Biochemistry: Proteins, 1st Stage

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Questions and Answers

What is the function of defensive proteins?

To fight against diseases (correct)

To store energy

To transport molecules

To build and repair tissues

How many amino acids are repeatedly found in the structure of proteins?

100

300

20 (correct)

What are the four groups attached to the α-carbon in an amino acid?

Amino group, COOH group, Hydrogen atom, Side Chain (R) (correct)

Hydrogen atom, Oxygen atom, Nitrogen atom, Carbon atom

COOH group, Side Chain (R), Oxygen atom, Nitrogen atom

Amino group, COOH group, Hydrogen atom, Oxygen atom

What determines the primary protein structure?

The sequence of amino acids Signup and view all the answers

What is the term for the end of a polypeptide chain with a free amino group?

N-terminus Signup and view all the answers

What is an example of a dipeptide?

Aspartame Signup and view all the answers

What is the classification of amino acids based on their nutritional value?

Nutritional Signup and view all the answers

What is an essential amino acid?

An amino acid that cannot be synthesized by the body Signup and view all the answers

What is the name of the bond that links amino acids together?

Peptide bond Signup and view all the answers

What is the catalyst for tyrosine transamination?

Tyrosine transaminase enzyme Signup and view all the answers

What is the term for chains of amino acids with less than 50 amino acids?

Peptides Signup and view all the answers

What is the result of hydrogen bond formation between hydrogen of –NH group of peptide bond and the carbonyl oxygen of another peptide bond?

Secondary structure Signup and view all the answers

What is the primary structure of a protein?

The unique sequence of amino acids Signup and view all the answers

What is the term for a spiral structure resulting from hydrogen bonding between one peptide bond and the fourth one?

α-helix Signup and view all the answers

What is the term for the bond formed between the acid group (COOH) of one amino acid and the amine group (NH2) of another amino acid?

Peptide bond Signup and view all the answers

How are chains of amino acids synthesized?

Based on inherited genetic information Signup and view all the answers

What type of interactions determine the tertiary structure of a protein?

Hydrophobic interactions, hydrogen bonds, and ionic bonds Signup and view all the answers

What is the term for a type of peptide with 3 amino acids?

Tripeptide Signup and view all the answers

What is the percentage of carbon in proteins?

50-55% Signup and view all the answers

What is the function of enzymes in the living system?

To perform biological catalysis Signup and view all the answers

What is the result of complete hydrolysis of proteins with concentrated HCL?

l-α-amino acids Signup and view all the answers

What determines the sequence of amino acids in proteins?

DNA Signup and view all the answers

What is the function of hemoglobin in the living system?

To carry oxygen from lung to cells Signup and view all the answers

What is the percentage of sulfur in proteins?

0-4% Signup and view all the answers

What is the function of contractile proteins in the living system?

To permit movement of the muscles Signup and view all the answers

What is the function of protective proteins in the living system?

To destroy any foreign substance released into the living system Signup and view all the answers

What is the general structure of proteins?

Linear Polymers of amino acids Signup and view all the answers

What is the characteristic of the α-carbon in amino acids, except for glycine?

It is chiral Signup and view all the answers

Which of the following amino acids are classified as both glucogenic and ketogenic?

Isoleucine, Phenylalanine, and Tyrosine Signup and view all the answers

What is the role of the liver in amino acid metabolism?

It metabolizes amino acids and uses them for protein synthesis Signup and view all the answers

What is the precursor of thyroid hormone?

Tyrosine Signup and view all the answers

What is the result of the conversion of amino acids to glucose or fat?

Energy is released Signup and view all the answers

What is the property of amino acids that allows them to have varied structure and chemical functionality?

Novel acid-base properties Signup and view all the answers

Which of the following is NOT a metabolic fate of amino acids?

Storage in the liver Signup and view all the answers

What is the outcome of the hydration of Phenylalanine?

Tyrosine is synthesized Signup and view all the answers

Where are amino acids absorbed from the diet?

Small intestine Signup and view all the answers

What type of bonds stabilize the structure of proteins?

Disulfide bridges Signup and view all the answers

What is the result of the aggregation of two or more polypeptide subunits?

Quaternary structure Signup and view all the answers

What is the characteristic of collagen?

Fibrous protein of three polypeptides that are supercoiled Signup and view all the answers

What type of interactions hold polypeptide subunits together in quaternary structure?

Non-covalent interactions Signup and view all the answers

What is the recommended daily protein intake for an adult?

0.8 g/kg daily Signup and view all the answers

What is the effect of protein denaturing on primary structure?

Primary structure is unaffected Signup and view all the answers

What is an example of a protein with quaternary structure?

Both A and B Signup and view all the answers

What is the recommended percentage of daily kilocalories from protein?

10-30% Signup and view all the answers

What can cause protein denaturing?

