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Biochemistry - Lecture > Proteins > Flashcards

Proteins Flashcards

1
Q

is a naturally-occurring, unbranched polymer in which the monomer units are amino acids

A

protein

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2
Q

protein is a naturally-occurring, unbranched polymer in which the monomer units are

A

amino acids

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3
Q

elemental composition of proteins

A

Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O), and Sulfur (S)

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4
Q

The average nitrogen content of proteins is ______ by
mass

A

15.4%

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5
Q

organic compound that contains both an amino (-NH2) and
a carboxyl (-COOH) group attached to same carbon atom

A

Amino acid

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6
Q

amino acis is an organic compound that contains both an _________________ and a ___________________ attached to ________ carbon atom

A

amino (-NH2); carboxyl (-COOH) group; same

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7
Q

(amino acid) The position of carbon atom is

A

Alpha (a)

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8
Q

-NH2 group is attached at

A

alpha (a) carbon atom

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9
Q

-COOH group is attached at

A

alpha (a) carbon atom

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10
Q

R = side chain –vary in

A

size, shape, charge, acidity, functional groups present, hydrogen-bonding ability, and chemical reactivity

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11
Q

__________ amino acids are known

A

more than 700

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12
Q

All amino acids differ from one another by their

A

R-groups

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13
Q

Standard amino acids are divided into four groups
based on the properties of R-groups

A
  1. Non-polar amino acids
  2. Polar amino acids
  3. Polar-neutral
  4. Polar acidic
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14
Q

R-groups are non-polar

A

Non-polar amino acids

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15
Q

Such amino acids are hydrophobic-water fearing (insoluble in water)

A

Non-polar amino acids

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16
Q

___ of the 20 standard amino acids are non polar

A

8

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17
Q

When present in proteins, they are located in the interior of protein where there is no polarity

A

Non-polar amino acids

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18
Q

R-groups are polar

A

Polar amino acids

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19
Q

Three types of polar amino acids

A

Polar neutral; Polar acidic; and Polar basic

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20
Q

contains polar but neutral side chains

A

Polar neutral

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21
Q

Contain carboxyl group as part of the side chains

A

Polar acidic

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22
Q

Contain amino group as part of the side chain

A

Polar basic

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23
Q

A standard amino acid needed for protein synthesis that must be obtained from dietary sources – adequate amounts cannot be synthesized in human body.

A

Essential Amino acid

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24
Q

_________ of the 20 standard amino acids are considered essential

A

9

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25
Q

Non-Polar Amino Acids

A

Glycine, Alanine, Valine, Leucine, Isoleucine, Proline, Phenylalanine, Methionine, Tryptophan

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26
Q

Polar Neutral Amino Acids

A

Serine, Cysteine, Threonine, Asparagine, Glutamine, Tyrosine

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27
Q

Polar Acidic Amino Acids

A

Aspartic acid, Glutamic acid

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28
Q

Polar Basic Amino Acids

A

Histidine, Lysine, Arginine

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29
Q

Essential Amino Acids

A

Arginine*, Methionine, Histidine, Phenylalanine, Isoleucine, Threonine, Leucine ,Tryptophan, Lysine, Valine

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30
Q

In glycine R-group is

A

hydrogen

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31
Q

___ of the 20 standard amino acids contain a chiral center

A

19

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32
Q

Molecules with chiral centers exhibit

A

enantiomerism

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33
Q

leftand right-handed forms

A

enantiomerism

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34
Q

The amino acids found in nature as well as in proteins are

A

L isomers

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35
Q

An ion with + (positive) and – (Negative) charges on the same molecule with a net zero charge

A

Zwitterions

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36
Q

in pure form amino acids are

A

white crystalline solids

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37
Q

give-up a proton to get negative charge

A

Carboxyl groups

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38
Q

accept a proton to become positive

A

Amino groups

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39
Q

Amino acids in solution exist in three different species

A

zwitterions, positive ion, and negative ion

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40
Q

pH at which the concentration of Zwitterion is maximum – net charge is zero

A

Isoelectric point (pI)

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41
Q

At ____________________ - amino acids are not attracted towards an applied electric field because they carry net zero charge.

