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CHEMISTRY 60 > CHAPTER SIXTEEN: AMINO ACIDS, PROTEINS AND ENZYMES > Flashcards

CHAPTER SIXTEEN: AMINO ACIDS, PROTEINS AND ENZYMES Flashcards

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1
Q

All proteins in humans are POLYMERS made up from ____ different amino acids.

A

20

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2
Q

See chart mom made for the classes of proteins, functions and examples

A

fill out the chart

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3
Q

What are AMINO ACIDS?
How many are there?
Every AMINO ACID consists of ____

A

molecular building blocks

20

a central carbon atom called the alpha-carbon bonded to 2 functional groups (and amino group (-NH2) and a carboxylic acid group (-COOH). The alpha-carbon is also bonded to a hydrogen atom and an R group.

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4
Q

What differs in each amino acid and provides unique characteristics to each type?

A

R group

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5
Q

What is a ZWITTERION?

A

An ionized amino acid which has both a positive and a negative charge…it is a dipolar ion.

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6
Q

Amino acids have ____ melting points and:

  • are/are not soluble in water
  • are/are not soluble in organic solvents
A

high

are soluble in water; are not soluble in organic solvents

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7
Q

All the alpha-amino acids except for _____ are chiral because the alpha-carbon is attached to four different atoms

A

GLYCINE

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8
Q

Describe NONPOLAR AMINO ACIDS

A

have hydrogen, alkyl or aromatic R groups, which makes them HYDROPHOBIC (water fearing)

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9
Q

Describe POLAR AMINO ACIDS

A

have R group that interact with water, which makes them HYDROPHYLIC (water loving).

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10
Q

Describe the POLAR NEUTRAL amino acids

A

contain hydroxyl (-OH), thiol (-SH) or amide (CONH2) groups.

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11
Q

What does the R group of a polar acidic amino acid contain?

A

a carboxylate group (-COO-)

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12
Q

What does the R group of a polar BASIC amino acid contain?

A

an amino group which ionizes to give an ammonium ion.

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13
Q

What is the ISOELECTRIC POINT (pI)?

A

A zwitterion forms only at a certain pH

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14
Q

An amino acid can exist as a positive ion if a solution is more ________ (has a lower pH) than its pI or as a negative ion if a solution is more ______ (has a higher phH) than its pI.

A

acidic, basic

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15
Q

The pI values for non polar and polar neutral amino acids are from pH ___ to ___.

A

5.1-6.3

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16
Q

The pI values of the polar SCIDIC amino acids (aspartic advice, glutamic acid) are about pH ___.

At this pH, the carboxylic acid group in the R groups of their zwitterion ______(is/is not) ionized.

A

3

is not

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17
Q

The pI values of basic amino acids are typically ____ than physiological pH value, ranging from pH ____ to _____.

A

higher

7.6-10.8

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18
Q

What is a PEPTIDE bond?

A

an amide bond that forms when the -COO- of one amino acid reacts with the -NH3+ of the next amino acid.

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19
Q

What is a:

  • PEPTIDE
  • DIPEPTIDE
  • TRIPEPTIDE
  • TETRAPEPTIDE
  • PENTAPEPTIDE
  • POLYPEPTIDE
A

A peptide is formed by the linking of 2 or more amino acids by peptide bonds.

Dipeptide= 2 amino acids
Tripeptide= 3
Tetrapeptide= 4
Pentapeptide= 5
Polypeptide= long chains
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20
Q

After you put two amino acids together:

  • Where is the N terminal amino acid and what makes an amino acid N terminal?
  • Where is the C terminal amino acid and what makes an amino acid C terminal??
A

On the left (NH3+)

On the right (COO-)

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21
Q

With the exception of the C terminal amino acid, the names of all the other amino acids in a peptide end with ____

A

yl

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22
Q

What is a PROTEIN?

