Biochemistry of Amino Acids and Hormones

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Questions and Answers

Which amino acid serves as a precursor for histamine production?

Arginine

Histidine (correct)

Cysteine

Serine

Which property is unique to glycine among the amino acids?

Optical inactivity (correct)

High melting point

High solubility in ethanol

Amphoteric nature

Which amino acid is primarily associated with collagen and gelatin?

N-methyl-lysine

Desmosine

MethylHistidine

Hydroxyproline (correct)

What role do essential amino acids play in human health?

Supporting growth in infants Signup and view all the answers

What is the effect of amino acids on polarized light due to their structure?

Most amino acids are optically active except glycine Signup and view all the answers

Which property allows amino acids to react with both acids and alkalis?

Amphoteric properties Signup and view all the answers

Which amino acid is crucial in the structure of the anticoagulant protein prothrombin?

γ-Carboxyglutamate Signup and view all the answers

What is the main biochemical function of glycine in detoxification?

Contributing to the ammonia removal process Signup and view all the answers

What is the primary function of glucagon in the body?

Increases blood glucose levels Signup and view all the answers

How does oxytocin affect uterine contractions during parturition?

It initiates the contractions of the uterus Signup and view all the answers

Which of the following is true regarding vasopressin?

It decreases glomerular filtration rate (GFR) Signup and view all the answers

What role does corticotropin play in the endocrine system?

Promotes secretion of steroid hormones from the adrenal cortex Signup and view all the answers

What is the primary structure length of oxytocin?

9 amino acids Signup and view all the answers

Which statement about glutathione is correct?

It acts as a biological antioxidant. Signup and view all the answers

What is the effect of the natriuretic factor on the body?

Promotes diuresis and decreases blood pressure Signup and view all the answers

Which hormone is responsible for stimulating the release of thyrotropin?

TRH (thyrotropin releasing hormone) Signup and view all the answers

What distinguishes proteins from peptides?

Proteins contain more than 50 amino acids. Signup and view all the answers

Which level of protein structure is primarily determined by the sequence of amino acids?

Primary structure Signup and view all the answers

What type of bond is primarily responsible for stabilizing the secondary structure of proteins?

Hydrogen bonds Signup and view all the answers

In which structure do proteins gain additional complexity when formed by multiple polypeptide chains?

Quaternary structure Signup and view all the answers

What feature characterizes the primary structure of proteins?

Linear sequence of amino acids Signup and view all the answers

What is the N-terminal of a protein?

The end with a free amine group Signup and view all the answers

Which structural arrangement results in the formation of an alpha helix?

Twisting of the polypeptide backbone Signup and view all the answers

What happens to protein function if there is a change in conformation?

The protein may lose its functionality. Signup and view all the answers

Which of the following amino acids is classified as an imino acid?

Proline Signup and view all the answers

At physiological pH (7.4), which form does the amino group of an amino acid take?

Positively charged (-NH3+) Signup and view all the answers

Which classification method is NOT commonly used for amino acids?

Physical classification Signup and view all the answers

Which group of amino acids is characterized by being least soluble in water?

Nonpolar hydrophobic amino acids Signup and view all the answers

What type of isomers can amino acids with an asymmetric center at the α-carbon form?

Enantiomers Signup and view all the answers

What is the primary characteristic of glucogenic amino acids?

They can be converted into glucose. Signup and view all the answers

Which amino acid group includes cysteine due to its ability to form hydrogen bonds?

Polar hydrophilic uncharged amino acids Signup and view all the answers

Which of the following amino acids is classified as a branched-chain amino acid?

Leucine Signup and view all the answers

Which of the following amino acids are classified as polar amino acids with a negative charge on their R group?

Aspartate Signup and view all the answers

Which two amino acids are exclusively categorized as pure ketogenic amino acids?

Lysine and Leucine Signup and view all the answers

Which of the following amino acids is considered semi-essential?

Histidine Signup and view all the answers

Which amino acid functions as a neurotransmitter and is derived from glutamate?

GABA Signup and view all the answers

In terms of metabolic classification, which amino acids are categorized as both glucogenic and ketogenic?

Phenylalanine and Tyrosine Signup and view all the answers

Which amino acids are known to participate in the urea cycle?

Arginine and Ornithine Signup and view all the answers

Which of the following amino acids contains iodine and serves as a precursor to thyroid hormones?

Monoiodotyrosine Signup and view all the answers

Which two amino acids are classified as non-essential?

Serine and Glycine Signup and view all the answers

Which compound is involved in converting toxic substances into non-toxic compounds through a defense mechanism?

Glutathione Signup and view all the answers

Which statement correctly describes the action of Bradykinin?

It acts as a vasodilator and mediates pain sensation. Signup and view all the answers

What is the primary function of beta-endorphin in the body?

To provide natural pain relief and enhance mood. Signup and view all the answers

How many amino acids are contained in Kallidin?

10 Signup and view all the answers

Which of the following best describes Aspartame?

