MCAT Biology Flashcards
1
Q
Oligodendrocytes
A
Cells that produce myelin in the central nervous system.
2
Q
Myelin sheath
A
Electrically insulating substance that surrounds axons, secreted by Schwann cells and oligodendrocytes.
3
Q
Anaphase
A
The mitotic phase involving the separation of chromosomes.
4
Q
Cell wall
A
The cell’s protection from external stimuli and desiccation.
5
Q
Heterozygotes
A
Organisms containing two different alleles for the same gene on corresponding chromosomes.
6
Q
Neural crest cells
A
Cells at the tip of the neural fold; this group of cells gives rise to many components of the peripheral nervous system.
7
Q
Microfilaments
A
Solid rods of actin that are involved in cell movement and cell wall support.
8
Q
Appendicular skeleton
A
The bones of the pelvis, pectoral girdles, and limbs.
9
Q
Cholecystokinin
A
A hormone that is secreted by the duodenum in response to the presence of chyme. It stimulates the release of bile and pancreatic enzymes into the small intestine.
10
Q
Inversion
A
A form of chromosomal rearrangement in which a portion of a chromosome breaks off and rejoins the same chromosome in the reverse position.
11
Q
Adrenal medulla
A
Synthesizes and releases epinephrine and norepinephrine, which stimulates an increase in the metabolic rate and blood glucose levels.
12
Q
Bacteriophages
A
Viruses that can infect bacteria.
13
Q
Cornea
A
Transparent covering in front of the eye that refracts light and helps keep the eye in focus
14
Q
Osmoregulation
A
Maintenance of water and solute concentrations.
15
Q
Humoral immunity
A
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.
16
Q
Exteroceptor
A
Type of sensory receptor that monitors external signals such as light, sound, and temperature.
17
Q
Endometrium
A
The mucosal lining of the uterus where the embryo implants. Progesterone is necessary to maintain it during pregnancy.
18
Q
Iris
A
Muscular tissue in the eye that controls the amount of light allowed in through the pupil.
19
Q
Penetrance
A
The percentage of people in a population with a certain genotype who express the associated phenotype.
20
Q
Microtubules
A
Structures that maintain cell shape, form the spindle, and provide tracks along which organelles can move. They also compose cilia and flagella.
21
Q
Gametocyte
A
A cell from which gametes form by meiotic division, especially a spermatocyte or an oocyte.
22
Q
Enzymes
A
Catalysts (usually proteins) that accelerate reactions by reducing the activation energy without being consumed or altered by the reaction.
23
Q
Capillaries
A
Blood vessels composed of a single layer of endothelial cells, facilitating exchange between the blood and interstitial fluid.
24
Q
Homozygotes
A
Organisms containing two identical copies of the same gene on corresponding chromosomes.
25
Glycogen
The primary form in which carbohydrates are stored in the liver.
26
Directional selection
Type of natural selection where one extreme phenotype is favored over the mean phenotype and other extreme phenotypes.
27
Parthenogenesis
The development of an unfertilized egg into an adult organism.
28
Autotroph
An organism that can harness sunlight to create energy via photosynthesis.
29
Zygote
A fertilized egg.
30
Fluid mosaic model
A model that states that a cell membrane consists of a phospholipid bilayer with proteins embedded throughout.
31
Intramembranous ossification
This is the transformation of mesenchymal tissue into bone.
32
Lock and key theory
Theory of enzyme catalysis stating the active site's structure is complementary to the structure of the substrate.
33
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.
34
Helicase
An enzyme that unwinds the double helix of a DNA molecule and separates the two strands, allowing replication to take place.
35
Coronary arteries
Blood vessels that supply the heart with oxygenated blood
36
Adrenocorticotropic hormone
Synthesized and released by the anterior pituitary, it stimulates the adrenal cortex to synthesize and secrete glucocorticoids.
37
Seminiferous tubules (testes), epididymis, vas deferens, ejaculatory duct, (nothing), urethra, penis
Name the structures of the male reproductive tract using the Kaplan acronym (SEVEN UP).
38
Fovea
The region of the retina with a high density of cones.
39
Osmosis
The passive movement of water; diffusion of water.
40
Pyloric glands
Glands located in the walls of the stomach that secrete the hormone gastrin in response to certain substances in food.
41
Ventricles
The muscular lower chambers of the heart.
42
Genotype
Genetic makeup of an individual
43
Testosterone
Hormone secreted by the interstitial cells of the testes. It is responsible for embryonic sexual differentiation, male sexual development, and maintenance of masculine secondary sexual characteristics.
44
Lagging strand
During DNA replication, the strand of DNA that is synthesized in small fragments and then ligated together.
45
Homeostasis
The maintenance of a stable internal environment.
46
Diploid
Cells that have two copies of each chromosome, like somatic eukaryotic cells.
47
Large intestine
Section of the GI tract that consists of the cecum, colon, and rectum. The major function is to absorb salts and water.
48
Rough endoplasmic reticulum
Serves as an attachment point for ribosomes, which functions in protein synthesis.
49
Autonomic nervous system
Division of the peripheral nervous system that is responsible for involuntary movement
50
Monosynaptic reflex
Reflex pathway that has only one synapse between the sensory neuron and the motor neuron.
51
Posterior pituitary
Stores and releases hormones synthesized in the hypothalamus. Release of hormones is triggered by an action potential that originates in the hypothalamus.
52
Efferent neurons
Neurons that carry information from the central nervous system to other parts of the body.
53
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.
54
Nephron
The functional unit of the kidney.
55
Purines
Adenine and guanine. They have characteristic bicyclic nitrogenous bases and pair with pyrimidines in double-stranded DNA.
56
Diastole
The stage of the heart cycle in which the heart muscle relaxes and collects blood into its four chambers.
57
Osteoclasts
Cells in the bone matrix that are involved in bone degradation.
58
Hypothalamus
Structure responsible for visceral functions such as hunger, thirst, and sex drive.
59
Expressivity
The degree to which an organism expresses its genotype.
60
Spermatozoa
Mature sperm specialized for transporting a male's genetic information to the ovum.
61
Glomerulus
Network of capillaries within the Bowman's capsule 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.
62
Arteries
Vessels that carry blood away from the heart. These vessels are muscular and do not have valves.
63
Haploid
Cells that have only one copy of each chromosome, such as human gametes.
64
DNA ligase
Enzyme that covalently links the Okazaki fragments together during DNA replication
65
Repressible system
A system that is normally "turned on" but can be inactivated by the addition of a repressor or corepressor.
66
Semen
The fluid discharged during ejaculation, consisting of sperm cells and seminal fluid.
67
Small intestine
It can be divided 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.
68
Alleles
Genes coding for alternative forms of a given trait.
69
Disjunction
The separation of homologous chromosomes during anaphase I of meiosis.
70
Vestigial structures
Structures that have lost ancestral function, like the human tailbone.
71
Transcription
The process whereby mRNA is synthesized from a DNA template.
72
Synaptic terminals
Ends of axons that form one side of the synaptic cleft; the location where neurotransmitters are stored.
73
Proximal convoluted tubule
Site where glucose, amino acids, and other important organic molecules are reabsorbed from the filtrate into the interestitial fluid. It lies in the cortex of the kidney.
74
Cerebellum
Part of the brain that is responsible for coordination.
75
Adaptive radiation
The emergence of a number of distinct lineages from a single ancestral species.
76
Cytoskeleton
Gives cell mechanical support, maintains cell shape, and functions in cell motility. Composed of microtubules, microfilaments, and intermediate filaments.
77
Transverse tubules
A system of structures that provides channels for ion flow throughout the muscle fibers to facilitate the propagation of electrical signals from the nervous system.
78
Prolactin
A hormone synthesized and released by the anterior pituitary that stimulates milk production and secretion in female mammary glands.
79
Tetrad
Four chromatids that result when a pair of homologous chromosomes synapse during prophase I of meiosis.
80
Veins
Vessels that carry blood toward the heart. They have thin walls and have valves to prevent backflow.
81
Golgi apparatus
Receives vesicles from the smooth ER, modifies them, and repackages them into vesicles for distribution.
82
Right atrium, tricuspid valve, right ventricle, pulmonary arteries, pulmonary capillaries, pulmonary veins, left atrium, bicuspid valve, left ventricle, aorta, arteries, arterioles, vapillaries, venules, veins, vena cava
Starting with the right atrium, trace the path of blood flow throughout the body.
83
Placenta
An organ formed by the uterus and extraembryonic membranes of the fetus. It contains a network of capillaries through which exchange between the fetal and maternal circulations take place.
84
Medulla oblongata
The part of the brain that controls many basic, autonomic functions, such as breathing and heart rate.
85
Pyrimidines
Cytosine and thymine. They have characteristic monocyclic nitrogenous bases and pair with purines in double-stranded DNA.
86
Ganglion
A group of neural cell bodies in the peripheral nervous system.
87
Nodes of Ranvier
Gaps between segments of myelin sheath where action potentials can propagate, allowing for saltatory conduction.
88
Inner cell mass
The group of cells in a blastocyst that develop into the embryo.
89
Cerebral cortex
Processes and integrates sensory input and motor response, and controls memory.
90
Inducible system
A system in which a repressor bound to an operator prevents transcription. Addition of inducers can activate it by preventinr the repressor from binding to the operator.
91
Zymogen
Enzyme that must undergo processing before it can catalyze reactions
92
Fatty acid activation
The usage of two ATP molecules to convert fats into acetyl CoA for usage in the citric acid cycle.
93
Hyperpolarization
State where the potential across the membrane is more negative than the resting potential.
94
Polar body
A small, short-lived haploid cell created during oogenesis that receives very little cytoplasm, organelles, and nutrients.
95
Phenotype
The physical manifestation of an individual's genotype
96
Retrovirus
An RNA virus that codes for the enzyme reverse transcriptase, which uses the RNA as a template for DNA synthesis.
97
Telophase
The mitotic phase where cytokinesis occurs.
98
Depolarization
A process that occurs when the voltage-gated Na+ channels open, allowing Na+ to rush into the cell.
99
Residual volume
The amount of air that must remain in the lung at all times in order to prevent collapse
100
Ribonucleic acid
Similar to DNA but the sugar deoxyribose is replaced with the sugar ribose, and adenine pairs with uracil instead of thymine.
101
Incomplete dominance
Describes a situation in which an organism heterozygous for a trait will have a phenotype that is intermediate both alleles.
102
Sarcoplasmic reticulum
A modified form of endoplasmic reticulum, which stores calcium that is use to trigger contraction when muscle is stimulated.
103
Pyloric sphincter
A valve between the stomach and the small intestine that regulates the flow of chyme into the small intestine.
104
Cell theory
States that all living things are composed of cells; cells are the basic functional unit of life; cells arise only from pre-existing cells, and carry their genetic information in the form of DNA.
105
Hypodermis
Layer of loose connective tissue below the dermis that binds the dermis to the body.
106
Leukocytes
White blood cells; the component of blood involved in cell defense and immunity. Types include neutrophils, basophils, eosinophils, lymphocytes, and monocytes.
107
Frameshift 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.
108
Pancreas
Secreates amylase, trypsin, chymotrypsin, carboxypeptidase, and lipase into the small intestine.
109
Punctuated equilibrium
A model that holds that evolution is characterized by long periods of stasis punctuated by rapid evolutionary changes.
110
Pyruvate decarboxylation
The stage of aerobic cellular respiration that comes after glycolysis. Pyruvate is oxidized to acetate, which combines with coenzyme A to form acetyl CoA in the mitochondrial matrix. This process result in the formation of one NADH per pyruvate or two NADH per glucose.
111
Secondary immune response
Subsequent infections by antigens trigger a more immediate response by the memory cells produced during the primary response.
112
Osteoblasts
Cells in the bone tissue that secrete organic constituents of the bone matrix.
113
Substrate
A molecule upon which an enzyme acts.
114
Centrosome
A region of the cell that contains the centrioles.
115
Interkinesis
A short rest period between meiosis I and meiosis II. DNA is not replicated.
116
Prophage
A virus that has integrated its DNA into the host cell's DNA.
117
Hepatic portal vein
Carries nutrients absorbed in the small intestine to the liver, where they are modified to enter circulation
118
Point mutation
Mutation in which one nucleotide base is substituted for another. The protein products are often functional.
119
Exocytosis
A process in which a vesicle within the cell fuses with the membrane and releases its contents to the extracellular medium.
120
Threshold value
The minimal value that must be reached in order for a system to respond. Muscle fibers and neurons both exhibit this all-or-none response.
121
Progesterone
Hormone synthesized and released by the ovaries, corpus luteum, and placenta. During the luteal phase of the menstrual cycle, the corpus luteum secretes it, which, along with estrogen, stimulates the development and maintenance of the endometrial walls for implantation of the embryo.
122
Superior vena cava
A large vein that returns deoxygenated blood from the head and neck to the right atrium of the heart.
123
Prophase
The mitotic phase where chromosome condensation and spindle formation occurs. In mesiosis, crossing over occurs here.
124
Rh factor
An antigen on the surface of erythrocytes, classified as either positive (possessing the factor) or negative (not possessing the factor).
125
mRNA
Class of RNA that is created from the transcription of DNA (and post-transcriptional processing in eukaryotes).
126
Somatostatin
Produced and secreted by the delta cells of the pancreas, inhibits the release of glucagon, insulin, and several other hormones throughout the body.
127
Gluconeogenesis
A process in the liver by which glucose is produced using by-products of glycolysis, lipids, or fats.
128
Amnion
The innermost extraembryonic membrane that contains amniotic fluid in which the growing fetus is suspended.
129
Red fibers
Slow-twitch muscle fibers. They are primarily aerobic and contain many mitochondria and myoglobin.
130
Steroid hormones
Nonpolar hormones that permeate the cell membrane and act by binding to intracellular receptors.
131
Codon
Nonoverlapping group of three nucleotides. During translation, each is read to determine the next step in protein synthesis, usually by dictating which amino acid is added.
132
Mesoderm
Primary germ layer that gives rise to the musculoskeletal system, circulatory system, excretory system, gonads, connective tissue, and portions of the digestive and respiratory organs.
133
Operon
A group of genes or segment of DNA that regulates (bacterial) transcription.
134
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.
135
Post-transcriptional RNA processing
In eukaryotes, once an RNA molecule is transcribed, it is spliced and a 5' cap and 3' poly-adenine tail are added. This does not occur in prokaryotes.
