Bio 235 Chapter 3 Cellular Level Of Organization Flashcards
(220 cards)
1
Q
Basic, living, structural and functional units of the body.
A
Cells
2
Q
The scientific study of cells
A
cell biology or cytology.
3
Q
forms the cell’s flexible outer surface, sep-
arating the cell’s internal environment (everything inside the cell) from the external environment (everything outside the cell).
A
Plasma membrane
4
Q
Consists of all the cellular contents between the plasma membrane and the nucleus
A
Cytoplasm
5
Q
the fluid portion of the cytoplasm , contains water, dissolved solutes, and
suspended particles.
A
Cytosol
6
Q
a large organelle that houses
most of a cell’s DNA.
A
Nucleus
7
Q
flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell, is best described by using a structural model called the fluid mosaic model.
A
Plasma membrane
8
Q
the molecular arrangement of the plasma membrane resembles a continually moving sea of fluid lipids that contains a mosaic of many different proteins. Some proteins float freely like icebergs in the lipid sea, whereas others are anchored at specific locations like islands.
A
Fluid mosaic model
9
Q
two back-to-back layers made up of three types of lipid molecules-phospholipids, cholesterol, and glycolipids
A
Lipid bilayer
10
Q
About 75% of the membrane. lipids that contain phosphorus.
A
Phospholipids
11
Q
Functions or the Plasma membrane
A
- Acts as a barrier separating inside
and outside of the cell - Controls the flow of substances into and out of the cell.
- Helps Identify the cell to other cells (e.g., immune cells).
- Participates in intercellular signaling.
12
Q
extend into or through the lipid bilayer and are firmly embedded in it.
A
Integral proteins
13
Q
they span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid. A few integral proteins are tightly attached to one side of the bilayer by covalent bonding to fatty acids.
A
Transmembrane protein
14
Q
are not as firmly embedded in the membrane. They are attached to the polar heads of membrane lipids or to integral proteins at the inner or outer surface of the membrane
A
Peripheral proteins
15
Q
proteins with carbohydrate groups attached to the ends that protrude into the extracellular
fluid.
A
Glycoproteins
16
Q
The carbohydrate
portions of glycolipids and
glycoproteins form an extensive sugary coat called
A
Glycocalyx
17
Q
acts like a molecular “signature” that enables cells to recognize one another.
A
Glycocalyx
18
Q
Functions of membrane proteins.
A
lon channel (integral)
Carrier (integral)
Receptor (integral)
Enzyme (integral and peripheral)
Linker (integral and peripheral)
Cell identity marker(Glycoprotein)
19
Q
pores or holes that
specific ions, such as potassium ions (K”), can flow through to get into or out of the cell. Most are selective; they allow only a single type of ion to pass through.
A
Ion channels
20
Q
selectively moving a polar
substance or ion from one side of the membrane to the other.
also known as transporters.
A
Carriers
21
Q
serve as cellular recognition sites.
Each type recognizes and binds a specific type of mol-ecule. For instance, insulin receptors bind the hormone insulin.
A
Receptors
22
Q
A specific molecule that binds to a receptor is a ___ of that receptor
A
Ligand
23
Q
catalyze specific chemical
reactions at the inside or outside surface of the cell.
A
Enzymes
24
Q
anchor proteins in the plasma membranes of neighboring cells to one another or to protein filaments inside and outside the cell.
A
Linkers
25
Membrane glycoproteins and glycolipids often serve as
Cell identity markers
26
What do cell identity markers do
They may enable a cell to (1) recognize other cells of the
same kind during tissue formation or (2) recognize and respond to potentially dangerous foreign cells. The ABO blood type markers are one example of cell-identity markers. When you receive a blood transfusion, the blood type must be compatible with your own, or red blood cells may clump together.
27
depends both on the number of double bonds in the fatty acid tails of the lipids that make up the bilayer, and on the amount of cholesterol present.
Membrane fluidity
28
Plasma membranes permit some substances to pass more readily than others.
Selective permeability
29
difference in the concentration of a chemical from one place to another, such as from the inside to the outside of the plasma mem-brane.
Concentration gradient
30
A difference in electrical charges between two regions constitutes an
Electrical gradient
31
Because electrical gradient occurs across the plasma membrane, this charge difference is termed
Membrane potential
32
The combined influence of the con: centration gradient and the electrical gradient on movement of a particular ion is referred to as
Electrochemical gradient
33
suDi
stance moves down its concentration or electrical gradient to cross the membrane using only its own kinetic energy (energy of motion).
Kinetic energy is intrinsic to the particles that are moving. There is no input of energy from the cell. An example is simple diffusion.
Passive processes
34
cellular energy is used to drive the substance "uphill"
against its concentration or electrical gradient. The cellular energy used is usually in the form of adenosine triphosphate (ATP). An example is active transport.
Active processes
35
Another way that some substances may enter and leave cells is an active process in which tiny, spherical membrane sacs referred to as ___. Examples include endocytosis.
Vesicles
36
vesicles detach from the plasma membrane while bringing materials into a cell, and exocytosis, the merging of vesicles with the plasma membrane to release materials from the cell.
Endocytosis
37
a passive
process in which the random mixing of particles in a solution occurs because of the particles' kinetic energy. Both the solutes, the dissolved substances, and the solvent, the liquid that does the dissolv-ing, undergo diffusion. If a particular solute is present in high concentration in one area of a solution and in low concentration in another area, solute molecules will diffuse toward the area of lower concentration-they move down their concentration gradient.
Diffusion
38
factors that influence the diffusion rate
Steepness of the concentration gradient.
Temperature
Surface area
Mass of the diffusing substance.
Diffusion distance
39
The greater the difference in concentration between the two sides of the membrane, the higher the rate of diffusion.
Steepness of the concentration gradient
40
The higher it is, the faster the rate of dif-fusion.
Temperature
41
The larger the mass of the diffusing particle, the slower its diffusion rate. Smaller molecules diffuse more rapidly than larger ones.
Mass of the diffusing substance
42
The larger it is available for
diffusion, the faster the diffusion rate.
Surface area
43
The greater the distance over which diffusion must occur, the longer it takes.
Diffusion distance
44
passive process in which substances move freely through the lipid bilayer of the plasma membranes of cells without the help of membrane transport proteins
Simple diffusion
45
is important in the movement of oxygen and carbon dioxide between blood and body cells, and between blood and air within the lungs during breathing.
Simple diffusion through the lipid bilayer
46
an integral membrane protein assists a specific substance across the membrane. The integral membrane protein can be either a membrane channel or a carrier.
Facilitated diffusion
47
solute moves down its concentration gradient across the lipid bilayer through a membrane channel
Channel mediated facilitated diffusion
48
integral transmembrane
proteins that allow passage of small, inorganic ions that are too hydrophilic to penetrate the nonpolar interior of the lipid bilayer.
Ion channels
49
A channel is said to be gated
when
part of the channel protein
acts as a "plug" or "gate," changing shape in one way to open the pore and in another way to close it
50
a carrier (also called a transporter) moves a
solute down its concentration gradient across the plasma membrane
Carrier mediated facilitated diffusion
51
The number of carriers available in a plasma membrane places
an upper limit, called the____. on the rate at which
facilitated diffusion can occur.
Transport maximum
52
Glucose, the body's preferred energy source for making ATP, enters many body cells by carrier-mediated facilitated diffusion as follows
1. Glucose binds to a specific type of carrier protein called the glucose transporter (GluT) on the outside surface of the membrane.
2. As the transporter undergoes a change in shape, glucose passes through the membrane.
3. The transporter releases glucose on the other side of the
membrane.
53
a type of diffusion in which
there is net movement of a solvent through a selectively permeable membrane. Passive process
Osmosis
54
water moves through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
Osmosis
55
integral membrane proteins that
function as water channels. play a critical role in controlling the water content of cells.
Aquaporins
56
responsible for the production of cerebrospinal fluid, aqueous humor, tears, sweat, saliva, and the concentration of urine.
Aquaporins
57
the higher the column of solution in the right arm becomes, the more pressure it exerts on its side of the membrane.
Hydrostatic pressure
58
proportional to the concentration of the solute particles that cannot cross the membrane-the higher the solute concentration, the higher it is
Osmotic pressure
59
measure of the solution's ability to change the
volume of cells by altering their water content.
Tonicity
60
Any solution in which a cell-for example, a red blood cell (RBC) - maintains its normal shape and volume
Isotonic solution
61
a solution that has a lower concentration of solutes than the cytosol inside the RBCS. In this case, water molecules enter the cells faster than they leave, causing the RBCs to swell and eventually to burst.
Hypotonic solution
62
The rupture of RBCs where it swell and eventually bursts
Hemolysis
63
the rupture of other types of
cells due to placement in a hypotonic solution
Lysis
64
has a higher concentration of solutes than does the cytosol inside RBCs. One example is a 2% Nacl solution. In such a solution, water molecules move out of the cells faster than they enter, causing the cells to shrink.
