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Energética, enzymes and proteins Flashcards

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1
Q

What is Gibbs free energy used to describe in biological systems?

A

The amount of energy available to do work in a chemical reaction.

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2
Q

What does a negative ΔG (ΔG < 0) indicate about a reaction?

A

It is exergonic and releases energy.

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3
Q

What does a positive ΔG (ΔG > 0) indicate about a reaction?

A

It is endergonic and requires energy input.

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4
Q

Why is ATP considered the ‘energy currency’ of the cell?

A

Because it stores and transfers energy for cellular processes.

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5
Q

What is the standard free energy change for ATP hydrolysis to ADP?

A

-30.5 kJ/mol.

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6
Q

Name three types of biological work that require ATP.

A

Chemical work, movement, and active transport.

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7
Q

What is substrate-level phosphorylation?

A

A process where a phosphate group is transferred directly to ADP to form ATP.

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8
Q

What is oxidative phosphorylation?

A

ATP synthesis using a proton gradient and ATP synthase.

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9
Q

Which organelles are involved in ATP production via oxidative phosphorylation?

A

Mitochondria and chloroplasts.

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10
Q

How does the ATP synthase generate ATP?

A

By using the energy of the proton gradient to drive conformational changes in the catalytic subunits.

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11
Q

What role does the γ subunit play in ATP synthase?

A

Its rotation changes the conformation of the β subunits, driving ATP synthesis.

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12
Q

What is the function of the ADP/ATP exchanger in mitochondria?

A

To export ATP and import ADP, maintaining low matrix [ATP].

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13
Q

What is the function of the Pi/H+ co-transporter?

A

It imports inorganic phosphate (Pi) into the mitochondrial matrix.

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14
Q

How much ATP does a human recycle daily?

A

50-75 kg, more than 500 times per day.

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15
Q

What are other energy-rich phosphate compounds involved in substrate-level phosphorylation?

A

PEP, BPG, and creatine phosphate.

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16
Q

What is the main purpose of cellular respiration?

A

To transform redox energy from nutrients into ATP via the electron transport chain and chemiosmosis.

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17
Q

What role does NADH play in cellular respiration?

A

NADH acts as an “electron currency,” carrying high-energy electrons to the ETC.

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18
Q

What molecule does FADH₂ donate electrons to?

A

Complex II of the ETC.

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19
Q

What is redox potential?

A

A measure of a molecule’s tendency to gain or lose electrons.

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20
Q

What does a negative redox potential indicate?

A

The molecule has a high tendency to donate electrons (high free energy).

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21
Q

What does a positive redox potential indicate?

A

The molecule has a high tendency to accept electrons (low free energy).

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22
Q

What equation is used to calculate the free energy change (ΔG°) in redox reactions?

A

ΔG° = -nFΔE’₀

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23
Q

How much energy is released by transferring electrons from NADH to O₂?

A

Approximately -52.4 kcal/mol.

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24
Q

How many ATP molecules can be generated from one glucose molecule?

A

Approximately 36 to 38 ATP.

