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BI110 > Chapter 5 - Cellular Respiration > Flashcards

Chapter 5 - Cellular Respiration Flashcards

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1
Q

what is cellular respiration?

A

a collection of metabolic reactions within cells that break down food molecules to produce ATP

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2
Q

what are the roles of cellular respiration?

A

1.) break down high energy molecules (carbs, lipids, proteins)

2.) convert chemical potential energy from bonds into ATP

3.) allow the cell to do work

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3
Q

Where does the energy on earth come from?

A

1.) the sun - ultimate source of energy

2.) photosynthesis - captures sunlight energy and converts to energy in the form of organic molecules (glucose)

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4
Q

what is electron sharing?

A

a chemical reaction where electrons are transferred from one atom/molecule to another

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5
Q

loss of electrons

A

oxidation

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6
Q

gain of electrons

A

reduction

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7
Q

what is oxidation?

A

the partial or full loss of electrons from a substance (substance losing = oxidized)
lose H or gain O

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8
Q

what is reduction?

A

the partial or full gain of electrons to a substance (substance gaining = reduced)
gain H or lose O

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9
Q

what is a redox reaction?

A

are coupled reactions where a oxidation and reduction reaction occur simultaneously

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10
Q

what are the 2 types of combustion in cellular respiration?

A

1.) direct (rapid) oxidation
2.) stepwise (controlled) oxidation

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11
Q

what occurs in direct (rapid) combustion?

A
  • one big reaction
  • large activation energy
  • no energy is stored
  • all heat is released at once = would incinerate the cell
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12
Q

what occurs in stepwise (controlled) combustion?

A
  • there are many small enzyme catalyzed intermediate reactions
  • small activation energy
  • energy is stored to be transformed into ATP
  • small amount of energy is released
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13
Q

what is the most common energy carrier molecules in cells?

A

NAD+

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14
Q

what are the oxidized and reduced form of NAD+?

A
  • NAD+ is the oxidized form and can pick up electrons
  • NADH is the reduced form, and can lose electrons
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15
Q

what are the oxidized and reduced form of FAD+?

A
  • FAD is the oxidized form, and can pick up electrons
  • FADH2 is the reduced form, and can lose electrons
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16
Q

oxidation and reduction reactions of NAD+ and FAD?

A

reduction:
1.) NAD+ + 2e + 2H+ –> NADH (reduced form)
2.) FAD + 2e + 2H –> FADH2 (reduced form)

oxidation:
1.) NADH –> NAD+ + 2e + 2H+ (oxidized form)
2.) FADH2 –> FAD + 2e + 2H+ (oxidized form)

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17
Q

what is the equation for cellular respiration?

A

glucose + oxygen –> carbon dioxide + water + energy (ATP)

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18
Q

what are the 3 stages of cellular respiration?

A

1.) glycolysis
2.) pyruvate oxidation and citric acid cycle
3.) oxidative phosphorylation and ETC

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19
Q

where does glycolysis occur?

A

in the cytosol

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20
Q

where does pyruvate oxidation and CAC occur?

A

in the mitochondrial matrix

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21
Q

where does oxidative phosphorylation and ETC occur?

A

inner membrane of the mitochondria

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22
Q

where is glycolysis considered an ancient metabolic process?

A

it is a universal process that all organisms on earth (prokaryotes and eukaryotes) because it doesn’t require O2 as it developed when primitive earth was an oxygen-free environment

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23
Q

what happens in stage 1: glycolysis?

A
  • converts glucose (6 carbons) into 2 molecules of pyruvate (3C)
  • a series of 10 chemical reactions catalyzed by enzymes which involves an “energy investment” and “energy payoff” phase
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24
Q

what reactions occur in glycolysis?

Study These Flashcards
A

1 glucose molecule is converted to 2 pyruvate molecules:
2 ATP –> 2 ADP + Pi
4ADP + Pi –> 4 ATP
2 NAD+ –> 2 NADH

