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WBiology > Cellular Respiration > Flashcards

Cellular Respiration Flashcards

1
Q

What is cellular energetics?

A

The study of energy metabolism in a cell or the transformation/transfer of energy

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2
Q

What is nicotinamide adenine dinucleotide? What does it do?

A

Coenzyme that accepts excited electron (H atom) from one molecule and transfers it to another via enzyme catalyzed redox reaction

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3
Q

What are the forms of nicotinamide adenine dinucleotide? Which is more energized?

A

a) NAD+
- Oxidized form (lost an H)
- Oxidizing agent in reaction

b) NADH
- Reduced form (gained an electron)
- Reducing agent in reaction
- More energized form as it’s gained 2 excited electrons

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4
Q

What is adenosine triphosphate? What does it do? What is its reaction?

A

Molecule that transforms energy by coupling

ATP = ATP + Pi

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5
Q

What is the structure of ATP? How is it used?

A
  • Adenine
  • Ribose
  • 3 phosphate groups

2 terminal phosphates are joined with high energy/reactive bonds that have low activation energy so transferred easily

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6
Q

How are coupled reactions indicated?

A

With a swoop

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7
Q

What are coupled reactions used for?

A
  • Mechanical work (eg. muscle contraction)
  • Transport work (eg. active transport pumps)
  • Chemical work (eg. protein synthesis)
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8
Q

How is ATP regenerated?

A

ATP is regenerated by phosphorylating ADP which is endergonic and requires the input of more than 30.5 kJ/mol

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9
Q

What is a redox reaction? What happens?

A
  • Transfer of excited electrons
  • Electron in elevated energy level maintains its energy when transferred to other molecules
  • Increases free energy of receiving molecule
  • Electron is often accompanied by proton (so a hydrogen ATOM is transferred)
  • Reactions involve the loss and gain of hydrogen
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10
Q

What is a phosphorylation reaction? What is a molecule called involved? What are the types of phosphates?

A
  • Transfer of phosphate group from ATP to a molecule (ATP = ADP + Pi)
  • Phosphates can be inorganic (Pi) or high energy (ATP)
  • Increases free energy of receiving molecule
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11
Q

What is the hydrolysis of ATP for? What happens? What does it produce?

A
  • Releases large sum of energy
  • Exergonic, with free energy of -30.5 kJ/mol under standard conditions
  • Coupled with endergonic reactions
  • Transfers terminal phosphate of ATP to another molecule during enzyme catalyzed reaction
  • Produces phosphorylated intermediate (higher free energy and more unstable)
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12
Q

What is the reaction pathway for cellular respiration?

A
  1. Glycolysis: anaerobic breakdown of glucose into 2 molecules of pyruvate (cytosol)
  2. Krebs Cycle: cyclical pathway that captures high energy electrons
  3. Electron Transport Chain: series of redox reactions that supply energy for oxidative phosphorylation
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13
Q

Does glycolysis lose carbons?

A

No. 6C from glucose to 2 molecules of pyruvate (3C each).

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14
Q

When does fermentation occur? What does it do? Is it efficient?

A
  • Occurs under anaerobic conditions (no O2)
  • Prevents the glycolytic pathway from stopping by regenerating NAD+
  • Very inefficient (2 ATP x 30.5kJ/mol over 2870 kJ/mol = 2%) even with glycogen (3 ADP = 3%)
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15
Q

What is fermentation for multicellular organisms called? What happens? What are the consequences?

A

Lactate Fermentation

Pyruvate → Lactic acid
NADH → NAD+ coupled

Lactic acid reduces pH of cell which affects enzyme conformation.

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16
Q

What is fermentation for single celled organisms called? What happens? What are the consequences?

A

Alcohol Fermentation

Pyruvate → Acetaldehyde (2C) → Ethanol
NADH → NAD+ coupled
The 1 C is lost to CO2 (decarboxylation, lost oxygen too)

Ethanol is toxic after 11% so organism must be small and live in aqueous environment so it can diffuse out.