All of the above Signup and view all the answers

What is the name of the bond that links amino acids together?

Peptide bond Signup and view all the answers

How many amino acids are linked by two peptide bonds in a tripeptide?

3 Signup and view all the answers

What is the term for the end of a polypeptide chain with a free carboxyl group?

C-terminus Signup and view all the answers

What is the name of a bond formed between the acid group (COOH) of one amino acid and the amine group (NH2) of another amino acid?

Peptide bond Signup and view all the answers

What is the minimum number of amino acids required to form a peptide bond?

2 Signup and view all the answers

What is the term for a polypeptide chain with less than 50 amino acids?

Peptide Signup and view all the answers

What is the result of the formation of a peptide bond between two amino acids?

Water is formed Signup and view all the answers

What is the characteristic of the peptide bond?

It is a strong covalent bond Signup and view all the answers

Which of the following is an example of a peptide?

Aspartame Signup and view all the answers

What is the characteristic of the α-carbon in amino acids, except for glycine?

It is chiral Signup and view all the answers

Which of the following amino acids are classified as both glucogenic and ketogenic?

Isoleucine, Phenylalanine, Tyrosine, and Threonine Signup and view all the answers

What is the precursor of thyroid hormone?

Tyrosine Signup and view all the answers

What is the role of the liver in amino acid metabolism?

Metabolism and synthesis of new proteins Signup and view all the answers

What is the result of the conversion of amino acids to glucose or fat?

Energy production Signup and view all the answers

What is the property of amino acids that allows them to have varied structure and chemical functionality?

Novel acid-base properties Signup and view all the answers

Where are amino acids absorbed from the diet?

Small intestine Signup and view all the answers

What is the metabolic fate of Phenylalanine?

Converted to Tyrosine Signup and view all the answers

What is the outcome of the hydration of Phenylalanine?

Formation of Tyrosine Signup and view all the answers

What is the percentage of carbon in proteins?

50-55% Signup and view all the answers

What is the type of bonds that links amino acids together?

Peptide bonds Signup and view all the answers

What is the function of enzymes?

To catalyze biological reactions Signup and view all the answers

What is the result of complete hydrolysis of proteins with concentrated HCL?

Amino acids and water Signup and view all the answers

What determines the sequence of amino acids in proteins?

DNA Signup and view all the answers

What is the general structure of proteins?

Linear polymer of amino acids Signup and view all the answers

What is the percentage of oxygen in proteins?

19-24% Signup and view all the answers

What is the function of hemoglobin?

To carry oxygen from lung to cells Signup and view all the answers

What is the percentage of sulfur in proteins?

2-4% Signup and view all the answers

What type of reaction occurs between the acid group (COOH) of one amino acid and the amine group (NH2) of another amino acid?

Condensation Signup and view all the answers

What is the result of peptide bond formation between amino acids?

A polypeptide chain is formed Signup and view all the answers

What is the process by which peptide bonds are broken?

Hydrolysis Signup and view all the answers

What type of peptides are formed by linking 2 amino acids?

Dipeptides Signup and view all the answers

What is the minimum number of amino acids required to form a protein?

50 Signup and view all the answers

What is the term for chains of amino acids with more than 10 amino acids?

Polypeptides Signup and view all the answers

What is the term for chains of amino acids with less than 50 amino acids?

Peptides Signup and view all the answers

What is the purpose of peptide bonds in protein synthesis?

To link amino acids together Signup and view all the answers

What is the result of peptide bond formation between amino acids in terms of energy?

Energy is released Signup and view all the answers

What type of bonds form between the sulfhydryl groups of cysteine monomers?

Disulfide bridges Signup and view all the answers

What is the result of the aggregation of two or more polypeptide subunits?

Quaternary structure Signup and view all the answers

What is the characteristic of collagen?

It is a fibrous protein Signup and view all the answers

What type of interactions hold polypeptide subunits together in quaternary structure?

Non-covalent interactions Signup and view all the answers

What is the recommended daily protein intake for an adult?

0.8 g/kg Signup and view all the answers

What is the effect of protein denaturing on primary structure?

It is not affected Signup and view all the answers

What is an example of a protein with quaternary structure?

Hemoglobin Signup and view all the answers

What can cause protein denaturing?

Heating, acids, bases, salts, or mechanical agitation Signup and view all the answers

What is the recommended percentage of daily kilocalories from protein?

10-30% Signup and view all the answers

Study Notes

Proteins

Proteins are the most abundant molecules in biological systems, making up 50% of cellular dry weight.
They are linear polymers of amino acids, with the sequence of amino acids determined by DNA.
Proteins have a wide range of molecular weights, from several thousand to several million.