136
Portal systems
Circulatory routes in which blood travels through two capillary beds before returning to the heart. Examples are the hepatic, renal, and hypophyseal.
137
Foramen ovale
A shunt that connects the right atrium to the left atrium in order to bypass the fetal lung.
138
Nares, pharynx, larynx, trachea, bronchi, bronchioles, alveoli
Sequence the following structures of the respiratory tract: alveoli, trachea, larynx, nares, pharynx, bronchi, bronchioles
139
Lysosome
Membrane-bound vesicle that contains hydrolytic enzymes used for intracellular digestion.
140
Somatic nervous system
Division of the peripheral nervous system that is responsible for voluntary movement.
141
Citric acid cycle
A series of reactions that begins when the two-carbon acetyl group from acetyl CoA combines with oxaloacetate to form citric acid. The cycle continues to release three NADH molecules, one FADH2 molecule, and one GTP molecule. It also regenerates oxaloacetate.
142
Bile
An alkaline fluid synthesized in the liver, stored in the gall bladder, and released into the duodenum. It aids in emulsification, digestion, and absorption of fats.
143
Pineal gland
Secretes melatonin, and is thought to help regulate sleep-wake cycles in response to external lighting cues.
144
Immunoglobulins
Protein antibodies, each of which is produced in response to a specific foreign substance.
145
Holoenzyme
An active enzyme containing all necessary cofactors.
146
Chloroplast
The site of photosynthesis in plants. It contains chlorophyll, is semiautonomous, and has two cell membranes.
147
Competitive inhibitor
Molecule that inhibits the activity of an enzyme by directly binding to the active site. It can be overcome by increasing the substrate concentration.
148
Dizygotic twins
Results when two ova are fertilized by two different sperm. Since the two resulting embryos develop from distinct zygotes, they do not have identical alleles. Also called "fraternal".
149
Endorphins
Synthesized and released by the anterior pituitary, inhibit the perception of pain.
150
Mitosis
Cell division and/or nuclear division in somatic cells that results in the daughter nucleus receiving a full complement of the organism's genome.
151
Kidney, ureter, bladder, urethra
Describe the path of urine from the kidney out of the body.
152
Somatic cells
All the cells in an organism that are not reproductive.
153
Lymph nodes
Swellings along the lymph vessels where lymph is filtered by leukocytes to remove antigens.
154
Cortisol
A glucocorticoid that increases the blood's glucose level.
155
Glycolysis
A series of enzymatic reactions in the cytoplasm that convert one molecule of glucose into two molecules of pyruvate. The energy released in the process is used to produce a net yield of two ATP and two NADH molecules.
156
Systole
The stage of the heart cycle in which the heart muscle contracts and pumps blood.
157
Insulin
Produced and secreted by the beta cells of the pancreas, it decreases blood glucose concentrations by facilitating the uptake of clucose by muscle and adipose cells, and the conversion of glucose to glycogen in muscle and liver cells.
158
Recombination frequency
Proportion of gametes that receive recombinant chromosomes for two different linked genes.
159
Peptide hormones
Hydrophilic hormones incapable of permeating the cell membrane that bind to surface receptors and act through secondary messengers.
160
Induction
The influence of a group of cells on the development of other cells.
161
Afferent neurons
Neurons that carry information to the central nervous system from outlying tissues and sense organs.
162
Fibrin
Protein responsible for blood clotting.
163
Blood antigens
Proteins found on the erythrocyte cell surface. Three antigens (A, B, and Rh) are used to differentiate blood groups.
164
Sarcomere
The structural unit of striated muscle. It is composed of thin filaments (actin) and thick filaments (myosin).
165
Tricuspid valve
The valve located between the right atrium and the right ventricle of the heart.
166
Central nervous system
Consists of the brain and spinal cord.
167
Erythrocytes
The oxygen-carrying component of blood. These anarobic cells lack organelles, are packed with hemoglobin, and feature a characteristic biconcave shape.
168
Hemoglobin
A protein found in erythrocytes made up of four polypeptide chains, each containing a heme group. It is responsible for transporting oxygen from the alveoli to the cells.
169
Oxytocin
This hormone increases the strength of contractions during childbirth.
170
DNA polymerase
An enzyme that polymerizes a complementary DNA strand in the 5' to 3' direction using a template DNA strand. It requires a primer.
171
Michaelis Constant
A constant, Km, that is a measure of the kinetics of an enzyme reaction and that is equivalent to the concentration of substrate at which the reaction takes place at one half its maximum rate.
172
Thyroid-stimulating hormone
Synthesized and released by the anterior pituitary, this hormone stimulates the thyroid gland to absorb iodine so that it can synthesize and secrete thyroid hormone.
173
Pharynx, larynx, trachea, bronchi, bronchioles, alveoli
Identify the passage of air through the body during inhalation.
174
Cardiac sphincter
A valve between the esophagus and the stomach that prevents the content of the stomach from traveling back up through the esophagus.
175
Fitness (according to Darwin)
The ability of an organism to mate and produce fertile offspring.
