Quiz 3 Flashcards
(168 cards)
1
Q
Do exergonic processes reach equilibrium or go to completion
A
they reach equilibrium
2
Q
How much glucose 6-phosphate and glucose 1- phosphate will be present at equilibrium
A
95 % of glucose 6-phosphate and 5% glucose 1-phosphate
3
Q
at equilibrium, the number of reactant molecules being converted to products equals to what
A
it equals the number of molecules being converted back to reactants
4
Q
ATP hydrolysis is exergonic because it is:
A
1- A decrease in potential energy
2- an increase in entropy
5
Q
why is there less potential energy in ADP than in ATP
A
because the loss of the terminal phosphate has decreased the electrical repulsion among the negatively charged oxygen atoms of the phosphate groups
6
Q
What is ATP hydrolysis
A
ATP + H2O –> ADP + P
7
Q
What does ATP consist of
A
- a five carbon sugar (ribose)
- nitrogenous base (adenine)
- 3 phosphate groups
8
Q
what is the specific form of chemical energy that most often links the two types of pathways
A
ATP
9
Q
ATP is a source of _______ as a result of its reaction with __________
A
free energy
water
10
Q
what are the products of ATP hydrolysis
A
- adenosine diphosphate
- molecule of inorganic phosphate
11
Q
what is the delta G of ATP hydrolysis
A
-7.3 kcal/mol
12
Q
glutamine is an endergonic process, yet molecules of glutamine are synthesized within our cells all the time. How is that possible ?
A
during metabolism, glutamine is synthesized through a process called energy coupling: an endergonic reaction occurs by being coupled to an exergonic reaction (ATP hydrolysis)
13
Q
why is energy released in a catabolic (breakdown) pathway
A
because the free energy of the final products of the pathway is less than the free energy of the starting molecule
14
Q
catabolic pathways fuel …
A
anabolic pathways
15
Q
why do anabolic or biosynthetic pathways require energy
A
the free energy of the products is greater than the free energy of the starting molecule
16
Q
catabolic and anabolic pathways are linked through …
A
chemical energy (ATP)
17
Q
How do catalysts work (loosely)
A
speed up reactions by bringing down the activation energy
18
Q
does the catalyst take part in the reaction
A
no.
19
Q
what are the most common biological catalysts
A
enzymes: they lower the activation energy of a reaction
20
Q
what are the three general ways enzymes accelerate reactions by inducing the transition state
A
- bringing the reacting molecules together (binding to an enzyme’s active site brings the reactants together in the right orientation for catalysis to occur
- Exposing the the reactant molecule to altered charge environments that promote catalysis (alters substrate)
- changing the shape of substrate molecule (conformation that mimics transition state)
21
Q
what are cofactors
A
a nonprotein, non organic group that binds to the enzyme to help it out (often minerals and metals)
22
Q
do you need a lot of metals like iron, copper, zinc or manganese in your body?
A
No but its necessary for enzymatic activity (ex: hemoglobin needs Fe to bond O2
23
Q
what are coenzymes
A
a type of cofactor that is an organic molecule, often derived from vitamins
24
Q
what happens if the amount of enzymes in a reaction increases
A
the rate increases
25
what happens if the amount of substrate in a reaction increases
the rate increases, but plateaus because there is too much substrate for the enzymes
26
What affects enzyme activity
1. enzyme and substrate concentration
2. competitive regulation
3. noncompetitive regulation
4. pH
5. temperature
27
what is competitive regulation
the competitive inhibitor molecule competes with the substrate for the active site
28
what is noncompetitive allosteric regulation
activation: the binding activator converts enzyme from low to high affinity state
inhibition: opposite
29
what are the three main catabolic pathways and what are their theoretical yield
- aerobic respiration(with oxygen): 1 molecule of glucose yields between 36 and 38 ATPs
- anaerobic respiration(w/out oxygen): 1 molecule of glucose yields between 2 and 36 ATPs
- fermentation (backup system) : 1 molecule of glucose yields 2 ATPs
30
which catabolic pathway(s) has the Krebs cycle and the electron transport chain
aerobic and anaerobic respiration
31
what are redox reactions
all chemical reactions in which atoms have their oxidation state changed. Often involve the transfer of electrons between chemical species.