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17
Q

Where do glycolysis/krebs/ETC take place?

A

Glycolysis: cytosol
Krebs: matrix
ETC: inner mitochondrial membrane

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18
Q

What is the reaction for pyruvate oxidation?

A

Pyruvate (3C) = Acetyl COA (2C)
1C leaves as CO2
COA comes in
NAD+ = NADH coupled

Catalyzed by multi-enzyme complex called pyruvate dehydrogenase

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19
Q

What are the coenzymes involved with Krebs cycle?

A
  • NAD+: electron shuttle (2e makes NADH; one H to neutralize)
  • FAD: electron shuttle (2e = FADH2)
  • CoA: makes molecules reactive, signal something important will happen
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20
Q

What is the electron transport chain?

A

Series of protein bound to inner mitochondrial membrane transfer electrons between them via redox reactions

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21
Q

What is the process for the ETC?

A
  • Electrons are transferred by NADH and FADH2 using redox reactions
  • 3 proteins are coupled to proton pumps
  • Free energy change in redox reaction provides energy to transfer H ions from matrix to intermembrane space
  • Proton gradient (proton motive force) is created with H ion concentration higher in intermembrane space than matrix
  • Final electron acceptor is O2
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22
Q

Why do you need a final electron acceptor for ETC?

A

Must be there or else no way to oxidize last cytochrome (protein with a heme group) so it can’t accept electrons from previous protein

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23
Q

Where does NADH and FADH2 enter for ETC?

A
  • NADH enters at 1st protein: activates 3 pumps

- FADH2 enters at 2nd protein: activates 2 pumps

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24
Q

What is chemiosmosis?

A

process that uses chemical potential to do cellular work (eg. ETC)

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25
Q

How much ATP is created and which method during cellular respiration?

A

Total of 36; 2 from glycolysis (SLP), 2 from Krebs (SLP), 32 from ETC (OP)

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26
Q

Where does the equation for cellular respiration come from?

A

C6H12O6 + 6 O2 = 6 H2) + 6 CO2 + ATP

Glucose + Electron Acceptor (12 Hs need 1/2 O2) = 6 H2O (6O2 forms water) + 6 CO2 (6 C of glucose end up as CO2) + ATP

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27
Q

What is ATP synthase?

A

Transmembrane protein in inner mitochondrial membrane

28
Q

Summarize what goes into and out of each of the 3 processes.

A

Glycolysis: Glucose = 2 Pyruvate + 2 ATP + 2 NADH

Krebs: 2 Pyruvate = 6 CO2 + 2 ATP + 8 NADH + 2 FADH2

ETC: 10 NADH + 2 FADH2 + O2 = 6 H2O + 32 ATP

29
Q

What are some aspects of cellular respiration that show the structure-function relationship?

A
  • Space between intermembrane space and matrix allows for concentration gradient as ions can’t get through the member
  • ATP channel allows ATP to exit mitochondria for cell to use
  • Binding of proteins in ETC ensures electrons are transferred in order in inner membrane
  • Folding of cristae increases surface area which means many copies of ETC
  • Outer membrane establishes inner memrane space
30
Q

What is the purpose of cellular respiration?

A

To slowly release the chemical potential energy in food through a series of enzyme catalyzed reactions and capture some of the energy in a usable form (ATP) for endergonic reactions.

31
Q

Where does the food for cellular respiration come from?

A

Heterotrophs: must eat to obtain substrate for cellular respiration

Autotrophs: make food for cellular respiration through process of photosynthesis; still make energy for metabolic processes by cellular respiration

32
Q

What is the purpose of photosynthesis?

A

To produce molecules that can be used as substrate for cellular respiration and for synthetic pathways (eg. proteins, cell walls).

33
Q

What are the requirements of photosynthesis?

A
  • Energy (ATP in chemical reactions): needs to be generated from light
  • Carbon source: atmospheric CO2 through stroma
  • Reducing Power: must supply H to break double bonds; uses electron carrier NADP+ (oxidized) to NADPH (reduced)
34
Q

What are pigments? Why are they able to do their job? What happens to the light absorbed by a pigment? Are the absorption spectrums identical?

