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BIOL 107 > Week 8 Recall Questions > Flashcards

Week 8 Recall Questions Flashcards

1
Q

What are overall similarities and differences between photosynthesis and cellular respiration?

What are the respective reactants and products?

Which molecules get reduced and which ones get oxidized
in each process?

A
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2
Q

What is the purpose of cellular respiration?

A

To use the energy released my oxidation process to power phoshporylation of ADP to ATP.
—( if able to use mitochondria)

— 32 ATP

  • Catabolic process

Fate of organic molecules:
1. Used to make ATP to power cellular work
2. Used to make carbon-based molecules
• Proteins, fats, carbohydrates, etc.
Used for growth, repair, and reproduction

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2
Q

What kind of organism are able to perform cellular respiration?

A
  • Carried out by:
    — all eukaryotes, including plants
    — some bacteria
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3
Q

What is the overall equation of cellular respiration?

Which parts get oxidized and which get reduced?

A

• C6H12O6 + 6O2 —> 6CO2 + 6H2O + energy

— C6H12O6 oxidatized to CO2
— 6O2 reduced to H2O

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4
Q

Why is cellular respiration critical for the evolution of higher/more complex life?

A

• Eukaryotic organisms and archaea only able to do 1st stage by self = glycolysis.

• mitochondria —> alpha protcobacterial descendants —> live in eukaryotic cells —> they are what does cellular respiration = enables life as we know it.
|
— > b/c not able to power anything as complex as ourselves with the 2 ATP molecules we are able to get out of respiration.

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5
Q

What are the 4 important stages of cellular respiration?

What is the function of each stage?

What are the reactants and what are the products?

Where is each step located in the cell?

A
  1. Glycolysis
    • Location: Cytosol
    • Process/Function: Breaks glucose down into pyruvate
    • Produces: ATP and NADH
    • Does NOT require oxygen
  2. Pyruvate Oxidation
    • Location: Mitochondrial matrix
    • Process/Function: Pyruvate is oxidized into Acetyl-CoA
    • Produces: NADH and CO2
  3. Citric Acid Cycle
    • Location: Mitochondrial matrix
    • Process/Function: Acetyl-CoA is oxidized into CO2
    • Produces: ATP, NADH, FADH, and CO2
  4. Oxidative Phosphorylation
    • Location: Inner mitochondrial membrane
    • Process/Function: Energy from NADH and FADH, is used to produce ATP
    • Produces: Lots of ATP
    • Requires: O2. B/c is terminal electron acceptor
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6
Q

Why does cellular respiration involve multiple steps?

A

The purpose with the multiple steps involved in respiration is to allow for a step-wise release of energy that allows for effective conversion to ATP-bound energy (capture of the released energy).

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7
Q

What is the overall reaction/equation of glycolysis?

A

• Splits glucose (6 carbons) into 2 pyruvates (3 carbons each)

• 1 glucose —> 2 pyruvate
• 4 ATP generated - 2 ATP used —> 2 ATP
• 2 NAD+ + 4 e- + 4 H+ —> 2 NADH+ + 2 H2O

Energy requiring rxns
1 Glucose (6 carbon) + (2 ATP —> 2 ADP + 2 pi) —> 2 G3P (3 carbon)

Energy releasing rxns
—> (2 NAD+ + 4 e- + 4 H+ —> 2 NADH+) —> (4 ADP + 4 pi —> 4 ATP) —> 2 pyruvate (3 carbon) + 2 H2O

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8
Q

What are the two phases or stages of glycolysis?

What are the initial reactants and what is the final product for each phase (which molecules enter each stage; what molecule is produced)?

A
  1. Energy-Requiring Reactions
    • 4-5 reactions, each catalyzed by an enzyme
    • Converts 1 glucose molecule to 2 G3P molecules
    • Uses two ATP
  2. Energy-Releasing Reactions
    • 5 reactions, each catalyzed by an enzyme
    • Converts 2 G3P molecules to 2 pyruvate
    • produces 4 ATP (substrate level phosphorylation)
    • Reduces 2 NAD+ to NADH
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9
Q

Which three general types of enzyme are involved in glycolysis?

