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Biochemistry > Module 02: Protein Structure and Function > Flashcards

Module 02: Protein Structure and Function Flashcards

1
Q

How many percentage do proteins make up a singular cell?

A

15%

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2
Q

What are the different functions of proteins?

A

(1) Enzymes (Catalytic)
(2) Structural
(3) Transport and Storage
(4) Signaling molecules and Receptors
(5) Defense

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3
Q

These links the amino acids of proteins

A

peptide bonds

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4
Q

This is the repeating sequence of the N-Ca-C-N-Ca-C-N-Ca-C… in the peptide bond.

A

Polypeptide backbone

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5
Q

The protein shape is determined by what?

A

The sequence of amino acids

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6
Q

The final shape is called the _____________and has the lowest free energy possible (stable)

A

Conformation

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7
Q

This is the process of unfolding the protein, manifested by coagulation.

A

Denaturation

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8
Q

Which agent can cause denaturation?

A

heat, pH or chemical compounds like alcohol, urea, acids and bases

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9
Q

These protein turns like a spiral – fibrous proteins.

A

Alpha helix

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10
Q

This protein folds back on itself as in a ribbon –globular proteins

A

Beta sheets

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11
Q

Where is alpha-helix located?

A

The human hair, nails, and skin

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12
Q

These soluble in water and have compact shape like a ball with irregular surfaces.

A

Globular Proteins

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13
Q

What are some examples of globular proteins?

A

(1) Enzymes
(2) Immunoglobins
(3) Transport molecules like myoglobin and hemoglobin
(4) Hormones

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14
Q

These are insoluble in water and usually span a long distance in the cell. This has a 3-D structure is usually long and rod shaped

A

Fibrous proteins

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15
Q

What function does fibrous proteins have?

A

Structural Function

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16
Q

What are some examples of fibrous proteins?

A

(1) Collagen
(2) Keratin
(3) Silk Fibroin

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17
Q

This is composed of of 2 a-helices

A

Coiled Coil

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18
Q

This is composed of pair of coiled coils

A

Protofilament

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19
Q

This is composed of four coiled protofilaments

A

Microfilament

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20
Q

This type of keratin is the basic structural unit is the alpha helix and is seen in humans.

A

Alpha keratin

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21
Q

Where is the alpha keratin found?

A

wools, hair, skin and nails

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22
Q

What is role of alpha keratin?

A

To provide structural stability

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23
Q

This form of keratin is present in birds and reptiles and is known to be rich in beta sheet structures

A

Beta keratin

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24
Q

Where is b-keratin found?

A

Found in hard tissues like feathers, horns, claws and hooves, beaks and scales

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25
Q

What is the role of b keratin?

A

Provides rigidity, waterproofing and prevention from desiccation

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26
Q

This is the most abundant protein in the human body (25% of total protein weight of human body). Moreover, it is constituted of insoluble fibers that have high tensile strength.

A

Collagen

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27
Q

The collagen alpha chain is described to be ___________________

A

left handed with 3 amino acid residues per turn.

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27
Q

The alpha chain of collagen has repeating sequence of what

A

tripeptide sequence: Gly-X-pro, and Gly-X-4-hyp

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28
Q

The 3 alpha chains wrap around one another in what manner?

A

A right handed twist

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29
Q

In the 3 stranded collagen superhelix within a space filling model, this amino acid is required at the tight junction where the 3 helices meet.

A

Glycine

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30
Q

This is required at the tight junction where the 3 helices meet

A

Collagen triple helix

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31
Q

Where is the collagen located?

A

(1) tendons
(2) cartilage
(3) ligaments
(4) blood vessels
(5) skin and eye cornea
(6) bones and teeth

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32
Q

The 3 chains interact by ___________________(formed during posttranslational modification by hydroxylation).

A

H-bonding between OHpro and OHlys

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33
Q

This is the cofactor of the enzyme hydroxylase required for hydroxylation.

A

ascorbic acid

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34
Q

This pertains to the bleeding of the gums, skin discoloration result from fragile collagen due to vitamin C deficiency

A

Scurvy

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35
Q

This is formed from the lining of long, thin, and rigid collagen molecules.

A

Collagen fibrils

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36
Q

This results to stiffening of the skin and other tissues is due to increase in the number of cross-links

A

Aging (due to more cross links making the skin more rigid)

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37
Q

This syndrome pertains to the abnormal bone formation in babies. Bones easily bend and fracture.

