Biochemistry: Amino Acids and Proteins Quiz
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Questions and Answers

How many standard proteinogenic amino acids are there?

  • 20 (correct)
  • 24
  • 22
  • 18

What is the primary biochemical designation of an amino acid?

  • α-carbon (correct)
  • β-carbon
  • γ-carbon
  • R-group

Which amino acid does not possess an asymmetric carbon?

  • Valine
  • Serine
  • Alanine
  • Glycine (correct)

What configuration is typically found in natural amino acids?

<p>L configuration (D)</p> Signup and view all the answers

What term describes amino acids in ionized form at physiological pH?

<p>Zwitterion form (B)</p> Signup and view all the answers

Which type of amino acids are characterized by their ability to act as both acids and bases?

<p>Amphoteric amino acids (A)</p> Signup and view all the answers

What is the total number of essential amino acids?

<p>9 (A)</p> Signup and view all the answers

Which of the following classifications is NOT used for amino acids?

<p>Hydrophilic vs. Hydrophobic (A)</p> Signup and view all the answers

What structural changes occur during protein denaturation?

<p>Loss of secondary, tertiary, and quaternary structure (D)</p> Signup and view all the answers

Which of the following proteins is classified as a globular protein?

<p>Hemoglobin (C)</p> Signup and view all the answers

Which of the following can cause protein denaturation?

<p>High pH environments (C)</p> Signup and view all the answers

What type of protein is hemoglobin classified as based on its composition?

<p>Conjugated protein (C)</p> Signup and view all the answers

At what temperature does protein denaturation begin to occur?

<p>41°C (C)</p> Signup and view all the answers

What is the primary role of insulin?

<p>Lower blood glucose levels (C)</p> Signup and view all the answers

Which level of protein structure is characterized by hydrogen bonds?

<p>Secondary structure (D)</p> Signup and view all the answers

Which example is classified as a fibrous protein?

<p>Collagen (A)</p> Signup and view all the answers

What defines the tertiary structure of a protein?

<p>The three-dimensional folding of the protein (C)</p> Signup and view all the answers

What role do proline and glycine play in protein structure?

<p>Inducing changes in direction of the peptide chain (B)</p> Signup and view all the answers

How many amino acids does insulin consist of?

<p>51 (B)</p> Signup and view all the answers

Which statement best describes the quaternary structure of proteins?

<p>It consists of multiple subunits interacting (D)</p> Signup and view all the answers

Which is NOT a biological role of proteins?

<p>Energy production (A)</p> Signup and view all the answers

Which amino acid is known for not having an asymmetric carbon?

<p>Glycine (D)</p> Signup and view all the answers

What is the product of the decarboxylation of histidine?

<p>Histamine (B)</p> Signup and view all the answers

Which amino acid transformation is associated with increased muscle tone when absent?

<p>Aspartic acid to Asparagine (C)</p> Signup and view all the answers

Which process contributes to the formation of urea in the body?

<p>Oxidative deamination (A)</p> Signup and view all the answers

How many amino acids classify a polypeptide?

<p>10 to 100 (C)</p> Signup and view all the answers

What is NOT a biological role of amino acids?

<p>Photosynthetic (A)</p> Signup and view all the answers

Which post-translation modification involves the addition of sugar moieties to amino acids?

<p>N/O-glycosylation (A)</p> Signup and view all the answers

What is the orientation of a peptide bond?

<p>N-terminal to C-terminal (A)</p> Signup and view all the answers

Which classification of amino acids refers to their ability to be essential for human life?

<p>Essential/non-essential (A)</p> Signup and view all the answers

What characterizes polar amino acids as opposed to non-polar amino acids?

<p>They are hydrophilic and can be ionized (A)</p> Signup and view all the answers

Which side chain type is associated with amino acids that can absorb UV light?

<p>Aromatic (C)</p> Signup and view all the answers

How are amino acids classified based on their side chain structure?

<p>Side chain nature (A)</p> Signup and view all the answers

What type of amino acid possesses a side chain that contains an acid group?

