· Web viewHypertonic—cells lose water and undergo plasmolysis (shrinkage of cell content which causes the cell membrane to pull away from the cell wall) c. Hypotonic—cells gain

Topic 2 review Name __________________________________1. What is the major difference between prokaryotic and eukaryotic cells?

Prokaryotic Cells (pro-before; karyon-kernel)• More primitive and smaller than eukaryotic cells• No nuclear membrane or membrane-bound organelles (no true nucleus)• Have cell wall in addition to a plasma membrane and ribosomes• Genetic material in nucleoid region• Members of domains Archaea and Bacteria

Eukaryotic Cells (eu-true)• “true cells” with a nuclear membrane and membrane-bound organelles• Genetic material within nucleus• Have a “true nucleus”• Domain Eukarya• Kingdoms Plantae, Fungi, Animalia, and Protista

2. Why can prokaryotic have ribosomes but not other organelles?Ribosomes are component. Organelles—refer to membranous sacs, envelopes, and other compartmented portions of the cytoplasm

3. List three similarities between pro and eu.Cellular membrane, have genetic material, cytosol

4. List three differences between pro and eu.Nucleoid, cell wall in addition to plasma membrane, ribosomes

5. How are pro and eu classified in the domain system? i. Prokaryotic cells - Members of domains Archaea and Bacteria

ii. Eukaryotic cells - eukarya

6. How are pro and eu classified in the kingdom system?i. Prokaryotic – eubacteria, archaebacteria

ii. Kingdoms Plantae, Fungi, Animalia, and Protista

7. What is the difference between pro and eu in where the DNA is found?Prokaryotic – nucleoidEukaryotic – nucleus, mitochondria, and chloroplast

8. What do you know about the structure of the plasma membrane? The general structure of a biological membrane is a double layer of phospholipids with proteins interspersed. The main components are proteins and lipids along with carbohydrates. Primary lipid is phospholipid, but also some glycolipids and cholesterol (helps membrane to remain fluid when cell temperature drops). Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids. Membranes must be fluid to work properly

9. What do you know about the function of the plasma membrane?The plasma membrane is a selectively permeable barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell. The plasma membrane is the boundary that surrounds and separates the living cell from its surroundings

10. What are the two common eukaryotic cells?Plant and Animal Cell

11. How are plant and animal cells different from one another? Name at least 3 differences.Plants – Large central vacuole and tonoplast, chloroplast, cell wall, plasmodesmata

Animals – lysosomes, only a plasma membrane, centrioles, flagella

List the function of the following cell organelles: 12. CytoskeletonThe cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organellesIt is composed of three types of molecular structures:

Microtubules Microfilaments Intermediate filaments

Helps to support the cell and maintain its shapePlays a major role in organizing the structures and activities of the cell Described by Keith PorterInteracts with motor proteins to produce motility

Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton

13. Chloroplast - found in plants and algae, are the sites of photosynthesis, Are not part of the endomembrane system, Have a double membrane, Have proteins made by free ribosomes, Contain their own DNA. Chloroplasts (chloro-green)—Contain green pigment chlorophyll as well as enzymes and other molecules that function in photosynthesisFound in leaves and other green organs of plants and in algae

Structure includes:Thylakoids—membranous sacs, stacked to form a granumStroma—the internal fluid contains DNA, ribosomes and enzymes

14. RibosomesComposed of ribosomal RNA and proteinFunction in protein synthesisConstructed in nucleolus in eukaryotic cellsCells with high rates of protein synthesis have prominent nucleoli and many ribosomesNo organized membraneEukaryotic ribosomes are made of 2 subunits composed of:

a. rRNA produced in nucleolusb. Proteins from cytoplasm

Prokaryotic ribosomes are smaller than eukaryotic and differ in compositionCarry out protein synthesis in two locations:

a. Free ribosomes• suspended in cytosol• produce proteins used in cytosol

b. Bound ribosomes• attached to the outside of the endoplasmic reticulum or nuclear envelope• produce proteins for membrane inclusion or to be exported from the cell

Bound and free ribosomes are interchangeable—depends on type of protein being produced

15. Golgi bodyConsists of flattened membranous sacs called cisternaeDescribed in 1898 by Camillo GolgiF(x):

Modifies products of the ER Manufactures certain macromolecules (pectin and other noncellulose polysaccharides) Sorts and packages materials into transport vesicles

Have two poles that differ in thickness and composition:a. Cis face

Located near the ER Receives material by fusing with transport vesicles from the ER

b. Trans face Pinches off vesicles from Golgi and transports molecules to other sites or to plasma membrane

for export

16. Nucleus (including structures such as chromatin)- Spherical or oval- Usually only one per cell except human red blood cells which are anucleate and skeletal muscle cells that are multinucleate- Contains nucleoplasm - DNA and proteins form the genetic material called chromatin - Chromatin condenses to form discrete chromosomes- The nuclear envelope which is a double membrane structure which encloses the nucleus separating it from the cytoplasm- Pores which are lined by a protein structure called a pore complex regulate the movement of certain large macromolecules and particles.- The nuclear side of the nuclear envelope is lined by the nuclear lamina, a network of protein filaments that maintain the shape of the nucleus- Evidence indicates the presence of nuclear matrix which is a framework of fibers extending throughout the nuclear interior

17. Nucleolus- The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis

18. ER (distinguish b/t smooth and rough)Accounts for more than half of the total membrane in many eukaryotic cellsContinuous with plasma membrane and nuclear membraneIncludes membranous tubules and internal, fluid-filled sacs called cisternaeNamed in 1953 by Keith PorterManufactures membranes and performs many biosynthetic functionsTwo regions:

a. Smooth ER • Lacks ribosomes• Rich in enzymes• F(x):

-synthesizes lipids, phospholipids, and steroids -metabolizes carbohydrate -detoxifies drugs and poisons -stores calcium

b. Rough ER• Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates)• Transport vesicles that contain proteins surrounded by membranes, bud from a specialized region called

the transitional ER• Transport vesicles carry proteins from one part of the cell to another• Is a membrane factory for the cell

• Synthesis of proteins destined for secretion -(Ex: insulin, antibodies)

19. CentrosomesThe centrosome is a “microtubule-organizing center”. In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring

20. Microvilli – finger-like projections on each epithelia cell’s apical surface which are exposed to the intestinal lumen. Give a brush- like appearance. Greatly increases the surface area and therefore nutrient absorption

21. Peroxisome - oxidative organelles. Specialized metabolic compartments bound by a single membrane. Contain enzymes that transfer hydrogen from various substrates to oxygen. Produce hydrogen peroxide and convert it to water

F(x):Breakdown fatty acids into smaller molecules to be used in cellular respirationDetoxification of alcohol and other harmful compounds in the liverSpecialized peroxisomes (glyoxysomes) convert fatty acids in seed to sugars for a source of energy for the seedling

22. MitochondriaMitochondria are the sites of cellular respiration, a metabolic process that generates ATP, Are not part of the endomembrane system, Have a double membrane, Have proteins made by free ribosomes, Contain their own DNAFound in nearly all eukaryotic cellsNumber in a cell depends on cell’s metabolic activityStructure:

Enclosed by two membranesjSmooth outer membrane

kInner membrane folded into cristae which increase surface area for enzymes that synthesize ATPThe inner membrane creates two compartments: intermembrane space and mitochondrial matrix

Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix which contains DNA, ribosomes, and enzymes

23. LysosomeMembrane-bound sac of hydrolytic enzymes that digest macromoleculesEnzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids and work best at acidic pHHydrolytic enzymes and lysosomal membranes are synthesized in rough ER and modified in the Golgi apparatusF(x):

a. Intracellular digestion—phagocytosisb. Recycle cell’s macromolecules and or damaged organelles—autophagyc. Programmed cell destructiond. Separate potentially dangerous enzymes from cytosole. Maintain optimum pH for enzyme activity

24. Cell wallPresence of a cell wall distinguishes plant cells from animal cellsFound in prokaryotes, fungi, and some protistsThicker than plasma membraneNonlivingComposed of cellulose microfibrils embedded in other polysaccharides and proteinChemical composition of cell wall differs with species and among cell types within a plantExternal to plasma membraneF(x): -Protection -Maintain shape

-Prevent excess water uptake

25. Central vacuoleLarge vacuole in mature plant cells which contains “cell sap”Enclosed by a membrane—tonoplast—which is part of the endomembrane system and is selectively permeableF(x): -stockpiling proteins or inorganic ions

-disposing of metabolic by-products-storing defensive compounds that protect the plant against herbivores-holding pigments -involved in cell elongation-increases the ratio of membrane surface area to volume

26. What is the function of plasmodesmata?i. Channels that perforate plant cell walls allowing cytosol to pass between adjacent cells

ii. Allows free passage of water and small solutesiii. Lined by plasma membrane

27. What is the function of microvilli?Greatly increases the surface area and therefore nutrient absorption

28. What are nuclear pores? What function do they serve?i. Pores which are lined by a protein structure called a pore complex regulate the movement of

certain large macromolecules and particles.

