201 Flashcards
(132 cards)
1
Q
metabolism definition
A
collection of coupled and interlinked series of chemical reactions which starts with particular molecule and converts it to some other molecule or molecules
all reactions in a cell
2
Q
main functions of metabolism
A
-extracts biologically useful energy
-synthesise the building blocks of the cell
3
Q
examples anabolic reactions going from simple to complex molecules
A
amino acids to proteins
nucleotides to DNA/RNA
4
Q
What is metabolism?
A
All reactions in a cell; a collection of coupled and interlinked series of chemical reactions that convert a particular molecule to other molecules
5
Q
What are the two types of metabolic reactions?
A
- Catabolic reactions
- Anabolic reactions
6
Q
What do catabolic reactions do?
A
Extract biologically useful forms of energy
7
Q
What do anabolic reactions do?
A
Synthesize complex structures or molecules from simple ones
8
Q
Fill in the blank: Catabolic reactions convert fuels to _______ + H2O + useful energy.
A
CO2
9
Q
What is an example of an anabolic reaction?
A
Amino acid to proteins, nucleotides to DNA/RNA
10
Q
What are the six types of enzyme-catalyzed reactions?
A
- Oxidation-reduction
- Ligation
- Isomerism
- Group transfer
- Hydrolysis
- Lyase reactions
11
Q
True or False: Hydrolysis reactions involve breaking bonds using water.
A
True
12
Q
Define oxidation-reduction reactions.
A
Reactions involving the transfer of electrons
13
Q
What is the role of activated carriers in metabolism?
A
Conserved through evolution to facilitate electron transfer
14
Q
What is the final stage of fuel catabolism?
A
Oxidative phosphorylation
15
Q
What is pyruvate’s role in metabolism?
A
Central point connecting various metabolic pathways
16
Q
What is the significance of the pyruvate dehydrogenase complex?
A
Catalyzes the oxidation of pyruvate to acetyl CoA and CO2
17
Q
What cofactors are required for the pyruvate dehydrogenase complex?
A
- NAD+
- CoA
- FAD
- Lipoamide
- Thiamine pyrophosphate
18
Q
What is the consequence of high concentrations of NADH, acetyl CoA, and ATP on PDH activity?
A
Inhibit PDH activity
19
Q
What disease is related to disrupted pyruvate metabolism?
A
Beriberi
20
Q
Fill in the blank: The enzyme that catalyzes the first step of the citric acid cycle is _______.
A
Citrate synthase
21
Q
What does aconitase do in the citric acid cycle?
A
Interchanges a hydrogen atom and a hydroxyl group
22
Q
What are the outputs of the citric acid cycle?
A
- 2 CO2
- GTP
- 8 electrons
23
Q
True or False: Succinate dehydrogenase is the only enzyme in the citric acid cycle that is bound to the inner mitochondrial membrane.
A
True
24
Q
What is the maximum theoretical ATP yield from one glucose molecule through oxidative phosphorylation?
A
38 ATP
25
Define chemiosmosis.
Process that couples electron transport chains to ATP synthase through a proton gradient
26
What is the role of ATP synthase?
Common currency for the exchange of energy in all living systems
27
Fill in the blank: The total energy stored across the membrane with respect to translocation of solute S is referred to as the _______.
Electrochemical potential
28
What is the effect of uncouplers like DNP on ATP production?
Makes membranes permeable to protons, causing energy to be lost as heat
29
What is the energy stored in an electrochemical gradient across a membrane called?
Electrochemical potential
## Footnote
Given by the equation ΔÛs+ = RT In ([S]I / [S]o) + Zfδe, with units Jmol-1.
30
What effect do uncouplers like DNP have on membranes?
They make membranes permeable to protons
## Footnote
DNP was sold as a weight loss drug but could cause overdose as it uncouples ATP production in all cells.
31
What is the role of electron transport chains (ETC)?
Coupling electron transfer to H+ translocation
## Footnote
Involves redox centers that bind and release electrons.
32
What does a more negative redox potential indicate?
The reduced form has a lower affinity for electrons
## Footnote
This means it is poised to donate electrons.
33
What is the stoichiometry of H+ pumping per electron transferred for most redox centers?
H+/2e-
## Footnote
Most redox centers can transfer 2 electrons.
34
How many protons are pumped per 2 electrons in Complex I?
4 protons
## Footnote
Measured as H+/2e- = 4.
35
What is the terminal acceptor of electrons in the respiratory chain?