Hypertonic solution
65
When cells shrink due to water molecules moving out of it faster than they enter.
Crenation
66
active process because energy is required for carrier proteins to move solutes across the membrane against a concentration gradient.
Active transport
67
Two sources of cellular energy can be used to drive active transport:
(1) Energy obtained from hydrolysis of adenosine triphosphate (ATP) is the source in primary active transport:
(2) energy stored in an ionic concentration gradient is the source in secondary active transport.
68
energy
derived from hydrolysis of ATP changes the shape of a carrier protein, which "pumps" a substance across a plasma membrane against its concentration gradient.
Primary active transport
69
carrier proteins that mediate primary active transport
Pumps
70
The most prevalent primary active transport mechanism expels sodium ions (Na*) from cells and brings potassium ions (K*) in. Because of the specific ions it moves, this carrier is called
Sodium potassium pump
71
The most prevalent primary active transport mechanism expels sodium ions (Na*) from cells and brings potassium ions (K*) in. Because of the specific ions it moves, this carrier is called
Secondary active transport
72
a carrier protein simultaneously binds to Na and another substance and then changes its shape so that both substances cross the membrane at the same time.
Secondary active transport
73
the transporters in a secondary active transport that moves two substances in the same direction are called
Symporters
74
Transporters that move two substances in opposite directions across the membrane in a secondary active transport
Antiporters
75
three
types of endocytosis:
receptor-mediated endocytosis, phagocytosis, and bulk-phase endo-cytosis.
76
highly selective type
of endocytosis by which cells take up specific ligands.
Receptor-mediated endocytosis
77
Receptor-mediated endocytosis of LDLs (and other ligands) occurs as follows:
Binding.
Vesicle formation
Uncoating
Fusion with endosome
Recycling of receptors to plasma membrane
Degradation in lysosomes
78
a protein in plasma membrane that attaches to the membrane on its cytoplasmic side.
Clathrin
79
"cell eating" is a form of endocytosis in which the cell engulfs large solid particles, such as worn-out cells, whole bacteria, or viruses
Phagocytosis
80
Two main types of phagocytes and location
Macrophages located in many body tissues
Neutrophils, a type of white blood cell
81
A vesicle during phagocytosis
phagosome
82
Also called pinocytosis, or cell drinking. A form of endocytosis in which tiny droplets of extracellular fluid are taken up
Bulk-phase endocytosis
83
the plasma membrane folds inward and forms a vesicle containing a droplet of extracellular fluid. The vesicle detaches or "pinches off " from the plasma membrane and enters the cytosol.
Bulk-phase endocytosis
84
2 types of cells where exocytosis is important
(1) secretory cells that liberate digestive enzymes, hormones, mucus, or other secretions and
(2) nerve cells that release substances called neurotransmitters
85
membrane-enclosed vesi-cles that form inside the cell, fuse with the plasma membrane, and release their contents into the extracellular fluid.
Secretory vesicles
86
vesicles underge endocytosis on one side of a cell, move across the cell, and then undergo exocytosis on the opposite side.
Transcytosis
87
consists of all the cellular contents between the plasma membrane and the nucleus, and has two components:
Cytoplasm
88
2 components of cytoplasm
1) the cytosol and (2) organelles, tiny structures that perform different functions in the cell
89
is the fluid portion of the cytoplasm that surrounds organelles
Cytosol
90
the site of many chemical reactions required for a cell's existence.
Cytosol
91
network of protein filaments that extends throughout the cytoplasm
Cytoskeleton
92
are the thin-
nest elements of the cytoskeleton. They are composed of the proteins actin and myosin and are most prevalent at the edge of a cell
Microfilaments
93
two general functions of microfilaments
They help generate movement and provide mechanical support.
94
How do microfilament help generate movement
involved in muscle contraction, cell division, and cell locomotion, such as occurs during the migration of embryonic cells during development, the invasion of tissues by white blood cells to fight infection, or the migration of skin cells during wound healing.
95
How do microfilaments provide mechanical support
responsible for the basic strength and shapes of cells. They anchor the cytoskeleton to integral proteins in the plasma membrane.
96
Functions of cytoskeleton
Serves as a scaffold that helps determine a cell's shape and organize
une cellular contents.
2. Aids movement of organelles within the cell, of chromosomes during cell division, and of whole cells such as phagocytes.
97
nonmotile, Microscopic fingerlike
projections of the plasma membrane. Because they greatly increase the surface area of the cell, they are abundant on cells involved in absorption, such as the epithelial cells that line the small
Microvilli
98
thicker than microfilaments but thinner than microtubules. are found in parts of cells subject to mechanical stress; they help stabilize the position of organelles such as the nucleus and help attach cells to one another.
Intermediate filaments
99
the largest of the
cytoskeletdl
components
are long, unbranched hollow tubes
composed mainly of the protein tubulin.
Microtubules
100
specialized structures within the cell that have characteristic shapes, and they perform specific functions in cellular growth, maintenance, and reproduction.
Organelles
101
Located near the nucleus, consists of a pair of centrioles and the pericentriolar matrix.
Centrosome
102
Functions of the Centrosomes
1) pericentrioral matrix of the centrosome contains tubulins that
build microtubules in nondividing cells.
2. The pericentriolar matrix of the centrosome forms the mitotic spindle during cell division
103
Also known as microtubule organizing center
Centrosome
104
are cylindrical structures, each composed of nine clusters of three microtubules (triplets) arranged in a circular pattern
Centrioles
105
Contains hundreds of
Ring-shaped complexes composed or
the protein tubulin. These tubulin complexes are the organizing centers for growth of the mitotic spindle, which plays a critical role in cell division, and for microtubule formation in nondividing cells.
Pericentriolar matrix
106
numerous, short, hairlike projections that extend from the surface of the cell
Cilia
107
contains a core or microtubules with one pair in the center Surrounded of nine clusters of doublet microtubules
Cilium
108
Functions of the Cilia
Cilia move fluids along a cell's surface.
109
Function of flagella
flagellum moves an entire cell.
110
are the sites of protein synthesis.
Ribosomes
111
Functions of ribosomes
1. Ribosomes associated with endoplasmic reticulum synthesize proteins destined for insertion in the plasma membrane or secretion from the cell.
2. Free ribosomes sunthesize proteins used in the cvtosol.
112
located within mitochondria, where they synthesize mitochondrial proteins.
Ribosomes
113
is a network of membranes in the form of flattened sacs or tubules that extend throughout the cytoplasm and connect to the nuclear envelope
endoplasmic reticulum (ER)
114
continuous with the nuclear membrane and usu-
ally is folded into a series of flattened sacs. The outer Surface is studded with ribosomes, the sites of protein synthesis.
Rough ER
115
does not have ribosomes on the outer surfaces of its membrane. However they contains unique enzymes that make it functionally more diverse than rough ER. Because it lacks ribosomes, it does not synthesize proteins, but it does synthesize fatty acids and steroids, such as estrogens and testosterone.
Smooth ER
116
Function of rough ER
synthesizes glycoproteins and phospholipids that are transferred into cellular
organelles, Inserted Into the plasma membrane, or secreted during exocytosis.
117
Function of smooth ER
synthesizes fatty acids and steroids, such as estrogens and testosterone, inactivates or detoxifies drugs and other potentially harmful substances; removes the phosphate group from glucose-6-phosphate; and stores and releases calcium ions that
Trigger contraction in muscle cells.
118
The first step in the transport pathway is through an organelle called
Golgi complex
119
small, flattened membranous sacs with bulging edges that resemble a stack of pita bread
Cisterns
120
more extensive in cells that secrete proteins, a clue to the organelle's role in the cell.
Golgi complex
121
cistern that faces the rough ER.
convex entry (cis) face
122
cistern that faces the plasma membrane.
concave exit (trans) face
123
Sacs between the entry and exit faces
Medial cisterns
124
Functions of the Golgi Complex
1. Modifies, sorts, packages, and transports proteins received from the rough ER.
2. Forms secretory vesicles that discharge processed proteins via exocytosis into extracellular
Tula, toms memorane vesicles that temy new moiccules to the plasma membrane, forms
transport vesicles that carry molecules to other organelles, such as lysosomes.
125
receives and modifies proteins produced by the rough ER.
Entry face
126
add carbohydrates to proteins to form glycoproteins and lipids to proteins to form lipoproteins.
Medial cisterns
127
modifies the molecules further and then sorts and packages them for transport to their destinations
Exit face
128
Proteins arriving at, passing through, and exiting the Golgi complex do so through this, which occur via transfer vesicles
maturation of the cisternae and exchanges
129
These vesicles deliver the proteins to the
plasma membrane, where they are discharged by exocytosis into the extracellular fluid. For example, certain pancreatic cells release the hormone insulin in this way.
