are two basic kinds of cells. • Prokaryotic cells (bacteria) do not have a separation of the DNA from the remainder of the cell parts. • Eukaryotic cells have a definite nucleus and membrane-bound organelles. cytoplasm DNA plasma membrane Figure 3.1

  12. Animation: Overview of Cells CLICKTO PLAY

  13. What is a Cell? • Why are cells small? • Most cells are so small they can only be seen by using light and electron microscopes. • Cells are necessarily small so that the surface-to-volume ratio remains low; this means that the interior will not be so extensive that it cannot exchange materials efficiently through the plasma membrane. Figure 3.2

  14. What is a Cell? • Membranes enclose cells and organelles. • A large portion of the cell membrane is composed of phospholipids, each of which possesses a hydrophilic head and two hydrophobic tails. • If phospholipid molecules are surrounded by water, their hydrophobic fatty acid tails cluster and a lipid bilayer results; hydrophilic heads are at the outer faces of a two-layer sheet with the hydrophobic tails shielded inside.

  15. fluid fluid one layer of lipids cross-section through lipid bilayer one layer of lipids Figure 3.4

  16. Animation: Lipid Bilayer Organization CLICKTO PLAY

  17. Section 2 The Parts of an Eukaryotic Cell

  18. The Parts of a Eukaryotic Cell • All eukaryotic cells contain organelles. • Organelles form compartmentalized portions of the cytoplasm. • Organelles separate reactions with respect to time (allowing proper sequencing) and space (allowing incompatible reactions to occur in close proximity).

  19. Animation: Parts of an Eukaryotic Cell CLICKTO PLAY

  20. Fig. 3.5, p. 44 nuclear envelope CYTOSKELTON nucleolus NUCLEUS DNA in nucleoplasm microtubules • RIBOSOMES microfilaments intermediate filaments • ROUGH ER MITOCHONDRION SMOOTH ER CENTRIOLES PLASMA MEMBRANE GOLGI BODY LYSOSOME

  21. PLASMA MEMBRANE ENDOPLASMIC RETICULUM (ER) LYSOSOME GOLGI BODY nuclear envelope nucleolus MITOCHONDRION NUCLEUS Fig. 3.6, p. 45

  22. Section 3 The Plasma Membrane: A Double Layer of Lipids

  23. The Plasma Membrane • The plasma membrane is a mix of lipids and proteins. • Bilayers of phospholipids, interspersed with glycolipids and cholesterol, are the structural foundation of cell membranes. • Within a bilayer, phospholipids show quite a bit of movement; they diffuse sideways, spin, and flex their tails to prevent close packing and promote fluidity, which also results from short-tailed lipids and unsaturated tails (kinks at double bonds).

  24. The Plasma Membrane • Proteins perform most of the functions of cell membranes. • The scattered islands of protein in the sea of lipids create a “mosaic” effect. • Membrane proteins (most are glycoproteins) serve as enzymes, transport proteins, receptor proteins, and recognition proteins.

  25. Animation: Structure of the Plasma Membrane CLICKTO PLAY

  26. Fig. 3.7, p. 46 EXTRACELLULAR FLUID receptor protein adhesion protein recognition protein cholesterol phospholipid LIPID BILAYER cytoskeletal proteins just beneath the plasma membrane CYTOPLASM transport proteins

  27. Video: Fluid Mosaic Model CLICKTO PLAY

  28. Section 4 How Do We See Cells?

  29. How Do We See Cells? • Microscopy allows us to see cells and their pieces. • Many types of microscopes exist, which can produce many types of pictures (micrographs): • Light microscopes use light to see samples; specimens usually must be thin and colored with dyes to be seen. Figure 3.8a

  30. Animation: How a Light Microscope Works CLICKTO PLAY

  31. How Do We See Cells? • Electron microscopes use beams of electrons rather than light to see details; transmission and scanning electron microscopy can magnify (enlarge) specimens far beyond the limits of the light microscope. Figure 3.8b-c

  32. Animation: How an Electron Microscope Works CLICKTO PLAY

  33. Section 5 The Nucleus

  34. The Nucleus • The nucleus encloses DNA, the building code for cellular proteins. • Its membrane isolates DNA from the sites (ribosomes in the cytoplasm) where proteins will be assembled. • The nuclear membrane helps regulate the exchange of signals between the nucleus and the cytoplasm.

  35. The Nucleus • A nuclear envelope encloses the nucleus. • The nuclear envelope consists of two lipid bilayers with pores. • The envelope membranes are continuous with the endoplasmic reticulum (ER).

  36. nuclear pore (protein complex that spans both lipid bilayers) one of two lipid bilayers (facing cytoplasm) NUCLEAR ENVELOPE one of two lipid bilayers (facing nucleoplasm) Fig. 3.10, p. 49

  37. Animation: Nuclear Envelope CLICKTO PLAY

  38. The Nucleus • The nucleolus is where cells make the units of ribosomes. • The nucleolus appears as a dense mass inside the nucleus. • In this region, subunits of ribosomes are prefabricated before ship­ment out of the nucleus.

  39. The Nucleus • DNA is organized in chromosomes. • Chromatin describes the cell’s collection of DNA plus the proteins associated with it. • Each chromosome is one DNA molecule and its associated proteins.

  40. The Nucleus • Events that begin in the nucleus continue to unfold in the cell cytoplasm. • Outside the nucleus, new polypeptide chains for proteins are assembled on ribosomes. • Some proteins are stockpiled; others enter the endomembrane system.

  41. Nucleus of an Animal Cell Figure 3.9

  42. Section 6 The Endomembrane System

  43. The Endomembrane System • ER is a protein and lipid assembly line. • The endoplasmic reticulum is a collection of interconnected tubes and flattened sacs, continuous with the nuclear membrane. • Rough ER consists of stacked, flattened sacs with many ribosomes attached; oligosaccharide groups are attached to polypeptides as they pass through on their way to other organelles, membranes, or to be secreted from the cell.

  44. The Endomembrane System • Smooth ER has no ribosomes; it is the area from which vesicles carrying proteins and lipids are budded; it also inactivates harmful chemicals and aids in muscle contraction. • Golgi bodies “finish, pack, and ship.” • In the Golgi body, proteins and lipids undergo final processing, sorting, and packag­ing. • The Golgi bodies resemble stacks of flattened sacs whose edges break away as vesicles.

  45. The Endomembrane System • A variety of vesicles move substances into and through cells. • Lysosomes are vesicles that bud from Golgi bodies; they carry powerful enzymes that can digest the contents of other vesicles, worn-out cell parts, or bacteria and foreign particles. • Peroxisomes are membrane-bound sacs of enzymes that break down fatty acids and amino acids.

  46. Animation: Nucleus and the Endomembrane System CLICKTO PLAY

  47. Fig. 3.11ab, p. 50 RNA messages from the nucleus vesicle cytoplasm ribosome vesicle inside nucleus rough ER nuclear envelope

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