proteins part 2 Flashcards
____________ are biological catalyst –ex:
Pepsin, Trypsin
Enzymes
_______________ include antibodies
(Immunoglobulins) which are specific
protein molecules produced by
specialized cells of the immune system
in response to foreign antigens.
Defense Proteins include antibodies
(Immunoglobulins) which are specific
protein molecules produced by
specialized cells of the immune system
in response to foreign antigens.
- Membrane-bound immunoglobulin on the surface of immature and mature B cells
- First antibody produced in a primary response to an antigen
- First antibody produced by the fetus
- Efficient in binding antigens with many repeating epitopes, such as viruses
Classical complement activation
IgM (serum level-5%)
- Membrane-bound immunoglobulin on the surface of mature B cells
- No biological effector function known
igD (serum level-0.3%)
- Predominant antibody class in secretions (saliva, tears, breast milk) and mucosa
- First line of defense against infection by microorganisms
igA (serum level 7-15%)
- Most abundant class with four isotypes - IgGI, IgG2, IgG3, IgG4
Crosses the placenta
-Opsonization
igG (serum level-85%)
- Defense against parasite infections
- Associated with hypersensitivity reactions (allergies)
- Found mainly in tissues
igE (serum level- 0.02%)
_______________ carry material from place to another in the body. Ex: transferrin,
Hemoglobin and Myoglobin.
Transport Protein
____________ controls many aspects of cell
function, including metabolism and
reproduction. Ex: Insulin and Glucagon
Regulatory Protein controls many aspects of cell function, including metabolism and reproduction. Ex: Insulin and Glucagon
_______________ provide mechanical support to large animals and provide them with their outer coverings. Ex:
Keratin
Structural proteins provide mechanical support to large animals and provide them with their outer coverings. Ex:
Keratin
______________ are necessary for all forms of
movement. Ex. Actin and Myosin, Flagella of sperm cell.
Movement Proteins
______________ serves as source of Amino acids for embroyos or infants. Ex: Albumin and Casein
Nutrient Protein
• It is the amino acid sequence of the protein chain.
• This structure will determine its biological active form.
• It results from the covalent bonding between the amino acids in the chain
Primary Structure of Proteins
This level of structure describes the local folding pattern of the polypeptide backbone and is stabilized by hydrogen bonds between N-H and C=O groups. The most common are the orderly repeating forms known as the a helix and the b sheet.
Secondary Structure proteins
The most common type of Secondary structure may it be in coiled of helical conformation.
Special Feature:
-Every amide hydrogen and carbonyl oxygen associated with the peptide backbone is involved in a hydrogen bond when the chain coils into it.
- Every carbonyl oxygen is hydrogen bonded to an amide hydrogen four amino acids away in the chain.
a-Helix
– are structural proteins arranged in fibers or sheets that have only one type of secondary structure.
Fibrous Proteins
– are fibrous proteins that form
the covering (hair, nails and fur) of most land animals.
α-Keratins
The second common secondary structure in proteins resembles the pleated folds of drapery.
All the carbonyl oxygen and amide hydrogens in this are involved in hydrogen bonds, and the polypeptide chain is nearly completely
extended.
β-Pleated Sheet
What are the 2 Orientation of B-Pleated
form?
- Parallel
- Anti-parallel
• Beta sheets are ______ if the polypeptide strands run in the same direction,
N-terminus to C-terminus. The N-terminus of one beta strand will be opposite the N-terminus of the other beta strand.
the arrangement is less stable because the geometry of the individual amino acid molecules forces the hydrogen bonds
to occur at an angle, making them longer and thus weaker.
parallel
• Beta sheets are ___________ if the polypeptide strands run in opposite directions. The N- terminus of one beta strand will be opposite the C-terminus
of the other beta strand.
- in this the arrangement hydrogen bonds are aligned directly opposite each other, making for stronger and more stable bonds.
anti-parallel
________________________ forms when a polypeptide chain sharply reverses direction. This can occur in the presence of two consecutive proline residues, which create an angled kink in the polypeptide chain and bend it back upon itself.
Anti-parallel beta-pleated sheet forms when a polypeptide chain sharply reverses direction. This can occur in the presence of two consecutive proline residues, which create an angled kink in the polypeptide chain and bend it back upon itself.
- A protein whose structure is an antiparallel B-pleated sheet.
- The polypeptide chains of a B-pleated sheet are almost completely extended, and silk does not stretch easily.
Silk Fibroin
- ___________ accounts for nearly half of the amino acids of silk fibroin. Alanine and serine account for most of the others,
Glycine
•it is the complete three-dimensional (3-D) structure of a polypeptide. It is formed
spontaneously and stabilized both
by side chain interactions and, in
extracellular proteins, by disulfide
bonds. This folding brings distant
sequences in a linear polypeptide
together into a stable structure
Tertiary Structure of Proteins
Tertiary structure is maintained by the following molecular interactions:
- ______________ between the R groups of non polar amino acids that are hydrophobic.
- _______________ between the polar R group of the polar amino acids
- _______________ (salt bridges) between the R groups of oppositely charged amino acids
- _______________ between the thiol containing amino-acids.
Tertiary structure is maintained by the following molecular
interactions:
- Van der Waals Forces between the R groups of non polar amino acids that are hydrophobic.
- Hydrogen bonds between the polar R group of the polar amino acids
- Ionic bonds (salt bridges) between the R groups of oppositely charged amino acids
- Covalent bonds between the thiol-containing amino
acids.
