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Molecular Cell Biology > (1) Chapter 3: Cell Metabolism > Flashcards

(1) Chapter 3: Cell Metabolism Flashcards

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1
Q

Thermodynamically unfavorable biological reaction

A

Change in G > 0. these reactions use energy to generate an end product

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2
Q

Thermodynamically favorable biological reaction

A

Change in G

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3
Q

Thermodynamically favorable and unfavorable reactions can combine to form _____reactions?

A

very efficient.

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4
Q

Main function of ATP

A

(adenosine 5’-triphosphate) ATP.

-stores free energy in the cell

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5
Q

What occurs as bonds between phosphates of ATP break?

A

-bonds are broken by hydrolysis and release a large amount of free energy

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6
Q

Hydrolysis of ATP to AMP and PPi

A

-ATP can be hydrolyzed to AMP & Pyrophosphate (PPi), then PPi is rapidly hydrolyzed and the total free-energy change is double than the hydrolysis from ATP to ADP

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7
Q

Energy yielding reactions within the cell are coupled to _____

A

ATP synthesis

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8
Q

Energy-requiring reactions are coupled to _____

A

ATP hydrolysis

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9
Q

The complete breakdown of glucose to CO2 and H2O yields how much free energy?

A

-686 kcal/mol

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10
Q

Glycolysis

A
  • 1st stage of ATP synthesis
  • takes place in cytosol
  • inhibited if there is an adequate supply of ATP
  • provides all metabolic energy of anaerobic organisms
  • occurs in all cells in the absence of oxygen.
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11
Q

What is the result of Glycolysis?

A
  • breakdown of glucose into pyruvate
  • net gain of 2 ATP
  • Gain 2NADH from NAD+
  • uses 2ATP to start process
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12
Q

In Anaerobic glycolysis conditions what happens to NADH?

A

NADH is reoxidized to NAD+ by conversion of pyruvate to lactate/ ethanol/ or Acetaldehyde

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13
Q

In aerobic glycolysis conditions, what happens to NADH?

A

NADH donates electrons to the electron transport chain

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14
Q

What happens to pyruvate after aerobic glycolysis?

A

Pyruvate enters mitochondria and is converted to acetyl CoA

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15
Q

How is Acetyl CoA formed? What is a byproduct?

A
  • pyruvate enters mitochodria and undergoes oxidative decarboxylation when coenzyme A & NAD+ is present
  • Generates acetyl CoA, 2NADH, and CO2
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16
Q

What happens to Acetyl CoA after it is synthesized?

A
  • enters citric acid cycle (Kreb’s cycle)

- Citrate (6C) is formed after Acetyl CoA binds with oxaloacetate.

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17
Q

What happens to Citrate in the Kreb’s cycle?

A

2 C’s of Citrate are oxidized to CO2 and Oxaloacetate is regenerated

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18
Q

Where does the citric acid cycle take place?

A

mitochondria

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19
Q

What are the products of the Kreb’s cycle?

A

after one turn:

  • 2 CO2, 1 oxaloacetate, 1 GTP, 3NADH, 1 FADH2
  • products double after the 2nd turn
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20
Q

FADH2

A
  • Flavin adenine dinucloetide

- an electron carrier

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21
Q

List products after oxidation of glucose and name what process they are from

A
  • Total ATP: 36-38
  • GLycolysis: 2 ATP and 2 NADH
  • Citric Acid Cycle: 2 ATP, 6 NADH, 2 FADH
  • Oxidative phosphorylation: 30 ATP from NADH, 4 ATP from FADH
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22
Q

In oxidative phosphorylation which electron carriers produce ATP and what amount to they produce?

A

NADH yields 3 ATP: so produces 30

FADH2 yields 2 ATP: so produces 4

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23
Q

What other molecules besides glucose can break down to yield energy?

A
  • polysaccharides can be broken down to sugars in order to metabolized by glycolysis and the krebs cycle.
  • lipids can be oxidized to yield a whole lot of energy
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24
Q

Describe the process of triacylglycerol break down to produce ATP

A
  • Fats are broken down into glycerol and free fatty acids
  • fatty acids bind to coenzyme A
  • Acyl-CoA is formed using 1 ATP
  • Fatty acids are degraded in stepwise oxidative process, 2 carbons at a time.
  • each round of oxidation yields 1 NADH and one FADH2
  • acetylCoA then enters citric Acid cycle.
  • net gain is 130 ATP per 16 C fatty acid
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25
Q

What processes derive the most energy from the breakdown of macromolecules?

A
  • electron transport

- oxidative phosphorylation

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26
Q

In general, what happens to electrons carried by electron transporters during oxidative phosphorylation?

A

-Electrons from NADH and FADH2 are transferred to O2, which is coupled to the formation of 34 ATP

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27
Q

How are the components of the etc organized?

A

-four complexes in the inner mitochondrial membrane

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28
Q

Describe process of ETS for transport of e- from NADH

A
  1. e- from NADH enter ETC @ complex 1, NAD left
  2. e- transferred to complex 3 by coenzyme Q
  3. Cytochrome C carries e- from complex 3 to complex 4
  4. e- transferred to O2 and 2H+ from mitochodrial matrix is added to form water
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29
Q

Describe Process of ETS for transport of e- from FADH2

A
  1. e- from Krebs cycle are transferred to complex 2 by the intermediate Succinate
  2. In complex 2, e- transferred to FADH2
  3. e- transferred to complex 3 by coenzyme Q
  4. Cytochrome C carries e- from complex 3 to 4
  5. e- transferred to O2 and 2H+ from mitochondrial matrix is added to form water.
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30
Q

Which ET complexes are coupled to the transport of protons across mitochondrial membranes?

A

1, 3, 4. They establish a proton gradient across the mitrochondrial membrane

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31
Q

At each proton transfer complex in the ETS, how many protons are transported per pair of electrons?

A

4

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32
Q

What kind of gradient is formed across the inner membrane of the mitochondria? describe components

A

An Electrochemical gradient is formed by both a pH and electric potential gradient. In the matrix, pH is higher, and there is a (-) charge. In the intermembrane space, pH is lower and there is a (+) charge

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33
Q

ATP synthase

A
  • Complex 5
  • Where ATP is generated as protons move with [_] gradient.
  • 2 components
  • F0
  • F1
34
Q

F0 component of ATP synthase

A

forms a spinning channel through with protons pass

35
Q

F1 component of ATP synthase

A

spins and harvests the free energy of ADP and phosphate group by catalyzing the synthesis of ATP

36
Q

What does Photosynthesis do? What is the overall equation?

A
  1. converts energy of sunlight to a usable chemical energy
  2. source of all metabolic energy in biological systems
  3. 6CO2 + 6H2O—->(light)–> C6H12O6 + 6O2
37
Q

What two stages does Photosynthesis take place in?

A

Light Reactions & Dark Reactions

38
Q

Light Reactions

A

sunlight energy drives synthesis of ATP and NADPH coupled to the oxidation of H2O to O2

39
Q

Dark Reactions

A

The ATP and NADPH from light reactions drive synthesis of carbohydrates from CO2

40
Q

In eukaryotic cells, where do both light & dark reactions occur?

A

Chloroplasts

41
Q

What structure absorbs sunlight

A

Chlorphylls (photosynthetic pigments)

42
Q

What happens as chlorphylls absorb light?

A

Absorption of light excited electrons to a higher energy state; sunlight energy is converted to potential chemical energy

43
Q

How are photosynthetic pigments organized in plants?

A

Within the chloroplast membrane, pigments are organized into photocenters.

44
Q

When sunlight hits a plant, what initially happens in the chloroplast?

A
  1. Photons are absorbed by hundreds of pigment molecules
  2. Energy “jumps” around by resonance energy transfer
  3. energy is transferred to a reaction center chlorophyll
  4. Electrons that are excited are transferred to an acceptor in the ETC
45
Q

Describe process of Light reactions of photosynthesis

A
  1. energy from sunlight is used to split H2O into O2
  2. after splitting, the high energy e- go through a series of carriers (ETC) and used to convert NADP+ to NADPH
  3. Energy from the ETS Rx’s also drive ATP synthesis
46
Q

Thylakoid Memebrane

A
  • an internal membrane system
  • divides chloroplasts into 3 internal compartments
    1. stroma
    2. intermembrane space
    3. thylakoid lumen
47
Q

What structure(s) and how many, within the thylakoid membrane, participate in ___ and synthesis of ______

A

Four protein complexes in the thylakoid membrane function in ETC and synthesis of NADPH

48
Q

Which photosystem absorbs photos in photosynthesis?

A

both 1 and 2

49
Q

How many electron transport chains does photosynthesis and cellular respiration have?

A

PS has 2 electron transport pathways

Cellular respiration has 1

50
Q

What occurs in the first e- transport pathway of PS?

A
  1. H2O is split and the resulting e- enter the transport chain
  2. NADPH is generated
  3. a proton gradient that drives ATP synthesis
51
Q

What is NADPH’s role in photosystem 1 of the 1st ETC?

A

NADPH is generated by photosystem 1, and is required for converting CO2 to carbohydrates

52
Q

What structure generates a proton gradient?

A

Cytochrome bf complex

53
Q

What occurs in PS1, second e- transport pathway?