32
Oxidation is the ______ of electrons or an __________ in oxidation state by a molecule, atom or ion.
loss
increase
33
Reduction is the ______ of electrons or an __________ in oxidation state by a molecule, atom or ion.
gain
decrease
34
what is the ultimate source of energy-rich carbon compounds found in carbohydrates, fats and proteins
photosynthesis
35
how is carbon reduced into glucose in photosynthesis
light energy is used to extract electrons from water; the electrons then combine with hydrogen to reduce carbon.
36
What is one of the major by-products of photosynthesis
oxygen, which is later used in cellular respiration.
37
what happens O2 and glucose in cellular respiration
glucose is oxidized into CO2
O2 is reduced into water
38
how can we define cellular respiration
As the collection of metabolic reactions within cells that breaks down food molecules
39
What is life and its systems driven by
a cycle of electron flow that is powered by light in photosynthesis and oxidation in cellular respiration
40
What are the three phases of cellular respiration
1. Glycolisis
2. Pyruvate oxidation and the citric acid cycle
3. oxidative phosphorylation
41
In what domains of life can glycolysis be found
Archaea, bacteria and eukarya
42
Does glycolysis depend upon the presence of O2
No
43
Where does glycolysis occur?
In the cytosol of all cells, using soluble enzymes and therefore does not require more sophisticated ETCs and internal membrane systems to function (no mitochondria)
44
What does glycolysis consist of
10 sequential enzyme catalyzed reactions that lead to the oxidation of the six-carbon sugar glucose
45
what does glycolysis produce
2 molecules of the three carbon compound pyruvate
46
the potential energy released in the oxidation of glycolysis leads to the synthesis of...
NADH and ATP (3ATP/NADH after ETC)
47
explain the energy investment/payoff in glycolysis
there is an initial 5 step energy requiring phase, followed by a five step energy releasing phase. It costs 2 ATPs, and produces 4 (6 after ETC)
48
what is NADH
a coenzyme found in all living cells. It is dinucleotide because it is 2 nucleotides joined through their phosphate group(one has adenine, the other nicotinamide).
49
What is ATP generated by
a substrate level phosphorylation (specific enzyme; pyruvate kinase)). A phosphate group is transferred from a high energy donor directly to ADP, forming ATP. Also used in citric acid cycles
50
What type of enzymes can be found in glycolysis
- kinases
- mutases
- isomerases
- dehydrogenases
- enolase
51
What is the role of kinase
transfers phosphate between ATP and another molecule
52
What is the role of mutase
transfer functional groups from one position to another within the same molecule
53
What is the role of isomerases
changes a molecules conformation
54
What is the role of dehydrogenase
removes a hydrogen form the substrate (NAD+ ---> NADH)
55
What is the role of enolase
removes water from the substrate
56
do bacteria and archaea still have respiratory ETCs
yes, many do. they are located on internal membrane systems derived from plasma membranes
57
How do bacteria and archaea "breath" in hot springs and hydrothermal vents
they have respiratory chains that use a molecule other than O2 as the electron acceptor and are said to possess anaerobic respiration.
58
what are commonly used terminal electron acceptors instead of O2
SO4 2-, NO3 - and Fe 3+
59
why did aerobic respiration evolve to be the dominant form of respiratory metabolism
because, by being highly electronegative, O2 has a greater affinity for electrons than any other electron acceptor
60
what is the result of low oxygen levels in eukaryotic cells
fermentation
61
what happens after glycolysis if oxygen is abundant
the pyruvate and NADH produced by glycolysis are transported into mitochondria, where they are oxidized using the citric acid cycle and the ETC
62
what happens after glycolysis if oxygen is absent
The pyruvate remains in the cytosol, where it is reduced, consuming the NADH generated by glycolysis in fermentation.