A

• Kinases - transfers phosphate from one molecule to another

• Isomerases - rearrange atoms

• Dehydrogenases - transfer electrons to shuttle molecules

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10
Q

How is ATP produced in glycolysis and how many ATP are produced per glucose molecule?

A

ATP is created directly from Substrate-level phosphorylation:
• Kinase transfers a phosphate group from a high-energy substrate molecule to ADP —> makes ATP

ATP is created indirectly by oxidative phosphorylation.

Net Outcome of Glycolysis:
• Glucose oxidized to 2 pyruvate
- Electrons transferred to 2 NAD+ —> 2 NADH
• 4 ATP made - 2 ATP used = 2 ATP net
• Made by substrate-level phosphorylation a 1 glucose —> 2 pyruvate + 2 ATP + 2 NADH

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11
Q

What kind of electron carriers are produced in glycolysis and how many?

A

NADH

2 NADH for every 1 glucose molecule
(From NAD+)

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12
Q

After glycolysis, what are possible pathways for pyruvate?

A

Lots of energy still left in pyruvate
- What happens next depends on oxygen
• O2 absent - fermentation
• O2 present - aerobic respiration

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13
Q

What is an obligate aerobe and facultative anaerobe organism?

A

Obligate aerobe:
• Only respiration

• Facultative anaerobe:
• Prefers respiration
• Switches to fermentation when O2 not available

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14
Q

What is fermentation and where is the cell does it take place?

A

Alternative to cellular respiration.
— another pathway for breaking down glucose.

• Location: Cytosol

• Pyruvate stays in cytosol and undergoes fermentation

• Occurs in anaerobic conditions (No O2)

• Doesn’t require O2, an ETC, or mitochondria

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15
Q

Under what conditions does fermentation occur and what it its function?

A

• Function of Fermentation: Recycling NADH
• GIycolysis occurs without O2
• Glucose + 2 ADP + 2 NAD+ —> 2 pyruvate + 2 ATP + 2 NADH.

• Fermentation recycles NADH back to NAD+ so it can be reused in glycolysis
• No additional ATP is produced!

— NAD+ acts as electron receptor = oxidizing agent in glycolysis.
— this oxidation is coupled with something.
That’s what fermentation is about, recycles NADH back to NAD+ so we can reuse it and make more NADH

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16
Q

What are the advantages and drawbacks of fermentation?

A

• Provides a boost of energy when oxygen is not available

• b/c it’s only purpose is to recycle some NADH to NAD+, energy is wasted and released as heat.

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17
Q

What is the reactant of fermentation and what are two products?

A

Starting Compound: Pyruvate
• Produced by glycolysis.

Terminal Electron Acceptor: Organic molecules.
• i.e. where the electrons from NADH end up a NOT O2

End Products: Characteristic organic molecules
• Not just CO2 and H2O
• In eukaryotes (and many prokaryotes): ethanol or lactic acid

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18
Q

What is alcoholic fermentation?

What is it used for and what is the terminal electron acceptor?

A

Pyruvate is converted to ethanol (Acetaldehyde) and CO2
• Organisms:
— Bacteria, yeast, fungi

• Uses:
— Brewing, breadmaking

• terminal electron acceptor: Acetaldehyde (2 carbons) accepts electron from NADH + H+ —> ethyl alcohol

Then get NAD+ produced

CO2 removed from end to get ^

• double bonded oxygen in Acetaldehyde is what allows the carbon to react with protons of NADH and H+.
— when break double bond, have 1 available orbital on oxygen and 1 available on carbon
— so proton attaches to carbon = H-C bond
— other proton attaches to Oxygen.

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19
Q

What is lactic acid fermentation?

What is it used for and what is the terminal electron acceptor?

A

Pyruvate is reduced to lactate in one step
• No CO2 produced
Uses:
— Cheese, yogurt, sauerkraut

Organisms:
• Bacteria, fungi, animal muscle cells

• terminal electron acceptor: pyruvate

• don’t have to convert pyruvate to other molecules first
• can have it reacting directly with NADH + H^+ —> lactate (3 carbon)

• NAD+ produced

• proton from NADH and H+ reacting with double bond between carbon and oxygen (C=O)

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20
Q

What are two differences between ethanolic and lactic acid fermentation?

A
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21
Q

What is the net energy production from fermentation and how does this compare to cellular respiration?

A

Net Reaction:
• Glucose + 2 NAD+ —> 2 pyruvate + 2 NADH + 2 ATP —> organic molecules + 2 NAD+ (which goes back to the first section of this rxn)

Net Energy Production:
• 2 ATP from glycolysis (vs. 32 ATP from cellular respiration)

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22
Q

What is pyruvate oxidation and where does it take place?

A

• Pyruvate is converted to Acetyl-CoA
— Only in the presence of O2
Location:
— Mitochondrial matrix
(immediately adjacent to the inner membrane)

23
Q

What is the reactant in pyruvate oxidation and what are the products?

A

• Reactants:
— Pyruvate
— Pyruvate dehydrogenase

• Products:
— Acetyl-CoA

24
Q

Which enzyme catalyzes this pathway and what electron carrier is involved?

A

• Pyruvate dehydrogenase
—Membrane protein complex
— Catalyzes a three-step reaction

• NAD+ is reduced
• CoA is oxidized

  1. Carboxyl group is removed from pyruvate and released as CO2
  2. Remaining 2-carbon molecule is oxidized to make acetate
    • Electrons transferred to NAD+
    • 1 NADH produced per pyruvate
  3. Coenzyme A is added to acetate
    • Attached by unstable (high energy) bond
    • Forms acetyl-CoA
25
Q

What is the function of Coenzyme A in this process?

A

Coenzyme A is added to acetate
• Attached by unstable (high energy) bond
• Forms acetyl-CoA

26
Q

What is the overall unbalanced equation for this process?

A

For 1 glucose molecule:
• 2 pyruvate -› 2 acetyl-CoA + 2 NADH + 2 CO2

• 1NADH/pyruvate (2 NADH/glucose)

27
Q

What is the citric acid cycle and where does it take place?

A

• A series of chemical reactions in which the starting material is regenerated
— Each step catalyzed by an enzyme

• Location: Mitochondrial matrix

28
Q

What is the overall purpose of the citric acid cycle (CAC)?

A

• Purposes:
1. Oxidize acetyl-CoA into CO2
2. Transfer high energy electrons to shuttle molecules (used later for ATP production)
3. Produce ATP by substrate-level phosphorylation

29
Q

What molecules are the starting point of the CAC and which one needs to be regenerated?

A

• Acetyl-CoA + Oxaloacetic acid —> CoA + Citrate.

30
Q

What is the “energy outcome” (net production of energy carriers) of the CAC?

What and how many of each energy carriers are being produced?

A

Net reaction:
• 1 acetyl-CoA -› 2 CO2 + 3 NADH + 1 FADH2 + 1 ATP

Per glucose:
• 2 acetyl-CoA -› 4 CO2 + 6 NADH + 2 FADH2 + 2 ATP

Energy production:
– 1ATP/acetyl-CoA
(2 ATP /glucose)
by substrate-level phosphorylation

– 3NADH/acetyl-CoA
(6 NADH/glucose)
by dehydrogenase enzymes

– 1FADH2/acetyl-CoA
(2 FADH2/glucose)
by dehydrogenase enzymes

31
Q

How is ATP produced and how many per pyruvate?

