Biomolecules Questions and Answers AP Inter 1st Year Botany Chapter 6

Andhra Pradesh BIEAP AP Inter 1st Year Botany Study Material 6th Lesson Biomolecules Class 11 Textbook Exercise Questions and Answers.

Biomolecules Class 11 Questions and Answers AP Inter 1st Year Botany 6th Lesson

I. Biomolecules Multiple Choice Questions (1 Mark)

Question 1.
Chemical analysis of living organisms can be done by the usage of following chemical.
(1) Ethanol
(2) Benzene
(3) Trichloro acetic acid
(4) Acetic acid
Answer:
(3) Trichloro acetic acid

Question 2.
Identify the polysaccharide which is polymer of fructose.
(1) Starch
(2) Glycogen
(3) Cellulose
(4) Inulin
Answer:
(4) Inulin

Question 3.
Identify the aromatic amino acid.
(1) Glutamic acid
(2) Tyrosine
(3) Lysine
(4) Alanine
Answer:
(2) Tyrosine

Question 4.
Palmitic acid contains how many carbons?
(1) 16
(2) 20
(3) 15
(4) 19
Answer:
(1) 16

Question 5.
Cytidylic acid is a
(1) nitrogen base
(2) nucleotide
(3) nucleoside
(4) nucleic acid
Answer:
(2) nucleotide

Question 6.
Concanavalin A is a ………..
(1) drug
(2) lectin
(3) alkaloid
(4) toxin
Answer:
(2) lectin

Question 7.
Identify the secondary metabolite.
(1) Amino acid
(2) Nucleic acids
(3) Carbohydrates
(4) Rubber
Answer:
(4) Rubber

Question 8.
Which among the following is not a pyrimidine ?
(1) Thymine
(2) Cytosine
(3) Adenine
(4) Uracil
Answer:
(3) Adenine

Question 9.
The following protein enables glucose uptake into cells.
(1) GLUT-4
(2) Collagen
(3) Antibody
(4) Trypsin
Answer:
(1) GLUT-4

Question 10.
The following structure is necessary for the many biological activities of proteins.
(1) Primary structure
(2) Secondary structure
(3) Tertiary structure
(4) Quarternary structure
Answer:
(3) Tertiary structure

Question 11.
Which among the following is not a polymer ?
(1) Polysaccharide
(2) Protein
(3) Nucleic acid
(4) Lipid
Answer:
(4) Lipid

II. Biomolecules Fill in the Blanks (1 Mark)

Question 1.
The pentose sugar in DNA is …………
Answer:
Deoxy ribose

Question 2.
Nucleic acids percentage in the total cellular mass is …………
Answer:
5-7%

Question 3.
Most abundant protein in the biosphere …………
Answer:
RUBISCO

Question 4.
The molecular weight of macromolecules is greater than ………… Daltons.
Answer:
1000

Question 5.
The amino acids in protein are linked by ………… bond.
Answer:
Peptide

Question 6.
Exo skeleton of arthropods is made up of …………
Answer:
Chitin

Question 7.
The R-group of the serine is …………
Answer:
CH₂OH

Question 8.
The micro molecule which is found in acid insoluble fraction …………
Answer:
Lipids

Question 9.
Coenzyme NAD and NADP contain ………… vitamin.
Answer:
Niacin

Question 10.
Most of the enzymes get damaged/denatured above ………… degrees temperature.
Answer:
40

III. Biomolecules One Word Answer Questions (1 Mark)

Question 1.
Name the pyrimidine which is absent in the RNA.
Answer:
Thymine

Question 2.
Name the acid which is formed in our skeletal muscle, under anaerobic conditions.
Answer:
Lactic acid

Question 3.
In the presence of carbonic anhydrase how many H₂CO₃ molecules can be formed per Second.
Answer:
6 lakhs

Question 4.
What is the metal ion cofactor for the proteolytic enzyme carboxypeptidase?
Answer:
Zn

Question 5.
Name the non-protein constituent of the enzyme.
Answer:
Cofactor

Question 6.
What is the most abundant protein in the animal world ?
Answer:
Collagen

Question 7.
Among the starch and cellulose which one holds iodine and gives blue colour ?
Answer:
Starch

Question 8.
Nucleic acids with catalytic power are known as ?
Answer:
Ribozyme

Question 9.
Name the first and last amino acids of a polypeptide chain.
Answer:
N-terminal and C- terminal amino acids.

