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Cells

Cells. Questions & Answers. 1. What is the basic organizational structure of the human body? The cell 2. How many cells are in the human body? 50-100 trillion 3. What is cell differentiation? When cells specialize 4. What is the result of differentiation?

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Cells

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  1. Cells Questions & Answers

  2. 1. What is the basic organizational structure of the human body? The cell 2. How many cells are in the human body? 50-100 trillion 3. What is cell differentiation? When cells specialize 4. What is the result of differentiation? Cells vary in size and shape due to their unique function.

  3. 5. What are the 3 main parts of a cell? Cell membrane, nucleus and cytoplasm 6. The cytoplasm is composed of organelles suspended in a gel-like liquid called cytosol. 7. Cells vary considerably in size. In what units are they measured? Micrometers (µm) = 1/1,000 mm

  4. 8. Describe the structure of the cell membrane. a.Phospholipidbilayer b. Surfaces formed by the phosphate “heads”, which are hydrophilic. c. Fatty acid “tails” make up the interior of the membrane, which is hydrophobic.

  5. 9. What are the 3 main functions of the cell membrane? 1. Forms the outermost limit of the cell 2. Selective permeability – controls what enters and leaves the cell. 3. Signal transduction – allows cell to receive and respond to incoming messages

  6. 10. There are 5 main types of proteins found in the cell membrane. List the function of each: 1. Receptor proteins – receive and transmit messages 2.Integral proteins – form pores, channels and carriers; transduce signals 3. Enzymes – catalyze chemical reactions 4. CAMs – cellular adhesion molecules 5. Cell surface proteins – identify cells as self

  7. 11. Which type of molecules pass easily through the cell membrane, water-soluble or lipid-soluble? Lipid-soluble 12. What are some examples of lipid-soluble molecules? O₂, CO₂ and steroid hormones 13. What are some examples of water-soluble molecules to which the membrane is impermeable? Amino acids, proteins, sugars, nucleic acids and ions.

  8. 14. Organelle Ribosome – Free or bound to ER 15. Structure Tiny spheres made of rRNA and protein. 16. Function Protein synthesis

  9. 17. Organelle Endoplasmic reticulum – rough and smooth 18. Structure : Membrane-bound flattened sacs, canals and vesicles; RER studded with ribosomes; extension of the nuclear membrane 19. Function: RER – protein synthesis SER – makes lipids, breaks down drugs

  10. 20.Organelle Vesicles 21. Structure membranous sacs that vary in size and contents Formed by cell membrane in endocytosis, by Golgi apparatus and by ER 22. Function transport of substances

  11. 23. Organelle Golgi apparatus 24. Structure Stack of flattened, membranous sacs called cisternae 25. Function Modifies, packages and delivers proteins synthesized in the RER

  12. 26. Organelle Mitochondrion 27. Structure Membrane-enclosed sac containing a highly folded inner membrane, forming cristae. 28. Function Converts energy in glucose and other nutrients into ATP.

  13. 29. Organelle Lysosomes 30. Structure Vary greatly, often tiny sacs. Contain digestive enzymes. 31. Function “Garbage disposal” – enzymes digest debris and foreign particles, such as bacteria

  14. 32. Organelle Peroxisomes 33. Structure Membranous sacs that resemble lysosomes 34. Functions a. Enzyme peroxidase– catalyzes reactions that produce H₂O₂ (hydrogen peroxide) – toxic to cell b. Enzyme catalase– breaks down H₂O₂ c. Over 40 other enzymes

  15. 35. Cell part Cilia 36. Structure Hairlike motile extensions on surface of cells 37. Function Propel fluids across the cell’s surface (ie. mucus)

  16. 38. Cell part Flagellum 39. Structure Long tail-like projection 40. Function Motility (ie. sperm)

  17. 41. Cell part Cytoskeleton 42. Structure Microfilaments and microtubules (thin rods and tubes) 43. Function Support cytoplasm, help move organelles and substances within the cytoplasm

  18. 44. Cell part Nuclear envelope 45. Structure Porous double-membrane that separtates the nuclear contents form the cytoplasm 46. Function Maintains integrity of nucleus, controls passage of materials between nucleus and cytoplasm

  19. 47. Organelle Nucleolus 48. Structure Nonmembranous body of protein and RNA 49. Function Makes ribosomes

