Biology MCAT Flashcards
1
Q
Action Potential
A
A sharp change in the membrane potential of neurons or muscle cells caused by a change in the selective permeability of K+ and Na+ using ion-gated channels. Action potentials are all-or-none events
2
Q
Activation Energy
A
The difference in potential energy between the inital state (reactants) and the transition state. Reactants must overcome the activation energy in order to undergo the reaction
3
Q
Active Immunity
A
Immunity resultin from the produciton of antibodies during a previous infection or a vaccination
4
Q
Active Transport
A
Movement of particles from a region of lower concentration to a region of higher concentration utilizing energy
5
Q
ADH
A
Antidiuretic hormone (ADH), also known as vasopressin, acts on the collecting duct to increase water reabsorption. ADH is produced by the hypothalamus and stored in the posterior pituitary
6
Q
Adrenal Cortex
A
Synthesizes and releases corticosteroids (including glucocorticoids and mineralcorticoids) when stimulated by adrenocroticotropic hormone (ACTH)
7
Q
Adrenal Meduall
A
Synthesizes and releases epinephrine and norepinephrine, which stimulate an increase in the metabolic rate and blood glucose levels
8
Q
Adrenocorticotropic Hormone
A
Synthesized and released by the anterior pituitary, ACTH stimulates the adrenal cortex to synthesize and secrete glucocoritcoids. ACTH is regulated by corticotrophin-releasing hormone (CRF) which is released by the hypothalamus
9
Q
Afferent Neurons
A
Neurons that carry information to the central nervous system
10
Q
Aldosterone
A
A steroid hormon produced in the adrenal cortex that is responsible for reabsorpiton of sodium and water and the excretion of potassium
11
Q
Allantosis
A
The embryonic membrane that contains the growing embryo’s waster products
12
Q
Allelels
A
Genes coding for alternative forms of a given trait
13
Q
Allosteric Enzyme
A
An enzyme with two or more active sites that can exist in more than one conformation, usually an active form or an inactive form
14
Q
Amino Acid Derived Hormones
A
Hormones that are synthesized from amino acids. Some amino acid derived hormones act via secondary messengers, while others act in a fashion similar to steroid hormones
15
Q
Amnion
A
The innermost extraembryonic membrane that contains amniotic fluid in which the growing fetus is suspended
16
Q
Analogous Structures
A
Similar structures that share a common funciton but not similar origins
17
Q
Anterior Pituitary
A
Synthesizes and releases many vital hormones, including follicle-stimulating hormone, luteinizing hormone, adrenocorticotropic hormone, thyroid-stimulating hormone, prolactin, endorphins, and growth hormone (“FLATPED”). The anterior pituitary is under the hormonal control of the hypothalamus
18
Q
Apoenzyme
A
An enzyme that requirees cofactors in order to become catalytically active
19
Q
Appendicular Skeleton
A
The bones of the pelvis, the pectoral girdles, and the limbs
20
Q
Arteries
A
Vessels that carry blood away from the heart. These vessels are muscular and do not have valvves
21
Q
Ascending Limb of the Loop of Henle
A
Portion of the nephron not permeable to water. As the filtrate flows up the ascending limb through decreasing concentration of the intersitital fluid, Na+ is actively pumped out of the filtrate, decreasing filtrate concentration
22
Q
Atria
A
The two thin-walle dupper chambers of the heart. The right atrium receives deoxygenated blood from the vena cava, while the left atrium receives oxygenated blood from the pulmonary vein
23
Q
Atrioventricular Valves
A
Valves located between the atria and the centricles (tricuspid valve and mitral valve)
24
Q
Axial skeleton
A
The skull, vertebral column, and bones of the chest
25
Axon Hillock
The portion of the neuron that connects the cell body (soma) to the axon. The impulses the neuron receives from all the dendrites are summed up at the axon hillock to determine whether an action potential will be initiated
26
Bacteriophages
Viruses that can only infect bacteria
27
Bile
An alkaline fluid synthesized in the liver, stored in the gall bladder, and released into the duodenum. Bile aids in the emulsification, digestion, and absorption of fats
28
Binary Fission
Metod of asexual reproduction by which prokaryotes divide. The ciruclar DNA molecule replicates and then moves to opposite sides of the cell. The cell then divides into two daughter cells of equal size
29
Blastulation
The process by which a morula develops into a blastula with a fluid-filled cavity called a blastocoel
30
Blood Antigens
Proteins found on the erythrocyte cell surface. Three antigens used to differentiate blood groups are A, B, and Rh. If a host organism is transfused with erythrocytes containing antigens that the host doe not have, an immune response will be triggered, such as in the case of erythroblastosis fetalis
31
Bohr Effect
Increasing teh concentration of H+ and CO2 reduces hemoglobin's affinity for oxygen, allowing for the transfer of oxygen to cells that require it most
32
Calcitonin
Hormone synthesized and released by the thyroid gland that decreases plasma Ca2+ concentration
33
Capillaries
Blood vessels composed of a single layer of endothelial cells, facilitating exchange between the blood and interstitial fluid
34
Carbonic Anhydrase
Enzyme that catalyzes the conversion of carbonic acid to carbon dioxide and water as well as the formation of carbonic acid from carbon dioxide and water