Question 10.
Enzymes are categorized into how many classes ?
Answer:
6

IV. Biomolecules Very Short Answer Questions (2 Marks)

Question 1.
Give one example for each of amino acids, sugars, nucleotides and fatty acids.
Answer:

• Amino acids : Alanine, Glycine, Serine
• Sugars : Glucose, Ribose, Deoxyribose
• Nucleotide : Adenylic acid, Thymidylic acid, Guanylic acid, Uridylic acid, Cytidylic acid
• Fatty acid : Palmitic acid, Arachidonic acid

Question 2.
Explain the zwitterionic form of an amino acid.
Answer:

• It is a form where the amino group (- NH₂ ) is positively charged and the carboxyl group (- COOH ) is negatively charged, making the molecule neutral overall. This occurs in aqueous solutions.
• This form of amino acid exists under neutral conditions.

Question 3.
Glycine and alanine are different with respect to one substituent on the alpha carbon. What are the other common substituent groups ?’
Answer:
Glycine and alanine differ in their R group (glycine has hydrogen, alanine has a methyl group). The other common substituent groups on the alpha carbon are : Amino group (- NH₂), Carboxyl group (- COOH ), Hydrogen atom (H).

Question 4.
Starch, cellulose, glycogen, chitin are polysaccharides found among the following.
Choose the one appropriate against each.
a. Cotton fiber
b. Exo skeleton of cockroach
c. Liver
d. Peeled potato
Answer:
a. Cotton fiber – Cellulose
b. Exoskeleton of cockroach – Chitin
c. Liver – Glycogen
d. Peeled potato – Starch

Question 5.
What are primary, secondary metabolites ? Give examples.
Answer:
Primary metabolites are compounds essential for normal growth and physiological functions. Example : Amino acids, sugars, nucleotides. Secondary metabolites are compounds not directly involved in growth but often have ecological or medicinal roles. Example : Alkaloids, antibiotics, pigments

Question 6.
Distinguish between apoenzyme and cofactor.
Answer:

• Apoenzyme : Apoenzyme is the protein part of an enzyme that is inactive on its own.
• Cofactor: Non-protein part that binds to the holoenzyme is a co-factor.

Question 7.
How are prosthetic groups different from co-enzyme?
Answer:
Prosthetic groups are tightly bound to the apoenzyme, e.g. : Haeme group of peroxidase while co-enzymes are loosely and temporarily associated during the reaction. e.g.: Zn, NAD.

Question 8.
What are competitive enzyme inhibitors? Mention one example.
Answer:
Competitive enzyme inhibitors are chemicals that resemble the substrate and compete for the enzyme’s active site, blocking substrate binding. Example: Malonate inhibits succinic dehydrogenase.

Question 9.
Why are ‘Oxidoreductases’, so named ?
Answer:
Oxidoreductases are so named because they catalyse oxidation-reduction reactions between two substrates S and S′.
Malate + NAD → Oxaloacetate + NADH + H⁺

V. Biomolecules Short Answer Questions (4 Marks)

Question 1.
Schematically represent primary, secondary and tertiary structures of a hypothetical polymer using protein as an example.
Answer:
(a) Primary Structure:

• Definition : The primary structure of a protein is the linear sequence of amino acids in the polypeptide chain.
• Representation: Draw a straight line of circles or squares, each representing an amino acid. Label them with their respective one-letter codes (e.g., A for Alanine, R for Arginine, etc.). Connect these with lines to represent peptide bonds.

(b) Secondary Structure:

• Definition : The secondary structure refers to the local folding of the polypeptide chain into structures such as alpha helices and beta sheets.
• Representation: For the alpha helix, draw a spiral or coiled structure. For the beta sheet, draw arrows pointing in the direction of the polypeptide chains. Indicate whether they are parallel or antiparallel by arranging the arrows accordingly.

(c) Tertiary Structure:

• Definition: The tertiary structure is the overall three-dimensional shape of a single polypeptide chain, formed by the interactions between the side chains of the amino acids.
  

• Representation: Draw a more complex, folded structure that incorporates both the alpha helices and beta sheets from the secondary structure. Indicate interactions such as hydrogen bonds, Van der Waals forces, electrostatic interactions, and disulfide bonds with different types of lines or symbols.

