Module 02: Protein Structure and Function Flashcards
How many percentage do proteins make up a singular cell?
15%
What are the different functions of proteins?
(1) Enzymes (Catalytic)
(2) Structural
(3) Transport and Storage
(4) Signaling molecules and Receptors
(5) Defense
These links the amino acids of proteins
peptide bonds
This is the repeating sequence of the N-Ca-C-N-Ca-C-N-Ca-C… in the peptide bond.
Polypeptide backbone
The protein shape is determined by what?
The sequence of amino acids
The final shape is called the _____________and has the lowest free energy possible (stable)
Conformation
This is the process of unfolding the protein, manifested by coagulation.
Denaturation
Which agent can cause denaturation?
heat, pH or chemical compounds like alcohol, urea, acids and bases
These protein turns like a spiral – fibrous proteins.
Alpha helix
This protein folds back on itself as in a ribbon –globular proteins
Beta sheets
Where is alpha-helix located?
The human hair, nails, and skin
These soluble in water and have compact shape like a ball with irregular surfaces.
Globular Proteins
What are some examples of globular proteins?
(1) Enzymes
(2) Immunoglobins
(3) Transport molecules like myoglobin and hemoglobin
(4) Hormones
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
Fibrous proteins
What function does fibrous proteins have?
Structural Function
What are some examples of fibrous proteins?
(1) Collagen
(2) Keratin
(3) Silk Fibroin
This is composed of of 2 a-helices
Coiled Coil
This is composed of pair of coiled coils
Protofilament
This is composed of four coiled protofilaments
Microfilament
This type of keratin is the basic structural unit is the alpha helix and is seen in humans.
Alpha keratin
Where is the alpha keratin found?
wools, hair, skin and nails
What is role of alpha keratin?
To provide structural stability
This form of keratin is present in birds and reptiles and is known to be rich in beta sheet structures
Beta keratin
Where is b-keratin found?
Found in hard tissues like feathers, horns, claws and hooves, beaks and scales
What is the role of b keratin?
Provides rigidity, waterproofing and prevention from desiccation
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.
Collagen
The collagen alpha chain is described to be ___________________
left handed with 3 amino acid residues per turn.
The alpha chain of collagen has repeating sequence of what
tripeptide sequence: Gly-X-pro, and Gly-X-4-hyp
The 3 alpha chains wrap around one another in what manner?
A right handed twist
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.
Glycine
This is required at the tight junction where the 3 helices meet
Collagen triple helix
Where is the collagen located?
(1) tendons
(2) cartilage
(3) ligaments
(4) blood vessels
(5) skin and eye cornea
(6) bones and teeth
The 3 chains interact by ___________________(formed during posttranslational modification by hydroxylation).
H-bonding between OHpro and OHlys
This is the cofactor of the enzyme hydroxylase required for hydroxylation.
ascorbic acid
This pertains to the bleeding of the gums, skin discoloration result from fragile collagen due to vitamin C deficiency
Scurvy
This is formed from the lining of long, thin, and rigid collagen molecules.
Collagen fibrils
This results to stiffening of the skin and other tissues is due to increase in the number of cross-links
Aging (due to more cross links making the skin more rigid)
This syndrome pertains to the abnormal bone formation in babies. Bones easily bend and fracture.
Osteogenesis imperfecta or brittle bone syndrome
This is characterized by stretchy skin and loose joints.
Ehlers-Danlos syndrome
The Ehlers-Danlos is characterized by what?
(1) Hyperelasticity
(2) Hypermobility
(3) Atrophic Scarring
(4) Fragility
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.
Elastin
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
Denaturation
What are the effects of denaturation?
(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)
The tertiary structure of a globular protein is determined by its ________________.
Amino Acid Sequence
This is a hemoprotein only found in the cytoplasm of erythrocytes (ery). This transports O2 and CO2 between lungs and various tissues
Hemoglobin
A hemoglobin tetramer is comprised of
2a (141 amino acids) & 2b (146 amino acids)
What kind of binding does hemoglobin have?
Cooperative Binding of O2
What is the normal concentration of hemoglobin in adult males?
135 – 175 g/L
What is the normal concentration of hemoglobin in adult females?
120 – 168 g/L
What do you call the 4 peptide subunits constituting the spherical shape of the hemoglobin?
Globins
What kind of structure does hemoglobin have?
Quaternary structure
What is the central ion of each globin of a hemoglobin tetramer?
1 heme group with a central Fe2+ ion (ferrous ion)
A heme is comprised of what?
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
This pertains to the proteins that stores &transports O2 in skeletal and heart muscle. Moreover, it is found in cytosol of skeletal & heart muscles
Myoglobin
How many amino acyl residue and heme does myoglobin contain respective?
