The slides discuss *chemical bonds* and their role in holding atoms together, focusing on different types of bonds:
1. *Chemical Bonds*:
- *Attractive forces* between atoms, which can be strong or weak.
- Bonds allow interactions between biological molecules and can either *share electrons (covalent bonds)* or not (*non-covalent bonds*).
- These bonds determine the *properties and functions* of biomolecules.
2. *Types of Chemical Bonds*:
- *Covalent Bonds*: Form when electrons are shared between atoms.
- *Ionic Interactions*: Occur when a positively charged ion (cation) is attracted to a negatively charged ion (anion).
- *Hydrogen Bonds*: The interaction of a partially positively charged hydrogen atom (e.g., in water) with unpaired electrons from another atom.
- *Van der Waals Interactions*: A weak, nonspecific attractive force that occurs when atoms are closely aligned.
3. *Bond Strength*:
- The strength of these bonds is measured by the energy required to break them, known as *bond energies*. Covalent bonds are generally stronger than non-covalent interactions.
The slide also shows illustrations of these bonds and provides a comparison of their relative energies.
*Molecular Complementarity*:
1. *Lock-and-Key Model*: Different molecules fit together like a lock and key. This concept helps in the specific binding of biomolecules within cells.
2. *Complementary Interactions*: The shapes, charges, polarity, and hydrophobicity of two protein surfaces allow for weak interactions that, when combined, form strong interactions and tight binding.
- *More interactions → Better fit → Higher affinity*
3. *Purpose*: Molecular complementarity ensures the *specificity* between macromolecules in a cell.
4. *Molecular Complementarity in Biomolecules*:
- The binding of proteins occurs via multiple non-covalent interactions.
- The complementarity between protein molecules (as shown in images) allows them to bind tightly compared to non-complementary proteins.
5. *Example*: The images display how adenine (A) and thymine (T) in nucleic acids interact through complementary shapes, contributing to the stability of molecular complexes.
This concept is fundamental for understanding how molecules interact with high specificity in biological systems.
*Chemical Compounds in Cells*:
1. *Organic Compounds*:
- Contain Carbon and Hydrogen (hydrocarbons).
- Usually associated with living organisms.
- Examples include proteins, amino acids, nucleotides, lipids, and fatty acids.
2. *Inorganic Compounds*:
- Do not contain Carbon.
- Examples include salt (NaCl), sand (SiO₂), ammonia (NH₃), and water (H₂O).
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*Major Chemical Composition of a Cell*:
1. *Water*: 70 - 85% of the total cell mass.
2. *Proteins*: 10 - 20% of the total cell mass.
3. *Nucleic Acids*: 5 - 7% of the total cell mass.
4. *Lipids*: 2 - 4% of the total cell mass.
5. *Carbohydrates*: 2 - 3% of the total cell mass.
These compounds make up the basic chemical structure of cells, with water being the most abundant, followed by proteins and nucleic acids.
*Basic Terms*:
- *Polar*: Molecule with opposite charges at different ends.
- *Nonpolar*: Molecule with no charge separation.
- *Hydrophilic*: "Water-loving," soluble in water.
- *Hydrophobic*: "Water-fearing," repels water.
- *Amphipathic*: Molecule with both hydrophilic and hydrophobic parts.
- *Monomer*: Single unit that can combine to form larger molecules.
- *Polymer*: Large molecule made of repeating monomers.
- *Macromolecule*: Large, complex molecule, such as proteins or DNA.
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*Water*:
- *Cellular chemistry* and metabolism occur in the *cytosol*, a water-filled environment.
- *H₂O*:
- Polar molecule.
- Universal solvent.
- High-specific heat.
- Cohesive and surface tension.
- Facilitates movement in cellular structures.
Water is *essential for life* and plays a crucial role in cellular functions.
*Properties of Water*:
1. *Water is Polar*:
- Water molecules have partial charges; oxygen is negatively charged, and hydrogen is positively charged.
- Despite having partial charges, the molecule has no net charge.
- Polar molecules bond with each other through *cohesion*.
- Polar water molecules are good solvents and have the ability to absorb heat and cool down slowly.
2. *Hydrogen Bonding*:
- Water molecules form hydrogen bonds with each other or with other polar molecules.