A
  • Molecules that absorb light
  • Occurs due to arrangement of bonds in molecules (chains of Cs so hydrophobic)
  • Has unique absorption spectrum because energy required to excite electron is exact
  • Any light that is not absorbed is reflected; therefore pigment appears that colour
35
Q

More specifically, what is a photosynthetic pigment?

A

Any pigment that absorbs solar energy for photosynthesis

36
Q

What is chlorophyll a? What does it absorb? What is its structure?

A
  • Major photosynthetic pigment that is present in all organisms that can photosynthesize
  • Has porphyrin ring head that has Mg2+ in center and hydrocarbon tail
  • Absorbs in blue-violet and red portion of spectrum
37
Q

What do accessory pigments do? What are the types?

A

Absorb wavelengths that chlorophyll a cannot, increasing efficiency of light absorption and creates action spectrum broader than chlorophyll a spectrum

Chlorophyll b: similar absorption to chlorophyll a except has 1 function group different; results in slightly different absorption spectrum

Carotenoids

Xanthophylls

38
Q

What are the types of graphs for pigment?

A

Absorption Spectrum: series of wavelengths that can be absorbed by pigment

Action Spectrum: graph showing rate of photosynthesis at different wavelengths

39
Q

What is the structure of chloroplasts?

A
  • 2 membranes and thylakoid (disc) and stroma (fluid)
  • Contains pigment molecules
  • Hydrophobic
40
Q

What are some aspects of photosynthesis that show the structure-function relationship?

A
  • Thylakoid surface area is increased by stacked as flattened discs called grana
  • Pigments are hydrophobic so located in thylakoid membrane
  • Capture of light is made efficient by organization of pigments into photosystems
  • Protein Z
  • There is a system for cyclic for more ATP
  • CO2 enters through stroma
  • Products of light and dark reactions can be used for each other
  • Separation for H+ concentration gradient to build up
41
Q

What is a general summary of the photosynthetic pathway?

A
  1. Light Reactions
    - Require light which is absorbed by photosynthetic pigment molecules
    - Produce NADPH and ATP
  2. Calvin Cycle
    - Incorporates CO2 into organic molecules such as G3P (carbon fixation)
    - Require energy of ATP and reducing powder of NADPH (endergonic)
42
Q

What makes up the light reactions?

A
  • Photoexcitation
  • ETC
  • Chemiosmosis
43
Q

What happens during photoexcitation?

A
  • Light strikes pigment molecules, exciting electrons
  • Pigments of antenna complex absorbs photons and transfers the energy to reaction centre
  • When 2 photons are transferred to reaction centre, the P680 or P700 molecule loses 2 electrons (oxidized = missing electrons that must be replaced)
44
Q

What is a photosystem? What are the 2 types? What should you consider about the 2 chlorophyll a pigments?

A

complex of chlorophyll, proteins, and other organic molecules within thylakoid membrane

PS I: P700 which absorbs maximally at 700 nm

PS II: P680 which absorbs maximally at 680nm

Each photosystem has unique primary electron acceptors

45
Q

What is the antenna centre?

A

part of photosystem that absorbs light and transfers it to reaction centre

46
Q

What is the reaction centre?

A

just the chlorophyll a and the primary electron acceptor

47
Q

How does energy transform throughout photosynthesis?

A
  • Light energy is transformed into energy in excited electrons
  • Energy in excited electrons is transformed into a H+ concentration gradient
  • Energy in H+ concentration gradient is transformed into chemical potential energy as ATP
48
Q

What is the process of non-cyclic electron flow?

A
  • Electrons of PS II go through ETC, pumping protons
  • Electrons go to PS I, replacing its electrons lost
  • PS I ejects elecrtons to go through ETC
  • Final electron acceptor is NADP+, resting electron acceptor is NADPH
49
Q

What is the process of cyclic electron flow?

