Atomic Composition and Bonding

Atomic Composition

• Atoms are composed of a nucleus and an electron cloud.
• The nucleus contains heavy, positively charged protons and neutral neutrons.
• Electrons are negatively charged, very small, and move rapidly around the nucleus, being responsible for chemical bonding and reactions.

Elements vs. Isotopes

• Elements are defined by the number of protons in their atoms.
• Isotopes are atoms of the same element and have the same number of protons, but different numbers of neutrons, leading to different atomic masses.

Ionic vs. Covalent Bonds

• Ionic bonds involve the transfer of electrons between a metal and a non-metal. An example is NaCl.
• Covalent bonds involve the sharing of electrons between two non-metals. An example is H₂O. These bonds create stable electron pairings.

Electron Arrangement

• Electrons are arranged in orbitals and occupy specific energy levels or shells around the nucleus.
• The lower shells fill first, and valence electrons in the outermost shell are involved in bonding.

Valence Electrons

• For neutral atoms, the number of valence electrons is equivalent to the group number for main group elements.
• For ions, electron count can be adjusted based on charge, subtracting electrons for cations and adding for anions.

Polar vs. Non-Polar Bonds

• Polar bonds occur between atoms with different electronegativities, creating partial charges.
• Non-polar bonds occur between atoms with equal or similar electronegativities. Greater electronegativity differences lead to more polar bonds.

Electronegativity and Bond Polarity

• Comparing electronegativity values can show how bond polarity occurs
• Large differences results in more polar bonds, such as O-H being more polar than C-H, because oxygen is more electronegative than hydrogen.

Molecular Polarity and Solubility

• Polar molecules with a net dipole dissolve well in polar solvents like water.
• Non-polar molecules with symmetrical non-polar bonds dissolve better in non-polar solvents such as oil.

Hydrogen Bonds

• Hydrogen bonds form between a hydrogen atom covalently bonded to N, O, or F and a lone pair on another N, O, or F.
• This is represented as a dashed line between the δ⁺ hydrogen and the lone pair of a δ⁻ oxygen or nitrogen on water.

Water States and Hydrogen Bonding

• Hydrogen bonds form a stable lattice in ice.
• Hydrogen bonds constantly form and break in liquid water.
• Hydrogen bonding is minimal in gas, due to large molecular spacing.

Water and Energy Requirements

• Energy is needed to break hydrogen bonds for phase changes that can occur in melting or evaporation.
• Latent heat is the energy absorbed to disrupt hydrogen bonding without changing temperature.

Atom Connectivity and Chirality

• Atom arrangement affects a molecule's shape and function.
• Isomers of the same compound may have different flavors, smells, and nutritional effects.
• Chiral molecules can interact differently with biological receptors, based on handedness.

Basic Tastes

• Receptors can detact five taste, which are:
  • Sweet (sugars)
  • Salty (Na⁺ ions)
  • Sour (H⁺ ions)
  • Bitter (varied molecules, often toxic)
  • Umami (glutamate, an amino acid)

Odor Detection

• Smells are detected through unique combinations of olfactory receptors
• The brain interprets these combinations as specific smells using a combinatorial coding system. This is similar to letters forming words.

Lock-and-Key Model

• The lock-and-key model suggests a molecule (ligand) fitting only into a receptor's active site, just like a key in a lock.
• Only specific molecules trigger specific responses.

Ligand-Receptor Interaction

• The strongest interaction between receptor and ligand occurs with ideal fit
• Ideal fit results in multiple favorable interactions like hydrogen bonds, complementary charges, and hydrophobic effects .

pH Scale

• Low pH indicates high H₃O⁺ concentration, showing acidity.
• High pH indicates high OH⁻ concentration, showing basicity.
• The product of [H₃O⁺] and [OH⁻] is always 1 × 10⁻¹⁴ at 25°C.

pH Comparison

• Lower pH values indicate greater acidity.
• Each pH unit change leads to a tenfold change in acidity; pH 3 is 10 times more acidic than pH 4.

pKa and Acid/Base Strength

• Lower pKa values signify stronger acids, which dissociate more readily in water.
• Higher pKa values signify weaker acids or stronger bases.

pKa and Molecular Form

• Deprotonation is the conjugate base form when pH > pKa.
• Protonation is the conjugate acid form when pH < pKa.

Molecular Charge

• Assess each site's protonation state using its pKa and the solution's pH
• Add up charges based on whether groups are protonated (+1 for amines, 0 for neutral) or deprotonated (–1 for acids).

Dynamic Equilibrium

• Forward and reverse reactions occur at the same rate.
• Le Chatelier’s Principle states that systems counteract disturbances such as a changed concentration, pressure, or temperature.

Coupled Equilibria

• Changing the concentration of one product or reactant can shift both equilibria.
• For example, removing a product from one reaction drives it forward and shifts the second reaction.