35
Cardiac Output
The total volume of blood that left ventricle pumps into circulation per minute. The cardiac output can be increased by increasing either the heart rate or the stroke volume
36
Cardiac Sphincter
A valve between the esophagus and the stomach the prevents the content of the stomach from going back up through the esophagus
37
Cartilage
A firm, elastic, translucent connective tissue consisting of collagenous fibers embedded in chondrin. Produced by cells called chondrocytes. Cartilage is the principal component of embryonic skeletons and can harden and calcify into bone
38
Central Nervous System
The central nervous system consists of the brain and the spinal cord
39
Centrosome
The protion of the cell containing the centrioles
40
Chemical Digestion
Enzymatic breakdown of large molecules into smaller molecules
41
Chloroplast
The site of photosynthesis in plants. The chloroplast contains chlorophyll, is semiautonomous, and has two cell membrane
42
Cholecytoskinin
CCK is a hormone that is secreted by the duodenum in response to the presence of chyme. CCK stimulates the release of bile and pancreatic enzymes into the small intestine
43
Chorion
The outermost extraembryonic membrane; contributes to the formation of the placenta
44
Chromatin
Chromosomes in their uncoiled active states. Chromatin is not visibile under a light microscope
45
Chyme
Combination of partially digested food and acid that forms in the stomach
46
Ciliary Muscles
Muscular tissue attached to the lens that is used to control the lens's shape
47
Citric Acid Cycle
The cycle begins when the two-carbon acetyl group from acetyl CoA combines with oxaloacetate to form citric acid. This product then proceeds througha series of reactions that result in the regeneration of oxaloacetate and the production of three NADH, one FADH2, and one GTP
48
Codon
Nonoverlapping group of three bases that code for a particular amino acid
49
Collecting Duct
Portion of te nephron permeable to water and ions. As the filtrate flows down the collecting duct through the increasing concentration of the intersitial fluid, the filtrate is concentrated further. The degree of water reabsorption in the collecting duct is controlled by the action of the hormones ADH and aldosterone
50
Compact bone
Much more dense than spongy bone, compact bone consists of havrsian systems (osteons)
51
Competitive inhibitor
Molecule that inhibits the activity of an enzyme by directly binding to the active site of the enzyme. This type of inhibition is usuallly reversible and can be overcome by increasing the substrate concentration
52
Cornea
Transparent coverin in front of the eye that refracts light and helps keep the eye in focus
53
Corona Radiata
Outer layer of cells surrounding the oocyte. These cells are secreted by follicle cells
54
Coronary Arteries
Blood vessels that supply the heart with oxygenated blood
55
Coronary Veins
Blood vessels that ransport deoxygenated blood from the heart toward the right atrium
56
Corpus Callosum
The crpus callosum connects the brain's left hemisphere with its right hemisphere and correlates their activities
57
Corpus Luteum
Tissue that forms from the collapsed ovarian follicle. Produces and secretes progesteron and estrogen
58
Crossing Over
The exchange of genetic material between chromosomes (usually homologous chromosomes) that occurs during prophase I of meiosis. Crossing over aids in evolution and genetic diversity by unlinking linked genes
59
Cytoskeleton
The cytoskeleton gives the cell mechanical support, maintains shape, and functions in motility. It is composed of microtubules, micorfilaments, and intermediate filaments
60
Dendrite
As extension of the neuron that transmits impulses toward the cell body
61
Depolarization
A porcess that occurs when the voltage-gated Na+ channels open, allowing Na+ to rush into the cell and depolarize it
62
Dermis
The layer of skin beneath the epidermins that is subdivided into the papillary layer and the reticular layer. It contains the sweat glands, sense organs, blood vessels, and the bulbs of hair follicles, and is derived from the mesoderm
63
Descending Limb of the Loop of Henle
Portion of the nephron permeable only to water. The filtrate becomes more concentrated (loses water) as it travels through the descending limb due to the increasing concentration of interstitial fluid
64
Determinate Cleavage
A cleavage whose future differentiation pathways are determined
65
Diastole
The stage of the heart cycle in which the heart muscle relaxes and collects blood into its four chambers
66
Dihybrid Cross
A cross between two organisms where two distinct traits are being studied
67
Diploid
Diploid cells have two copis of each chromosome, usually one from the mother and one from the father. Eukaryotic somatic cells are diploid
68
Directional Selection
Type of natural selection where one extreme pheotype is favored over the normal phenotype and other extremem phenotypes
69
Disjunction
The separation of homologous chromosomes during anaphase I of meiosis
70
Disruptive Selection
Type of natural selection where both phenotypic extremes are favored over the normal phenotype
71
Dizygotic Twins
Results when two ova are fertilized by two different sperm. Since the two resulting embryos develop form distinct zygotes they do not have identical alleles.