- These hydrogen bonds occur between the positive hydrogen atoms of one molecule and the negative oxygen atoms of another, creating an interconnected structure.
*Properties of Water:*
1. *Water as a Universal Solvent:*
- Water is considered a universal solvent because polar molecules interact with it.
- Water is *hydrophilic* (water-loving), meaning it attracts other polar substances.
- Opposite charges (positive and negative) attract each other, and water can dissolve salts like NaCl by breaking them into ions.
2. *Cohesion, Adhesion, and Surface Tension:*
- *Cohesion*: Attraction between similar molecules (e.g., water molecules attract each other via hydrogen bonds), leading to surface tension.
- *Adhesion*: Attraction between water molecules and different molecules, such as the interaction between water and the surface of xylem cells in plants, helping water rise against gravity (capillary action).
- These properties enable water to flow through plant structures like roots and stems.
*Properties of Water:*
1. *Surface Tension:*
- Cohesion via hydrogen bonds causes water's surface tension, making it resist rupture when under stress.
- This allows organisms like the water strider to stay afloat on water, and it is crucial for biological processes like water movement in plants and drainage of tears from the eyes.
2. *Water Stabilizes Temperature:*
- Water's hydrogen bonds give it a high boiling point and high specific heat, meaning it takes more energy to change its temperature.
- This property helps regulate temperature in living organisms (homeostasis) and the environment.
*Biological Macromolecules (Biomolecules):*
- Key macromolecules include *Nucleic Acids*, *Proteins*, *Carbohydrates*, and *Lipids*.
*Dehydration and Hydrolysis:*
- *Dehydration* is a synthesis reaction where water is removed to join monomers into polymers (e.g., forming disaccharides).
- *Hydrolysis* is the reaction that breaks down polymers into monomers by adding water.
*Nucleic Acids:*
- Nucleic acids, like *DNA* and *RNA*, are key macromolecules essential for life and carry genetic information in cells.
- The monomers of nucleic acids are *nucleotides*, which consist of a nitrogenous base, a 5-carbon sugar, and a phosphate group.
- *Nucleotides* are linked by *5'–3' phosphodiester bonds*, which determine their directionality.
- Nucleotides contain *purines* (adenine, guanine) and *pyrimidines* (cytosine, thymine, uracil).
*DNA vs RNA:*
- *DNA*: Carries genetic information, remains in the nucleus, has a double helix structure, uses deoxyribose as sugar, and contains cytosine, thymine, adenine, and guanine.
- *RNA*: Involved in protein synthesis, leaves the nucleus, is usually single-stranded, uses ribose as sugar, and contains cytosine, uracil, adenine, and guanine.
*Proteins:*
- Proteins are linear polymers made of *amino acids* linked by *peptide bonds*.
- There are *20 amino acids* in nature.
- The *amino acid monomer* consists of a central carbon atom (Cα), an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom (-H), and a variable side chain.
*Proteins:*
- Proteins are formed by *peptide bonds* linking *amino acids*. These can form *polymers* like polypeptides from individual *monomers* (amino acids).
*Classification of Amino Acids by R Side Chains:*
- The *R side chains* on amino acids are very important as they:
- Determine the properties of the amino acid.
- Influence the properties of proteins that contain these amino acids.
- Dictate how the protein functions and how it folds.
- Examples include *Glycine, Alanine, Leucine, Methionine, Lysine*, and others, with distinct chemical structures influencing the protein's function.
Sure, here's the breakdown in English:
*Functions of Proteins*
Proteins have several essential functions in the body:
- *Catalysis*: Enzymes catalyze biochemical reactions, speeding up metabolic processes.
- *Transport*: Proteins like hemoglobin transport oxygen in the blood.
- *Structure*: Structural proteins like collagen and keratin provide structure in connective tissues, hair, and nails.
- *Motion*: Proteins such as myosin and actin are involved in muscle movement.
*Hierarchical Protein Structure*
Proteins have a hierarchical structure that defines their functionality:
- *Primary Structure*: The sequence of amino acids in a linear chain.
- *Secondary Structure*: Hydrogen bonding between amino acids leads to the formation of structures like alpha helices and beta-pleated sheets.
- *Tertiary Structure*: The protein folds into a more complex shape, with side-chain interactions stabilizing the structure.