  20. 50. Cell part Chromatin 51. Structure Loosely coiled double-stranded fibers of DNA and protein 52. Function Codes for protein

  21. 53. There are 2 types of transport across the cell membrane – passive and active. Which type requires no energy? Passive 54. Why? It is a physical process in which particles move with (or down) the concentration gradient 55. Examples Diffusion, osmosis, facilitated diffusion, and filtration

  22. 56. Why does active transport require energy? Because it is a physiological process in which particles are moved against (or up) the concentration gradient by the cell membrane 57. Examples Transport proteins, endocytosis, exocytosis and transcytosis

  23. 58. What is facilitated diffusion? Diffusion across the membrane with the help of a channel or carrier protein 59. What is osmosis? Diffusion of water through a selectively permeable membrane 60. Does water move toward a higher or lower concentration of solutes? Higher

  24. 61. What is filtration? When smaller molecules are forced through porous walls of capillaries, but larger molecules remain in the blood. 62. What is the driving force for filtration? Blood pressure 63. Why is filtration considered a passive process? Because it can occur due to the pressure caused by gravity alone.

  25. 64. Endocytosis is a form of active transport. What are the three types? 1. Pinocytosis – substance is liquid 2. Phagocytosis – substance is solid 3. Receptor-mediated endocytosis – requires the substance to bind to a membrane receptor

  26. 65. Exocytosis is also active transport. Describe how it works: Vesicle formed in the cell, then fuses with cell membrane and releases contents outside the cell. 66. What are some examples of exocytosis? Waste removal; release of neurotransmitters from nerve cells

  27. 67. What is transcytosis? Endocytosis followed by exocytosis 68. Function? Transport a substance rapidly through a cell 69. Example? HIV virus crossing a cell

  28. 70. What is the cell cycle? Series of changes a cell undergoes from the time it is formed until the time it divides. 71. What are the three stages of the cell cycle? Interphase, mitosis and cytokinesis

  29. 72. What occurs during Interphase? Cell is very active – grows and maintains routine functions 73. What are the 3 phases of Interphase? G₁, S and G₂. 74. What occurs during each phase? G₁ and G₂ - Cell grows and makes organelles S phase – replicates DNA in preparation for mitosis.

  30. 75. What occurs during mitosis? Karyokinesis = nucleus divides Cytokinesis = cytoplasm divides 76. List the 4 phases of nuclear division in order: Prophase , metaphase, anaphase and telophase 77. How does cytokinesis occur in animal cells? Contractile ring pinches cytoplasm in half

  31. 78. One reason cells must divide is to maintain a (high or low) surface area to volume ratio? High 79. Cell division rate varies greatly among cell types.Between skin, blood and neuron cells, which type(s) divide often? Skin and blood 80. What stimulates cell division? Growth factors and hormones 81. Cell division is suppressed by contact inhibition. 82. The consequence of a loss of cell cycle control are tumors.

  32. 83. What are the 2 types of tumors? Benign = usually remains localized Malignant = can metastasize (spread); cancerous 84. Two types of genes can cause cancer. What are they? a. Oncogenes– activate other genes that increase cell division b. Tumor suppressor genes – normally regulate mitosis, but become inactivated

  33. 85. What is a stem cell? Undifferentiated cell that can make 2 new stem cells (self-renewal) or a new stem cell and a partially differentiated progenitorcell. 86. A cell that can give rise to any type of cell is called totipotent. A cell that can give rise to many, but not all, cell types is called pluripotent. Which cell is totipotent, and which is pluripotent? Stem cell =totipotent Progenitor cell = pluripotent

  34. 87. All cells in the human body, with the exception of red blood cells, which expel their nucleus, have a complete set of chromosomes. How do cells specialize and develop their distinct characteristics? By expressing different sets of genes. 88. The term blastis used to describe an immature differentiated cell, such as an osteoblast (immature bone cell) and myoblast, (immature muscle cell.)

  35. 89. What is apoptosis? Programmed cell death 90. It is a fast, orderly multi-step process: Cell surface “death receptor” receives a message to die. Enzymes called caspases are activated inside the cell, where they cut up various cell components that are then encapsulated by pieces of cell membrane. The cell is gone within a(n) hour. 91. Why must mitosis and apoptosis by synchronized? So that tissues and organs neither overgrow nor shrink.

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