Proteins and Amino Acids Quiz
42 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary element that distinguishes proteins from carbohydrates and lipids?

  • Carbon
  • Oxygen
  • Hydrogen
  • Nitrogen (correct)

Proteins are made up of more than 20 standard amino acids.

False (B)

What are the small units that proteins can be broken down into called?

Amino acids

The Greek word that the term 'protein' is derived from means '______'.

<p>primary</p> Signup and view all the answers

Match the following elements with their presence in proteins:

<p>C = Present in proteins N = Present in proteins S = Occasionally present in proteins I = Rarely present in proteins</p> Signup and view all the answers

How many standard amino acids can proteins be composed of?

<p>20 (D)</p> Signup and view all the answers

Who suggested the term 'proteins' to GJ Mulder?

<p>JJ Berzelius</p> Signup and view all the answers

Which of the following amino acids is classified as having a non-polar R group?

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

All amino acids with polar but uncharged R groups are hydrophobic.

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

What is the one-letter symbol for Cysteine?

<p>C</p> Signup and view all the answers

The amino acid ______________ has a positively charged R group.

<p>Lysine</p> Signup and view all the answers

Match the amino acids with their classifications:

<p>Alanine = Non-polar R group Serine = Polar but uncharged R groups Aspartic acid = Negatively charged polar R group Histidine = Positively charged polar R group</p> Signup and view all the answers

Which amino acid is commonly considered to have an ambiguous classification due to its side chain?

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

Glycine has the largest R group among amino acids.

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

Name one amino acid that is classified as negatively charged.

<p>Aspartic acid</p> Signup and view all the answers

Out of the following amino acids, ______________ is classified as a polar but uncharged R group.

<p>Asparagine</p> Signup and view all the answers

Which amino acid has both a polar side chain and an ionizable group?

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

Which amino acid has a thiol ether side chain?

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

Proline is categorized as an a-amino acid.

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

What is the formula for Tryptophan?

<p>COO- H3N+-C-H CH2 NH</p> Signup and view all the answers

Tyrosine is a derivative of ___________ with a phenolic group.

<p>phenylalanine</p> Signup and view all the answers

Match the following amino acids with their characteristics:

<p>Serine = Contains a hydroxylic group Threonine = Has a larger hydroxylic group than Serine Tyrosine = Contains a phenolic group Proline = Has a pyrrolidine ring structure</p> Signup and view all the answers

Which amino acid is known for its aromatic side chain?

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

Valine is classified as a polar amino acid.

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

Which amino acid has an amide-bearing side chain?

<p>Asparagine or Glutamine</p> Signup and view all the answers

The amino acid ___________ features a side chain that can form hydrogen bonds due to its hydroxyl group.

<p>Threonine</p> Signup and view all the answers

What distinguishes Proline from other amino acids?

<p>It features a pyrrolidine ring (A)</p> Signup and view all the answers

Which of the following amino acids is classified as a dicarboxylic amino acid?

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

All non-essential amino acids can be synthesized by the body.

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

Name two essential amino acids.

<p>Leucine and lysine</p> Signup and view all the answers

__________ amino acids can be converted into glucose via gluconeogenesis.

<p>Glucogenic</p> Signup and view all the answers

Match the type of amino acid to their classification:

<p>Lysine = Essential amino acid Aspartate = Non-essential amino acid Leucine = Essential amino acid Glutamate = Non-essential amino acid</p> Signup and view all the answers

Which amino acid carries a positive charge at physiological pH due to its protonated side chain?

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

Glutamic acid does not carry a negative charge at physiological pH.

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

What is the pK of Arginine, making it the most basic amino acid?

<p>13</p> Signup and view all the answers

Cysteine can form _______ bonds with another cysteine through oxidation.

<p>disulfide</p> Signup and view all the answers

Match the following amino acids with their corresponding formulas:

<p>Asparagine = NH2-C-CH2-C-COOH Lysine = NH2-CH2-CH2-CH2-CH2-C-COOH Cysteine = HS-CH2-CH(COOH)-NH2 Histidine = NH2-CH2-C-COOH</p> Signup and view all the answers

Which of the following amino acids contains an imidazoline ring in its side chain?