176
Endochondral ossification
The replacement of cartilage with bone.
177
Parathyroid hormone
Synthesized and released by the parathyroid gland, it increases calcium ion concentration in the blood stimulating its release from the bones.
178
Descending limb of the loop of Henle
Portion of the nephron permeable only to water. The filtrate becomes more concentrated as it travels through, increasing concentration of the interstitial fluid.
179
Cofactor
A nonprotein molecule that is incorporated into an enzyme and is required for proper functioning.
180
Substrate level phosphorylation
The transfer of a phosphate group from an organic compound to ADP. Glycolysis and the citric acid cycle utilize this to produce ATP.
181
Transfer RNA
Class of RNA bearing an anticodon and the amino acid for the corresponding codon. Vital for translation, as it brings the amino acids to the ribosome and ensures that each codon matches up with the proper amino acid.
182
Divergent evolution
Refers to the process whereby related groups independently develop dissimilar characteristics.
183
White fibers
Fast-twitch muscle fibers. They are primarily anaerobic and fatigue easily.
184
Cartilage
A firm, elastic, translucent connective tissue consisting of collagenous fibers embedded in chondrin. Produced by chondrocytes. Principal component of embryonic skeleton that calcifies into bones.
185
Coenzyme
An organic cofactor for an enzymatic reaction (e.g., vitamin).
186
Sclera
The white covering of the eye, made up of connective tissue.
187
Lymph node
A swelling along a lymphatic vessel that contains phagocytic cells. Their role is to filter the lymph and remove/destroy foreign particles.
188
Sister chromatids
After replication, each chromosome consists of these, held together at the centromere. The mitotic spindle pulls them apart.
189
Schwann cells
Cells that produce myelin in the peripheral nervous system
190
Facultative anaerobe
An organism that makes ATP by aerobic respiration if oxygen is present, but can switch to fermentation when oxygen is not available
191
Amino acid derived hormones
Hormones that are synthesized from amino acids. Some act via secondary messengers, while others act in a fashion similar to steroid hormones by crossing the plasma membrane into the cell.
192
Peristalsis
Involuntary contractions of smooth muscle that push food through the digestive tract.
193
Atria
The two thin-walled upper chambers of the heart.
194
Blood
Made up of plasma and cellular components, which include erythrocytes, leukocytes, and platelets
195
Mechanical digestion
Breakdown of food particles into smaller particles through such activities as biting, chewing, and churning.
196
Osteons
The structural units of compact bone that consist of a central canal, called the haversian canal, surrounded by a number of concentric rings of bony matrix called lamellae.
197
Dihybrid cross
A cross between two organisms where two distinct traits are being studied.
198
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.
199
Interoceptors
Type of sensory receptor that monitors signals inside the body, such as blood pressure, pH, or the partial pressure of carbon dioxide in the blood.
200
Follicle-stimulating hormone
Synthesized and released by the anterior pituitary, stimulates maturation of ovarian follicles in females and maturation of the seminiferous tubules and sperm production in males.
201
Lytic cycle
Phase in viral replication in which the host cell is lysed and releases new virions.
202
Active immunity
Immunity resulting from the production of antibodies during a previous infection or a vaccination.
203
Disruptive selection
A type of selection that favors phenotypic extremes, leading to the expression of two or more phenotypic forms.
204
Corpus callosum
Connects the left and right hemispheres of the brain.
205
Saltatory conduction
A means by which action potentials jump from node to node along an axon.
206
Zona pellucida
Inner layer of cells surrounding the oocyte. These cells are secreted by follicle cells. Penetration of these cells by a sperm forces the secondary oocyte to complete meiosis II.
207
Umbilical cord
Connects the vasculature of the fetus to the placenta.
208
Seminiferous tubules
Located in the testes, these are the site of sperm production.
209
Monohybrid cross
A cross between two organisms where only one trait is being studied.
210
Parallel evolution
The process whereby related groups independently develop similar characteristics due to analogous environmental pressures.
211
Corona radiata
Outer layer of cells surrounding the oocyte. These cells are secreted by follicle cells.
212
Action potential
A sharp change in the membrane potential of neurons or muscle cells caused by a change in the selective permeability to K+ and Na+ using ion-gated channels. They are all-or-none.
213
Cytochrome
A molecular electron carrier involved in oxidative phosphorylation.
214
Synovial fluid
A lubricant found in movable joints.
215
Collecting duct
Portion of the nephron permeable to water and ions. As the filtrate flows down it, the filtrate concentrates.
216
Mitral valve
A valve located between the left atrium and the left ventricle of the heart.
217
Coronary veins
Blood vessels that transport deoxygenated blood from the heart toward the right atrium.
218
B lymphocytes
White blood cells that are involved in humoral immunity.
219
Anticodon
A 3-base sequence on tRNA that is complementary to the mRNA codon.
220
Mitochondria
The site of aerobic respiration that provides the cell wit ha majority of its energy in the form of ATP. It is a semiautonomous organelles enclosed by two membranes.