______________ generally have a more
compact and rounded shape and have functional roles (they do something)
Globular proteins
• some proteins are made up of multiple polypeptide chains, also known as subunits. When these subunits come together, they give the protein its _________________.
• The forces that hold the structure of a
protein are the same as those that hold the tertiary structure.
Quaternary Structure
_______________ – when a non-protein group is added to the functional protein. Ex: Glycoprotein
Prosthetic group
Protein digestion is the degradation of protein by cellular enzymes
in a process called _________
Protein digestion is the degradation of protein by cellular enzymes in a process called hydrolysis
The macromolecules are the _________ or
polypeptides themselves, and the subunits are the ______________.
The macromolecules are the proteins or polypeptides themselves, and the subunits are the amino acids.
Protein Digestion
• It takes place in two different phases:
- In the stomach
- In the small intestine.
Both of these phases of digestion are based on several types of enzymes that are called ___________ and __________.
Protein Digestion
• It takes place in two different phases:
- In the stomach
- In the small intestine.
Both of these phases of digestion are based on several types of enzymes that are called Proteinases and Proteases.
__________ –endo & exo peptidases:
- Enzymes that degrade proteins by hydrolysis of peptide bonds
Proteases
__________ - endo peptidases; proteases that show specificity for intact proteins
Proteinases
_____________ – Stimulates Parietal cells to secrete HCl; Chief cells of the gastric glands to secrete pepsinogen.
Gastrin
_______________ - Denatures protein stucture. Activates pepsinogen (Zymogen) to pepsin.
HCI / Hydrochloric Acid
_________ - Hydrolyzes proteins to smaller polypeptides and some free amino acids.
Pepsin
The remainder of protein digestion occur in the ____________ as the result of the action of enzymes such as trypsin (secreted by the pancrease) and petidases (located in the cells that line the small intestine).
small intestine
____________ - Stimulates the pancreas to secrete bicarbonate into the small intestine to neutralize the gastric HCl
Secretin
_______________- Stimulates secretion of several pancreatic enzyme with activity optima pH 7 to 8.
Cholecystokinin
- Activates chymotrpsinogen → chymotrypsin
- Further hydrolyze the peptides that were produced by pepsin in the stomach specifically the peptide bonds next to Lys and Arg.
Trypsin
____________ - Cleaves peptide bonds next to Phe, Tyr, Trp, Met, Asp and His
Chymotrypsin
Occur when the organized structures of a globular protein, the a-helix, the B-pleated sheet and tertiary folds become completely disorganized. However, it does not alter the primary structure.
Denaturation of protein
Factors that cause Denaturation
- Temperature
- Coagulation
- pH
- Organic solvents
- Heavy metals
-Mechanical Stress - Detergents
As the ___________ increase, molecular movement also increase and the bonds within the cells vibrate more violently which results to disruption of protein structure.
As the temperature increase, molecular movement also increase and the bonds within the cells vibrate more violently which results to disruption of protein structure.
occur as the protein molecules unfold and become untangled. At this point they are no longer in solution; they have aggregated to become solid
Coagulation
A high concentration of hydrogen ions (low pH) will result in more groups being protonated. Carboxyl groups (aspartic acid, glutamic acid, the carboxy terminus) and phenolic groups are uncharged when protonated. The nitrogen groups (amines on lysine, guanidino of arginine, and imidazole in histidine, etc.) are charged when protonated
pH
_____________ such as rubbing alcohol (2-propanol), denatured proteins by disrupting hydrogen bonds within the protein, in addition to forming hydrogen bonds with the solvent, water Nonpolar regions of these solvents interfere with hydrophobic interactions in the interior of the protein molecules, thereby disrupting the conformation.
Polar organic solvent
- Mercury (Hg2+) or Lead (Pb2+) may form negatively charged side chain groups.
- may also bind to sulfhydryl groups of a protein that can accompanied by loss of function.
Heavy metals
__________ have hydrophobic region and hydrophilic. When it interacts with proteins, they disrupt hydrophobic interactions, causing the protein chain to unfold.
Detergent
- Stirring, whipping, or shaking can disrupt the weak interactions that maintain protein conformation. This is the reason that whipping egg whites produces a stiff meringue.
Mechanical Stress
amino acid sequence of a protein is encoded in ______ .
amino acid sequence of a protein is encoded in DNA
amino acid sequence of a protein is encoded in ______ .
amino acid sequence of a protein is encoded in DNA
Proteins are synthesized by a series of steps called __________ (the use of a DNA strand to make a complimentary messenger RNA strand -mRNA) and translation (the mRNA sequence is used as a template to guide the synthesis of the chain of amino acids which make up the protein)
Proteins are synthesized by a series of steps called transcription (the use of a DNA strand to make a complimentary messenger RNA strand -mRNA) and translation (the mRNA sequence is used as a template to guide the synthesis of the chain of amino acids which make up the protein)
________ can change by the process of mutation during the course of evolution.
A mutation of this can result in a change in the primary acid sequence of a protein.
Genes
The ______________ is the result of hydrogen bonding between the amide Hydrogen and carbonyl oxygens of the
peptide bonds.
The secondary structure is the result of hydrogen bonding between the amide Hydrogen and carbonyl oxygens of the
peptide bonds.
Types of Secondary Structure
- α-Helix
- β-Pleated Sheet
Types of Secondary Structure
- α-Helix
- β-Pleated Sheet
