objectives Flashcards
(128 cards)
1
Q
catabolic pathway
A
combust carbon fuels to synthesize ATP
2
Q
anabolic pathway
A
pathways that use ATP and reduce power to synthesize large biomolecules
3
Q
amphibolic pathways
A
can function anabolically or catabolically
4
Q
what is creatine phosphate?
A
- can regenerate ATP from ADP (allowing a short burst of activity as in a sprint)
- once creatine phosphate stores are depleted, ATP must be generated by metabolic pathways
5
Q
why are phosphate and its esters prominent in biology for several reasons?
A
1) are thermodynamically unstable, yet kinetically stable
2) stable because the inherent negative charges resist hydrolysis
3) are ideal regulatory molecules, added to molecules by kinases and removed by phosphatases
6
Q
oxidation reactions
A
loss of electrons
7
Q
reduction reactions
A
gain of electrons
8
Q
why are oxidation and reduction reactions coupled?
A
- carbon atoms in fuels are oxidized to yield CO2, and the electrons are ultimately accepted by oxygen to form H2O
- the more reduced an oxygen is, the more free energy is released upon oxidation
9
Q
what are activated carriers?
A
exemplify the modular design and economy of metabolism
10
Q
what are the 2 characteristics that are common to activated carriers?
A
1) kinetically stable in the absence of specific catalysts
2) metabolism of activated groups is accomplished with a small number of carriers
11
Q
what is an example of an activated carrier?
A
- ATP; it is an activated carrier of phosphoryl groups
- Nicotinamide adenine dinucleotide (NAD+) & flavin adenine dinucleotide (FAD) carry activated electrons derived from the oxidation of fuels
12
Q
what are 3 regulatory controls in metabolism?
A
1) amount of enzymes present (gene expression)
2) catalytic activity of enzymes (allosteric regulation, covalent modification)
3) accessibility of substrates
13
Q
what is the summary of glycolysis?
A
converting one molecule of glucose to 2 molecules of pyruvate with the generation of 2 net molecules of ATP
14
Q
what are the 2 stages of glycolysis?
A
stage 1 = traps glucose in the cell & modifies it so that it can be CLEAVED into a pair of phosphorylated 3-carbon compounds (high-phosphoryl-transfer potential)
stage 2 = oxidizes the 3-carbon compounds to pyruvate while generating 2 molecules of ATP
15
Q
what does hexokinase do?
A
- traps glucose in cell and begins glycolysis
- requires Mg2+ OR Mn2+ as a cofactor
- catalyzes the reaction
- employs substrate-binding induced fit to minimize hydrolysis of ATP
- increased specificity - decreases chance of becoming an indiscriminate ATPase
16
Q
what are the enzymes that catalyze the 3 irreversible steps in glycolysis?
A
- hexokinase
- phosphofructokinase
- pyruvate kinase
17
Q
what is alcoholic fermentation?
A
conversion of glucose into 2 molecules of ethanol
18
Q
what is lactic acid fermentation?
A
conversion of glucose into 2 molecules of lactate
19
Q
how else can NADH be oxidized?
A
by converting pyruvate to lactate in a reaction catalyzed by lactate dehydrogenase
20
Q
where can fructose come from?
A
table sugar or high-fructose corn syrup
21
Q
where does galactose come from?
A
milk sugar
22
Q
how is fructose metabolized in the liver?
A
by the fructose 1-phosphate pathway
23
Q
how is fructose metabolized in adipose tissue?
A
it is directly phosphorylated by hexokinase
24
Q
what are the key regulators of phosphofructokinase in the liver?
A
- citrate
- fructose 2,6-bisphophate
25
where is GLUT1 located?
all mammalian tissues
26
where is GLUT2 located?
liver and pancreatic beta cells
27
where is GLUT3 located?
all mammalian tissues
28
where is GLUT4 located?
muscle and fat cells
29
where is GLUT5 located?
small intestine
30
what steps in glycolysis make ATP?
- step 6 = phosphoglycerate kinase
| - step 9 = pyruvate kinase
31
what steps in glycolysis change ATP to ADP?