Wavelength and Energy

• Longer wavelengths have lower energy. Red and infared are examples.
• Shorter wavelengths have higher energy. Blue or UV are examples.
• Energy and wavelength are inversely related.

Color Perception

• Color is perceived as the reflected or transmitted light wavelengths
• Absorbed colors are not visible; a red object reflects red light and absorbs other wavelengths.

Color Absorption

• The complementary color wheel can show how color absorption occurs
• An object appears green when it absorbs red light, and yellow when it absorbs blue light.

Sigma vs. Pi Bonds

• Sigma (σ) bonds form from head-on orbital overlap and are the first bond between atoms; stronger, allow rotation.
• Pi (π) bonds form from side-by-side overlap and appear in double and triple bonds; does not allow rotation.

Light Absorption

• A molecule absorbs light when a photon's energy matches the energy gap between electronic energy levels.
• Doing so promoting an electron to a higher orbital.

Conjugated Pi Bonds

• Conjugated pi systems have alternating single and double bonds with delocalized electron clouds.
• To identify the amount, you count the number of double bonds separated by single bonds sequentially.

Light Absorption and Conjugation

• Conjugated systems lower the orbital energy gap, causing absorption of longer light wavelengths
• This produces visible colors in food pigments like carotenoids and flavonoids.

Triglyceride Structure

• One glycerol molecule, that is a three-carbon alcohol, bonds to three fatty acid chains via ester bonds.
• Each fatty acid varies in length and saturation, influencing the triglyceride's properties (solid or liquid at room temperature).

Cis vs. Trans Double Bonds

• Hydrogen atoms are on the same side of the double bond, causing a kink in the fatty acid chain. It is in the cis structure
• Hydrogen atoms are on opposite sides, creating a straight chain similar to saturated fats. It is in the trans structure
• Such structures can be drawn using zig-zag skeletal structures where the geometry is bent (cis) or straight (trans).

Double Bond Geometry

• Cis double bonds create kinks that prevent tight lipid molecule packing, making them more fluid and lowering their melting temperature.
• Trans double bonds allow tighter packing, which leads to higher melting points and a more solid consistency at room temperature.

Double Bonds

• Double bonds, especially in unsaturated fats, are chemically reactive and more prone to oxidation, which can cause rancidity.
• The more double bonds a lipid has, the more chemically unstable it becomes when exposed to heat, light, or oxygen.

van der Waals interactions

• van der Waals interactions are weak, non-specific forces between all atoms or molecules in close proximity.

London dispersion forces

• London dispersion forces are van der Waals forces that are temporary dipoles when electrons randomly shift.
• They are especially important in non-polar molecules like fats.

Hydrophobic Effect

• Refers to the tendency of non-polar substances to cluster in aqueous environments
• Minimizing contact with water and increasing the entropy of the system

Hydrophobic, Hydrophilic, and Amphiphilic Entities

• Hydrophobic substances repel water. Examples are Non-polar like oil or fatty acid tails.
• Hydrophilic substances are attracted to water. An example is polar or charged, like sugar or salt.
• Amphiphilic molecules contain both hydrophobic and hydrophilic regions. For example is phosopholipids and surfactants. They interact with both oil and water.

Definition of Entropy

• Entropy describes the randomness or disorder that may exist with a system
• Increases the number of possible microstates and is thermodynamically more stable.

Types and Degradation of Emulsions

• A mixture of two immiscible liquids, usually oil and water, where one is dispersed as droplets in the other.
• Emulsifiers can degrade or break due to coalescence, creaming, flocculation, or phase separation over time.

Functioning of Emulsifiers

• Emulsifiers/surfactants have hydrophobic tails and hydrophilic heads.
• Emulsifiers position themselves at the oil-water interface, decreasing surface tension and surrounding fat droplets in a stabilizing barrier. This can prevent merging that leads to separating from the water phase.

Emulsion Stabilizers

• Additives like gums, proteins, or modified starches increase the viscosity of the continuous phase or strengthen the interfacial layer around droplets.
• Others like lecithin, mono- and diglycerides, or xanthan gum, act directly at the interface to improve emulsion stability
• Stabilizers can prevent droplet coalescence and delaying separation

Polymers

• Polymers are molecules of repeating smaller units, aka monomers, linked together like a chain.
• Starch, proteins, and cellulose are food polymers.
• Biopolymers are polymers that are made by living organisms, like starch, gelatin, and cellulose.
• Can be linear or branched. Amylose and amylopectin are examples
• Their properties like thickening, gelling, strtching, depend on interactions with water.

Carbohydrates

• Molecules made of carbon, hydrogen, and oxygen. They usually have a 1:2:1 ratio. C6H12O6 is an example.
• Carbs come in three main forms: Monosaccharides, Disaccharides, Polysaccharides
• They have -OH groups or ring-shaped structures.

