Chapter 1: The Facts of Life Flashcards
(144 cards)
1
Q
__ are lifeless. Yet, the properties of living things derive from the properties of __.
A
Molecules; molecules
2
Q
Who said, “Living things are composed of lifeless molecules.”
A
Albert Lehninger
3
Q
Who said,“…everything that living things do can be understood in terms of the jigglings and wigglings of atoms.”
A
Richard P. Feynman
4
Q
Distinctive properties of living systems
A
1) Organisms are complicated and highly organized
2) Biological structures serve functional purposes
3) Living systems are actively engaged in energy transformations
4) Living systems have a remarkable capacity for self-replication
5
Q
Living systems are distinct from the inanimate world because they have certain extraordinary properties. They can grow, move, and perform the incredible chemistry of:
A
- metabolism
- respond to stimuli from the environment
- replicate
6
Q
organisms are composed of many __, typically of many types. In turn, these possess subcellular structures, called __, which are complex assemblies of very large polymeric molecules, called __.
A
- cells
- organelles
- macromolecules
7
Q
macromolecules themselves show an exquisite degree of organization in their intricate __, even though they are composed of simple sets of chemical building blocks, such as __ and __.
A
- three-dimensional architecture
- sugars
- amino acids
8
Q
- the complex three-dimensional structure of macromolecules is __
- a consequence of interactions between the __, according to their individual chemical properties.
A
- conformation
- monomeric units
9
Q
it is this __ that separates the science of biology from studies of the inanimate world such as chemistry, physics, and geology.
A
functional characteristic of biological structures
10
Q
In biology, it is always meaningful to seek the __ of observed structures, organizations, or patterns; that is, to ask what __ they serve within the organism.
A
- purpose
- functional role
11
Q
- Made of long chains of 20 amino acids
- Most of the structure and function of living things
A
Proteins
12
Q
- Made of long and short chains of nucleic acid bases form DNA, RNA, also ATP, GTP…
- Informational storage (RNA, DNA), structure, enzymes, energy transfer
A
Nucleic Acid
13
Q
- Made of phosphate or other charged “head” with a long hydrocarbon tail
- Energy Storage, insulation, cushioning, membranes
A
Lipids
14
Q
- Made of long and short chains of sugar molecules like glucose, fructose
- Energy source, energy storage, structure
A
Carbohydrates
15
Q
- Made of various molecules such as hormones, vitamins, neurotransmitters, porphyrins
- mostly sending signals
A
small molecules
16
Q
Maintenance of the highly organized structure and activity of living systems depends on their ability to __ from the environment.
A
extract energy
17
Q
The ultimate source of energy
A
sun
18
Q
Solar energy flows from __ (organisms able to capture light energy by the process of photosynthesis) through food chains to __ and ultimately to __ at the apex of the food pyramid. The biosphere is thus a system through which __.
A
- photosynthetic organisms
- herbivores
- carnivorous predators
- energy flows
19
Q
Organisms capture some of this energy, be it from photosynthesis or the metabolism of food, by forming special energized biomolecules, of which __ and __ are the two most prominent examples
A
- ATP
- NADPH
20
Q
energized biomolecules because they represent chemically useful forms of stored energy.
A
- Adenosine triphosphate (ATP)
- Nicotinamide adenosine dinucleotide phosphate hydrogen (NADPH)
21
Q
when ATP and NADPH molecules react with other molecules in the cell, the energy released can be used to drive energetically unfavorable processes. That is, ATP, NADPH, and related compounds are the power sources that drive the energy-requiring activities of the cell, including:
A
- biosynthesis
- movement
- osmotic work against concentration gradients
- light emissions (bioluminescence) *in special instances
22
Q
Only upon __ does an organism reach equilibrium with its inanimate environment
A
death
23
Q
At the expense of this energy flow, the organism can maintain its intricate order and activity far removed from equilibrium with its surroundings, yet exist in a state of apparent constancy over time. This state of apparent constancy, or so-called __, is actually a very dynamic condition: Energy and material are consumed by the organism and used to maintain its stability and order.