Question 2.
Nucleic acid exhibits secondary structure, justify with example.
Answer:

• One of the secondary structures exhibited by DNA is the Watson-Crick model.
• According to this model, DNA exists as a double helix.
• The two polynucleotide strands are antiparallel, i.e., run in opposite directions.
• The backbone is formed by the sugar-phosphate-sugar chain.
• N₂ – bases are projected-perpendicular to the back bone, but face inside.
• Adenine (A) and Guanine (G) of one strand pair with Thymine (T) and Cytosine (C) of other strands, respectively.
• Two hydrogen bonds are present in between A and T. Three hydrogen bonds are present in between G and C .
• Each strand looks like a helical staircase. Each step is represented by a pair of N₂-bases.
• At each step of ascent, the strand turns 36°.
• Ten steps or ten base pairs are present in one full turn of the helix.
• The pitch (coil) would be 34 A°. The distance between two successive base pairs would be 3.4 A°. This form of DNA is called B-DNA.

Question 3.
Explain briefly about polysaccharides.
Answer:

• Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic bonds. The building blocks of polysaccharide are called monosaccharides.
• Cellulose is a homopolymer as it consists of only one type of monosaccharide called glucose. It is a structural polysaccharide present in the cell walls of plants and other organisms.
• Paper made from plant pulp is cellulose.
• Starch is a homopolymer of glucose and is used as energy storage in plant tissues.
• Glycogen is a branched homopolymer and is used as energy storage in animal cells.
• Inulin is a homopolymer of fructose and is used as energy storage in tuberous roots or stems. Ex : Asteraceae,
• In a polysaccharide chain, the right end is called the reducing end and the left end is called the non-reducing end.
• Complex polysaccharides possess amino-acids and chemically modified sugars (glucosamine, N -acetyl galactosamine etc).
• Exoskeleton of arthropods and the cell wall of fungi have a complex polysaccharide called chitin.

Question 4.
Explain how pH affects enzyme activity with the help of a graphical representation.
Answer:

• Enzymes are highly sensitive to changes in pH, and each enzyme functions best at a specific optimum pH
• The enzyme activity increases as the pH approaches this optimum value, and declines sharply if the pH moves either below or above it.
• This is because extreme pH levels can alter the enzyme’s structure, especially the tertiary structure, and denature the protein, making the active site ineffective.

In the Figure, illustrates this effect:

• The x-axis represents the pH range.
• The y-axis shows the enzyme activity.
• The curve rises to a peak at the optimum pH and then falls steeply, forming a bell-shaped curve.

This graph visually demonstrates that enzyme activity is highest at the optimum pH and decreases on either side due to enzyme denaturation or reduced binding efficiency.

Question 5.
Explain the mechanism of enzyme action.
Answer:
Mechanism of Enzyme Action: The chemical which is converted into a product is called a ‘substrate’. Hence enzymes, i.e., proteins with three dimensional structures including an ‘active site, convert a substrate (S) into a product (P).
Symbolically, this can be depicted as: S → P

Nature of Enzyme action:

• Each enzyme (E) has a substrate (S) binding site in its molecule so that a highly reactive enzyme-substrate complex (ES) is produced.
• This complex is short-lived and dissociates into its product(s) P and the unchanged enzyme, with an intermediated formation of the enzyme-product complex (EP).
• The formation of the ES complex is essential for catalysis.
  E+S → (ES) → (EP) → E+P
• Formation of (ES) complex has been explained with the ‘lock and key’ hypothesis by Emil fischer (1884) and much later with the ‘induced-fit hypothesis’ by Daniel E.Koshland.

The catalytic cycle of an enzyme action :

• First, the substrate binds to the active site of the enzyme, fitting into the active site.
• The binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate.
• The active site of the enzyme, now in close proximity to the substrate, breaks the chemical bonds of the substrate and the new enzyme – product complex is formed.
• The enzyme releases the products of the reaction and the free enzyme is ready to bind to another molecule of the substrate and runs through the catalytic cycle once again.

Question 6.
Define enzyme inhibition. Write briefly about competitive inhibition, give an example.
Answer:
Enzyme Inhibition is the process where a specific chemical, called an inhibitor, binds to an enzyme and reduces or stops its activity.
Competitive Inhibition: In competitive inhibition, the inhibitor resembles the substrate in structure and competes with it for the active site of the enzyme. Because of this, the substrate cannot bind, and the enzyme’s activity decreases. Example: Inhibition of succinic dehydrogenase by malonate, which closely resembles the enzyme’s normal substrate, succinate.
Such competitive inhibitors are often used in the control of bacterial pathogens.

Question 7.
Explain different types of cofactors.
Answer:
Different Types of Cofactors: Enzymes often require non-protein components called cofactors to become catalytically active. The protein part alone is called the apoenzyme, and when combined with a cofactor, it becomes a functional enzyme. There are three main types of cofactors :

• Prosthetic Groups
• Coenzymes
•  Metal Ions.

Prosthetic Groups: These are organic compounds that are tightly bound to the apoenzyme. They form a permanent part of the active site. Example : Haem in peroxidase and catalase, which helps break down hydrogen peroxide.

Coenzymes: These are organic molecules that temporarily bind with the enzyme during the reaction. They are often derived from vitamins. Examples : NAD (Nicotinamide Adenine Dinucleotide); NADP, both containing vitamin niacin.

Metal Ions: Some enzymes require metal ions to form coordination bonds with the active site and the substrate. These help in stabilizing the enzyme-substrate complex. Example: Zinc acts as a cofactor for the enzyme carboxypeptidase, Copper for Cytochrome oxidase. If the cofactor is removed, the enzyme loses its catalytic activity, showing the crucial role cofactors play in enzyme function.

VI. Biomolecules Long Type Questions (8 Marks)

Question 1.
What are secondary metabolites? Enlist them indicating their usefulness to man.
Answer:
Secondary metabolites: Metabolic products that do not have identifiable functions in the host organism are called secondary metabolites.
Thousands of compounds found in plant, fungal and microbial cells other than primary metabolites are called secondary metabolites.
Ex : Alkaloids, flavonoids, rubber, essential oils, antibiotics, coloured pigments, scents gums, spices, etc.
Some secondary metabolites:

• Pigments — Carotenoids, Anthocyanins etc.
• Alkaloids — Morphine, Codeine
• Terpenoides — Monoterpenes, Diterpenes
• Essential oils — Lemongrass oil
• Toxins — Abrin, Ricin
• Lectins — Concanavalin A
• Drugs — Vinblastine, curcumin
• Polymeric substances — Rubber, gums, cellulose

Many secondary metabolites are useful to human welfare.
Ex: Rubber, drugs, spices, scents and pigments.
1. Rubber:

• Uncured rubber is used for adhesive, insulating and friction tapes.
• Other significant uses of rubber are manufacturing of belts, matting, flooring, medical gloves and much more. Used rubber tyres are often recycled to make other items like shoes, bags, coats.

2. Drugs : In medicine:

• Antidiabetic drug is used to treat diabetes mellitus.
• Antihistamine medicine is used to treat allergies and hypersensitivity reactions and cold.
• Anti-inflammatory drug is intended to reduce inflammation.

In sports : Anabolic steroids are synthetic substances that stimulate proteins that help in building non-fat muscle mass, helping an athlete become stronger and able to play for longer periods of time.

3. Spices:

• Cloves: Cloves offer health benefits for reducing intestinal worms, digestive discomfort and can be used topically for toothache.
• Cardamom: This spice has been shown to reduce cancer development in animal studies and increase cell death of cancer cells in the colon. This herb can be used for its diuretic benefits.
• Asafoetida: It is used as a remedy for asthma and bronchitis. It has antiflatulent and antimicrobial properties.

4. Scents: These are used at various places like retail space with customers, hotel lobby with guests, an office space with clients and employees. Scents smell has a strong influence on the emotions we feel in our daily lives. Fragrances make clothes smell ‘clean’ cosmetics ‘pretty’ and households ‘well kept.

5. Pigments: These are used in food colouring, water colour paints, clothing dyes, Green tea guards against cardiovascular disease.

Question 2.
What are the processes used to analyze elemental composition, organic constituents and inorganic constituents of living tissue?
Answer:
Chemical analysis of a living tissue : On elemental analysis of a plant tissue, animal tissue or a microbial paste, a list of elements like carbon, hydrogen, oxygen and several others and their content per unit mass of a living tissue is known.
The relative abundance of carbon and hydrogen with respect to other elements is hig in any living organism than in earth’s crust.