Starch vs Cellulose

• Starches have α(1→4) glycosidic bonds. They have coiled/branched structures and are easy too digest and also store energy in support cells
• Cellulose have β(1→4) glycosidic bonds. They are rigid and are not easily digested and provide structural support

Starches

• Amylose has linear chains and forms firmer gels.
• Amylopectin has branched chains and forms softer and more viscous gels
• Most plants contain a mix of both.
• For example, waxy corn starch is nearly 100% amylopectin and is used for clear and glossy sauces.
• Potato starch has large granules, gelatinizes easily
• Rice starch is small-grained, often used in baby foods

Colloids

• A colloid is a mixture where tiny particle are dispersed in a substance without easy separation
• Examples being emulsions, foams and gels.
• Hydrocolloids is a colloid in which water is the medium with the dispersed particles being starch and gelatin
• Milk and gelatin are examples

Gels

• A gel is a semi-solid with liquid trapped in a 3d polymer network
• A gel forms by a chain of materials of jelly, amylose etc which form zones via hydrogen bonding and cross-linking
• Their texture depends on the concentration, the material, and also the temperature

Spherification Process

• Alginate is created through favored liquids and calcium for calcium-rich and creamy liquids
• It results in thing, fragile skins for flavored liquids and thick skins that last longer for calcium-rich

Thickeners

• Provides a thick texture without drastic changes in flavor.
• Starch, flour, pectin, and xanthan gum are common examples
• Their swelling nature can be used for sauces, soups, puddings, and dressings

Foams

• Foams are a mixture of gas bubbles
• Meringues is air with egg whites. Cream is air with whipped cream. Bread comes from C02
• To stablize it is required to have proteins, that form a film. You need sugars or acids, this is known as acidity. Also need low surface tension to prevent air bubbles from popping

Amino Acid Structure

• Central carbon (alpha) is bonded to four groups - an amino group, the carboxylic acid group, an hydrogen atom, and a side chain
• Side chain defines the identity of the amino acid.

Chemical Structure Factors

• Side chains indicate the behavior of acids. Non-polar side chains are hydrophilic and polar uncharged side chains form hydrogen bonds and are hydrophilic. Charged side chains form ionic interactions

Proteins

• Are stabilized by hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions. Hydrogen bridges use van der waals forces, weak attractions in close proximity

Protein Stages

• Primary stage is the sequence of acids. Secondary is local folding into alpha-helices or beta-sheets via hydrogen bonding. The tertiary aspect of folding of the side chains. and the quaternary is many polypeptide stages working as a functional protein.

Folding

• When folding, non-polar side chains can be folded away from the water and polar side ends can be folded with the other hydrogen interactions

Energy and States

• Proteins will exists in either a high or low energy state
• The protein exists within unfolded elements during reactions
• Energy is a core factor in what is present

Free Energy

• The change in Gibbs Free energy determines the rate of energy that is involved in the reaction
• Also determines if something in spontaneous

Thermal Heat

• Thermal heat can determine if it releases heat, often making a reaction feel warm, endothermic absorbs the heat making it feel cold.

Proetin Aggregation

• When misfolded proteins can stick to each other which causes them to act together, this means it must use low levels

Thermal Aggrevation

• Heating the egg proteins with the exposure of hydrophibic parts makes them interact by forming bonds this makes them create transparent networks

Hydrolosis

• Involves breaking glyscoidic bonds by using water. The water acts as a reactant, and the sugar is cleaved into its monosaccharide components

Peptide

• Yes they can, they are broken down by having water breaking down in amino acid residues. This reaction is catalysed by enzyme or during conditions

Energy Dependant

• Activation depends on energy which is dependat on the activation energy, high and low are used for it
• Diagrams can show the activation between peaks of when transition occurs

Reaction Rates

• Higher temps speed up as increased momentum is added to the equation
• Molecules are more likely to overcome activation barriers which leads to a higher reaction rate
• Can exist in two forms dependant on pH and how it shifts from its cycle from acidic and more basic states

Reactivity

• Depends on how the acids are involved and how influenced they are during reactions
• Also what their amino and carboxylic groups are with their surrounding environment

Maillard Reaction

• Needs to begin with reduced sugar being reactive and diverse in their complexity which leads to a higher count

Caramelisation

• Caramelisation happens through the process of heating, without aminos it'll have thermal decomposition.
• Also results if different flavours.
• Cooking triggers various reactions, creating flavours and scents.

Enzyme Properties

• Catalyst and free energy, enzymes provide alternative ways and increase rates through products
• Non catalyysed reactions differ with high usage compared non catalyzed actions
• Also enzyme is key within substrate/product action, an entity that catalyzes the reaction

Enzyme specificity

• When specific reactions are achieved, this provides specific activity
• When reactions occur enzymes can speed things up
• Environmental conditions, water, salt, and pressure are factors as increased or decreased usage affect a reaction
• Browning is primarily from amino acids, its caused by phenol

Enzymes

• An enzyme is used to gain energy, they provide multiple flavours and tastes. An amino can then be more versatile within the sugar levels being consistent .
• Factors can also limit it such as the sugars being inconsistent and the temperature as well.