63
What and where does alcohol fermentation happen
where: yeast (single cell fungi)
what: pyruvate is reduced to ethyl alcohol as CO2 is released and NADH is oxidized to NAD+
64
What enzymes are involved in alcohol fermentation
- pyruvate decarboxylase
- alcohol dehydrogenase
65
What and where does lactate fermentation happen
where: many bacteria and some plant and animal tissues
what: pyruvate is converted into the three carbon molecule lactate = lactic acid (lactate dehydrogenase)
66
when does lactate fermentation happen
when vigorous contractions of muscle cells calls for more oxygen than the circulating blood can supply
67
what enzymes are involved in the energy requiring phase of glycolysis and what reaction is associated to it
1. hexokinase - phosphorylation reaction
2. phosphoglucomutase - rearranged into its isomer
3. phosphofructokinase - phosphorylation
4. aldolase - hydrolysis (splits in 2)
5. triosephosphate isomerase - isomerization reaction
68
what enzymes are involved in the energy releasing phase of glycolysis and what reaction is associated to it
6. triosephosphate dehydrogenase - NAD+ to NADH
7. phosphoglycerate kinase - substrate-level phosphorylation
8. phosphoglyceromutase - shifting of chemical group
9. enolase - water cleaved
10. pyruvate kinase - remaining phosphate group removed
69
What happens to pyruvate, in the mitochondria
It is oxidized to an acetyl group (two carbons), which is carried to the citric acid cycle by CoA.
70
In the pyruvate oxidation, what is the third carbon released as
CO2
71
The acetylene group carried away by CoA is the ________ for the citric acid cycle
fuel
72
what is the pyruvate oxidation
a multi-step process that converts pyruvate into acetyl-CoA , once it is in the matrix.
73
what is the first step of pyruvate oxidation
a decarboxylation reaction whereby the carboxyl group of pyruvate is lost as carbon dioxide (dehydrogenation)
74
what is the second step of pyruvate oxidation
transfer of two electrons and a proton to NAD+, forming NADH
75
what is the third step of pyruvate oxidation
the acetyl group reacts with coenzyme A to form the high energy intermediate acetyl-CoA.
76
what is the goal of the reactions that make up the citric acid cycle
liberating the electrons in the C-H bonds of the acetyl-CoA as a source of chemical energy
77
What does the citric acid cycle consist of
eight enzyme-catalyzed reactions: 7 are soluble enzymes located in the mitochondrial matrix, and one is bound to the matrix side of the inner mitochondrial membrane
78
What is the result of the citric acid cycle
the oxidation of acetyl groups to carbon dioxide accompanied by the synthesis of ATP; NADH; and FAD (reduced from FADH2)
79
How many carbons, NADH, FADH2 and ATP are yielded for two turns of the citric acid cycle
Carbons (dioxide): 4
NADH: 6
FADH2: 2
ATP: 2
80
Why are there two turns of the citric acid cycle
because 1 molecule of glucose is converted to 2 pyruvate, which are both converted to acetyl-CoA.
81
what stage of respiration do the remaining carbons that were originally in glucose at the start of glycolysis convert into carbon dioxide
the citric acid cycle
82
Besides ATP, where does the potential energy originally present in glucose exist after the citric acid cycle?
in molecules of NADH and FADH2
83
what is the role of the ETC coupled with chemiosmosis?
to extract the potential energy in NADH and FAH2 and synthesize more ATP
84
How does the electron transport system work
electrons move spontaneously down a potential energy gradient from one complex to the next. The release of energy (from NADH and FADH2) is used to pump protons into the inter membrane space
85
How does chemisomosis work
ATP synthase catalyzes ATP synthesis using energy from the H+ gradient across the membrane.
86
what does UQ stand for
ubiquinone (coenzyme Q) (positive electron carrier
87
what does Cyt c stand for
cytochrome c (hemeprotein) (positive electron carrier)
88
what goes in and out of complex 1 (4H+)
in: NADH
out: NAD+
89
What goes in and out of complex II
in : FADH2
out: FAD
90
What is reduced at complex IV (2H+)
O2 is reduced to H2O
91
which complex is a single peripheral membrane protein
complex II
92
How do certain electrons bypass complex I
by complex II, which passes electrons to ubiquinone
93
what are prosthetic groups
sort of like coenzymes, bind to the complexes (not II) very precisely to allow for e- transport. they are redox-active cofactors. (they switch form oxidized to reduced)
94
describe the journey of the prothetic group FMN of complex I
it is reduced by electron donation from NADH on the matrix side of the inner membrane
FMN then donates e- to the Fe/S prosthetic group, which in turn donates them to ubiquinone.
this continues until e- are donated to oxygen, where it is reduced to water.