A comparison of elements present in Non-living and Living matter

Element	% weight of Earth’s crust	% weight of Human body
Hydrogen (H)	0.14	0.5
Carbon (C)	0.13	18.5
Oxygen (0)	46.6	65.0
Nitrogen (N)	Very little	3.3
Sulphur (S)	0.03	0.3
Sodium (Na)	2.8	0.2
Calcium (Ca)	3.6	1.5
Magnesium (Mg)	2.1	0.1
Silicon (Si)	27.7	negligible

To analyse the organic compounds in a living tissue :

• Any living tissue should be taken and grind it in trichloroacetic acid (CCl₃COOH) using a mortar and a pestle.
• The obtained thick slurry should be strained through a cheesecloth or cotton.
• Two fractions can be obtained.
• a) Filtrate or acid soluble pool, and
• b) Retentate or acid insoluble fraction.
• Thousands of organic compounds can be found in acid soluble pools.
• To analyse a living tissue sample and to identify a particular organic compound, first the compounds should be extracted.
• Then the extract should be subjected to various separation techniques to separate a compound from all other compounds.
• The isolated compound should be purified. All the carbon compounds obtained from living tissue are called ‘biomolecules.
• Living organisms also contain inorganic elements and compounds in them.

To analyse inorganic elements and compounds in living organisms : A small amount of a living tissue should be weighed (wet weight) and it should be dried.

• As a result of this water evaporated. The remaining material gives dry weigh.
  Now, the tissue should be burnt. Due to this, all the carbon compounds are oxidised to gaseous form (CO)₂ and water vapour) and are removed.
• The remaining substance is called ‘ash.

This ash contains inorganic elements like calcium, magnesium, etc. Inorganic compounds like sulphate, phosphate, etc., are also seen in the acid soluble fraction.

A list of representatives inorganic constituents of living tissues

Compound	Formula
Sodium	Na+
Potassium	K+
Calcium	Ca++
Magnesium	Mg+ +
Water	H2O
Compounds	NaCl, CaCO3

•  Therefore, element analysis gives elemental composition of living tissues in the form of hydrogen, oxygen, chlorine, carbon, etc.
• The analysis of compounds gives the analysis of organic and inorganic constituents present in living tissues.

Question 3.
Write an account of the classification of enzymes.
Answer:
Classification of Enzymes: Enzymes are biological catalysts that speed up chemical reactions. Based on the type of reaction they catalyze, enzymes are classified into six major classes, each with further subclasses. This classification is standardized and each enzyme is given a four-digit number.

1. Oxidoreductases / Dehydrogenases :

• Enzymes which catalyze oxidation-reduction (redox) reactions between two substrates S and S’.
• Example : S reduced +S‘ oxidised → S oxidized+S’ reduced

2. Transferases :

• Enzymes that catalyze the transfer of a group (excluding hydrogen) between a pair of substrate S and S’
• Example: S-G+S’ → S+S’-G

3. Hydrolases:

• Enzymes that catalyze the hydrolysis of various bonds like ester, ether, peptide, glycosidic, C-C,C- halide, or P-N bonds.
• These are involved in breaking down large molecules with the help of water.

• Lyases: Enzymes that catalyze the removal of groups from substrates by methods other than hydrolysis, often forming double bonds in the process.
• Isomerases: Enzymes that catalyze inter-conversion of isomers, including optical, geometric, or positional isomers.

Ligases :

• Enzymes that catalyze the joining (ligating) of two molecules, forming new C-O, C-S, C-N, or P-O bonds.
• Require energy, often from ATP.