O2
## Footnote
The reaction produces water: O2 + 4e- + 4H+ → 2H2O.
36
What does ATP synthase do?
H+ translocation and ATP synthesis
## Footnote
It is evolutionarily conserved across all organisms.
37
What is the significance of the Q cycle in Complex III?
It allows for the oxidation of UQH2 and the pumping of protons
## Footnote
Results in the transfer of 4 protons across the membrane per UQ/UQH2 molecule.
38
What is the primary event of photosynthesis?
Absorption of a photon to excite photosensitive components
## Footnote
Leads to electron transport coupled with H+ pumping.
39
What is the difference between cyclic and non-cyclic electron transport in photosynthesis?
Cyclic involves recycling electrons, while non-cyclic does not
## Footnote
Non-cyclic produces O2 from water splitting.
40
What happens during non-cyclic photosynthesis?
Water splitting releases 2H+ into the lumen
## Footnote
Also involves the reduction of NADP+ to NADPH2.
41
What are the components of ATP synthase?
F1 and Fo
## Footnote
F1 is outside the membrane, while Fo is embedded in the membrane.
42
What occurs when DCCD binds to the ATP synthase?
It blocks the proton channel
## Footnote
Binding to one of the c subunits inhibits H+ translocation.
43
What are redox centers?
Reduced-oxidized pairs that bind and release electrons
## Footnote
They are crucial in the electron transport chain.
44
What is the measured H+/2e- ratio for Complex IV?
2
## Footnote
Indicates the number of protons pumped per two electrons transferred.
45
What is the function of the gamma subunit in ATP synthase?
Couples the opening and closing of nucleotide binding sites
## Footnote
It rotates during ATP synthesis.
46
What is the electrochemical gradient established by?
Proton pumps in the electron transport chain
## Footnote
H+ are pumped from the N side to the P side.
47
What is the structure of the inner mitochondrial membrane?
Impermeable to H+
## Footnote
It has a greatly enhanced surface area compared to the outer membrane.
48
What experimental evidence supported chemiosmotic theory?
Demonstration of pH gradient across thylakoid membrane driving ATP synthesis
## Footnote
Conducted by Andre Jagendorf in 1966.
49
How do chloroplasts differ from mitochondria in terms of H+ pumping?
Chloroplasts pump H+ into the lumen of thylakoids
## Footnote
Mitochondria pump H+ out of the matrix.
50
What is the role of ferredoxin in photosynthesis?
Reduction of NADP+
## Footnote
Transfers electrons back from Fd-NADP+ to cytochrome bf.
51
What is the function of the F1 portion of ATP synthase?
Catalyzes ATP synthesis
## Footnote
The F1 portion is located outside the membrane.
52
Which part of ATP synthase forms the H+ channel?
Fo portion
## Footnote
The Fo portion is embedded in the membrane.
53
What is the sensitivity of the Fo portion to oligomycin?
Sensitive
## Footnote
Oligomycin blocks the H+ channel.
54
How many subunits does the E.coli F-type ATPase have?
3 subunits: a, b, and c
## Footnote
E.coli F-type ATPase is encoded by the unc operon.
55
What binds to the c subunit to block the proton channel?
DCCD
## Footnote
DCCD binding to c inhibits H+ translocation.
56
What is crucial for H+ flow through the Fo portion?
Glutamate or aspartate residues at position 61
## Footnote
All 3 subunits are essential for H+ flow.
57
What mechanism is proposed for the coupling of F1 and Fo?
Rotational catalysis
## Footnote
The y subunit rotates, coupling ATP synthesis.
58
How many protons are required for a full 360-degree rotation of the c subunit?
10 H+
## Footnote
This rotation is linked to ATP synthesis.
59
What is the role of the y subunit during ATP synthesis?
Acts like a crankshaft
## Footnote
It couples the opening and closing of nucleotide binding sites.
60
What are the three states of the F1 binding sites?
Open, Loose, Tight
## Footnote
Each state has different affinities for substrates.
61
What happens in the Tight state of ATP synthase binding sites?
Spontaneous formation of ATP
## Footnote
ATP is tightly bound in this state.
62
In what order does glucose-6-phosphate convert to glucose-1-phosphate?
Catalyzed by phosphoglucomutase
## Footnote
This is the first step of glycogenesis.
63
What enzyme catalyzes the conversion of glucose-1-phosphate to UDP-glucose?
