midterm Flashcards
(100 cards)
1
Q
What is the internal environment of the cell?
A
extracellular fluid (plasma, interstitial) that surrounds each cell
2
Q
What do solute, solvent, and solution mean? What are hydrophilic, hydrophobic, and amphipathic molecules?
A
SOLUTE: substance dissolved in a liquid
SOLVENT: the liquid in which a substances are dissolved (e.g., water)
SOLUTION: solutes dissolve in a solvent to form a solution
HYDROPHILIC have a number of polar bonds and/or ionized groups, soluble in water (e.g., carboxyl, amino)
HYDROPHOBIC are composed mostly of carbon and hydrogen, insoluble in water (bc electrically neutral covalent bonds, e.g., C-H, are not attracted to water)
AMPHIPATHIC have polar or ionized region at one site and nonpolar at another, when mixed with water form clusters with polar (hydrophilic) heads at surface of cluster and nonpolar (hydrophobic) tails oriented inward
3
Q
What is organic chemistry?
A
chemistry of the compounds of carbon
4
Q
What are the major classes of organic molecules?
A
carbohydrates, lipids, proteins, nucleic acids
5
Q
What are the subclasses of carbohydrates?
A
monosachharides, disaccharides, polysaccharides
6
Q
What are the subclasses of lipids?
A
fatty acids, triglycerides, phospholipids, steroids
7
Q
What are endocrine glands? What do they do?
A
glands of the endocrine system that produce and secrete hormones into the bloodstream
8
Q
What are proteins and what are they made out of?
A
complex polymers of more than 50 amino acids (folded into a characteristic shape forming a functional molecule)
9
Q
What are peptides and what are they made out of?
A
- amides, -NHCO-
- a polypeptide with 50 or fewer amino acids, with a known biological function
10
Q
What are polypeptides?
A
a sequence of amino acids linked by peptide bonds
11
Q
What is a peptide bond?
A
bond formed between amino and carboxyl group (polar covalent)
12
Q
What are fatty acids? What do they do?
A
building block of lipids, provide energy for cellular metabolism
(carbon chain w/ acidic carboxyl group at one end)
types:
- SATURATED (when all Cs are linked by single covalent bonds (animal fats))
- UNSATURATED (one or more double bonds of C (vegetable oils))
- POLYUNSATURATED (more than one C double bond (vegetable fats))
- EICOSANOIDS (derived from the polyunsaturated arachidonic acid) regulate a number of cell functions
13
Q
What are triglycerides? What do they do?
A
a subclass of lipids, “fat”; majority of body’s lipids; found in blood and can be synthesized in liver; stored (via dehydration) in adipose tissue where they supply energy to cells (via hydrolysis) esp during fasting or exercising
(glycerol + 3 fatty acids) combine by dehydration to form triglycerides and water
14
Q
What are phospholipids? What do they do?
A
a subclass of lipids, amphipathic (w/ polar hydrophobic end + nonpolar hydrophobic end) permits them to form the lipid bilayers of cellular membranes
(glycerol + 2 fatty acids + phosphate + small charged nitrogen molecule)
15
Q
What are steroids? What do they do?
A
a subclass of lipids (e.g., cholesterol, cortisol from the adrenal glands, estrogen and testosterone secreted by the gonads)
(4 interconnected rings of carbon atoms, plus a few hydroxyl groups may be attached)
16
Q
What is biochemistry?
A
organic chemistry of life and its constituents
17
Q
What are monosaccharides?
A
a subclass of carbohydrates (e.g., glucose, fructose), the simplest sugars, stores energy for later use
5C + O form a ring on a flat plane, H and HO on each carbon lie above and below the plane
18
Q
What are disaccharides?
A
a subclass of carbohydrates, composed of two monosaccharides (e.g., sucrose or table sugar, lactose in milk)
dehydration links monosaccharides, hydrolysis uncouples monosaccharides
19
Q
What are polysaccharides?
