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Biol 130 > Module 7: Cellular Respiration > Flashcards

Module 7: Cellular Respiration Flashcards

1
Q

What can cellular respiration do?

A
  1. Can utilize carbs, lipids and proteins
  2. converts energy in fuel molecules into ATP
  3. Allows the cell to do work
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2
Q

What are the two types of phosphorylation?

A
  1. substrate level
  2. oxidative
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3
Q

What is Stage 1 of Cellular Respiration?

A

Glycolysis
- occurs in the cytoplasm
- glucose is partially broken down and small amount of energy is released
- forms pyruvate

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4
Q

What is Stage 2 of Cellular Respiration?

A

Pyruvate Oxidation
- occurs in the mitochondria
- pyruvate is produced from the breakdown of glucose in glycolysis and converted to acetyl-CoA and CO2

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5
Q

What is Stage 3 of Cellular Respiration?

A

Citric Acid Cycle
- occurs in the mitochondria
- Acetyl-CoA from the end of stage 2 is broken down
- this releases CO2, small amount of energy and electron carriers

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6
Q

What is Stage 4 of Cellular Respiration?

A

Oxidative Phosphorylation
- occurs in the mitochondria
- all the electron carriers from stages 1-3 release their high energy electrons to the electron transport chain
- this produces ATP

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7
Q

What mechanisms generate ATP?

A

Substrate level phosphorylation is the process by which ATP is synthesized by a hydrolysis reaction involving enzyme/substrate complex
- a small amount of ATP is generated
- the energy is transferred to electron carriers which carry energy from one reaction to another
- the electron carriers transport electrons to the respiratory ETC, which transfers electrons acoross membrane associated proteins to a final acceptor
- Oxidative Phosphorylation is the process where the proteins harness the energy released to produce ATP

The majority of ATP is produced using OP

substrate level phosphorylation is a direct phosphorylation of ADP with a phosphate group by using the energy obtained from a coupled reaction whereas oxidative phosphorylation is the production of ATP from the oxidized NADH and FADH2.

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8
Q

Oxidation Reactions in Cellular Respiration

A
  • NAD+ and FADH are important electron carriers in cellular respiration
  • in CR the energy stored in glucose is harnessed in electron carriers as glucose is oxidized into CO2
  • In the breakdown of glucose, glucose is oxidized to CO2 and O2 is reduced to H2O
  • oxidation = Loss of e-
  • reduction = gain e-
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9
Q

What is the final electron acceptor in cellular respiration?

A

Oxygen

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10
Q

When O2 is reduced it turns into what?

A

forms H2O

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11
Q

What is the original electron donor in cellular respiration?

A

glucose

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12
Q

How do electrons move from one molecule to the next during cellular respiration?

A

reduction reactions

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13
Q

What are the two important electron carriers?

A

NAD+/NADH & FADH/FADH2
- the oxidized forms of these carriers are NAD+ and FADH
- the reduced forms are NADH and FADH2
- through glycolysis, pyruvate oxidation, and the citric acid cycle, the form of the electron carrier accepts electrons and becomes reduced
- the reduced form of the electron carriers has high potential energy
- this is used to synthesize ATP in the final stage of cellular respiration

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14
Q

What type of pathway is glycolysis?

A

Catabolic

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15
Q

How many chemical reactions does it take to break down glucose?

A

10
- goes from six carbon glucose to 2 three carbon pyruvates

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16
Q

Where does glycolysis occur?

A

cytosol

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17
Q

What is glycolysis relationship with O2?

A

occurs in the presence or absence of O2

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18
Q

What are the three phases of glycolysis?

A
  1. Preparatory Phase
    - where energy is consumed
  2. Cleavage Phase
    - where glucose is split into two
  3. Payoff Phase
    - where ATP is one of the products
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19
Q

Glycolysis Phase 1

A

Preparatory Phase
- the preparation of glucose for the next two phase’s happens here
- add two phosphate groups to glucose, producing fructose 1,6-biphosphate
- this process requires an input of energy in the form of two molecules of ATP
- the phosphorylation of glucose traps the molecule inside the cell and destabilizes it so that i is ready for phase 2

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20
Q

Glycolysis Phase 2

A

Cleavage Phase
- cleavage of fructose 1,6 biphosphate into two molecules
– glyceraldehyde 3-phosphate
– dihydroxyacetone phosphate (which is quickly converted into another molecule of glyceraldehyde 3-phosphate)

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21
Q

Glycolysis Phase 3

A

Payoff Phase
- two molecules of pyruvate are formed
- two molecules of the electron carrier NADH are produced
four molecules of ATP are produced

22
Q

What is the net gain of ATP in glycolysis?

A

2
- produces 4 ATP, but uses 2

23
Q

What is the makeup of the mitochondria?

A
  1. the inner membrane
  2. the outer membrane
    - these define the two spaces
  3. inter membrane
    - space between the two membranes
  4. mitochondrial matrix
    - space inside inner membrane
24
Q

Pyruvate Oxidation

A
  • when oxygen is present, pyruvate can be oxidized to produce carbon dioxide and NADH
  • Ultimately to Acetyl-CoA
  • these reactions occur in the mitochondrial matrix
  • pyruvate is converted to Acetyl CoA and then further broken down in the citric acid cycle
  • the pyruvate is initially oxidized to form CO2 and an acetyl group
25
Q

Where is the acetyl group in pyruvate oxidation transferred to?

