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QUIZZ 3 Flashcards

1
Q

Do exergonic processes reach equilibrium or go to completion?

A

They reach equilibrium

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2
Q

What is glycogendysis?

A

The breakdown of glycogen (a stored form of glucose) into glucose 1-phosphate and glucose 6-phosphate.

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3
Q

What can glucose 1-phosphate and glucose 6-phosphate be used for?

A

They can be used as a source of energy

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4
Q

If glucose 1-phosphate and glucose 6-phosphate are dissolved in water, what is their respective concentration (percentage) at equilibrium.

A

No matter what the initial quantities were, there will always be 95% of glucose 6-phosphate and 5% of glucose 1-phosphate.

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5
Q

If the concentration of G1P is higher than the concentration of G6P, what happens?

A

A concentration gradient will be created so that G6P is kept in the cell and so that more glucose is allowed to enter the cell.

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6
Q

If the concentration of G6P is higher than the concentration of G1P, what happens?

A

Because there is no concentration gradient, no energy is used and the tendency to be spontaneous steps in (although it will stop being spontaneous at some point).

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7
Q

What does ATP hydrolysis release?

A

Free energy

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8
Q

What does ATP contain?

A

A high amount of potential energy

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9
Q

What is it about the chemistry of ATP that explains the -deltaG when it is hydrolyzed?

A

The exergonic nature of ATP hydrolysis is because of both a decrease in potential energy and an increase in entropy.

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10
Q

ATP + H2O –> ?

A

ADP + phosphate

-deltaG, so the reaction is spontaneous

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11
Q

In which is there more potential energy, ATP or ADP? Why is that so?

A

ATP because the loss of the terminal phosphate in ADP has decreased the electrical repulsion among the negatively charged oxygen atoms of the phosphate groups.

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12
Q

What is the fact that all forms of life use ATP as their dominant energy currency is a piece of evidence for?

A

It points to all forms of life sharing a common ancestor

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13
Q

What is the molecule that often links the two types of pathways (catabolic and anabolic)?

A

ATP

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14
Q

What is the chemical structure of ATP

A

It consists of a five-carbon sugar (ribose), linked to the nitrogenous base adenine joined to a chain of three phosphate groups.

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15
Q

What does the enzyme kinase do in glycolysis?

A

It transfers a phosphate between ATP and another molecule.

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16
Q

What does hexokinase do to ATP?

A

It transfers an inorganic phosphate group from ATP to a substrate.

This step requires some energy.

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17
Q

What happens when hexokinase binds to glucose?

A

It undergoes a conformational change which prevents ATP hydrolysis.

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18
Q

Glutamic acid + NH3 –> ?

A

Glutamine + H2O

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19
Q

amino acid (A.A) + a nitrogenous group –> amino acid (A.A) + H20
Is this reaction exergonic or endergonic? Is it spontaneous or non-spontaneous?

A

Because the products have more free energy than the reactants, the reaction is endergonic. The positive deltaGj shows that the reaction will not occur spontaneously.

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20
Q

For a reaction that happens within your cells all the time and gives raise to syntesized molecules of glutamine, yet does not have a negative deltaG, how is it possible?

A

Because during metabolism, glutamine is synthesized through a process called energy coupling.

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21
Q

What is energy coupling?

A

An endergonic reaction that occurs by being coupled to an exergonic reaction.

For most reactions, the energy is provided by exergonic breakdown of ATP

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22
Q

What is the mechanism for the exergonic breakdown of ATP and the endergonic biosynthesis of glutamine?

A

Glutamic acid is cleaved by ATP to form ADP, the phosphate attached to glutamyl phosphate is cleaved by ammonia to form glutamine

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23
Q

What does metabolism consists of?

A

Catabolic and anabolic pathways

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24
Q

What is a catabolic pathway?

A

A series of chemical reactions that results in the breakdown of larger, more-complex molecules into smaller, less-complex molecules. Those pathways release the free energy of ATP to fuel the anabolic reactions.