A
steady state
24
Q
A thermodynamic term used to designate
that amount of energy in a system that is unavailable to do work.
A
entropy
25
__, as exemplified by the universe in totality, is moving to a condition of increasing disorder or, in thermodynamic terms, __
- inanimate matter
- maximum entropy
26
Self-replication can proceed by a variety of mechanisms, ranging from __ in bacteria to __ in plants and animals; but in every case, it is characterized by an astounding __
- simple division
- sexual reproduction
- degree of fidelity
27
the degree of exactness with which something is copied or reproduced
fidelity
28
Energy and material are consumed by the organism and used to maintain its __. Living organisms are able to extract free energy from the environment and export entropy (in the form of __).
- stability and order
- heat
29
The fidelity of self-replication resides ultimately in the chemical nature of the __. This substance consists of __ of deoxyribonucleic acid, or DNA, which are structurally complementary to one another
- genetic material
- polymeric chains
30
These molecules can generate new copies of themselves in a rigorously executed __ that ensures a faithful reproduction of the original __.
- polymerization process
- DNA strands
31
the molecules of the inanimate world lack the capacity to __. A crude mechanism of __ must have existed at life’s origin.
- replicate
- replication
32
The elemental composition of living matter differs markedly from the relative abundance of elements in the __. __, __, __, and __ constitute more than 99% of the atoms in the human body, with most of the __ and __ occurring as __.
- earth’s crust
- Hydrogen, oxygen, carbon, nitrogen
- H, O, H2O
33
the predominant gas in the atmosphere
Nitrogen as dinitrogen (N2)
34
abundant in the atmosphere and in the oceans
oxygen
35
present at a level of 0.04% in the atmosphere, a small but critical amount
carbon dioxide
36
What property unites H, O, C, and N and renders these atoms so suitable to the chemistry of life?
- It is their ability to form covalent bonds by electron-pair sharing.
- H, C, N, and O are among the lightest elements of the periodic table capable of forming such bonds. Because the strength of covalent bonds is inversely proportional to the atomic weights of the atoms involved, H, C, N, and O form the strongest covalent bonds
37
Two other covalent bond-forming elements, ___ , also play important roles in biomolecules.
- phosphorus (as phosphate derivatives)
- sulfur
38
can share two electron pairs to form double bonds with one another within biomolecules, a property that enhances their __.
- Carbon, Nitrogen, Oxygen
- chemical versatility
39
can form covalent bonds with itself and __ shape; these broperties hold the potential for an incredible variety of __, __, and __compounds of __
- Carbon
- tetrahedral
- linear , branched, cyclic
- Carbon
40
Carbon can form as many as __ such bonds by sharing each of the __ in its __ with electrons contributed by other atoms. Atoms commonly found in covalent linkage to C are C itself, H, O, and N. Hydrogen can form __ such bond by contributing its __ to the formation of an __. Oxygen, with __ unpaired electrons in its outer shell, can participate in __ covalent bonds, and nitrogen, which has __ unshared electrons, can form __ such covalent bonds.
- four
- four electrons
- outer shell
- one
- single electron
- electron pair
- two; two
- three; three
41
Two properties of carbon covalent bonds that merit particular attention
- the ability of carbon to form covalent bonds with itself
- the tetrahedral nature of the four covalent bonds when carbon atoms form only single bonds
42
biomolecules are classified according to the __ and __, an organizational pattern emerges.
- similarities of their sizes ; chemical properties
43
The biomolecules are built according to a __: Simple molecules are the units for building __.
- structural hierarchy
- complex structures
44
The major inorganic precursors for the formation of biomolecules
▪ Water (H2O)
▪ carbon dioxide (CO2)
▪ ammonium (NH4+)
▪ nitrate (NO3-)
▪ dinitrogen (N2)
45
In the first step, the major inorganic precursors are converted into __, simple organic compounds that are intermediates in cellular energy transformation and in the biosynthesis of various sets of building blocks: __
- metabolites
- amino acids
- sugars
- nucleotides
- fatty acids
- glycerol
46
Through the covalent linkage of the building blocks, the __ are constructed: __(4)
- macromolecules
- proteins
- polysaccharides
- polynucleotides (DNA and RNA)
- lipids
47
- contain relatively few building blocks and are therefore not really polymeric like other macromolecules
- important contributors to higher levels of complexity
lipids
48
Interactions among macromolecules lead to the next level of structural organization, __.