72
DNA ligase
Enzyme that covalently links the Okazaki fragments together
73
DNA polymerase
An enzyme that polymerizes a complementary DNA strand in the 5' to 3' direction using a template DNA strand. A primer is necessary for DNA polymerase to initiate polymerization
74
Ductus Arteriosus
A shunt that connects the pulmonary artery to the aorta in order to bypass the fetal lung
75
Ductus venosus
A shunt that connects the umbilical vein to the inferior vena cava in order to bypass the fetal liver
76
Ectoderm
The outermost of teh three primary germ layers, which gives rise to the skin, and the nervous system
77
Efferent Neurons
neurons that carry information from the central nervous system to other parts of the body
78
Electron Transport Chain
A chain of cytochromes and other proteins in the inner membrane of teh mitochondria that transfers electrons form NADH and FADH2 to oxygen. The energy released from teh series of oxidations is used to create a proton gradient, which ATP synthase then uses to synthesize ATP
79
Endocrine Glands
Glands that synthesize and secrete hormones into the circulatory system. Examples include the hypothalamus, pituitary gland, pineal gland, thymus, pancrease, testes, ovaries, adrenal glands, thyroid gland, and parathyrodi glands
80
Endoderm
The innermost of the three primary germ layers, which gives rise to the linings of the digestive and respiratory tracts, and to parts of the liver, pancrease, thyroid, and bladder
81
Endometrium
The mucosal lining of the uterus where the embryo implants. Progesterone is necessary for the maintenance of the endometrium during pregnancy
82
Endorphins
Synthesized and released by the anterior pituitary, endorphins inhibit the perception of pain
83
Energy Carriers (NAD+, NADP+, FAD)
Molecules involved in cell respiration that serve as energy stores, releasing eneryg when oxidized to NAD+, NADP+, and FAD
84
Enzymes
Protein catalysts that accelerate reactions by reducing the activation energy without being consumed or altered by the reaction. Note the enzymes affect only the rate of reaction and not the amounts of products formed
85
Epidermis
The outermost layer of skin, which is composed of the following sublayers: stratum baslia, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. Serves as a protective barrier against microbial attack. Derived from the ectoderm
86
Epiglottis
A flap of cartilage that covers the glottis when swallowing food in order to prevent food particles from entereing the larynx
87
Episomes
Plasmids that have the ability to integrate into the host genome
88
Erythrocytes
The oxygen-carrying component of blood (red blood cells). These anaerobic cells, which lack organelles, are packed with hemoglobin and have a characteristic biconcave, dislike shape that facilitates gas exchange and mobility within blood vessels
89
Estrogen
Hormone syntheized and relazed by the ovaries, the ovarian folicles, the corpus luteum, and the placenta. Estrogen stimulates the development of the female reproductive tract and secondary sexual characteristics and is partly responsible for the LH spike that causes ovulation. Estrogen, along with progesterone produced by the placent during the second trimester of pregnancy, helps inhibit the oncset of a new menstrual cycle by blocking GnRH release
90
Exocrine Glands
Glands that synthesize and secrete substanes through ducts. The gall bladder is an example of an exocrine gland
91
Exons
Segments of coding eukaryotic mRNA that are spliced together and translated
92
Expiratory Reserve Volume
the amount of air that can be forcibly exhaled after a normal exhalation
93
Expressivity
The degree to which an organism expresses its genotype
94
Exteroceptor
Type of sensory receptor that monitors external signals such as light, sound, and temperature
95
Facilitated Diffusion
Passive movement of particles from a region of higher concentration to a region of lower concentration using carrier molecules. Does not require energy
96
Facultative Anaerobe
An organism that makes ATP by aerobic respiration if oxygen is present, but that can switch to fermentation when oxygen is not available
97
Fatty Acid Activation
Fats must be activated using two ATP molecules before they can be converted into acetyl CoA and enter the citric acid cycle
98
Fermentation
Process by which the cell is able to replenish the NAD+ used during glycolysis by oxidizing NADH. In this process, pyruvate (the product of glycolysis) is reduced by NADH to form ethanol (in yeast) or lactic acid (in humans)
99
Fibrin
Protein responsible for blood clotting
100
Filtrate
The material that passes from the blood vessles into Bowman's capsule
101
Follice-Stimulating Hormone
Synthesized and released by the anterior pituitary, FSH stimulates maturation of ovarian follicles in females and maturation of the seminiferous tubules and sprem production in males. FSH is regulated by estrogen and gonadotropin-releasing hormone (GnRH)
102
Follicle
A multilayered sac of cells that protects and nourishes the developing ovum
103
Foramen Ovale
A shunt that connects the right atrium to the left atrium in order to bypass the fetal lung
104
Frame Shift Mutation
Mutation in which a number of nucleotides (except multiples of three) are either deleted or inserted. Such mutations lead to a shift in the DNA reading frame and often result in the translation of nonfunctional proteins
105
Free Energy Change
The difference in potential energy between the initial state (reactants) and the final state (products). A negative delta G indicates a spontaneous reaction, whereas a postive delta G indicates a nonspontaneous reaction
106
Frequency summation
The strengthening of contraction that results when the stimuli are so frequent that muscle cannot fully relax. The stronger contraction is due to the incorporation of more muscle fibers
107
Ganglia
A group of neural cell bodies in the peripheral nervous system
108
Gastric Glands
Located in the stomach; secrete HCl and various enzymes (eg. pepsin) when stimulated by gastrin
109
Gastrulation
The process by which a single-layer blastula becomes a three-layered gastrula
110
Genotype
The genetic makeup of an individual
111
GLomerulus
Network of capillaries within Bowman's capsul that serves as the site of filtration. Blood cells and proteins are too large to be filtered, but ions, glucose, and amino acids readily pass into the filtrate
112
Glucagon
Produced and secreted by the alpha cells of the pancrease, glucagon increases blood glucose concentration by promotin gluconeogenesis and the conversion of glycogen to glucose in the liver
113
Glucocorticoids
Synthesized and released by the adrenal cortex, glucocorticoids raise blood glucose levels while decreasing protein synthesis
114
Gluconeogenesis
A process in the liver by which glucose is produced using by-products of glycolysis, lipids, or fats
115
Glycogen
The form in which carbohydrates are primarily stored in the liver. Glycogen is easily converted to glucose-6-phosphate when the body needs it.
116
Glycolysis
Through a series of enzymatic reactions in the cytoplasm, glucose is convereted into two moleucules of pyruvate. The energy released in this process is used to produce a net yield of two ATP and two NADH molecules
117
Growth Hormone
Synthesized and released by the anterior pituitary, GH stimulates bone and muscle growth as well as glucose conservation. GH is inhibited by somatostatin and stimulated by growth hormone-releasing hormone (secreted by the hypothalamus)
118
Haploid
Haploid cells have only one copy of each chromosome. Germ cells in humans are haploid
119
Helicase
An enzyme that unqinds the double helix of a DNA molecule, allowing replication to take place
120
Hemoglobin
A protein foudn in erythrocytes made up of four polypeptide chains, each containing a heme group. Hemoglobin is responsible for transporting oxygen from the alveoli to the cells
121
Hepatic Protal Vein
Carries nutrients (monosaccharides, amino acids, and small fatty acids) absorbed in the small intestine to the liver, where they are modified to enter circulation
122
Heterozygous
Organisms that contain two different alleles for the same gene on corresponding chromosome
123
Holoenzyme
An active enzyme containing all necessary cofactors
124
Homologous chromosomes
Chromosomes in a diploid cell that contain different alleles for the same trait at corresponding loci
125
Homologous Structures
Similar structures that share a common origin
126
Homozygous
Organisms that contain two identical copies of the same gene on corresponding chromosomes
127
Humoral Immunity
The synthesis of specific antibodies by activated B-cells in response to an antigen. These antibodies bind to the antigen and either clump together to become insoluble or attract other cells that engulf them
128
Hyperventilation
An increase in the rate of inhalation. lack of oxygen or an increase in blood pH promotes hyperventilation
129
Hypodermis
Layer of loose connective tissue below the dermis that binds the dermis to the body
130
Immunoglobulins
A protein antibody produced in rsponse to a specific foreign substance that recognizes and binds to that specific antigen and triggers an immune response
131
Incomplete Dominance
Describes a situtation in which an organism heterozygous for a trait will have a phenotype that is intermediate to both alleles. Neither allele, therefore, is dominant or recessive
132
Indetermintae Cleavage
A cleavage that results in cells maintaining their totipotency, or ability to develop into a complete organism
133
Induced Fit Hypothesis
Theory of enzyme catalysis which states that the partial binding of a substrate to an enzyme alters the structure of the enzyme sot that its active site becomes complementary to the structure of the substrate, enabling binding
134
Inducible System
A system in which a repressor bound to an operator prevents transcription. Additon of inducers can activate an inactive inducible system by preventing the repressor from binding to the operator
135
Induction
The influence of a group of cells sometimes called the organizer on the development of other cells. Induction is achieved by chemical substances known as inducers
136
Inferior Vena Cava
A large vein that return deoxygenated blood from the lower body and the extremities to the right atrium of the heart
137
Inner Cell mass
The group of cells in a blastocyst (mammalian blastula) that develop into the embryo
138
Insulin
Produced and secreted by the beta cells of the pancreas, insulin decreases blood glucose concentrations by facilitating the uptake of glucose by muscle and adipose cells and the conversion of glucose to glycogen in muscle and liver cells
139
Interkinesis
A short rest period between meiosis I and meiosis II during which DNA is not replicated. An ovum remains in interkinesis until it is fertilized by a sperm
140
Interoceptors
Type of sensory receptor that monitors blood pressur, the partial pressure of CO2 in the blood, and the pH of blood within the body
141
Interphase
Phase of teh cell cycle in which cell division does not take place. Includes the G1, S1, and G2 phase. Cells in this phase may or may not be growing
142
Interstitial Cell
Also referred to as "Cells of Leydig" interstitial cells are located in the testes and secrete testosterone and other androgens
143
Intestinal Glands
Secretes maltase, sucrase, lactase, aminopeptidase, dipeptidase, and enterokinase into the small intestine
144
Intrapleural Space
The space between the two membranes (visceral pleura and parietal pleura) that covers the lungs
145
Introns
Segments of noncoding eukaryotic mRNA that are spliced out and not translated
146
Inversion
A form of chromosomal rearrangement in which a portion of a chromosome breaks off and rejoins the same chromosome in the reverse position
147
Iris
Muscular tissue that controls the amount of light allowed in through the pupil
148
Lagging Strand
The strand of DNA that is synthesized in small fragments called Okazaki fragments and then ligated together. The Okazaki fragments are synthesized in the 5' to 3' direction, but the overall synthesis is in the 3' to 5' direction. The template strand has a 5' to 3' polarity.