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25
What is an anabolic pathway?
A series of reactions that results in the synthesiss of larger, more-complex molecules from simpler starting molecules. The require energy because the overall free energy of the products is greater than the free energy of the starting molecules.
26
In metabolism, how are catabolic and anabolic pathways linked together and why is that so?
They are linked through chemical energy, because anabolic reactions require this chemical energy for the formation of new covalent bonds.
27
What are the role of catalysts in relation to the activation energy of reactions?
They catalize the reaction so the that the reaction is sped up.
28
What is required for chemical reactions to occur (conditions)?
So that those reactions occur, established bonds need to be broken and new bonds need to be formed. The bonds first need to be strained or otherwise made less stable with requires a small input of energy: the activation energy.
29
What is a catalyst?
It is a chemical agent, that speeds up the rate of a reaction without itself taking part in the reaction.
30
True or False: All catalysts are enzymes.
False | The most common biological catalysts are a group of proteins called enzy
31
What is the role of enzymes in chemical reactions?
They lower the activation energy of a reaction by inducing the transition state.
32
What does the binding of substrate(s) to an active site of an enzyme results in?
It results in the substrate acquiring the transition state conformation. The reactants are thus put togheter in the right orientation for catalysis to occur.
33
What happens if the reactant molecule is exposed to alterred charge environments that promote catalysis.
Those alterations come from some of the enzyme's active sites that might contain ionic groups whose charges alter the substrates in a way to favor catalysis.
34
In summary, what are the three ways for enzymes to affect chemical reactions?
1. Enzymes accelerate reactions by reducing the activation energy 2. Enzymes reduce the activation energy by inducing the transition state 3. Enzymes aquire the transition state conformation by the substrate(s) binding to their active site
35
What is a cofactor?
A nonprotein group that binds very precisely to the enzyme. Many enzymes require one. They are often vitamins/minerals (inorganic molecules).
36
Give an exemple of collaboration between an enzyme and a cofactor that is a metal.
DNA polymerase (enzyme) needs Magnesium (cofactor) to be activated.
37
True or False: Cofactors are often metals. Develop
True. They are mostly metals such as iron, copper, zinc, or manganese. Although most cells need very small amounts of these metals, they are absolutely essential for the catalytic activity of the enzyme to which they bind.
38
Give an exemple of collaboration between an enzyme and a cofactor.
Hemoglobin (enzyme) requires an hemegroup ion (cofactor) to bind with oxygen.
39
Are all cofactors coenzymes?
No
40
What are coenzymes?
They are organic molecules that are often derived from vitamins.
41
Give 2 examples for coenzymes.
1. Vitamin C (coenzyme) is involved in the building of collagen 2. Niacin/Vitamin B3 (coenzyme) is the precursor to the coenzymes NAD and NADP
42
What five factors affect enzyme activity?
1. Enzyme and substate concentrations can change the rate of catalysis 2. It can be altered by competitive regulation (inhibition) 3. It can be altered by noncompetitive (allosteric) regulation (shape change) 4. It can be altered by pH 5. It can be altered by temperature
43
In a case where substrate is present in excess, what is the rate of catalysis proportional to?
It is proportional to the amount of enzyme as the higher enzyme concentration means the higher rate of product formation. | The enxyme concentration is the only limitting factor.
44
In a case where the enzyme concentration is constant, what is the rate of reaction's relation to the substrate concentration?
The rate of reaction increases with the substrate concentration until the saturation level is atteined.
45
What is the competitive inhibitor molecule?
It ressemble the substrate and competes for the active site of the enzyme. The substrate is thus unable to bind when the inhibitor is bound to the active site.
46
In what consists noncompetitive (allosteric) regulation in the case of a noncompetitive activator?
The enzyme (in a low activity state (weak bond)) binds the allosteric activator to its allosteric active site and thus converts the enzyme to a high-affinity state (strong bond). In the high-affinity state, the enzyme binds the substrate to its active site.
47
In what consists noncompetitive (allosteric) regulation in the case of a noncompetitive inhibitor?