supramolecular complexes
49
Here, various members of one or more of the classes of macromolecules come together to form specific assemblies that serve important sub-cellular functions.
supramolecular complexes
50
Examples of supramolecular assemblies
- multifunctional enzyme complexes
- ribosomes
- chromosomes
- cytoskeletal elements
51
supramolecular assemblies are an interesting contrast to their components because their structural integrity is maintained by __, not by __. These forces include __, __, __, and __ between macromolecules. Such forces maintain these __ in a __.
- noncovalent forces; covalent bonds
- hydrogen bonds
- ionic attractions
- van der Waals forces
- hydrophobic interactions
- supramolecular assemblies; highly ordered functional state
52
- entities of considerable dimensions compared with the cell itself
- found only in eukaryotic cells, that is, the cells of “higher” organisms
organelles
53
Organelles
- Nucleus
- Mitochondria
- Chloroplasts
- endoplasmic reticulum
- Golgi apparatus
- Vacuoles
- other relatively small cellular inclusions such as peroxisomes, lysosomes, and chromoplasts
54
Two attributes of organelles
- They are cellular inclusions, usually membrane-bounded
- They are dedicated to important cellular tasks.
55
the repository of genetic information as contained within the linear sequences of nucleotides in the DNA of chromosomes.
nucleus
56
the “power plants” of cells by virtue of their ability to carry out the energy-releasing aerobic metabolism of carbohydrates and fatty acids, capturing the energy in metabolically useful forms such as ATP
mitochondria
57
endow cells with the ability to carry out photosynthesis. They are the biological agents for harvesting light energy and transforming it into metabolically useful chemical forms
Chloroplasts
58
define the boundaries of cells and organelles. As such, they are not easily classified as supramolecular assemblies or organelles, although they share the properties of both
membranes
59
resemble supramolecular complexes in their construction because they are complexes of proteins and lipids maintained by noncovalent forces.
membrane
60
- particularly important in maintaining membrane structure
- arise because water molecules prefer to interact with each other rather than with nonpolar substances.
hydrophobic interactions
61
The presence of ___ lessens the range of opportunities for water–water interaction by forcing the water molecules into ordered arrays around the nonpolar groups.
nonpolar molecules
62
the creative means of membrane formation and the driving force that presumably established the boundary of the first cell.
hydrophobic interactions
63
The membranes of organelles, such as nuclei, mitochondria, and chloroplasts, differ from one
another, with each having a __ tailored to the organelle’s function.
characteristic protein and lipid composition
64
the creation of discrete volumes, or __, within cells is not only an inevitable consequence of the presence of membranes, but usually an essential condition for proper __.
- compartments
- organellar function
65
If we consider what attributes of biomolecules render them so fit as components of growing, replicating systems, several biologically relevant themes of structure and organization emerge.
- we will see that these themes serve as principles of biochemistry. Prominent among them is the
the necessity for information and energy in the maintenance of the living state
66
Other biomolecules must have the capacity to __ this information so that the organized structures essential to life are __. Interactions between these structures are the processes of life.
- translate
- synthesized
67
The macromolecules of cells are built of __—__in proteins, __ in nucleic acids, and __ in polysaccharides—that have __.
- monomeric units
- amino acids
- nucleotides
- carbohydrates
- structural polarity
68
macromolecules are not symmetrical, and so they can be thought of as having a __ and a __. Polymerization of these units to form macromolecules occurs by __. Hence, the macromolecule has a __ to its structure
- “head” ; “tail"
- head-to-tail linear connections
- “sense” or direction
69
Not all biological macromolecules are rich in information. Polysaccharides are often composed of the same sugar unit repeated over and over, as in __ or __, which are __ of many glucose units.
