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Biology 2 > Lecture 10- Pathways that harvest chemical energy > Flashcards

Lecture 10- Pathways that harvest chemical energy Flashcards

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1
Q

What is the difference between slow twitch and fast twitch muscle fibers?

A

Slow twitch: lots of mitochondria to form ATP

Fast twitch: Fewer mitochondria, generate ATP in short bursts in absence of O2

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2
Q

What protein breaks down fat in fat tissues and leads to ‘marathon mouse’? (increase in slow twitch muscle fibers)

A

PPARδ

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3
Q

What are fuels?

A

Molecules whose stored energy can be released for use

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4
Q

How are molecules such as fats or proteins able to supply energy?

A

They are converted into glucose or intermediate compounds

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5
Q

Complex chemical transformations in the cell occur…

A

in a series of separate reactions that form metabolic pathways

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6
Q

Each reaction in a metabolic pathway is

A

catalyzed by a specific enzyme

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7
Q

Metabolic pathways are

A

similar in all organisms, from humans to bacteria

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8
Q

Metabolic pathways are comp_____

A

Compartmentalized in eukaryotes (certain reactions occur in specific organelles)

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9
Q

Each metabolic pathway is regulated by…

A

Key enzymes that can be inhibited or activated to determine how fast a reaction can go

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10
Q

C6H12O6 +6O2 —>

A

6CO2 + 6H20 + free energy

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11
Q

What is the function of the glucose metabolism pathway?

A

To trap stored energy of glucose into ATP molecules

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12
Q

What is the reaction that traps free energy into ATP molecules?

A

ADP + Pi + free energy –> ATP

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13
Q

What is the change in free energy from the complete conversion of glucose and oxygen into carbon dioxide and water?

A

-686 kcal/mol (exergonic)

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14
Q

What are the three metabolic processes that harvest energy from glucose?

A

Glycolysis
Cellular respiration
Fermentation

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15
Q

What is glycolysis?

A

The first step in glucose metabolism in all cells and produces two three carbon pyruvates

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16
Q

Does glycolysis use oxygen?

A

No

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17
Q

What is cellular respiration?

A

Aerobic
Converts each pyruvate molecule into three CO2 molecules
Energy stored in covalent bonds is transferred into ADP and Pi to form ATP

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18
Q

What is fermentation?

A

Anaerobic

Converts pyruvate into lactic acid or ethanol (energy rich molecules)

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19
Q

Why does fermentation not release as much energy as cellular respiration?

A

Lactic acid or ethanol is produced. Glucose break down is incomplete, less energy is released

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20
Q

What four pathways operate when oxygen is present as the final electron acceptor?

A

Glycolysis,
Pyruvate oxidation
Citric acid cycle
Electron transport chain

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21
Q

What 2 pathways operate in the absence of oxygen?

A

Glycolysis

Fermentation

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22
Q

What is a redox reaction?

A

A reaction in which one substance transfers one or more electrons to another substance

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23
Q

What type of reaction is the addition of phosphate to ADP to make ATP?

A

Endergonic

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24
Q

In redox reactions, what type of agent is glucose and what type of agent is oxygen?

