Chapter 8,9 Flashcards
(127 cards)
1
Q
what is metabolism?
A
all of the reactions that build up and break down organic molecules in an organism
2
Q
what is major form of chemical energy used by cells?
A
ATP
3
Q
what is catabolism?
A
breakdown of molecules into smaller units
4
Q
what is anabolism?
A
building of molecules from smaller units
5
Q
what kind of metabolism requires ATP?
A
the building up of molecules by forming chemical bonds requires energy in anabolism
6
Q
what kind of metabolism produces ATP?
A
the breakdown of molecules and breaking of chemical bonds supplies enough energy for the anabolic reaction of ATP synthesis to occur
7
Q
what is energy?
A
the capacity to cause change or do work
8
Q
what are two major types of energy?
A
kinetic and potential energy
9
Q
what does potential energy depend on?
A
structure of object and/or position within its surroundings
10
Q
what do the bonds linking phosphate groups in ATP have?
A
high chemical potential energy
11
Q
why does the cell not breakdown ADP into AMP further?
A
the second phosphate group is more difficult to remove and requires more energy to break the bond.
energetically unfavourable
12
Q
what type of energy is present in molecular covalent bonds?
A
chemical potential energy
13
Q
what is the first law of thermodynamics?
A
energy is conserved - it cannot be created or destroyed
14
Q
what is the second law of thermodynamics?
A
energy transformations always result in an increase in disorder/entropy in the universe
15
Q
why are energy transformations never 100% efficient?
A
some energy is lost, usually in the form of heat. energy available to do work decreases
16
Q
what is Gibbs free energy?
A
amount of energy in a system available to do work
17
Q
what is ΔG?
A
ΔG = Gp - Gr
18
Q
what are exergonic reactions?
A
-ΔG release energy, releases energy
19
Q
what are endergonic reactions?
A
+ΔG release energy, absorbs energy
20
Q
how is a reaction spontaneous?
A
the reaction is energetically favourable and happens on its own
21
Q
why are catabolic reactions exergonic?
A
products have less chemical energy, meaning ΔG is negative, products are more disordered/ have more entropy
22
Q
why are anabolic reactions endergonic?
A
products have more chemical energy, meaning ΔG is positive. products are less disordered/have less entropy
23
Q
what kind of reaction is ATP hydrolysis?
A
exergonic, spontaneous, catabolic
24
Q
how can energetic coupling drive nonspontaneous reactions?
A
a spontaneous reaction can drive a nonspontaneous reaction to occur by providing it with energy, making overall reaction thermodynamically favourable
25
what is an example of energetic coupling?
ATP drives nonspontaneous reactions such as synthesis of a macromolecule from smaller units
26
how do enzymes speed up chemical reactions?
enzymes lower activation energy and stabilizing transition state
enzymes also bind to multiple reactants and keep them in close proximity, allowing them to interact
27
what is a transition state?
unstable state in which old bonds are breaking and new ones are forming, therefore having large amount of free energy
28
what is activation energy?
an input of energy that every reactant requires to reach transition state
29
how do enzymes determine whether or not a reaction goes forward or backward?
- Following the equilibrium constant and the relative concentrations of reactants and products.
- Coupling the reaction with another reaction that is energetically favorable.
- Regulating their own activity or expression by various mechanisms.
30
what is an enzyme's active site?
part of enzyme that binds substrate and converts it to the product
31
what does the active site do?
active site brings substrates into close proximity in correct orientation, interactions btwn active site and substrates help to stabilize transition state and lower activation energy required for reaction
32
what are catalytic amino acids?
amino acids that when protein is folded properly, forms the active site
33
what are cofactors and coenzymes?
nonprotein helpers which bind to proteins and function in catalysis by activating protein/enzyme, allowing it to perform its function
34
what are cofactors?
inorganic ions such as iron zinc copper etc.
35
what are coenzymes?
organic molecules such as vitamins
36
what is an enzyme inhibitor?
chemical that decreases enzyme's activity
37
what is competitive inhibition?
inhibitor binds to active site
38
what is non-competitive inhibition?
binding sites of inhibitors and substrates are different, binding of a non-competitive inhibitor causes decrease in rate at which enzyme converts substrate to product by changing shape of enzyme
39
which type of inhibition is usually non-reversible?
non-competitive inhibition
40
what are metabolic pathways?
chemical reactions that are organized in a way in which a molecule is altered in a series of steps, each catalyzed by a specific enzyme, to form a final product
41
what is feedback inhibition?
a product may act as an inhibitor for one of the enzymes earlier in the pathway, blocking its own production
42
what is the advantage of using a feedback inhibition system to a cell?
prevents waste and overproduction, the starting material is not wasted
43
what is an allosteric enzyme?
type of enzyme that is activated or inhibited when binding to another molecule causing its shape to change
44
what is cellular respiration?
metabolic pathway converting energy stored in organic fuel molecules
45
what is overall energy yield of one glucose molecule?
around 30 ATP
46
what happens to the carbons in glucose?
become oxidized into CO₂
47
are fuel molecules COMPLETELY broken down in glycolysis and pyruvate oxidation (step 1 and 2)?
NO, partially broken down
48
are fuel molecules COMPLETELY broken down in the citric acid cycle?
YES, completely broken down into CO₂
49
why do oxidation and reduction reactions always occur together?
when a substance loses electrons, another substance must gain those electrons
50
what are oxidizing agents?
electron acceptors, become reduced
51
what are reducing agents?
electron donors, become oxidized
52
do redox reactions always occur with electron transferring?
NO, redox reactions can also involve a change in the degree of electron sharing between atoms
53
why is oxygen a good oxidizing agent?
it is very electronegative
54
how does an electron lose potential energy?
when it shifts from a less electronegative atom to a more electronegative one
55
why does methane have more potential energy than carbon dioxide?
methane has less electronegative atoms compared to CO₂, which has oxygen, a very electronegative atom
56
what are the electron carriers in cellular respiration?
NAD+ and FAD
(nicotinamide adenine dinucleotide and flavin adenine dinucleotide)
57
what is the purpose of hydrogen anions in cellular respiration?
represents electrons, used as electron carriers because electrons cannot be transferred by themselves
58
how do you extract energy from molecules?
you oxidize them
59
why are carbon atoms in glucose oxidized in cellular respiration?
carbon atoms in glucose share their electrons equally with other atoms
electrons are NOT shared equally in CO₂, carbon does not attract electrons as strongly as oxygen does, meaning carbon atoms partially LOST electrons to oxygen and OXIDIZED
60
why are oxygen atoms in water reduced in cellular respiration?
O atoms in O₂ share electrons equally
electrons are NOT shared equally in H₂O, oxygen attracts electrons from H more, meaning oxygen atoms have partially GAINED electrons and is REDUCED
61
what does it mean when an atom has partially gained electrons?
atom attracts electrons from other atom in the bond, gaining the electrons in a way, meaning it is reduced
62
what does it mean when an atom has partially lost electrons?
atom does not attract electron as strongly as the other atom in the bond, losing the electrons in a way, meaning it is oxidized
63
how does NAD+ accept electrons from glucose?
enzyme dehydrogenase removes a pair of hydrogen atoms (represents electrons) from glucose, oxidizing it
hydrogen atoms are transferred to NAD+, reducing it to NADH because it gained the electrons
64
what is the definition of glycolysis?
"splitting of sugar" , breaking down 6-carbon glucose into TWO (2) molecules of 3-carbon pyruvate
65
is glycolysis aerobic?
NO, glycolysis does not have O₂ as a reactant, meaning the process can occur in the absence of oxygen.
66
where does glycolysis occur?
in the cytosol of the cytoplasm
67
what are the three phases of glycolysis?
the preparatory phase, steps 1 -3
the cleavage phase, steps 4 - 5
the payoff phase, steps 6 - 10
68
what is the net yield of energy in glycolysis?
2 ATP, 2 NADH, 2 Pyruvat
69
what occurs in the prep phase of glycolysis?
glucose is prepared by adding 2 phosphate groups, producing fructose 1,6-bisphosphate, needing 2 ATP
70
what occurs in the cleavage phase of glycolysis?
fructose 1,6-bisphosphate is split into two molecules of glyceraldehyde 3-phsphate
71
what occurs in the payoff phase of glycolysis?
enzyme transfers a phosphate group from phosphoenolpyruvate into ADP, producing ATP and pyruvate.
Four ATP, two pyruvate molecules and two NADH molecules are formed
72
what is substrate-level phosphorylation?
enzyme transfers a phosphate group from an organic molecule containing a phosphate molecule to ADP, producing ATP
energetic coupling, using energy from a catabolism reaction to drive the reaction of an anabolism reaction
73
is glucose the only sugar that can contribute to glycolysis?
NO, other sugars can be converted into glycolysis intermediates that come later in the pathway
(e.g. fructose receives a phosphate group to form fructose 6-phosphate which enters glycolysis at step 3)
74
what happens to carbons from glucose in glycolysis?
oxidized into pyruvate
75
what happened to electrons from glucose?
transferred into ATP and NADH
76
why does the inner membrane have so much folds?
to maximize surface area for more reactions to occur
77
what is pyruvate oxidation? what occurs during pyruvate oxidation?
pyruvate is transported into mitochondrial matrix and oxidizes into an acetyl group and CO₂,
acetyl group transferred to coenzyme A, forming into Acetyl-CoA
78
what is net energy yield in pyruvate oxidation?
2 CO₂, 2 NADH, 2 Acetyl-CoA
79
how much carbons does Acetyl-CoA have?
2 carbons, the other carbon from pyruvate is in CO₂
80
where does pyruvate oxidation occur?
mitochondrial matrix
81
what happens to carbons in pyruvate in pyruvate oxidation?
oxidized into Acetyl-CoA and CO₂
82
what is the net energy yield in pyruvate oxidation PER glucose molecule?
2 NADH molecules
83
What occurs during the citric acid cycle?
glucose is completely oxidized into 6CO₂
chemical energy in bonds of Acetyl-CoA are transferred to ATP via substrate level phosphorylation and to NADH and FADH₂
84
how is Acetyl-CoA completely oxidized in the citric acid cycle?
two carbons from Acetyl-CoA are added to oxaloacetate (4C), forming citrate (6C)
cycle continues, where citrate is converted back to oxaloacetate
85
where does the citric acid cycle occur?
mitochondrial matrix
86
what happened to carbons in acetyl-CoA in the citric acid cycle?
completely oxidized into CO₂
87
what happened to the electrons of acetyl-CoA in the citric acid cycle?
transferred into 3 NADH and 1 FADH₂ molecules
88
what is the NET energy yield from the citric acid cycle PER glucose molecule?
6 NADH, 2 FADH₂ and 2 ATP
89
where is most of the energy from one glucose molecule stored from glycolysis up to the citric acid cycle?
in the electron carriers NADH and FADH₂
90
what do the electron carriers do?
they donate electrons they carry to the electron transport chain (ETC), powering ATP synthesis via OXIDATIVE PHOSPHORYLATION
91
what is the electron transport chain?
allows energy from electron carriers generated during glycolysis to the citric acid cycle to drive ATP synthesis in the inner mitochondrial membrane
1. receives electrons from carriers
2. transports electrons to electron acceptors
3. generates proton gradient which drives ATP synthesis via oxidative phosphorylation
92
what processes are involved in the electron transport chain?
chemiosmosis (diffusion dealing with ions) and oxidative phosphorylation
93
what are mobile electron carriers? what is their purpose in the electron transport chain?
MECs are used to pass electrons between protein complexes called respiratory complexes in the ETC
94
what respiratory complex does NADH enter?
Complex I
95
what respiratory complexes does FADH₂ enter?
Complex II
96
what is the final electron acceptor in the electron transport chain?
oxygen
97
what happens to oxygen when it accepts electrons in the electron transport chain?
it is reduced into H₂O
98
what happens if no oxygen is available to accept electron in the electron transport chain?
ETC fails to continue, ATP is not produced, resulting in cells dying due to lack of energy
99
how does the electron transport chain create a proton gradient?
flow of electrons across ETC is coupled to pumping of H+ protons from mitochondrial matric across inner mitochondrial membrane into intermembrane space, creating conc. and electrical gradient
electrochemical gradient provides source of potential energy to synthesize ATP
100
what does the presence of an electrochemical gradient do?
electrochemical gradient provides source of potential energy to synthesize ATP
101
how do H+ in inner membrane space diffuse down their conc. gradient to mitochondrial matrix?
through protein channel called ATP synthase (complex 5)
102
how is the potential energy of the H+ gradient released?
H+ crosses the inner mitochondrial membrane from intermembrane space to the mitochondrial matrix through ATP synthase
103
Each pair of electrons released by NADH provides energy to produce how much ATP?
~ 2.5 ATP
104
Each pair of electrons released by FADH₂ provides energy to produce how much ATP?
~ 1.5 ATP
105
what is the max. # of ATP produced from one glucose molecule?
30-32
106
where is the electron transport chain located?
inner mitochondrial membrane
107
what is the net energy yield from oxidative phosphorylation?
about 26-28 ATP
108
what happened in the electron transport chain in terms of redox reactions?
electron donors (reducing agents) transfer electrons to electron acceptors (oxidizing agents)
NADH and FADH₂ are oxidized, while oxygen is reduced
109
how are cellular respiration reactions regulated?
level of energy/ATP in cell as well las level of NAD+/ NADH indicates how much energy a cell has available
110
what happens when ATP levels are low?
when ATP levels low / ADP levels high, cell activates or upregulates pathways leading to ATP synthesis
111
what happens when ATP levels are high?
when ATP levels high / ADP levels low, cell slows down or downregulates pathways leading to ATP synthesis
112
what happens if cell has high levels of NAD+?
cell activates or upregulates pathways leading to ATP synthesis to consume NAD+
113
what happens if cell has high levels of NADH?
cell slows down or downregulates pathways leading to ATP synthesis to prevent waste of NADH
114
How is step 3 of glycolysis important?
step 3 of glycolysis (converting fructose 6-phosphate to fructose 1,6-bisphosphate) is catalyzed by PFK-1
step 3 is considered a committed, important step and is under tight control
115
what is the role of phosphofructokinase-1 (PFK-1) in glycolysis regulation?
PFK-1 is an allosteric enzyme with many activators and inhibitors
when levels of ADP/AMP high(ATP low), molecules binds to PFK-1 and activates enzyme to continue glycolysis
when ADP/AMP low (ATP levels high), ATP binds to enzyme and inhibits its activity
116
what categories of cellular poisons obstruct oxidative phosphorylation?
1. blocks ETC (cyanide, CO)
2. blocks H+ flow through ATP synthase
3. make membrane leaky to H+
117
what is brown fat? how does it benefit organisms when it interrupts cellular respiration?
brown fat generates heat due to abundance of mitochondria
brown fat inner membrane has protein that allows H+ to flow back down electrochemical gradient without generating ATP whilst generating heat
useful for hibernation
118
what is anaerobic respiration?
cellular respiration with a molecule other than O₂ as its last electron acceptor
119
what is fermentation?
reactions that regenerates NAD+, absence of oxygen
120
what is lactic acid fermentation?
pyruvate is broken down via fermentation in absence of oxygen
electrons from NADH are transferred to pyruvate to produce lactic acid and NAD+
occurs in animals and bacteria
121
what is reaction formula for lactic acid fermentation?
Glucose + 2ADP + 1P = 2 lactic acid + 2ATP + 2H₂O
122
what is alcohol fermentation?
pyruvate releases CO₂ to form acetaldehyde, electrons from NADH are transferred to acetaldehyde to form ethanol and NAD+
123
what is function of coenzyme Q?
facilitate transport of electrons from complex I to III and complex II to III
124
what is function of cytochrome C?
facilitate electron transport from complex III to IV
125
why does NADH produce more ATP than FADH₂?
electrons from NADH are activating more proton pumps compared to electrons from FADH₂, which activate less proton pumps.
As electrons move through complex I in a series of redox reactions, energy is released, and the complex uses this energy to pump protons from the matrix into the intermembrane space
Complex II does not have the ability to pump protons against gradient
126
how does NADH have higher potential energy?
activates complex I, III, and IV while FADH₂ only activates complex III and IV
127
what is difference between substrate-level phosphorylation and oxidative phosphorylation?