A
  • Cyclic e- flow: light absorbed by PS1 is used to generate ATP instead of NADPH.
  • High energy e- are transported back to the cyctochrome bf complex, and coupled to establishment of proton gradient
54
Q

Describe thylakoid membrane permeability

A

THylakoid membrane is impermeable to protons, but permeable to other ions like Mg2+ and Cl-

55
Q

How is the total free energy stored across the thylakoid membrane similar to that stored across the inner mitochondrial membrane?

A
  • permeable to specific ions
  • free passage of the ions neutralizes voltage component of proton gradient
  • difference can be more than 3 pH units between stroma and thylakoid lumen
56
Q

For each pair of __ transported, __ protons are transferred at ______ and ____protons at cytochrome bf complex.

A
  1. e-
  2. 2 protons
  3. Photosystem 2
  4. 2-3 protons
57
Q

Since (#) protons are needed for synthesis of _(#)__ ATP, each pair of electrons yields __ to __ ATP.

A
  1. 4 protons
  2. one ATP
  3. one to 1.5 ATP
58
Q

Cyclic electron flow yields ___ ATP per ___ of electrons

A
  1. one ATP

2. per pair of e-

59
Q

In dark Rx’s of photosynthesis, what 2 components drive the synthesis of carbohydrates from ___ and ____

A

ATP and NADPH drive synthesis of carbs from CO2 and H2O

60
Q

How are carbohydrates formed by the Calvin cycle?

A

one molecule of CO2 (1 of 6) at a time is added to the Calvin cycle

61
Q

How many ATP and NADPH does the Calvin Cycle consume for every glucose produced?

A

18 ATP and 12 NADPH

62
Q

How many e- are needed to convert each molecule of NADP+ to NADPH? where are they from?

A

2 e-, from the conversion of H2O to O2

63
Q

What do catabolic pathways involve?

A

oxidation of organic molecules coupled to generation of ATP and reducing power NADH

64
Q

What to Anabolic pathways involve?

A

(aka biosynthetic pathways). Use ATP and reducing power (NADH or NADPH) for production of new organic compounds

65
Q

Gluconeogenesis in animal cells

A
  • glucose synthesis
  • starts with Lactate from anaerobic glycolysis,
  • starts with amino acids from breakdown of proteins OR glycerol from breakdown of lipids
66
Q

Gluconeogenesis in plant cells

A
  • plant cells can synthesize glucose from fatty acids

- important during seed germination since energy stored as fats must be converted to carbs for growth of a new plant

67
Q

Gluconeogenesis process in general

A
  • pyruvate is converted to glucose

- not just the reverse of glycolysis, it requires more energy to drive the pathway in the direction of biosynthesis

68
Q

What is UDP-glucose

A
  • uridine diphosphate
  • a nuclotide sugar used as an intermediate to join two sugar molecules.
  • activated intermediate that donates its glucose to a growing polysaccharadie chain
69
Q

How is UDP-glucose formed?

A

-Formed after glucose is phosphorylated bc then it is able to react with UTP

70
Q

Nitrogen Fixation process

A
  • N2 is reduced to NH3.
  • requires ATP
  • how bacteria use atmospheric Nitrogen
71
Q

What form of nitrogen can all organisms incorporate into organic compounds?

A

NH3

72
Q

What form of Nitrogen can bacteria, fungi, and plants use?

A
  • NO3-, nitrate
  • common constituent of soil
  • must be reduced to NH3
73
Q

How is NH3 incorporated in organisms?

A
  • during synthesis of AA’s glutamate and glutamine
  • the amino acids donate amino groups to other AA’s (these are derived from intermediates in glycolysis and the citric acid cycle)
74
Q

Essential Amino Acids

A

Must be obtained from dietary sources

75
Q

Nonessential amino acids

A

can by synthesized by human cells

76
Q

transfer RNA

A

(tRNA)

  • amino acids are attached to tRNA
  • used during transcription
77
Q

aminoacyl-tRNA

A
  • complex of tRNA and amino acid
  • align based on the mRNA template
  • amino acids are dropped and added to peptide chain
  • coupled to hydrolysis of ATP and GTP
78
Q

Where can nucleotides come from?

A
  • dietary sources
  • nuclic acid breakdown
  • synthesized from carbohydrates and amino acids
79
Q

Process of Nucleotide synthesization

A
  • starts with ribose-5-phosphate.

- different pathways lead to synthesis of purine and pyrimidine ribonucleotides

80
Q

pyrimidine nucleotides

A

UMP, CMP

-from Aspartate

81
Q

purine nucleotides

A

AMP, GMP

-from Aspartate, Glycine, Glutamine

Molecular Cell Biology (16 decks)

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