29. Describe the endosymbiont theory.Theory proposed by Lynn Margulis:

• mitochondria are the result of endocytosis of aerobic bacteria• chloroplasts are the result of endocytosis of photosynthetic bacteria• in both cases by large anaerobic bacteria who would not otherwise be able to exist in an aerobic environment.• this arrangement became a mutually beneficial relationship for both cells (symbiotic).Margulis' original hypothesis proposed that aerobic bacteria (that require oxygen) were ingested by anaerobic bacteria (poisoned by oxygen), and may each have had a survival advantage as long as they continued their partnership.

30. What pieces of evidence support this theory?

Prokaryotes Eukaryotes Mitochondria ofEukaryotic cells

Chloroplasts of Photosynthetic eukaryotes

DNA 1 single, circular chromosome

Multiple linear chromosomescompartmentalized in a nucleus

1 single, circularchromosome

1 single, circular chromosome

Replication

Binary Fission(1 cell splits into 2)

Mitosis Binary Fission(1 cell splits into 2)

Binary Fission(1 cell splits into 2)

Ribosomes "70 S" "80 S" "70 S" "70 S"

Electron Transport Chain

Found in the plasma membrane around cell

Not found in the plasma membranearound cell (found only in the cell's mitochondria and chloroplasts)

Found in the plasma membrane around mitochondrion

Found in the plasma membrane around chloroplast

Size (approximate)

~1-10 microns ~50 - 500 microns ~1-10 microns ~1-10 microns

31. How does the structure of the mitochondria contribute to its function?

Enclosed by two membranesjSmooth outer membrane

kInner membrane folded into cristae which increase surface area for enzymes that synthesize ATPThe inner membrane creates two compartments: intermembrane space and mitochondrial matrix

Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix which contains DNA, ribosomes, and enzymes

32. List different types of vacuoles and their functions.Vacuole types and F(x):

a. Food Vacuole Formed by phagocytosis F(x): intracellular digestion

b. Contractile Vacuole F(x): eliminates excess water from fresh water protists

c. Central Vacuole

Large vacuole in mature plant cells which contains “cell sap” Enclosed by a membrane—tonoplast—which is part of the endomembrane system and is

selectively permeable F(x): -stockpiling proteins or inorganic ions

-disposing of metabolic by-products-storing defensive compounds that protect the plant against herbivores-holding pigments -involved in cell elongation-increases the ratio of membrane surface area to volume

33. What is the difference between bound and free ribosomes?Free ribosomes

• suspended in cytosol• produce proteins used in cytosol

Bound ribosomes• attached to the outside of the endoplasmic reticulum or nuclear envelope• produce proteins for membrane inclusion or to be exported from the cell

Bound and free ribosomes are interchangeable—depends on type of protein being produced

34. What is the endomembrane system? These components are either continuous or connected via transfer by vesicles

35. Know what organelles belong to it.Components of the endomembrane system:

a. Nuclear envelopeb. Endoplasmic reticulumc. Golgi apparatusd. Lysosomese. Vacuolesf. Plasma membrane

36. What are the three components of the cytoskeleton?a. Microtubulesb. Microfilamentsc. Intermediate filaments

37. Distinguish between cilia and flagella.

Microtubules control the beating of cilia and flagella, locomotor appendages of some cells

38. What is the ECM? What is its purpose?Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM)The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectinECM proteins bind to receptor proteins in the plasma membrane called integrinsF(x):

Support Adhesion Movement Regulation

39. List and describe the three types of intercellular junctions. a. At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluidb. Desmosomes (anchoring junctions) fasten cells together into strong sheetsc. Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells

40. Intercellular junctions in animal cells are analogous to __plasmodesmata_______________ in plant cells.

41. What structures do animal cells have that plant cells don't? centrioles, lysosomes

42. Explain the fluid mosaic model.The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in itProposed by S. J. Singer and G. L. Nicolson in 1972