A
a subclass of carbohydrates, polymers of monosaccharides (e.g., starch, glycogen or animal starch)
hydrolysis of glycogen (as during fasting) leads to release of glucose monomers into the blood, thereby preventing blood glucose from decreasing to dangerously low levels
20
Q
What are glycoproteins?
A
Proteins covalently attached to a monosaccharide; present in plasma membranes; major components of connective tissue; also abundant in fluids like mucus where they play a protective or lubricating role
21
Q
What are the subclasses of nucleic acids?
A
DNA (stores genetic info)
RNA (decode info sfrom DNA into instructions for forming specific proteins)
22
Q
What makes the cell’s plasma membrane special? What is its structure?
A
- acts as selective barrier, regulating passage of substances into and out of cell
- also detects extracellular signals, links adjacent cells, and anchors proteins on cellular surface
- structure: lipid bilayer (mostly phospholipids, 25%) with embedded proteins (55%)
- also contains cholesterol (13%)
23
Q
What are the different membrane junctions?
A
desmosomes, tight junction, gap junction
24
Q
What is a desmosome?
A
- a specialized type of membrane junction, in areas subject to stretching (skin)
- a region of 20nm btwn two adjacent cells held together by cadherins, anchored by dense protein along cytoplasmic surface of membrane
25
What is a tight junction?
- a specialized type of membrane junction that occurs in a band around the cell’s circumference
- impedes molecular movement btwn cells, joins most epithelial cells
26
What is a gap junction?
- a specialized type of membrane junction involved in transmission of electrical activity
- 2-4nm gap allows CONNEXINS from two membranes join, forming 1.5 nm protein-lined channels linking cytosols of the cells
- passes small molecules and ions (e.g., Na+ and K+), and excludes large proteins
27
What is the granular/rough endoplasmic reticulum?
- the most extensive cytoplasmic organelle, a network of membranes w/ a flattened-sac appearance
- with ribosomes bound to its cytosolic surface
- involved in producing and packaging proteins to be secreted by the cell
28
What are ribosomes?
- the "protein factories" of the cell (located in cytoplasm)
- composed of 70-80 proteins and several RNA molecules
- synthesize proteins using genetic info from DNA
- bind to rough endoplasmic reticulum (or float free in cytoplasm)
- the proteins pass into the lumen of the reticulum and are then transferred to the Golgi apparatus
29
What is the Golgi apparatus?
- the "packaging center" of the cell
- a series of flattened sacs forming a cup-shaped structure
- modifies and sorts proteins (sent from rough endoplasmic reticulum) into secretory vesicles
- e.g., where carbohydrates are linked to proteins to form glycoproteins
30
What is an oligodendrocyte?
type of glial cell in the CNS that:
1) provides physical support for neurons
2) insulates neurons by supplying myelin sheath
3) forms one 1mm segment of myelin for several adjacent axons (one process = one myelin segment)
31
What is a Node of Ranvier?
bare portion of axon btwn myelin sheaths
32
What is a Schwann cell?
PNS counterpart to oligodendrocyte:
1) an entire cell = one myelin segment
2) serves as phagocyte and guides regeneration (when peripheral nerve is damaged)
33
What is the difference btwn transcription and translation?
DNA --> RNA (in the nucleus)
RNA --> Protein (in the cytoplasm)
34
What are metabolism, anabolism, and catabolism?
- the entire collection of chemical reactions in the body
- synthesis of organic molecules by cells
- breakdown of organic molecules
35
What is a cofactor?
substance (e.g., trace metal) that ACTIVATES ENZYME - binds to enzyme altering its conformation to conform to substrate
36
What is a coenzyme?
- a cofactor that is an organic molecule and participates as one substrate in a reaction, adding or removing only a few atoms (e.g., H, acetyl, methyl)
- derived from vitamins (e.g., NAD+ from niacin, FAD from riboflavin)
37
What does the Michaelis-Menten equation mean?
- reaction rate increases as substrate concentration increases, until all active sites on enzyme are bound (saturation occurs)
- reaction time plateaus at full saturation, despite change in substrate concentration
- reaction rate can be increased by increasing enzyme concentration (even after saturation) (semi-saturation constant is unaffected)
- reaction rate can be altered by changing properties of enzyme's active site (e.g., affinity), resulting in change in semi-saturation constant (max rate is unaffected)
38
What is chemical specificity?
