Biology Chapter 2: Properties of Water and Life

Biology 1 - Cells, Molecular Biology and Genetics (Biol 1000)

• Course offered by Dr. Michael Cardinal-Aucoin during Winter 2025 at York University
• Course code: Biol 1000

Building Blocks of Life

• Chemistry of Life is a fundamental topic
• Biological macromolecules include polymers, carbohydrates, lipids, proteins, and nucleic acids

Review Chapter 2

• Matter, elements, and atoms are building blocks
• Atoms consist of protons, neutrons, and electrons within a nucleus
• Atomic mass and number, isotopes, and valence electrons define an element's properties
• Ionic, covalent (non-polar and polar), hydrogen and Van der Waals forces are important types of chemical bonds
• Chemical reactions involve reactants, products, and reversible processes with equilibrium and specificity
• Properties of water include polarity, cohesion, adhesion, and high specific heat affecting reactions in biological processes

The Molecules of Life

• All cells are composed of four main biological macromolecules: carbohydrates, lipids, nucleic acids, and proteins.
• All have a carbon skeleton as a common component.
• The diversity of ways these molecules are put together leads to the multitude of forms and functions in living things
• Carbohydrates, lipids, proteins, and nucleic acids perform diverse functions at the cellular level

The Chemistry of Life

• About 20-25% of 92 elements are essential to life
• Carbon, hydrogen, oxygen, and nitrogen compose 96% of living matter.
• Remaining 4% includes calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium

Table 2.1: Elements in the Human Body

• Oxygen (O) accounts for 65.0% of body mass (including water).
• Carbon (C) amounts to 18.5%
• Hydrogen (H) comprises 9.5%
• Nitrogen (N) makes up 3.3%
• Calcium (Ca) is 1.5%
• Phosphorus (P) is 1.0% and so on (including other trace elements)

Water and Life

• Water is the biological medium on Earth where life originated.
• Most living organisms need water more than any other substance.
• Cells are primarily composed of water (70-95%).
• Water's abundance is vital for Earth's habitability

Summary

• Water's properties (e.g., expansion upon freezing, cohesion/adhesion, moderation of temperature, versatility as a solvent) are due to polarity and hydrogen bonding.
• The pH of water is tightly regulated in living systems.

The Backbone of Life

• Living organisms primarily consist of carbon-based compounds.
• Carbon's ability to form complex molecules is crucial to life's diversity, and is abundant in the cosmos.
• Proteins, DNA, carbohydrates, and other molecules forming living matter are based on compounds of carbon.

A note about formulae

• Aspartic acid is an amino acid, one of the building blocks of proteins.
• Aspartic acid has a chemical formula (C4H7NO4)
• Aspartic acid has a condensed structural formula as well as a Lewis Diagram and a Skeletal formula

Diversity of chemical functional groups constructed with carbon.

• Many different types of chemical functional groups can be attached to a carbon atom, and they define the properties of the resulting molecule.

The Molecules of Life

• Carbohydrates provide energy and structure.
• Lipids are diverse compounds and form membranes and function in many other roles.
• Nucleic acids comprise DNA and RNA that store information.
• Proteins are diverse in function and have important roles in structural support, as enzymes, transport, defence, hormones, and more.

Polymers

• Most biological macromolecules are polymers composed of repeated units (monomers).
• Proteins are chains of amino acids joined by peptide bonds.

Dehydration Synthesis

• Polymer construction involves dehydration synthesis (condensation reaction, forming a bond and releasing water).

Hydrolysis

• Polymer breakdown involves hydrolysis (adding water to break a bond).

Carbohydrates

• Simple sugars (monosaccharides) have a 1:2:1 ratio of C:H:O. They include glucose, fructose, ribose, sucrose, lactose, maltose.
• They serve as energy sources and structural components in organisms.

Polysaccharides

• Long chains of monosaccharides (e.g., starch, glycogen, cellulose, chitin).
• Starch is the main storage polysaccharide in plants, glycogen in animals, cellulose and chitin for structural support.

Lipids

• Lipids aren't polymers, but are grouped based on hydrophobic properties.
• Types include neutral fats, phospholipids, and steroids.

Neutral fats

• Store energy
• Insulate from cold
• Protect internal organs (e.g., triglycerides)

Phospholipids

• Major components of cell membranes
• Have hydrophobic tails and hydrophilic heads

Steroids

• Components of cell membranes (e.g., cholesterol)
• Components of vitamins (e.g., vitamin D)
• Components of hormones (e.g., growth, sex hormones)

Nucleic Acids

• Polymers composed of nucleotide subunits (nitrogenous base, pentose sugar, and phosphate).
• DNA and RNA are major examples, storing and transmitting genetic information, and are held together by phosphodiester bonds through dehydration synthesis.
• The chemical structure of DNA and RNA are important for their function.
• The Central Dogma demonstrates how DNA is transcribed into RNA, which is translated into protein.

Proteins

• Polymers of amino acid subunits, essential to nearly all life processes.
• Amino acids have a common structure with varying "R" groups, impacting unique characteristics.
• Essential amino acids must be obtained from diet.
• Proteins have four levels of organization: Primary (sequence), Secondary (a-helices and β-sheets), Tertiary (3D folding), and Quaternary (interactions of polypeptide subunits):
• Protein function is dependent on their structure.

Denaturation

• Tertiary structure dictates protein function.
• Chemical treatment or heat can denature protein (unfolding), causing disruption of bonds and losing functionality.

Quaternary structure

• Interaction of multiple polypeptide chains to create a larger functional protein.
• Hemoglobin is an example of a quaternary protein

Protein Form and Function

• Protein's 3D structure dictates its function(s)

Amino acid substitution

• Small changes in amino acid sequence can significantly affect protein function, as demonstrated by sickle cell anemia.

Proteins- Pathogens: Prions

• Prions are misfolded proteins that propagate by inducing normal proteins to misfold.
• Prion diseases involve accumulation of prion proteins in the infected tissues.

Summary

• Key concepts from the material presented, covering various biological macromolecules and their roles in living systems.