<p>Polar amino acids (D)</p> Signup and view all the answers

What distinguishes non-proteinogenic amino acids from proteinogenic amino acids?

<p>They lack essential roles in protein synthesis (C)</p> Signup and view all the answers

Which of the following correctly defines a property of non-polar amino acids?

<p>They do not interact well with water (D)</p> Signup and view all the answers

Which classification system indicates the orientation of amino acids based on molecular configuration?

<p>D/L form (C)</p> Signup and view all the answers

What is a defining characteristic of a peptide bond?

<p>It is a covalent bond that connects the amino group of one amino acid to the carboxyl group of another. (C)</p> Signup and view all the answers

Which of the following correctly classifies amino acids?

<p>Amino acids can be classified by their side chains as polar, nonpolar, acidic, or basic. (A)</p> Signup and view all the answers

What distinguishes D and L forms of amino acids?

<p>The spatial arrangement of their atoms around the alpha carbon. (A)</p> Signup and view all the answers

Which of the following is NOT a function of amino acids?

<p>Providing energy through glycosidic bonds. (D)</p> Signup and view all the answers

How many proteinogenic amino acids are there?

<p>22 (D)</p> Signup and view all the answers

What are the four levels of protein structure?

<p>Primary, secondary, tertiary, and quaternary. (B)</p> Signup and view all the answers

Which of the following organic molecules is NOT classified under the category of amino acids, peptides, and proteins?

<p>Fatty acids. (C)</p> Signup and view all the answers

What is biochemistry primarily concerned with?

<p>The integration of biology and chemistry to study biomolecules. (B)</p> Signup and view all the answers

Flashcards

What is biochemistry?

Biochemistry deals with the chemical processes occurring within living organisms, studying the composition, structure, and functions of biomolecules.

How does biochemistry integrate chemistry and biology?

Biochemistry integrates chemistry and biology, exploring the structure, properties, and functions of essential biomolecules and their interactions.

What are some applications of biochemistry?

Biochemistry has broad applications across various fields, including:

  • Medicine: Understanding diseases and developing treatments.
  • Pharmaceuticals: Developing new drugs and therapies.
  • Cosmetics: Formulating skincare products and cosmetics.
  • Food industry: Developing new food products and improving food processing.
  • Agriculture: Understanding plant metabolism and improving crop yields.
  • Environmental science: Studying environmental pollution and its impact on organisms.

What does structural biochemistry focus on?

Structural biochemistry focuses on determining the three-dimensional structures of biomolecules, like proteins and DNA.

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What is the focus of metabolic biochemistry?

Metabolic biochemistry investigates the chemical reactions that occur within an organism, such as energy production, metabolism, and biosynthesis.

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What is the application of clinical biochemistry?

Clinical biochemistry applies biochemical principles to medical diagnosis, disease monitoring, and treatment, often analyzing blood and urine samples.

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What is the focus of analytical biochemistry?

Analytical biochemistry develops and uses techniques to identify, quantify, and characterize biomolecules, often employing various methods like chromatography and spectroscopy.

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What are inorganic biochemical molecules?

Inorganic biochemical molecules are essential for life, acting as structural components, catalysts, and regulators of biological processes.

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Proline's exception

Proline is unique because it has a ring structure that includes its amino group, making it inflexible and disrupting the typical alpha-helix formation in proteins.

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Glycine's exception

Glycine is the smallest amino acid, lacking a chiral center and making it unique because it doesn't have a typical asymmetric carbon atom found in most amino acids, which is essential for chirality.

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What is decarboxylation?

Decarboxylation is a chemical reaction that removes a carboxyl group (COOH) from a molecule, often involving amino acids.

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Histidine's decarboxylation product

Histidine is an amino acid that can be decarboxylated into histamine, which is a vital chemical involved in allergic reactions and inflammation.

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Glutamic acid's decarboxylation product

Glutamic acid, through decarboxylation, produces GABA (gamma-aminobutyric acid), a crucial neurotransmitter responsible for calming and regulating brain activity.