Net ATP = 2

25
what is phosphofrutokinase?
- an enzyme which catalyzes the second ATP consuming step (ATP --> ADP + Pi) of the glycolysis pathway (step 3) - it regulates glycolysis through allosteric inhibition and can increase/decrease the rate of glycolysis in response to the cell's energy requirements
26
what is substrate level phosphorylation?
- ATP production by removing a phosphate from a high energy donor and adding it to ADP (ADP + Pi --> ATP) - produced a small amount of ATP
27
what is oxidative phosphorylation?
- ATP production by a series of redox reactions when electrons from NADH and FADH2 pass through the ETC, creating a electrochemical gradient and energy to drive synthesis of ATP from ADP - most ATP is produced through this process
28
what happens in stage 2.1: pyruvate oxidation?
- an aerobic process linking glycolysis and the citric acid cycle - pyruvate (3C) is oxidized to become an Acetyl group (2C) then added to Co-enzyme A to form Acetyl CoA - CO2 is a product when a carboxyl group is removed from pyruvate
29
what reactions occur in pyruvate oxidation?
2 Pyruvate molecules are converted into 2 Acetyl CoA and 2 CO2 molecules: 2NAD+ --> 2NADH 2 CoA --> added to acetyl
30
what happens in stage 2.2: citric acid cycle?
- 8 enzyme catalyzed reactions where high energy electron carrier molecules are produced (NADH and FADH2) for stage 3 - some ATP is produced by substrate-level phosphorylation
31
what is chemiosmosis?
the process of pumping protons across the membrane to generate the proton gradient driven by the flow of electrons through the ETC
32
what occurs in stage 3: oxidative phosphorylation?
- involves the electron transport chain (ETC) and chemiosmosis - energy is harnessed from the flow of electrons through the ETC to power ATP synthase and the production of ATP
33
where do the electron carriers from stage 1 and 2 go?
They go to the ETC to "drop off" electrons and protons for oxidative phosphorylation: - NADH gives e- to complex 1 - FADH2 gives e- to complex 2
34
what is the role of high energy electrons in the ETC?
the ETC chain converts the chemical potential energy found in NADH and FADH2 into a proton force (an electrochemical gradient) to drive ATP synthesis
35
what are the different parts of the ETC?
- 4 protein complexes (1, 2,3 and 4) in the inner mitochondrial membrane - 2 small shuttle carriers: ubiquinone (UQ) from complex 1 and 2 to 3 and cytochrome c (cytc) shuttles from 3 to 4
36
how does the electron transport chain work?
37
what is the role of the protein complexes in the ETC?
- the 3 major complexes (1,3 and 4) pump H+ protons from the mitochondrial matrix to the inter-membrane space by the release of energy from electrons moving down the chain - they contain prosthetic groups which cycle between reduced and oxidized state as they accept upstream electrons and donate electrons downstream
38
what is the electronegativity of the ETC?
- electronegativity of each complex increases as you move downstream (right) to keep electrons moving in one direction - allows for free energy to be released and used for active transport of H+ from low to high concentration to inter-membrane space
39
what is the final electron acceptor?
oxygen because it is very electronegative
40
what happens to the electrons that pass through the ETC?
they become depleted of energy (b/c they release it) and delivered to the oxygen
41
what does the ETC do?
the reduced, high energy electron carriers (NADH and FADH2) produced in stage 1 and 2 by the complete oxidation of glucose drop their electrons off and transported through the complexes to power the synthesis of ATP
42
what are the steps of electron transport?
1.) complex 1 and 2 receive their respective electrons from NADH and FADH2 2.) Ubiquinone is reduced to CoQH2 and transfers electrons from complex 1 and 2 to 3 3.) cytochrome c moves electrons from complex 3 to 4 where oxygen is reduced to form water at the end of the ETC
43
how does proton transport and ATP synthesis work?
- the transport of electrons is coupled with the transport of protons from [low] to [high] across the inner membrane from mitochondrial matrix to the inter-membrane space - a electrochemical proton gradient is formed, and the potential energy is used to drive ATP synthase
44
what is ATP synthase?
a molecular motor embedded in the inner mitochondrial membrane, which uses the free energy of the proton gradient to generate ATP from ADP + Pi via oxidative phosphorylation
45
what is the ATP yield from the oxidation of glucose?
1.) glycolysis = 2 ATP 2.) citric acid cycle = 2 ATP 3.) oxidative phosphorylation = 28 ATP total = 32 ATP
46
what happens to the intermediates of glycolysis and the citric acid cycle?
they can be used elsewhere and used as starting substrates for the production of amino acids, fats, and the pyrimidine and purine bases for nucleic acid
47
can energy only be extracted from simple sugars?
NO, it can extracted from carbs, fats and proteins too by entering at different points of the chain
48
how is cellular respiration controlled?
phosphofructokinase acts as an allosteric enzyme that can regulate the pathway so no resources are wasted - ATP, citrate are inactivators - ADP are activators
49
what happens to cellular respiration in the absence of oxygen?
- in anaerobic respiration, the terminal electron acceptor isn't oxygen (sulfate, nitrate or ferric ion) - lactate or ethanol fermentation occurs instead of CAC and oxidative phosphorylation
50
what is fermentation?
the pathway of respiration that oxidizes fuel molecules in the absence of oxygen
51
2 types of fermentation
alcohol and lactate
52
how does fermentation work?
NAD+ produced as a product in fermentation is recycled and used again and again in glycolysis to keep producing 2 ATP
53
why does fermentation only yield 2 ATP?
lactic acid and ethanol are not fully oxidized and still contain a large amount of chemical energy in their bonds
54
lactate fermentation
- occurs in animal and bacteria - NAD+ and lactic acid are produced
55
alcohol fermentation
- occurs in plants and fungi - NAD+, ethanol and CO2 are produced
56
strict anaerobes
cannot grow in the presence of oxygen
57
strict aerobes
require oxygen
58
facultative aerobes
can grow in the presence of oxygen or grow using fermentative pathways
59
what is the paradox of aerobic life?
- oxygen can be dangerous to all forms of life because the conversion from O2 to H2O is stepwise, resulting in the intermediate of ROS (hydrogen peroxide, superoxide) - defence = antioxidants (enzymes and non enzymes)

BI110 (3 decks)

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