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25
Which ETC complex does not pump protons?
Complex II.
26
What are the prosthetic groups in Complex I?
FMN and Fe-S clusters.
27
Which ETC component contains heme a and copper centers?
Complex IV (Cytochrome c oxidase).
28
What property of ETC components allows them to be studied with light?
Their spectral (color) properties change depending on redox state.
29
How do enzymes in the ETC prevent the release of dangerous radicals?
By sequestering electron intermediates like semiquinones deep inside their structures.
30
What is the function of the Q cycle in Complex III?
To transfer 2 electrons from QH₂ to cytochrome c, safely managing the radical intermediate Q⁻*.
31
What molecule transfers electrons one at a time and is water-soluble?
Cytochrome c.
32
Where in the mitochondrion does the ETC occur?
The inner mitochondrial membrane.
33
What drives ATP synthase to make ATP?
The proton gradient (chemiosmotic gradient) generated by the ETC.
34
What is electron tunneling?
A mechanism allowing electrons to jump between redox centers over short distances inside enzymes.
35
What is the function of ubiquinone (Q) in the ETC?
It transports electrons between Complex I/II and Complex III and is lipid-soluble.
36
Name four types of photosynthetic organisms.
Purple bacteria, cyanobacteria, algae, higher plants (including mosses and ferns).
37
How much free energy is stored per year by photosynthesis (excluding oceans)?
>10^7 kcal
38
How much carbon is assimilated into organic matter each year (excluding oceans)?
>10^10 tons
39
What is the annual total grain yield worldwide?
Approximately 2 x 10^9 tons
40
What percentage of land is used by agriculture in the tropics and temperate regions?
10% (tropics), 20% (temperate)
41
How much does grain production need to increase by 2050?
From 2 to 3.5 billion tons/year
42
What is the estimated new cropland required by 2050?
100–200 million hectares
43
How much carbon is lost per hectare due to land conversion?
120 tons C/ha (natural to crop), 60 tons C/ha (pasture to crop)
44
What are the two main steps of photosynthesis?
1. Energy capture (ATP, NADPH production), 2. Carbon fixation using ATP/NADPH
45
What structures in chloroplasts are involved in the light reactions?
Thylakoids and stroma
46
What two processes happen to chlorophyll in the antenna complex and reaction centre?
Energy absorption and transfer in antenna; high-energy electron generation in reaction centre
47
What are the core components of a photosystem?
Antenna complex and reaction centre
48
What is the donor of low-energy electrons in Photosystem II?
Water
49
What are the major products of the light reactions?
ATP and NADPH
50
What does the Calvin cycle use to fix carbon dioxide?
ATP and NADPH
51
What are the four levels of protein structure?
Primary, secondary, tertiary, and quaternary.
52
What is the primary structure of a protein?
The sequence of amino acids in the polypeptide chain.
53
What interactions stabilize alpha helices?
Hydrogen bonds between the N-H and C=O groups.
54
How many residues per turn does an alpha helix have?
3.6 residues per turn.
55
What is a beta-sheet?
A protein structure formed by hydrogen bonds between strands, with R-groups alternating above and below.
56
Which amino acids are commonly found in beta turns?
Proline and glycine.
57
What forces contribute to tertiary protein structure?
Hydrogen bonding, ionic bonding, van der Waals forces, hydrophobic interactions, and disulfide bonds.
58
What is a protein domain?
An independently folding unit of a protein that often carries a specific function.
59
What is a motif in protein structure?
A sequence of amino acids that is predictive of a particular function or family.
60
What experiment demonstrated that proteins can refold after denaturation?
Anfinsen's experiment.
61
What is the hydrophobic effect?
The tendency of non-polar groups to aggregate in water to minimize entropy loss.
62
What is the Walker motif?
A conserved motif involved in nucleotide binding, e.g., ATP.
63
What is the function of SH2 domains?
They recognize and bind phosphorylated tyrosines in signaling proteins.
64
What technique provides atomic-level protein structure?
X-ray crystallography.
65
What is BLAST used for in bioinformatics?
Comparing a protein or DNA sequence against a database to find similar sequences.
66
What is the dissociation constant (Kd)?
A measure of the affinity between two binding molecules, defined as [P][L]/[PL].
67
What does a low Kd value indicate?
Tight binding and high affinity.
68
How can protein domains evolve?
Through recombination and shuffling events during evolution.
69
What is homology modeling?
Predicting a protein’s structure based on the structure of a homologous protein.
70
What are the main techniques in proteomics?
Mass spectrometry and chromatography techniques to analyze complex protein mixtures.
71
What is the resting membrane potential of most cells?
-60 mV
72
What equation calculates the equilibrium potential for an ion?
Nernst equation
73
What factors determine the membrane potential?
Ion equilibrium potentials and membrane permeability
74
What is the GHK equation used for?
To calculate membrane potential considering multiple ions and their permeabilities
75
What technique measures ion currents through single channels?
Patch-clamp technique
76
What enables selectivity in potassium channels?
The TVGYG selectivity filter motif
77
What is the Ball-and-Chain model?
Mechanism of channel inactivation where a 'ball' blocks the pore
78
What kind of gating does the acetylcholine receptor use?
Ligand gating
79
What is a P-type ATPase and its example?
An ATP-powered ion pump; e.g., Ca2+ ATPase (SERCA)
80
What enables voltage gating in K+ channels?
Structural movement in the protein sensitive to membrane potential changes
81
What is AMPK?
AMP-activated protein kinase, a cellular energy sensor
82
How does AMP activate AMPK?
1. Promotes phosphorylation, 2. Inhibits dephosphorylation, 3. Allosteric activation
83
What does AMPK regulate?
Many downstream signaling pathways related to energy metabolism
84
What happens in plants during long-term starvation?
Growth is adjusted to starch degradation rate
85
What links the circadian clock to metabolism in plants?
Starch degradation regulated by anticipated night length

Genes Molecules And Cells (3 decks)

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