The enzyme (in a high-affinity state (strong bond)) binds an allosteric inhibitor (the substrate is already binded to the enzyme) which converts it to a low-affinity state. Then the substrate is released.
48
Complete the example of cellular respiration for the enzyme phosphofructokinase (PFK) by explaining what the noncompetitive activator and the noncompetitive inhibiter's roles are?
The activator is ADP, it allows for PFK to be active (high-affinity) The inhibitor is ATP, il prevents PFK activation (low-affinity). In this case, if ATP increases, we don't need to break down glucose while if ADP increases, we need to break down glucose.
49
True or False: An enzyme typically has an optimal pH at which it is most active. What is this called?
True. The optimum.
50
What happens when the pH drops below or above the optimum? What happens if the pH is at extreme pH values?
Below or above: the rate of enzyme activity drops off. Extremes: the rate of enzyme activity drops to zero.
51
What two characteristics of temperature change its effect on chemical reactions?
1. Temperature has a general effect on chemical reactions of all kinds 2. Temperature has a more specific effect on all proteins including enzymes.
52
Example of visible effects of environmental temperature on enzyme activity in Siamese cats.
Heat-sensitive enzyme cotrolling melanin production is denatured in warmer body regions so dark pigment is not produced there. | denatured: the protein is unfolded and loses its shape and function.
53
54
55
What are the 3 catabolisme pathways of cellular respiration?
Aerobic respiration, anaerobic respiration and fermentation
56
In aerobic respiration, what does 1 molecule of glucose yields theoretically?
Between 36 and 38 ATPs . Aerobic respiration uses O2.
57
In anaerobic respiration, what does 1 molecule of glucose yield theoretically?
Between 2 and 36 ATPs . Anaerobic respiration is done without O2.
58
In fermentation, what does 1 molecule of glucose yield theoretically?
2 ATPs. It is the backup option if either aerobic or anaerobic respiration do not happen.
59
Describe the aerobic respiration pathway briefly.
Step 1: Glycolysis (Cytoplasm) Step 2: Krebs cycle (Mitochondria) Step 3: ETC using O2 as electron acceptor (Mitochondria) | Because O2 has high electronegativity.
60
Describe the anaerobic respiration pathway briefly.
Step 1: Glycolysis (Cytoplasm) Step 2: Krebs cycle (Mitochondria) Step 3: ETC using non-O2 compounds as electron acceptor (So42-, NO2-, CO22-) (Mitochondria) | Those compounds are not in the body (external environment).
61
Describe the fermentation pathway briefly.
Step 1: Glycolysis (Cytoplasm) Step 2: Using organic compounds like alcohols and acids as electron acceptor (Mitochondria) | No Krebs cycle nor ETC
62
What are redox reactions?
Reactions in which atoms have their oxidation state changed. They involve the transfer of electrons between chemical species.
63
What is an oxidation?
The loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
64
What is a reduction?
The gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.
65
What is the ultimate source of the energy-rich carbon compound found in carbohydrates, fats, and proteins?
Photosynthesis
66
In photosynthesis, what is light energy used for?
It is used to extract electrons from water. Those electrons then combine with H to reduce CO2 into glucose, a carbohydrate.
67
What is the major by-product of photosynthesis?
Oxygen, a molecule needed for the most common type of cellular respiration.
68
In cellular respiration, what is glucose oxidized into?
CO2
69
In cellular respiration, what is O2 reduced into?
H2O
70
How can we define cellular respiration?
As the collection of metabolic reactions within cells that breaks down food molecules.
71
Life and its systems are driven by a cycle of electron flow that is powered by what?
Light in photosynthesis and oxidation in cellular respiration.
72
What three phases can cellular repiration be divided into?
- Glycolysis - Pyruvate oxidation and the citric acid cycle - Oxidative phosphorylation
73
What happens during glycolysis?
Enzymes break down a molecule of glucose into 2 molecules of pyruvate, ATP and NADH are synthesized.
74
What happens during pyruvate oxidation and citric acid cycle?
Acetyl coenzyme A, formed from the oxidation of pyruvate, enters a metabolic cycle where it is completely oxidized to CO2. ATP and NADH are synthesized.
75
What happens during oxidative phosphorylation?
With the NADH synthesized in the two last steps and the liberated electrons being passed along an ETC are oxidized, until they are transferred to oxygen, producing water. The free energy released during electron transport is used to generate a proton gradient across a membrane (in turn this will be used to synthesize ATP).
76
What are all stages of cellular respiration required to extract?