95
how are the prosthetic groups and electron carriers organized
from hight to low free energy, therefore mvt along the chain is thermodynamically spontaneous down a free energy gradient
96
does electron transport from NADH/FADH2 to oxygen produce ATP
no, the energy that is released during electron transport is used to do the work of transporting protons across the inner mitochondrial membrane
97
how is ATP synthase a molecular motor
protons move through a channel between the basal unit and the stator, making the stalk and headpiece spin (like a propeller)
98
what is the definition of chemiosmosis
the ability of cells to use the proton-motive force to do work
99
what is the mode of synthesis that is linked to the oxidation of energy-rich molecules by an ETC called
oxidative phosphorylation (last step of cellular respiration)
100
what is the difference between substrate level phosphorylation and oxidative phosphorylation
oxidative phosphorylation relies on the action of a larger multi protein complex that spans the inner mitochondrial membrane called ATP synthase
101
what does the rate of ATP generation match
the requirements of the cell for chemical energy
102
what happens if there is an excess of ATP present in the cytosol
ATP, an allosteric enzyme, binds to phosphofructokinase and inhibits its activity, resulting in a slowing down or stop of glycolysis
103
if ATP is an allosteric inhibitor to fructokinase, what is ADP
an allosteric activator
104
theoretically, how many ATP do we get for each oxidized glucose and where do they come from
glycolysis: 2
Citric acid cycle: 2
oxidative phosphorylation: 34
total: 38
105
what are the three reasons the actual ATP yield is different form the theoretical yield
1. NADH (from glycolysis) transport costs 1 ATP/NADH, so 2 ATP/glucose
2. pyruvate transport needs 2nd active transport and uses H+
3. intermitochondrial matrix is leaky, so there is a loss of H+
106
how many H+ are pumped into the inter mitochondrial membrane for each NADH that is oxidized
10
107
how many molecules of ATP are synthesized for every NADH oxidized by the ETC
between 2.5 and 3.3
108
How many ATP are synthesized for every FADH2 oxidized by the ETC
about 2
109
What is the theoretical maximum yield from the complete oxidation of one mole of glucose
36 moles of ATP
110
what other carbohydrate can enter glycolysis at early steps because they're easy to break down
sucrose and other disaccharides that can be broken down to fructose and glucose
111
how is glycogen an early substrate in glycolysis
its broken down and converted by enzymes into glucose-6-phosphate
112
where do 2 carbon fragments of of fatty acids and lipids enter the citric acid cycle
they enter as acetyl-CoA
113
what are alanine, leucine and phenylalanine ( amino acids) converted to upon entering the citric acid cycle
a: pyruvate
l: acetyl units
p: fumarate
114
what are the intermediates of glycolysis and the citric acid cycle also used as
the starting substrates for the synthesis of amino acids, fats and the pyrimidine and purine bases need for nucleic acid synthesis.
115
what supplies the carbon backbones for the array of hormones, growth factors, prosthetic groups and cofactors that are essential to cell function?
the respiratory intermediates
116
what happens to excess acetyl-CoA
it can be removed from the respiration and used to synthesize the fatty acids needed for a range of cellular processes
117
what happens if glucose levels are low in the body
new glucose can be synthesized through glycogenesis
118
what are the substrates of glycogenesis
- glycogenic amino acids
- glycerol
- pyruvate and lactate
119
when is glycogenesis the reverse process of glycolysis
when it starts with pyruvate
120
to be used a source of energy, photons of light must be ________
absorbed/captured
121
what does absorption occurs
when the energy of a photon is transferred to an electron within a molecule, moving to electron from ground state to an excited state.
122
is the electron farther or closer to the nucleus in the excited state
farther
123
what are earths primary producers
photoautotrophic organisms bcthey generate organic compounds that are consumed by other organisms (the consumers)
124
how many membranes does chloroplast have
3
125
is photosynthesis found in cyanobacteria chemically different from the one found in the chloroplast of plant leaves
no, its identical
126
what is the aqueous environment within the inner membrane of a plant
the storm of the chloroplast
127
what is the third membrane system in plants
the thylakoids membranes, form flattened closed sacs
128
what is the space enclosed in the thylakoids called
the thylakoid lumen
129
what is embedded within the thylakoid membrane
the reactions that carry out photosynthesis: proteins, pigments, ETC and ATP synthase
130
where are the enzymes that catalyze the reactions of the Calvin cycle located
in the stroma of the chloroplast
131
what does chloroplast synthesize vs mitochondria convert
c: carbohydrates
m: carbohydrates into ATP
132
what do the light reactions involve
- the capture of light energy by pigment molecules
- the utilization of that energy to synthesize both NADPH and ATP
133
where do the electrons needed to reduce NADPH come from and what do they result in
they come from the oxidation of h2o and result in the release of o2
134
what type of reaction is photosynthesis
a redox (reduction of co2 to ch2o and oxidation of h2o to o2)
135
what er the two light-trapping components involved in photosynthetic electron transport
photosystem I and photosystem II (depend on sunlight)
136
what kind of reactions are the Calvin cycle, the hatch slack cycle, photorespiration and CAM photosynthesis
dark reaction (don't depend on sunlight)
137
What is the first fate of light and atomic excitation
e- returns to ground state by emitting a less energetic photon (fluorescence) or releasing energy as heat.