On the other hand, proteins and polynucleotides are typically composed of building blocks arranged in __; that is, their sequences are unique, akin to the letters and punctuation that form this descriptive sentence. In these unique sequences lies __. Discerning the meaning, however, requires some __
- cellulose; starch
- homopolymers
- no obvious repetitive way
- meaning
- mechanism for recognition
70
(a) Amino acids build __.
(b) Polysaccharides are built by __.
(c) Nucleic acids are __.
All these polymerization processes involve bond formations accompanied by the __
- proteins
- joining sugars together
- polymers of nucleotides
- elimination of water (dehydration synthesis reactions)
71
The sequence of monomeric units in a
biological polymer has the potential to contain information if the __. __and __ are information-rich molecules; __ are not.
- diversity and order of the units are not overly simple or repetitive
- Nucleic acids; proteins
- polysaccharides
72
Although proteins are linear sequences of covalently linked amino acids, the course of the protein chain can __, __, and __ in the three
dimensions of space to establish a __ that is an
identifying characteristics of the given protein molecule
- turn
- fold
- coil
- specific, highly ordered architecture
73
__ hold atoms together so that molecules are formed. In contrast, __ are intramolecular or intermolecular attractions between atoms. None of these forces, which typically range from 4 to 30 kJ/mol, are strong enough to bind __ atoms together
- Covalent bonds
- weak chemical forces or noncovalent bonds (hydrogen bonds, van der Waals forces, ionic interactions, and hydrophobic interactions)
- free
74
The average kinetic energy of molecules at 25°C is __, so the energy of weak forces is only several times greater than the dissociating tendency due to the __. Thus, these weak forces create interactions that are __ at physiological temperature, unless by cumulative number they impart stability to the structures generated by their collective action.
- 2.5 kJ/mol
- thermal motion of molecules
- constantly forming and breaking
75
What properties of biomolecules endow them with the potential for such remarkable qualities?
Biological macromolecules and their building blocks have a “sense” or directionality
76
* result from the induced electrical interactions between closely approaching atoms or molecules
* __ that fluctuate instantaneously in time are attracted to __ and the electrons of nearby atoms
* operate only over a very limited interatomic distance (__)
- Van der Waals forces
- negatively charged electron clouds
- positively charged nuclei
- 0.3 to 0.6 nm
77
* form between a hydrogen atom covalently bonded to an __ (such as oxygen or nitrogen) and a second electronegative atom that serves as the __
* cylindrically symmetrical and tend to be __, forming straight bonds between
donor, hydrogen, and acceptor atoms.
- Hydrogen bonds
- electronegative atom
- hydrogen bond acceptor
- highly directional
78
Strength depends on the relative size of the atoms or molecules and the distance between them. The size factor determines the area of contact between two molecules: The greater the __, the stronger the __
- van der Waals interactions
- area; interaction
79
Relative strength is proportional to the __ and __. More polar atoms form stronger H bonds
- Hydrogen bonds
- polarity of the H bond donor; H bond acceptor
80
Strength also depends on the relative polarity of the interacting charged species. Examples that are also H bonds: --NH3+. . . -OOC--
Ionic interactions
81
Force is a complex phenomenon determined by the degree to which the structure of water is disordered as discrete hydrophobic molecules or molecular regions coalesce.
- Van der Waals packing is enhanced in molecules that are structurally complementary. hydrophobic interactions
81
Van der Waals packing is enhanced in molecules that are __.
structurally complementary
82
When two atoms approach each other so closely that their electron clouds interpenetrate, strong repulsive __ occur
van der Waals forces
83
is the interatomic distance that results if only van der Waals forces hold two atoms together
van der Waals contact distance
84
Hydrogen bonds, at a strength of __, are stronger than van der Waals forces and have an additional property: H bonds are __ and tend to be highly directional, forming straight bonds between donor, hydrogen, and acceptor atoms.