2. Proposed the fluid mosaic model which accounted of the amphipathic character of proteins3. Proposed that proteins are individually embedded, rather than forming a coat on the surface

4. Hydrophilic portions of proteins and phospholipids are exposed to water resulting in a stable membrane structure

5. Hydrophobic portions of proteins and phospholipids are in the non-aqueous environment inside the bilayer 6. Membrane is a mosaic of proteins bobbing in a fluid bilayer of phospholipids

43. Distinguish between integral and peripheral proteins.Integral proteins penetrate the hydrophobic core

• Those that span the membrane are called transmembrane proteins• The hydrophobic regions of an integral protein consist of one or more stretches of nonpolar amino acids, often

coiled into alpha helicesPeripheral proteins are bound to the surface of the membrane

44. What role do carbohydrates play in the membrane?Cells recognize each other by binding to surface molecules, often carbohydrates, on the plasma membraneMembrane carbohydrates may be covalently bonded to lipids (forming glycolipids) or more commonly to proteins (forming glycoproteins)Carbohydrates on the external side of the plasma membrane vary among species, individuals, and even cell types in an individual

45. Are nonpolar substances hydrophobic or hydrophilic? - Nonpolar (hydrophobic) Molecules:Dissolve in the membrane and cross it with ease (hydrocarbons, oxygen, carbon dioxide)

46. Which type of substance can easily cross the membrane? – hydrophobic, small, non-charged

47. If it can’t easily cross on its own, how can it get across?Movement of ions and polar molecules are slowed by the hydrophobic core of the membrane. Transport proteins (aquaporins and channel proteins and carrier proteins)

48. What is the movement of water across membranes called? How does it easily pass through? Osmosis - aquaporins

49. Explain the difference in active and passive transport.Does not require energy – passiveRequires energy - active

50. Define concentration gradient in your own words.Substances diffuse down their concentration gradient, the difference in concentration of a substance from one area to another

51. Explain the difference in hypotonic, hypertonic, and isotonic solution. (Be able to work these problems)Isotonic solution: Solute concentration is the same as that inside the cell; no net water movement across the plasma membraneHypertonic solution: Solute concentration is greater than that inside the cell; cell loses waterHypotonic solution: Solute concentration is less than that inside the cell; cell gains waterCells without walls:

a. Isotonic—no changeb. Hypertonic—cell loses water and undergoes crenation (shrinks)c. Hypotonic—cell gains water and may undergo lysis (burst)

52. Explain the difference between turgid, plasmolyzed and flaccid. What type of solution would these be found in?Effects of Osmosis on Cells with Walls:

a. Isotonic—plant cells become flaccid or limpb. Hypertonic—cells lose water and undergo plasmolysis (shrinkage of cell content which causes the cell

membrane to pull away from the cell wall)c. Hypotonic—cells gain water and builds up turgor pressure (firmness due to water content)

53. Explain why the cell would need to use facilitated diffusion. Defined as the diffusion of solutes across a membrane with the help of transport proteins (channel and carrier proteins)Helps the diffusion of many polar molecules and ions that are impeded by the membrane’s phospholipid bilayerSome gated channels open in response to a stimulus (Ex: ion channels)

54. List examples of passive transport.Aquaporins, channel proteins, diffusion, osmosis, carrier proteins

55. List examples of active transport.Defined as energy-requiring process during which a carrier protein pumps a molecule across a membrane, against its concentration gradient (from low to high)Enables a cell to maintain internal concentrations of small molecules that differ from concentrations in its

environmentRequires specific proteins embedded in the membranesEnergy from ATPTypes: sodium-potassium pump, ion pumps, cotransport

56. Explain how the sodium potassium pump contributes to membrane potential.Helps keep Na+ conc. high outside cell and K+ conc. high inside the cellATP provide energy for the transport protein which causes a change in shape of transport proteinTransports 3 Na+ out and 2 K+ in

57. Explain cotransport.occurs when active transport of a solute indirectly drives transport of another solute Plants commonly use the gradient of hydrogen ions generated by proton pumps to drive active transport of nutrients into the cell

58. Answer the review questions on p. 57.

59. Differentiate between endocytosis and exocytosis.Both are energy- usingIn endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membraneEndocytosis is a reversal of exocytosis, involving different proteinsThere are three types of endocytosis:

a. Phagocytosis (“cellular eating”)b. Pinocytosis (“cellular drinking”)c. Receptor-mediated endocytosis

Exocytosis• Transport vesicles migrate to the membrane, fuse with it, and release their contents• Many secretory cells use exocytosis to export their products

60. Differentiate between pinocytosis and phagocytosis.In phagocytosis a cell engulfs a particle in a vacuole and the vacuole fuses with a lysosome to digest the particle. In pinocytosis, molecules are taken up when extracellular fluid is “gulped” into tiny vesicles. In receptor-mediated endocytosis, binding of ligands (any molecule that binds specifically to a receptor site of another molecule)to receptors triggers vesicle formation. It enables cells to acquire bulk quantities of specific substances, even if they are in low conc. in extracelluar fluid

61. What is metabolism?Totality of an organism’s chemical reactions

62. Distinguish between catabolic and anabolic pathways.Catabolic Pathway

• Release energy by breaking down complex molecules into simpler molecules (downhill)• Ex: Cellular respiration which breaks glucose down into CO2 and H2O and provides energy for

the cell.Anabolic (Biosynthetic) Pathway

• Consume energy to build complex molecules from simpler ones (uphill)• Ex: Photosynthesis

Protein Synthesis

63. What is the difference between potential and kinetic energy.Kinetic energy is energy associated with motionPotential energy is energy that matter possesses because of its location or structure

64. Which law states that energy cannot be created nor destroyed?First Law: Principle of Conservation of Energy

65. Distinguish between endergonic and exergonic reactions. An exergonic reaction proceeds with a net release of free energy and is spontaneousAn endergonic reaction absorbs free energy from its surroundings and is nonspontaneous

66. What is the structure of ATP? ATP—adenosine triphosphate; cell’s energy shuttle

Nucleoside triphosphateConsists of:

• adenine—nitrogenous base• ribose—5 carbon sugar• chain of 3 phosphate groups

67. Use ATP and ADP to explain energy coupling.To do work, cells manage energy resources by energy coupling, the use of an exergonic process to drive an endergonic oneMost energy coupling in cells is mediated by ATP which is the immediate source of energy that drives cellular work

• Bonds between phosphates (~) are unstable and easily broken by hydrolysis to form ADP (adenosine diphosphate) + Pi (inorganic phosphate) and release energy which comes from the chemical change to a state of lower free energy and not the phosphate bonds themselves

• ATP + H2O ADP + Pi + energy (DG = -7.3 kcal/mol)• Exergonic reaction• Exergonic hydrolysis of ATP is coupled with endergonic process by transferring a phosphate to another molecule• Process called phosphorylation• Enzyme controlled• Molecule acquiring phosphate is more reactive

68. What do enzymes do to activation energy? – lowers.

69. Explain the relationship between enzyme and substrate.The reactant that an enzyme acts on is called the enzyme’s substrate

• Ex: sucrose sucrase glucose + fructoseThe enzyme binds to its substrate, forming an enzyme-substrate complexSpecificity is based on shape of enzymeThe active site is the region on the enzyme where the substrate bindsInduced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze the reactionIn an enzymatic reaction, the substrate binds to the active site of the enzymeThe active site can lower an EA barrier by

a. Act as a template for substrate orientation b. Stressing the substrates and stabilizing the transition statec. Providing a favorable microenvironmentd. Participating directly in the catalytic reaction

Initial substrate concentration partly determines the rate of an enzyme controlled reactionThe higher the substrate concentration, the faster the reaction up to a limit

70. What is an active site?The active site is the region on the enzyme where the substrate binds

71. How can an enzyme be denatured?Environmental Conditions

• Each enzyme has optimal environmental conditions that favor the most active enzyme conformationTemperature

-increase temperature and rate of reaction speeds up to about 60° C when protein is denatured-optimal temperature for human enzymes—35-40°C

pH-optimal pH range for most enzymes—6-8

-pepsin works best at pH of 2Disrupts the hydrogen, covalent, ionic, and van der waal interactions

72. What is a cofactor? - Nonprotein molecules that are required for proper enzyme reaction

73. Distinguish between competitive and noncompetitive inhibitors.

Competitive inhibitor-resembles an enzyme’s normal substrate and competes with it for an active site-blocks active site-if reversible, effects can be overcome by increased substrate concentration

