Biology I - Introduction to Biomolecules
Lectures Biology I 2025
English Medical Program, Faculty of Medicine, University of Thessaly
Instructor: Rodopi Stamatiou
rstamatiou@uth.gr
Objectives
Learn about the following key concepts:
Atoms: definition, structure, and properties
Chemical bonds: types including covalent, ionic, hydrogen, and Van der Waals
Biomolecules: categories and formation reactions
Monomers and polymers
Blood groups: ABO system and Rhesus factor
Contents
Atoms
Chemical Bonds
Biomolecules
Monomers
Blood Groups
Atoms
Definition: Atoms are the basic particles of chemical elements.
Structure of an Atom:
Composed of a nucleus containing:
Protons (positively charged)
Neutrons (no charge)
Electrons (negatively charged) are bound to the nucleus by electromagnetic force.
Key Points:
Atoms are characterized by the number of protons.
Example: An atom with 11 protons is sodium, one with 29 protons is copper.
Isotopes: Atoms with the same number of protons but differing numbers of neutrons are called isotopes.
Nucleus of an Atom
The nucleus constitutes more than 99.94% of the atom's mass.
Types of particles:
Protons: positively charged
Neutrons: no charge
Electrons:
Bind to the nucleus due to opposite charges.
If protons = electrons, the atom is neutral.
If electrons > protons, the atom becomes negatively charged (anion).
If electrons < protons, the atom becomes positively charged (cation).
The Hydrogen Atom
Isotopes of Hydrogen:
Protium: 1 proton, no neutrons
Deuterium: 1 proton, 1 neutron
Tritium: 1 proton, 2 neutrons
Tritium is used as a tracer for biochemical research and studies in animal metabolism and groundwater transport.
The Carbon Atom
Carbon Isotopes:
Carbon-12: 6 protons, 6 neutrons (atomic weight = 12)
Carbon-13: 6 protons, 7 neutrons
Carbon-14: 6 protons, 8 neutrons
Radiocarbon dating:
A method to determine the age of organic materials up to 60,000 years based on the decay of carbon-14. Developed by Willard Libby in the late 1940s.
Solution Formulas
Concentration Formula:
C1V1 = C2V2Atomic Weight:
Mass is relative to the mass of the hydrogen atom.
Measured in daltons.
Avogadro’s Number:
One proton or neutron weighs grams.
1 gram of hydrogen contains atoms.
Mole Definition:
1 mole is equal to x grams of a substance (where x is the molecular mass of that substance).
1M represents one mole in 1 liter of solution (e.g., 1M glucose = 1 mole or 180g in 1 liter).
Nature of Elements
Elements Found in Nature:
There are 90 different elements.
Living organisms are composed primarily of 4 elements: Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N)—making up 96% of their total weight.
Role of Ions and Molecules
Significance of Na and K Channels:
Vital in kidney functions and neuron synapses.
Oxygen:
Most abundant molecule in the human body.
Chemical Bonds
Covalent Bonds:
First defined by Irving Langmuir in 1919.
Atoms share electrons, forming a stable bond.
Critical Distance:
Correct distance is essential to manage the attraction between nuclei and bonding electrons versus repulsion between electrons and nuclei.
The correct distance between the atoms plays critical role
Attraction between nuclei+bonding electrons
Repulsion between the 2 nuclei as well as between the 2 electrons
Ionic Bonds:
Formed through electrostatic attraction between oppositely charged ions resulting from the transfer of one or more valence electrons from one atom to another.
The atom losing electrons becomes a cation (positive ion)
The atom gaining electrons becomes an anion (negative ion).
Comparison:
In covalent bonding, electrons are shared
in ionic bonds, electrons are donated.
Extra
Covalent bonds are 100x stronger in solution from ionic bonds
Covalent bonds have enzymes to break them down
Ionic bonds can’t be broken down by enzymes => too strong
Hydrophobic and Hydrophilic Molecules:
Hydrophilic: Molecules forming hydrogen bonds and interacting with water (soluble).
Hydrophobic: Molecules that do not form hydrogen bonds and avoid water (insoluble).
Hydrogen bonds facilitate enzymatic catalysis: Water molecules cluster around substrates and enzymes, promoting formation of enzyme-substrate complexes in aqueous environments.
Van der Waals Forces:
These are the weakest types of bonds and depend significantly on the distance between atoms.
Relative Strength of Bonds:
Covalent bonds are approximately 100 times stronger than ionic bonds in solution.
Destruction of covalent bonds often requires enzymes.
Triple bond> double bond>single bond
ionic > covalent >hydrogen
=================>
stronger
Biomolecules
We have
Carbohydrates
Proteins
Nuclei acids
Lipids
Formed through Covalent Bonds:
Biomolecules consist of monomers linked by covalent bonds.
Condensation and Hydrolysis
Condensation Reaction:
Linking of monomers with the release of water ().
Hydrolysis Reaction:
Water uptake causing the breakdown of polymers.
Macromolecules
Small molecules covalently link to form macromolecules which are then assembled into complexes through non-covalent interactions.
Lipids
Types:
Saturated: Carbon chains with only single bonds ().
Unsaturated: At least one double bond ().
Amphipathic: Possess both hydrophilic heads and hydrophobic tails, such as phospholipids.
Functions:
Serve as energy sources
Basic structural components of cell membranes.
Amino Acids
Structure:
Composed of a constant amino group and carboxyl group, with a variable side chain.
Classification:
Polar Uncharged Amino Acids: Can form hydrogen bonds with water.
Charged Amino Acids: Have either an ionized carboxyl group (negative charge) or a protonated nitrogen (positive charge).
Cysteine: Unique for its thiol group () which can form disulfide bonds (H_2OC(H2O)nH_2O$$).
Role of Polysaccharides
Classification:
Heteropolysaccharides: Composed of different monomers.
Homopolysaccharides: Composed of the same monomer.
Functions include storage (e.g. starch, glycogen) and structural (e.g. cellulose).
Diabetes
Definition: A disease characterized by high blood glucose levels, impacting energy utilization in the body.
Insulin: Hormone produced by the pancreas to help glucose enter cells. Lack of insulin or improper utilization leads to excess blood glucose.
Blood Groups
ABO System:
Discovered by Karl Landsteiner (1900).
Based on antigens present on erythrocyte membranes, with genes located on chromosome 9.
Antigens: A and B are dominant, O is recessive.
Rhesus System:
Antigens D, C, c, E are significant in transplantation and hemolytic reactions.
Rh factor indicates the presence (+) or absence (−) of the D antigen in blood.
Multiple blood group antigens (a total of over 50) defined over time, with significant implications in transfusions and hemolytic disease of the newborn.
Bombay Blood Group:
Rare group lacking H antigen; individuals produce antibodies against it.
Transfusion Compatibility
Blood Group Compatibility Chart:
Recipients and donors must match to prevent adverse reactions (e.g. AB+ can receive from A+, O-, etc.).
Blood Group Testing
Agglutination Test:
Mixing blood drops with specific antibodies to determine blood type. If agglutination occurs, it indicates the presence of corresponding antigens.
Conclusion
Questions?
Diagram links and images/errors in transcription may need review for enhanced understanding.