- shape of binding site permits only particular ligands to bind to it
- determines drug side effects (less ___, more side effects)
(shape determines proximity; greater proximity, greater force of attraction)
39
What is affinity?
- strength of binding btwn protein and given ligand
- increases with increased specificity and proximity:
HIGH (if oppositely charged + high specificity),
INTERMEDIATE (high specificity only),
LOW (low specificity only)
- if ___ is high for a drug, then very little of the drug is required to bind, thus reducing unwanted side effects
40
What are components of covalent modulation?
changes shape and activity of protein by covalently binding charged chemical group to protein side chain (e.g., phosphorylation)
1) PHOSPHATE GROUP adds negative charge to region, changing the protein's shape
2) ENZYMES accelerate rate at which substrates are converted into products
3) PROTEIN KINASE: any enzyme that mediates protein phosphorylation
4) PHOSPHOPROTEIN PHOSPHATASE: enzyme that dephosphorylates protein
phosphorylation:
protein + ATP --> phosphorylated protein + ADP
dephosphorylation:
phosphorylated protein + water --> protein + phosphate group
41
What is glycolysis?
breakdown of carbohydrates (primarily glucose) to pyruvate, in the cytosol
```
net gain (per one glucose molecule):
2 ATP + 4 H
```
- if oxygen is present, pyruvate enters Krebs cycle (where broken down to carbon dioxide), and oxidative phoshporylation (in which hydrogens are transferred to oxygen, producing water and the conversion of ADP to ATP)
- if oxygen is absent, pyruvate is converted to lactate
42
What is the Krebs cycle? Where does it take place, what are the steps in the process, and results?
major source of H for oxidative phosphorylation
three products:
1) H ions - H atoms bound to coenzyme molecules and available for oxidative phosphorylation lose electrons, converting them to H ions (which yield WATER and the conversion of ADP to ATP)
2) CO2
3) ATP
net reaction per glucose molecule: 2 acetyl-CoA + 6 H20 + 2 ADP --> 4 CO2 + 16 H + 2 CoA + 2 ATP
43
How is fat metabolized?
- triacylglycerol (3 fatty acids linked to glycerol)
- stored in adipocytes (almost all of cytoplasm is filled with single fat droplet); adipose tissue are clusters of adipocytes, mostly under skin
- catabolism of one 18-carbon saturated fatty acid yields 146 ATP molecules
- (in contrast, catabolism of one glucose molecule yields max 38 ATP molecules)
44
How are proteins and amino acids metabolized?
PROTEASES (enzymes) break peptide bonds btwn amino acids
OXIDATIVE DEANIMATION:
- amino group is removed from amino acid
- amino group (NH2) gives rise to ammonia molecule (NH3)
- and is replaced by O atom (derived from water) to form a KETO ACID
- (the remainder can be metabolized to intermediates that can enter the glycolytic pathway or the Krebs cycle)
45
What are the essential nutrients?
- substances (about 50) that
(1) are essential for health, and
(2) cannot be synthesized by the body in adequate amounts
- include water, mineral elements, essential amino acids, essential fatty acids, vitamins, and other essential nutrients
46
What is ATP used for?
- synthesis of cellular components
(peptide linkages in protein synthesis,
glucose from lactic acid,
fatty acids from acetyl-CoA, cholesterol, phospholipids, hormones, urea, etc.)
- muscular contraction
- active transport across membranes
- glandular secretion
- nerve conduction
47
How is pyruvic acid converted to acetyl CoA?
- after glycolysis and before Krebs cycle, the 2 derivative pyruvate acid molecules (from glycolysis) enter the mitochondrial matrix (by facilitated diffusion) where they are converted into 2 molecules of acetyl-CoA
- 2-carbon acetate is added to CoA to form acetyl-CoA
- no ATP is formed in this stage
48
What is simple diffusion?
movement of a solute down its concentration gradient (from high to low) (solely as a result of random thermal motion)
- small (e.g., oxygen, carbon dioxide)
- lipid soluble (e.g., steroids)
49
What is facilitated diffusion?
like simple diffusion but requires transporter (e.g., glucose)
50
How does oxidative phosphorylation form ATP?
