NSC-350 QUIZ 2 GCU EXAM WITH
COMPLETE SOLUTIONS
Structure of Protein - ANSWER carbon, hydrogen, oxygen, nitrogen, and sometimes
sulfur
-may also contain iron, copper, phosphorus, or zinc
Amino acids - ANSWER a simple organic compound containing a side chain of carbon
and hydrogen atoms, a carboxyl (—COOH) and an amine (—NH2) group.
In a protein the carboxyl group acts as an? - ANSWER acid
In a protein the amine group acts as a? - ANSWER base
What happens when 2 amino acids combine - ANSWER a peptide bond is formed and
water is released
What is a polypeptide? - ANSWER a chain of amino acids bound together by peptide
bonds
What are proteins classified by - ANSWER nutritional use and chemical nature of their
side chains
How are proteins classified by nutritional use - ANSWER -20 amino acids needed by
body fro growth and body function
-dispensable (nonessential) amino acids
-indispensable (essential) amino acids
Indispensable amino acids - ANSWER 9 essential amino acids that are not made by the
body and must be supplied by the diet
Conditional indispensable amino acids - ANSWER conditionally essential
Complete proteins - ANSWER contain all the indispensable amino acids
incomplete proteins - ANSWER short one or more of the essential amino acids
-combining incomplete proteins, such as red beans and rice form a complete protein
Classification by side chains - ANSWER -the shape and function of protein depend on
the polarity of the side chains
Side chains can be - ANSWER nonpolar, uncharged polar, positively charged, or
negatively charged
,Nonpolar side chain - ANSWER less soluble in water and are attracted to other nonpolar
compounds, such as lipids and cholesterol
amino acids with neutral polar side chains will? - ANSWER form hydrogen bonds and are
attracted to other polar molecules, such as water
positively and negatively charged side chains - ANSWER enable some proteins to act as
buffers
Proteins are complex molecules because of the? - ANSWER -number of amino acids
-order in which they combine
-interaction of the side chains
Primary structure - ANSWER order the amino acids occur in the chain
-results from the chain of peptide bonds
secondary structure - ANSWER refers to the shape of the sections of the amino acid
helix - ANSWER repeating coil
random coil - ANSWER is tangled and twisted
pleated sheet - ANSWER like a paper fan
Tertiary structure - ANSWER -the 3-dimensional structure of an entire amino acid chain
-globular proteins do not form networks
-fibrous proteins are usually made from helix-shaped strands, are strong and elastic,
and form networks
Molecular interactions of proteins - ANSWER a hydrogen bond can form between
hydrogen atom of one side chain and hydroxyl group of another
disulfide cross-links - ANSWER covalent bonds between 2 protein molecules at side
chains containing sulfur
the more disulfide bonds - ANSWER the more stable the molecule
hydrophobic - ANSWER interactions occur between side chains that are nonpolar
hydrophobic proteins include - ANSWER caseins in milk that form cheese curds
whey-a by product of cheese production
myoglobin - ANSWER iron-building protein pigment in muscle that provides color
protein pigment - ANSWER bright red-oxygen muscle is attached
,purplish-oxygen molecule is not attached
brown-prolonged exposure to oxygen
Oxidation - ANSWER adding oxygen
reduction - ANSWER removing oxygen
Nitrites - ANSWER added during the curing process to preserve meats
Denaturation of proteins - ANSWER -change in the shape without breaking the peptide
bond
-loosening or unfolding of the tertiary and sometimes secondary structure
-sometimes reversible
-involves only hydrogen bonds
Is breaking disulfide cross-links reversible? - ANSWER no
Coagulation - ANSWER permanent denaturation
-results when liquid or semi-liquid proteins from solid or semisoft clots
Coagulation of a protein - ANSWER -changes its physical characteristics
-alters the ability to bind with water
-interferes with biological interactions of enzymes
which denatured proteins can return to their original state? - ANSWER eggs whites
Physical methods of denaturing protein - ANSWER -temperature changes
-mechanical actions
-sound waves and irradiation
Chemical methods of denaturing proteins - ANSWER - Change in pH
- Exposure to mineral salts or metals
what do food scientists analyze to determine the effectiveness of protein in food? -
ANSWER -degree of water
absorption
-solubility
, -viscosity
-stability in acids and
alkalis
Functions of Protein in Food - ANSWER 1. form gels
2. change texture
3. emulsion
4. form foams
5. develop gluten
Proteins form gels - ANSWER mixture of fluids locked in a tangled 3-dimensional mesh of
denatured and coagulated protein
-Gels have 2 parts
the 3-dimensional
molecular structure and liquid that is attracted
to the protein
-Protein gel has a narrow melting and
solidifying temperature range
Gel stability - ANSWER -increases with mineral salts,
hard water, more gelatin, and
slow cooling rates
-decreases with acids, sugar,
food pieces, and rapid cooling
Proteins can change texture - ANSWER -Most globular proteins can
COMPLETE SOLUTIONS
Structure of Protein - ANSWER carbon, hydrogen, oxygen, nitrogen, and sometimes
sulfur
-may also contain iron, copper, phosphorus, or zinc
Amino acids - ANSWER a simple organic compound containing a side chain of carbon
and hydrogen atoms, a carboxyl (—COOH) and an amine (—NH2) group.
In a protein the carboxyl group acts as an? - ANSWER acid
In a protein the amine group acts as a? - ANSWER base
What happens when 2 amino acids combine - ANSWER a peptide bond is formed and
water is released
What is a polypeptide? - ANSWER a chain of amino acids bound together by peptide
bonds
What are proteins classified by - ANSWER nutritional use and chemical nature of their
side chains
How are proteins classified by nutritional use - ANSWER -20 amino acids needed by
body fro growth and body function
-dispensable (nonessential) amino acids
-indispensable (essential) amino acids
Indispensable amino acids - ANSWER 9 essential amino acids that are not made by the
body and must be supplied by the diet
Conditional indispensable amino acids - ANSWER conditionally essential
Complete proteins - ANSWER contain all the indispensable amino acids
incomplete proteins - ANSWER short one or more of the essential amino acids
-combining incomplete proteins, such as red beans and rice form a complete protein
Classification by side chains - ANSWER -the shape and function of protein depend on
the polarity of the side chains
Side chains can be - ANSWER nonpolar, uncharged polar, positively charged, or
negatively charged
,Nonpolar side chain - ANSWER less soluble in water and are attracted to other nonpolar
compounds, such as lipids and cholesterol
amino acids with neutral polar side chains will? - ANSWER form hydrogen bonds and are
attracted to other polar molecules, such as water
positively and negatively charged side chains - ANSWER enable some proteins to act as
buffers
Proteins are complex molecules because of the? - ANSWER -number of amino acids
-order in which they combine
-interaction of the side chains
Primary structure - ANSWER order the amino acids occur in the chain
-results from the chain of peptide bonds
secondary structure - ANSWER refers to the shape of the sections of the amino acid
helix - ANSWER repeating coil
random coil - ANSWER is tangled and twisted
pleated sheet - ANSWER like a paper fan
Tertiary structure - ANSWER -the 3-dimensional structure of an entire amino acid chain
-globular proteins do not form networks
-fibrous proteins are usually made from helix-shaped strands, are strong and elastic,
and form networks
Molecular interactions of proteins - ANSWER a hydrogen bond can form between
hydrogen atom of one side chain and hydroxyl group of another
disulfide cross-links - ANSWER covalent bonds between 2 protein molecules at side
chains containing sulfur
the more disulfide bonds - ANSWER the more stable the molecule
hydrophobic - ANSWER interactions occur between side chains that are nonpolar
hydrophobic proteins include - ANSWER caseins in milk that form cheese curds
whey-a by product of cheese production
myoglobin - ANSWER iron-building protein pigment in muscle that provides color
protein pigment - ANSWER bright red-oxygen muscle is attached
,purplish-oxygen molecule is not attached
brown-prolonged exposure to oxygen
Oxidation - ANSWER adding oxygen
reduction - ANSWER removing oxygen
Nitrites - ANSWER added during the curing process to preserve meats
Denaturation of proteins - ANSWER -change in the shape without breaking the peptide
bond
-loosening or unfolding of the tertiary and sometimes secondary structure
-sometimes reversible
-involves only hydrogen bonds
Is breaking disulfide cross-links reversible? - ANSWER no
Coagulation - ANSWER permanent denaturation
-results when liquid or semi-liquid proteins from solid or semisoft clots
Coagulation of a protein - ANSWER -changes its physical characteristics
-alters the ability to bind with water
-interferes with biological interactions of enzymes
which denatured proteins can return to their original state? - ANSWER eggs whites
Physical methods of denaturing protein - ANSWER -temperature changes
-mechanical actions
-sound waves and irradiation
Chemical methods of denaturing proteins - ANSWER - Change in pH
- Exposure to mineral salts or metals
what do food scientists analyze to determine the effectiveness of protein in food? -
ANSWER -degree of water
absorption
-solubility
, -viscosity
-stability in acids and
alkalis
Functions of Protein in Food - ANSWER 1. form gels
2. change texture
3. emulsion
4. form foams
5. develop gluten
Proteins form gels - ANSWER mixture of fluids locked in a tangled 3-dimensional mesh of
denatured and coagulated protein
-Gels have 2 parts
the 3-dimensional
molecular structure and liquid that is attracted
to the protein
-Protein gel has a narrow melting and
solidifying temperature range
Gel stability - ANSWER -increases with mineral salts,
hard water, more gelatin, and
slow cooling rates
-decreases with acids, sugar,
food pieces, and rapid cooling
Proteins can change texture - ANSWER -Most globular proteins can