- step 1 = hexokinase
| - step 3 = phosphofructokinase
32
which step in glycolysis oxidizes NAD+ to NADH?
step 5 = glyceraldehyde 3-phosphate dehydrogenase
33
what is gluconeogenesis?
synthesis of glucose from non-carbohydrate precursors
34
where does gluconeogenesis occur?
mainly in the liver, but can occur in the kidney
35
why is gluconeogenesis not a simple reversal of glycolysis?
there are 3 irreversible steps in glycolysis that must be bypassed in gluconeogenesis:
- hexokinase
- phosphofructokinase
- pyruvate kinase
36
how much energy is expended, or spent, in the synthesis of glucose?
2 molecules of ATP
37
the fasting state uses which process?
gluconeogenesis
38
the fed state uses which process?
glycolysis
39
what are the negative regulators in gluconeogenesis?
- F-2,6-BP
- AMP
- ADP x2
40
what are the negative regulators in glycolysis?
- ATP x2
- Citrate
- H+
- Alanine (increased in skeletal muscle breakdown)
41
what are the positive regulators in glucogenesis?
- Citrate
| - Acetyl CoA
42
what are the positive regulators in glycolysis?
- F-2,6-BP
- AMP
- F-1,6-BP
43
what is the role of phosphofructokinase 2 (PFK2)?
kinase that synthesizes fructose-2,6-bisphosphate
44
what is the role of fructose bisphosphate 2 (FBPase2)?
phosphatase that hydrolyzes fructose-2,6-bisphosphate
45
what happens to gluconeogenesis in patients suffering from Type 2 diabetes?
- in type 2, insulin fails to act (aka insulin resistance)
| - causing levels of enzymes to be high, leading to abnormally high levels of blood glucose
46
what is the Cori cycle?
series of reactions that occur in the muscle and liver that display inter-organ cooperation
- lactate is produced by muscle during CONTRACTION
- lactate released into blood
- liver receives blood and removes the lactate to convert into glucose
- glucose then released into the blood
47
where does the citric acid cycle take place?
under aerobic conditions, the MITOCHONDRIA
| - pyruvate enters the mitochondria to be converted into acetyl CoA
48
what are the 2 parts of converting pyruvate to acetyl CoA?
1) citric acid cycle: carbon fuels are completely oxidized with the concomitant generation of high-transfer-potential electrons
2) oxidative phosphorylation: the movement of the high-transfer-potential electrons to oxygen to produce water (redox reactions)
49
what are the 2 principle fates for acetyl CoA?
1) metabolism by the citric acid cycle
| 2) incorporation into fatty acids
50
how is the pyruvate dehydrogenase complex regulated?
by energy charge
- ATP, acetyl CoA, and NADH inhibit the complex
- ADP and pyruvate stimulate the complex
51
what is lactic acidosis?
the process of pyruvate being processed into lactate, due to the inhibition of the pyruvate dehydrogenase complex
- production of lactate in the presence of oxygen is a characteristic of cancer cells
52
what are the clinical symptoms of Beriberi?
inhibited complex activity to the brain, leading to strange behavior
- neuromuscular pathologies
53
what causes Beriberi?
insufficient pyruvate dehydrogenase activity due to thiamine deficiency (aka vitamin deficiency)
54
what is the overall function of the citric acid cycle? (CAC)
harvests high-energy electrons from carbon fuels - oxidizing the acetyl fragment of acetyl CoA to CO2
55
which steps in the CAC that produce NADH?
- step 3 = isocitrate to alpha-ketoglutarate
- step 4 = alpha-ketoglutarate to succinyl CoA
- step 8 = Malate to oxaloacetate
56
which step(s) in the CAC produce FADH2?
step 6 = succinate to fumarate
57
which step(s) in the CAC produce ATP?
step 5 = succinyl CoA to succinate
58
how many ATP are generated from the electrons of NADH?
2.5 ATP
59
how many ATP are generated from the electrons from FADH2?
1.5 ATP
60
what is an anaplerotic reaction?
a replenishing reaction, if/when the energy status of the cells changes
61
explain an anaplerotic reaction in terms of oxaloacetate and pyruvate carboxylase
pyruvate carboxylase is a biotin-dependent enzyme that catalyzes the carboxylation of pyruvate into oxaloacetate
62
what is the outer mitochondrial membrane permeable to?
