Biochemistry EBA 1300: Proteins Lecture 6 Quiz

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Questions and Answers

What characterizes hydrophobic amino acids in terms of their interaction with water?

They form hydrogen bonds with water.

They are always charged.

They dissolve easily in water.

They tend to repel water. (correct)

Which of the following amino acids is considered positively charged and hydrophilic?

Cysteine

Lysine (correct)

Aspartic acid

Serine

Which type of amino acid has more carboxyl groups than amino groups?

Negatively charged amino acids (correct)

Uncharged amino acids

Essential amino acids

Hydrophobic amino acids

What is the primary role of essential amino acids in the diet?

They must be provided in the diet. Signup and view all the answers

Which of the following is NOT a characteristic of polar amino acids?

They are predominantly non-polar. Signup and view all the answers

What distinguishes semi-essential amino acids from non-essential amino acids?

Semi-essential amino acids are not needed in children. Signup and view all the answers

Which group of amino acids is characterized by containing polar functional groups but being uncharged?

Uncharged amino acids Signup and view all the answers

Which of the following amino acids would be classified as a representative of the uncharged, polar amino acids?

Threonine Signup and view all the answers

What are proteins primarily made of?

Amino acids Signup and view all the answers

Which process is required to link amino acids together to form a protein?

Dehydration synthesis Signup and view all the answers

What role do enzymes play in biological systems?

They act as catalysts and speed up chemical reactions Signup and view all the answers

Which of the following is NOT a role of proteins in the body?

Storing energy Signup and view all the answers

What are the two typical substituents on the α-carbon atom of amino acids?

Hydrogen atom and R group Signup and view all the answers

What is the basic structure of an amino acid?

An amino group, a carboxylic acid group, a hydrogen atom, and an R-group Signup and view all the answers

How are amino acids classified based on their R groups?

By their electrochemical and physiological properties Signup and view all the answers

Which classification represents amino acids that do not contain aromatic rings?

Aliphatic amino acids Signup and view all the answers

Which property is NOT characteristic of amino acids?

Low melting and boiling points Signup and view all the answers

Which statement about hormones is true?

They often act to control or regulate specific physiological processes in the body Signup and view all the answers

Which type of R group characterizes aromatic amino acids?

It contains conjugated rings Signup and view all the answers

Which elements are major components of amino acids?

Carbon, hydrogen, nitrogen, oxygen Signup and view all the answers

Which amino acid classification includes those with R-groups that have NH2 > COOH?

Basic amino acids Signup and view all the answers

What type of amino acids would you classify those with a hydroxyl group present?

Neutral aliphatic amino acids Signup and view all the answers

What classification includes amino acids characterized by the R group being not benzene?

Heterocyclic amino acids Signup and view all the answers

What property differentiates the properties of amino acids and, consequently, proteins?

The nature of the R groups Signup and view all the answers

Study Notes

Biochemistry Science: Course Code EBA 1300

Course code: EBA 1300

Fundamental Biochemistry of Proteins (Lecture 6)

Lecture topic: Fundamental biochemistry of proteins
Lecture number: 6

Topic 1: Definition of proteins
Topic 2: Importance of proteins
Topic 3: Properties of amino acids
Topic 4: Classification of amino acids

Proteins

Found in various foods (e.g., meat, seafood, cheese, nuts, legumes)
Fight infections
Help cells divide

Definition of Protein

Biological macromolecules within living bodies
Macromolecules are large
Proteins are polymers
Polymers consist of monomers

Protein Structure

Very large compared to sugar or salt molecules
Polymers composed of smaller units called amino acids
Contain carbon (C), hydrogen (H), oxygen (O), and nitrogen (N)

Building a Protein

Requires dehydration synthesis - removal of water
Amino acids linked together by peptide bonds
Proteins = polypeptides

Importance of Proteins

Found in animal and plant products (e.g., nuts, legumes)
Important large, complex molecules in the body
Essential for building muscle mass
Crucial for the structure, function, and regulation of body tissues and organs

Proteins as Enzymes

Catalysts speeding up chemical reactions
Lower activation energy
Enzyme specificity to temperature and pH

Proteins as Chemical Messengers (Hormones)

Chemical signaling molecules (often small proteins or steroids)
Secreted by endocrine cells
Regulate physiological processes, like growth, development, metabolism, and reproduction
Example: Insulin regulates blood glucose levels

Amino Acids: Building Blocks of Protein

Monomers of proteins
Contain carbon (C), hydrogen (H), nitrogen (N), and oxygen (O)
Approximately 500 known amino acids, but 20 appear in the genetic code
Can be classified in various ways

General Properties of Amino Acids

High melting and boiling points
White crystalline solid substances
Some are sweet, tasteless, or bitter
Mostly soluble in water, insoluble in organic solvents

Amino Acid Structure

Central carbon atom (α-carbon)
Amino group (-NH2)
Carboxyl group (-COOH)
Hydrogen atom
Unique side chain (R-group)

Amino Acid Classification

Differ in specific chemical properties and structure of their R-groups
Nature of the R-group determines protein properties
Classification based on R-group properties: electrochemical polarity, physiological classification, structural classification, metabolic classification

Structural Classification of Amino Acids

Aliphatic (no ring):
- Neutral
- Acidic
- Basic
Aromatic (containing a benzene ring)
Heterocyclic (R-group not benzene)

Aliphatic (Neutral)

Branched
- Valine (Val, V)
- Leucine (Leu, L)
- Isoleucine (Ile, I)
Unbranched
- Glycine (Gly, G)
- Alanine (Ala, A)
- Hydroxyl-containing
  - Serine (Ser, S)
  - Threonine (Thr, T)
- Sulfur-containing
  - Cysteine (Cys, C)
  - Methionine (Met, M)
- Aliphatic (Acidic)
Aspartic acid (Asp, D)
Glutamic acid (Glu, E)
- Amides
  - Asparagine (Asn, N)
  - Glutamine (Gln, Q)
Aliphatic (Basic)
- Lysine (Lys, K)
- Arginine (Arg, R)
- Histidine (His, H)

Aromatic Amino Acids

Phenylalanine (Phe, F)
Tyrosine (Tyr, Y)
Tryptophan (Trp, W)
- Have conjugated rings
- Characteristic smells (bananas, oranges)

Heterocyclic Amino Acids

Proline (Pro, P)
Histidine (His, H)
- R-groups not benzene rings

Electrochemical Classification

Hydrophobic (nonpolar):
- Repel aqueous environment
- Primarily in protein interiors
- Do not participate in hydrogen bonding
Hydrophilic (polar): (including charged amino acids), which interact well with water or participate in hydrogen bonding

Nonpolar or Hydrophobic Amino Acids

List of amino acids

Polar or Hydrophilic Amino Acids

Positively charged (Basic)
- Arginine, Histidine, Lysine
Negatively charged (Acidic)
- Aspartic and Glutamic Acid
Polar uncharged
- Serine, Threonine, Cysteine, Asparagine, Glutamine

Biological or Physiological Classification

Essential
- Cannot be synthesized by the body. Must be obtained from the diet.
Semi-essential
- Can be synthesized by the body, but not in sufficient amounts for adults (but enough for children) Arginine Histidine
Nonessential
- Can be synthesized by the body in sufficient amounts.

Amino Acid Three-Letter Codes

Table of amino acids and their three-letter codes

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Description

Test your knowledge on the fundamental biochemistry of proteins in the EBA 1300 course. This quiz covers the definitions, importance, properties, and classification of proteins and amino acids. Dive into the basics of protein structures and their biological significance.