Biology Anatomy Flashcards
5’ cap
a methylated guanine nucleotide added to the 5’ end of eukaryotic mRNA. The cap is necessary to initiate translation of mRNA
a band
The band of the sarcomere that extends the full
length of the thick filament. The A band includes
regions of thick and thin filament overlap, as well as a region of thick filament only. A bands alternate
with I bands to give skeletal and cardiac muscle a
striated apperance. The A band does not shorten
during muscle contraction.
absolute refractory period
A period of time following an action potential during
which no additional action potential can be evoked
regardless of the level of stimulation. (usually
because Na+ channel closed whle K+ efflux)
accessory glands
The three glands in the male reproductive system
that reproduce semen: the seminal vesicles, the
prostate, and the
accessory organs
(1) In the GI tract, organs that play a role in
digestion but not directly part of the alimentary
canal. These include the liver, the gallbladder, the
pancreas, adn the salivary glands.
acetylcholine ACh
The neurotransmitter used throughout the
parasympathetic nervous system as well as the
neuromuscular junction.
acetlycholinesterase (AChE)
The enzyme that breaks down acetylcholine in the
synaptic cleft.
Acetyl-CoA
The first substrate in the Krebs cycle, produced
primarily from the oxidation of pyruvate by the
pyruvate dehydrogenase complex, however
acetyl-CoA is also produced during fatty acid
oxidation and protein catabolism.
acid hydrolases
Enzymes that degrade various macromolecules and that require an acidic pH to function properly. Acid hydrolases are found within the lysosomes of cells.
acinar cells
Cells that make up exocrine glands, and that secrete their products into ducts. For example, in the pancreas, acinar cells secrete digestive enzyme; in the salivary glands, acinar cells secrete saliva.
acrosome
A region at the head of a sperm cell that contains
digestive enzyems which, when released during the acrosome reaction, can facilitate penetration of the corona radiata of the egg, and subsequently,
fertilization
actin
A contractile protein. In skeletal and cardiac muscle, actin polymerizes (along with other proteins) to form the thin filaments. Actin is involved in many contractile activities, such as cyotkinesis, pseudopod formation, and muscle contraction.
action potential
A localized change in a neruon’s or musce cell’s
membrane potential that can propogate itself away
from its point of origin. Action potentials are an
all-or-none process mediated by the opening of
voltage-gated Na+ and K+ channels when the
membrane is brought to the threshold potential;
opening of the Na+ channels causes a characteristic
depolarization, while opening of the K+ channels
repolarizes the membrane.
activation energy (Ea)
The amount of energy required to produce the
transition state of a chemical reaction. If the
activation energy for a reaction is very high, the
reaction occurs very slowly. Enzymes (and other
catalysts) increase reaction rates by reducing
activation energy.
active site
The 3D site of an enzyme where substrates
(reactants) bind and a chemical reaction is
facilitated.
active transport
The movement of molecules through the plasma
membrane against their concentration gradients.
Active transport requires input of cellular energy,
often in the form of ATP. An example is the Na+/K+
ATPase in the plasma membrane of all cells.
adenine
One of the four aromatic bases found in DNA and
RNA; also a component of ATP, NADH, and FADH2. Adenine is apurine; it pairs with thymine (in DNA) and with uracil (in RNA)
adenohypophis
anterior pituitary gland
adipocyte
fat cell
adrenal medulla
The inner region of the adrenal gland. The adrenal
medulla is part of the sympathetic nervous system, and releases epinephrine (adrenaline) and
norepinephrine into the blood when stimulated. These hormones augment and prolon the effects of
sympathetic stimulation in the body.
adrenergic tone
A constant input to the arteries that keeps them
somewhat constricted to maintain a basal level of
blood pressure.
adrenocorticotropic hormone (ACTH)
A tropic hormone produced by the anterior pituitary
gland that targets the adrenal cortex, stimulating it to release cortisol and aldosterone.
afferent arteriole
The small artery that carries blood toward the
capillaries of the glomerulus
afferent neuron
A neuron that carries information (action potentials)
to the central nervous system; a sensory neuron.
albumin
A blood protein produced by the liver. Albumin
helps to mantain blood osmotic pressure (oncotic
pressure)
aldosterone
The principal mineralocorticoid secreted by the
adrenal cortex. This steroid hormone targets the
kidney tubules and increases renal reabsorption of
sodium [and excretion of potassium]. (this causes
ADH to be secreted & increased water comes out,
increasing blood pressure indirectly).
alimentary canal
Also known as the gastrointestinal (GI) tract of the
digestive tract, the alimentary canal is the long
muscular “tube” that includes the mouth esophagus, stomach, small intestine, and large intestine.
allosteric regulation
The modification of enzyme activity through
interactino of molecules with specific sites on the
enzyme other than the active site (called allosteric
sites)
alveolie
(singular alveolus.) Tiny sacs, with walls only a single cell layer thick found at the end of the respiratory bronchiole tree. Alveoli are the site of gas exchange in the respiratory system.
allele
A version of a gene. For example, the gene may be
for eye color, and the allels include those for brown
eyes, those for blu e eyes, those green eyes, etc. At most, diploid organisms can posses only two alleles for a given gene, one on each of the two homologous chromosomes.
amino acid
The monomer of a protein; amino acids have an amine group on one end of the molecule and a carboxylic acid group on the other, and of the of 2 different side
chains.
amino acid acceptor site
The 3’ end of a tRNA molecule that binds an amino
acid. The nucleotide sequence at this end is CCA
aminoacyl tRNA
A tRNA with an amino acid attached. This is made
by an animoacyl-tRNA synthetase specific to the
amino acid being attache.d
aminion
A sac filled with fluid (aminotic fluid) that surrounds
and protects a developing embryo.
amphipatic
The characteristics of a molecule that has both polar (hydrophilic) and non-polar hydrophobic) regions, e.g. phospholipids, bile, etc.
amylase
An enzyme that digests starch into disaccharides.
Amylase is secreted by salivary glands and by the
pancreas.
anabolism
The process of building complex structures out of
simpler precursors, e.g. synthesizing protiens from
amino acids.
analagous structures
Physical structures in two different organism that
have funcitonal similarity due to their evoluntion in
a common environment, but have different
underlying structure. Analogous structures arise
from convergent evolution.
anal sphincter
The valve that controls the release of feces from the rectum. It has an internal part made of smooth
muscle (thus involuntary) and an external part made of skeletal muscle (thus voluntary).
anaphase
The third phase of mitosis. During anaphase,
replicated chromosmes are split apart at their
centromeres (the sister chromatids are separated
from each other) and moved to opposite sides of the cell.
anaphase I
The third phase of meiosis I. During anaphase I the
rplicated homologous chromosomes are separated
(the tetrad is split) and pulled to opposite sides of
the cell.
anaphase II
The third phase of meiosis II. During anaphase II the sister chromatids are finally separated at their
centromeres and puled to opposite sides of the cell. Note that anaphase II is identical to mitotic
anaphase, except the number of chromosomes was reduced by half during meiosis I.
androgens
Mal sex hormones. Testosterone is the primary androgen.
angiotensin
A normal blood protein produced by the liver,
angiotensin is converted to angiotensim I by renin
(secreted by kidney when blood pressur falls).
Angiotensin I si further onverted to angiotensim II
by ACE (angiotensin converting enzyme).
Angiotensin II is a powerful systemic vasoconstrictor and stimulator of aldosterone release, both of which
result in an increase in blood pressure.
antagonist
Something that acts to oppose the action of
something else. For example, muscles that move a
join in opposite direction are said to be antagonists.
antierioir pituitary gland
also known as the adenohypophysis, the anterior pituitary is made of gland tissue and makes and secretes six different hormones: FSH, LH, ACTH, prolatcin, TSH, and growth hormone. the anterior pituitary is controlled by releasing and inhibiting factors form the hypothalamus