A

Osteogenesis imperfecta or brittle bone syndrome

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38
Q

This is characterized by stretchy skin and loose joints.

A

Ehlers-Danlos syndrome

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39
Q

The Ehlers-Danlos is characterized by what?

A

(1) Hyperelasticity
(2) Hypermobility
(3) Atrophic Scarring
(4) Fragility

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40
Q

These are rubber-like properties with structure of irregular or a random coil. Moreover, it is located in elastic fibers like lungs, walls of large blood vessels and elastic ligaments.

A

Elastin

41
Q

In this, the specific three-dimensional conformation (shape) is changed by breaking some bonds without breaking its primary structure. This may be reversible or irreversible. And it causes a total or partial loss of biological activity

A

Denaturation

42
Q

What are the effects of denaturation?

A

(1) Non-covalent interactions (H-bond, hydrophobic, ionic) are broken
(2) Results into unfolding of polypeptide chain
(3) Loss of H2O solubility
(4) Coagulation (precipitation out of biochemical solution of denatured proteins)

43
Q

The tertiary structure of a globular protein is determined by its ________________.

A

Amino Acid Sequence

44
Q

This is a hemoprotein only found in the cytoplasm of erythrocytes (ery). This transports O2 and CO2 between lungs and various tissues

A

Hemoglobin

45
Q

A hemoglobin tetramer is comprised of

A

2a (141 amino acids) & 2b (146 amino acids)

46
Q

What kind of binding does hemoglobin have?

A

Cooperative Binding of O2

47
Q

What is the normal concentration of hemoglobin in adult males?

A

135 – 175 g/L

48
Q

What is the normal concentration of hemoglobin in adult females?

A

120 – 168 g/L

49
Q

What do you call the 4 peptide subunits constituting the spherical shape of the hemoglobin?

A

Globins

50
Q

What kind of structure does hemoglobin have?

A

Quaternary structure

51
Q

What is the central ion of each globin of a hemoglobin tetramer?

A

1 heme group with a central Fe2+ ion (ferrous ion)

52
Q

A heme is comprised of what?

A

conjugated system of double bonds → red colour
Protoporphyrin ring (4 pyrroles)
1 iron cation (Fe2+)→ bound in the middle of tetrapyrrole skelet by 4 coordination covalent bonds

53
Q

This pertains to the proteins that stores &transports O2 in skeletal and heart muscle. Moreover, it is found in cytosol of skeletal & heart muscles

A

Myoglobin

54
Q

How many amino acyl residue and heme does myoglobin contain respective?

A

153-amino acyl residue and 1 heme

55
Q

How many a helices does myoglobin contain?

A

8 alpha helices from a to h

56
Q

How does myoglobin release O2 during O2 deprivation during exercise?

A

Facilitated diffusion

57
Q

How is a typical globular protein constituted?

A

surface is polar, interior contains nonpolar residues such as Leucine, Valine, Phenylalanine, and Methionine

58
Q

These residues in myoglobin participate in O binding.

A

His E7 (proximal) and His F8 (distal),

59
Q

This is the major form of Hb in adults and in children over 7 months, made up of 2 alpha and 2 beta subunits.

A

HbA1

60
Q

This is a minor form of Hb in adults. It forms only 2 – 3% of
a total Hb. It is made up of two alpha and two delta subunits.

A

HbA2

61
Q

This occurs in fetus and newborn infants, wherein it binds O2 at lower tension than Hb A; thus resulting to a higher affinity to O2. It is composed of 2 alpha and 2 y subunits.

A

HbF

62
Q

In this, the β-globin chain Glu is replaced by Val. Thus, resulting to an abnormal Hb typical for sickle cell anemia

A

HbS

63
Q

This is Hb with O2.

A

Oxyhemoglobin (oxyHb)

64
Q

This is without CO2

A

Deoxyhemoglobin (deoxyHb)

65
Q

This Hb contains Fe3+ instead of Fe2+ in heme groups

A

Methemoglobin (metHb)

66
Q

In this Hb, CO binds to Fe2+ in heme in case of CO poisoning or smoking. CO has 200x higher affinity to Fe2+ than O2.

A

Carbonylhemoglobin (HbCO)

67
Q

In this Hb, CO2 is bound to the N-terminal amino group of the T form of Hb.

A

Carbaminohemoglobin (HbNHCO2-)

68
Q

HbNHCO2- transports CO2 in blood about how many percentage?

A

23%

69
Q

This Hb is formed spontaneously by nonenzymatic reaction with Glc. People with DM have more HbA1c than normal (› 7%).