A

More than 50 amino acids in a chain, the polypeptide is usually called a protein. Every protein has a unique sequence of amino acids that determines its biological function.

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23
Q

The PRIMARY STRUCTURE of a protein is the ____________

A

the particular sequence of amino acids held together by peptide bonds.

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24
Q

What is the SECONDARY STRUCTURE of a protein?

What are the 3 most common types of secondary structures?

A

Describes the type of structure that forms when amino acids form hydrogen bonds within a polypeptide or between polypeptides.

3 most common secondary structures:

  • alpha helix
  • beta-pleated sheet
  • triple helix
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25
Q

Describe an ALPHA HELIX

A

hydrogen bonds form between the oxygen of the C=O groups and the hydrogen of N-H of the amide bonds in the next turn of the ALPHA HELIX.

It has the helical shape of a spiral staircase because there are many hydrogen bonds along the polypeptide. The R groups of the different alpha-amino acids extend to the outside of the helix.

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26
Q

Describe the BETA-PLEATED SHEET

A

hydrogen bonds form between the oxygen atoms in the carbonyl groups of one polypeptide chain and the hydrogen atoms in the N-H groups of the amide bonds in adjacent polypeptide chains.

Several polypeptide chains are held together side by side like folded or pleated sheets.

Silk fibers.

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27
Q

What is the most abundant protein in the body?

Describe the TRIPLE HELIX, which is the structure of this protein.

These fibers are weakened if the diet is deficient in _________

A

COLLAGEN

It is the result of 3 alpha helical polypeptides woven together like a braid.

Collagen has a high content of glycine, proline, alanine and smaller amounts of hydroxyproline and hydroxylsine. The hydroxy forms of proline and lysine contain
-OH groups that form additional hydrogen bonds across the peptide chains to give strength to the collagen triple helix.

Collagen fibers weakened if diet deficient in Vitamin C.

28
Q

What is the TERTIARY STRUCTURE of a protein?

A

involves attractions and repulsions between the R groups of the amino acids in the polypeptide chain.

As interactions occur between different parts of the peptide chain, segments of the chain twist and bend until the protein acquires a specific 3-dimensional shape.

The structure is stabilized by interactions between the R groups of the amino acids in one region of the chain and those in other regions.

29
Q

What are the 5 types of attractions that occur in the tertiary structures of proteins?

A
  1. hydrophobic interactions
  2. hydrophilic interactions
  3. salt bridges
  4. hydrogen bonds
  5. disulfide bonds
30
Q

What are HYDROPHOBIC interactions?

A

interactions between 2 non polar R groups. Within a protein, the amino acids with non polar R groups move away from the aqueous environment to form a hydrophobic center at THE INTERIOR of the protein molecule.

31
Q

What are HYDROPHILIC interactions?

A

attractions between the external aqueous environment and the R groups of polar amino acids moving the polar amino acids toward the OUTER SURFACE of globular proteins where they form hydrogen bonds with water.

32
Q

What are SALT BRIDGES?

A

ionic bonds between ionized R groups of basic and acidic amino acids.

Example: the ionized R group of arginine, which has a positive charge, can form a salt bridge (ionic bond) with the R group in aspartic acid, which has a negative charge.

33
Q

Describe HYDROGEN BONDS as a type of attraction in a protein

A

form between H of a polar R group and the O or N of another amino acid.

For ex: hydrogen bond can form between
-OH groups of two series or between the -OH of serine and the -NH2 in the R group of glutamine.

34
Q

Describe DISULFIDE BONDS as a type of attraction in a protein

A

-S-S- Covalent bonds that form between the -SH groups of cysteines in a polypeptide chain.

35
Q

What are GLOBULAR PROTEINS and what is their function?

A

they have compact, spherical shapes because actions of the polypeptide chain fold over on top of each other due to the various interactions between R groups.

They carry out of the work of the cells: functions such a synthesis, transport, and metabolism.

Example: MYOGLOBIN on page 573

36
Q

What are FIBROUS PROTEINS and what is their function?

Describe the two types

A

They consist of long, thin, fiber-like shapes. Involved in the structure of cells and tissues.

2 types:

  • alpha-keratins: hair, wool, skin and nails; coil together like a braid to form a fibril
  • beta-keratins: feathers, scales. Large amounts of beta-pleated sheet structure
37
Q

What is a QUATERNARY STRUCTURE?

How are the subunits held together?

A

when a biologically active protein consists of two or more polypeptide chains or SUBUNITS, the structural level is a QUATERNARY STRUCTURE.

Example: hemoglobin consists of 4 polypeptide chains or subunits. (alpha2beta2)

Held together by the same interactions that stabilize tertiary structures.

38
Q

What are the similar biological functions of HEMOGLOBIN and MYOGLOBIN?

A

Both carry oxygen.

Hemoglobin- in the blood
Myoglobin- in muscle

39
Q

Which of the following are present in the primary, secondary, tertiary and quaternary structures of proteins:

  • peptide bonds
  • hydrogen bonds between adjacent peptides
  • hydrogen bonds within a single peptide
  • hydrophobic interactions
  • association of 4 polypeptide chains
A
  • peptide: all levels of protein structures
  • hydrogen/adjacent: secondary structures
  • hydrogen/single peptide: secondary and tertiary
  • hydrophobic: tertiary and quaternary
  • 4: quaternary
40
Q

What is the DENATURATION of a protein?

A

occurs when there is a change that disrupts the interactions between R groups that stabilize the secondary, tertiary or quaternary structure. (increased temp, change in pH, adding certain organic compounds, mechanical agitation, etc,)

NOTE: the covalent amide bonds of the primary structure are not affected

41
Q

What are ENZYMES?

They ______ (lower or raise) the activation energy for a chemical reaction

A

Biological catalysts that increase the reaction rate, but is itself not changed.

Lower

42
Q

What is the normal pH and body temperature (Celcius) in a human being?

A

7.4 and 37 degrees Celcius

43
Q

The names of ENZYMES describe the _____ or the ______ that is catalyzed.

The actual names of enzymes are derived by replacing the end of the name of the reaction or reacting compound with the suffix ___.

A

the compound or the reaction

ase

44
Q

Nearly all enzymes are ____ proteins.

Each has a unique 3-dimensional shape that recognizes and binds a small group of reacting molecules, which are called _____.

A

GLOBULAR

SUBSTRATES

45
Q

What is the ACTIVE SITE?

A

Within an enzyme’s large tertiary structure is this region, where the enzyme binds one or more substrates and catalysis the reaction.

Within the active site, the R groups of amino acids interact with the functional groups of the substrate to form hydrogen bonds, salt bridges, or hydrophobic interactions.

The active sit of a particular enzyme first the shape of only a few types of substrates.

46
Q

What is an ENZYME-SUBSTRATE (ES) COMPLEX and what does it do?

A

The proper alignment of a substrate within the active site forms an ES COMPLEX.

This provides an alternative pathway for the reaction that has a lower activation energy.

Within the active site, the amino acid R groups take part in catalyzing the chemical reaction. As soon as the catalyzed reaction is complete, the products are released from the enzyme so it can bind to another substrate molecule.

47
Q

What is the LOCK-and-KEY MODEL theory of enzyme action?

A

an early theory

describes the active site as having a rigid, non flexible shape.

48
Q

What is the INDUCED-FIT MODEL theory of enzyme action?

A

certain enzymes have a broader range of activity than the lock-and-key model allows.

The active site adjusts to fit the shape of the substrate more closely. At the same time, the substrate adjusts its shape to better adapt to the geometry of the active site.

49
Q

What is an ISOENZYME?

A

slightly different forms of an enzyme that catalyze the same reaction in different organs and tissues of the body.

50
Q

What does the ACTIVITY of an enzyme describe?

What affects this activity?

A

it describes how fast an enzyme catalyzes the reaction that converts a substrate to product.

This activity is strongly affected by reaction conditions, which include temperature, pH, concentration of the substrate, concentration of enzyme, and the presence of inhibitors.

51
Q

At LOW TEMPERATURES, most enzymes show _______ activity because _______.

At HIGHER TEMPERATURES, enzyme activity _________.

Enzymes at most active at the OPTIMUM TEMPERATURE, which for most enzymes is _____.

A

little activity; there is not a sufficient of energy for the reaction to take place.

increases

37 degreesC, or body temperature

52
Q

What are THERMOPHILES?

A

Certain organisms that live in environments where temperatures range from 50-80 degreesC. They must have enzymes with tertiary structures that are not destroyed at these temps.

53
Q

What is the OPTIMUM pH for most enzymes?

A

7.4

It does vary depending on where it is.

chart on page 585

54
Q

As long as the substrate concentration is greater than the enzyme concentration, there is a ________ relationship between the enzyme concentration and enzyme activity.

A

direct

55
Q

How do the following affect the activity of an enzyme?

  • decreasing the pH
  • increasing the temperature
  • increasing the substrate concentration at constant temperature and pH
A
  • decreasing the pH= a more acidic environment- disrupts the hydrogen bonds and salt bridges
  • increasing the temperature= the tertiary structure breaks down (denaturation), the shape of the active site deteriorates, and enzyme activity is lost.
  • increases the rate of reaction until all the enzyme has combined with substrate. Then the reaction rate of an exam continues at a constant rate.
56
Q

What are INHIBITORS?

How to they act?

A

many kind of molecules called INHIBITORS cause enzymes to lost catalytic activity.

They act differently, but all prevent the active site from binding with a substrate.

57
Q

What is a COMPETITIVE INHIBITOR?

A

has a similar structure- bonds to the enzyme, competes for the active site. If it occupies the active site, the substrate cannot bind to the enzyme and no reaction takes place.

58
Q

What is a NONCOMPETITIVE INHIBITOR?

A

does not resemble the substrate and does not compete for the active site. It binds to a site on the enzyme that is not the active site. This distorts the shape of the enzyme and now the substrate cannot fit properly. No catalysis can take place.

59
Q

What is IRREVERSIBLE INHIBITION?

usually forms a ________ bond with an amino acid side group within the active site.

A

a molecule causes and enzyme to lose all enzymatic activity. Most are toxic substances that destroy enzymes.

usually forms a covalent bond with an amino acid side group within the active site.

60
Q

What are SIMPLE ENZYMES?

A

consist only of proteins

61
Q

What is a COFACTOR?

A

many enzymes require small molecules or metal ions called COFACTORS to catalyze reactions properly.

62
Q

What is a COENZYME?

A

when the cofactor is a small organic molecule, it is known as a COENZYME.

63
Q

If an enzyme requires a cofactor, neither the protein structure nor the cofactor alone has ________.

A

catalytic activity

64
Q

Many enzymes must contain a metal ion to carry out their catalytic activity. The metal ions are bonded to one or more of the _________________.

A

amino acid groups.

65
Q

What are VITAMINS?

A

organic molecules that are essential for normal health and growth. They are required in trace amounts and must the obtained from the diet because they are not synthesized in the body.

66
Q

What are the two groups of vitamins when classifying by solubility?

Describe each one

A
  1. Water-soluble: have polar groups such as -OH and -COOH. Most are not stored in the body and excess amounts are eliminated in the urine. Must be in the foods of our daily diets.
  2. Fat-soluble: non-polar compounds that are soluble in the lipid (fat) components of the body. Vitamins A, D, E and K are not involved as coenzymes. Sorted in the body and not eliminated- can take too much, which would be toxic.

CHEMISTRY 60 (18 decks)

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