221
Stabilizing selection
A type of natural selection where the mean phenotype is favored while extreme phenotypes are eliminated.
222
Plasmid
A small ring of extrachromosomal DNA found in bacteria. It replicates independently of the bacterial chromosome.
223
Intestinal glands
Secrete maltase, sucrase, lactase, aminopeptidase, dipeptidase, and enterokinase into the small intestine.
224
Simple diffusion
Passive movement of particles from a region of higher concentration to a region of lower concentration without the use of energy.
225
Neurotransmitters
Chemical messengers released from synaptic clefs of a neuron that can bind and stimulate a postsynaptic cell.
226
Vital capacity
The maximum volume of air that can be inhaled or exhaled by the lungs with a single breath
227
Axon hillock
The portion of the neuron that connects the cell body to the axon. The impulses the neuron receives from all the dendrites are summed up here to determine whether an action potential will be initiated.
228
Bohr effect
The phenomenon in which increasing the concentration of carbon dioxide reduces hemoglobin's affinity for oxygen.
229
Primary spermatocytes
Diploid cells that undergo meiosis I to form haploid secondary spermatocytes.
230
Electron transport chain
A chain of cytochromes and other proteins in the inner membrane of the mitochondria that transfers electrons from NADH and FADH2 to oxygen. The energy released by the series of oxidations is used to create a proton gradient, which ATP synthase then uses to synthesize ATP.
231
Mendel's Law of Segregation
The postulation that there are alternate versions of genes that account for genetic variation, which are separated into two different gametes during meiosis.
232
Allantois
The embryonic membrane that contains the growing embryo's waste products.
233
Monocyte
A phagocyte of foreign matter.
234
Surfactant
A liquid produced by the lung that reduces surface tension in the alveoli.
235
Filtrate
The material that passes from the blood vessels into the Bowman's capsule and travels through the nephron to eventually become urine.
236
Spongy bone
Lighter and less dense than compact bone, it consists of an interconnecting lattice of bony spicules. The cavities between the spicules contain bone marrow.
237
Binary fission
Method of asexual reproduction by which prokaryotes divide. The circular DNA molecule replicates and then moves to opposite sides of the cell, which then divides into two daughter cells of equal size.
238
Translocation
A form of chromosomal rearrangement in which a portion of one chromosome adds on to a nonhomologous chromosome.
239
Endocytosis
A process in which the cell membrane invaginates, forming an intracellular vesicle containing extracellular medium.
240
Endocrine glands
Glands that synthesize and secrete hormones into the circulatory system. Examples include the hypothalamus, pituitary, pineal, thymus, pancreas, testes, ovaries, adrenal, thyroid, and parathyroid glands.
241
Ribosomal RNA
Class of RNA that is a structural component of ribosomes, synthesized in the nucleolus.
242
Blastulation
The process by which a morula develops into a blastula with a fluid-filled cavity.
243
Photoreceptors
Light-sensitive proteins
244
Lymphatic system
A system of vessels and lymph nodes that collect interstitial fluids and return them to the circulatory system, thereby maintaining a plasma protein and fluid balance.
245
Aldosterone
A steroid hormone produced in the adrenal cortex that increases reabsorption of sodium and water and the excretion of potassium.
246
Total lung capacity
The maximum volume of air that the lung can hold, which includes the vital capacity and the residual volume.
247
Sodium-potassium pump
A protein that hydrolyzes one ATP to transport three sodium ions out of the cell for every two potassium ions it transports into the cell.
248
Hardy-Weinberg Equation
p^2 + 2pq + q^2 = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele. It predicts the frequency of homozygous dominants, homozygous recessives, and heterozygotes.
249
Leading strand
During DNA replication, the strand of DNA that is continuously synthesized in the 5' to 3' direction. The template strand is read in the 3' to 5' direction.
250
Axial skeleton
The skull, vertebral column, and bones of the chest.
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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.
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Nondisjunction
The failure of homologous chromosomes or sister chromatids to separate properly during meiosis.
253
Inferior vena cava
A large vein that returns deoxygenated blood from the lower body and the extremities to the right atrium f the heart.
254
Glucocorticoids
Synthesized and released by the adrenal cortex, raise blood glucose levels while decreasing protein synthesis.
255
Metaphase
The mitotic phase where the chromosomes line up at the equatorial plate.
256
Ductus arteriosus
A shunt that connects the pulmonary artery to the aorta in order to bypass the fetal lung.
257
Obligate intracellular parasites
Organisms that require a host cell to express their genes and reproduce. Viruses and some microorganisms belong to this category.
258
Ovary, oviduct, uterus, cervix, vagina
Starting with the ovary, name the different structures of the female reproductive tract.
259
Histone
A structural protein complexed with eukaryotic DNA to form a chromosome.
260
Exons
Segments of coding eukaryotic mRNA that are spliced together during post-transcriptional processing
261
Ductus venosus
A shunt that connects the umbilical vein to the inferior vena cava in order to bypass the fetal liver.
