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 – nucleoid
Eukaryotic – 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. Cytoskeleton
The cytoskeleton is a network of fibers extending throughout the cytoplasm
It organizes the cell’s structures and activities, anchoring many organelles
It is composed of three types of molecular structures:
 Microtubules
 Microfilaments
 Intermediate filaments
Helps to support the cell and maintain its shape
Plays a major role in organizing the structures and activities
of the cell
Described by Keith Porter
Interacts 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
photosynthesis
Found in leaves and other green organs of plants and in algae
Structure includes:
Thylakoids—membranous sacs, stacked to form a granum
Stroma—the internal fluid contains DNA, ribosomes and enzymes
14. Ribosomes
Composed of ribosomal RNA and protein
Function in protein synthesis
Constructed in nucleolus in eukaryotic cells
Cells with high rates of protein synthesis have prominent nucleoli and many ribosomes
No organized membrane
Eukaryotic ribosomes are made of 2 subunits composed of:
a. rRNA produced in nucleolus
b. Proteins from cytoplasm
Prokaryotic ribosomes are smaller than eukaryotic and differ in composition
Carry 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 body
Consists of flattened membranous sacs called cisternae
Described in 1898 by Camillo Golgi
F(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 cells
Continuous with plasma membrane and nuclear membrane
Includes membranous tubules and internal, fluid-filled sacs called cisternae
Named in 1953 by Keith Porter
Manufactures membranes and performs many biosynthetic functions
Two 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. Centrosomes
The 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 respiration
Detoxification of alcohol and other harmful compounds in the liver
Specialized peroxisomes (glyoxysomes) convert fatty acids in seed to sugars for a source of energy for the
seedling
22. Mitochondria
Mitochondria 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 DNA
Found in nearly all eukaryotic cells
Number in a cell depends on cell’s metabolic activity
Structure:
Enclosed by two membranes
Smooth outer membrane
Inner membrane folded into cristae which increase surface area for enzymes that synthesize ATP
The 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. Lysosome
Membrane-bound sac of hydrolytic enzymes that digest macromolecules
Enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids and work best at acidic pH
Hydrolytic enzymes and lysosomal membranes are synthesized in rough ER and modified in the Golgi apparatus
F(x):
a. Intracellular digestion—phagocytosis
b. Recycle cell’s macromolecules and or damaged organelles—autophagy
c. Programmed cell destruction
d. Separate potentially dangerous enzymes from cytosol
e. Maintain optimum pH for enzyme activity
24. Cell wall
Presence of a cell wall distinguishes plant cells from animal cells
Found in prokaryotes, fungi, and some protists
Thicker than plasma membrane
Nonliving
Composed of cellulose microfibrils embedded in other polysaccharides and protein
Chemical composition of cell wall differs with species and among cell types within a plant
External to plasma membrane
F(x): -Protection
-Maintain shape
-Prevent excess water uptake
25. 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
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 solutes
iii. 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?
DNA
Replica
tion
Riboso
mes
Electro
n
Transp
ort
Chain
Size
(approx
imate)
Prokaryotes
Eukaryotes
Mitochondria of
Eukaryotic cells
Chloroplasts of
Photosynthetic
eukaryotes
1 single,
circular
chromosome
Binary Fission
(1 cell splits
into 2)
Multiple linear chromosomes
compartmentalized in a
nucleus
1 single, circular
chromosome
1 single, circular
chromosome
Mitosis
Binary Fission
(1 cell splits into 2)
Binary Fission
(1 cell splits into 2)
"70 S"
"80 S"
"70 S"
"70 S"
Found in the
plasma
membrane
around cell
Not found in the plasma
membrane
around cell (found only in the
cell's mitochondria and
chloroplasts)
Found in the plasma
membrane around
mitochondrion
Found in the plasma
membrane around
chloroplast
~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 membranes
Smooth outer membrane
Inner membrane folded into cristae which increase surface area for enzymes that synthesize ATP
The 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 envelope
b. Endoplasmic reticulum
c. Golgi apparatus
d. Lysosomes
e. Vacuoles
f. Plasma membrane
36. What are the three components of the cytoskeleton?
a. Microtubules
b. Microfilaments
c. 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 fibronectin
ECM proteins bind to receptor proteins in the plasma membrane called integrins
F(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
b. Desmosomes (anchoring junctions) fasten cells together into strong sheets
c. Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells
fluid
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 it
Proposed by S. J. Singer and G. L. Nicolson in 1972
2. Proposed the fluid mosaic model which accounted of the amphipathic character of proteins
3. 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 helices
Peripheral 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 membrane
Membrane 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 – passive
Requires 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
membrane
Hypertonic solution: Solute concentration is greater than that inside the cell; cell loses water
Hypotonic solution: Solute concentration is less than that inside the cell; cell gains water
Cells without walls:
a. Isotonic—no change
b. 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 limp
b. 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 bilayer
Some 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
environment
Requires specific proteins embedded in the membranes
Energy from ATP
Types: 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 cell
ATP provide energy for the transport protein which causes a change in shape of transport protein
Transports 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- using
In endocytosis, the cell takes in macromolecules by forming vesicles from the plasma membrane
Endocytosis is a reversal of exocytosis, involving different proteins
There 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 motion
Potential 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 spontaneous
An 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 triphosphate
Consists 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
one
Most 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 (G = -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 + fructose
The enzyme binds to its substrate, forming an enzyme-substrate complex
Specificity is based on shape of enzyme
The active site is the region on the enzyme where the substrate binds
Induced fit of a substrate brings chemical groups of the active site into positions that enhance their ability to catalyze
the reaction
In an enzymatic reaction, the substrate binds to the active site of the enzyme
The active site can lower an EA barrier by
a. Act as a template for substrate orientation
b. Stressing the substrates and stabilizing the transition state
c. Providing a favorable microenvironment
d. Participating directly in the catalytic reaction
Initial substrate concentration partly determines the rate of an enzyme controlled reaction
The 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 conformation
Temperature
-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 2
Disrupts 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 site
Allosteric 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 pathway
Feedback 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 diffusion
Second 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 suicide
A cell is chopped and packaged into vesicles that are digested by scavenger cells
Cell 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 animals
Apoptosis 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 replicate
ii. 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 identical
Gametes (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
•
•
Metaphase
Stage
Anaphase
Synapsis occurs to form
tetrads
Chiasmata appear as
evidence that crossing
over has occurred
•
Neither synapsis nor crossing over occurs
Homologous pairs
(tetrads) align on the
metaphase plate
•
Individual doubled chromosomes align on metaphase plate
Meiosis
•
•
•
Mitosis
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
Meiosis II is basically identical to Mitosis
84. What is the difference in diploid and haploid?
Diploid – full set of chromosomes
Haploid – half set of chromosomes
•
•
•
Sister chromatids of individual doubled chromosomes
separate
Centromers divide
Sister chromatids move to opposite poles of the cell
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 replicates
iii. 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 disappear
b. Chromatin fibers become tightly coiled and folded to form
observable
chromosomes
Changes 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 fragments
3. Microtubules interact with chromosomes
4. Spindle fibers (bundles of microtubules) extend from each pole toward the equator
(midpoint between the poles) (aka metaphase plate) of the cell
iii.
iv.
v.
5. 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
Metaphase
8. Centrosomes positioned at poles (opposite ends ) of the cell
9. Chromosomes move to metaphase plate (plane equidistant between the spindle poles)
10. Centromeres of all chromosomes aligned on metaphase plate
11. Kinetochore fibers of sister chromatids face opposite poles so identical chromatids are
attached to kinetochore fibers radiating from opposite ends of the parent cell
12. Entire structure formed by nonkinetochore microtubules plus kinetochore microtubules
called the spindle
Anaphase
13. Begins when paired centromeres of each chromosome move apart
14. Sister chromatids separate and are considered chromosomes
15. Spindle apparatus starts moving the separate chromosomes toward opposite poles
16. Chromosomes move in a V-shape because of attachment of kinetochore fibers to
centromere
17. Kinetochore microtubules shorten at end attached to kinetochores
18. Poles of cell move farther apart slightly elongating the cell
19. At end of phase two poles have complete and equivalent collections of chromosomes
Telophase
20. Nonkinetochore microtubules further elongate the cell
21. Daughter nuclei begin to form at the two poles
22. Nuclear envelop reforms from fragments of parent cell nuclear envelope and other
portions of endomembrane system
23. Nucleoli reappear
24. Chromosomes uncoil and appear as chromatin
25. cytokinesis begins
88. Distinguish between cytokinesis in plant cell and animal cells.
a. Cytokinesis –
i.
Process of cytoplasmic division that follows mitosis
ii.
Begins in telophase
iii.
Differs in plant and animal cells
iv.
Animal Cells
1. Occurs as cleavage
2. 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 furrow
4. Microfilaments contract until parent cell is pinched in two
v.
Plant Cells
1. 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 center
3. Cell plate enlarges until its surrounding membrane fuses with the existing plasma
membrane
4. 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 death
b. 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 dividing
Anchorage 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 transformation
1. Cancer cells do not respond normally to the body’s control mechanisms
2. 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 tumor
Malignant 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