proteins- lecture 4 Flashcards
What are the building blocks and basic monomer of proteins?
Amino acids
What are the four key characteristics that make biomolecules well-suited to their roles in living cells?
They are compounds of carbon.
They have specific shapes and dimensions.
They have functional groups that determine their chemical properties.
They have a three-dimensional structure crucial for their interactions.
Why is carbon a fundamental element in biomolecules?
Carbon can form stable covalent bonds with many other elements, including itself, allowing for diverse and complex molecular structures.
How do functional groups contribute to the properties of biomolecules?
Functional groups determine the chemical reactivity and properties of biomolecules by influencing their interactions with other molecules.
Why is the three-dimensional structure of biomolecules important?
The three-dimensional structure dictates how biomolecules interact with each other and perform their specific biological functions.
What are the four main types of biomolecules?
Proteins, carbohydrates, lipids, and nucleic acids.
Define polymer and monomer in the context of biomolecules.
Polymer: A large molecule consisting of many similar or identical building blocks linked by covalent bonds. Monomer: The repeating units that serve as the building blocks of a polymer.
What type of bond links amino acids in a protein?
Peptide bond
What is the function of hemoglobin?
Oxygen transport in the blood
Why are proteins considered highly sophisticated molecules?
Because they occur in great variety, have diverse biological functions, and fold into specific conformations that determine their function.
What determines the function of a protein?
Its conformation (3D shape) and functional-group chemistry.
How many different amino acids are used to build proteins?
21 different amino acids.
What are the three major components of an amino acid?
An amino group (-NH3+), a carboxyl group (-COO-), and an “R” group (side chain).
What is the significance of the R group in amino acids?
The R group determines the unique properties of each amino acid, such as its structure, size, electric charge, and solubility in water.
What is meant by amino acids being “chiral”?
They have an asymmetric center, leading to two enantiomeric forms: L and D isomers.
Which configuration of amino acids is found in mammalian proteins?
L-configuration.
What are zwitterions in amino acids?
Molecules that have both positive and negative charges at a specific pH.
Which amino acids are hydrophobic?
Glycine, Alanine, Valine, Leucine, Isoleucine, Proline, Phenylalanine, Tryptophan, and Methionine.
Which amino acid has a cyclic structure and is not very hydrophobic?
Proline.
Which amino acids are positively charged at physiological pH?
Lysine, Arginine, and Histidine.
Name two amino acids with highly hydrophilic, positively charged R-groups.
Lysine and Arginine.
Which amino acids have highly hydrophilic, negatively charged R-groups?
Aspartate and Glutamate.
Which amino acids have uncharged R-groups?
Asparagine and Glutamine
Which amino acids contain sulfur?
Cysteine and Methionine.
What is unique about Cysteine’s R-group?
It is hydrophobic and highly reactive, capable of forming disulfide (S-S) links.
What is the role of cysteine in protein structure?
It forms disulfide bonds, which help stabilize protein structure.
How is a peptide bond formed?
By a condensation reaction between the carboxyl group of one amino acid and the amino group of another.
Which functional groups are involved in the formation of a peptide bond?
The α-carboxyl group of one amino acid and the α-amino group of another amino acid.
What molecule is released during the formation of a peptide bond?
Water (H₂O)
What is the resulting bond called when two amino acids are joined together?
A peptide bond.
What is the shape of the bonds around the central carbon in a peptide bond?
Tetrahedral
What is the range in size for peptides?
From small molecules containing 2-3 amino acids to macromolecules containing thousands of amino acids.
How many amino acid residues are in insulin?
30 and 21.
What is the function of corticotropin, and where is it secreted from?
Stimulates adrenal cortex, secreted from the anterior pituitary.
How many amino acid residues are in oxytocin, and where is it secreted from?
9, secreted from the post-pituitary gland.
What is the function of bradykinin?
Inhibits inflammation of tissues.
What is the function of thyrotropin-releasing factor, and where is it secreted from?
Stimulates release of thyrotropin from the anterior pituitary gland, secreted from the hypothalamus.
What is the commercial application of L-aspartylphenylalanyl methyl ester?
Aspartame (a dipeptide).
What is the function of enzymatic proteins?
Selective acceleration of chemical reactions.
example: Digestive enzymes catalyzing the hydrolysis of polymers in food.
What is the function of structural proteins?
Support.
Example: Collagen providing a fibrous framework in animal connective tissues.