149
Large Intestine
Section of the GI tract that consists of the cecum, the colon, and the rectum. The major function of teh large intestine is to absorb salts and water
150
Leading strand
The strand of DNA that is continuously synthesized int he 5' to 3' direction. The template strand is read in the 3' to 5' direction.
151
Leukocytes
White blood cells; the component of blood involved in cell defense and immunity. neutrophils, basophils, eosinophils, lymphocytes, and monocytes are types of leukocytes
152
Linked Ggenes
Genes that are located on the same chromosome
153
Lock and Key theory
Theory of enzyme catalysis starting that the active site' structure is complementary to the structure of the substrate
154
Luteinizing Hormone
Synthesized and released by teh anterior pituitary, LH stimulates ovulation and formation of the corpus luteum. LH is regulated by estrogen, progesteron, and gonadotropin-releasin ghormone (GnRH)
155
Lymph Nodes
Swellings along the lymph vessels where lymph is filtered by leukocytes to remove antigens
156
Lymphatic System
A system of vessels and lymph nodes that collect intersitital fluids and return them to the circulatory system, thereby maintaing a plasma protein and fluid balance. The lymphatic system is also involved in lipid absorption and lymphocyte production
157
Lysogenic Cycle
Phase of viral replication in which the DNA of the bacteriophage becomes integrated in the host's genome and replicates as the bacteria replicates
158
Lysosome
Membrane-bound vesicle that contains hydrolytic enzymes used for intracellular digestion
159
Lytic Cycle
Phase in viral replication in which the host cell is lysed and releases new virons
160
Mechanical Digestion
Breakdown of food particles into smaller particles through such activities as biting, chewing, and churning
161
Medulla Oblongata
The part of the brain that controls such functions as breathing and heartbeat
162
Meiosis
A two-phase cell division in germ cells that results in the formation of four haploid cells from one diploid cell
163
Mendel's Law of Independent Assortment
The alleles of different genes assort independently during meiosis. We now know that this is true only for unlinked genes
164
mendel's Law of segregation
mendel's postulation that there are alternate versions of genes that account for genetic variation. Each individual has two alleles for each gene, on maternal and one paternal in origin. During meiosis, these two alleles separate into two different gametes
165
Mesoderm
Primary germ layer that lies between the ectoderm and teh endoderm. Gives rise to the musculoskeletal system, circulatory system, excretory system, gonads, connective tissue throughout the body, and portions of the digestive and respiratory organs
166
Michaelis Constant
Michaelis constant, Km, is the ratio of teh breakdown of an enzyme-substrate complex to its formation is simple Michaelis-menton reactions. Km is alos half Vmax, and low Km indicates a strong affinity between an enzyme and its substrate
167
Mitochondria
The site of aerobic respiration that provides the cell with a majority of its energy in the form of ATP. The mitochondrion is a semiautonomous organelle enclosed by two membranes, with an intermembrane space between the two membranes and mitochondrial matrix enclosed by the inner membrane
168
Mitosis
Cell division and/or nuclear division in somatic cells that results in daughter nucleus receiving a full complement of the organism's genome
169
Mitral Valve
A valve located between the left atrium and the left ventricle. the valve consists of two cusps and prevents backflow of blood from the ventricles to the atria
170
Monohybrid Cross
A cross between two organisms where only one trait is being studied
171
Monosynaptic Reflex
Reflex pathway that has only one synapse between the sensory neuron and the motor neuron (ex knee-jerk reflex)
172
mRNA (messenger RNA)
Class of RNA that is created from the transcription of DNA and serves as the template for protein synthesis during translation
173
Myelin Sheath
Insulating substance that surrounds axons. Action potentials cannot take place in areas of the axon that are myelinated
174
Na+/K+ Pump
A protein that hydrolyzes one ATP to transport three Na+ out of the cell from every two K+ it transports into the cell
175
Negative Pressure Breathing
The contraction of the diaphragm and the intercostal muscles increases the volume of the thoracic cavity, reducing the pressure in the intrapleural space. This decrease in pressure creates a vacuum that causes the lungs to suck in air.