138
what is the second fate of light and atomic excitation
e- returns to ground state as its energy is transferred to an e- in a neighbouring pigment
139
what is the third fate of light and atomic excitation
the high energy e- is transferred to another molecule, an e- acceptor
140
which fate is not involved in photosynthesis
the first one
141
how do chlorophyll a and b differ
a : CH3 methyl
b: CHO aldehyde
142
which chlorophyll is most abundant
a
143
what do chlorophyll a and b both have that increases the mvt of e-
double bonds, fully conjugated so resonance
144
what are the peaks of chlorophyll a on the absorption spectrum
435 and 685 nm
145
what are the peaks of chlorophyll b on the absorption spectrum
480 and 645 nm
146
what are the peaks of carotenoids on the absorption spectrum
450 and 500 nm
147
how can you determine the wavelengths of light absorbed by a pigment such as chlorophyll a
producing an absorption spectrum using a spectrophotometer and a sample of the pigment
148
what does the absorption spectra of accessory pigments (chlorophyll b and carotenoids) illustrate
that these pigments expand the wavelengths of light that can be effectively captured and used for photosynthesis
149
what is an absorption spectrum
a plot of the absorption of light as a function of wavelength
150
what does a group of pigment proteins form
an antenna complex that surrounds a reaction center
151
what happens in the reaction center
the absorbed light is transferred to chemical energy when an excited e- from the chlorophyll a is transferred to a primary acceptor
152
what happens to the high energy e- after they are passed out of the photosystem
they are passed to the electron transport system
153
how does the ETC work in chloroplast
same as in mitochondria: e- flows spontaneously from molecules that are easily oxidized to molecules that are progressively more reduced
154
in the (Z) non-cyclic photophosphorylation, do e- start at photosystem I or II
II
155
why is the specialized clorophyll a in the reaction center of photosystem I called P700
because the absorption maximum is at a wavelength of 700nm
156
what is the absorption maximum of specialized chlorophyll a in photosystem II
680nm
157
are the chlorophyll molecules in photosystem I and II easily oxidized
no
158
Why is the photon light used to excite e- in photosystem I and II
to make them easier to oxidize by the ETC.
159
what happens when a second photon of light is absorbed by photosystem I
it forms p700 which is easily oxidized by the primary e- acceptor of photosystem I and in turn ferredoxin, before the e- is donated to NADP+
160
how is the energy of NADP+ being over p700 overcome
photosystem I absorbs a photon of light producing p700
161
why do we normally transport electrons
to build/create a proton gradient
162
what is the first step to building a proton gradient (photosynthesis)
protons are translocated into the lumen by the cyclic reduction and oxidation of plastoquinone as it migrates from photosystem II to the cytochrome complex and back again
163
what is the second step to building a proton gradient (photosynthesis)
the gradient is enhanced by the addition of two protons to the lumen from the oxidation of water, which occurs on the luminal side of photosystem II
164
what is the third step to building a proton gradient (photosynthesis)
the removal of one proton from the stroma for each NADPH molecule synthesized further decreases the H+ concentration in the stroma, thereby enhancing the gradient across the thylakoid membrane
165
what is used to generate ATP in the light reaction
chemiosmosis
166
cyclic electron transport
involves only photosystem I, e- flow from photosystem I to ferrodoxin is not followed by e- donation to NADP+ reductase complex. Instead, reduced ferrodoxin donates e- back to the plastoquinone pool.
167
what happens to the plastoquinone pool in cyclic photophosphorylation
it gets continually reduced and oxidized and keeps moving protons across the thylakoid membrane without the involvement of e- coming from photosystem I
168
is NADPH formed during cyclic photophosphorylation
no