Secretory vesicles
130
deliver their contents to the plasma membrane for incorporation into the membrane. In doing so, the Golgi complex adds new segments of plasma membrane as existing segments are lost and modifies the number and distribution of membrane molecules
Membrane vesicles
131
All proteins exported from the cell are processed in
Golgi complex
132
They can contain as many as 60 kinds of powerful digestive and hydrolytic enzymes that can break down a wide variety of molecules once lysosomes fuse with vesicles formed during endocytosis.
Lysosomes
133
help recycle worn-out cell structures.
Can engulf another organelle, digest it, and return the digested components to the cytosol for reuse.
Lysosome
134
The process by which entire worn-out organelles are digested
Autophagy
135
The process by which entire worn-out organelles are digested
Autophagy
136
the organelle to be digested is enclosed by a membrane derived from the ER to create a vesicle called
Autophagosome
137
destroy the entire cell that contains them,
Autolysis
138
also called microbodies, contain several oxidases, enzymes that can exidize (remove hydrogen atoms from) various organic substances
Peroxisome
139
Functions or Lysosomes
1. Digest substances that enter a cell via endocytosis and transport final products of digestion into cytosol.
2. Carry out autophagy, the digestion of worn-out organelles.
3. Implement autolysis, the digestion of an entire cell.
4. Accomplish extracellular digestion.
140
Continuous destruction of unneeded, damaged, or faulty proteins is the function of tiny barrel-shaped structures consisting of four stacked rings of proteins around
a central core called
Proteasomes
141
Functions of Mitochondria
1. Generate ATP through reactions of aerobic cellular respiration.
2. Play an important early role in apoptosis.
142
rererred lo as the powerhouse of the cell.
Mitochondria
143
contains a series of folds called mitochondrial Cristae
internal mitochondrial membrane
144
The central fluid-filled cavity of a mitochondrion, enclosed by the internal mitochondrial membrane,
Mitochondrial matrix
145
The orderly, genetically programmed cell death
Apoptosis
146
spherical or oval-shaped structure that usually is the most prominent feature of a cell
Nucleus
147
A double membrane. It separates the nucleus from the cytoplasm. Both layers of it are lipid bilayers similar to the plasma membrane.
Nuclear envelope
148
control the movement of substances between the nucleus and the cytoplasm. Small molecules and ions move through it passively by diffusion.
Nuclear pores
149
Inside the nucleus are one or more spherical bodies that function in producing ribosomes
Nucleoli
150
the sites of synthesis of RNA and assembly of RNA and proteins into ribosomal subunits. Are quite prominent in cells that synthesize large amounts of protein, such as muscle and liver cells.
Nucleoli
151
Complex of DNA, proteins and some RNA
Chromatin
152
The
total genetic information carried in
an organism
Genome
153
Electron micrographs reveal that chromatin has a beads-on-a-string structure. Each bead is a
Neuclosome
154
Function of nucleus
1. Controls cellular structure.
2. Directs cellular activities.
3. Produces ribosomes in nucleoli.
155
core of eight proteins found in chromosome
Histone
156
The string between the
Beads in chromosome
Linker DNA
157
In cells that are not dividing, another histone promotes coiling of nucleosomes into a larger-diameter which then folds into large loops.
Chromatin fiber
158
refers
to all of an organism's proteins.
Proteome
159
refers
to all of an organism's proteins.
Proteome
160
a gene's DNA is used as a template for synthesis of a specific protein.
Gene expression
161
the information encoded in a specific region of DNA is transcribed (copied) to produce a specific molecule of RNA (ribonucleic acid).
Transcription
162
the
RNA attaches to a ribosome, where the information contained in RNA is translated into a corresponding sequence of amino acids to form a new protein molecule
Translation
163
A sequence of three such nucleotides in DNA
Base triplet
164
Each DNA base triplet is transcribed as a complementary se-
quence of three nucleotides, called
Codon
165
the set of rules that relate the base triplet sequence of DNA to the corresponding codons of RNA and the amino acids they specify.
Genetic code
166
Where does transcription occur
Nucleus
167
Where does translation occur
Cytoplasm
168
Three types of RNA made from the DNA template:
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
169
directs the synthesis of a protein.
Messenger RNA (mRNA)
170
the genetic infor-mation represented by the sequence of base triplets in DNA serves as a template for copying the information into a complementary sequence or codons.
Transcription
171
joins with ribosomal proteins to make ribosomes.
Ribosomal RNA (rRNA)
172
binds to an amino acid and holds it in place
on a ribosome until it is incorporated into a protein during translation.
