Acidic Properties of Carboxyl Groups
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Questions and Answers

A carboxyl group is deprotonated when it receives a hydrogen ion.

False

Amino acids have a three-letter abbreviation.

True

The structure of R influences the solubility of an amino acid in non-polar solvents.

False

Amino acids are soluble in non-polar solvents due to their ionic character.

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

The COO- group is a feature of amino acids.

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

A carboxyl group is basic when it receives a hydrogen ion.

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

Amino acids have only one type of abbreviation.

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

The R group of an amino acid influences its solubility.

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

Non-polar amino acids have hydrocarbon chains.

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

Polar amino acids are soluble in water.

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

Aromatic amino acids are bulky and have a negative charge.

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

Proline is an example of a polar amino acid.

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

Non-polar amino acids are usually found in the kinks of proteins.

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

Amino acids with an R-group containing sulfur are always charged.

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

Hydrophobic amino acids are capable of forming hydrogen bonds.

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

Hydrophilic amino acids are insoluble in water.

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

All non-polar amino acids have aliphatic R-groups.

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

Polar amino acids are always hydrophilic.

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

Glycine has a polar R-group.

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

Proline is likely to be found in kinks of a protein structure.

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

The pH of a solution is equal to 2.

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

The pH of a solution is directly proportional to the hydrogen ion concentration.

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

Cysteine's R-group is a hydrocarbon.

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

The R-group of methionine is easily polar.

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

A solution with a pH of 2 is basic.

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

Serine and threonine have similar R-groups.

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

The pH of a solution can be calculated as the square of the hydrogen ion concentration.

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

A solution with a pH of 11 is neutral.

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

Valine's R-group is small and non-polar.

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

Alanine is a polar amino acid.

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

The pH of a solution is a linear function of the hydrogen ion concentration.

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

A solution with a pH of 2 has a higher hydrogen ion concentration than a solution with a pH of 11.

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

Two cysteine molecules can form a disulfide bond.

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

The pH of a solution is always a whole number.

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

Isoleucine has a large R-group.

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

Phenylalanine's R-group contains oxygen.

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

The pH of a solution can be calculated using the formula pH = log[H+]

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

Weak acids and weak bases dissociate completely in water

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

The carboxyl group (-COOH) is basic

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

The pK1 of glycine is 9.6

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

The amino group (-NH3+) is acidic

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

At pH < 2.2, the carboxyl group (-COOH) is fully deprotonated

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

The reaction between an acid and its conjugate base is reversible

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

The pKR of an acid is equal to the pH at which the acid is fully dissociated

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

At pH > 9.4, the amino group (-NH3+) is fully protonated

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

The pH of a solution can be calculated using the formula pH = [OH-]

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

Study Notes

Amino Acids

  • Carboxyl group is deprotonated, making it acidic, and receives an H+ to become basic
  • Amino acids are soluble in polar solvents due to their ionic character, exemplified by the COO- and +NH3 groups
  • Solubility is influenced by the structure of the R group

Types of Amino Acids

  • Non-Polar Amino Acids: have hydrocarbon chains, are hydrophobic, neutral, and aliphatic
  • Polar Amino Acids: dissolve in water, are hydrophilic, neutral, and form H-Bonds
  • Aromatic Amino Acids: contain oxygen, are bulky, and have polarity dependent on the R group

Characteristics of Amino Acids

  • Some amino acids are found inside the protein, usually in the kinks of the protein

  • The R group has a charge, which affects solubility

  • Hydrogen bonds are not formed when the R group has no charge### Amino Acids

  • There are 20 standard amino acids, each with a unique R-group

  • Glycine (Gly) and Alanine (Ala) have small R-groups

  • Serine (Ser) and Threonine (Thr) have R-groups with a hydroxyl (-OH) group

  • Cysteine (Cys) has an R-group with a sulfur atom, which can form a disulfide bridge with another Cysteine

  • Tyrosine (Tyr) and Tryptophan (Trp) have large, rigid R-groups

  • Proline (Pro) has a unique, rigid structure that can cause kinks in protein chains

  • Valine (Val) and Isoleucine (Ile) have non-polar, hydrophobic R-groups

  • Asparagine (Asn) and Glutamine (Gln) have R-groups with an amide group

  • Methionine (Met) has a sulfide group in its R-group, making it easily soluble in water

  • Leucine (Leu) has a non-polar, hydrophobic R-group

Polarity of Amino Acids

  • Amino acids can be classified as polar or non-polar based on their R-group
  • Polar amino acids have R-groups with a hydroxyl (-OH) or amide group
  • Non-polar amino acids have R-groups with hydrocarbon chains or sulfur atoms
  • Glycine (Gly) and Serine (Ser) are polar amino acids
  • Alanine (Ala) and Valine (Val) are non-polar amino acids
  • Proline (Pro) is a non-polar amino acid, but its rigid structure makes it unique

Protein Structure

  • Disulfide bridges can form between two Cysteine (Cys) residues, stabilizing protein structure

  • Hydrogen bonds and weak interactions between amino acids help stabilize protein structure

  • Proline (Pro) can cause kinks in protein chains due to its rigid structure### pH Scale and Acid-Base Properties

  • pH is a measure of the concentration of hydrogen ions (H+) in a solution, calculated as pH = -log[H+].

  • pH scale ranges from 0 to 14, with a pH below 7 being acidic, pH 7 being neutral, and pH above 7 being basic.

Weak Acids and Bases

  • A weak acid is a molecule that partly dissociates in water, releasing H+ ions.
  • Weak acids have a higher pKa (acid dissociation constant) than strong acids, indicating a lower tendency to donate a proton (H+).
  • A weak base is a molecule that accepts H+ ions to form a conjugate acid.

Acid-Base Properties of Amino Acids

  • Amino acids have both an acidic carboxyl (-COOH) and a basic amino (-NH2) group.
  • The carboxyl group is protonated (acidic) at low pH and deprotonated (basic) at high pH.
  • The amino group is deprotonated (basic) at low pH and protonated (acidic) at high pH.

Titration of Glycine

  • Glycine, an amino acid, has two pKa values: pK1 (COOH) = 2.34 and pK2 (NH3+) = 9.6.
  • At pH < 2.34, glycine is fully protonated (acidic).
  • At pH > 9.6, glycine is fully deprotonated (basic).
  • The zwitterion form of glycine, where the carboxyl group is deprotonated and the amino group is protonated, is most prevalent at pH around 6-7.

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Description

This quiz explores the acidic properties of carboxyl groups, including their deprotonation and acidic behaviors. Test your knowledge of carboxyl groups and their chemical properties.

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