Chemical Reactions in Biochemistry

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Questions and Answers

What is produced when the aldehyde group of a sugar undergoes oxidation?

Dulcitol

Fructose

Uronic acid (correct)

Sorbitol

Which of the following reactions results from the action of strong alkalis on sugars?

Formation of β-hydroxy aldehyde

Reduction to corresponding alcohols

Polymerization through aldol condensation (correct)

Isomerization to fructose

What function does the free aldehyde or ketone group serve in a reducing reaction?

Act as a substrate

Act as a reducing agent (correct)

Act as a solubilizing agent

Act as a catalyst

Which of the following is a result of the oxidation of both the aldehyde and last alcoholic group of a carbohydrate?

Saccharic acid Signup and view all the answers

Which reaction type involves the removal of a water molecule from a β-hydroxy aldehyde or ketone?

Dehydration Signup and view all the answers

What occurs during the process of melting?

Heat is absorbed from the solid. Signup and view all the answers

Which of the following processes involves a decrease in temperature?

Condensation Signup and view all the answers

What describes the process of vaporization?

It requires heat to be transferred from the surroundings to the liquid. Signup and view all the answers

Which statement accurately describes freezing?

It occurs when the temperature of a liquid decreases below its freezing point. Signup and view all the answers

What happens to kinetic energy when a solid undergoes sublimation?

It increases, allowing molecules to escape. Signup and view all the answers

What is the main feature of boiling as a phase change?

It requires the liquid to reach its boiling point before transitioning to vapor. Signup and view all the answers

What is the nature of pressure's effect on the phase changes of materials?

Higher pressure always leads to higher melting points. Signup and view all the answers

Which phase change requires heat to be added to the system?

Vaporization Signup and view all the answers

Which of the following amino acids contains a sulfur group?

Cysteine Signup and view all the answers

What distinguishes basic amino acids from other classifications?

They contain more than one amino group. Signup and view all the answers

Which amino acid is a precursor to serotonin, melatonin, and niacin?

Tryptophan Signup and view all the answers

Which amino acid does NOT contain an aromatic ring?

Proline Signup and view all the answers

D-amino acids are characterized by which structural feature?

Amine group on the right of the asymmetric carbon Signup and view all the answers

Which amino acids are classified as amidic amino acids?

Glutamine and Asparagine Signup and view all the answers

Which classification does Methionine fall under?

Aliphatic amino acid Signup and view all the answers

What type of amino acid is Lysine categorized as?

Basic amino acid Signup and view all the answers

What is the primary role of lecithin in biological membranes?

To serve as a structural component Signup and view all the answers

Which of the following compounds is formed from lecithin by the action of lecithinase?

Lysolecithin Signup and view all the answers

What is the function of phosphatidylserine in the body?

Involved in coagulation Signup and view all the answers

What distinguishes plasmalogens from cephalins?

Attachment of unsaturated alcohol by ether linkage Signup and view all the answers

Which glycerophospholipid is particularly important in the mitochondrial membrane?

Cardiolipin Signup and view all the answers

What condition results from sphingomyelinase enzyme deficiency?

Niemann-Pick's disease Signup and view all the answers

Which type of fatty acids are primarily found in lecithin?

A mix of saturated and unsaturated fatty acids Signup and view all the answers

Which of the following is true about lipositol?

It acts as a precursor for second messengers Signup and view all the answers

Which of the following statements accurately describes the action of phosphoric acid?

It gives rise to phosphate esters such as glucose6phosphate. Signup and view all the answers

What is the result of the fermentation process involving all monosaccharides except for pentoses?

Production of ethyl alcohol and carbon dioxide. Signup and view all the answers

Which of the following sugars does not form osazone crystals when reacted with phenylhydrazine?

Sucrose Signup and view all the answers

Which of the following describes a sugar alcohol?

Lacks both aldehyde and ketone groups. Signup and view all the answers

What characterizes deoxy sugars?

One hydroxyl group is replaced by a hydrogen atom. Signup and view all the answers

Which of the following amino sugars is acetylated?

N-acetylglucosamine Signup and view all the answers

What effect does sulfuric acid have on sugar during the dehydration process?

It removes water to form a violet ring with α naphthol. Signup and view all the answers

Which derivative of sugar is produced when the aldehyde at C1 or OH at C6 undergoes oxidation?

