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Biology 1002 > Cycle 3 > Flashcards

Cycle 3 Flashcards

(43 cards)

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1
Q
  1. What are cells described as in terms of entropy?
A

Cells are islands of low entropy.

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2
Q
  1. Why are living systems thermodynamically open?
A

They bring in thermal energy and matter from their surroundings.

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2
Q
  1. What is required to make proteins from amino acids?
A

Work (free energy) is required to drive amino acids into proteins.

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3
Q
  1. Why do living systems constantly need energy?
A

To build things (e.g., proteins, lipid membranes) and maintain low entropy despite constant breakdown.

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4
Q
  1. What is entropy?
A

Entropy is the measure of disorder or energy spreading.

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5
Q
  1. How does protein entropy compare to amino acid pools?
A

Entropy is lower in proteins because energy is concentrated in one molecule, unlike in amino acid pools.

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6
Q
  1. How do cells maintain low entropy?
A

By constantly bringing in energy and building new molecules to replace broken-down ones.

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7
Q
  1. How do living systems follow the second law of thermodynamics?
A

They release heat and waste products, increasing the entropy of the surroundings.

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8
Q
  1. What is free energy (G)?
A

Free energy is the energy available to do work.

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9
Q
  1. What reactions are spontaneous?
A

Reactions with a negative change in free energy (-ΔG), also called exergonic reactions.

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9
Q
  1. What do ΔG, ΔH, and ΔS represent?
A

ΔG: Free energy
ΔH: Enthalpy (energy content/bond energy)
ΔS: Entropy (disorder)

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9
Q
  1. Write the equation for free energy.
A

ΔG = ΔH - ΔS

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9
Q
  1. Do enzymes change thermodynamics?
A

No, enzymes only change the kinetics (pathway) of a reaction.

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9
Q
  1. What is the role of enzymes in reactions?
A

Enzymes are biological catalysts that speed up reactions by lowering the activation energy (EA).

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9
Q
  1. Why were enzymes essential for life evolution?
A

They speed up reactions, allowing processes to occur quickly at low temperatures.

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9
Q
  1. What is the activation energy (EA)?
A

The energy needed to reach the transition state of a reaction.

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10
Q
  1. How do enzymes lower the activation energy?
A

1) Orienting substrates precisely.
2) Creating charge interactions.
3) Inducing conformational strain.

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11
Q
  1. What is the transition state in a reaction?
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A

The state where bonds are strained and about to break, with the highest free energy.

12
Q
  1. What is induced fit in enzymes?
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A

The enzyme changes shape as the substrate binds to the active site.

13
Q
  1. What happens to proteins in the presence of urea?
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A

Urea disrupts hydrogen bonding, causing proteins to unfold and lose activity.

14
Q
  1. What is native conformation?
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A

The functional shape of a protein, which is the lowest energy state.

15
Q
  1. How do chaperones assist protein folding?
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A

They help proteins fold into their native conformation and prevent misfolding in crowded cellular environments.

16
Q
  1. What dictates a protein’s shape?
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A

Its primary amino acid sequence.

17
Q
  1. Why is protein folding considered an energy-dependent process?
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A

It requires energy to overcome barriers and reach the lowest energy state in a crowded cytosol.

18
Q: Where are most ribosomes located in the cell?
A: In the cytosol, where mRNA is located and cytosolic protein synthesis occurs.
19
Q: What are the two types of proteins that require the secretory pathway?
A: Proteins that are excreted out of the cell or functional on the plasma membrane.
20
Q: What organelles are involved in the secretory pathway?
A: The endoplasmic reticulum (ER), Golgi apparatus, and vesicles.
21
Q: What determines if a protein enters the secretory pathway?
A: The presence of a signal peptide encoded in the gene.
22
Q: How many amino acids are typically in a signal peptide?
A: 15–30 amino acids.
22
Q: What is the role of the signal recognition particle (SRP) in protein targeting?
A: It pauses protein synthesis and directs the ribosome-protein complex to the ER membrane.
23
Q: What happens to the signal peptide after the protein is synthesized in the ER?
A: It is cut off by an enzyme to ensure proper protein folding.
24
Q: What drives simple diffusion?
A: Entropy, as molecules move from high to low concentration to increase disorder.
24
Q: What mutation causes most cases of cystic fibrosis?
A: The ΔF508 mutation, which involves the deletion of an amino acid.
24
Q: What is required for active transport?
A: Energy, typically from ATP, to move molecules against the concentration gradient (low to high).
25
Q: What is the main difference between simple diffusion and facilitated diffusion?
A: Facilitated diffusion uses protein channels to shield molecules from the hydrophobic core of the lipid bilayer.
26
Q: Why does facilitated diffusion exhibit saturation kinetics?
A: Because the number of protein channels is finite, creating a maximum rate of transport.
27
Q: What is the function of CFTR in normal cells?
A: It pumps chloride ions across the plasma membrane, causing water to move via osmosis and keeping mucus lining in the lungs wet.
27
Q: Why does ΔF508 CFTR fail to reach the plasma membrane?
A: It misfolds and is detected by ER quality control (ERQC), leading to degradation.
28
Q: How does ΔF508 CFTR affect individuals with CF?
A: It prevents chloride and water movement, leading to dry mucus, poor gas exchange, and increased susceptibility to bacterial infections.
29
Q: Why is membrane fluidity important?
A: Proper fluidity ensures essential processes like electron transport and prevents leakage or rigidity.
29
Q: Does ΔF508 CFTR still function as a chloride channel?
A: Yes, it can transport chloride ions if only it reaches the plasma membrane.
30
Q: How do organisms maintain membrane fluidity in low temperatures?
A: By introducing kinks into fatty acid tails using desaturases, which create C=C double bonds.
30
Q: How do desaturases regulate membrane fluidity?
A: Their expression increases at lower temperatures and decreases at higher temperatures.

Biology 1002 (11 decks)

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