A

isoelectric point

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42
Q

an analytical method for identifying amino acids by observing their migration as a function of pH under an applied electric field gradient

A

electrophoresis

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43
Q

the only standard amino acid with a sulfhydryl group ( — SH
group)

A

Cysteine

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44
Q

imparts cysteine a chemical property unique among the standard amino acids

A

sulfhydryl group

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45
Q

Cysteine in the presence of mild oxidizing agents dimerizes to form a

A

cystine molecule

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46
Q

Such a chain of covalently-linked amino acids is called a

A

peptide

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47
Q

The covalent bonds between amino acids in a peptide are called

A

peptide bonds (amide)

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48
Q

bond between two amino acids

A

Dipeptide

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49
Q

bond between ~ 10 - 20 amino acids

A

Oligopeptide

50
Q

bond between large number of amino acids

A

Polypeptide

51
Q

Every peptide has an

A

N-terminal end and a C-terminal end

52
Q

Peptides that contain the same amino acids but present in different order are different molecules (constitutional
isomers) with different properties

A

Isomeric Peptides

53
Q

Many relatively small peptides are biochemically active:

A
  • Hormones
    – Neurotransmitters
    – Antioxidants
54
Q

Best-known peptide hormones:

A

oxytocin and vasopressin

55
Q

Produced by the pituitary gland

A

oxytocin and vasopressin

56
Q

are pentapeptide neurotransmitters produced by the brain
and bind receptors within the brain

A

Enkephalins

57
Q

Help reduce pain

A

Enkephalins

58
Q

Best-known enkephalins:

A

Met-enkephalin and Leu-enkephalin

59
Q

a tripeptide – is present is in high levels in most cells

A

Glutathione

60
Q

is an antioxidant and protects cellular contents from oxidizing agents such as peroxides and superoxides

A

Glutathione

61
Q

is a naturally-occurring, unbranched polymer in which the monomer units are amino acids.

A

protein

62
Q

Contains one polypeptide chain

A

Monomeric

63
Q

Contains 2 or polypeptide chains

A

Multimeric

64
Q

A protein in which only amino acid residues are
present

A

Simple proteins

65
Q

A protein that has one or more nonamino acid entities (prosthetic groups) present in its structure

A

Conjugated (complex) proteins

66
Q

contain lipid prosthetic groups

A

Lipoproteins

67
Q

contain carbohydrate groups,

A

Glycoproteins

68
Q

contain a specific metal as prosthetic group

A

Metalloproteins

69
Q

is the amino acid sequence

A

primary structure

70
Q

is repeating geometry

A

secondary structure

71
Q

is overall spatial arrangement

A

tertiary structure

72
Q

is arrangement of several (folded) polypeptides

A

quaternaru structure

73
Q

Four Types of Structures

A

– Primary Structure
– Secondary Structure
– Tertiary Structure
– Quaternary

74
Q

refers to the order in which amino acids are linked together in a protein

A

Primary structure of protein

75
Q

sequenced and determined the primary structure for the first protein - Insulin

A

Frederick Sanger (1953)

76
Q

the first protein

A

insulin

77
Q

Arrangement of atoms of backbone in space.

A

Secondary Structure of Proteins

78
Q

The two most common types of secondary structure:

A

alpha-helix (a-helix) and the beta-pleated sheet (b-pleated sheet)

79
Q

A single protein chain adopts a shape that resembles a coiled spring

A

Alpha
-helix (a
-helix)

80
Q
  • Completely extended amino acid chains
  • H-bonding between two different chains – inter and/or
    intramolecular
  • Side chains below or above the axis
A

Beta-Pleated Sheets

81
Q

The overall three-dimensional shape of a protein

A

Tertiary Structure of Proteins

82
Q

Results from the interactions between amino acid side chains (R groups) that are widely separated from each other.