- 12 to 30 kJ/mol
- cylindrically symmetrical
85
Hydrogen bonds are also more specific than __ because they require the presence of complementary hydrogen donor and acceptor groups.
van der Waals interactions
86
* attractive forces between oppositely charged structures
* the electrical charge is __, so these interactions may lack the __ of hydrogen bonds or the __ of van der Waals interactions
- Ionic interactions
- radially distributed
- directionality
- precise fit
87
Ionic interactions may involve:
- Ions - species possessing discrete charges
- permanent dipoles - having a permanent separation of positive and negative charge
- induced dipoles - having a temporary separation of positive and negative charge induced by the environment
88
species possessing discrete charges
ions
89
having a permanent separation of positive
and negative charge
permanent dipoles
90
having a temporary separation of positive
and negative charge induced by the environment
induced dipoles
91
because the opposite charges are restricted to sterically defined positions, ionic interactions can impart a __
high degree of structural specificity
92
result from the strong tendency of water to exclude nonpolar groups or molecules
hydrophobic interactions
93
hydrophobic interactions arise not so much because of any intrinsic affinity of nonpolar substances for one another (although van der Waals forces do promote the weak bonding of nonpolar substances), but because __, compared with their interaction with nonpolar molecules.
water molecules prefer the stronger interactions that they share with one another
94
Hydrogen-bonding interactions between polar water molecules can be more varied and numerous if __. This phase separation __ of water because individual nonpolar molecules are no longer dispersed in the water, and thus, water molecules are no longer arranged in orderly arrays around them. It is these preferential interactions between water molecules that “exclude” hydrophobic substances from aqueous solution and drive the tendency of nonpolar molecules to cluster together.
- nonpolar molecules come together to form a distinct organic phase
- raises the entropy
95
nonpolar regions of biological macromolecules are often buried in the molecule’s __ to exclude them from the __.
- interior
- aqueous milieu (environment)
96
The formation of oil droplets as hydrophobic nonpolar lipid molecules that coalesce in the presence of water is an approximation of this phenomenon. These tendencies have important consequences in the __ and __ of living cells.
- creation and maintenance of the macromolecular structures
- supramolecular assemblies
97
the means of recognition in biomolecular interactions.
structural complementarity
98
The complicated and highly organized patterns of life depend on the ability of biomolecules to __
recognize and interact with one another in very specific ways
99
__ underlie the interactions that are the basis of biomolecular recognition. It is important to realize that because these interactions are sufficiently __, they are __.
- Weak chemical forces
- weak; readily reversible
100
biomolecular interactions tend to be __; rigid, static lattices of biomolecules that might __ are not formed.
- transient (lasting only for a short time)
- paralyze cellular activities
101
a __ occurs between metabolites and macromolecules, hormones and receptors, and all the other participants instrumental to life processes. This interplay is initiated upon __ and ultimately culminates in unique physiological activities.
- dynamic interplay
- specific recognition between complementary molecules
102
Biological function is achieved through
mechanisms based on __ and __
- structural complementarity
- weak chemical interactions
103
the formation of supramolecular complexes occurs because of __ and __ between their various macromolecular components, as governed by the weak forces formed between them. If a sufficient number of __ can be formed, as in macromolecules complementary in structure to one another, __ assemble spontaneously.
- recognition; interaction
- weak bonds
- larger structures
104
The tendency for nonpolar molecules and parts of molecules to come together through hydro-phobic interactions also promotes the formation of supramolecular assemblies. Very complex subcellular structures are actually spontaneously formed in an assembly process that is driven by __.
- weak forces accumulated through structural complementarity
105
Because biomolecular interactions are governed by __, living systems are __. Biological macromolecules are functionally active only within a narrow range of environmental conditions, such as temperature, ionic strength, and relative acidity. Extremes of these conditions disrupt the __ essential to maintaining the intricate structure of macromolecules. The loss of structural order in these complex macromolecules, so-called __, is accompanied by __.
- weak forces
- restricted to a narrow range of physical conditions
- weak forces
- denaturation; loss of function
106
cells cannot tolerate reactions in which large amounts of energy are released, nor can they generate a large energy burst to drive energy-requiring processes. Instead, such transformations take place via a __ whose overall effect achieves dramatic energy changes, even though any given reaction in the series proceeds with only __
- sequential series of chemical reactions
- modest input or release of energy
107
the ordered reaction pathways by which cellular chemistry proceeds and biological energy transformations are accomplished.
cellular metabolism
108
the common ways chemists accelerate reactions are not available to cells; the temperature cannot be raised, acid or base cannot be added, the pressure cannot be elevated, and concentrations cannot be dramatically increased. Instead, biomolecular catalysts mediate cellular reactions.
enzymes
109
accelerate the reaction rates many orders of magnitude and, by selecting the substances undergoing the reaction, determine the specific reaction that takes place. Virtually every metabolic reaction is catalyzed by these
enzymes
110
The need for metabolic regulation is obvious. This metabolic regulation is achieved through __ so that the rates of __ are appropriate to __.