Biomolecules Class 11 Extra Questions and Answers

I. Multiple Choice Questions (1 Mark)

Question 1.
The most abundant protein in the animal world is ……………
(1) Insulin
(2) Collagen
(3) Trypsin
(4) Antibody
Answer:
(2) Collagen

Question 2.
Exoskeleton of arthropods contain a complex polysaccharide namely ……………
(1) Cellulose
(2) Chitin
(3) Inulin
(4) Glycogen
Answer:
(2) Chitin

Question 3.
A nucleotide differs from a nucleoside by the presence of ……………
(1) Deoxyribose sugar
(2) Ribose sugar
(3) Phosphate
(4) Thymine
Answer:
(3) Phosphate

Question 4.
Quaternary structure of some proteins are unique in the way that they contain ……………
(1) Alpha helix
(2) Subunits (Polypeptide Chains)
(3) Beta pleated sheets
(4) Disulphide bonds
Answer:
(2) Subunits (Polypeptide Chains)

Question 5.
Which of the following comes under secondary metabolites ?
(1) Abrin
(2) Ricin
(3) Both
(4) Sugars
Answer:
(3) Both

Question 6.
Morphine is a ……………
(1) Alkaloid
(2) Lectin
(3) Pigment
(4) Drug
Answer:
(1) Alkaloid

Question 7.
Lower melting point oils are ……………
(1) Gingelly oil
(2) Lemongrass oil
(3) Castor oil
(4) Mustard oil
Answer:
(1) Gingelly oil

Question 8.
Insulin is a ……………
(1) Hormone
(2) Enzyme
(3) Antibody
(4) Antigen
Answer:
(1) Hormone

Question 9.
Water accounts to how much % of total cellular mass ?
(1) 70-90
(2) 10 – 15
(3) 5-7
(4) 3
Answer:
(1) 70-90

Question 10.
Nucleic acids account for how much % of total cellular mass ?
(1) 70-90
(2) 10 – 15
(3) 5-7
(4) 3
Answer:
(3) 5-7

Question 11.
Which of the following is an enzyme ?
(1) Insulin
(2) Collagen
(3) Trypsin
(4) Antibody
Answer:
(3) Trypsin

II. Fill in the Blanks (1 Mark)

Question 1.
Name the four major elements obtained by the elemental analysis of plant tissue, animal tissue or a microbial paste …………
Answer:
Carbon, hydrogen, oxygen and nitrogen

Question 2.
For chemical analysis of living tissue, it is grinded in ………… using a mortar and a pestle.
Answer:
Trychloroacetic acid

Question 3.
The weight of a living tissue is called …………
Answer:
Net Weight

Question 4.
The inorganic materials of living organisms are obtained from …………
Answer:
Ash

Question 5.
Name any two inorganic compounds which are present in the acid soluble fraction of living tissue. …………
Answer:
Sulphate, Phosphate

Question 6.
Protein percentage in the total cellular mass is …………
Answer:
10-15%

Question 7.
Lipids percentage in the total cellular mass is …………
Answer:
2%

Question 8.
The most abundant chemical in all living organisms is …………
Answer:
Water

Question 9.
Plant cell walls are made of …………
Cellulose

Question 10.
How many chemically distinct components are present in a nucleotide ? …………
Three

Question 11.
The purines in DNA are …………
Answer:
Adenine and Guanine

Question 12.
A protein is imagined as a line, which end is represented by the first amino acid …………
Answer:
Left end

Question 13.
The first amino acid is also called as …………
Answer:
N-terminal amino acid

Question 14.
Nucleic acids that behave like enzymes are called …………
Answer:
Ribozymes

Question 15.
At which temperature enzymes get damaged ? …………
Answer:
Above 40°C

III. One Word Answer Questions (1 Mark)

Question 1.
Neutral amino acid is ……….
Answer:
Valine

Question 2.
Basic amino acid is……….
Answer:
Lysine

Question 3.
Acidic amino acid is……….
Answer:
Glutamic acid

Question 4.
What is the nature of amino acid having an extra carboxylic group ?
Answer:
Acidic

Question 5.
Hydrolysis of starch into glucose is an……….
Answer:
Organic chemical reaction.

Question 6.
Without enzyme; how many molecules of H₂CO₃ are formed from CO₂ and H₂O in an hour.
Answer:
200

Question 7.
Enzymes catalysing hydrolysis of ester bonds are……….
Answer:
hydrolases

Question 8.
Organic compounds that are tightly bound to the apoenzyme are……….
Answer:
Prosthetic group

Question 9.
Enzymes which catalyze the breakdown of hydrogen peroxide to water and oxygen are ……….
Answer:
Peroxidases and catalases

Question 10.
Aromatic amino acids are……….
Answer:
Tyrosine, phenylalanine, tryptophan.