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Bio Mol prelims > Chapter 3 > Flashcards

Chapter 3 Flashcards

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1
Q

Derived from the Greek word ______ meaning “first” to indicate the central
roles that proteins play in living organisms

A

proteios

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2
Q

it is the indispensable agents of biological function

A

Proteins

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3
Q

They are the building blocks of proteins.

A

amino acids

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4
Q

are the biological catalysts

A

Enzymes

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5
Q

Which of the following best describes the reason why proteins are considered central to biological function?

A. Proteins are the most abundant macromolecules in living organisms.

B. Proteins serve as the primary energy source for cellular activities.

C. Proteins are the indispensable agents of biological function, formed from amino acids with diverse structures and functions.

D. Proteins are the simplest macromolecules in terms of chemical composition.

A

C. Proteins are the indispensable agents of biological function, formed from amino acids with diverse structures and functions.

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5
Q

The stunning diversity of the thousands of proteins found in nature arises from
the intrinsic properties of only

A

20 commonly occurring amino acids.

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6
Q

Defense proteins include _______
(also called immunoglobulins) which are
specific protein molecules produced by
specialized cells of the immune system in
response to foreign antigens

A

antibodies

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7
Q

Which of the following properties of amino acids contributes to their ability to form proteins?

A. Their ability to form hydrogen bonds with lipids.

B. Their intrinsic chirality, which leads to non-superimposable mirror images.

C. Their capacity to bind to nucleic acids.

D. Their ability to catalyze chemical reactions independently.

A

B. Their intrinsic chirality, which leads to non-superimposable mirror images.

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7
Q

The diversity of proteins in nature arises primarily from which of the following features of amino acids?

A. The ability to form covalent bonds with DNA.

B. The unique acid-base properties of peptide bonds.

C. The varied structure and chemical functionality of amino acid side chains.

D. The ability to undergo phosphorylation.

A

C. The varied structure and chemical functionality of amino acid side chains.

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8
Q

Which of the following statements about the role of amino acids in proteins is correct?

A. Only acidic amino acids are involved in protein formation.

B. The ability to polymerize is unique to amino acids and is essential for protein structure.

C. All amino acids have identical side chains that contribute to protein function.

D. The chirality of amino acids is irrelevant to their role in proteins.

A

B. The ability to polymerize is unique to amino acids and is essential for protein structure.

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8
Q

What role do enzymes play in biological reactions?

A. They provide the energy needed to drive chemical reactions.

B. They lower the activation energy required for reactions, thereby speeding up the process.

C. They act as substrates in metabolic pathways.

D. They prevent the denaturation of proteins.

A

B. They lower the activation energy required for reactions, thereby speeding up the process.

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9
Q

The Greek word ‘proteios’ is associated with proteins because:

A. Proteins were the first macromolecules discovered.

B. Proteins play a central and fundamental role in biological processes.

C. Proteins are the largest molecules in living organisms.

D. Proteins were the first catalysts identified in living systems.

A

B. Proteins play a central and fundamental role in biological processes.

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9
Q

How do defense proteins, such as antibodies, function in the immune response?

A. They produce toxins that directly kill pathogens.

B. They bind to antigens, marking them for destruction or removal from the body.

C. They prevent the entry of pathogens into cells by blocking receptor sites.

D. They stimulate the production of red blood cells to increase oxygen supply.

A

B. They bind to antigens, marking them for destruction or removal from the body.

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10
Q

it carries
materials from one place to
another in the body.

A

Transport proteins

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11
Q

it transports iron from the liver
to the bone marrow, where it
is used to synthesize the
heme group for hemoglobin.

A

transferrin

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12
Q

Transferrin is synthesized and
secreted into serum mostly
by the ?

A

liver

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13
Q

The proteins ________and
_______are responsible for
transport and storage of oxygen
in higher organisms, respectively

A

hemoglobin, myoglobin

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14
Q

What is the primary function of transport proteins in the body?

A. They act as enzymes to catalyze chemical reactions.

B. They store genetic information for cellular processes.

C. They carry materials from one place to another within the body.

D. They produce antibodies to fight infections.

A

C. They carry materials from one place to another within the body.

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15
Q

Which of the following statements accurately describes the function of transferrin in the body?