- controls on enzyme activity
- cellular reactions; cellular requirements
111
Enzymes have no influence over __ in their reactions. Enzymes only influence __. Thus, cells are systems that take in food, release waste, and carry out complex degradative and biosynthetic reactions essential to their survival while operating under conditions of essentially __ and __ and maintaining a __ with no outwardly apparent changes.
- energy changes (the thermodynamic component)
- reaction rates
- constant temperature: pressure
- constant internal environment (homeostasis)
112
Cells are __ exchanging matter and energy with their environment and functioning as highly regulated isothermal chemical engines.
open thermodynamic systems
113
Individual organisms have life spans ranging from a day or less to a century or more, but the phenomena that characterize and define living systems have durations ranging over __, from __ (electron transfer reactions, photoexcitation in photosynthesis) to __ (the period of evolution, spanning from the first appearance of organisms on the earth more than 3 billion years ago to today)
- 33 orders of magnitude
- 10^-15 sec
- 10^18 sec
114
Because proteins are the agents of biological function, phenomena involving weak interactions and proteins dominate the __ (in 33 orders of magnitude). As time increases, more stable interactions (__) and phenomena involving the agents of genetic information (the nucleic acids) come into play
- shorter times
- covalent bonds
115
All living cells fall into one of three broad categories
Archaea, Bacteria, and Eukarya
116
__ is essential for fertilization and may contribute to the membrane block to polyspermy. __ is displayed on the surface of acrosome-reacted sperm and interacts with __ on the surface of ovulated eggs. Following fertilization, __ is rapidly shed from the egg membrane and redistributed as vesicles, which may bind and rapidly neutralize subsequent incoming acrosome-reacted sperm, thereby reducing the possibility of creating nonviable polyploid embryos.
- Juno–Izumo binding
- Izumo
- Juno
- Juno
117
Despite great diversity in form and function, cells and organisms share much biochemistry in common. This commonality and diversity have been substantiated by the results of __ , the determination of the complete nucleotide sequence within the DNA of an organism.
whole genome sequencing
118
A unit of hereditary information, physically
defined by a specific sequence of nucleotides in DNA; in molecular terms, a gene is a nucleotide sequence that encodes a protein or RNA product.
genes
119
How many genes are needed for cellular life? Any minimum gene set must encode all the information necessary for cellular metabolism, including the vital functions essential to reproduction. The simplest cell must show at least:
(1) some degree of metabolism and energy production;
(2) genetic replication based on a template molecule that encodes information (DNA or RNA?); and
(3) formation and maintenance of a cell boundary (membrane).
120
The __ form a widely spread group. Certain of them are pathogenic to humans. The __, about which we know less, were first discovered growing in unusual environments where other cells cannot survive. Archaea include the __ (heat- and acid-loving bacteria) of hot springs, the __ (salt-loving bacteria) of salt lakes and ponds, and the __ (bacteria that generate methane from CO2 and H2).
- bacteria
- archaea
- thermoacidophiles
- halophiles
- methanogens
121
__ have only a single membrane, the plasma membrane or cell membrane. Because they have no other membranes, they contain no nucleus or organelles.