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Amidation

Amidation is a chemical reaction that adds an amide group (CONH2) to a molecule, specifically involving amino acids.

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Glutamic acid's amidation product

Glutamic acid can be converted to glutamine through amidation, which plays essential roles in muscle growth and maintaining acid-base balance in the kidneys.

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Aspartic acid's amidation product

Aspartic acid can be converted to asparagine through amidation. A lack of asparagine can lead to hyperreflexia (overactive reflexes) and weak muscle tone.

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What are amino acids?

Amino acids are the building blocks of proteins.

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Proteinogenic vs. Non-proteinogenic Amino Acids

Proteinogenic amino acids are the 20 amino acids commonly found in proteins, while non-proteinogenic amino acids are not typically incorporated into proteins.

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Standard vs. Non-Standard Amino Acids

Standard amino acids are the 20 most common ones found in proteins, while non-standard amino acids are less frequent.

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Essential vs. Non-Essential Amino Acids

Essential amino acids cannot be synthesized by the body and must be obtained from the diet, while non-essential amino acids can be produced.

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D vs. L Forms of Amino Acids

The D and L forms refer to the stereoisomers of amino acids, with L-forms being the dominant ones in proteins.

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Classification by Side Chain Structure

Amino acid side chains can be classified by their chemical properties, which determine their interactions.

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Classification by Side Chain Nature

Amino acids can be classified by their side chain nature: hydrocarbon, alcohol, sulfur, acid group, basic group, amide group, or aromatic.

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Polarity of Amino Acids

Polar amino acids are hydrophilic, attracting water molecules, while non-polar amino acids are hydrophobic, repelling water.

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Elastin

A type of protein that can stretch and recoil, found in tissues like lungs, aorta, and skin.

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Hemoglobin

A protein responsible for transporting oxygen and carbon dioxide in the blood. It has a globular shape.

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Protein classification by shape

Proteins categorized by their shape, either long and fibrous or compact and globular.

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Protein denaturation

A type of protein denaturation where the protein loses its natural shape and function due to changes in temperature, pH, or other factors.

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Factors causing denaturation

Factors that can cause protein denaturation, such as high temperatures, extreme pH values, chemical solvents, and heavy metal ions.

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What is glutathione?

Glutathione is a tripeptide composed of cysteine, glutamic acid, and glycine. It acts as an antioxidant, protecting cells from damage.

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What is insulin and what does it do?

Insulin is a hormone produced by beta cells in the pancreas. Its function is to lower blood glucose levels by facilitating the uptake of glucose into cells.

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What is protein synthesis?

Protein synthesis is the process of creating proteins from genetic instructions encoded in DNA. It involves transcription and translation.

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What are some structural roles of proteins?

Proteins play crucial structural roles by providing support and shape to cells and tissues. Think of collagen, which forms the connective tissue in your skin and bones.

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What is a transport role of proteins?

Proteins can bind and transport molecules across cell membranes, such as hemoglobin, which carries oxygen in the blood.

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What is the primary structure of a protein?

The primary structure of a protein refers to the linear sequence of amino acids, linked together by peptide bonds. This sequence is determined by the genetic code.

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How is the secondary structure of a protein formed?

The secondary structure of a protein involves the folding of the polypeptide chain into regular patterns, like alpha-helices and beta-sheets, stabilized by hydrogen bonds.

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What is the tertiary structure of a protein?

The tertiary structure of a protein refers to its three-dimensional shape, which is determined by interactions between amino acids, including hydrophobic interactions, hydrogen bonds, and disulfide bridges.

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What are essential amino acids?

These amino acids cannot be synthesized by the human body and must be obtained from the diet. Examples include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

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What is an asymmetric carbon?

Amino acids have a central asymmetric carbon atom, often called a chiral carbon, connected to four different groups.

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How do amino acids behave in solution?

Amino acids are amphoteric, meaning they can act as both an acid and a base. At the normal pH of the body, they exist in a zwitterion form, which is a molecule with both a positive and negative charge.