The maximum amount of energy that is biologically possible from a molecule of glucose. | Not all organisms undergo all three stages.
77
True or False: Glycolysis is universal, being found in all three domains of life.
True. Itis found in Archaea, Bacteria, and Eukaria.
78
True or False: Glycosis depends upon the presence of O2
False
79
True or False: glycosis depends upon the presence of sophisticated ETCs and internal membrane systems to function.
False
80
Where does glycolysis occur in a cell?
Inside the cytosol of all cells, using soluble enzymes.
81
What does glycolysis consists of?
10 sequential enzyme-catalyzed reactions that lead to the oxidation of the six-carbon sugar glucose.
82
What does the splitting of glucose by glycolysis produce?
2 molecules of the three-carbon compound pyruvate. | No carbons are lost during the reaction.
83
What does the potential energy released in the oxidation lead to (for glycolysis)?
To the synthesis of both NADH and ATP. | Eventually yields 3 ATP/NADH (ETC)
84
In glycolysis, what is the energy investement followed by payoff?
An initial five-step energy-requiring phase followed by a five-step energy-releasing phase.
85
In glycolysis, why is it that no carbon is lost?
Because the reactions of glycolysis convert glucose (a six-carbon molecule) into two molecules of the three-carbon compound pyruvate.
86
What is NADH?
Nicotinamide adenine dinucleotide is a coenzyme found in all living cells. The compound is a dinucleotide, because it consists of 2 nucleotides (one with an adenine base and one with nicotinamide) joined through their phosphate groups
87
NADH exists in what two forms?
AN oxidized and reduced form abbreviated as NAD+ and NADH respectively.
88
NADH -->
NAD+ + H+ + 2e-
89
By what is ATP generated?
By substrate level phosphorylation.
90
What is substrate-level phosphorylation in the case of ATP?
A phosphate group is transfered from a high-energy donor directly to ADP, forming ATP. It is mediated by a specific enzyme and is also the mode of ATP synthesis used in the citric acid cycle.
91
What does the enzyme mutase do in glycolysis?
It transfers functional groups from one position to another within the same molecule.
92
What does the enzyme isomerase do in glycolysis?
It changes a molecules' conformation.
93
What does the enzyme dehydrogenase do in glycolysis?
It removes an hydrogen from the substrate.
94
What does the enzyme enolase do in glycolysis?
It removes water from the substrate.
95
Although they lack mitochondria, what do many archaea and bacteria have?
Respiratory ETCs that are located on internal membrane systems derived from the plasma membrane.
96
What do bacteria and archaea have when they are said to possess anaerobic respiration?
They have respiratory chains that use a molecule other than O2 as the electron acceptor. They use sulfate, nitrate and the ferric ion Fe3+ as teminal electron acceptors.
97
If oxidative phosphorylation can proceed in anaerobic organisms, what explains why aerobic respiration evolved to be the dominant form of respiratory metabolism?
Simply by being electronegative, O2 has greater affinity for electrons than any other electron acceptor.
98
In eukaryotic cells, what does low oxygen levels result in?
Fermentation
99
In eukaryotic cells, what is the pathway followed by glycolysis when oxygen is plentiful?
The pyruvate and NADH produced by glycolysis are transported into mitochondria, where they are oxidized using the citric acid cycle and ETC.
100
In eukaryotic cells, what is the pathway followed by glycolysis when oxygen is absent or in short supply?
The pyruvate remains in the cytosol, where it is reduced, consuming the NADH generated by glycolysis in a metabolic process called fermentation.
101
In what organisms does alcohol fermentation occur?
It occurs in microorganisms such as yeasts, which are single-celled fungi.
102
What happens during alcohol fermentation?
Pyruvate is reduced to ethyl alcohol as CO2 is released and NADH is oxidized to NAD+
103
What does not happen in alcohol fermentation because there is no oxygen?
The ETC is blocked which means that NADH cannot give e- , thus there is no NAD+ = no glycolysis, fermentation keeps glycolysis going.
104
In what organisms is lactate fermentation found?
Many bacteria, some plant and animal tissues.
105
What happens during lactate fermentation?
Pyruvate is converted into the three-carbon molecule lactate.
106
When does lactate fermentation occur for exemple?
When vigorous contraction of mucle cells calls for more oxygen than the circulating blood can supply.
107
In lactate fermentation, what happens when the oxygen content of the muscle cells returns to normal levels?
The reverse of the reaction regenerates pyruvate an NADH.
108

Bio II (13 decks)

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