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

Histidine is fully charged at physiological pH.

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

What are the names given to aspartic acid and glutamic acid when they are ionized?

<p>Aspartate and Glutamate</p> Signup and view all the answers

The primary amino acid with a pK of ______ is Histidine.

<p>6.0</p> Signup and view all the answers

Which amino acid is known for its ability to form cystine by bonding with another cysteine?

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

Flashcards

What are proteins?

Proteins are large biomolecules composed of one or more long chains of amino acid residues. They are essential for virtually all biological processes, including catalyzing metabolic reactions, DNA replication, transporting molecules across cell membranes, and providing structural support.

What is protein hydrolysis?

The breakdown of proteins into smaller units, specifically amino acids, using water and enzymes. This process is vital for digesting proteins and releasing amino acids that can be used by the body.

What are standard amino acids?

The 20 standard amino acids commonly found in proteins. They are encoded by DNA and differ in their chemical properties, contributing to the diverse functions and structures of proteins.

How are amino acids classified?

Amino acids are categorized based on the chemical properties of their side chains (R groups), particularly their polarity and charge. This classification helps understand how amino acids interact with each other and with other molecules in a protein structure.

Signup and view all the flashcards

Why do proteins contain nitrogen?

Proteins contain nitrogen in addition to carbon, hydrogen, and oxygen. This characteristic distinguishes proteins from carbohydrates and lipids.

Signup and view all the flashcards

Are proteins polymers?

Proteins are polymers, meaning they are made up of repeating units called monomers. In the case of proteins, the monomers are amino acids.

Signup and view all the flashcards

What are the functions of proteins?

Proteins are essential for various biological functions, including enzyme catalysis, structural support, transport, signaling, and immunity. Their diverse roles are determined by the specific sequence and arrangement of amino acids within their structure.

Signup and view all the flashcards

Non-polar Amino Acids

Amino acids with side chains that are hydrophobic and tend to be buried in the interior of proteins.

Signup and view all the flashcards

Examples of Non-polar Amino Acids

Glycine, Alanine, Valine, Leucine, Isoleucine, Phenylalanine, Tryptophan, Methionine, and Proline are classified as non-polar amino acids.

Signup and view all the flashcards

Glycine's Side Chain

The side chain of glycine is a simple hydrogen atom.

Signup and view all the flashcards

Polar Amino Acids

Amino acids with side chains that are hydrophilic and tend to be on the surface of proteins.

Signup and view all the flashcards

Examples of Polar Amino Acids

Serine, Threonine, Tyrosine, Cysteine, Asparagine, Glutamine are classified as polar amino acids.

Signup and view all the flashcards

Negatively Charged Amino Acids

Aspartic acid and Glutamic acid are negatively charged amino acids.

Signup and view all the flashcards

Positively Charged Amino Acids

Lysine, Arginine, and Histidine are positively charged amino acids.

Signup and view all the flashcards

Amino Acid Classification

The three categories of amino acid classification based on side chain properties are non-polar, polar but uncharged, and charged polar.

Signup and view all the flashcards

Glucogenic amino acids

Amino acids that can be converted into glucose through gluconeogenesis.

Signup and view all the flashcards

Ketogenic amino acids

Amino acids that are broken down into acetyl-CoA or acetoacetyl-CoA, which are precursors for ketone bodies.

Signup and view all the flashcards

Glucogenic and ketogenic amino acids

Amino acids that can be converted into both glucose and ketone bodies.

Signup and view all the flashcards

Essential amino acids

Amino acids that are not produced by the body and must be obtained from the diet.

Signup and view all the flashcards

Non-essential amino acids

Amino acids that can be synthesized by the body.

Signup and view all the flashcards

Asparagine

Asparagine is an amino acid with a side chain structure containing an amide group.

