Chemistry of Life – Study Notes

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Chemistry of Life

Introduction to the Chemistry of Life

The chemistry of life explores the molecular foundations of living organisms, focusing on the structure, function, and interactions of biological macromolecules. Understanding these molecules is essential for comprehending biological processes and the basis of life itself.

Biology is the study of living organisms and their interactions with each other and their environments.
The scope of biology includes the molecular, cellular, and organismal levels.

Water: The Universal Solvent

Water is the most abundant molecule in living organisms and plays a critical role in biological processes due to its unique chemical properties.

Water makes up about 60-70% of the total body weight in organisms.
It is a polar molecule: the oxygen end has a partial negative charge, and the hydrogen end has a partial positive charge.
Polar molecules can attract and repel each other, leading to hydrogen bonding.
Hydrophilic molecules (e.g., table salt/NaCl) are polar and dissolve in water.
Hydrophobic molecules (e.g., oils) are non-polar and do not mix with water.

Organic Molecules in Living Organisms

Four major classes of organic macromolecules are found in living organisms, each with distinct structures and functions.

Carbohydrates
Lipids
Proteins
Nucleic Acids

Macromolecule	Composition
Carbohydrates	C, H, O
Lipids	C, H, O
Proteins	C, H, O, N
Nucleic Acids	C, H, O, N, P

Making and Breaking Down Organic Molecules

Dehydration reaction: Removal of water to link subunits into larger molecules.
Hydrolysis reaction: Addition of water to break larger molecules into subunits.

Carbohydrates

Structure and Function

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, typically in a 2:1 ratio of hydrogen to oxygen. They serve as energy sources and structural components.

Monosaccharides: Simple sugars (e.g., glucose, galactose).
Disaccharides: Two monosaccharides joined together (e.g., maltose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose).
Function as short- and long-term energy storage.

Example:

Glucose is the main sugar found in human blood and is used by cells as an immediate energy source.
The brain requires a continuous supply of glucose due to its high energy demands.

Polysaccharide	Source	Function
Starch	Plants	Energy storage (fewer side branches than glycogen)
Glycogen	Animals (liver)	Energy storage
Cellulose	Plants	Structural (cell walls, indigestible by humans)

Lipids

Structure and Types

Lipids are hydrophobic, non-polar molecules that do not dissolve in water. They function as energy storage, components of cell membranes, and signaling molecules.

Fats and oils: Composed of glycerol and fatty acids.
Phospholipids: Contain a phosphate group, with a polar hydrophilic head and non-polar hydrophobic tail.
Steroids: Lipids with four fused carbon rings (e.g., cholesterol, sex hormones).

Fats vs. Oils

Type	Origin	State at Room Temp	Function
Fats	Animal	Solid	Long-term energy, insulation, organ protection
Oils	Plant	Liquid	Energy storage

Saturated, Unsaturated, and Trans Fats

Saturated fatty acids: No double bonds between carbon atoms; saturated with hydrogen.
Unsaturated fatty acids: One or more double bonds in the carbon chain.
Trans fats: Artificially formed by partial hydrogenation; associated with health risks.

Example:

Saturated fats and trans fats contribute to atherosclerosis (hardening of arteries due to plaque buildup).

Phospholipids

Main components of cell membranes.
Form bilayers with hydrophilic heads facing outward and hydrophobic tails inward.

Steroids

Cholesterol is a precursor for sex hormones (testosterone, estrogen).
Structure: Four fused carbon rings.

Proteins

Structure and Function

Proteins are polymers of amino acids and perform diverse functions, including support, catalysis, transport, defense, signaling, and motion.

Amino acids: Subunits of proteins, each with a central carbon, amino group, carboxyl group, and variable side chain.
Proteins can denature (lose shape and function) due to changes in environment.

Levels of Protein Structure

Primary structure: Linear sequence of amino acids.
Secondary structure: Localized folding into alpha helices and beta sheets.
Tertiary structure: Overall 3D shape of a single polypeptide.
Quaternary structure: Combination of multiple polypeptides (rare).

Example:

Hemoglobin (transport), antibodies (defense), insulin (hormone).

Nucleic Acids

Structure and Function

Nucleic acids are polymers of nucleotide subunits and are responsible for storing and transmitting genetic information.

DNA (deoxyribonucleic acid): Double-stranded, stores genetic information.
RNA (ribonucleic acid): Single-stranded, involved in protein synthesis.
Mutations in DNA can lead to changes in proteins (e.g., sickle-cell anemia).

Nucleotide Structure

Each nucleotide consists of a nitrogen-containing base, a phosphate group, and a sugar.

Bases in Nucleic Acids

Base	Type
Adenine (A)	Purine (double-ring)
Guanine (G)	Purine (double-ring)
Cytosine (C)	Pyrimidine (single-ring)
Thymine (T)	Pyrimidine (single-ring, DNA only)
Uracil (U)	Pyrimidine (single-ring, RNA only)

In DNA: A pairs with T, G pairs with C.
In RNA: A pairs with U, G pairs with C.

DNA vs. RNA Comparison

Feature	DNA	RNA
Bases	A, G, C, T	A, G, C, U
Strands	Double-stranded	Single-stranded
Function	Genetic information storage	Protein synthesis

ATP: The Energy Currency

ATP (adenosine triphosphate) consists of adenosine (adenine + ribose) and three phosphate groups.
When energy is needed, ATP loses a phosphate group, forming ADP and releasing energy.

Equation:

Summary Table: Macromolecules

Macromolecule	Subunit	Function
Carbohydrates	Monosaccharides	Energy storage, structure
Lipids	Fatty acids, glycerol	Energy storage, membranes, signaling
Proteins	Amino acids	Support, enzymes, transport, defense, hormones, motion
Nucleic Acids	Nucleotides	Genetic information, protein synthesis

Additional info: These notes expand on the original slides and handwritten content to provide a comprehensive overview suitable for college-level study in introductory biology or biochemistry. All tables and explanations are reconstructed and clarified for academic completeness.