UDP-glucose pyrophosphorylase
## Footnote
This is the second step in glycogenesis.
64
What is the primary function of glucokinase in the liver?
Phosphorylates glucose to trap it inside the cell
## Footnote
This prepares glucose for storage or metabolism.
65
What hormone is released when blood sugar is low?
Glucagon
## Footnote
It is secreted by a-cells of the pancreas.
66
What is the primary energy source for cells without mitochondria?
Glucose
## Footnote
RBCs and some muscle cells rely on glucose for energy.
67
What is the structural characteristic of glycogen?
Highly branched polysaccharide
## Footnote
It consists of glucose linked by a(1-4) and a(1-6) bonds.
68
What enzyme catalyzes the cleavage of a-1-4 glycosidic bonds in glycogen?
Glycogen phosphorylase
## Footnote
It is essential for glycogenolysis.
69
What is the role of insulin in glucose metabolism?
Stimulates glycogen synthesis and glycolysis
## Footnote
Insulin is released when blood sugar is high.
70
True or False: ATP synthesis requires a proton gradient.
False
## Footnote
The H+ electrochemical gradient is not directly needed for ATP synthesis.
71
What does the term isoenzymes refer to?
Multiple forms of the same enzyme
## Footnote
Isoenzymes can prioritize glucose use at different concentrations.
72
What is the process of converting glucose to pyruvate called?
Glycolysis
## Footnote
It is a 10-step pathway that does not require oxygen.
73
What enzyme catalyzes the phosphorylation of fructose-6-phosphate?
Phosphofructokinase
## Footnote
This is a key regulatory step in glycolysis.
74
What is the result of the action of lactase?
Cleaves the b1-4 bond in lactose
## Footnote
This facilitates the digestion of lactose.
75
What is the relationship between glucose and ATP in the liver?
Glucose is phosphorylated to trap it inside for storage or metabolism
## Footnote
This is a critical step in glucose homeostasis.
76
What is the significance of the liver in glucose metabolism?
Acts as a buffer for glucose and controls glucose homeostasis
## Footnote
Absorbed sugars enter the liver via the hepatic portal vein.
77
What happens to glucose-6-phosphate in the kidneys?
It can be converted back to glucose for release into the bloodstream
## Footnote
This prevents excretion of unused glucose-6-phosphate.
78
What is the difference between di and bi in terms of phosphates?
Di – 2 phosphates bound to each other; Bi – 2 phosphorylation not attached to each other
79
What is the product of the reaction catalyzed by fructose 1,6-biphosphate aldolase?
Glyceraldehyde + Dihydroxyacetone phosphate
80
What is the main product desired from the reaction involving dihydroxyacetone phosphate?
Glyceraldehyde 3-phosphate
81
What enzyme catalyzes the conversion of dihydroxyacetone phosphate to glyceraldehyde 3-phosphate?
Triosephosphate isomerase
82
What is the role of pyruvate kinase in glycolysis?
Regulates conversion of phosphoenolpyruvate to pyruvate
83
Which allosteric regulators downregulate pyruvate kinase?
ATP, Citrate, Alanine, Fatty acids
84
What stimulates the activity of pyruvate kinase?
Phosphoenolpyruvate and fructose 1,6-bisphosphate
85
How many forms of isozymes does pyruvate kinase have?
Two forms: L type in liver and M type in muscle
86
What is the significance of phosphofructokinase in glycolysis?
It is the first control step and the first committed step
87
What are the three irreversible steps in glycolysis that gluconeogenesis must overcome?
Pyruvate to phosphoenolpyruvate; Fructose 1,6-bisphosphate to Fructose 6-phosphate; Glucose 6-phosphate to Glucose
88
What is gluconeogenesis?
An energy inefficient process that synthesizes glucose from non-carbohydrate sources
89
What are the conditions under which gluconeogenesis can occur?
Availability of precursors, spare energy (ATP and GTP), presence of necessary enzymes
90
What is the role of pyruvate carboxylase in gluconeogenesis?
Catalyzes the conversion of pyruvate to oxaloacetate
91
What is the net energy cost of gluconeogenesis compared to glycolysis?
Gluconeogenesis requires 6 high energy phosphate bonds to produce 1 molecule of glucose
92
What is fructose-2-6-bisphosphate's role in glycolysis and gluconeogenesis?
Stimulates glycolysis and inhibits gluconeogenesis
93
What is the purpose of the Cori cycle?