176
Nephron
The functional unit of the kidney. Can be subdivided into Bowman's capsule, proximal convoluted tubule, descending limb of the loop of Henle, ascending limg of the loop of Henle, distal convoluted tubule, and collecting duct
177
Neural Crest Cells
Cells at the tip of teh neural fold; this group of cells give rise to many components of teh peripheral nervous system
178
Neurotransmitters
Chemical messengers released from synaptic clefts of a neuron that can bind and stimulate a postsynaptic cell
179
Nodes of Ranvier
Gaps between segments of myelin sheath where action potentials can take place, allowing for saltatory conduction
180
Noncompetitive inhibitor
Molecule that inhibits the activity of an enzyme by binding to a regulatory site on the enzyme, thereby changing the conformaiton of teh enzyme. Because these inhibitors do not directly compete with the substrate, increasing substrate concentration usually has little effect on the catalytic rate
181
Nondisjunction
The failure of homologous chromosomes or sister chromatids to separate properly during meiosis I and meiosis II, respectiely. This usually results in gametes that lack certain genes or have multiple copies of those genes.
182
Obligate Intracellular Parasites
Organisms that require a host cell to express their genes and reproduce
183
Okazaki Fragments
Smallfragments of DNA that form the lagging strand
184
osmoregulation
Maintenance of water and solute concentrations
185
Osmosis
Passive movement of water from a region of higer water concentration to a region of lower water concentration; diffusion of water
186
Osteoblasts
Cells in teh bone tissue that secrete the organic constitutents of teh bone matrix. Osteoblasts develop into osteocytes
187
Osteoclasts
cells in the bone matrix that are involved in bone degradation
188
Osteons
The structural unit of compact bone that consists of a central canal, called the haversian canal, surronded by a number of concentric rings of bony matrix called lamellae
189
Oxidative Phosphorylation
The coupling of the oxidation of NADH, NADPH, and FADH2, with the phosphorylation of ADP. The electron transport chain utilized oxidative phosphorylation to produce ATP
190
Pancreas
Secretes pancreatic amylase, trypsin, chymotrypsin, carboxypeptidase, and lipase into the small intestine
191
Parathyroid Hormone
Synthesized and released by the parathyroid gland, PTH increases bloog Ca2+ concentration by increasing Ca2+ reabsorption in the kidneys and by stimulating calcium release from bone
192
Parthenogenesis
The development of an unfertilized egg into an adult organism with haploid cells
193
Passage of Air during Inhalation
Air travels through the pharynx, larynx, trachea, bronchi, bronchioles, and finally alveoli (site of gas exchange)
194
Passive Immunity
A short-lived immunity resulting from the transfer of antibodies into an individual who does not produce those antibodies
195
Path of Electrical Impulse
The elecctrical impulse orginates in the sinoatrial (SA) node, located in the right atrium. It then travels throughthe atrioventricular (AV) node, then throught he bundle of His, and finally through the Purkinje fibers
196
Penetrance
The percentage of people in a population with a certain genotype who express the assocaited phenotype
197
Peptide Hormones
Polar hormones incapable of permeating the cell membrane that bind to surface receptors and act rhough secondary messengers
198
Peripheral Nervous System
All neurons that are not part of the central nervous system, including sensory and motor neurons that connect to the central nervous system. Can be divided into the somatic nervous system and the autonomic nervous system
199
Peristalsis
Involuntary muscle contractions of the esophagus that push food down the digestive tract
200
Phenotype
The physical manifestation of an individual's genotype
201
Photoreceptors
Light-sensitive proteins
202
Placenta
The organ formed by the uterus and the extraembryonic membranes of teh fetus. The placenta contains a network of capillaries through which exchange between the fetal circulation and maternal circulation takes place
203
Point Mutation
Mutation in which one nucleotide base is substituted by another. The protein products are usually functional
204
Polar Body
A small, short-lived haploid cell created during oogenesis that receives very little cytoplasm, organelles, and nutrients
205
Portal Systems
Circulatory routes in which blood travels through two capillary beds before returning to the heart. Some example include the hepatic portal system, the renal portal system, and the hypophyseal portal system
206
Post-transcriptional RNA processing
In eukaryotes, once an RNA molecule is transcribed, it is spliced and a 5' cap and 3' polyA tail are added. RAN in prokaryotes does not udnergo such processing
207
Posterior Pituitary
Stores and releases hormones (oxytocin and ADH) synthesized by the hypothalamus. The release of these hormones is triggered by an action potenital that orgininates in the hypothalamus
208
Primary Response
The inital response to a specific antigen. During a primary response, T and B lymphocytes are activated and specific antibodies and memory cells to the antigen are produced
209
Primary Spermatocyte
Diploid cells that undergo meiosis I to form two haploid secondary spermatocytes
210
Primase
A type of RNA polymerase that adds short segments of RNA during replication to which DNA polymerase can add nucleotides. Without primase, DNA replication cannot be initiated
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Progesterone
Hormone synthesized and released by the ovaries, corpus luteum, and placenta. During the luteal phase of the menstrual cycle, the corpus luteum secretes progesteron, which along with estrogen, stimulates the development and maintenance of the endometrial walls for implantation of the embryo
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Prolactin
A hormone synthesized and released by the anterior pituitary that stimulates milk production and secretion in female mammary glands
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Proprioceptor
Type of sensory receptor that monitors the body's position in space
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Proximal convoluted tubule
Site where glucose, amino acids, and other important organic molecules are reabsorbed. The proximal convoluted tubules lie in the cortex of the kidney
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Purines
Adenine and Guanine They are bicyclic nitrogenous bases that pair with pyrimidiens in double-stranded DNA in order to keep the width of the strand constant
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Pyloric Glands