What is the function of storage proteins?
Storage of amino acids.
Example: Ovalbumin in egg white serving as an amino acid source for developing embryos.
What is the function of transport proteins?
Transport of other substances.
Example: Hemoglobin transporting oxygen in the blood.
What is the function of hormonal proteins?
Coordination of an organism’s activities.
Example: Insulin regulating blood sugar concentration.
What is the function of receptor proteins?
Response of cell to chemical stimuli.
Example: Receptors in nerve cell membranes detecting chemical signals.
What is the function of contractile and motor proteins?
Movement.
Example: Actin and myosin causing muscle contraction.
What is the function of defensive proteins?
Protection against disease.
Example: Antibodies combating bacteria and viruses.
What are the four levels of protein structure?
Primary, Secondary, Tertiary, and Quaternary structure.
What is the primary structure of a protein?
The linear sequence of amino acids.
What types of bonds stabilize secondary structures?
Hydrogen bonds between the backbone atoms.
What is the secondary structure of a protein?
Folding of polypeptides into α-helices and β-sheets, stabilized by hydrogen bonds.
examples of proteins having a secondary structure
keratin
fibrous protein
What is the difference between primary and secondary protein structure?
Primary structure is the amino acid sequence, secondary structure includes helices and sheets stabilized by hydrogen bonds
What is the tertiary structure of a protein?
The overall 3D conformation of a single polypeptide chain, forming a globular protein stabilized by hydrophobic interactions between R-groups.
What interactions stabilize tertiary protein structure?
Hydrogen bonds, ionic bonds, van der Waals forces, disulfide bonds, and hydrophobic interactions.
examples of proteins having a tertiary structure
enzymes
albumin
What is the quaternary structure of a protein?
The arrangement and interaction of multiple polypeptide subunits in a functional protein.
Examples of a protein with quaternary structure.
Hemoglobin
collagen
insulin receptor
immunoglobulin
what is protein denaturation?
The loss of a protein’s 3D structure, leading to loss of function.
What factors can cause protein denaturation?
pH
temp
ionic strength
solubility
What are the two main classes of proteins based on structure?
Fibrous proteins and globular proteins.
What is the main difference between fibrous and globular proteins?
Fibrous proteins are elongated and insoluble, whereas globular proteins are spherical and soluble in water.
Give an example of a fibrous protein.
Collagen or Keratin.
Give an example of a globular protein.
Hemoglobin or Enzymes.
What are conjugated proteins?
Proteins that contain a non-protein component (prosthetic group).
Give an example of a conjugated protein and its prosthetic group.
Hemoglobin (prosthetic group: Heme).
What is the function of chaperonins?
They assist in the correct folding of proteins.
Which technique separates proteins based on charge?
Electrophoresis.
What is isoelectric focusing?
A technique that separates proteins based on their isoelectric point (pI)
Which method separates proteins based on molecular size?
Gel filtration chromatography
Which technique uses a detergent to denature proteins and separate them by molecular weight?
SDS-PAGE.
What is ultracentrifugation used for?
Separating proteins based on their molecular mass.
What is affinity chromatography?
A technique that separates proteins based on their specific binding properties.
What are plasma proteins?
Proteins found in blood plasma with various functions such as transport and immune defense.
What is the role of albumin in blood plasma?
Maintains oncotic pressure and transports substances
Which amino acid starts protein synthesis?
Methionine
Which plasma protein transports iron?
Transferrin.
What is the role of haptoglobin?
It binds free hemoglobin to prevent iron loss.
What is the function of C-reactive protein (CRP)?
It is an acute-phase protein involved in inflammation and immune response.
Which plasma protein plays a role in blood clotting?
Fibrinogen.
Which protein is a marker for liver disease?
Albumin (low levels indicate liver dysfunction).
What is the significance of alpha-fetoprotein (AFP)?
It is a fetal plasma protein, and its levels are used as a marker for certain cancers and birth defects.
What is the function of ceruloplasmin?
It binds and transports copper in the blood.
What is the significance of α1-antitrypsin?
It inhibits proteases to prevent tissue damage.
What plasma protein is a marker for neural tube defects and certain cancers?
Alpha-fetoprotein (AFP)
What is the difference between positive and negative acute-phase proteins?
Positive acute-phase proteins increase during inflammation (e.g., CRP, fibrinogen), while negative acute-phase proteins decrease (e.g., albumin, transferrin).