A

Glycated hemoglobin (HbA1c)

70
Q

This is formed when Glucose enters RBC, glycates є- amino group of lysine residues and the amino terminals of valine of the b-chains

A

HbA1c (Glycated Hemoglobin)

71
Q

HbA1c reflects mean blood glucose concentration over ____________________ weeks

A

6-8 since glycated fraction is proportional to blood glucose concentration

72
Q

This permits Hb to maximize both the quantity of O2 loaded at the PO2 of the lungs and quantity of O2 released at the PO2 of peripheral tissues

A

Cooperative binding

73
Q

Quaternary structure of Hb confers the property of being ____________

A

allosteric

74
Q

Hemoglobin shows positive _______________which is absent in myoglobin

A

Bohr Effect

75
Q

These are disorders caused by production of structurally abnormal Hb or synthesis of abnormal Hb

A

Hemoglobinopathies

76
Q

This is a homozygous recessive disorder. Individuals with this disorder inherited two mutant genes from each parent

A

Sickle-cell Anemia (lifelong hemolytic anemia)

77
Q

This Heterozygous disorder has one normal and one mutant gene. The red blood cells contains both HbS and HbA.

A

Sickle-cell Trait

78
Q

This is a defective biosynthesis of the globin chain. These are genetic defects/hereditary hemolytic anemia and is caused by partial or total absence of 1 or more alpha or beta chains of hemoglobin

A

Thalassemia

79
Q

What are the 3 mutations of Thalassemia?

A

Alpha chain (alpha Thalassemia)
Beta chain (beta Thalassemia)
A sub-unit’s synthesis is reduced

80
Q

What are the clinical implications of Thalassemia?

A

Myoglobinuria- due to trauma or massive crash injury, myoglobin is released from damaged muscle fibers
Urine becomes dark red
Anemias- reduction in
1. numbers of erythrocytes
2. decrease Hb in the blood

81
Q

These are also known as Antibodies and are gamma globulin proteins (glycoproteins) that are found in blood or other body fluids,

A

Immunoglobulin

82
Q

What is the basic structure of an Immunoglobulin ?

A

Its basic structure consists of 4 amino acid chains linked together by disulfide bonds.
-two large heavy chains
-two small light chains

83
Q

What is the function of antibodies?

A

An antibody isa protein component of the immune system that circulates in the blood, recognizes foreign substances like bacteria and viruses, and neutralizes them.

84
Q

These recognize the antigen and produce antibodies that bind with the specific antigen.

A

Blood lymphocyte and plasma cell

85
Q

This results when the blood lymphocyte and plasma cell recognize the antigen and produce antibodies that bind with the specific antigen.

A

agglutination

86
Q

This is the process wherein foreign substances are removed.

A

phagocytosis

87
Q

This form of immunoglobulin is a monomer found in tissue fluids and plasma proteins.

A

Immunoglobulin G

88
Q

Where is the Immunoglobulin G located?

A

placenta (passive immunity).

89
Q

What are the functions of the Immunoglobulin G ?

A

(1) Attacks foreign antigens (bacteria and virus)
(2) Opsonin (substances that enhance phagocytosis)

90
Q

This type of immunoglobulin is a minor circulating Ab and is a monomer.

A

Immunoglobulin D

91
Q

Where is the Immunoglobulin D found?

A

on the surface of B lymphocytes (BCR).

92
Q

What is the function of Immunoglobulin D ?

A

B cell activation

93
Q

This is a Dimer in secretions and a monomer in serum as well as a major secretory Ab

A

Immunoglobulin A

94
Q

Where is the Immunoglobulin A located?

A

found in secretions (saliva, colostrum, serum), nasal
fluid, tears, gastric and intestinal juice, bile, and urine.

95
Q

What is the function of Immunoglobulin A?

A

Inhibits glycolitic metabolism of bacteria.

96
Q

This type of immunoglobulin is found in blood and lymph

A

Immunoglobulin E

97
Q

What are the functions of immunoglobulin e?

A

Binds to mast cells releasing histamine,
Involved in allergic reactions
Attacks allergic -causing antigens
Kills parasites

98
Q

This type of immunoglobulin is a pentamer and the 1st Ab to appear after immunization, binds complement strongly

A

Immunoglobulin M

99
Q

Where is the immunoglobulin m developed?

A

Develops in blood plasma. (fixes complement)

Biochemistry (16 decks)

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