262
Compact bone
Much more dense than spongy bone, and consists of haversian systems, or osteons.
263
Villi
Fingerlike projections that extend out of the small intestine in order to increase surface area for maximum absorption.
264
Peroxisomes
These make hydrogen peroxide and digest fats into smaller molecules.
265
Meiosis
A two-phase cell division in germ cells that results in the formation of four haploid cells from one diploid cell.
266
Monozygotic twins
Results when a single zygote splits into two embryoes. Since both embryos contain identical alleles, they are often called "identical".
267
Differentiation
The specialization of cells that occurs during development.
268
Calcitonin
Hormone synthesized and released by the thyroid gland that decreases plasma calcium ion concentration.
269
Chemical digestion
Enzymatic breakdowns of large molecules into smaller molecules.
270
Peripheral nervous system
All neurons that are not part of the brain and spinal cord, including sensory and motor neurons. Can be further divided into the somatic and autonomic nervous systems.
271
Retina
A thin layer of cells containing photoreceptors at the back of the eye that converts light signals into neural impulses.
272
Chorion
Outermost extraembryonic membrane; contributes to the formation of the placenta.
273
Gastrulation
The process by which a single-layer becomes a three-layered gastrula.
274
Pineal gland
Secretes melatonin.
275
Expiratory reserve volume
The amount of air that can be forcible exhaled after a normal exhalation.
276
Episomes
Plasmids that have the ability to integrate into the host genome.
277
Hyperventilation
An increase in the rate of inhalation. Lack of oxygen or a decrease in blood pH promotes this.
278
Regulator
A molecule, other than the substrate, that can bind to the allosteric site of an enzyme and either increase or decrease its activity.
279
Crossing over
The exchange of genetic material between chromosomes (usually homologous) that occurs during prophase I of meiosis. It aids in evolution and genetic diversity by unlinking otherwise linked genes.
280
Analogous structures
Similar structures that share a common function but not similar origin.
281
Dermis
The layer of skin beneath the epidermis that is subdivided into the papillary layer and the reticular layer. It contains the sweat glands, sense organs, blood vessels, and bulbs of hair follicles.
282
Cardiac output
Total volume of blood the left ventricle pumps into circulation per minute. Can be increased by raising heart rate or stroke volume.
283
Active transport
Membrane transport that utilizes energy. Unlike other methods of transport, it can move particles from a region of lower concentration to a region of higher concentration.
284
Fermentation
Process by which the cell is able to anaerobically replenish the NAD+ used during glycolysis by oxidizing NADH.
285
Translation
The transfer of information from an RNA molecule to a polypeptide. The three stages of polypeptide synthesis require energy and are mediated by various enzymes. mRNA is read in the 5' to 3' direction.
286
Okazaki fragments
Small fragments of DNA that form the lagging strand during DNA replication
287
Corpus luteum
Tissue that forms from the collapsed ovarian follicle after ovulation. Produces and secretes progesterone and estrogen.
288
Exocrine glands
Glands that synthesize and secrete substances either into the digestive tract or the surface of the body through the use of ducts. Examples are the gall bladder, pancreas, and mammary glands.
289
Homologous chromosomes
Paired chromosomes in a diploid cell that contain different alleles for the same trait at corresponding loci, although not necessarily similar functions.
290
Cytosol
The fluid component of the cell's cytoplasm.
291
Chyme
Combination of partially digested food and acid that forms in the stomach.
292
Intrapleural space
The space between the two membranes that cover the lungs.
293
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 so that its active site becomes complementary to the structure of the substrate, enabling binding.
294
Chromatid
One half of a replicated chromosome. Sisters are attached by the centromere.
295
Nucleolus
This is the region of the cell that synthesizes ribosomal RNA (rRNA)
296
Gastric glands
Located in the stomach; secrete HCl and various enzymes when stimulated by gastrin.
297
Follicle
A multilayered sac of cells in the ovary that protects and nourishes the developing ovum until ovulation.
298
Test cross
A cross between an organism of undetermined genotype and another that is homozygous recessive for the trait of interest.
299
Epidermis
The outermost layer of skin, which is composed of the following sublayers: stratum basilis, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. Serves as a protective barrier against microbial attack. Derived from the ectoderm.
300
Adrenal cortex
Synthesizes and releases corticosteroids when stimulated by adrenocorticotropic hormone.
301
Refractory period
A short period of time immediately following an action potential in which neurons or muscle cells are unresponsive to a simulus.
302
Ribosome
The site of protein translation during protein synthesis.
303
Endoplasmic reticulum
The structure involved in the transport of materials throughout the cell.
304
Homologous structures
Similar structures that share a common origin.
305
Wild type
The allele for a given trait that is most common in the population of the organism found in nature.
306
Leydig cells
Located in the testes and secrete testosterone and other androgens.
307
Apoenzyme
An enzyme that requires cofactors in order to become catalytically active.
308
Periosteum
The fibrous sheath of the bone.
309
Heterotroph
An organism that breaks down organic nutrients for energy.
310
Membrane receptor
A protein that binds to molecules in the extracellular environment.
311
Growth hormone
Synthesized and released by the anterior pituitary, it stimulates bone and muscle growth, as well as glucose conservation. It is inhibited by somatostatin.
312
Chromatin
Chromosomes in their uncoiled active state.
313
Thermoregulation
Maintenance of a constant internal body temperature.
314
Noncompetitive inhibitor
Molecule that inhibits the activity of an enzyme by binding to a regulatory site on the enzyme, thereby changing the conformation. Increasing substrate concentration does little to counteract the inhibition.
315
Transport protein
Helps move polar molecules and certain ions across the cell membrane.
316
Glucagon
Produced and secreted by the alpha cells of the pancreas, it increases blood glucose concentration by promoting gluconeogenesis and glycogenolysis.
317
Oxidative phosphorylation
The coupling of the oxidation of NADH, NADPH, and FADH2 with the phosphorylation of ADP.
318
Prosthetic group
A tightly bound cofactor, such as heme.
319
Reverse transcriptase
An enzyme in retroviruses that uses RNA strands as templates for synthesizing cDNA.
320
Interphase
Phase of the cell cycle in which cell division does not take place. It includes the G1, S, and G2 phases.
321
Endoderm
The innermost of the three primary germ layers, which gives rise to the linings of the digestive and respiratory tracts, parts of the liver, pancreas, thyroid, and bladder.
322
Centrioles
These are involved in spindle formation during cell replication. They are found only in animal cells.
323
Primary immune response
The initial response to a specific antigen. T and B lymphocytes are activated and specific antibodies and memory cells to the antigen are produced.
324
Determinate cleavage
A cleavage whose future differentiation pathways are determined.
325
Luteinizing hormone
Synthesized and released by the anterior pituitary, it stimulates ovulation and formation of the corpus luteum. It is regulated by estrogen, progesterone, and gonadotropin-releasing hormone.
326
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.
327
T lymphocytes
These are involved in cell-mediated immunity. They are responsible for the body's defense against viral and fungal infections.
328
Resting potential
The charge difference across a cell membrane of a neuron or a muscle cell while at rest, maintained by the sodium-potassium pump.
329
Introns
Segments of noncoding eukaryotic mRNA that are spliced out during post-transcriptional processing and are not translated into proteins.
330
Antidiuretic hormone (ADH)
Also known as vasopressin, this hormone acts on the collecting duct of the nephron to increase water reabsorption. It is produced in the hypothalamus and stored in the posterior pituitary.
331
Convergent evolution
Refers to the independent development of similar characteristics by non-related groups.
332
Ascending limb of the loop of Henle
Portion of the nephron not permeable to water, As the filtrate flows through, ions are actively pumped out of the filtrate, decreasing its concentration.
333
Follicular phase, ovulation, luteal phase, menstruation
Name the phases of the menstrual cycle
334
Heterogenous nuclear RNA
The unprocessed precursor of mRNA
335
Synapse
The space between the axon terminal of one neuron and the dendrite of another neuron. Neurotransmitters are released here.
336
Smooth endoplasmic reticulum
The site of lipid synthesis and poison detoxification, and involved in protein transport within the cell.
337
Proprioceptor
Type of sensory receptor that monitors the body's position in space.
338
Passive immunity
A short-lived immunity resulting from the transfer of antibodies into an individual who does not produce those antibodies.
339
Ciliary muscles
Muscular tissue in the eye, attached to the lens, that is used to control the lens' shape.
340
Ligaments
Connect bone to bone and strengthen joints.
341
Thyroid hormones
Synthesized and released by the thyroid gland, are called triiodothyronine (T3) or thyroxine (T4), stimulate cellular respiration, as well as protein and fatty acid synthesis and degradation.
342
Epiglottis
A flap of cartilage that covers the glottis when swallowing food in order to prevent it from entering the larynx.
343
Tidal volume
The volume of air that is normally inhaled or exhaled with each breath.
344
Frequency summation
The process by which many successive neural impulses stimulate a neuron or a muscle until the cell being stimulated experiences an action potential or a contraction.
345
Primase
A type of RNA polymerase that adds short segments of RNA during replication to which DNA polymerase can add nucleotides. It is essential for DNA replication.
346
Allosteric enzyme
An enzyme with one or more additional bonding sites that change the conformation of the enzyme when occupied, usually promoting or inhibiting enzymatic activity.
347
Acrosome
The enzyme-containing cap-like structure on the head of a sperm.
348
Estrogen
Hormone synthesized and released by the ovaries, ovarian follicles, corpus luteum, and placenta. It stimulates the development of the female reproductive tract and secondary sexual characteristics.
349
Dendrite
An extension of the neuron that transmits impulses toward the cell body and the axon.