Noncompetitive inhibitors-do not enter the enzyme’s active site, but bind to another part of enzyme molecule-alters enzyme shape

74. What is an allosteric site?Allosteric site—specific receptor site on some part of the enzyme molecule other than the active siteAllosteric enzymes have 2 conformations—one active and the other inactive. Binding of an activator to the allosteric site stabilizes the active conformation. Binding of an inhibitor to the allosteric site stabilizes the inactive conformation

75. Describe feedback inhibition.The end product of a metabolic pathway shuts down the pathwayFeedback inhibition prevents the cell from wasting chemical resources by synthesizing more product than necessary

76. What are the three stages of signaling?Reception- the target cell’s detection of a chemical signaling molecule. (when the molecule binds to the receptor protein).

Transduction- the change that occurs on the protein due to the receptor binding. Response- transduced signal triggers a specific cellular response.

77. Where can receptors be found? – cellular membrane

78. Explain briefly how a G coupled receptor and receptor tyrosine kinases work.

• G Protein Coupled Receptors (GPCRs) - signaling molecule binds to GPCR which activates it and changes its shape. GPCR then binds an inactive G protein causing causing GTP to displace the GDP, activating the G protein. Protein binds to enzyme, activating it- triggering the next step in a cellular response.

• Receptor tyrosine kinases (RTKs) are membrane receptors that attach phosphates to tyrosines (transfer phosphates from ATP to the amino acid tyrosine)

• A receptor tyrosine kinase can trigger multiple signal transduction pathways at once

79. What are second messengers?Second messengers are small, nonprotein, water-soluble molecules or ions involved in signaling pathways that spread throughout a cell by diffusionSecond messengers participate in pathways initiated by G protein-coupled receptors and receptor tyrosine kinases

80. What is apoptosis? How does it function in us?Apoptosis is programmed or controlled cell suicideA cell is chopped and packaged into vesicles that are digested by scavenger cellsCell shrinks and become lobed (called “blebbing”)Apoptosis prevents enzymes from leaking out of a dying cell and damaging neighboring cells Apoptosis evolved early in animal evolution and is essential for the development and maintenance of all animalsApoptosis may be involved in some diseases (for example, Parkinson’s and Alzheimer’s); interference with apoptosis may contribute to some cancers

81. List the 5 stages of the cell cycle and what happens in each stage.The cell cycle consists of:

d. Mitotic (M) phase (mitosis and cytokinesis)e. Interphase (cell growth and copying of chromosomes in preparation for cell division)

i. G1 Phase (first gap)—cell grows; first growth phase when the centrioles replicateii. S Phase (synthesis)--DNA replicates

iii. G2 Phase (second gap)—cell grows; second growth phase during which the cell is preparing for mitosis by producing proteins, ATP, etc.

82. Distinguish between gametes and somatic cells.

Somatic cells (nonreproductive cells) have two sets of chromosomes; produced by mitosis; genetically identicalGametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells; produced by meiosis; genetically unique

83. What are 3 differences in mitosis and meiosis?

Stage Meiosis I Mitosis

Prophase • Synapsis occurs to form tetrads

• Chiasmata appear as

• Neither synapsis nor crossing over occurs

evidence that crossing over has occurred

Metaphase

• Homologous pairs (tetrads) align on the metaphase plate

• Individual doubled chromosomes align on metaphase plate

Stage Meiosis Mitosis

Anaphase

• Pairs of chromosomes separate

• Centromeres do not divide and sister chromatids stay together

• Sister chromatids of each chromosome move to the same pole of the cell

• Sister chromatids of individual doubled chromosomes separate

• Centromers divide• Sister chromatids move to opposite poles of the cell

Meiosis II is basically identical to Mitosis

84. What is the difference in diploid and haploid?Diploid – full set of chromosomesHaploid – half set of chromosomes

85. What three stages make up interphase? How much time does a cell spend here? – 90%f. Interphase (cell growth and copying of chromosomes in preparation for cell division)

i. G1 Phase (first gap)—cell grows; first growth phase when the centrioles replicate

ii. S Phase (synthesis)--DNA replicatesiii. G2 Phase (second gap)—cell grows; second growth phase during which the cell is preparing for

mitosis by producing proteins, ATP, etc.