A

• Energy is released by electrons moving down an electron transport chain (ETC) and used to produce a proton gradient

• Proton gradient is used to make ATP by chemiosmosis

• Makes ATP by coupling hydrolysis of GTP to GDP. Then GDP with the phosphorylation of ADP to ATP.
—> this is substrate phosphorylation where a kinase enzyme catalyzes the transfer of the phosphate group from GTP to ATP.
• GDP + Pi —> GTP —> ADP —> ATP.

2 ATP produced per Glucose molecule.

1 ATP produced per pyruvate molecule.

32
Q

Where is the mitochondrial ETC located?

A

Inner Mitochondrial Membrane

Definition: A series of electron-carrying membrane proteins that transfer electrons and release energy

• Receive high energy electrons (from electron shuttles)

33
Q

What are the parts (complexes etc) of the mitochondrial ETC?

A

Membrane-bound protein complexes with embedded non-protein electron carriers.

34
Q

Which of the parts function as a proton pump?

Where are the protons being pumped to?

A

Energy is used to actively transport protons from the matrix to the intermembrane space
• Complex 1, Coenzyme Q, and Complex 4 are H+ pumps

H+ gradient forms across inner mitochondrial membrane

35
Q

Why do protein gradients need to be associated with a membrane?

A

B/c the flow of electrons (electron current) is used to power proton pumps.

• against protons gradient = builds up = potential energy = released to power ATP synthase.

• also b/c electrons in proteins don’t have the ability to have “jump around”, something is needed to act as a “wire” b/c they need to be able to gain and lose electrons. = prosthetic groups

36
Q

Can you identify the redox reactions in this ETC? Give 2 examples.

A
37
Q

What is/are the source of the electrons for this ETC?

What is their ‘original’ source (during the process of cellular respiration) and at what stage were the electrons transferred to a carrier?

A

NADH
• From glycolysis, pyruvate oxidation, and Citric Acid cycle

FADH2
• From Citric Acid cycle

38
Q

What is the function of prosthetic groups in the complexes?

A

They convalently bond to proteins

• they themselves aren’t amino acids = non- AA Group that are a part of protein and prosthetic group.
—> associates with protein complexes, have a metal centre capable of receiving and passing on electrons

39
Q

What complex does NADH donate the high energy electrons to?

A

NADH to Complex 1 (at high energy)

• 3 H+ pumping events
• Enough energy to make ~2.5 ATP

40
Q

What complex does FADH2 donate the high energy electrons to?

A

FADH2 to Complex 2 (lower energy than NADH)

• 2 H+ pumping events
• Enough energy to make -1.5 ATP

41
Q

What is the terminal electron acceptor in this chain?

How many e- are accepted?

A

O2: Terminal electron acceptor (TEA; end destination of e-)

42
Q

What is the source of the protons being pumped across the membrane?

A

Energy associated with the transfer of electrons down the electron transport chain is used to pump protons from the mitochondrial matrix into the intermembrane space, creating an electrochemical proton gradient.

43
Q

How is this electrochemical gradient used to produce ATP?

A

Protons flow down their concentration gradient into the matrix through the membrane protein ATP synthase, causing it to spin (like a water wheel) and catalyze conversion of ADP to ATP.

The proton gradient produced by proton pumping during the electron transport chain is used to synthesize ATP.

44
Q

What is the direction of the proton flow through ATP synthase?

A

Protons flow down their concentration gradient into the matrix through the ATP synthase from the intermembrane space.

45
Q

Why is this process referred to as oxidative phosphorylation?

Where in the mitochondrion is it located?

A

Released energy is used to drive
ADP + P, -> ATP reaction
• Called oxidative phosphorylation because energy comes from glucose oxidation
• Occurs in matrix

46
Q

Why are less ATP produced from FADH2 electron than from NADH electrons?

A

The electrons for FADH2 are dropped off at complex || (succinate dehydrogenase complex) of the electron transport chain.
- Which doesn’t directly/actively transport protons.

but also b/c it doesn’t transfer its electrons to the 1st complex.
— NADH does, and it has more energetic electrons.

Therefore, when the electrons of FADH2 are dropped off at complex 2 they produce a lower proton gradient and don’t supply ATP synthase with as much energy as NADH.

47
Q

How do you explain the discrepancy of the overall energy stored in Glucose (686 kcal/mol) and stored in 32 ATP (234kcal/mol) being produced by cellular respiration?

Where did the remaining energy go?

A

C6H12O6 + 6 O2 - 6 CO2 + 6 H2O
• 🔺G = -686 kcal/mol

• Cellular respiration produces ~32 ATP
• 1 ATP: G = 7,3 kcal/mol
• 32 ATP : G = 234 kcal/mol
• Only 34% of energy in glucose is captured

• rest is lost as heat.

48
Q

What are the general fuel sources for cellular respiration?

A

• Carbohydrates
— Glucose

• Fats

• Proteins

49
Q

How do these fuels enter the pathways of cellular respiration?

How and where do starch, glycogen, fructose, fats and proteins enter the metabolic pathways?

A

Carbohydrates:
• Starch and glycogen broken down to glucose by amylase
— Breaks 1-4 glycosidic linkages
• Enters glycolysis as glucose

Other sugars can be used
• Converted into intermediates
• Enter glycolysis at later steps
— Ex: Fructose, Sucrose

Proteins:
• Digested into amino acids by protease enzymes
— remaining 2 carbons put into citric acid cycle
• Amino group removed by deamination
• NH3 excreted in urine
• Carbon portion enters glycolysis at a early stage or TCA cycle if the AA has a large R-Group (more C-chains)

Fats:
• First digested into glycerol and fatty acids
• Glycerol is converted to G3P (glyceraldehyde-3-phosphate)
• Enters glycolysis
• Fatty acids are broken down, by beta-oxidation into acetyl-CoA
• Enter Citric Acid Cycle

50
Q

How are metabolic pathways regulated by the cell?

A

Regulation: The process of adjusting and controlling the cell’s activities.

Intermediate steps of metabolic pathways regulated by controlling their rate of reaction by controlling enzyme activity.

If there is enough ATP in the cell, glycolysis and the citric acid cycle are turned off
— Controlled by activators and inhibitors.

Regulation occurs at phosphofructokinase (PFK)
— Enzyme from early in glycolysis

51
Q

What is feedback inhibition? Give examples from this topic

A

End product of a metabolic pathway inhibits an enzyme that catalyzes an early step in the pathway.

Conserves resources and energy when more end product not needed.

52
Q

What is allosteric regulation? Give examples from this topic.

A

Function of an enzyme is affected (inhibited or activated) by the binding of a molecule at a site other than the enzyme’s active site.

• Inhibitors and activators may compete for the same allosteric site.

• ATP and ADP are allosteric regulators of PFK
— Compete for binding to the same allosteric site in PFK

53
Q

By regulating phosphofructokinase, which part of cellular respiration is controlled?

A

Glycolysis

Important to regulate b/c:
— Not burning off glucose crazily if you don’t need more ATP
— Not running glycolysis or anaerobic respiration at too low a rate = depletion of ATP
— want at right rate to get right amount of ATP molecules produced per unit time

54
Q

How do ATP and ADP interact with phosphofructokinase and what effect does this have on cellular respiration as a whole?

A

ATP is an inhibitor of PFK
-› decreases enzyme activity (feedback inhibition)

ADP is an activator of PFK
-› increases enzyme activity

55
Q

What role does citric acid play in the regulation of phosphofructokinase?

A

Citric Acid
• Product of first step of the Citric Acid Cycle

• Inhibitor of PFK -› decreases enzyme activity (by feedback inhibition)

BIOL 107 (48 decks)

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