A

Tertiary Structure of Proteins

83
Q

In general 4 types of interactions are observed in Tertiary Structure of Proteins

A

– Disulfide bonding
–Electrostatic interactions
– H-Bonding
– Hydrophobic interactions

84
Q

covalent, strong, between two cysteine groups

A

Disulfide bond

85
Q

Salt Bridge between charged side chains of acidic and basic amino acids

A

Electrostatic interactions

86
Q

refers to the organization among the various polypeptide
chains in a multimeric protein

A

Quaternary Structure of Proteins

87
Q

Highest level of protein organization

A

Quaternary Structure of Proteins

88
Q

Partial or complete disorganization of protein’s

A

tertiary structure

89
Q

Precipitation (denaturation of proteins)

A

Coagulation

90
Q

a concentrated solution of protein albumin - forms a jelly when heated because the albumin is denatured

A

egg white

91
Q

Three types of proteins:

A

fibrous, globular, and membrane

92
Q

protein molecules with elongated shape

A

fibrous

93
Q

– Generally insoluble in water
– Single type of secondary structure

A

fibrous

94
Q

– Tend to have simple, regular, linear structures
– Tend to aggregate together to form macromolecular structures, e.g., hair, nails, etc

A

fibrous

95
Q

protein molecules with peptide chains folded into
spherical or globular shapes

A

Globular proteins

96
Q

– Generally water soluble – hydrophobic amino acid residues are in the protein core
– Function as enzymes and intracellular signaling molecules

A

Globular proteins

97
Q

associated with cell membranes

A

Membrane proteins

98
Q

– Insoluble in water – hydrophobic amino acid residues on the surface
– Help in transport of molecules across the membrane

A

Membrane proteins

99
Q
  • Provide protective coating for organs
  • Major protein constituent of hair, feather, nails, horns
    and turtle shells
A

Alpha-Keratin

100
Q
  • Most abundant proteins in humans (30% of total body
    protein)
  • Major structural material in tendons, ligaments, blood
    vessels, and skin
  • Organic component of bones and teeth
A

Collagen

101
Q

Rich in proline (up to 20%) – important to maintain
structure

A

Collagen

102
Q

– An oxygen storage molecule in muscles.
– Monomer - single peptide chain with one heme unit
– Binds one O2 molecule
– Has a higher affinity for oxygen than hemoglobin.
– Oxygen stored in myoglobin molecules serves as a
reserve oxygen source for working muscles

A

myoglobin

103
Q
  • An oxygen carrier molecule in blood
  • Transports oxygen from lungs to tissues
  • Tetramer (four polypeptide chains) - each subunit has a
    heme group
  • Can transport up to 4 oxygen molecules at time
  • Iron atom in heme interacts with oxygen
A

Hemoglobin

104
Q

Enzymes are best known for their catalytic role

A

Catalytic proteins

105
Q

Immunoglobulins or antibodies are central to
functioning of the body’s immune system

A

Defense proteins

106
Q

Bind small biomolecules, e.g., oxygen and other
ligands, and transport them to other locations in the body and
release them on demand.

A

transport proteins

107
Q

ransmit signals to coordinate biochemical
processes between different cells, tissues, and organs

A

Messenger proteins

108
Q

regulate carbohydrate metabolism

A

Insulin and glucagon

109
Q

regulate body growth

A

Human growth hormone

110
Q

Necessary for all forms of movement.

A

Contractile proteins

111
Q

Muscles contain filament-like

A

Contractile proteins

112
Q

Confer stiffness and rigidity

A

Structural proteins

113
Q

Span a cell membrane and help control
the movement of small molecules and ions

A

Transmembrane proteins

114
Q

Bind (and store) small molecules.

A

Storage proteins

115
Q

Often found “embedded” in the exterior surface
of cell membranes - act as sites for receptor molecules

A

Regulatory proteins

116
Q

Particularly important in the early stages of life -
from embryo to infant

A

Nutrient proteins

117
Q

Glycoproteins produced as a protective response to the
invasion of microorganisms or foreign molecules -
antibodies against antigens.

A

Immunoglobulins

118
Q

a conjugated protein that contains lipids in addition to
amino acids

A

Lipoprotein

119
Q

Transport dietary triacylglycerols from intestine
to liver and to adipose tissue.

A

Chylomicrons

120
Q

Transport triacylglycerols
synthesized in the liver to adipose tissue

A

Very-low-density lipoproteins (VLDL)

121
Q

Transport cholesterol
synthesized in the liver to cells throughout the body

A

Low-density lipoproteins (LDL)

122
Q

Collect excess cholesterol from
body tissues and transport it back to the liver for degradation to
bile acids.

A

High-density lipoproteins (HDL)

Biochemistry - Lecture (4 decks)

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