A
  • Final electron acceptor is P700
  • Electrons to replace ejected electrons come from P700
  • Electron ejected from P700 is passed to ferredoxin (PS I ETC protein) and continues down PS II ETC chain to protein pump then P700
50
Q

What happens during chemiosmosis?

A
  • Both cyclic and non-cyclic electron flow supply energy to pump protons
  • Energy in electron is used to pump H+, which results in [H+] gradient used by ATP synthase (ADP + Pi = ATP)
51
Q

Where does the electrons to replace the ones lost by P680 come from?

A
  • Electrons to replace ejected electrons for - PS II come from H2O
  • Protein Z (PS II) splits H2O into ½ O2 (leaves cell), 2 H+ (remain in thylakoid space), and 2 e (P680)
  • Requires light energy
52
Q

What does each type of electron flow produce and which photosystems are used?

A

Non-Cyclic:

  • Uses both photosystems
  • Produces both ATP (PS II) and NADPH (PS I)

Cyclic:

  • Uses PS I
  • Produces only ATP
53
Q

Where does the Calvin cycle take place?

A

Stroma

54
Q

What are the 3 phases of the Calvin cycle and what happens (products, reactants, etc.)?

A
  1. Carbon Fixation
    - CO2 is added to RuBP (5C sugar) which is catalyzed by rubisco (enzyme)
    - 3 CO2 and 3 RuBP must be used
  2. Reduction Reactions
    - ATP energizes (phosphorylation)
    - NADPH reduces intermediate (reducing power)
    - 1 G3P exits
    - Undergoes reverse glycolysis in cytosol (G3P + G3P = Glucose)
  3. RuBP Regeneration
    - 5 G3P remain and are rearranged to regenerate 3 RuBP
    - Requires 3 ATP
55
Q

What is the equation for photosynthesis and why is it like so?

A

6 CO2 + 12 H2O = C6H12O6 + 6 O2 + 6 H2O

CO2: used in Calvin cycle to produce G3P, which requires ATP and NADPH

Water: supplies electrons in PS II

O2: generated when H2O is broken down

56
Q

In the end, where does glucose come from and how many ATP and NADPH are required?

A

G3P + G3P in reverse glycolysis in cytosol

Needs 18 ATP and 12 NADPH

57
Q

What molecule contains the greatest amount of chemical potential energy?

A

Pyruvate

58
Q

How do you get the energy for ATP synthesis?

A
  1. Substrate Level Phosphorylation: the usage of an exergonic reaction to supply energy needed to phosphorylate ADP (eg. PEP to Pyruvate)
  2. Oxidative Phosphorylation: uses energy in a proton concentration gradient to supply energy to phosphorylate ADP
59
Q

Which of the two reactions studied is catabolic and which is anabolic?

A

Cellular Respiration: catabolic

Photosynthesis: anabolic

60
Q

Photosynthesis is a redox reaction; what is oxidized and reduced?

A

Glucose: oxidized
Oxygen: reduced

61
Q

Can cells store large amounts of ATP?

A

No as ATP is very unstable and will break down at any given moment.

62
Q

How is cellular respiration controlled?

A

With allosteric enzymes working with indicators noting in a decrease of ATP and increase of ADP/Pi (needs energy) as well as a decrease of NAD+ and increase in NADH (need O2).

63
Q

What are examples of the control of cellular respiration?

A

Glucose = Glucose-6-Phosphate is inhibited if builds up

Glucose-6-Phosphate = Fructose-1,6-Bisphosphate is activated if energy is needed and inhibited if not

Isocitrate = Alpha-Ketoglutarate is “ and also activated if O2 is high and inhibited if not

64
Q

Why can’t humans undergo photosynthesis since it’s so efficient?

A

Humans are far too large

65
Q

Where do the reactions occur for photosynthesis?

A

Light Reactions: thylakoid membrane

Calvin Cycle: stroma

66
Q

Does FADH2 have more or less energy than NADH?

A

Less

67
Q

How is pyruvate transported into the mitochondria?

A

Facilitated diffusion

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