A. Transferrin stores oxygen in muscle tissues.

B. Transferrin transports iron from the liver to the bone marrow for hemoglobin synthesis.

C. Transferrin synthesizes heme groups directly from iron.

D. Transferrin catalyzes the reduction of iron in the bloodstream.

A

B. Transferrin transports iron from the liver to the bone marrow for hemoglobin synthesis.

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16
Q

Why is it important for iron to be bound by transferrin during transport in the body?

A. Free iron is highly reactive and can damage vascular, cellular, and subcellular structures.

B. Free iron is inert and needs transferrin to become biologically active.

C. Transferrin is the only protein capable of transporting iron to all body tissues.

D. Iron cannot be absorbed by cells without being bound to transferrin.

A

B. Free iron is inert and needs transferrin to become biologically active.

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17
Q

How does the body ensure the safe transport of iron after it is absorbed?

A. By immediately storing iron in the liver until needed.

B. By binding iron to transferrin, which safely transports it through the bloodstream.

C. By converting iron into a less reactive form before transport.

D. By encapsulating iron in lipoproteins for transport.

A

B ) By binding iron to transferrin, which safely transports it through the bloodstream.

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18
Q

What role does pH play in the release of iron from transferrin?

A. An increase in pH triggers the release of iron from transferrin.

B. A decrease in pH induces a conformational change in transferrin, leading to the release of iron.

C. A constant pH level is required for iron to remain bound to transferrin.

D. pH has no effect on the interaction between iron and transferrin.

A

B. A decrease in pH induces a conformational change in transferrin, leading to the release of iron.

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19
Q

Which of the following proteins is responsible for oxygen transport and storage in higher organisms?

A. Transferrin and ferritin

B. Albumin and transferrin

C. Hemoglobin and myoglobin

D. Ferritin and hemoglobin

A

C. Hemoglobin and myoglobin

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20
Q

Which organ primarily synthesizes and secretes transferrin into the bloodstream?

A. Bone marrow

B. Kidney

C. Liver

D. Spleen

A

C. Liver

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21
Q

What is the primary regulatory factor for the synthesis of transferrin?

A. Oxygen levels in the blood

B. Iron levels in the body

C. The presence of heme groups

D. pH levels in the liver

A

B. Iron levels in the body

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22
Q

controls many aspects of cell function,
including metabolism and reproduction.

A

Regulatory proteins

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23
Q

Many of the hormones that regulate
body function, such as ______ and
_______, are proteins.

A

insulin, glucagon

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24
Q

Which of the following hormones are examples of regulatory proteins that help regulate body function?

A. Keratin and collagen

B. Hemoglobin and myoglobin

C. Insulin and glucagon

D. Ferritin and transferrin

A

C. Insulin and glucagon

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24
Q

it provides
mechanical support to large animals
and provide them with their outer
coverings

A

Structural proteins

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24
Q

Our hair and fingernails are largely
composed of the protein _______

A

keratin.

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24
Q

What is the primary function of structural proteins in large animals?

A. To catalyze chemical reactions within cells.

B. To regulate the body’s metabolism and reproduction.

C. To provide mechanical support and contribute to the outer coverings.

D. To transport oxygen and nutrients throughout the body.

A

C. To provide mechanical support and contribute to the outer coverings.

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25
Q

Which protein is primarily responsible for the composition of hair and fingernails?

A. Collagen

B. Elastin

C. Keratin

D. Myosin

A

C. Keratin

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25
Q

Structural proteins play a crucial role in supporting which of the following tissues or structures in the human body?

A. Blood plasma

B. Tendons, bones, and skin

C. Digestive enzymes

D. Nervous system

A

B. Tendons, bones, and skin

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26
Q

Which of the following best describes the function of regulatory proteins in the body?

A. They provide energy for cellular processes.

B. They control various aspects of cell function, including metabolism and reproduction.

C. They are responsible for the mechanical support and structure of cells.

D. They store nutrients and waste products.

A

B. They control various aspects of cell function, including metabolism and reproduction.

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26
Q

How do regulatory proteins like hormones contribute to maintaining homeostasis in the body?

A. By storing glucose for energy use during fasting.

B. By regulating vital conditions such as body temperature, blood pH, and blood glucose levels.

C. By providing structural support to tissues and organs.

D. By acting as enzymes to catalyze metabolic reaction

A

B. By regulating vital conditions such as body temperature, blood pH, and blood glucose levels.

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27
Q

Which of the following best describes the role of movement proteins in the human body?

A. They store nutrients for later use.

B. They are involved in the contraction and expansion of muscles.

C. They regulate blood glucose levels.

D. They provide structural support to bones and tendons.

A

B. They are involved in the contraction and expansion of muscles.

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27
Q

What proteins are primarily responsible for muscle contraction and expansion?

A. Hemoglobin and myosin

B. Actin and myosin

C. Collagen and elastin

D. Albumin and casein

A

B. Actin and myosin

27
Q

Why are structural proteins essential for the existence of large, multicellular organisms?

A. They provide the energy needed for cellular functions.

B. They regulate body temperature and blood pH.

C. They offer mechanical strength and support to various tissues, allowing for complex body structures.

D. They transport essential molecules like oxygen and nutrients.

A

C. They offer mechanical strength and support to various tissues, allowing for complex body structures.

27
Q

it serves as source of amino acids for embryos or infants

A

Nutrient proteins

28
Q

Which of the following conditions would most likely be directly affected by a malfunction in regulatory proteins like insulin?

A. Loss of hair and weakening of nails

B. Inability to properly regulate blood glucose levels

C. Reduced strength in tendons and ligaments

D. Impaired oxygen transport in the bloodstream

A

B. Inability to properly regulate blood glucose levels

29
Q

_________ and ______ in milk are examples of nutrient storage proteins.

A

Egg albumen ,casein

30
Q

Which of the following is an example of a movement protein enabling cellular movement?

A. Sperm cells swimming due to flagella composed of proteins

B. Red blood cells transporting oxygen

C. The immune response facilitated by antibodies

D. Nutrient storage in seeds and eggs

A

A. Sperm cells swimming due to flagella composed of proteins

31
Q

Which statement about amino acids is accurate based on their structure and occurrence in nature?

A. All naturally occurring amino acids are β-amino acids.

B. Only one of the 20 common amino acids lacks a chiral carbon.

C. All 20 common amino acids are synthetically produced.

D. None of the 20 common amino acids are stereoisomers.

A

B. Only one of the 20 common amino acids lacks a chiral carbon.

31
Q

Nutrient proteins like egg albumen and casein primarily serve which function?

A. They act as enzymes to catalyze metabolic reactions.

B. They provide amino acids to embryos or infants.

C. They regulate muscle contractions.

D. They transport nutrients across cell membranes.

A

B. They provide amino acids to embryos or infants.

32
Q

Why is glycine unique among the 20 common amino acids found in nature?

A. It is the only amino acid that is not essential for protein synthesis.

B. It is the only amino acid that contains sulfur in its structure.

C. It is the only amino acid that does not have a chiral carbon atom.

D. It is the only amino acid found exclusively in animal proteins.

A

C. It is the only amino acid that does not have a chiral carbon atom.

32
Q

Which of the following proteins is an example of a nutrient storage protein?

A. Myosin

B. Keratin

C. Casein

D. Actin

A

C. Casein

33
Q

What characteristic distinguishes α-amino acids from other types of amino acids?

A. The amine group is adjacent to the carboxylate group.

B. They all have sulfur atoms in their side chains.

C. They do not participate in protein synthesis.

D. They are not found in living organisms.

A

A. The amine group is adjacent to the carboxylate group.

33
Q

it has a high affinity for water, but is not ionic at pH

A

Polar neutral

34
Q

it has an ionized carboxyl group in their
side chains

A
  • Polar acidic
35
Q

are basic as the side chain reacts with
water to release a hydroxide anion

A

polar basic

35
Q
  1. Which of the following statements correctly distinguishes between the classes of amino acids based on their side-chain (R group) polarity?

A. Nonpolar amino acids have hydrophilic side chains, while polar neutral amino acids have hydrophobic side chains.
B. Polar basic amino acids are negatively charged due to the ionization of carboxyl groups at physiological pH.
C. Nonpolar amino acids contain hydrophobic side chains that avoid interaction with water.
D. Polar acidic amino acids release a hydroxide anion when reacting with water.