Sugar acids Signup and view all the answers

What is the process by which the removal of CO2 from amino acids occurs to form amines called?

Decarboxylation Signup and view all the answers

What color is produced when tyrosine reacts with Millon's reagent after boiling?

Red Signup and view all the answers

Which amino acid does not yield a positive sulfur reaction test due to its sulfur being masked?

Methionine Signup and view all the answers

Which reaction is characterized by the formation of esters from amino acids?

Esterification Signup and view all the answers

Which group in tryptophan is responsible for the purple color when reacted with Rosenheim's reagent?

Indole group Signup and view all the answers

What is the result when cysteine or cystine reacts with lead acetate?

Black color Signup and view all the answers

In dicarboxylic amino acids, what compound can the last –COOH group combine with to form an amide?

Ammonia Signup and view all the answers

Which amino acid forms glutamine when its carboxylic group reacts with ammonia?

Glutamic acid Signup and view all the answers

Study Notes

General Chemistry - Physical Chemistry

Physical chemistry is a branch of general chemistry
Focuses on the structure and properties of matter

Matter

Matter is anything that has mass and volume
Examples of matter are cups, pens, and erasers
Another definition of matter is anything composed of atoms and molecules
Matter is ultimately made of protons, neutrons, and electrons

Structure of Matter

Atoms are the building blocks of matter
Atoms are constantly in motion
Combinations of atoms form different materials with varied properties

Atoms

Atoms are composed of protons, neutrons, and electrons
Protons have a positive charge
Neutrons have no charge (neutral)
Electrons have a negative charge
The nucleus, at the atom's center, contains protons and neutrons
Electrons orbit the nucleus

Nucleus

The nucleus is the positively charged center of an atom
Protons and neutrons are found in the nucleus
Protons have a positive charge
Neutrons have zero charge

Atom

Electrons orbit the atom's nucleus
Electrons have a negative charge

Structure of Atom

Atoms are of the order of 10-8 cm in size
Nuclei are of the order of 10-12 cm in size
Electrons are of the order of 10-16 cm in size
Quarks are smaller than electrons; they compose protons and neutrons

Phases of Matter

Matter exists in four phases (or states): solid, liquid, gas, and plasma
Solids have definite mass, volume, and shape
Liquid have definite mass and volume, but indefinite shape
Gases have indefinite mass, volume, and shape
Plasma is an ionized gas, exhibiting indefinite mass and volume, and an indefinite shape

States of Matter

Matter's states depend on particle arrangement, energy, and distance between particles

Solid

Solids have definite mass, volume and shape
Particles of solids are tightly packed, vibrating in a fixed position

Liquid

Liquids have definite mass and volume but do not have a definite shape
Particles of liquids are tightly packed but are far enough apart to slide over each other

Gas

Gases have no definite mass, volume and shape
Particles of gases are relatively far apart and move freely

Plasma

Plasma is an ionized gas
Plasmas are good conductors of electricity and are affected by magnetic fields
Plasmas have an indefinite shape and volume

Phase Changes

Melting: solid to liquid
Freezing: liquid to solid
Vaporization: liquid to gas
- Boiling: rapid type of vaporization
- Evaporation: slow type of vaporization
Condensation: gas to liquid
Sublimation: solid to gas

Melting

Melting is a solid-to-liquid change
Melting typically occurs at a fixed temperature (melting point)
In pure crystalline solids, this is a fixed temperature

Freezing

Freezing is a liquid-to-solid change
Freezing occurs at a fixed temperature (freezing point)

Vaporization

Vaporization is liquid-to-gas change, including boiling and evaporation
Liquids turn into gas when temperature is increased, and kinetic energy of molecules increases.
Molecules escape into surrounding as vapors

Evaporation

Evaporation is a type of vaporization
Evaporation occurs at temperatures below the boiling point

Condensation

Condensation is the change from gas to liquid
Condensation results when water vapor cools to below its boiling point

Sublimation

Solid changing to gas with no liquid phase in between
Dry ice (solid carbon dioxide) sublimates at ordinary pressure and temperature

Intermolecular Forces

Intermolecular forces are the forces that occur between individual particles of atoms, molecules or ions of a substance
These forces relative to intramolecular forces are quite weak; ie covalent or ionic bonds

