Chapter 18 Flashcards
The pH at which a sample of amino acids has equal numbers positive and negative charges
Isoelectric point
What does an amino acids isoelectric point influence?
Protein solubility and determines which amino acid in enzymes participate in enzyme reactions
Amino acids that can form crystals, have high melting points, are soluble in water but not hydrocarbon solvents are what?
Pure amino acids
Amino acids that accept proteins of their basic COO- group to leave only a positively charged NH3+ are what?
Low pH amino acids
Amino acids that lose protons from their acidic NH3+ group to leave only negatively charged COO- groups are what?
High pH amino acids
How many amino acids are chiral? Which ones aren’t?
19 are chiral, glycine isn’t (it’s identical)
Do right or left handed enantiomers make proteins
Left handed enantiomers
The sequence in which amino acids are linked by peptide bonds in a protein
Primary structure
T or F
Primary structures form ridged planar peptide units
True
Regular and repeating structural patterns created by hydrogen binding between backbone atoms in neighboring segments of protein chains
Secondary structure
What are the two kinds of repeating patterns of secondary structures?
Alpha helix and beta sheets
Do alpha helixes and beta sheets hydrogen bond?
Yes to keep backbone in place
Overall 3- dimensional shape that results from the folding of a single protein chain
Tertiary structure
The way in which two or more protein chains aggregate to form large ordered structures
Quaternary structure
What are the two protein types of secondary structure?
Fibrous protein and globular protein
Tough insoluble protein whose protein chains form fibers/ sheets is globular or fibrous protein?
Fibrous
Water soluble protein whose chain is folded in compact shape with hydrophilic groups on outside is globular or fibrous protein?
Globular
Extremely stable structure where protein chain forms right handed coil stabilized by hydrogen bonds between peptide groups along its backbone
Alpha helix
Protein structure where adjacent protein chains in same/ different molecules are held together by hydrogen bonds along its backbone forming a flat sheet structure
Beta sheets
What protein is fibrous and makes up about 30% total proteins?
Collagen
Protein hydrolysis is where peptides turn into _____
Amino acids
Is an acidic or basic solution better for hydrolysis and why?
Acidic because a basic solution can destroy some amino acids
What is a protein with the shape in which it exists naturally in living organisms? What type of protein structure is it?
Native structure, can be any 1-4 protein structures
A disruption in the shape of the protein that does not affect the order of amino acids within a protein chain
Denaturation
Which structures are and are not affected by denaturation
Only primary protein structures not lost
Other structures lost because of non covalent interactions or disulfide bonds leaving
Denaturation can be caused by heat, ______, ________, organic compounds, ___, or _________.
Mechanical agitation
Detergents
Organic compounds
pH changes
Inorganic salts
Can renaturation happen?
Possibly but not usually
peptides and proteins are always written with the ___ terminal on the left and the ___ terminal on the right
N
C
The C terminal amino acid has a free ____ group at the end of the protein
-COO group
The N terminal amino acid has a free _____ group that’s at the end of the protein
-NH3+
Individual amino acids joined in the polypeptide chain are called what?
Residues
Why are proteins usually least soluble in water at their isoelectric point?
At isoelectric point their neutral which makes them least soluble (charged proteins are more soluble)
What type of bonding is responsible for secondary structures?
Hydrogen bonding
Is hydrogen bonding covalent or noncovalent?
Noncovalent
Are alpha helixes usually fibrous or globular?
Fibrous (hair, nails, wool)
Are B-sheets usually fibrous or globular?
Globular
Spontaneous folding into correct tertiary structures is caused by _____ residues interacting with aqueous environments and _____ residues folding away and into each other
Hydrophilic
Hydrophobic
What is a conjugated protein?
Protein with one or more non protein molecules
Why is cysteine such an important amino acid for defining tertiary structure of some proteins?
Disulfide bonds stabilize tertiary structure
Which structure coils and fold the entire protein chain?
Teritary
Which structure orients segments of polypeptides into patterns?
Secondary
What type of bonds hold amino acids together in primary structure?
Peptide bonds
What is the minimum number of polypeptide chains necessary for quaternary structures to exist?
2
Myoglobin is an example of a ____ protein
Conjugated
______ functions to carry oxygen in red blood cells
Hemoglobin
What type of bonds connect insulin?
Disulfide bonds
What is the difference between protein digestion and denaturation?
Digestion= protein —> amino acids
Denaturation= 4 protein —> 1 protein and loss of function
Does protein hydrolysis end with the amino acids losing function?
No loss of function