- *Quaternary Structure*: Multiple polypeptide chains come together to form a functional protein.
*Carbohydrates:*
- *General chemical formula*: (C₆H₁₂O₆)ₙ, with a ratio of *C:H:O = 1:2:1* (carbon + water).
- *Primary functions*:
- Energy source and storage
- Cellular communication and recognition
- Structural components in biomolecules
- They are commonly referred to as *sugars*.
*Monosaccharides as Building Blocks:*
- *Monosaccharides* are simple sugars with one sugar unit.
- *Hexoses* (6 carbon atoms) and *pentoses* (5 carbon atoms) are key examples.
- *Examples of monosaccharides*:
- *Five-carbon sugars (pentoses)*: Ribose, Deoxyribose
- *Six-carbon sugars (hexoses)*: Mannose, Galactose, Glucose, Fructose
- Though all these sugars share the formula *C₆H₁₂O₆*, they have distinct biochemical properties.
*Disaccharides:*
- Formed by two monosaccharides linked via a *glycosidic bond* through a *dehydration reaction*. Example: *maltose*.
*Polysaccharides:*
- A long chain of monosaccharides linked by *glycosidic bonds*.
- Functions as an important energy source in *animals* and a structural component in *plants*.
- Can be *homopolysaccharides* (same type of monosaccharide) or *heteropolysaccharides* (different monosaccharides).
*Examples:*
- *Cellulose* (from plants, β-glucose, unbranched).
- *Amylose* (from plants, α-glucose, unbranched).
- *Amylopectin* (from plants, α-glucose, branched).
- *Glycogen* (from animals, α-glucose, branched).
These structures are key for energy storage and structural integrity in cells.
The slides cover chitin, chitosan, and lipids:
- Chitin and Chitosan (Polysaccharides)
- Chitin is composed of N-acetyl-D-glucosamine monomers.
- Chitosan is composed of D-glucosamine (non-acetylated) monomers.
- Found in various sources such as mushrooms, insects, squid pens, and crustacean shells (lobsters, prawns, crabs).
- Lipids
- Non-polar hydrocarbons, which are hydrophobic or amphiphilic.
- Functions:
- Energy storage.
- Insulation.
- Cellular signaling.
- Structural component of cell membranes.
- Types of Lipids:
- Fats and oils.
- Waxes.
- Phospholipids.
- Steroids.
The slides summarize key points about fats and oils:
- Fats and Oils Composition:
- Composed of fatty acids and glycerol, linked by an ester bond.
- Triacylglycerol (triglyceride) = 1 glycerol + 3 fatty acids.
- Fatty acids range from 4 to 36 carbon atoms, with 12–16 carbons being the most common.
- Types:
- Fats: Contain saturated fatty acids and are solid at room temperature.
- Oils: Contain unsaturated fatty acids and are liquid.
- Special Types of Fatty Acids:
- Trans fatty acids (Trans FA): Artificially hydrogenated, making them semi-solid and contributing to plaque deposition in arteries.
- Omega fatty acids (Omega FA): Essential fatty acids (e.g., Omega-3) that the human body cannot synthesize, but they are unsaturated and necessary for health.
The slides summarize Waxes and Phospholipids:
- Waxes:
- Composed of long-chain fatty acids (FAs) and long-chain alcohols.
- Linked by ester bonds.
- Hydrophobic, preventing water from sticking to surfaces.
- Examples: Candle wax, leaf coatings, and bird feathers repelling water.
- Phospholipids:
- Composed of 2 fatty acids + 1 glycerol + 1 phosphate group.
- Also called diacylglycerol.
- Major components of cellular membranes.
- Serve as precursors for intracellular signaling molecules.
- Amphiphilic: Have both hydrophobic (fatty acid tails) and hydrophilic (phosphate head) regions, enabling membrane formation.
Steroids Summary:
- Structure:
- Unlike typical lipids but share hydrophobic properties.
- Insoluble in water.
- Not linear, instead, they have a fused ring structure.
- Common Features:
- All steroids have four linked carbon rings.
- Some may have a short tail.
- Examples:
- Cholesterol: A crucial component of cell membranes.
- Cortisol: A steroid hormone involved in stress response.