Signup and view all the flashcards

Glutamine

Glutamine is an amino acid with a side chain structure containing an amide group.

Signup and view all the flashcards

Cysteine

Cysteine contains a thiol group, which can form a disulfide bond with another cysteine.

Signup and view all the flashcards

Cystine

Cystine is formed when two cysteines are linked by a disulfide bond.

Signup and view all the flashcards

Lysine

Lysine is a positively charged amino acid at physiological pH due to its terminal amino group.

Signup and view all the flashcards

Arginine

Arginine is a basic amino acid containing a guanidine group that's positively charged at physiological pH.

Signup and view all the flashcards

Histidine

Histidine contains an imidazole ring that can act as a general acid-base catalyst.

Signup and view all the flashcards

Glutamic acid

Glutamic acid is an acidic amino acid with a negatively charged carboxyl group at physiological pH.

Signup and view all the flashcards

Aspartic acid

Aspartic acid is an acidic amino acid containing a carboxyl group.

Signup and view all the flashcards

Charged Polar Amino Acids

The side chains of charged polar amino acids are either acidic or basic.

Signup and view all the flashcards

What is Alanine?

This amino acid is the simplest one with a methyl group as its R group. It's considered nonpolar and hydrophobic, contributing to protein structure and function.

Signup and view all the flashcards

What is Valine?

This amino acid has a branched side chain with two methyl groups. Like Alanine, it's nonpolar and hydrophobic.

Signup and view all the flashcards

What is Leucine?

This amino acid has a bulky side chain with two methyl groups, making it hydrophobic and contributing to protein folding.

Signup and view all the flashcards

What is Isoleucine?

This amino acid has a branched side chain with a methyl group at a different location compared to Leucine. It's also hydrophobic and affects protein folding.

Signup and view all the flashcards

What is Phenylalanine?

This amino acid has a phenyl ring as its side chain, making it aromatic and hydrophobic. It contributes to protein structure and UV absorption.

Signup and view all the flashcards

What is Methionine?

This amino acid has a thiol ether group in its side chain, making it nonpolar and hydrophobic. It plays a role in protein structure and can be modified.

Signup and view all the flashcards

What is Tryptophan?

This amino acid has a bulky indole ring as its side chain. It's aromatic and hydrophobic, contributing to protein structure and UV absorption.

Signup and view all the flashcards

What is Proline?

This amino acid has a unique pyrrolidine ring as its side chain. It's not a true a-amino acid but an a-imino acid, affecting protein structure.

Signup and view all the flashcards

What is Serine?

This amino acid has a hydroxyl group (OH) in its side chain, making it polar and hydrophilic. It can form hydrogen bonds and participates in protein interactions.

Signup and view all the flashcards

What is Threonine?

This amino acid has a hydroxyl group (OH) in its side chain but with an additional methyl group. It's also polar and hydrophilic.

Signup and view all the flashcards

Study Notes

Introduction to Amino Acids

  • Amino acids are the building blocks of proteins.
  • Proteins are large molecules with a high molecular weight, ranging from 5,000 to 25,000,000.
  • Proteins can be broken down into smaller units called amino acids by hydrolysis.
  • There are 20 standard amino acids.
  • Proteins are unbranched polymers of L-α-amino acids.
  • Amino acids are classified based on the polarity and charge of their R groups.

Protein Composition

  • Proteins contain C, H, O, and N, with nitrogen comprising approximately 16% of their molecular weight.
  • Other elements, such as I, Cu, Mn, Zn, and Fe, may also be present in small amounts.
  • In 1839, Dutch chemist G.J. Mulder identified nitrogenous compounds in milk and eggs.
  • Swedish scientist JJ Berzelius suggested the term "proteins" derived from the Greek word "proteios" meaning "primary" or "pre-eminent."

Amino Acids: Classification

  • The 20 amino acids encoded by DNA are classified based on different criteria.

  • One method is based on polarity and charge of their R groups.

  • These groupings are:

    • Non-polar
    • Polar but uncharged
    • Charged polar

  • Another classification method is based on structures of side chains. This includes:

    • Aliphatic amino acids
    • Aromatic amino acids
    • Heterocyclic amino acids
    • Dicarboxylic amino acids
    • Dibasic amino acids
    • Imino acid

  • A third way is based on catabolic fate, these are:

    • Glucogenic
    • Ketogenic
    • Both glucogenic and ketogenic

Amino Acids: Classification-Cont

  • Commonly, amino acids are classified based on their essential/non-essential nature.
    • Essential Amino Acids: Cannot be synthesized by the body and must be obtained from the diet. These include valine, leucine, isoleucine, phenylalanine, threonine, tryptophan, methionine, and lysine.
    • Nonessential Amino Acids: Can be synthesized by the body, and thus are not required in the diet. These include alanine, aspartic acid, asparagine, glycine, glutamic acid, glutamine, cysteine, proline, serine, and tyrosine.
    • Semi-essential Amino Acid: These can be made by the body by they may not synthesize enough for optimal growth. Examples of semi-essential Amino Acids are arginine and histidine.

Non-standard Amino Acids

  • These amino acids are formed from modifications of primary amino acids after protein synthesis.

  • These modifications are vital for protein function.

  • Examples include:

    • Hydroxylysine and hydroxyproline (in collagen)
    • Methylhistidine (muscle proteins)
    • Phosphoserine (casein, enzymes)
    • γ-carboxyglutamic acid (prothrombin, calcium-binding proteins)
    • Pyroglutamic acid (N-terminal in thyrotropin, several proteins)

  • Non-protein amino acids are found free in cells. Examples are ornithine and citrulline (urea cycle intermediates).

  • Taurine is an abundant human amino acid found in bile (fat digestion and absorption)

  • Other biologically important non-standard amino acids are used for functions beyond protein synthesis. Examples include chemical messengers (e.g., glycine, dopamine, GABA), local mediators of allergic reactions (e.g., histamine), and hormones (e.g., thyroxine).

  • D-amino acids are components of bacterial cell walls and antibiotics.

New Amino Acids

  • Selenocysteine is the 21st amino acid which is often part of several enzymes.
  • Pyrrolysine is the 22nd amino acid and coded for by the UAG codon in some bacteria.

Functions of Amino Acids

  • Amino acids serve various functions beyond serving as protein building blocks.
  • Some amino acids are converted into carbohydrates (e.g., glucogenic amino acids).
  • Other amino acids create specialized products; e.g.:
    • Proteins which are hormones (e.g. thyroid hormones, epinephrine, norepinephrine and melanin)
    • A vitamin, called niacin (B-vitamin) and serotonin from tryptophan
    • Creatine from glycine, arginine, and methionine.
    • Bile salts from glycine and cysteine.
  • Others have a role in the synthesis of glutathione from glycine, cysteine, and glutamate.
  • Histidine creates histamine on decarboxylation.
  • Several amino acids, including aspartate and glutamine, are precursors for pyrimidine and purine biosynthesis.
  • Methionine acts as an "active" methionine (SAM) transferring methyl groups to various molecules (transmethylation).
  • Methionine and cysteine are sulfur sources.

Properties of Amino Acids

  • Isomerism: Except glycine, all amino acids are optically active and exist in D and L forms. Naturally occurring proteins primarily contain L-forms.
  • Amphoteric Nature and Isoelectric pH: Amino acids have an amino group (-NH2) and a carboxyl group (-COOH), making them capable of acting as both acids and bases. The isoelectric point (pI) is the pH at which an amino acid has no net charge.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

BTC 312 Lecture 1: Amino Acids Structure and Properties - PDF

Description

Test your knowledge of proteins and amino acids with this engaging quiz. Explore various questions about the structure, classification, and properties of amino acids, and understand what makes proteins unique compared to carbohydrates and lipids. Perfect for students learning about biochemistry or molecular biology.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser