Protiens Flashcards
Proteins
Most diverse and complex molecules in living organisms
Their diversity is due to the diversity of the genes that code for them
They are extremely diverse due to the number of different monomers (20 amino acids) and the combinations made with them.
Proteins are large polymers that consists of many amino acid subunits joined together by peptide bonds into folded three-dimensional molecules
Include C, H, O, N, and S
Molecular Structure of Proteins
Atoms:
C, H, O, N, S (some)
Monomers:
20 different amino acids (8 (9) essential)
Distinguished by their side chain R group off of central (α) carbon
polar
Structure of amino acids
Amino acids are the building blocks of protein
Amphiprotic 🡪 have both acid (carboxyl) and basic (amino) qualities
The R group changes the qualities of the amino acid
Amino acids are the building blocks of proteins
Amino acid monomers are joined together by peptide bonds to form polypeptides and proteins
General structure of amino acid: central carbon + 1 hydrogen + 1 amino group NH2 + 1 carboxyl group COOH + 1 R (side chain) which is what changes to produce different amino acids
Various texts will remove the H from the carboxyl group which makes it negatively charged
There are 20 different R groups in living organisms (therefore 20 different amino acids) – 12 can be produced in the body and 8 are essential (must be consumed)
Amino acids are amphiprotic
Amino acids may be polar (hydrophilic), non-polar (hydrophobic), or charged (acidic/basic)
Amino acids to memorize
non polar
Glycine (Gly) –> R=H
Alanine (ala) –> R=Ch3
polar
Serine (ser) R–> cH2 - Oh
Cystine (cys) R –> CH2 - SH
Electrically charged (acidic)
Asparatic acid (ASP) R—> CH2 – C – OO-
Essential Amino Acids
There are 8 (9) essential amino acids, these amino acids CANNOT be synthesized by the body and must be obtained through diet ((histidine), isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine)
Tryptophan is mainly in meat, thus vegetarians must eat accordingly to offset missing amino acids
If an individual is missing certain essential amino acids, what are some possible consequences?
Protiens linkage
Peptide bond between amino acids is formed during condensation reaction
Forms polymer molecule (polypeptide)
Protein synthesis (dehydration synthesis reaction) has amino acid monomers connect to one another through peptide bonds to produce peptides or polypeptides (>50 amino acids)
The reaction occurs between one of amino acid’s amino group and the other amino acid’s carboxyl group 🡪 peptide bond (-CONH)
The chain has an N (amino) terminus and a C (carboxyl) terminus
protiens reactions + polymers
Reactions:
Build: Dehydration synthesis or condensation
Break: Hydrolysis
Polymers:
Called polypeptides
End up: straight 🡪 structural protein (hair, nails)
globular 🡪 functional protein (enzyme)
3D shape determined by 4 levels of structure
The 3-dimensional shape of the protein is known as the conformation
When amino acids link together to build proteins, they can form linear chains of protein (structural like collagen) or globular proteins with 4 levels of structure
Depending on the sequence of the amino acids, a different shape is made – this is known as the conformation of a protein
Protiens primary structure
Primary Structure: the specific sequence of amino acids
What if there is an error in the sequence?
An error in the sequence could mean misfolding, which results in a different conformation. This may affect protein function.
- Sickle cell anemia – one amino acid difference in healthy hemoglobin vs sickle cell hemoglobin
Secondary strucuture
Secondary Structure: as the chain of amino acids grows, the chain coils and folds at various locations along it’s length
Since peptide bonds are polar, hydrogen bonding is possible between C=O of one amino acid and N-H of another amino acid.
Two shapes possible.
tertiary strucuture
Tertiary Structure: the supercoiling of a polypeptide controlled by side-chain interactions with it’s environment
The chain supercoils because of the interactions between the side-chains and the environment
This is mainly caused by the different polar, non-polar, and hydrophobic R groups and the interaction with water
Tertiary Structure: due to protein folding.
hydrophobic interactions (London dispersion force / van der Waals) between nonpolar R groups
H bonds form between polar R groups
Sulphur containing R groups form disulphide bridges
ionic bonds form between acidic and basic R groups
Quaternary structure
Quaternary Structure: different polypeptide chains bonding together
The specific shape of a protein allows for its specificity and selectivity as a messenger (hormone), surface receptor, building block, or enzyme
The quaternary structure is between different polypeptide chains coming together to form a 3-dimensional blob
Some proteins must form this quaternary structure to become functional (examples: collagen and hemoglobin)
Hemoglobin is a protein composed of four separate polypeptide chains; each heme protein has an iron molecule which allows each hemoglobin to transport up to 4 oxygen molecules; when there is an iron deficiency in the blood people may develop anemia
When two or more large polypeptide chains join to make a functional protein e.g. hemoglobin
Protien structure levels
- primary protien
- sequence of a chain of amino acids - secondary protien
- hydrogen bonding of the peptide backbone causes the amino acids to fold into repeating pattern - Tertiary protien structure
- 3d folding pattern due to side chain reactions - quaternary structure
- protien consisting of more than one amino acid chain
Roles of protiens
Roles:
Catalyzing chemical reactions
Provide structural support (bones, skin, nails)
Transport substance in body (hemoglobin, transport channels in cell membrane)
Enable organisms to move (actin and myosin in muscles)
Regulating cellular processes (hormones regulate cell activity, alter gene expression)
Provide defense against disease (antibodies)
Enzymes
Enzymes are biological catalysts
They make chemical reactions in the body proceed at a speed that sustains life
Examples: amylase, lipase, pepsin
Seen a lot in the food industry
Denaturation
a change in the 3D shape of a protein caused by changes in temperature, pH, ionic concentration or other environmental factors
protein enzymes function best within a narrow range of temperature, pH and salt concentration
this will occur when the protein is NOT in its original or natural environment
What happens to function of protein? Why?
Can be reversed if primary bonds remain intact e.g. slight heating
cannot be reversed if peptide bonds are broken
denaturation –> useful and dangerous!
Dangers of denaturation – fever can denature enzymes in the brain – explains why high fevers can be potentially very dangerous!
Useful denaturation – harmful bacteria used to extreme conditions cannot survive in less extreme, or meats are preserved/cooked, hair perms or straightening products
types of secondary structures
b plated sheet
alpha helix