Prokaryotic cells
122
Prokaryotic cells possess a distinct nuclear area called the __ where a single circular chromosome is localized.
nucleoid
123
In __, flat, sheetlike membranous structures called lamellae are formed from cell membrane infoldings. These __ are the sites of photosynthetic activity, but they are not contained within __, the organelles of photosynthesis found in higher plant cells. Some bacteria have __, single, long filaments used for motility
- cyanobacteria
- lamellae
- plastids
- flagella
124
a rigid framework of polysaccharides cross-linked by short peptide chains. Some bacteria possess a lipopolysaccharide- and protein-rich outer membrane
cell wall: peptidoglycan
125
Mechanical support, shape, and protection against swelling in hypotonic media. The cell wall is a porous nonselective barrier that allows most small molecules to pass.
cell wall
126
The cell membrane is composed of about __ and __. The __ form a bilayer that is a continuous nonpolar hydrophobic phase in which the proteins are embedded.
- 45% lipid
- 55% protein
- lipids
127
s a highly selective permeability barrier that controls the entry of most substances into the cell. Important enzymes in the generation of cellular energy are located in the membrane.
cell membrane
128
__ the sites of protein synthesis. The __ binds to ribosomes, and the __ nucleotide sequence specifies the protein that is synthesized.
- ribosomes
- rRNA
- mRNA
129
When needed as a metabolic fuel, the monomeric units of the polymer are liberated and degraded by energy-yielding pathways in the cell.
storage granules
130
the site of intermediary metabolism, the interconnecting sets of chemical reactions by which cells generate energy and form the precursors necessary for the biosynthesis of macromolecules essential to cell growth and function
cytosol
131
- supramolecular complexes of nucleic acid, either DNA or RNA, encapsulated in a protein coat and, in some instances, surrounded by a membrane envelope
- acellular, but they act as cellular parasites in order to reproduce
virus
132
The bits of __ in viruses are, in reality, mobile elements of genetic information. The __ serves to protect the nucleic acid and allows it to gain entry to the cells that are its specific hosts.
- nucleic acid
- protein coat
133
Viruses infecting bacteria are called __
bacteriophages (“bacteria eaters”);
134
The host metabolic functions are subjugated to the synthesis of viral nucleic acid and proteins. Mature virus particles arise by encapsulating the nucleic acid within a protein coat called the __. Thus, viruses are supramolecular assemblies that act as parasites of cells
capsid
135
Often, viruses cause disintegration of the cells that they have infected, a process referred to as cell __
lysis
136
It is their cytolytic properties that are the basis of viral disease. In certain circumstances, the viral genetic elements may integrate into the host chromosome and become quiescent. Such a state is termed __. Typically, damage to the host cell activates the replicative capacities of the quiescent viral nucleic acid, leading to viral propagation and release.
lysogeny
137
- This complex coating is cell specific, serves in cell–cell recognition and communication, creates cell adhesion, and provides a protective outer layer.
- The surfaces of animal cells are covered with a flexible and sticky layer of complex carbohydrates, proteins, and lipids
extracellular matrix
138
a labyrinthine organelle where both membrane proteins and lipids are synthesized. Proteins made by the ribosomes of the __ pass through the __ membrane into the cisternae and can be
transported via the Golgi to the periphery of the cell. Other ribosomes unassociated with the __ carry on protein synthesis in the cytosol. The nuclear membrane, ER, Golgi, and additional vesicles are all part of a continuous __.
- Endoplasmic reticulum
- rough ER
- ER
- ER
- endomembrane system
139
Involved in the packaging and processing of macromolecules for secretion and for delivery to other cellular compartments.
golgi apparatus
140
function in intracellular digestion of materials
entering the cell via phagocytosis or pinocytosis. They also function in the controlled degradation of cellular components. Their internal pH is about 5, and the hydrolytic enzymes they
contain work best at this pH
lysosomes
141
act to oxidize certain nutrients, such as amino
acids. In doing so, they form potentially toxic hydrogen peroxide, H2O2, and then decompose it to H2O and O2 by way of the peroxide-cleaving enzyme catalase.
peroxisome
142
determines the shape of the cell and gives it
its ability to move. It also mediates the internal movements that occur in the cytoplasm, such as the migration of organelles and mitotic movements of chromosomes. The propulsion instruments of cells—cilia and flagella—are constructed of microtubules.
cytoskeleton
143
function in the transport and storage of nutrients and cellular waste products. By accumulating water, the vacuole allows the plant cell to grow dramatically in size with no increase in cytoplasmic volume
vacuole