To allow liver and skeletal muscle to cooperate metabolically
94
What is the induced fit model in enzymology?
Enzymes change shape to better fit substrates, promoting catalysis
95
What are coenzymes?
Organic cofactors that participate in chemical group transfer reactions
96
What is the Michaelis-Menten equation used for?
To describe the rate of enzyme-catalyzed reactions
97
What is competitive inhibition?
Inhibitor competes with substrate for active site
98
What is the effect of uncompetitive inhibition on K_m and V_max?
Both K_m and V_max change
99
What is the Cleland notation used for?
To organize reactions involving multiple substrates
100
What is the significance of the turnover number (K_cat) in enzyme kinetics?
It indicates the maximum number of substrate molecules converted to product per enzyme molecule per unit time
101
What does the Lineweaver-Burk plot help to determine?
It helps to extrapolate data from the Michaelis-Menten plot
102
What is the role of cofactors in enzymatic reactions?
They are non-protein components essential for enzyme activity
103
What are the two types of cofactors?
Prosthetic groups (tightly bound) and co-substrates (loosely bound)
104
What is the role of succinate dehydrogenase in the electron transport chain (ETC)?
It is an enzyme involved in the ETC.
105
What does UQ stand for in the context of the electron transport chain?
Ubiquinone
106
How can Lineweaver plots be used in enzyme kinetics?
To differentiate bisubstrate mechanisms.
107
What is a characteristic of Ping-pong bi-bi reactions regarding Km values?
Differing Km values because substrate A modifies the enzyme into a different form for substrate B to bind.
108
What is the relationship between substrates in Sequential Bi-Bi reactions?
They share Km because both substrates bind to the same enzyme.
109
Define Km in the context of enzyme kinetics.
Enzyme affinity to a substrate.
110
What does Kcat represent in enzyme kinetics?
Enzyme's turnover rate, indicating the number of catalytically enhanced reactions per second at maximum efficiency.
111
What is the range of Kcat values?
From 10 to 10^8 s^-1.
112
What is the purpose of pre-steady state kinetics?
To analyze the rate constant during the slowest step of catalysis, involving many reaction intermediates.
113
What is a typical apparatus used for measuring pre-steady state kinetics?
Stopped-flow apparatus.
114
What is the function of a quench-flow apparatus?
To stop reactions at precise times and measure levels of reactants or products using non-optical methods.
115
What is the main characteristic of allosteric regulation?
Binding of a small molecule to a site other than the enzyme's active site, causing a conformational change.
116
What are the two types of modulators in allosteric regulation?
Positive and negative allosteric modulators.
117
What is the structure of E.coli ATCase?
12 subunits consisting of 6 catalytic and 6 regulatory subunits.
118
What is the significance of feedback loops in allosteric enzymes?
They regulate enzyme activity based on the concentration of end products like CTP and ATP.
119
What are the two states of allosteric enzymes?
T (tense, less active) and R (relaxed, more active).
120
What does phosphorylation do to an enzyme?
It can increase or decrease its activity.
121
List some types of covalent modifications besides phosphorylation.
* Methylation
* Uridylylation
* Adenylation
* ADP-ribosylation
* Acetylation
* Ubiquitination
122
What is the role of kinases in phosphorylation?
Enzymes that phosphorylate other molecules.
123
What are the common amino acid residues where phosphorylation occurs?
* Serine
* Threonine
* Tyrosine
124
What is the function of phosphatases?
To reverse phosphorylation by removing phosphate groups.
125
What is the impact of high AMP levels in a cell?
Signals to AMPK to restore the cell's energy balance.
126
What is the structure of AMPK in mammals?
Trimeric, consisting of alpha, beta, and gamma subunits.
127
What are the three types of lipids mentioned in adipocytes?
* Neutral lipids (triacylglycerols)
* Polar lipids (phospholipids)
* Steroids (cholesterol)
128
What happens to triacylglycerol after ingestion?
It forms micelles, is broken down to fatty acids, and is absorbed in the gut.
129
How is hormone-sensitive lipase activated?
Through the activation of G-proteins and subsequent phosphorylation by protein kinase A.
130
What Nobel Prize was awarded in 1994 and for what discovery?
For the discovery of G-proteins and their role in signal transduction.
131
What is the process of fatty acid oxidation in mitochondria?
Involves four reactions: oxidation, hydration, oxidation, and cleavage.
132
Fill in the blank: The first step to activate fatty acids for mitochondrial entry is the addition of _______.
CoA.