- most small ions and molecules (due to the channel protein, PORIN)
63
what channel allows for passage of small molecules and ions in the outer mitochondrial membrane?
the voltage dependent anion channel (VDAC)
64
what does the structure of the inner mitochondrial membrane look like?
it is folded into ridges called CRISTAE
65
what is the permeability of the inner mitochondrial membrane?
it's impermeable to most molecules
66
what is the inner mitochondrial membrane a site for?
site of electron transport and ATP synthesis
67
where does the citric acid cycle and fatty acid oxidation occur?
in the mitochondrial matrix
68
what is the reduction potential, or redox potential?
measure of molecule's tendency to donate OR accept electrons
69
what is a strong reducing agent?
readily DONATES electrons and has a NEGATIVE E0′
70
what is a strong oxidizing agent?
readily ACCEPTS electrons and has a POSITIVE E0′
71
how many protein complexes is the electron transport chain composed of?
4 large protein complexes
72
why are the electrons carried by FADH2 not as energy rich as those carried by NADH? what is the consequence of this?
the electrons in FADH2 have a lower reduction potential
| - thus, the electrons pump fewer protons and yield fewer molecules of ATP
73
what are the roles of superoxide dismutase?
scavenges superoxide radicals by catalyzing the conversion of two of these radicals into hydrogen peroxide and molecular oxygen
74
what is catalase and what is its role in the cell?
it is an ubiquitous heme protein that catalyzes the dismutation of hydrogen peroxide into water and molecular oxygen
75
what are the steps in glycolysis where ADP is formed?
- step 1: glucose -> glucose-6-phosphate (hexokinase)
| - step 3: fructose 6-phosphate -> fructose 1,6-bisphosphate (phosphofructokinase)
76
which steps in glycolysis generate ATP?
- step 6: 1,3-bisphosphoglycerate -> 3-phosphoglycerate (phosphoglycerate kinase)
- step 9: phosphoenolpyruvate -> pyruvate (pyruvate kinase)
77
which step in glycolysis generates NADH?
step 5: glyceraldehyde 3-phosphate -> 1,3-bisphosphoglycerate (glyceraldehyde 3-phosphate dehydrogenase)
78
what is the proton-motive force and how does it produce ATP?
it is the proton gradient generated by the oxidation of NADH and FADH2
- this force powers the synthesis of ATP
79
what is the chemiosmotic hypothesis?
proposed that electron transport and ATP synthesis are coupled by a proton gradient across the inner mitochondrial membrane (the coupled pair being oxidation and phosphorylation)
80
what is the purpose and process of the "glycerol 3-phosphate shuttle"?
- introduces NADH into the electron-transport chain
- reduces dihydroxyacetone phosphate to glycerol 3-phosphate
- electron transfer to FAD prosthetic group in membrane-bound glycerol 3-phosphate dehydrogenase reoxidizes glycerol 3-phosphate
- subsequent electron transfer to Q to form QH2 allows these electrons to enter the electron-transport chain
81
what is the purpose and process of "malate-aspartate shuttle"?
- brings electrons from cytoplasmic NADH into the mitochondria in the HEART & LIVER
- consists of 2 membrane transporters and 4 enzymes
82
what does the "ATP-ADP translocase" do?
- enables the exchange of cytoplasmic ADP for mitochondrial ATP
83
what happens when the electron transport is uncoupled from ATP synthesis? what is this called?
heat is generated; it is called non-shivering thermogenesis
84
how is uncoupling facilitated?
in a regulated fashion by uncoupling protein 1 (UCP-1) AKA thermogenin
85
where does rotenone and amytal block in the electron-transport chain?
when NADH-Q oxidoreductase would be converted into QH2
86
which step does antimycin A block in the electron-transport chain?
blocks the reaction where Q-cytochrome c oxidoreductase would be converted to cytochrome c
87
which step does cyanide, azide, and carbon monoxide block in the electron-transport chain?
block the reaction where cytochrome c oxidase would be converted into O2
88
why was 2,4-dinitrophenol (DNP) used as a weight loss drug?
- DNP inhibits ATP synthesis
- causes increased oxygen consumption and energy is released as heat
* increase in metabolic rate & body temp
* can lead to organ failure
89
what is a reducing sugar?
sugars that react with oxidizing agents; they donate electrons
90
what is an O-glycosidic bond?
bond formed between the anomeric carbon of a glucose and a hydroxyl group of an alcohol (oxygen bond)
91
what is a N-glycosidic bond?
bond formed between an anomeric carbon atom of a glucose and the nitrogen from an amine (nitrogen bond)
92
what is an oligosaccharide?
molecule that contains 2 or more monosaccharides linked by O-glycosidic bonds (max is 10 before it's considered technically a polysaccharide)
93
what does glycosyltransferases do?
they are a class of enzymes that catalyze the formation of glycosidic bonds (take sugar and transfer it)
94
what are the different forms of glycoproteins?
1) proteoglycans
| 2) mucins/mucoproteins
95
what is a N-linkage?
the bond that forms between a carb and the nitrogen atom in the side chain of asparagine
96
what is an O-linkage?
the bond that forms between a carb and the oxygen on the side chains of either serine OR threonine
97
how does blood type A come about?
N-acetylgalactosamine is added to the O antigen by a specific glycosyltransferase
98
how does blood type B come about?
the addition of galactose to the O antigen
99
what are the 5 classes of lipids?
1) free fatty acids
2) triacylglycerol
3) phospholipids
4) glycolipids
5) steroids
100
what is the function of free fatty acids?
common fuel
101
what is the function of triacylglycerols?
storage form of fatty lipids
102
what is the function of phospholipids?
membrane lipids
103
what is the function of glycolipids?
membrane lipids composed in part of carbohydrates
104
what is the function of steroids?
polycyclic hydrocarbons with a variety of functions
105
what is meant by the "melting temperature" of fatty acids?
the fluidity
106
what does more unsaturation mean?
greater fluidity, shorter chain, more double bonds
107
why are omega-3 fatty acids important for human health?
offer protection from coronary heart disease, and helps with brain health
108
what is a triacylglycerol?
3 fatty acids esterified to one (1) molecule of glycerol
109
between anhydrous fat stores and hydrated glycogen, which one lasts longer, energy-wise, and by how much?
a gram of anhydrous fat stores last more than 6x than a gram of hydrated glycogen
110
where is triacylglycerol stored?
in adipose tissue
111
what are the common types of membrane lipids?
1) phospholipids
2) glycolipids
3) cholesterol
112
what role does cholesterol play in the cell?
- maintains membrane fluidity
| - precursor to steroid hormone
113
what is the cause of "Hutchinson-Gilford progeria syndrome"?
inappropriate famesylation; the failure to remove a farnesyl group from the nuclear protein
114
what are peripheral membrane proteins?
bound to the POLAR head groups of membrane lipids OR to exposed surfaces of integral membrane proteins
115
how do COX inhibitors work?
they are dependent on a channel connecting the active site to the membrane interior
116
what are the factors involved in transporting small molecules across a membrane?
1) concentration of the molecule is higher on one side of the membrane
2) molecule is lipophilic or soluble in nonpolar solutions
117
what's the difference between lipophilic and hydrophilic (polar) molecules?
lipophilic means the molecules are soluble in nonpolar solutions
- hydrophilic (or polar) means they are soluble in polar and/or water solutions
118
what is a membrane channel?
particular protein that assists polar molecules diffusing across a membrane down their concentration gradient
119
what is facilitated diffusion (aka passive transport)?
it is when molecules move down their concentration gradient to diffuse across a membrane
120
how is the sodium gradient established across the membrane of a cell?
Na+ - K+ pump uses energy of ATP hydrolysis to simultaneously pump 3 Na+ ions out of the cell and 2 K+ ions into the cell against their concentration gradient
121
describe the mechanism of a symporter
it powers the transport of a molecule against its concentration gradient by coupling the movement with the movement of another molecule down its concentration gradient, with both molecules moving in SAME direction
122
describe the mechanism of an antiporter
use one concentration gradient to power the formation of another, but the molecules move in OPPOSITE directions
123
what is digitalis, and how does it work?
it is a cardiotonic steroid that inhibits the Na+ - K+ pump by blocking its dephosphorylation
- it strengthens heart contractions and is used to treat heart disease
124
what are the 2 types of ion channels?
- voltage-activated
| - ligand-activated
125
what is a voltage-activated channel?
a channel that is activated by changes in the voltage across a membrane
126
what is a ligand-activated channel?
a channel that can be activated by the binding of specific molecules to the channel
127
what is a signal transduction cascade?
(1) releases a primary message as a response to a physiological circumstance
(2) reception of the primary message by a receptor
(3) relays the detection of the primary message to the cell interior by the generation of an intracellular second message
(4) activation of effector molecules by the second messenger that results in a physiological response
(5) termination of signal cascade
128
what are the 3 major classes of membrane receptors?
(1) 7 transmembrane receptors associated w/ heterotrimeric G-proteins
(2) dimeric membrane receptors that RECRUIT protein kinases
(3) dimeric protein receptors that ARE protein kinases