- oxidation of the H atoms released during earlier stages of glucose degradation (producing 90% of total ATP formed by glucose metabolism)
- results from series of enzymatically catalyzed reactions in mitochondria that:
1) split each H atom into an H ion + an electron (which enters the electron transport chain)
2) use the electrons to change dissolved O into OH ions; H and OH ions combine to form H2O
- energy transfer takes place on inner membranes of mitochondria, involving cytochromes (iron-containing proteins)
- H is stripped from coenzyme, and electrons are donated to O
- ATP synthase uses the energy derived from the concentration gradient and flow of hydrogen ions to synthesize ATP from ADP + inorganic P (CHEMIOSMOSIS)
51
What is resistance? What is conductance? What is Ohm's Law?
the hindrance to electrical charge movement (in ohms)
the reciprocal of resistance (in siemens)
I = V / R, or, I = V x G
the effect of voltage V and resistance R on current I (if resistance is high, current flow will be low)
52
What is membrane capacitance (C)?
C = Q / V
capacity of isolated conductors to hold electrical charge, where Q is amount of charge (+ or -) on either conductor (in farads)
53
What is the Nernst equation?
the electrical potential necessary to balance a given ionic concentration gradient across a membrane so that the net flux of the ion is zero (the equilibrium potential)
```
E = ( RT / ZF ) ln ( Co / Ci), where
E is potential difference across membrane in mV,
R is universal gas constant,
T is Kelvin temperature,
F is Faraday constant,
Z is valence of ion,
Co is extracellular concentration of ion,
Ci is intracellular concentration of ion
```
assumptions:
1) only electrostatic and diffusion forces are at work
2) ion is free to cross membrane
3) system is in equilibrium
54
What does the Goldman equation do, and what does it mean?
- used to accurately calculate resting membrane potential (Vm). taking into account concentration gradients and relative membrane permeabilities for individual ions
- means that the contribution of an individual ion to the overall membrane potential is a function of its CONCENTRATION GRADIENT and RELATIVE PERMEABILITY
55
What is an action potential?
- a stereotyped change in membrane potential:
if resting membrane potential moves past threshold, membrane potential quickly moves to +40mV then returns to resting level
- ionic basis: NA+ in, upswing of spike; K+ out, downswing of spike
- a brief all-or-none depolarization of the membrane, which reverses polarity in neurons; it has a threshold and refractory period, and is conducted without decrement
56
What is hyperpolarization?
when membrane potential is even more negative than resting potential
57
What is depolarization?
when membrane potential becomes less negative (closer to zero) than resting potential
58
What is the threshold of excitation?
the membrane potential at which an action potential is initiated
59
What are eicosanoids?
- converted from arachidonic acid by cytoplasmic enzymes
- exert paracrine and autocrine effects, such as smooth muscle releaxation
- include CYCLIC ENDOPEROXIDES, PROSTAGLANDINS (vascular actions, inflammation), THROMBOXANES (blood clotting, other vascular actions), and LEUKOTRIENES (mediate allergic and inflammatory reactions)
60
What is a therapeutic index?
the ratio btwn the dose that produces the desired/specified effect in 50% of the population (median effective dose), and the dose that produces toxic effects in 50% (median lethal dose)
61
What are the effects of repeated administration?
TOLERANCE (a decrease in the effectiveness of a drug administered repeatedly)
SENSITIZATION (an increase in the effectiveness of a drug administered repeatedly)
62
What is Methylphenidate?
a drug that inhibits dopamine reuptake
63
What is Monoamine Oxidase (MAO)?
a class of enzymes that destroy the monoamines
64
What is Deprenyl?
a drug that blocks MAO-B activity, acts as a dopamine agonist
65
What is Chlorpromazine?
a drug that reduces the symptoms of schizophrenia by blocking dopamine D2 receptors
66
What is an NMDA receptor? Which neurotransmitters are involved, and what processes are implicated?
- a specialized ionotropic glutamate receptor (found in postsynaptic membranes)
- controls a calcium channel normally blocked by Mg2+ ions; activation by gluatamate requires:
GLYCINE BINDING,
DEPOLARIZATION, &
DISPLACEMENT OF MAGNESIUM IONS
(thus, is a voltage- and neurotransmitter-dependent ion channel)
- implicated in mediating EXCITOTOXICITY (spread of cell death/injury), and cooperating (along with AMPA receptors) in LONG-TERM POTENTIATION (which couples frequent activity across a synapse with lasting changes in strength of signaling)
- memory, synaptic plasticity, learning
67
What is GABA?
- an amino acid, the most important INHIBITORY neurotransmitter in the brain
- produced from glutamic acid by the action of an enzyme called GAD (glutamic acid decarboxylase) that removes a carboxyl group
- distribution: widespread throughout gray matter of brain, and dorsal horn of spinal cord
- implicated in some forms of epilepsy, and Huntington's Chorea
68
What is Allylglycine?
a drug that inhibits GAD activity, and thus blocks the synthesis of GABA
69
What is Muscimol?
a direct agonist for the GABA binding site on the GABA(A) receptor
70
What is Bicuculline?
a direct antagonist for the GABA binding site on the GABA(A) receptor
71
What is Tetanus toxin?
antagonist, inhibits release of GABA and glycine (causes lockjaw)
72
What are Picrotoxin and Bicuculline?
GABA antagonists, block GABA receptor sites
73
What is Muscimol?
GABA agonist, stimulates receptor sites (a hallucinogen)
74
What is 2-hydroxy-GABA?
GABA agonist, retards reuptake
75
What is GABAtransaminase (GABA-T)?
GABA antagonist, breaks down excess GABA
76
What is n-propylacetic acid?
GABA agonist, deactivates GABA-T, used for epilepsy
77
What is Huntington's Chorea?
involves degeneration of GABA cells in basal ganglia
78
What is glycine?
- an amino acid, and important INHIBITORY neurotransmitter in lower brain stem and spinal cord
- binds to ionotropic receptors that allow chloride to enter, thus produces inhibitory postsynaptic potentials when active
- essential for maintaining a balance of excitatory and inhibitory activity in spinal cord integrating centers that regulate skeletal muscle contraction (an antagonist is STRYCHNINE, rat poison, which causes convulsions and death)
- some terminal buttons in brain release both glycine and GABA, producing rapid, long-lasting postsynaptic potentials:
glycine stimulates rapid ionotropic receptors, and
GABA stimulates long-lasting metabotropic receptors
79
What is strychnine?
a drug (used for rat poison), a direct antagonist for glycine receptor, causes convulsions and death, found in seed of a tree found in India
80
What is an endocannabinoid?
a lipid and endogenous ligand for cannabinoid receptors, which also binds with THC (the active ingredient of marijuana)
81
What is THC?
the active ingredient of marijuana, interacts with cannabinoid (CB1) receptors in brain to produce analgesia and sedation
82
What is anandamide?
the first cannabinoid (natural ligand for THC receptor) to be discovered, a lipidlike substance
synthesized as needed and not stored in synaptic vesicles, deactivated by FAAH
83
What is FAAH?
fatty acid amide hydrolase, the enzyme that destroys anandamide after it is brought back into the cell by anandamide transporters
84
What is nitric oxide?
- a soluble gas produced by cells in the nervous system, used to communicate btwn distant cells
- created within cells from the amino acid arginine, by the enzyme nitric oxide synthase
- exerts effects within intestinal muscles, dilates brain blood vessels, contributes to changes in blood vessels that produce penile erections
- activates an enzyme that produces cyclic GMP (cGMP, a secondary messenger) within adjoining cells
- Sildenafil (Viagra) binds with the enzyme that destroys cGMP, causing cGMP to be destroyed at a much slower rate
85
What is carbon monoxide?
a soluble gas that, like nitric oxide, synthesizes cGMP
86
What are benzodiazepines, and what do they do?
- a category of anxiolytic (anxiety-dissolving) drugs, an indirect agonist for the GABA(A) receptor
- stimulates specific binding site, amplifying GABAergic effect on neurotransmitter-dependent Cl ion channel
- increases GABA receptor sensitivity (like ethyl alcohol)
- e.g., diazepem (Valium) which reduces anxiety and facilitates sleep
87
What are opiates?
type of analgesic drug that stimulates opiate receptors, are effective but addictive
- opium
- morphine
- heroin
- codeine
- methadone
88
What are endogenous opioids?
type of analgesic drug; peptide neuromodulators produced in brain (e.g., enkephalins)
89
What is aspirin?
produces analgesic effects by interfering with production of prostaglandins, which mediate pain sensations
90
What is nitric oxide?
- a soluble gas produced by cells in the nervous system, used to communicate btwn distant cells
- created within cells from the amino acid arginine, by the enzyme nitric oxide synthase
- exerts effects within intestinal muscles, dilates brain blood vessels, contributes to changes in blood vessels that produce penile erections
- activates an enzyme that produces cyclic GMP (cGMP, a secondary messenger) within adjoining cells
- Sildenafil (Viagra) binds with the enzyme that destroys cGMP, causing cGMP to be destroyed at a much slower rate
91
What is carbon monoxide?
a soluble gas that, like nitric oxide, synthesizes cGMP
92
What are benzodiazepines, and what do they do?
- a category of anxiolytic (anxiety-dissolving) drugs, an indirect agonist for the GABA(A) receptor
- stimulates particular binding site which then amplifies GABAergic effect on neurotransmitter-dependent Cl ion channel
- e.g., diazepem (Valium) which reduces anxiety, facilitates sleep, reduces seizure activity, produces muscle relaxation
93
What are opiates?
opium, morphine, heroin, codeine, methadone
stimulate opiate receptors
effective but addictive
94
What are endogenous opioids?
peptide neuromodulators produced in brain (e.g., enkephalins)
95
What is aspirin?
produces analgesic effects
by interfering with production of prostaglandins,
which mediate pain sensations
96
What is primary active transport?
direct use (HYDROLYSIS) of ATP to move a solute against its concentration gradient (e.g., SODIUM PUMP moves 3 sodium ion out, 2 potassium ions in)
97
What is secondary active transport?
- use of ion gradient energy (usually Na+) to move a 2nd solute against its concentration gradient, via ALLLOSTERIC MODULATION (e.g., nutrient absorption in gut)
- Sodium ions always move down their concentration gradient into a cell, and the transported solute always moves up its gradient
- COTRANSPORT: both Na+ and transported solute move in same direction
- COUNTERTRANSPORT: Na+ and transported solute move in opposite direction
98
What is endocytosis?
- entry of packets of solutes into cells (e.g., antibody absorption by gut of nursing neonates)
- regions of plasma membrane form small pockets that pinch off to produce intracellular vesicles that enclose some extracellular fluid
three types:
1) FLUID ENDOCYTOSIS ("cell-drinking")
2) PHAGOCYTOSIS ("cell-eating")
3) RECEPTOR-MEDIATED ENDOCYTOSIS (including potocytosis)
99
What is exocytosis?
- exit of packets of solutes from cells (e.g., release of neurotransmitters in the synapses of neurons)
- vesicles in cytoplasm fuse with plasma membrane and release contents to outside of cell
two functions:
1) provides way to replace portions of plasma membrane that endocytosis removed, adding new membrane components in the process
2) provides a route for membrane-impermeable molecules (e.g., protein hormones) that the cell synthesizes to be secreted into the extracellular fluide
100
What is osmosis?
net diffusion of water through a semipermeable membrane
OSMOLARITY: total solute concentration of solution
ISOTONIC: solution of NONPENETRATING SOLUTES with osmolarity of 300 mOsm