A

Glucose is a reducing agent

Oxygen is a oxidizing agent

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25
What are co-enzymes?
Small molecules that assist in enzyme-catalyzed reactions
26
How is ADP a coenzyme?
It picks up energy released in exergonic reactions and uses it to form ATP
27
Other than ADP, what molecule acts as a coenzyme in redox reactions?
NAD acts as an electron carrier
28
What does NAD stand for?
Nicotinamide adenine dinucleotide
29
What is the oxidized and reduced form of NAD?
Oxidized: NAD+ Reduced: NADH + H+
30
What is the equation for the reduction of NAD+?
NAD+ + 2H --> NADH + H+
31
What is transferred to NAD+ to form NADH?
A hydride ion, H-
32
Why does oxygen readily accept electrons from NADH?
It is highly electronegative
33
What is the equation for the oxidation of NADH?
NADH +H+ +1/202 --> NAD+ +H20
34
What is the delta G value for oxidation of NADH?
-52.4 kcal/mol
35
What type of reaction is the oxidation of NADH?
Exergonic
36
Other than NAD, name another electron carrier in cells.
FAD
37
What does FAD stand for?
Flavin adenine dinucleotide
38
Where does glycolysis and fermentation occur in eukaryotes?
external to mitochondria
39
Where does glycolysis occur in prokaryotes?
In the cytoplasm
40
Where does fermentation occur in prokaryotes?
In the cytoplasm
41
Where does the citric acid cycle occur in prokaryotes?
In the cytoplasm
42
Where does the electron transport chain occur in eukaryotes?
The inner membrane of the mitochondria
43
Where does the electron transport chain occur in prokaryotes?
Plasma membrane
44
Where does the citric acid cycle and pyruvate oxidation occur in eukaryotes?
The matrix of the mitochondria
45
Where does pyruvate oxidation occur in prokaryotes?
On the plasma membrane
46
Does glycolysis generate CO2?
no
47
How many enzyme catalysed reactions are there in glycolysis?
10
48
What does glycolysis produce?
2 molecules of pyruvate 4 molecules of ATP 2 molecules of NADH
49
What are the two stages of glycolysis?
Energy investment reactions | Energy harvesting reactions
50
What are the first 5 energy investment reactions of glycolysis?
Endergonic
51
In what two reactions in glycolysis is ATP invested?
1 and 3
52
What happens during reaction 1 and 3 of glycolysis?
Two phosphate groups are attached to the glucose molecule using energy from ATP
53
What is the result of investing 2 ATP molecules during glycolysis?
Fructose 1,6-bisphosphate
54
What is the free energy of fructose 1,6 bisphosphate compared to that of glucose?
Higher
55
What enzyme catalyzes reaction 1 of glycolysis?
hexokinase
56
What is a kinase?
An enzyme that catalyzes the transfer of a phosphate group from ATP to another substrate
57
What enzyme catalyzes reaction 3 of glycolysis?
Phosphofructokinase
58
What does reaction 4 of glycolysis do?
Opens up the six-carbon ring structure and cleaves it into two different three carbon sugar phosphates
59
In summary, what is the end product of the energy investing reactions of glycolysis?
- Two molecules of ATP have been invested | - Two three carbon sugar phosphate molecules have been produced
60
What is the name of the 3 carbon sugar phosphate produced by the energy investing glycolysis reactions?
Glyceraldehyde 2-phosphate (G3P)
61
What is the drop in free energy for reaction 6 of glycolysis?
100kcal/mol
62
What type of reaction is reaction 6 of glycolysis?
Oxidation
63
How is the energy released in reaction 6 of glycolysis stored?
Reducing 2 molecules of NAD+ to NADH + H+
64
What happens if NAD is not recycled?
Glycolysis comes to a stop because its is present only in small amounts
65
What happens in reaction 7-10 of glycolysis?
2 phosphate groups are transferred to ADP
66
What is the name of the enzyme-catalyzed transfer of phosphate groups from donor molecules to ADP molecules to form ATP?
Substrate-level phosphorylation
67
What happens in reaction 7 of glycolysis?
Phosphoglycerate kinase catalyzes the transfer of a phosphate group from BPG to ADP
68
How many ATP molecules are produced per glucose molecule in the energy harvesting reactions?
4 (2 net)
69
At the end of glycolysis, each glucose molecule yields...
2 pyruvate 2 NADH +H+ 2 ATP
70
What does pyruvate oxidation link?
Glycolysis and the citric acid cycle
71
What is Coenzyme A?
A complex molecule responsible for binding two-carbon acetate molecule
72
Acetyl coenzyme A formation is a
multi step reaction
73
What is acetyl coenzyme A formation catalysed by?
Pyruvate dehydrogenase complex
74
What is pyruvate dehydrogenase complex?
A multi-enzyme complex attached to the inner mitochondrial membrane
75
What happens after pyruvate diffuses into the mitochondrion?
Pyruvate is oxidised to a two carbon actyl group (acetate) and CO2 is released
76
What happens after pyruvate is oxidised to become acetate?
Part of the energy from the oxidation is captured by reducing NAD+ to NADH + H+
77
How is the rest of the energy from oxidation of pyruvate into acetate stored?
Temporarily, by combining the acetyl group with CoA to form acetyl CoA
78
What is the overall reaction for the pyruvate oxidation reaction?
pyruvate + NAD+ CoA --> acetyl CoA + NADH +H+ +CO2
79
What does the citric acid cycle do?
Completes the oxidation of glucose to CO2
80
What is the starting molecule of the citric acid cycle?
Acetyl CoA
81
How many reactions are there in the citric acid cycle?
8
82
The citric acid cycle is maintained in a ________
steady state
83
What does it mean that the citric acid cycle is maintained in a steady state?
The concentration of the intermediates does not change
84
What is the first reaction of the citric acid cycle?
oxaloacetate and energy stored in Acetyl CoA forms citrate
85
What is removed during the first reaction of the citric acid cycle?
Coenzyme A
86
What is the second reaction of the citric acid cycle?
Citrate is rearranged to form isocitrate
87
What is the third reaction of the citric acid cycle?
Isocitrate is converted to alpha-ketoglutarate 2 hydrogen atoms and 1 CO2 is removed NADH + H+ forms
88
What is the 4th reaction in the citric acid cycle?
alpha-ketoglutarate is oxidised to succinyl CoA | Catalysed by a multi-enzyme complex
89
What is the 5th reaction in the citric acid cycle?
GDP +Pi-->GTP | Succinyl CoA releases CoA to become succinate
90
What does GTP stand for?
Guanosine triphosphate
91
What is the reaction of GDP +Pi --> GTP an example of?
Substrate level phosphorylation
92
What is GTP used for?
To make ATP from ADP
93
What is the 6th reaction of the citric acid cycle?
Succinate is oxidised to fumarate | FAD --> FADH2
94
What is the 7th reaction of the citric acid cycle?
Fumarate and water react, malate is formed
95
What is the final reaction of the citric acid cycle?
Malate is oxidised to oxaloacetate | NADH + H+
96
How many times does the citric acid cycle operate for each molecule of glucose?
Twice
97
What is the input for each citric acid cycle?
Acetate (actyl CoA) Water Oxidised electron carriers
98
What is the output for each citric acid cycle?
CO2 reduced electron carriers ATP
99
How is the citric acid cycle regulated?
Electron carriers that were reduced must be oxidized
100
What two chemical pathways oxidize electron carriers so that the citric acid cycle can proceed?
Fermentation | Oxidative phosphorylation
101
At the end of the citric acid cycle, each molecule of glucose yields from all three stages:
6 CO2 10 NADH + H+ 2 FADH2 4 ATP
102
What does fermentation use to reduce pyruvate?
NADH +H+
103
What are the two most understood fermentation pathways?
Lactic acid fermentation | Alcoholic fermentation
104
What serves as the electron acceptor in lactic acid fermentation?
Pyruvate
105
Why does lactic acid build up in muscles cause problems?
The acid ionizes pH of the cell is lowered Cellular activities reduce
106
Where does alcoholic fermentation take place?
Certain yeasts | Some plant cells
107
How does alcoholic fermentation metabolize pyruvate?
two enzymes
108
What is the first step in alcoholic fermentation?
carbon dioxide is removed from pyruvate to make acetaldehyde
109
What is the second step in alcoholic fermentation?
Acetaldehyde is reduced by NADH +H+ to produce ehtanol and NAD+
110
What is net yield of ATP from fermentation?
two ATP's

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