Kinetic Energy

Kinetic energy is the energy an entity has because of its motion
Work done on an object by applying a net force results in a gain of kinetic energy

Properties of Gases

Gases consist of widely separated molecules
The kinetic energy of gas molecules is greater than any attractive force
Gases expand to fill their containers because of the lack of significant attractive forces

Properties of Liquids

Liquids have strong intermolecular forces to hold molecules close together
Liquids are less compressible than gases
Liquids are more dense than gases
Molecules of liquids are free to flow past one another
Liquids assume the shape of their container

Properties of Solids

Solids have strong intermolecular forces to keep their constituent molecules fixed
Solids are less compressible due to lack of space between molecules
Highly ordered arrangements of molecules produce solid crystals

Types of Intermolecular Forces

Permanent dipole-permanent dipole forces (Kessom forces)
Permanent dipole-induced dipole forces (Debye forces)
Induced dipole-induced dipole forces (London or dispersion forces)
Hydrogen bonding

Permanent Dipole-Permanent Dipole Forces

Dipole-dipole forces exist between polar covalent molecules
One molecule's (+) charged poles attract the (-) charged poles of other molecules

Permanent Dipole-Induced Dipole Forces

Polar molecules can induce dipoles into nonpolar molecules
Polar molecules induce dipoles in surrounding molecules

Induced Dipole-Induced Dipole Forces (London or Dispersion Forces)

These forces are present between all molecules
They arise from momentary, asymmetrical electron distributions

Hydrogen Bonding

Hydrogen bonding is a strong type of dipole-dipole interaction between a hydrogen atom bonded to a highly electronegative atom (F, O, or N) and another highly electronegative atom in a neighboring molecule

Molecular Shape and Intermolecular Attraction

Molecular shape affects the strength of intermolecular forces
Linear shape molecules have a larger surface area, increasing intermolecular attraction
Sphericity decreases dispersion forces

Carbohydrate Chemistry

Carbohydrates are polyhydroxy aldehydes or ketones
General formula is Cn(H2O)n
They are the chief energy source in the human body (50-60%)

Classification of Carbohydrates

Monosaccharides: contain one basic sugar unit
Disaccharides: contain 2 monosaccharide units
Oligosaccharides: contain 3 to 10 monosaccharide units
Polysaccharides: contain more than 10 monosaccharide units

Monosaccharides Naming

Named based on the presence of aldehyde or ketone groups, and the number of carbon atoms

Trioses

Monosaccharides with 3 carbon atoms
Aldotriose: Glyceraldehyde (parent sugar)
Ketotriose: Dihydroxyacetone

Tetroses

Monosaccharides with 4 carbon atoms
Aldotetrose: Erythrose
Ketotetrose: Erythrulose

Pentoses

Monosaccharides with 5 carbons
Aldopentoses: Ribose, arabinose, xylose and lyxose
Ketopentoses: Ribulose and xylulose

Hexoses

Monosaccharides with 6 carbon atoms
Aldohexoses: Glucose, galactose, and mannose
Ketohexose: Fructose

Ring (Cyclic) Structure of Sugars

Open chain formulas of sugars fail to explain all reactions
This indicates that the -CHO group must be masked or combined somewhat

Haworth and Chair Forms

Cyclic forms of monosaccharides
The 1-5 ring form is called pyranose
The 1-4 ring form is called furanose

Mutarotation

Mutarotation: change of specific rotation in optically active compounds; usually carbohydrates

Aldose-ketose isomerism

Isomers with the same molecular formula but which differ in structure
Glucose is an aldose
Fructose is a ketose

Epimeric Carbon and Epimers

Isomers that differ in configuration at only one asymmetric carbon
D-glucose and D-galactose are epimers

Properties of Monosaccharides

All monosaccharides are soluble in water
Monosaccharides are optically active
Monosaccharides can exist in a and ẞ forms, and exhibit mutarotation

Chemical Properties of Carbohydrates

Oxidation: converting aldehyde group to aldonic acid; last alcoholic group to uronic acid; aldehyde and last alcoholic groups to saccaric acid
Reduction: reducing aldehyde or ketone groups into alcohols
Action of alkalis: isomerization; polymerization (aldol condition)
Action of acids: phosphate esters; furfural derivatives (Molisch test)
Fermentation: converting sugars into alcohol and CO2 by bacteria or yeast
Osazone formation: forming yellow crystals by reacting with phenylhydrazine