Glands located in the walls of the stomach that secrete the hormone gastrin in response to certain substances in food
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Pyloric Sphincter
A valve between the stomach and the small intestine that regulates the flow of chyme into the small intestine
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Pyrimidines
Cytosine and Thymine are called Pyrimidines. They have characteristic monocyclic nitogenous bases and pair with purines in double-stranded DNA in order to keep the width of the strand constant
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Pyruvate decarobyxlation
The first stage of cellular respiraiton. Pyruvate is oxidized to acetate, which then combines with coenzyme A to form acetyl CoA in the mitochondrial matrix. This process results in the formation of one NADH per pyruvate molecule or two NADH per glucose molecule
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Recombination Frequency
The proportion of gametes that receive recombinat chromosomes. If the recombination frequency of two particular traits is high, then it can be inferred that they lie far apart on the same chromosome
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Red fibers
Slow-twitch muscle fibers. They are primarily aerobic and contain many mitochondria and myoglobin
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Refractory Period
A short period to time immediately following an action potential in which neurons or muscle cells are unresponsive to a stimulus. In some cases, a stimulus that is much larer than the threshold causes an action potential in a cell in a refractory period (relative refractory period)
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Regulator
A molecule, other than the substrate, that can bind to the allosteric site of an enzyme and either incerase its activity (allosteric activator) or decrease its activity (allosteric inhibitor)
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Repolarization
A process that occurs when the voltage-gated Na+ channels close and voltage-gated K+ channels open, allowing K+ to rush out of the cell and reploarize it
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Repressible System
A system that is normall "turned on" but can be inactivated by the additon of a repressor or corepressor
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Residual Volume
The amount of air that must remain in the lung at all times in order to prevent lung collapse
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Resting Potential
The charge difference (maintained by the Na+/K+ pump) across the cell membrane of a neuron or a muscle cell while at rest
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Retina
A thin layer of cells containing photoreceptors at the back of the eye that converts light signals into neural impulses
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Reverse Transcriptase
An enzyme in retrobiruses that uses RHA strands as templates for synthesizing cDNA molecules
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Ribonucleic Acid
RNA is similar to DNA, but the sugar in RNA is a ribose, and adenine pairs with uracil instead of thymine
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rRNA (ribosomal RNA)
Class of RNA that is a structural component of ribosomes. rRNA is synthesized in the nucleolus
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Saltatory Conduction
A means by which action potential jump from node to node along an axon
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Sarcomere
The structural unit of striated muscle. It is composed of thin (mostly actin) and thick (mostly myosin) filaments
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Sarcoplasmic Reticulum
A modified form of endoplasmic reticulum, which stores calcium that is used to trigger contraction when the muscle is stimulated
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Schwann cells
Cells that produce myelin in the peripheral nervous system
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Sclera
The white covering of the eye. Made up of connective tissue
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Secondary Response
Subsequent infections by antigens trigger a more immediate response by the memory cells produced during the primary response
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Semen
The fluid discharged during ejaculation. Semen consists of sperm cells and seminal fluid (fluid from the prostate and bulbourethral glands)
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Semiconservative Replication
A replicated molecule of DNA contains one strand from the original DNA molecule (used as the template) and a newly synthesized DNA strand
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Semilunar valves
Valves that prevent backflow of bloood from the arteris back into the ventricles (aortic valve and pulmonic valve)
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seminiferous Tubules
Locatd in the testes, the seminiferous tubules are the site of sperm production
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Simple diffusion
Passive movement of particles from a region of higher concentration to a region of lower concentration without the use of energy
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Sister Chromatids
After replication, each chromosome consists of two identical chromatids held together at a central region called the centromere. After the mitotic spindle pulls the sister chromatids apart, each chromatid is referred to as a chromosome
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Small Intestine
Three small intestine can be subdivided into three sections: the duodenum, jejunum, and ileum. Most digestion takes place in the duodenum and most absorption takes place in the jejunum and the ileum
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Somatic Cells
All cells excluding the germ (reproductive) cells
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Somatic Nervous System
Division of the peripheral nervous system that is responsible for voluntary movement
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Somatostatin
Produced and secreted by the delta cells of the pancrease, somatostatin inhibits the release of glucagon and insulin
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Spermatozoa
Mature sperm specialized for transporting the genetic information from the male to the ovum
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Spongy bone
Lighter and less dense than compact bone, it consists of an interconnecting lattice of bony spicules (trabeculae). The cavities between the spicules contain bone marrow.