A
  • the acetyl group is transferred to coenzyme A, which carries the acetyl group to the citric acid cycle
26
Q

What enzymes catalyze the reactions in pyruvate oxidation?

A

pyruvate dehydrogenase complex

27
Q

Overall what does one molecule of pyruvate produce?

A

1 CO2
1 molecule of NADH
1 molecule of acetyl-CoA

but remember glycolysis produces 2 molecules of pyruvate, thus, at the end of this process for each GLUCOSE molecule there are
2 CO2
2 molecules of NADH
2 molecules of acetyl-CoA

28
Q

Why is the Citric Acid cycle called a cycle?

A
  • because the first reactant (oxaloacetate) in the process is also regenerated at the end
29
Q

During the citric acid cycle what happens to the fuel molecules?

A

they are completely oxidized

30
Q

Where does the citric acid cycle happen?

A

In the mitochondrial matrix

31
Q

What happens during the citric acid cycle?

A

the citric acid cycle completes the oxidation of glucose and turns it into CO2 (produces 2)

32
Q

What does the citric cycle produce?

A
  • undergoes substrate level phosphorylation to produce ATP
  • 3 NADH
  • 1 FADH
33
Q

How are intermediates used in reference to the citric acid cycle?

A

some organisms can use products from different steps in the citric acid cycle as intermediates in other metabolic pathways

34
Q

Why do we exhale CO2?

A

the oxidation of acetyl-CoA produces the carbon dioxide we exhale

35
Q

What do NADH and FADH2 produce?

A

they produce transfer electrons to other carriers in the electron transport chain (ETC)
- produced though redox reactions in the first 3 stages of cellular respiration

36
Q

CO2 produced from citric acid

A
  • there is a transfer of the potential energy stored in acetyl-CoA to be stored in NADH and FADH2
  • also the production of GTP is catalyzed by substrate level phosphorylation
37
Q

Where is the ETC?

A

in the mitochondrial inner membrane

38
Q

Overview of ETC

A
  • electrons enter and move from donors to acceptor until they reach the final electron acceptor, oxygen
  • when oxygen accepts the electron it is reduced to H2O
39
Q

Where are electrons moved?

A
  • electrons are moved from energy storage molecules to proteins in the ETC
40
Q

How do electrons move?

A

they move through a sequence of redox processes which contributes to the formation of the proton gradient
- this stores potential energy for ATP synthesis

41
Q

What happens with protons near the membrane and what is their distribution?

A
  • protons are pumped across the membrane and a gradient is formed across the membrane
  • the distribution is as follows:
    1. in the intermembrane space there is HIGH [protons]
    2. in the mitochondrial matric there is LOW [protons]
  • the protons cannot diffuse across the membrane (can’t go on own), the proton concentration gradients contains high potential energy
42
Q

What does the proton gradient power?

A

the proton gradient powers ATP synthase, a molecular machine

43
Q

How does ATP synthase work?

A

-protons flow down their concentration gradient
- as protons pass through a channel it rotates a protein subunit
- this converts one form of energy into energy in bonds of ATP

44
Q

Summary of CR

A
  • Overall the energy of glucose is released slowly in a series of reactions
  • some of the energy is released by substrate-level phosphorylation
  • some is generated through redox reactions that transfer energy to the electron carriers NADH and FADH2
  • these carriers donate electrons to the ETC, forms the proton gradient to drive ATP synthase
    – this is oxidative phosphorylation
  • thus the complete oxidation of GLUCOSE forms 32 molecules of ATP
45
Q

What happens if oxygen is not available?

A

If O2 is not available, the cell is under anaerobic conditions
- the pyruvate produced from glycolysis can be reduced by a fermentation process

46
Q

In animal and bacteria cells what happens if there is no Oxygen?

A

the pyruvate is reduced to lactic acid
- this regenerates NAD+ which can then be reduced in glycolysis
- ATP is still synthesized in small amounts for use by the cell

Glucose + 2 ADP + 2 Pi -> 2 lactic acid + 2 ATP + 2 H2O

47
Q

What happens in plants and fungus if there is no oxygen?

A

they undergo ethanol fermentation
- the pyruvate releases CO2 to form acetaldehyde, the electrons from NADH are transferred to acetaldehyde to produce ethanol and NAD+
- regeneration of NAD+ is important so that at least small amounts of ATP can be generated during ethanol fermentation

glucose + 2 ADP + 2 Pi -> 2 ethanol + 2 CO2 + 2 ATP + 2 H2O

48
Q

Excess sugar storage

A
  • plants and animals can store excess glucose for use in glycolysis later as branched polymers of glucose
  • glucose monomers are cleaved one at a time and enter glycolysis as an intermediate
  • plants store it as STARCH
  • animals store it as GLYCOGEN
    – stored in muscle cells for energy to power contraction
    – stored in liver for the whole body
49
Q

What about other sugars?

A
  • the carbohydrates that are digested can produce a variety of disaccharides and monosaccharides
  • may produce glucose or other glycolysis intermediates
50
Q

What about other energy sources?

A
  • lipids are an excellent energy source, rich in C-C bonds and C-H bonds
  • fatty acids absorbed after a meal, or produced from excess glucose can be used by cells
    – they are shortened through beta-oxidation
51
Q

What is beta-oxidation?

A

in beta-oxidation lipids are broken down into glycerol and acetyl-CoA
– ATP is not produced directly
– NADH and FADH2 are produced and can enter

Biol 130 (11 decks)

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