Biology 1 - vocabulary Flashcards
1
Q
Evolution
A
Descent with modification; the process by which species accumulate differences from their ancestors as they adapt to different environments over time; also defined as a change in the genetic composition of a population from generation to generation.
2
Q
Hypothesis
A
A testable explanation for a set of observations based on the available data and guided by inductive reasoning. A hypothesis is narrower in scope than a theory.
3
Q
Theory
A
An explanation that is broader in scope than a hypothesis, generates new hypotheses, and is supported by a large body of evidence.
4
Q
Isotope
A
One of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass.
5
Q
Valence electron
A
An electron in the outermost electron shell.
6
Q
Ionic bond
A
A chemical bond resulting from the attraction between oppositely charged ions.
7
Q
Nonpolar covalent bond
A
A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.
8
Q
Polar covalent bond
A
A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.
9
Q
Element
A
Any substance that cannot be broken down to any other substance by chemical reactions.
10
Q
Compound
A
A substance consisting of two or more different elements combined in a fixed ratio.
11
Q
Molecule
A
Two or more atoms held together by covalent bonds.
12
Q
Polar molecule
A
A molecule (such as water) with an uneven distribution of charges in different regions of the molecule.
13
Q
Surface tension
A
A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules.
14
Q
Specific heat
A
The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1 degree C.
15
Q
Buffer
A
A solution that contains a weak acid and its corresponding base. A buffer minimizes changes in pH when acids or bases are added to the solution.
16
Q
Functional group
A
A specific configuration of atoms commonly attached to the carbon skeletons of organic molecules and involved in chemical reactions.
17
Q
ATP
A
(adenosine triphosphate)
An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
18
Q
Monomer
A
The subunit that serves as the building block of a polymer.
19
Q
Polymer
A
A long molecule consisting of many similar or identical monomers linked together by covalent bonds.
20
Q
Enzyme
A
A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most enzymes are proteins.
21
Q
Gene
A
A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).
22
Q
Genomics
A
The systematic study of whole sets of genes (or other DNA) and their interactions within a species, as well as genome comparisons between species.
23
Q
Proteomics
A
The systematic study of sets of proteins and their properties, including their abundance, chemical modifications, and interactions.
24
Q
Dehydration reaction
A
A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule.
25
Condensation reaction
A type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water.
26
Cytosol
The semifluid portion of the cytoplasm.
27
Cytoplasm
The contents of the cell bounded by the plasma membrane; in eukaryotes, the portion exclusive of the nucleus.
28
Phagocytosis
A type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells).
29
Plasmadesmata
An open channel through the cell wall that connects the cytoplasm of adjacent plant cells, allowing water, small solutes, and some larger molecules to pass between the cells.
30
Chromatin
The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.
31
Chromosome
A cellular structure consisting of one DNA molecule and associated protein molecules. A duplicated chromosome has two DNA molecules. (In some contexts, such as genome sequencing, the term may refer to the DNA alone.)
32
Selective permeability
A property of biological membranes that allows them to regulate the passage of substances across them.
33
Amphipathic
Having both a hydrophilic region and a hydrophobic region.
34
Aquaporins
A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane.
35
Concentration gradient
A region along which the density of a chemical substance increases or decreases.
36
Osmoregulation
Regulation of solute concentrations and water balance by a cell or organism.
37
Hypotonic
Referring to a solution that, when surrounding a cell, will cause the cell to take up water.
38
Hypertonic
Referring to a solution that, when surrounding a cell, will cause the cell to lose water.
39
Isotonic
Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell.
40
1st law of thermodynamics
The principle of conservation of energy: Energy can be transferred and transformed, but it cannot be created or destroyed.
41
Catalyst
A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.
42
Activation energy
The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation.
43
Active site
The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.
44
Cofactor
Any nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely and reversibly, along with the substrate, during catalysis.
45
Coenzyme
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions.
46
Enzyme-substrate complex
A temporary complex formed when an enzyme binds to its substrate molecule(s).
47
Substrate
The reactant on which an enzyme works.
48
REDOX reaction
A chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another; short for reduction-oxidation reaction.
49
Purine
One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. Adenine (A) and guanine (G) are purines.
50
Catabolic pathway
A metabolic pathway that releases energy by breaking down complex molecules to simpler molecules.
51
Fermentation
A catabolic process that makes a limited amount of ATP from glucose (or other organic molecules) without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid.
52
Metabolic pathway
A series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catabolic pathway).
53
Metabolism
The totality of an organism’s chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.
54
Anabolic pathway
A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules.
55
Acetyl CoA
Acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a two-carbon fragment of pyruvate attached to a coenzyme.
56
Cellular respiration
The catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules and use an electron transport chain for the production of ATP.
57
Citric acid cycle
Same as the Krebs cycle.
A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; together with pyruvate oxidation, the second major stage in cellular respiration.
58
Glycolysis
A series of reactions that ultimately splits glucose into pyruvate. Glycolysis occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration.
59
NAD+
The oxidized form of nicotinamide adenine dinucleotide, a coenzyme that can accept electrons, becoming NADH. NADH temporarily stores electrons during cellular respiration.
60
NADH
The reduced form of nicotinamide adenine dinucleotide that temporarily stores electrons during cellular respiration. NADH acts as an electron donor to the electron transport chain.
61
Oxidative phosphorylation
The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration.
62
Oxidizing agent
The electron acceptor in a redox reaction.
63
Oxidation
The complete or partial loss of electrons from a substance involved in a redox reaction
64
Alcohol fermentation
Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD-plus and releasing carbon dioxide.
65
Lactid acid fermentation
Glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD plus with no release of carbon dioxide.
66
Pyruvate oxidation
The conversion of pyruvate into acetyl-CoA by the enzyme complex pyruvate dehydrogenase complex.
67
Krebs cycle
Same as the citric acid cycle.
A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; together with pyruvate oxidation, the second major stage in cellular respiration.
68
Electron transport chain (ETC)
A sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP.
69
Chemiosmosis
An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Under aerobic conditions, most ATP synthesis in cells occurs by chemiosmosis.
70
Heterotroph
An organism that obtains organic food molecules by eating other organisms or substances derived from them.
71
Autotroph
An organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from oxidation of inorganic substances to make organic molecules from inorganic ones.
72
Photosystem
A light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes. There are two types of photosystems, I and II; they absorb light best at different wavelengths.
73
Thylakoid
A flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular “machinery” used to convert light energy to chemical energy.
74
Light reaction
The first of two major stages in photosynthesis (preceding the Calvin cycle). These reactions, which occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.
75
Photophosphorylation
The process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certain prokaryotes during the light reactions of photosynthesis.
76
Stroma
The dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA; involved in the synthesis of organic molecules from carbon dioxide and water.
77
Calvin cycle
The second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric carbon dioxide and reduction of the fixed carbon into carbohydrate.
78
Chlorophyll
A green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes. "Chlorophyll a" participates directly in the light reactions, which convert solar energy to chemical energy.
79
Chlorophyll a
A photosynthetic pigment that participates directly in the light reactions, which convert solar energy to chemical energy.
80
Chlorophyll b
An accessory photosynthetic pigment that transfers energy to chlorophyll a.
81
Chloroplast
An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
82
Cholesterol
A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as many hormones.
83
ATP synthase
A complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP. ATP synthases are found in the inner mitochondrial membranes of eukaryotic cells and in the plasma membranes of prokaryotes.
84
Carotenoid
An accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis.
85
Glyceraldehyde 3-phosphate (G3P)
A three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis.
86
Hormone
In multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the organism, changing the target cells’ functioning.
87
Ligand
A molecule that binds specifically to another molecule, usually a larger one.
88
Second(ary) messenger
A molecule that relays messages in a cell from a receptor to a target where an action within the cell takes place.
89
Cyclic AMP (cAMP)
Cyclic adenosine monophosphate, named because of its ring structure, is a common chemical signal that has a diversity of roles, including as a second messenger in many eukaryotic cells, and as a regulator of some bacterial operons.
90
Paracrine
Referring to a secreted molecule that acts on a neighboring cell.
91
Synapse
The junction where a neuron communicates with another cell across a narrow gap via a neurotransmitter or an electrical coupling.
92
Endocrine system
In animals, the internal system of communication involving hormones, the ductless glands that secrete hormones, and the molecular receptors on or in target cells that respond to hormones; functions in concert with the nervous system to effect internal regulation and maintain homeostasis.
93
Signal reception
In cellular communication, the first step of a signaling pathway in which a signaling molecule is detected by a receptor molecule on or in the cell.
94
Signal reception
The linkage of a mechanical, chemical, or electromagnetic stimulus to a specific cellular response.
95
(Signal) response
In cellular communication, the change in a specific cellular activity brought about by a transduced signal from outside the cell.
96
Genome
The genetic material of an organism or virus; the complete complement of an organism’s or virus’s genes along with its noncoding nucleic acid sequences.
97
Karyotype
A display of the chromosome pairs of a cell arranged by size and shape.
98
Somatic cell
Any cell in a multicellular organism except a sperm or egg or their precursors.
99
Gamete
A haploid reproductive cell, such as an egg or sperm, that is formed by meiosis or is the descendant of cells formed by meiosis. Gametes unite during sexual reproduction to produce a diploid zygote.
100
Cytokinesis
The division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II.
101
Mitosis
A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei.
102
Mitotic (M) phase
The phase of the cell cycle that includes mitosis and cytokinesis.
103
Mitotic spindle
An assemblage of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis.
104
Meiosis
A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.
105
Meiosis I
The first division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.
106
Meiosis II
The second division of a two-stage process of cell division in sexually reproducing organisms that results in cells with half the number of chromosome sets as the original cell.
107
Nondisjunction
An error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other.
108
Linked genes
Genes located close enough together on a chromosome that they tend to be inherited together.
109
Linkage map
A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes.
110
Locus
A specific place along the length of a chromosome where a given gene is located.
111
Zygote
The diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg.
112
Synapsis
The pairing and physical connection of one duplicated chromosome to its homolog during prophase I of meiosis.
113
Recombinant chromosomes
A chromosome created when crossing over combines DNA from two parents into a single chromosome.
114
Homologous chromosomes
A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism’s male parent, the other from the female parent. Also called a homologous pair.
115
Sister chromatids
Two copies of a duplicated chromosome attached to each other by proteins at the centromere and, sometimes, along the arms. While joined, two sister chromatids make up one chromosome. Chromatids are eventually separated during mitosis or meiosis II.
116
Alleles
Any of the alternative versions of a gene that may produce distinguishable phenotypic effects.
117
Dominant allele
An allele that is fully expressed in the phenotype of a heterozygote.
118
Recessive allele
An allele whose phenotypic effect is not observed in a heterozygote.
119
Testcross
Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring reveals the unknown genotype.
120
Dihybrid
An organism that is heterozygous with respect to two genes of interest. All the offspring from a cross between parents doubly homozygous for different alleles are dihybrids. For example, parents of genotypes AABB and aabb produce a dihybrid of genotype AaBb.
121
Homozygous
Having two identical alleles for a given gene.
122
Incomplete dominance
The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele.
123
Monohybrid
An organism that is heterozygous with respect to a single gene of interest. All the offspring from a cross between parents homozygous for different alleles are monohybrids. For example, parents of genotypes AA and aa produce a monohybrid of genotype Aa.
124
P generation
The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived in studies of inheritance. (P stands for parental.)
125
Codominance
The situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways.
126
Complete dominance
The situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.
127
Dihybrid cross
A cross between two organisms that are each heterozygous for both of the characters being followed (or the self-pollination of a plant that is heterozygous for both characters).
128
F1 generation
The first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross.
129
Heterozygous
Having two different alleles for a given gene.
130
Genotype
The genetic makeup, or set of alleles, of an organism.
131
Phenotype
The observable physical and physiological traits of an organism, which are determined by its genetic makeup.
132
Law of segregation
Mendel’s first law, stating that the two alleles in a pair segregate (separate from each other) into different gametes during gamete formation.
133
Law of independent assortment
Mendel’s second law, stating that each pair of alleles segregates, or assorts, independently of each other pair during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes.
134
Wild type
The phenotype most commonly observed in natural populations; also refers to the individual with that phenotype.
135
X-linked gene
A gene located on the X chromosome; such genes show a distinctive pattern of inheritance.
136
Map unit
A unit of measurement of the distance between genes. One map unit is equivalent to a 1 percent recombination frequency.
137
Hemophilia
A human genetic disease caused by a sex-linked recessive allele resulting in the absence of one or more blood-clotting proteins; characterized by excessive bleeding following injury
138
Genetic map
An ordered list of genetic loci (genes or other genetic markers) along a chromosome.
139
Crossing over
The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.
140
Recombinant type
An offspring whose phenotype differs from that of the true-breeding P generation parents; also refers to the phenotype itself.
141
Semiconservative model
Type of DNA replication in which the replicated double helix consists of one old strand, derived from the parental molecule, and one newly made strand.
142
DNA replication
The process by which a DNA molecule is copied; also called DNA synthesis.
143
Primer
A short polynucleotide with a free 3′ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication.
144
Leading strand
The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5' to 3' direction.
145
Okazaki fragment
A short segment of DNA synthesized away from the replication fork on a template strand during DNA replication. Many such segments are joined together to make up the lagging strand of newly synthesized DNA.
146
Lagging strand
A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.
147
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3′ end of one DNA fragment (such as an Okazaki fragment) to the 5′ end of another DNA fragment (such as a growing DNA chain).
148
Helicase
An enzyme that untwists the double helix of DNA at replication forks, separating the two strands and making them available as template strands.
149
Nucleosome
The basic, bead-like unit of DNA packing in eukaryotes, consisting of a segment of DNA wound around a protein core composed of two copies of each of four types of histone.
150
Protein
A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.
151
Lipid
Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water.
152
Carbohydrate
A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides).
153
Organelle
Any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells.
154
Mass number
The total number of protons and neutrons in an atom’s nucleus.
155
Neutron
A subatomic particle having no electrical charge (electrically neutral), with a mass of about 1.7 times 10 to the negative 24 g, found in the nucleus of an atom.
156
Electron
A subatomic particle with a single negative electrical charge and a mass about 1 two-thousandths that of a neutron or proton. One or more electrons move around the nucleus of an atom.
157
Electron shell
An energy level of electrons at a characteristic average distance from the nucleus of an atom.
158
Nuclear envelope
In a eukaryotic cell, the double membrane that surrounds the nucleus, perforated with pores that regulate traffic with the cytoplasm. The outer membrane is continuous with the endoplasmic reticulum.
159
Nucleolus
A specialized structure in the nucleus, consisting of chromosomal regions containing ribosomal RNA (rRNA) genes along with ribosomal proteins imported from the cytoplasm; site of rRNA synthesis and ribosomal subunit assembly.
160
Nucleoid
A non-membrane-enclosed region in a prokaryotic cell where its chromosome is located.
161
(Cell) nucleus
The organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes, made up of chromatin.
162
Proton
A subatomic particle with a single positive electrical charge, with a mass of about 1.7 times 10 to the negative 24 g, found in the nucleus of an atom.
163
Endomembrane system
The collection of membranes inside and surrounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the plasma membrane, the nuclear envelope, the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, and vacuoles.
164
Golgi apparatus
An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates.
165
Flagella
A long cellular appendage specialized for locomotion. Like motile cilia, eukaryotic flagella have a core with nine outer doublet microtubules and two inner single microtubules (the “9 plus 2” arrangement) ensheathed in an extension of the plasma membrane. Prokaryotic flagella have a different structure.
166
Intermediate filament
A component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments.
167
Microtubule
A hollow rod composed of tubulin proteins that makes up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella.
168
Cytoskeleton
A network of microtubules, microfilaments, and intermediate filaments that extend throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions.
169
Microfilaments
A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction; also called an actin filament.
170
Central vacuole
In a mature plant cell, a large membranous sac with diverse roles in growth, storage, and sequestration of toxic substances.
171
Food vacuole
A membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell.
172
Vacuole
A membrane-bounded vesicle whose specialized function varies in different kinds of cells.
173
Endoplasmic reticulum (ER)
An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions.
174
Rough ER
That portion of the endoplasmic reticulum with ribosomes attached.
175
Smooth ER
That portion of the endoplasmic reticulum that is free of ribosomes.
176
Centriole
A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a “9 plus 0” pattern. A centrosome has a pair of centrioles.
177
Endosymbiont theory
The theory that mitochondria and plastids originated as prokaryotic cells engulfed by a host cell. The engulfed cell and its host cell then evolved into a single organism; A relationship between two species in which one organism lives inside the cell or cells of another organism.
178
Mitochondria
An organelle in eukaryotic cells that serves as the site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP.
179
Lysosome
A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.
180
Ribosome
A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus.
181
Plasma membrane
The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell’s chemical composition.
182
Microvilli
One of many fine, finger-like projections of the epithelial cells in the lumen of the small intestine that increase its surface area.
183
Cell wall
A protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists. Polysaccharides such as cellulose (in plants and some protists), chitin (in fungi), and peptidoglycan (in bacteria) are important structural components of cell walls.
184
Cell plate
A membrane-bounded, flattened sac located at the midline of a dividing plant cell, inside which the new cell wall forms during cytokinesis.
185
Peroxisome
An organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen, producing and then degrading hydrogen peroxide.
186
Exocytosis
The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.
187
Endocytosis
Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.
188
Tight junction
A type of intercellular junction
between animal cells that prevents the leakage of material through the space between cells.
189
Gap junction
A type of intercellular junction in
animal cells, consisting of proteins surrounding a pore that allows the passage of materials between cells.
190
Desmosome
A type of intercellular junction in
animal cells that functions as a rivet, fastening cells together.
191
Extracellular matrix (ECM)
The meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides, and proteoglycans synthesized and secreted by cells.
192
Hydroxyl group
–OH
Compound name: Alcohol
Example: Ethanol
193
Carbonyl group
>C=O
Compound name: Ketone (inside) or Aldehyde (on end)
Example: Acetone; Propanal
194
Carboxyl group
–COOH
Compound name: Carboxylic/organic acid
Example: Acetic acid
195
Amino group
–NH2
Compound name: Amine
Example: Glycine
196
Sulfhydryl group
–SH
Compound name: Thiol
Example: Cysteine
197
Phosphate group
–OPO3^(2-)
Compound name: Organic phosphate
Example: Glycerol phosphate
198
Methyl group
–CH3
Compound name: Methylated compound
Example: 5-Methylcytosine
199
Deoxyribose
The sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides.
200
Cilia
A short hair-like membrane protrusion from many types of eukaryotic cell.