Composition of Proteins

Five major elements: Carbon (50-55%), Hydrogen (6-7%), Oxygen (19-24%), Nitrogen (13-19%), and Sulfur (0-4%).
Small amounts of other elements: Phosphorus, Iron, Copper, Iodine, Magnesium, and Zinc.

Functions of Proteins

Enzymes: biological catalysis, vital to all living systems.
Structural proteins: hold living systems together, e.g. collagen.
Hormones: proteins that act as messengers, e.g. insulin.
Transport proteins: carry molecules and ions from one place to another, e.g. hemoglobin.
Protective proteins: destroy foreign substances, e.g. WBC.
Toxins: proteins that are poisons, e.g. snake venom.
Trans-membrane transport: Na+, K+, ATPase.
Contractile proteins: permit movement of muscles, e.g. Actin and Myosin.
Storage proteins: found in seeds and eggs.
Defensive proteins: antibodies.

Amino Acids

Building blocks of proteins, organic compounds with two functional groups: carboxyl group (-COOH) and amine group (-NH2).
300 known amino acids in nature, but only 20 are repeatedly found in the structure of proteins.
These 20 amino acids appear in the genetic code and may be positively, negatively, or zero charged.

Structure of Amino Acids

Each amino acid has four different groups attached to the α-carbon atom: amino group, COOH group, hydrogen atom, and side chain (R).

Amino Acid Sequence and Peptide Bonds

Amino acid sequence determines primary protein structure.
Amino acids are linked together by peptide bonds.
Each polypeptide starts with a free amino group (N-terminus) and ends with a free carboxyl group (C-terminus).

Classification of Amino Acids

Polarity.
Structural.
Nutritional.
Metabolic fate.
Number of Carboxylic acids.
Nutritional classification: essential amino acids (cannot be made by the body) and non-essential amino acids (made by the body).

Properties of Amino Acids

Genetic code.
Capacity to polymerize.
Novel acid-base properties.
Varied structure and chemical functionality.
Chirality (except for glycine).
Metabolic role classification.

Amino Acid Metabolism

Absorbed in the small intestine, then transported to the liver via the portal vein.
Metabolized in the liver and used for synthesis of new proteins according to body needs.
Used as an energy source by conversion to glucose or fat.

Protein Structure

Primary structure: the sequence of amino acids.
Secondary structure: results from hydrogen bond formation between amino acids.
Tertiary structure: determined by interactions among R groups and between R groups and the polypeptide backbone.
Quaternary structure: results from the aggregation of two or more polypeptide subunits.

Protein Denaturation

Any change or alteration in protein shape affecting its function.
Caused by: heating, acids, bases, salts, and mechanical agitation.
Primary structure is not affected by denaturation.

Protein Needs

Recommended protein consumption should be between 10-30% of daily kilocalories.
This means an adult should consume around 0.8 g/kg of protein daily.

Protein Structure and Function

Proteins are linear polymers of amino acids
Composition: C (50-55%), H (6-7%), O (19-24%), N (13-19%), S (0-4%), and small amounts of P, Fe, Cu, I, Mg, and Zn
Primary structure: sequence of amino acids determined by DNA
Secondary structure: results from hydrogen bond formation between hydrogen of –NH group and carbonyl oxygen of another peptide bond
- α-helix: spiral structure resulting from hydrogen bonding between one peptide bond and the fourth one
- β-sheets: another form of secondary structure in which two or more polypeptides are linked together by hydrogen bonds
Tertiary structure: determined by a variety of interactions (bond formation) among R groups and between R groups and the polypeptide backbone
Quaternary structure: results from the aggregation (combination) of two or more polypeptide subunits held together by non-covalent interactions

Amino Acids

Building blocks of proteins
Organic compounds with two functional groups: carboxyl group (-COOH) and amine group (-NH2)
300 known amino acids in nature, but only 20 are repeatedly found in protein structure
Amino acid sequence determines primary protein structure
Amino acids are linked together by peptide bonds
Each amino acid has 4 different groups attached to α-carbon: amino group, COOH group, hydrogen atom, and side chain (R)

Classification of Amino Acids

Polarity
Structural
Nutritional
Metabolic fate
Number of carboxylic acids
Essential amino acids: cannot be made by the body
Non-essential amino acids: can be made by the body

Protein Denaturation

Any change or alteration in protein shape affecting its function
Causes: heating, acids, bases, salts, mechanical agitation
Primary structure is not affected by denaturation

Protein Function

Enzymes: biological catalysis
Structural proteins: hold living systems together
Hormones: act as messengers
Transport proteins: carry molecules and ions
Protective proteins: destroy foreign substances
Toxins: poisons
Trans-membrane transport
Contractile proteins: permit movement of muscles

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Description

This lecture covers the basics of proteins, including their definition, importance, functions, structure, and amino acid metabolism. Students will be able to define, list, and classify proteins and amino acids.