153-amino acyl residue and 1 heme
How many a helices does myoglobin contain?
8 alpha helices from a to h
How does myoglobin release O2 during O2 deprivation during exercise?
Facilitated diffusion
How is a typical globular protein constituted?
surface is polar, interior contains nonpolar residues such as Leucine, Valine, Phenylalanine, and Methionine
These residues in myoglobin participate in O binding.
His E7 (proximal) and His F8 (distal),
This is the major form of Hb in adults and in children over 7 months, made up of 2 alpha and 2 beta subunits.
HbA1
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.
HbA2
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.
HbF
In this, the β-globin chain Glu is replaced by Val. Thus, resulting to an abnormal Hb typical for sickle cell anemia
HbS
This is Hb with O2.
Oxyhemoglobin (oxyHb)
This is without CO2
Deoxyhemoglobin (deoxyHb)
This Hb contains Fe3+ instead of Fe2+ in heme groups
Methemoglobin (metHb)
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.
Carbonylhemoglobin (HbCO)
In this Hb, CO2 is bound to the N-terminal amino group of the T form of Hb.
Carbaminohemoglobin (HbNHCO2-)
HbNHCO2- transports CO2 in blood about how many percentage?
23%
This Hb is formed spontaneously by nonenzymatic reaction with Glc. People with DM have more HbA1c than normal (› 7%).
Glycated hemoglobin (HbA1c)
This is formed when Glucose enters RBC, glycates є- amino group of lysine residues and the amino terminals of valine of the b-chains
HbA1c (Glycated Hemoglobin)
HbA1c reflects mean blood glucose concentration over ____________________ weeks
6-8 since glycated fraction is proportional to blood glucose concentration
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
Cooperative binding
Quaternary structure of Hb confers the property of being ____________
allosteric
Hemoglobin shows positive _______________which is absent in myoglobin
Bohr Effect
These are disorders caused by production of structurally abnormal Hb or synthesis of abnormal Hb
Hemoglobinopathies
This is a homozygous recessive disorder. Individuals with this disorder inherited two mutant genes from each parent
Sickle-cell Anemia (lifelong hemolytic anemia)
This Heterozygous disorder has one normal and one mutant gene. The red blood cells contains both HbS and HbA.
Sickle-cell Trait
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
Thalassemia
What are the 3 mutations of Thalassemia?
Alpha chain (alpha Thalassemia)
Beta chain (beta Thalassemia)
A sub-unit’s synthesis is reduced
What are the clinical implications of Thalassemia?
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
These are also known as Antibodies and are gamma globulin proteins (glycoproteins) that are found in blood or other body fluids,
Immunoglobulin
What is the basic structure of an Immunoglobulin ?
Its basic structure consists of 4 amino acid chains linked together by disulfide bonds.
-two large heavy chains
-two small light chains
What is the function of antibodies?
An antibody isa protein component of the immune system that circulates in the blood, recognizes foreign substances like bacteria and viruses, and neutralizes them.
These recognize the antigen and produce antibodies that bind with the specific antigen.
Blood lymphocyte and plasma cell
This results when the blood lymphocyte and plasma cell recognize the antigen and produce antibodies that bind with the specific antigen.
agglutination
This is the process wherein foreign substances are removed.
phagocytosis
This form of immunoglobulin is a monomer found in tissue fluids and plasma proteins.
Immunoglobulin G
Where is the Immunoglobulin G located?
placenta (passive immunity).
What are the functions of the Immunoglobulin G ?
(1) Attacks foreign antigens (bacteria and virus)
(2) Opsonin (substances that enhance phagocytosis)
This type of immunoglobulin is a minor circulating Ab and is a monomer.
Immunoglobulin D
Where is the Immunoglobulin D found?
on the surface of B lymphocytes (BCR).
What is the function of Immunoglobulin D ?
B cell activation
This is a Dimer in secretions and a monomer in serum as well as a major secretory Ab
Immunoglobulin A
Where is the Immunoglobulin A located?
found in secretions (saliva, colostrum, serum), nasal
fluid, tears, gastric and intestinal juice, bile, and urine.
What is the function of Immunoglobulin A?
Inhibits glycolitic metabolism of bacteria.
This type of immunoglobulin is found in blood and lymph
Immunoglobulin E
What are the functions of immunoglobulin e?
Binds to mast cells releasing histamine,
Involved in allergic reactions
Attacks allergic -causing antigens
Kills parasites
This type of immunoglobulin is a pentamer and the 1st Ab to appear after immunization, binds complement strongly
Immunoglobulin M
Where is the immunoglobulin m developed?
Develops in blood plasma. (fixes complement)