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How are amino acids classified?

Amino acids are classified based on their side chain structure, which is the part of the molecule that gives it its unique properties. Side chains can be aliphatic, aromatic, or polar, among others.

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What is the difference between L and D amino acids?

Natural amino acids are primarily in the L configuration. This means they are left-handed isomers. The D form, the right-handed version, is less common in nature.

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How are amino acids abbreviated?

Amino acids are named using a three-letter code or a one-letter code. For example, glycine can be abbreviated as Gly or G.

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Study Notes

Amino Acids, Peptides, and Proteins

  • Amino Acids: About 500 amino acids exist naturally, organic molecules.
  • Proteinogenic Amino Acids: Are 22 in number, 20 standard and 2 non-standard.
  • Non-proteinogenic Amino Acids: Not incorporated into proteins
  • Essential Amino Acids: There are 9 essential amino acids.
  • Amino Acid Structure: Have an amino group, carboxyl group, an alpha carbon, and a side chain (R group).
  • Asymmetric Carbon: Most amino acids have a chiral center that is bonded to four different groups. Glycine is the only one that lacks an asymmetric carbon.
  • Chirality: Amino acids exhibit chirality with L and D forms. Natural amino acids are L-configured.
  • Amino Acids Classification:
    • Proteinogenic/non-proteinogenic
    • Standard/non-standard
    • Essential/non-essential
    • Polar/non-polar
    • side chain structure/ nature
    • Acid/base group

Peptide and Protein

  • Amino Acid: A single unit of an amino acid, monomer, or residue.
  • Peptides: Chains of more than 2 amino acids;
    • Oligopeptide: 2 to 10 amino acids
    • Polypeptide: 10 to 100 amino acids
  • Protein: Over 100 amino acids.
  • Peptide Bond: Connects amino acids. Formed through a dehydration reaction removing water.
  • Peptide Bond Properties:
    • N-terminal and C-terminal ends
    • Strong (partial double bond character)
    • Stable and planar structure
    • Lack of rotation

Peptide Examples

  • Glutathione (antioxidant): Cys-Glu-Gly, involved in cellular redox reactions.
  • Insulin (hormone): 51 amino acids, from pancreatic beta cells regulating blood glucose levels.

Protein Synthesis

  • Translation: Protein synthesis process using mRNA instructions.

Protein Biological Roles

  • Structural: Form building blocks of tissues and organs.
  • Metabolic and functional: Participate in various metabolic processes, including energy production and cell signaling.
  • Energetic: Supply energy to cells when needed.
  • Transport: Carry substances throughout the body.
  • Defense: Protect the body from pathogens and foreign substances.
  • Enzymatic: Act as catalysts in biochemical reactions.
  • Storage: Store nutrients for later use.

Protein Levels of Structure

  • Primary: Amino acid sequence.
  • Secondary: Hydrogen bonding (alpha helix, beta sheet).
  • Tertiary: 3D structure of a single protein.
  • Quaternary: Multiple protein subunits, their interactions.

Protein Classification

  • Shape:
    • Fibrous Example: Keratin, collagen
    • Globular Example: Hemoglobin
  • Composition:
    • Simple Example: Albumin, globulins
    • Conjugated: protein + non-protein part Example: glycoproteins, lipoproteins, nucleoproteins, metalloproteins.

Protein Denaturation

  • Loss of Structure and Function:
    • Chemical and Physical Agents cause loss of secondary, tertiary, and quaternary structure. Chemical agents: temperature, pH, solvents, and heavy metal ions. Physical agents: agitation.
  • Examples:
    • Cooking eggs, hair care, damaged protein due to fever.

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Amino acids, Peptides and Proteins - Chapter 1 - 2024-2025 PDF

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Test your knowledge of amino acids and proteins in this comprehensive quiz. Explore topics such as protein structure, denaturation, and the roles of essential amino acids. Perfect for students studying biochemistry or related fields.

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