Transfer RNA (tRNA)
173
the opposite end of tRNA consists of a triplet of nucleotides called
Anticodon
174
The enzyme that catalyzes transcrip-tion of DNA. However, the enzyme must be instructed where to start the transcription process and where to end it.
RNA polymerase
175
Ine segment of DNA where transcription begins, a special nucleotide sequence called
Promoter
176
Transcription of the DNA strand ends at another special nucleo-
tide sequence called
Terminator
177
do not code for parts of proteins.
Introns
178
Region where introns are located that do code for segments of a pro-
tein.
Exons
179
Who carries out translation
Ribosomes in cytoplasm
180
the process by
which cells reproduce themselves.
Cell division
181
any cell of the body
other than a germ cell.
Somatic cell
182
any precursor cell destined to become a gamete.
Germ cell
183
nuclear division
Mitosis
184
cytoplasmic division
Cytokinesis
185
A cell undergoes mitosis and cytokinesis to produce genetically identical cells, each with the same number and kind of chromosomes as the original cell
Somatic cell division
186
the mechanism that produces gametes, the cells needed to form the next generation of sexually reproducing organisms.
Reproductive cell division
187
number of chromosomes in the nucleus is reduced by half
Meiosis
188
an orderly sequence of events in which a somatic cell duplicates its contents and divides in two.
Cell cycle
189
One member of
make up each pair are called
Homologous chromosomes
190
one pair of chromosomes designated X and Y
Sex chromosomes
191
Because
somatic cells contain two sets of chromosomes. they are called
Diploid cells
192
It is during this time that the cell does most of its growing.
Interphase
193
periods when there is no activity related to DNA duplication, they are thought of as gaps or interruptions in DNA duplication.
G phases
194
During this phase, DNA replication occurs. As a result of DNA replica-tion, the two identical cells formed during cell division later in the cell cycle will have the same genetic material.
S phase
195
results in the formation or two identical cells, consists or a nuclear division (mitosis) and a cytoplasmic division (cytokinesis) to form two identical cells.
Mitotic phase
196
4 stages of mitosis
prophase, metaphase, anaphase, and telophase.
197
the chromatin fibers condense and shorten into chromosomes that are visible under the light microscope
Prophase
198
A constricted region which holds the chromatid pair together.
Centromere
199
outside of each centromere is a protein complex known as
Kinetochore
200
football-shaped assembly or microtubules that
attach to the kinetochore
Mitotic spindle
201
the microtubules of the mi-totic spindle align the centromeres of the chromatid pairs at the exact
center or the mitotic spindle
Metaphase
202
plane of alignment of
the centromeres
Metaphase plate
203
the centromeres split, separating the two members of each chromatid pair, which move toward opposite poles of the cell
Anaphase
204
Once separated, the chromatids are termed
Chromosomes
205
begins after chromosomal movement stops
Telophase
206
identical sets of chromosomes, now at opposite poles of the cell, uncoil and revert to the threadlike chromatin form.
Telophase
207
slight indentation of the plasma membrane,
Cleavage furrow
208
cell has three possible
Destinies
(1) to remain alive and functioning
without dividing, (2) to grow and divide, or (3) to die.
209
Period between cell divisions; chromosomes not visible under light microscope.
Interphase
210
Metabolically active cell duplicates most of its organelles and cytosolic components; replication of chromosomes begins. (Cells that remain in the G, phase for a very long time, and possibly never divide again, are said to be in the G, phase.)
G1 phase
211
Replication of DNA and centrosomes.
S phase
212
Cell growth, enzyme and protein synthesis continue; replication of centrosomes complete
G2 phase
213
Cytoplasmic division; contractile ring forms cleavage furrow around center of cell, dividing cytoplasm into separate and equal portions
Cytokinesis
214
Nuclear envelopes and nucleoli reappear; chromosomes resume chromatin form; mitotic spindle disappears.
Telophase
215
pathological type of cell death that results
from tissue injury.
Necrosis
216
the reproductive cell division that eccurs in the gonads (ovaries and testes. produces gametes.in which the number of chromosomes is reduced by half.
Meiosis
217
two successive stages of meiosis
Meiosis I and Meiosis II
218
the two sister chromatids of each pair of homolo-gous chromosomes pair off, an event called
Synapsis
219
This process, among others, permits an exchange of
genes between chromatids of homologous chromosomes.
Crossing over
220
The sizes of cells are measured in units
called
Micrometers
