Lecture 5 - Exam 1 Flashcards

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1
Q

What does X-ray crystallography do?
What was it used in solving?

A

Create crystallized structures with ordered molecule and shoot an X ray beam through this, the X rays will be diffracted. Based off diffraction patterns, can determine what molecule you are looking at.
Used in solving the 3-D protein structure

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2
Q

Who helped solved the 3-D protein structure?

A

John Kendrew & Max Perutz
Used Sperm Whale Myoglobin
*Computer modeling too

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3
Q

Local amino acid sequences which form stable interactions will serve as…?

A

Nucleation points in the folding process.

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4
Q

What is a fundamental role of proteins?

A

To act as enzymes.

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5
Q

What are enzymes?

A

Enzymes are catalysts that increase the rate of all chemical reactions in cells. Without enzymes, most biochemical reactions are so slow that they would not occur.

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6
Q

What are the fundamental properties of enzymes?

A

Increase rate of chemical reactions without themselves being consumed or permanently altered.
Increase reaction rates without altering the chemical equilibrium between reactants and products.

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7
Q

How is equilibrium determined?

A

Equilibrium is determined by the final energy states of substrate and product.
The substrate must first be converted to a higher energy state, the transition state.

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8
Q

Energy required to reach the transition state =

A

activation energy.
Enzymes reduce the activation energy.

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9
Q

Enzymes must bind their ______ to form _________.

A

substrates ; enzyme-substrate complex (ES)

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10
Q

Where does the substrate bind?
The substrate is converted to ______ while bound.

A

Active site
The substrate is converted to product while bound to the active site, then released.

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11
Q

The enzymes brings the substrates together in proper orientation to _____.

A

Favor the transition state.

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12
Q

Enzymes also accelerate reactions by _________.

A

Altering the conformation of substrates to approach the transition state.
The stress produced by distortion of the substrate further lowers the transition state by weakening critical bonds in the protein substrate.

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13
Q

What is the lock-and-key model?

A

The substrate fits precisely into the active site.

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14
Q

What is induced fit?

A

Conformation of both enzyme and substrate is modified.

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15
Q

Who discovered Chaperons?

A

F. Ritossa when a lab worker accidentally boosted the incubation temperature of Drosophila.
When examining the chromosomes, Ritossa found a “puffing pattern” that indicated elevated gene transcription of an unknown protein.

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16
Q

Defects in protein folding are responsible for?

A

Protein misfolding diseases.

17
Q

Cystic fibrosis is caused by…?

A

A mutation that results in a one amino acid deletion that leads to improper folding of protein CFTR. CFTR transports Cl- ions across epithelial cell membranes.
When CFTR is not functional, Cl- ions get trapped in cells and the cell surface doesn’t get hydrated. Secretions which are thin, become thick… coughing up mucus.

18
Q

Alzheimer’s disease, Parkinson’s disease, and type 2 diabetes are associated with…?

A

Aggregation of misfolded proteins.
The misfolded proteins form fibrous aggregates called amyloids, characterized by B-sheets structures.

19
Q

What does Prion stand for? What are they?

A

Proteinaceous infectious particle
Prions are misfolded proteins that can self-replicate.
Infection by prions is based on amyloid formation of the protein PrP.

20
Q

[Prions] In mammalian cells, the normal alpha-helical form is…?

A

PrPC

21
Q

[Prions] In the infectious form, PrP forms a…?

A

Misfolded amyloid structure, PrPSc.

22
Q

PrPSc can replicate by inducing autocatalytic amyloid formation of endogenous PrPC - a…?

A

Novel form of propagation that does not require any nucleic acid.

23
Q

What do cell membranes do?

A

Define the boundary of the cell and cell organelles.
It is a selective barrier to the passage of molecules.

24
Q

Why are steroid molecules able to pass through the cell membrane?

A

Due to their extreme hydrophobic nature.

25
Q

Phospholipids spontaneously form _____ when…?

A

Bilayers ; in aqueous solutions.

26
Q

Lipids make up ____% of the mass of the membrane - depending on the membrane.

A

50
Ex: plasma membranes 50% protein 50% lipid, whereas mitochondrial membranes are 75% protein.

27
Q

Double bonds between carbons affect…?

A

Physical properties of membranes

28
Q

Unsaturated fatty acids chains have double bonds that result in…? What does this do?

A

Kinks
This reduces packing and increases membrane fluidity.

29
Q

Membrane fluidity is determined by…?

A

Temperature and lipid composition.
Think bacon fat versus olive oil at room temperature.

30
Q

What is the structure of a cholesterol?

A

A sterol ring structure and polar OH head.

31
Q

What does cholesterol help to determine because of its ring structure?

A

Membrane fluidity

32
Q

Interactions between the hydrocarbon rings of a cholesterol and fatty acid tails makes the membrane more…?

A

rigid

33
Q

Cholesterol also interferes with interaction between fatty acids, maintaining membrane fluidity at…?

A

lower temperatures

34
Q

What is the orientation of phospholipids in the cell membrane?
Phospholipids with a negative charge are located where?

A

Asymmetric
Phospholipids with negative charges are located on the cytosolic face.