Biochem
Phosphorylation/dephosphorylation of enzymes is one way of regulating enzyme activity and it involve
A. Covalent modification
B. Feedback control
C. Allosteric enzymes
D. Proteolytic enzymes and zymogens
All of the following has an enantiomer EXCEPT
Glutamic acid
Glycine
Valine
Lysine
The six-membered ring formed by an aldohexose is called a
Glycan
Furanose
Pyranose
Furfural
Which of the following statements about the B vitamins is CORRECT?
All of them have preferred names that start with a letter B.
All except two of them are water-soluble.
No correct response.
They all have similar chemical structures.
Which of the following is an INCORRECT characterization of an allosteric enzyme?
Possesses quaternary structure
Binding of regulator changes the shape of the enzyme
Substrate and regulator occupy different binding sites
Substrate and regulator compete for the same binding site
The B vitamin whose coenzyme form is involved in the transfer of an acyl group.
Biotin
Pyridoxal
Pantothenic acid
Cobalamin
All of the following are function of proteins EXCEPT
All the given choices are correct
As hormones
For transport of materials
As enzymes
It is a mechanism of regulating enzyme activity by switching “on” the enzyme only when needed.
Allosteric enzymes
Covalent modification
Proteolytic enzymes and zymogens
Feedback control
It is the pH value at which the net charge of a protein is equal to zero.
Isoelectric pH
Isoelectric point
None of the choices is correct
Equilibrium point
It refers to the reduction of a carbon-carbon double bond resulting to a saturated fatty acid.
Condensation
Oxidation
Esterification
Hydrogenation
The tripeptide made of arg-ala-asn is called
Arginylalanylasparagine
Alanylarginylasparagine
Argininealanylasparagine
Argininealanineasparagine
This vitamin is necessary for the deposition of calcium in bones and is derived from cholesterol.
Vitamin K
Vitamin E
Vitamin D
Vitamin A
The specificity of an enzyme that catalyzes the oxidation of several different alcohols is termed
absolute specificity
Group specificity
Linkage specificity
Stereochemical specificity
Inhibition of angiotensin-converting enzyme is useful for
Treating moderately high blood pressure
Treating bacterial infection
Inhibiting prostaglandin production
Reducing inflammation
The coenzyme form for which of the B vitamins contain a pyrophosphate group?
Vitamin B1
Folate
Thiamin
Vitamin B12
Which DOES NOT belong to the group?
Mannose
Fructose
Galactose
Glucose
Which of the following is NOT a function of carbohydrates?
Carbohydrates are our primary source of energy.
Carbohydrates can supply carbon atoms for the synthesis of non-carbohydrate biomolecules.
Carbohydrates found on the cell membrane can act for a cell-to-cell or cell-to-molecule recognition process.
Carbohydrates can act as messenger chemicals.
All of the following are reducing sugars EXCEPT
Lactose
Maltose
Cellobiose
Sucrose
All of the following are considered as sugar EXCEPT
Starch
Sucrose
Lactose
Maltose
When glucose-6-phosphate is transformed into glucose-1- phosphate, the enzyme involved is a/an
Isomerase
Lyase
Oxidoreductase
Hydrolase
Which of the following statements about the interaction of cofactors with apoenzymes is CORRECT?
No correct response
They can, but not have to be, covalently bonded to the apoenzyme.
They cannot be covalently bonded to the apoenzyme.
They are always covalently bonded to the apoenzyme.
Which DOES NOT belong to the group?
Tyrosine
Lysine
Tryptophan
Phenylalanine
Which of the following statements about the lock-and-key model for enzyme activity is INCORRECT?
The active site has a geometry identical to that of substrate.
The active site has a fixed, rigid geometry.
The active site has a geometry complementary to that of substrate.
No correct response
Cerebrosides which accounts for 7% of the brain’s dry weight and are also found in nerve synapses is an example of
Glycolipid
Sphingolipid
Glycerophospholipid
Sphingoglycolipid
The presence of an unsaturation in a fatty acid __________the melting point of its triglyceride.
Either increase or decrease
Does not affect
Decreases
Increases
Predict the function of cellulase.
It catalyzes the hydrolysis of cellulose.
It catalyzes the phosphorylation of cellulose.
It catalyzes the chain elongation in cellulose.
It catalyzes the transfer of an amino group to cellulose.
It acts as the energy reserve storage form of carbohydrates in humans.
Amylose
Glycogen
Triacylglycerol
Amylopectin
Which of the following statements is TRUE about carbohydrates?
The D- and L-enantiomers of carbohydrates have identical chemical properties.
Carbohydrates are water-soluble
Carbohydrates are synthesized by plants through the process of photosynthesis.
Carbohydrates are the most abundant bioorganic molecule in the human body.
Inhibition of the enzyme transpeptidase is the mode of action for
All antibiotics
Sulfa drugs
No correct response
Penicillin
The presence of which of the following is a defining characteristic of a multimeric protein?
At least three polypeptide chains
At least four polypeptide chains
At least two polypeptide chains
At least 200 amino acid residues
The -OH group in the anomeric carbon of ?-D-glucose is oriented
Upward
Downward
In any direction
Horizontally
A small organic molecule that serves as a cofactor in a conjugated enzyme is called
Mineral
Vitamin
Coenzyme
Prosthetic group
The acidic polysaccharide that has an anticoagulant property.
Heparin
Glucuronic acid
Hyaluronic acid
None of the choices is correct
When forming the peptide bond, the carboxylic group of one amino acid bonds with _____of the other amino acid.
Either amino or carboxylic group
Amino group
Side chain
Carboxylic group
It is the process wherein the ester linkage of a triglyceride splits into glycerol and 3 fatty acid molecules.
Esterification
Dehydration
Hydrolysis
Saponification
Which of the following is NOT found on a cell membrane?
Glycolipids
Cholesterol
Triacylglycerol
Phospholipids
All of the following are functions of proteins EXCEPT
For transport of materials
All the given choices are correct
As hormones
As enzymes
All of the following describes a conjugated enzyme EXCEPT
An enzyme that contains only protein
AN enzyme that contains a carbohydrate portion.
A holoenzyme.
An enzyme that contains a vitamin as part of its structure.
The enantiomeric form of amino acids beneficial to humans.
L-
D-
Both L- and D-
A conjugated enzyme is biologically active when it contains
Both apoenzyme and cofactor
No correct response
A cofactor
An apoenzyme
Which of the following statements is TRUE?
In general, fibrous proteins are water insoluble while globular proteins are water soluble.
Enzymes, in general, have spherical shape.
There are more globular proteins than fibrous proteins.
All of the given statements are correct.
The smallest/simplest carbohydrate contains ___ carbon atoms.
4
3
1
2
When a protein undergoes denaturation, only its _____________ remains unchanged.
Tertiary
Primary
quaternary
Secondary
Rancidity in oils is caused by a/an __________ reaction.
Oxidation
Condensation
Hydrogenation
Esterification
Which of the following is NOT TRUE about zwitterions?
They give rise to the molecular structure of amino acids
It results to a high melting point of amino acids.
Zwitterions are formed from the internal acid-base reaction between the amino and carboxylic groups of amino acids.
They explain the solubility of amino acids in water.
A metabolic reaction involves a transfer of an amino group from one molecule to another. The enzyme that catalyzes this type of reaction is a / an
Transferase
Ligase
Lyase
Oxidoreductase
The highest organizational structure of a multimeric (several polypeptide chains) protein.
Quaternary
Secondary
Primary
Tertiary
All of the following are water-soluble vitamins EXCEPT
Niacin
Riboflavin
Vitamin C
Vitamin A
When forming the peptide bond, the carboxylic group of one amino acid bonds with the _____of the other amino acid.
Amino group
Side chain
Carboxylic group
Either amino or carboxylic group
This type of transport across the cell membrane spends energy since it will involve passage across a concentration gradient
Passive transport
Facilitated transport
Active transport
None of the choices is correct
Which of the following is NOT TRUE about zwitterions?
They explain the solubility behavior of amino acids in water.
Zwitterions are formed from the internal acid-base reaction between the amino and carboxylic groups of amino acids.
It results to a high melting point of amino acids.
They give rise to the molecular structure of amino acids.
It is a protein that has one or more non-amino acid entities present in its structure in addition to one or more peptide chains.
Conjugated protein
Monomeric
Complex protein
Multimeric
It is a structural polysaccharide found in plant cell wall made of repeating glucose units connected via ?-1,4- glycosidic linkages.
Cellulose
Amylose
Starch
Amylopectin
The tripeptide made of arg-ala-asn is called
Alanylarginylasparagine
Arginylalanylasparagine
Argininealanylasparagine
Argininealanineasparagine
A molecule that inhibits an enzyme by being identical to the substrate in shape and charge distribution is called a
Negative regulator
Competitive inhibitor
Noncompetitive inhibitor
Positive regulator
Ll of the following has an enantiomer EXCEPT
valine
Lysine
Glycine
glutamic acid
The coenzyme involved in redox reactions and contains riboflavin in its structure.
Coenzyme A
ACP
NAD+
FAD
Which of the following is a CHIRAL compound?
C6H12O6
CH2OH
CH3Cl
C2H6
In terms of biological function, albumin and globulin are example of
Storage protein
Nutrient proteins
Buffer proteins
Fluid-balance proteins
The major structural component of the cell membrane
Glycolipid
Cholesterol
Phospholipids
Phosphatidylcholine
T is the pH value at which the net charge of a protein is equal to zero.
None of the choices is correct
Isoelectric pH
Equilibrium point
Isoelectric point
All of the following are functions of cholesterol EXCEPT
It serves as a protective coating.
It provides rigidity to the cell membrane.
Precursor for bile salts.
Precursor for steroid hormones.
When a monosaccharide reacts with Benedicts reagent, a/an ____________ is formed.
Alditol
Amino alcohol
Aldonic acid
Uronic acid
An enzyme active site is the location in an enzyme where substrate molecules
No correct response
Are changed to products
React to form products
Are produced
In which of the following solvents will lipids readily dissolve?
Chloroform
water
Ethanol
Isopropyl alcohol
Which of the following likely contains unsaturated fatty acids?
Lard
Beef tallow
Sunflower oil
Butter
Which of the following interactions are NOT found in the quaternary structure of proteins?
Electrostatic interaction
H-bond
Covalent disulfide bond
Hydrophobic interaction
Which of the following is NOT a function of lipids?
For energy storage
As chemical messengers
Supplies carbon atoms for DNA and RNA synthesis
As structural component of the cell membrane
A protein is made up of at least 40 amino acid residues link by _____ bonds.
Glycosidic
Ether
Ester
Amide
Which of the following is a nonstandard amino acid?
4-hydroxyproline
Methionine
Arginine
Aspartic acid
The highest organizational structure of a multimeric (several polypeptide chains) protein.
Tertiary
Primary
Quaternary
Secondary
A nonapeptide that acts as an antidiuretic hormone
Insulin
Vasopressin
None of the choices is correct
Oxytocin
A protein is made up of at least 50 amino acid residues link by _____ bonds.
ester
Ether
Amide
Glycosidic
The hormones that regulate the concentration of sodium and potassium ions in the body.
Glucocorticoid
Mineralocorticoid
Aldosterone
Cortisol
It is a tri-hydroxy alcohol found as a backbone in triglycerides.
Propanoic acid
Glycerol
Ethanol
Lauric acid
Gamma globulin, mucin, and interferon are examples of
Glycoproteins
Nucleoproteins
Lipoproteins
Hemoproteins
Which of the following statements is TRUE about enzyme activity?
Enzyme activity refers to the number of products formed per minute per molecule of an enzyme.
Enzyme activity constantly increases with increasing temperature.
Enzyme activity reaches optimum for a given pH, temperature, and enzyme & substrate concentration.
Enzyme activity can only be regulated by removing them from the reaction mixture.
It is an amino sugar found in many polysaccharides like in cartilage and chitin.
D-galactosamine
N-acetyl-D-glucosamine
D-glucosamine
D-mannosamine
Which of the following best describes lipids?
Lipids in the form of triglycerides are made of fatty acids with odd-numbered carbon atoms.
Lipids are naturally occurring organic compounds which are insoluble in water but are soluble in nonpolar solvents
Lipids are less efficient in storing energy compared to carbohydrates.
Lipids are the primary source of energy by the human body.
Which of the following will have an enantiomer?
Galactose
All the given choices will form enantiomers
Fructose
Ribose
Chain-elongation reactions would be catalyzed by a/an
Ligase
Lyase
Transferase
Hydrolase
It is the most abundant of all proteins in humans and is a major structural material in tendons, ligaments, blood vessels, and skin.
Collagen
Keratin
No correct response
Hemoglobin
Which of the following is NOT TRUE about catalysts?
They can be inorganic or biological catalysts.
They are used up in a reaction.
Their catalytic activity can be regulated.
They provide an alternative pathway for a chemical reaction with lower activation energy.
Vitamin C is important in
Collagen synthesis
Maintaining healthy epithelial tissues
recharging spent ferrous ions
All the choices given are correct
A double bond was introduced into the structure of a compound after a metabolic reaction without involving oxidation. The enzyme involved is like a
Hydrolase
Ligase
Lyase
Transferase
Which of the following is a basic compound?
Ethanolamine
Acetaldehyde
Acetone
Ethane
When a protein undergoes denaturation, only its _____________ remains unchanged.
Primary
Secondary
Tertiary
Quaternary
Which of the following statements about enzymes is FALSE?
All enzymes are made up of proteins.
Enzymes can have more than one binding site.
Enzymes are multimeric proteins.
Enzyme denaturation can occur by changing the pH of its environment.
The _____ transports the cholesterol synthesized by the liver to the other organs.
HDL
LDL
VLDL
None of the choices is correct
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