It is a dipeptide synthesized from phenylalanine and L-aspartic acid. Signup and view all the answers

What effect does Glutathione have on proteins?

It prevents oxidation of sulfhydryl groups in proteins. Signup and view all the answers

Which of the following peptides is noted for having a powerful analgesic effect?

Met-enkephalin Signup and view all the answers

What is one consequence of G6PD deficiency related to Glutathione?

Hemolytic anemia. Signup and view all the answers

Study Notes

Biochemistry I: Amino Acids, Peptides, and Protein Chemistry

The lecture covers amino acids, peptides, and protein chemistry, including their structure, properties, classification, and functions.
About 300 amino acids exist naturally, but only 20 are common in proteins.
A general structure features in α-amino acids: a central carbon atom (α-carbon) bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom (H), and a variable side chain (R group).
The side chain distinguishes each amino acid.
All amino acids are α-amino acids except proline, which is an imino acid.
L-amino acids are the types used in proteins.
At physiological pH (7.4), amino acids exist as zwitterions (with both positive and negatively charged groups).
Amino acids are classified based on factors including side chain polarity and charge, among other properties. They can be neutral, acidic, or basic.
Amino acids are also classified based on nutritional requirements (essential, non-essential, and semi-essential) and metabolic fate (ketogenic, glucogenic, both).
Special groups in amino acids include guanidinium (in arginine), benzene (in phenylalanine), phenol (in tyrosine), indole (in tryptophan), imidazole (in histidine), pyrrolidine (in proline).
Selenocysteine is the 21st amino acid, and pyrrolysine is the 22nd.
Amino acids with properties like polarity are categorized as neutral, polar (hydrophilic), acidic, and basic.
Classification based on polarity (hydrophobic, hydrophilic, and charged) helps determine their solubility in water.
Amino acids can be classified based on chemical properties of their side chains (neutral, acidic, basic).
Amino acids can be classified based on characteristics of their side chains (aliphatic, aromatic, heterocyclic, containing hydroxyl, sulfur).
Some amino acids contain a hydrocarbon side chain (e.g., glycine, alanine, valine).
Other amino acids have hydroxyl groups in their side chains (e.g., serine, threonine, tyrosine).
Some amino acids have sulfur groups in their side chains (e.g., cysteine, methionine).
Amino acids have amide side chains (e.g., asparagine, glutamine).
Amino acids can have acidic side chains (e.g., aspartic acid, glutamic acid).
Amino acids can have basic side chains (e.g., lysine, arginine, histidine).
The formation of a peptide bond involves the removal of a water molecule between the carboxyl group of one amino acid and the amino group of another, requiring energy from ATP.
Peptides are formed from a limited number of amino acids, while proteins are formed with a greater number.

Peptide Bonds and Peptides

Peptides are short chains of amino acids linked by peptide bonds.
Peptides can range from two to about 50 amino acids.
The primary structure of a peptide or protein describes the sequence of amino acids.
The primary structure affects the subsequent levels of structure.

Separation of Peptides

Peptides can be separated using techniques like electrophoresis and exchange chromatography.

Biologically Active Peptides

Many peptides function as hormones, neurotransmitters, neuromodulators, antibiotics, and other important biomolecules.
Examples of biologically active peptides include insulin, glucagon, vasopressin, oxytocin, corticotropin, TRH, glutathione, bradykinin, kallidin, endorphins, enkephalins, aspartame.

Functions of Amino Acids (Biomedical Importance)

Amino acids are involved in various biological processes, including forming the structure of proteins, hormones, neurotransmitters, and detoxification.
Essential amino acids are required in the diet, whereas most non-essential amino acids can be synthesized in the body.

Physical Properties of Amino Acids

Amino acids are typically soluble in water and organic solvents like ethanol.
Most, except glycine, exhibit optical activity due to their chiral center.
Their high melting points signify their stability.

Amphoteric Properties and Isoelectric Point

Amino acids act as both acids and bases (amphoteric).
In acidic conditions, the amino group accepts a proton, forming a positive ion.
In alkaline conditions, the carboxyl group loses a proton, forming a negative ion.
Zwitterions are formed at a specific pH, called the isoelectric point (pI), where the net charge is zero.

Protein Structure

Proteins have various levels of structural organization.
Primary structure: the linear sequence of amino acids.
Secondary structure: recurring local structures like α-helices and β-sheets.
Tertiary structure: overall three-dimensional folding of the entire polypeptide chain.
Quaternary structure: arrangement of multiple polypeptide chains (subunits) in a protein.
The final arrangement results from multiple bonds (hydrogen, hydrophobic, ionic, and disulfide).
Specific shapes and arrangements of amino acids dictate how proteins interact.
Protein shape arises from specific interactions (e.g., hydrogen bonds, disulfide bonds, hydrophobic interactions, van der Waals forces, ionic interactions).

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Test your knowledge on the key roles and properties of amino acids and hormones in human health. This quiz covers essential topics such as amino acid precursors, biochemical functions, and hormonal impacts on bodily functions. Perfect for students studying biochemistry or related fields.