Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biomolecules CHM040 > Laboratory Exercise 3: Proteins and Denaturing Agents > Flashcards

Laboratory Exercise 3: Proteins and Denaturing Agents Flashcards

1
Q

polymers of amino acids

A

proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

A typical protein may be composed of __ of amino acids

A

hundreds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The R groups of the amino acid may be __

A
  • nonpolar
  • polar
  • positively charged
  • negatively charged
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

structure of proteins that is the sequence of amino acids

A

primary structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

structures of proteins that define the protein’s folded state

A

secondary and tertiary structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

the state in which the protein is most active and functional. What structures and what is it called?

A
  • secondary and tertiary structures
  • native conformation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Proteins are held in their native conformations by a combination of forces:

A
  • hydrogen bonds
  • ionic interactions
  • disulfide bridges
  • hydrophobic interactions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Changing the conformation of a protein either temporarily or permanently by disrupting these forces is called __.

A

denaturation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

results in a loss of protein activity

A

denaturation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Since the native conformation is usually the most __, disrupting the secondary and tertiary structures causes changes in __. It frequently results in the formation of a __ in the solution.

A
  • water-soluble
  • solubility
  • solid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Reagents or conditions that can cause denaturation are called __; these include:

A
  • denaturing agents
    = heat
    = pH changes
    = alcohol
    = heavy metal salts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

describe the figure of hydrogen bonds in the lab sheet

A

N-H — O=C
O=C — H-N

(hydrogen atom that is covalently bonded to more electronegative atom oxygen–donor electron)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe the figure of ionic bonds in the lab sheet

A

NH2(+) (-)OOC

(formed between two ions of opposite charges, typically a metal cation and a non-metal anion, through the transfer of electrons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe the figure of the disulfide bridge in the lab sheet

A

S–S

(covalent bond formed between the sulfur atoms of two cysteine amino acids in a protein)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe the figure of the hydrophobic interaction in the lab sheet

A

–Ar
Ar–

(nonpolar interaction between molecules in aqueous environments, where hydrophobic (water-repelling) portions of molecules tend to aggregate to minimize their contact with water molecules)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

supply kinetic energy to protein molecules, causing their atoms to vibrate more rapidly.

A

heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what forces can heat disrupt?

A

relatively weak forces such as hydrogen bonds and hydrophobic interactions.

18
Q

most common example is observed (heat)

A

cooking an egg

19
Q

also used in sterilization to denature and hence destroy the enzymes in bacteria.

A

heat

20
Q
  • can cause a protein to denature.
  • The R-groups in the amino acid chain are often charged and can form ionic bonds with a group of opposite charge.
  • can change the charges on these positive and negative groups, disrupting ionic bonds.
A

Extremes of pH

21
Q

Some reagents, such as __, can form hydrogen bonds with protein molecules which will disrupt the hydrogen bonding within the molecule.

A
  • ethanol
22
Q

A __ of alcohol can be used as a disinfectant because the alcohol functions to denature the proteins in bacteria. It is used because it will effectively penetrate the __

A
  • 70% solution
  • bacterial cell wall
23
Q

a __ coagulates proteins at the surface of the cell wall, forming a __ that prevents the alcohol from penetrating the cell.

A

-95% solution
- crust

24
Q

examples of salts of metal ions

A
  • mercury(II)
  • lead(II)
  • silver
25
Q

They can form strong bonds with disulfide groups of proteins, disrupting disulfide bridges and salt linkages, and causing the protein to precipitate as insoluble metal-protein salts.

A

salts of metal ions

26
Q

Why are heavy metal salts, like those of mercury(II), lead(II), and silver, used as topical antiseptics?

A
  • disrupt protein structures
  • precipitating proteins out of solution
27
Q

Why are most heavy metal salts toxic when taken internally?

A

Internally, they precipitate proteins in cells, leading to toxicity, as they come into contact with proteins of various cells.

28
Q

How do substances high in protein, such as egg whites and milk, act as antidotes for heavy metal poisoning?

A

Proteins in these substances readily combine with heavy metal ions, forming insoluble solids that can be safely eliminated from the body.

29
Q

What precaution is necessary when dealing with heavy metal poisoning and the use of protein antidotes?

A

The resulting insoluble matter must be promptly removed from the stomach using an emetic to prevent the gastric juices from destroying the protein and releasing the poisonous heavy metal ions.

30
Q

In exercise 3, the effect of several __ on the protein albumin will be studied. __ is a simple globular protein. It is soluble in __ and dilute salt solutions such as __

A
  • denaturing agents
  • Albumin
  • water
  • isotonic saline (0.9% NaCl).
31
Q

Materials in Exercise 3: Proteins and denaturing agents

A
  • 20 mL test tubes (7)
  • pH test strips (4)
  • Test tube holder (1)
    Alcohol lamp-tripod-wire gauze set (1)
  • Stirring rod (2)
  • 250 mL beaker (2)
  • Watch glass (1)
  • Pipet 5 mL (1)
  • Aspirator (1)
  • Wash bottle (1)
  • Test tube brush (1)
32
Q

Chemicals in Exercise 3: Proteins and denaturing agents

A

2 N HCl
2.5 N NaOH
0.2 M AgNO3 (Silver nitrate) (with dropper)
10% trichloroacetic acid
95% Ethanol

33
Q

Procedure in Exercise 3: Proteins and denaturing agents (1-3)```

A
  1. Label seven (7) test tubes as A, B1, B2, C, D, E, and Control.
  2. Prepare a stock albumen solution by adding the white of one (1) egg to 100 mL of distilled water in a beaker. Stir until the albumen is in solution.
  3. Place 5 mL of the albumen solution into each of seven (7) test tubes.
34
Q

Treatment for Control Test Tube

A

Let stand at room temperature. Measure the temperature. Determine the pH with pH paper.

35
Q

Treatment for Test Tube A

A

EFFECT OF HEAT: Heat tube A in a hot water bath for a few minutes.

36
Q

Treatment for Test Tube B

A

The effect of pH changes:
* To tube B1, add 2 mL of 2 N HCl. Record the pH using the pH test strips.
* To tube B2, add 2 mL of 2.5 N NaOH. Record the pH using the pH test strips.

37
Q

Treatment for Test Tube C

A

The effect of metal ions: Add 5-10 drops of AgNO3 (Silver nitrate)

38
Q

Treatment for Test Tube D

A

The effect of an alkaloidal reagent: To tube D, add 1 mL of 10% trichloroacetic acid.

39
Q

Treatment for Test Tube E

A

The effects of ethanol: To tube E, add 1 mL of 95% ethanol.

40
Q
A

Biomolecules CHM040 (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions