PROTEINS

An essential amino acid is a standard amino acid needed for protein synthesis that must be obtained from dietary sources because the human body cannot synthesize it in adequate amounts from other substances.

A zwitterion is a molecule that has a positive charge on one atom and a negative charge on another atom, but which has no net charge.

Hemoglobin, which is a tetramer consisting of two identical alpha chains and two identical beta chains, each enfolding a heme group.

No, protein denaturation does not affect the primary structure of a protein.

At low pH, all acid groups are protonated (-COOH) and all amino groups are protonated (-N+H3).

The C-terminal amino acid keeps its full name, while other residues end in -yl, except for specific amino acids like tryptophan and cysteine.

Antigen binding to the variable region of an immunoglobulin occurs through hydrophobic interactions, dipole-dipole interactions, and hydrogen bonds, rather than covalent bonds.

Hydrogen bonds are weak attractions between polar side chains containing functional groups like -OH, -NH2, and -C=O, and can be easily disrupted by changes in pH and temperature.

Myoglobin molecules have a red color when oxygenated and a purple color when deoxygenated.

The carbohydrate groups in collagen assist in cross-linking, helping to assemble collagen triple helices into more complex structures called collagen fibrils.

Detergents affect R-group interactions.

Collagen has a triple helix structure formed when three chains of amino acids wrap around each other.

Isomeric peptides are peptides that contain the same amino acids but in different order, resulting in different molecules with different properties.

A simple protein is a protein that contains only amino acid residues.

Chirality in amino acids refers to the presence of four different groups attached to the α-carbon atom, making them chiral, except for glycine, which is achiral.

A dipeptide is a compound containing two amino acids.

A limiting amino acid is an essential amino acid that is missing, or present in inadequate amounts, in an incomplete dietary protein.

In solution, amino acids can exist in three different forms: zwitterion, negative ion, and positive ion.

A peptide bond links amino acids together in a peptide chain.

Complete hydrolysis is when all peptide bonds are broken down, freeing all constituent amino acids, resulting in amino acids as the only products.

An amino acid is an organic compound that contains both an amino (–NH2) group and a carboxyl (–COOH) group.

The isoelectric point of alanine is 6.01.

Cysteine readily dimerizes to form a cystine molecule through a covalent disulfide bond.

Proteins account for about 15% of a cell’s overall mass.

Alcohols, such as isopropyl or ethyl alcohol, act as denaturing agents, causing denaturation of bacterial proteins.

The significance of immunoglobulins is highlighted by the effects of AIDS, which disrupts normal immunoglobulin production and increases susceptibility to infections.

Cysteine is the only standard amino acid that has a side chain containing a sulfhydryl group.

Protein denaturation is the partial or complete disorganization of a protein’s three-dimensional shape due to disruption of its structural interactions, resulting in loss of biochemical activity.

There are nine essential amino acids for adults, and a tenth one is needed for growth in children.

A peptide chain has directionality from the N-terminal end to the C-terminal end.

Cooking denatures proteins, making them easier to digest and killing microorganisms.

Essential amino acids are those that cannot be synthesized adequately by the adult human body and must be obtained from dietary protein.

At the isoelectric point, amino acids become insoluble due to having a net charge of zero.

A complete dietary protein is a protein that contains all of the essential amino acids in the same relative amounts in which the body needs them.

The isoelectric point is the pH at which an amino acid exists primarily in its zwitterion form, having no net charge.

The R group, or amino acid side chain, distinguishes α-amino acids from each other and varies in size, shape, charge, acidity, and chemical reactivity.

Individuals receiving organ transplants must take drugs to suppress immunoglobulin production against foreign proteins in the new organ to prevent rejection.

The primary structure of proteins is the order in which amino acids are linked together in a protein chain, specifically the sequence of amino acids connected by peptide bonds.

Transport proteins bind and transport small biomolecules to specific locations in the body, such as hemoglobin for oxygen transport.

Organic solvents interfere with R-group interactions and hydrogen bonds, denaturing proteins in bacteria.

Hemoglobin transports oxygen from the lungs to tissues and can transport four oxygen molecules at the same time.

The number of constitutional isomers is given by n! (n factorial).

A conjugated protein is a protein that has one or more non-amino acid entities present in its structure in addition to one or more peptide chains.

An oligopeptide refers to peptides with 10 to 20 amino acid residues.

Proteins contain carbon, hydrogen, oxygen, and nitrogen; most also contain sulfur.

Breastfeeding provides immunoglobulins from the mother to the newborn, offering protection against pathogens the mother is immune to during the initial days of lactation.

The first biochemist to determine the primary structure of a protein was Frederick Sanger, and the protein was insulin.

Defense proteins, also known as immunoglobulins or antibodies, bind to foreign substances like bacteria and viruses to combat invasion.

Strong acids and bases disrupt hydrogen bonds and salt bridges, potentially leading to peptide bond hydrolysis.

Myoglobin functions as an oxygen storage molecule in muscles, serving as a reserve oxygen source when demand exceeds supply from hemoglobin.

Small peptide hormones give cells signals and are involved in various physiological processes.

Hemoglobin is a hemoprotein that serves as a carrier of oxygen in the blood.

The quaternary structure is the highest level of protein organization found only in multimeric proteins, involving two or more independent peptide chains that are not covalently bonded.

The presence of nitrogen in proteins sets them apart from carbohydrates and lipids, which most often do not contain nitrogen.