Monosaccharide Derivatives

Sugar acids
Sugar alcohols
Deoxy sugars
Amino sugars
Amino sugar acids
Glycosidic bond and glycosides (Glycosides)

Glycosidic Bond and Glycosides (Glycosides)

The bond between a carbohydrate and another compound; could be another monosaccharide or a noncarbohydrate (aglycone) group
Glycosides are naturally occurring substances and often extracted as drugs

Disaccharides

Formed from two monosaccharides bonded by a glycosidic bond
Maltose (glucose + glucose, α(1→4) glycosidic bond)
Isomaltose (glucose + glucose, α(1→6) glycosidic bond)
Lactose (galactose + glucose, β(1→4) galactosidic bond)
Sucrose (glucose + fructose, α(1→2) glycosidic bond)
Cellobiose (glucose + glucose, β(1→4) glycosidic bond)
Trehalose (glucose + glucose, α(1→1) glycosidic bond)

Polysaccharides

Polymers of more than 10 monosaccharides
Classified as homopolysaccharides or heteropolysaccharides

Homopolysaccharides

Contain repeated same sugar units
Starch (amylose and amylopectin): plants; storage form of glucose
Glycogen: animals; storage form of glucose
Cellulose: plant cell walls; fibrous material; ẞ-linkages

Heteropolysaccharides

Contain two or more different repeated monosaccharide units
Acidic: containing uronic acid + aminosugar (GAGs); e.g. hyaluronic acid, chondroitin 4,6-sulfate, dermatan sulfate, heparin sulfate
Neutral: no uronic acid or sulfuric acid; e.g. blood groups, glycoprotein hormones

Specific Properties of TAG, Waxes

TAG: (triacylglycerol): usually liquid at room temperature (is fats/oils)
Waxes: typically solid at room temperature

Lipids: Definition and Classification

Simple lipids: fatty acids + alcohol
Compound lipids: fatty acids + alcohol + additional group
Derived lipids: result from the hydrolysis of simple or compound lipids

Simple Lipids

Neutral fats (triacylglycerols or TAGs): glycerol + fatty acids (storage form for fat)
Waxes: fatty acids + long chain alcohol (like that used in cosmetics)

Properties of TAG

TAG are soluble in fat solvents
TAG rich in unsaturated fatty acids: typically liquid at room temperature
TAG rich in saturated fatty acids: typically solid or semi-solid at room temperature
Acrolein Test
Hydrolysis
Saponification: cleaved by alkali into glycerol and salts of fatty acids (soaps)
Halogenation
Oxidation (rancidification); occurs readily if unsaturated fatty acids are present

Complex (Compound) Lipids

1- Phospholipids (fatty acids + alcohol + phosphoric acid residues + nitrogenous base)
- Glycerophospholipids: alcohol is glycerol
- Sphingophospholipids: alcohol is sphingosine
2- Glycolipids (Fatty acid + sphingosine + carbohydrate)
- Neutral glycolipids (Cerebrosides) : ceramide + monosaccharide
- Acidic glycolipids (Gangliosides): ceramide + monosaccharide + one or more sialic acids
3- Lipoproteins: lipids conjugated with proteins; facilitates transport between blood and tissues
4- Sulfolipids
5- Aminolipids

Steroids and Sterols

Cyclic compounds containing cyclopentanoperhydrophenanthrene ring
Cholesterol: major sterol; found in cell membranes, precursor to steroid hormones and bile acids

5- Branched Chain Fatty Acids

Primarily saturated fatty acids with branches in the hydrocarbon chain
Phytanic acid (18C) is an example; it is formed by bacterial degradation of chlorophyll

6- Cyclic Fatty Acids

Unusual class of minor fatty acids produced primarily by bacteria
Cyclopropane and omega-cyclohexyl fatty acids are examples; found in bovine meat and dairy products

Classification of Fatty Acids

Saturated fatty acids: no double bonds in the hydrocarbon chain
- Examples include acetic acid (2C), butyric acid (4C), caproic acid(6C), caprylic acid (8C), capric acid (10C), lauric acid (12C), myristic acid (14C), palmitic acid (16C), stearic acid (18C), arachidic acid (20C), behanic acid (22C), and lignoceric acid (24C)
Unsaturated fatty acids: 1 or more double bonds in the hydrocarbon chain
- Examples include myristoleic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid
Essential fatty acids
- Polyunsaturated fatty acids (PUFAs)