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Stabilizing Selection
Type of natural selection where the normal phenotype is favored while those outside the norm are eliminated
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Steroid Hormones
Nonpolar hormones that permeate the cell membrane and act by binding intracellular receptors
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Substrate Level Phosphorylation
The transfer of phsophate group from an organic compound to ADP. Glycolysis and the citric acid cycle utilize substrate level phosphorylation to produce ATP
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Superior Vena Cava
A large vein that returns deoxygenated blood from the head and neck regions to the right atrium of the heart
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Surfactant
A liquid substance produced by the lung that reduces surface tension in the alveoli. Surfactant prevents lung collapse and decreasees the effort needed to expand the lungs (inhale)
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Synapse
The space between the axon terminal of one neuron and the dendrite of another enuron where neurotransmitters are released
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Synaptic Terminals
Ends of axons that form one side of the synaptic cleft; the location where neurotransmitters are stored
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Systole
The stage of the heart cycle in which the heart muscle contracts and pumps blood
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Test Cross
A cross between an organism of an undetermined genotype and another this is homozygous recessive for the trait of interest
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Testosterone
Hormone secreted by the interstitial cells of teh testes. Testosterone is responsible for embryonic sexual differentiation, male sexual development, and the maintenance of masculin secondary sexual characterisitics
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Tetrad
Four chromatids that result when a pair of homologous chromosomes synapse during prophase I of meiosis
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Thermoregulation
Maintenance of a constant internal body temperature
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Threshold Value
The minimal value that must be reached in order for the system to respond. Muscle fibers and neurons exhibit an all-or non response, where the system initiates an action potential only if the threshold value is met.
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Thyroid Hormones
Synthesized and released by the thyroid gland, thyroid hormones (thyroxine, T4, and triiodothyronine) stimulate cellular respiration as well as protein and fatty acid synthesis and degradation
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Thyroid-Stimulating Hormone
Synthesized and released by the anterior pituitary, TSH stimulates the thyroid gland to absorb iodine so that it can synthesize and secrete thyroid hormone. TSH is regulated by thyroid-releasing hormone )TRH, which is released by the hypothalamus
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Tidal Volume
The volume of air that is normally inhaled or exhaled with each breath
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Total lung capacity
The maximum volume of air that the lung can hold, which includes the vital capacity and the residual volume
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Translation
The transfer of information from an RNA moleucle to a polypeptide. The three stages of polypeptide synthesis (initiation, elongation, and termination) require energy and are mediated by various enzymes. During translation, mRNA is read in the 5' to 3' direction
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Translocation
A form of chromosomal rearrangement in which a portion of one chromosome adds on to a nonhomologous chromosome
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Transverse tubules
A system of tubules that provides channels for ion flow throughout the muscle fibers to facilitate the propagation of an action potential
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Tricuspid Valve
A valve located between the right atria and the right ventricle. The valve consists of three cusps and prevents backflow of blood from the ventricle to the atria
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tRNA (Transfer RNA)
Class of RNA bearing an anticodon (complementary to the codon) and the amino acid for the corresponding codon. tRNA is vital in translation, as it brings the amino acids to the ribosome and ensures that each codon matches up with the proper amino acid
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Umbilical cord
Connects the vasculature of teh fetus to the placenta
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Veins
Vessles that carry blood toward the heart. These vessels are thin-walled and have valves to prevent backflow
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Ventricles
The muscular lower chambers of the heart. The right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery, while the left ventricle pumps oxygenated blood throughout the body
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Villi
Fingerlike projections that extend out of the small intestine in order to increase surface area for maximum absorption
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Vital capacity
The maximum volume of air that can be inhaled or exhaled by the lungs with each breath
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White fibers
Fast-twitch muscle fibers. They are primarily anaerobic and fatigue more easily than red fibers
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Wild Type
An allele that is normal to the population
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Zone Pellucida
Inner layer of cells surrounding the oocyte. These cells are secreted by follicle cells. Penetration of teh zona pellucida by a sperm forces the seondary oocyte to undergo meiosis II
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Zygote
A fertilized egg
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Zymogen
Enzyme that must undergo processing before it can catalyze reactions