A beta pleated sheet structure is a protein secondary structure where two fully extended protein chain segments are held together by hydrogen bonds, forming a repeated zigzag pattern.

Insulin regulates blood-glucose levels by assisting the entry of glucose into cells and facilitating the conversion of glucose to glycogen when blood-glucose levels are high.

Contractile proteins enable movement, including muscle contraction and extension in response to nerve stimuli, with actin and myosin as key examples.

Reducing agents reduce disulfide linkages, producing -SH groups.

It can dissociate into dimers or separate subunits, resulting in a temporary loss of protein activity.

Nonpolar amino acids contain one amino group, one carboxyl group, and a nonpolar side chain; they are hydrophobic and found in the interior of proteins.

Unstructured segments of proteins are neither alpha helices nor beta pleated sheets and often have the flexibility to bind to several different protein partners.

The alpha helix structure is maintained by hydrogen bonds between C=O and N-H groups, which are oriented parallel to the helix axis.

A glycoprotein is a protein that contains carbohydrates or carbohydrate derivatives in addition to amino acids.

Fibrous proteins have an elongated shape with one dimension much longer than the others and tend to have simple, regular, linear structures.

Vasopressin is also known as antidiuretic hormone (ADH).

In complete hydrolysis, all peptide bonds are broken, while in partial hydrolysis, some peptide bonds are broken, producing a mixture of free amino acids and small peptides.

The amino acids found in proteins are always α-amino acids.

Immunoglobulin molecules consist of four polypeptide chains: two identical heavy (H) chains and two identical light (L) chains, with constant and variable regions.

Electrostatic interactions, also known as salt bridges, involve the interaction between an acidic side chain and a basic side chain.

The amount of myoglobin present in a muscle is determined by how the muscle is used; heavily used muscles require larger amounts of myoglobin.

When collagen is boiled in water under basic conditions, it converts into the water-soluble protein gelatin through denaturation and hydrolysis.

Ultraviolet radiation operates similarly to heat, disrupting hydrogen bonds.

Alpha keratin is a fibrous protein found in protective coatings for organisms, such as hair, feathers, and nails.

Coagulation is the precipitation out of biochemical solution of denatured protein, often resulting in loss of water solubility.

Polar acidic amino acids contain one amino group and two carboxyl groups, with a side chain that bears a negative charge at physiological pH.

The tertiary structure of proteins is the overall three-dimensional shape that results from interactions between widely separated amino acid side chains within a peptide chain.

Globular proteins have peptide chains that are folded into spherical or globular shapes and are generally water-soluble.

Vasopressin decreases urine output to reduce water elimination from the body, especially during dehydration.

There are 20 standard α-amino acids normally found in proteins.

The primary structures of insulin in cows, pigs, sheep, and horses are very similar to each other and to human insulin, but animal insulin is considered foreign to the human body.

Messenger proteins transmit signals to coordinate biochemical processes among cells, tissues, and organs; examples include insulin and glucagon.

Salts of heavy metals combine with -SH groups to form poisonous salts.

The two best-known peptide hormones are oxytocin and vasopressin.

Glycoproteins, which contain carbohydrates, serve various functions including acting as antibodies and lubricants in mucous secretions.

The four categories are nonpolar amino acids, polar neutral amino acids, polar acidic amino acids, and polar basic amino acids.

In a beta pleated sheet, hydrogen bonds between C=O and N-H groups lie within the plane of the sheet.

The two most common types of secondary protein structure are the alpha helix and the beta pleated sheet.

Structural proteins provide stiffness and rigidity to tissues; collagen supports cartilage, while keratin strengthens hair and nails.

Immunoglobulins are crucial soluble proteins that function as glycoproteins produced in response to the invasion of microorganisms or foreign molecules, serving as antibodies that combat antigens.

The four types of interactions are covalent disulfide bonds, electrostatic attractions (salt bridges), hydrogen bonds, and hydrophobic attractions.

Disulfide bonds are the strongest of the tertiary structure interactions, formed by the reaction of -SH groups from two cysteine residues, creating covalent bonds either within the same chain or between different chains.

Myoglobin serves as the oxygen storage protein that provides molecular oxygen necessary for muscle contraction.

Hydrophobic interactions are attractions between nonpolar side chains due to London forces.

Catalytic proteins, or enzymes, facilitate biochemical reactions and play a critical role in genetics and metabolic processes.

Violent whipping or shaking stretches and entangles molecules in globular shapes.

A monomeric protein has only one peptide chain, while a multimeric protein has more than one peptide chain.

Collagen qualifies as a glycoprotein due to the presence of carbohydrate units in its structure.

Heat disrupts hydrogen bonds, causing molecules to vibrate excessively and produces coagulation.

Enkephalins are pentapeptide neurotransmitters produced by the brain that bind to receptor sites to reduce pain.

Microwave radiation causes violent molecular vibrations that disrupt hydrogen bonds.

Membrane proteins are associated with a membrane system of a cell, tend to be water-insoluble, and usually have fewer hydrophobic amino acids than globular proteins.

Glutathione functions as an antioxidant, protecting cellular contents from oxidizing agents.

The three main types of proteins are fibrous, globular, and membrane proteins.

Oxytocin regulates uterine contractions and lactation, stimulating the flow of milk in nursing mothers.

A protein is defined as a naturally occurring, unbranched polymer in which the monomer units are amino acids, containing at least 40 amino acid residues.