Omega-3 Fatty Acids

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are examples
Found predominantly in fish
Potential roles in disease prevention

Omega-6 Fatty Acids

Linoleic acid (LA) and arachidonic acid (ARA) are examples
Found in vegetable oils like corn, soybean, and cottonseed
Possible roles in inflammation, growth and development

Cis- and Trans Fatty Acids

Cis isomers: hydrogen atoms(on the same side of the double bond)
Trans isomers: hydrogen atoms are (on opposite sides of the double bond); more common in processed foods; less healthy

Waxes

Acetyl alcohols are present
Long-chain fatty acids are present

Enzymes

Protein catalysts produced from cells
Increase the rate of chemical reactions
Act in all living systems without changing themselves
Have specific active sites, interacting with particular substrates, and requiring specific substrates, cofactors, etc.
Nomenclature: -ase suffix to enzyme; also named according to their class and function (e.g. Oxidoreductase, transferases and hydrolases etc)
Enzyme code (EC) numbers are used; have 4 digits and are an identifier for enzymes
Factors affecting enzyme activity: substrate concentration, enzyme concentration, end product concentration, temperature, pH, time and activators / inhibitors

Enzyme Specificity

Absolute specificity: enzymes act on only one substrate
Relative specificity: enzymes act on one type of bond
Structural specificity: enzymes act on specific structures of a molecule

Enzyme Classification

1 - Oxidoreductase: catalyzes oxidation-reduction reactions
- Oxidases: form water
- Hydroperoxidases: act on hydrogen peroxide; e.g. catalase, peroxidase
- Dehydrogenases
- Oxygenases
2 - Transferase: catalyzes the transfer of a functional group (other than hydrogen) from one substrate to another
3 - Hydrolases: catalyzes the hydrolysis of bonds by the addition of water
- Glycosidases: act on glycosidic bonds
- Estrases: catalyzes the hydrolysis of ester bonds
- Lipidase
4 - Lyases: catalyze the addition or removal of atoms or molecules from substrates; do not involve water
5 - Isomerases: catalyze the interconversion of isomers - two isomer forms of the same molecule
6 - Ligases: catalyze the joining of two molecules using energy from ATP

Factors Affecting Enzyme Activity

1 - Substrate concentration
2 - Enzyme concentration
3 - End product concentration
4 - Temperature
5 - pH
6 - Time
7 - Activators: increase reaction rate (removing inhibitory peptides, reducing agent)
8 - Inhibitors:

Enzyme Inhibitors

Competitive inhibitors
Non-competitive inhibitors
Uncompetitive inhibitors
Irreversible inhibitors; e.g. lead, cyanide

Protein Structure

Primary structure: sequence of amino acids
Secondary structure: local folding of polypeptide chain (e.g. helices and sheets)
Tertiary structure: complete 3D shape of a polypeptide chain
Quaternary structure: multiple polypeptide chains

Denaturation of Protein

Loss of native structure (natural conformation) caused by physical or chemical agents
Example: heat, violent shaking, chemical agents, etc.

Protein Classifications

Based on shape: fibrous proteins (long, rod-shaped) and globular proteins (compact, spherical)
Based on function
- Dynamic Function: (enzymes, hormones, contractile proteins
- Structual function
Based on composition: simple/conjugated proteins
Based on biological value

Simple Proteins

Albumins and globulins
Protamines
Histones
Gliadins (prolamines)
Glutelins
Scleroproteins (e.g. keratin, collagen, elastin, ossein, reticulin)

Conjugated Proteins

Phosphoproteins: contain phosphoric acid
Glycoproteins: contain carbohydrates
Lipoproteins: contain lipids
Nucleoproteins: contain nucleic acids
Chromoproteins: contain colored prosthetic groups
Metalloproteins: contain metals as prosthetic groups (e.g. iron in hemoglobin)

Derived Proteins

Hydrolytic by-products of proteins
E.g. gelatin

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Description

Explore key concepts in biochemistry related to the oxidation of sugar aldehyde groups and phase changes in matter. This quiz includes questions about reducing reactions, the effects of temperature on these processes, and specific properties of amino acids. Test your knowledge and understanding of fundamental biochemical reactions and physical chemistry.