A

C. Nonpolar amino acids contain hydrophobic side chains that avoid interaction with water.

35
Q

Which of the following best explains the role of essential amino acids in human nutrition?

A. Essential amino acids are those that can be synthesized by the body in unlimited amounts.
B. Essential amino acids must be supplied in the diet because the body lacks pathways for their synthesis or the available pathways are insufficient.
C. Essential amino acids are synthesized in sufficient amounts during infancy but not adulthood.
D. All amino acids are essential for tissue growth, but essential amino acids must be supplied in higher amounts than non-essential amino acids.

A

B. Essential amino acids must be supplied in the diet because the body lacks pathways for their synthesis or the available pathways are insufficient.

35
Q

What structural characteristic of amino acids causes them to exist as zwitterions at physiological pH?

A. The presence of both a hydroxyl and an amino group on the α-carbon.
B. The ability of the carboxyl group to donate a proton, resulting in a -COO- group, and the amino group to accept a proton, forming -NH3+.
C. The side chain’s ability to ionize at pH 7, creating both positive and negative charges on the side chain.
D. The carboxyl group and the amino group both maintain neutral charges at physiological pH, resulting in an overall neutral amino acid.

A

B. The ability of the carboxyl group to donate a proton, resulting in a -COO- group, and the amino group to accept a proton, forming -NH3+.

35
Q

Which of the following amino acids would most likely be found in the interior of a protein, away from water?

A. Lysine
B. Glutamic acid
C. Leucine
D. Serine

A

C. Leucine

35
Q

Why are histidine and arginine considered semi-essential amino acids, particularly in infancy?

A. They cannot be synthesized at all during adulthood, and dietary intake is crucial throughout life.
B. They are synthesized in sufficient quantities during adulthood, but their synthesis is inadequate during infancy.
C. They are synthesized in greater quantities during infancy but not adulthood, leading to essentiality in adults.
D. They are not required for proper tissue growth during infancy but become essential during adulthood due to increased metabolic demands.

A

B. They are synthesized in sufficient quantities during adulthood, but their synthesis is inadequate during infancy.

36
Q

At physiological pH, what is the overall charge of an amino acid with a nonpolar, uncharged R group?

A. Positive
B. Negative
C. Neutral
D. Depends on the type of R group

A

C. Neutral

36
Q

Which of the following amino acids has an R group that would make it classified as polar basic?

A. Alanine
B. Aspartic acid
C. Lysine
D. Phenylalanine

A

C. Lysine

36
Q

it is the pH at which it bears no net change

A

isoelectric point

36
Q

it is a form of the amino acid is a more accurate depiction of its structure

A

zwitterionic

37
Q

A zwitterion contains two point charges but is ______ overall

A

neutral

38
Q

At which pH value would an amino acid with an isoelectric point (pI) of 5.96 be expected to have no net charge in an aqueous solution?

A. pH 4.5
B. pH 5.96
C. pH 6.5
D. pH 7.5

A

B. pH 5.96

39
Q

In an electrophoresis experiment, if an amino acid has a net negative charge, where would it migrate when an electric field is applied?

A. Toward the anode (+)
B. Toward the cathode (-)
C. Neither; it will not migrate
D. It will migrate randomly

A

A. Toward the anode (+)

40
Q

Why does an amino acid not migrate in an electric field at its isoelectric point (pI)?

A. It is completely protonated and carries a positive charge
B. It is completely deprotonated and carries a negative charge
C. It has no net charge due to the balancing of positive and negative charges
D. It is in a non-aqueous solution

A

C. It has no net charge due to the balancing of positive and negative charges

41
Q

If the pH of the solution is higher than the isoelectric point of an amino acid, what is the expected charge of the amino acid?

A. Net positive charge
B. Net negative charge
C. No net charge
D. Cannot be determined

A

B. Net negative charge

42
Q

What type of technique is used to determine the isoelectric point of an amino acid by analyzing its migration in an electric field?

A. Chromatography
B. Spectroscopy
C. Electrophoresis
D. Mass spectrometry

A

C. Electrophoresis

43
Q

At a pH value below the isoelectric point of an amino acid, what is the likely charge on the amino acid?

