Module 1: Introduction to Biology and the Chemistry of Life

Importance of Biology

Biology is a field of immense relevance to our everyday lives, impacting various facets of human existence and global health.
Medical advances: Studying biology is foundational for progress in medicine and healthcare.
Biodiversity challenges: Biology addresses the critical issues related to the decreasing rate of biodiversity globally.
Biotechnology advances: Biological research fuels the growth of biotechnology, which applies biological systems to technological solutions.

What is Biology?

Definition: Biology is the study of life and the study of living organisms.
Etymology: The word "Biology" is derived from Greek or Latin roots:
- bios-: Meaning life.
- -logia: Meaning science, study, or knowledge.
Scientific Objective: It is a science dedicated to understanding, explaining, integrating, and describing the world of living things.

Properties of Living Organisms

All living organisms share a specific set of characteristics and properties:

Cellular Organization: Organisms are composed of cells. They are characterized by being highly organized and complex.
Sensitivity: Living things move and respond to their environment.
Growth, Development, and Reproduction: Organisms have the capacity to grow, develop through lifecycle stages, and reproduce to create new life.
Energy Utilization: Living things obtain and use energy to sustain their functions.
Homeostasis: Organisms maintain internal balance and stable conditions despite external changes.
Evolutionary Adaptation: Living things possess mechanisms that allow for evolutionary adaptation over generations.
Genetic Blueprint: They contain a blueprint (genetic material) that defines their characteristics.

Levels of Biological Organization

Biological organization is hierarchical, where each level builds upon the level below it, often demonstrating new features (emergent properties):

1. Cellular Level:
- Atoms
- Molecules
- Compounds
- Organelles
- Cells
2. Organismal Level:
- Cells
- Tissues
- Organs
- Organ Systems
3. Population Level:
- Population
- Species
- Biological Community
4. Ecosystem Level:
- Includes the biological community plus the physical habitat (soil, water, and atmosphere).
5. The Biosphere:
- The entire planet thought of as a single ecosystem.

Introduction to the Chemistry of Life

Chemistry Definition: Chemistry is the study of how matter interacts.
Relevance: Understanding standard chemical terminology is essential to describe how living things work.
Elements: A substance that cannot be separated into simpler substances by chemical reactions. It is a pure substance consisting of one type of atom.
Compounds: A combination of two or more different elements.
Atoms: The basic unit of matter (derived from a term meaning "unable to cut"). Each atom has specific properties that differentiate one element from another.
Molecules: Consist of two or more atoms joined together by molecular bonds.

Elements Required for Life

Life requires a total of $25$ elements.
Major Elements (96%): Carbon ( $C$ ), Hydrogen ( $H$ ), Nitrogen ( $N$ ), and Oxygen ( $O$ ).
Minor Elements (4%): Sulfur ( $S$ ), Phosphorus ( $P$ ), Calcium ( $Ca$ ), and Potassium ( $K$ ).
Elemental Weight (99.9% wt): Living things are composed of 99.9% by weight of six specific elements: $C$ , $H$ , $N$ , $O$ , $P$ , and $S$ . The remaining percentage is made up of seventeen other elements.

Subatomic Particles and Atomic Structure

Subatomic Particles: Atoms are composed of smaller particles:
- Protons: Positively charged particles ( $+$ ).
- Electrons: Negatively charged particles ( $-$ ).
- Neutrons: Neutral particles with no charge.
Nucleus: The central part of the atom containing protons and neutrons.
Isotopes: Atoms of the same element that have the same number of protons but a different number of neutrons.
Chemical Bonding: Two atoms connect to each other through the interaction of electrons.

Chemical Bonds in Biology

A. Weak Bonds: These involve interactions between a positive ( $+$ ) pole and a negative ( $-$ ) pole.
- Example: Hydrogen Bonds.
B. Strong Bonds: These form when atoms share one or more pairs of electrons. They are very stable and strong, forming the basis of molecules.
- Covalent Bonds: Formed by sharing electrons; may result in single, double, or triple bonds.
- Ionic Bonds: Involve the complete transfer of an electron from one molecule (or atom) to another.

Water and Its Biological Importance

Polarity: Water is a polar compound.
Composition: Water is made up of hydrogen ions ( $H^+$ ) and hydroxide ions ( $OH^-$ ).
Water Content in Human Tissue:
- Bone: $20\%$ water.
- Brain: $85\%$ water.
Ionization: Water ionizes at times, producing $H^+$ (which is acidic) and $OH^-$ (which is basic). These properties are used in the measurement of pH.
Functions:
- Acts as the universal solvent.
- Serves as the extracellular medium in the cytoplasm.

Solubility: Hydrophilic vs. Hydrophobic

Hydrophilic: Means "water loving"; these substances dissolve in water.
Hydrophobic: Means "water fearing"; these substances do not dissolve in water.

Acids, Bases, and Buffers

Acids: Contain a higher concentration of $H^+$ ions than pure water. They have a pH below $7$ .
Bases: Contain a lower concentration of $H^+$ ions than pure water. They have a pH above $7$ .
Buffer: A weak acid or base that can react with strong acids or bases to prevent sharp changes in pH levels.

Biomolecules: The Four Groups of Organic Compounds

There are four primary groups of organic compounds essential to life:

1. Carbohydrates

Name Origin: The name literally means "hydrates of carbon."
Composition: Primarily composed of Carbon ( $C$ ), Hydrogen ( $H$ ), and Oxygen ( $O$ ).
General Formula: Most have the general formula $C_n H_{2n} O_n$ or $(CH_2O)_n$ .
Structure: Represented as $H-C-OH$ .

2. Proteins and Amino Acids

Amino Acids: The building blocks of protein.
Proteins: Polymers of amino acids that are linked together by peptide bonds.

3. Nucleic Acids and Nucleotides

Function: Nucleic acids serve as the primary repositories and transmitters of genetic information.
Two Types:
- Deoxyribonucleic Acid (DNA).
- Ribonucleic Acid (RNA).
Components of Nucleotides:
- Sugars (Ribose in RNA and Deoxyribose in DNA).
- Phosphate group.
- Nitrogenous bases: Purines or Pyrimidines ( $A, C, T, G, U$ ).

4. Lipids

Definition: A group of heterogeneous compounds characterized by their unique solubility properties.
Solubility: They are insoluble in water but soluble in organic solvents such as ether, chloroform, and benzene.

Enzymes

Definition: Enzymes are protein catalysts that increase the rate (velocity) of chemical reactions without being changed or consumed in the overall process.
Metabolic Role: Enzymes direct all metabolic events within the organism.
Properties:
- They are protein-based.
- They increase reaction velocity.
- They are not consumed during the reaction they catalyze.
Nomenclature (Recommended Name): Most enzyme names use the suffix "-ase" attached to either the substrate or the action performed:
- Based on Substrate: Glucosidase, Urease, Sucrase.
- Based on Action: Lactate dehydrogenase, Adenylyl cyclase.