86. What is the relationship between sister chromatids and a centromere?

87. What are the 5 phases of mitosis? What happens in each phase?a. Mitosis – cellular Division

i. Prophase - Changes in nucleus:a. Nucleoli disappearb. Chromatin fibers become tightly coiled and folded to form observable

chromosomesChanges in cytoplasm

c. Mitotic spindle forms--Composed of microtubules and associated proteins which are arranged between the two centrosomes (microtubule-organizing center)d. Centrosomes move apart

--Apparently they are propelled along the surface of the nucleus by lengthening of microtubule bundles between them

ii. Prometaphase - . 2. Nuclear envelope fragments3. Microtubules interact with chromosomes4. Spindle fibers (bundles of microtubules) extend from each pole toward the equator

(midpoint between the poles) (aka metaphase plate) of the cell5. Each chromatid has a kinetochore (specialized structure located at the centromere

region)

6. Bundles of microtubules (kinetochore microtubules) attach to kinetochores and put chromosomes into agitated motion

7. Microtubules (nonkinetochore microtubules) radiated from each centrosome toward the metaphase plate (equator) without attaching to chromosome

iii. Metaphase8. Centrosomes positioned at poles (opposite ends ) of the cell9. Chromosomes move to metaphase plate (plane equidistant between the spindle poles)10. Centromeres of all chromosomes aligned on metaphase plate11. Kinetochore fibers of sister chromatids face opposite poles so identical chromatids are

attached to kinetochore fibers radiating from opposite ends of the parent cell12. Entire structure formed by nonkinetochore microtubules plus kinetochore microtubules

called the spindleiv. Anaphase

13. Begins when paired centromeres of each chromosome move apart14. Sister chromatids separate and are considered chromosomes15. Spindle apparatus starts moving the separate chromosomes toward opposite poles16. Chromosomes move in a V-shape because of attachment of kinetochore fibers to

centromere17. Kinetochore microtubules shorten at end attached to kinetochores18. Poles of cell move farther apart slightly elongating the cell19. At end of phase two poles have complete and equivalent collections of chromosomes

v. Telophase20. Nonkinetochore microtubules further elongate the cell21. Daughter nuclei begin to form at the two poles22. Nuclear envelop reforms from fragments of parent cell nuclear envelope and other

portions of endomembrane system23. Nucleoli reappear24. Chromosomes uncoil and appear as chromatin25. cytokinesis begins

88. Distinguish between cytokinesis in plant cell and animal cells.a. Cytokinesis –

i. Process of cytoplasmic division that follows mitosisii. Begins in telophase

iii. Differs in plant and animal cellsiv. Animal Cells

1. Occurs as cleavage2. Cleavage furrow forms as a shallow groove on cell surface near metaphase plate

(in animal cells only)3. Contractile ring of actin and myosin microfilaments forms on cytoplasmic side of furrow4. Microfilaments contract until parent cell is pinched in two

v. Plant Cells1. Cell plate forms across midline of parent cell (equator)2. Cell plate forms from fusing vesicles derived from Golgi apparatus that have moved

along microtubules to cell’s center3. Cell plate enlarges until its surrounding membrane fuses with the existing plasma

membrane4. New cell wall forms between two membranes from contents of cell plate

89. What are the 3 checkpoints? Which is most important?

For many cells, the G1 checkpoint seems to be the most important one (“restriction point”) If a cell receives a go-ahead signal at the G1 checkpoint, it will usually complete the S, G2, and M phases and

divide If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the

G0 phase

90. What is the G0 phase?nondividing state called the G0 phase

-Ex: a. muscle and nerve cells until deathb. liver cells until recruited back to cell cycle by such cues as growth factors

91. What are the key characteristics of normal cell division?Density – dependent inhibition - which crowded cells stop dividingAnchorage dependency- in which they must be attached to a substratum in order to divide

92. What is transformation?A normal cell is converted to a cancerous cell by a process called transformation1. Cancer cells do not respond normally to the body’s control mechanisms2. Cancer cells may not need growth factors to grow and divide:

They may make their own growth factor They may convey a growth factor’s signal without the presence of the growth factor They may have an abnormal cell cycle control system

93. Distinguish between a malignant and benign tumor.If abnormal cells remain at the original site, the lump is called a benign tumorMalignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body, where they may form secondary tumors

94. What is metastasis? Spread of cancer cells