A. No net charge
B. Net positive charge
C. Net negative charge
D. Net neutral charge

A

B. Net positive charge

44
Q

Which of the following statements is true regarding the isoelectric point (pI) of an amino acid?

A. The pI is the pH at which the amino acid has the highest net positive charge.
B. The pI is the pH at which the amino acid has the highest net negative charge.
C. The pI is the pH at which the amino acid has no net charge.
D. The pI is the pH at which the amino acid is completely ionized.

A

C. The pI is the pH at which the amino acid has no net charge.

45
Q

In an electrophoresis experiment at pH 7.0, what will be the behavior of an amino acid with a pI of 5.96?

A. It will migrate towards the anode (+)
B. It will migrate towards the cathode (-)
C. It will not migrate
D. It will migrate randomly

A

A. It will migrate towards the anode (+)

46
Q

the net charge of an amino acid will ___ be zero at ____ pH values

A

not, all

47
Q

The Carboxlate group is ________

A

Weakly basic

48
Q

What is the purpose of saturating the electrophoresis paper or gel with buffer solution?

A. To provide a medium for the amino acids to migrate
B. To neutralize the amino acids
C. To prevent the amino acids from reacting with ninhydrin
D. To slow down the migration of the amino acids

A

A. To provide a medium for the amino acids to migrate

49
Q

In an electrophoresis experiment, a solution of an unknown amino acid is placed at the center of the paper. If the pH of the buffer solution is lower than the isoelectric point (pI) of the amino acid, which direction will the amino acid migrate?

A. Toward the anode (+)
B. Toward the cathode (-)
C. It will not migrate
D. It will migrate toward both electrodes

A

B. Toward the cathode (-)

50
Q

What is the function of ninhydrin in the electrophoresis experiment?

A. It neutralizes the amino acids.
B. It reacts with amino acids to visualize their positions.
C. It enhances the migration of amino acids.
D. It prevents the formation of peptide bonds.

A

B. It reacts with amino acids to visualize their positions.

51
Q

What type of charge does an amino acid carry when it is at a pH greater than its isoelectric point (pI)?

A. Positive charge
B. Negative charge
C. No charge
D. Both positive and negative charges

A

B. Negative charge

52
Q

During electrophoresis, where would a negatively charged amino acid migrate under an applied electric field?

A. Toward the cathode (-)
B. Toward the anode (+)
C. It would not migrate
D. It would oscillate between electrodes

A

B. Toward the anode (+)

53
Q

Which type of bond links amino acids together in proteins?

A. Ionic bond
B. Hydrogen bond
C. Peptide bond
D. Disulfide bond

A

C. Peptide bond

54
Q

If a protein is composed of L-α-amino acids, how are the amino acids linked?

A. By glycosidic bonds
B. By ester bonds
C. By amide (peptide) bonds
D. By phosphodiester bonds

A

C. By amide (peptide) bonds

54
Q

What type of reaction forms a peptide bond between two amino acids?

A. Hydrolysis reaction
B. Dehydration reaction
C. Oxidation-reduction reaction
D. Isomerization reaction

A

B. Dehydration reaction

55
Q

In an electrophoresis experiment, what happens to a protein composed of amino acids when placed in an electric field at a pH below its pI?

A. The protein will migrate toward the cathode (-)
B. The protein will migrate toward the anode (+)
C. The protein will not migrate
D. The protein will oscillate between the electrodes

A

A. The protein will migrate toward the cathode (-)

56
Q

the positively charged form (____) dominates at very low pH

A

1+

57
Q

the zwitterionic (____) form dominates at low PH

A

neutral

57
Q

the negatively charged atom (___) at intermediate pH

A

-1

58
Q

at strongly basic pH a doubly negatively charged form (___)

A

-2

58
Q

net charge +2 is a ?

A

strongly acidic pH

58
Q

an intermediate pH is a net charge of

A

1+

59
Q

net charge pH 0

A

is the basic pH

59
Q

what net charge is the strongly basic pH

A

-1

60
Q

At pH values above the pI, the amino acid is

A

negatively charged.

60
Q

At pH values below the pI, the amino acid is

A

positively charged.

61
Q
A
61
Q
A
62
Q
A

Bio Mol prelims (4 decks)

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