Biological Science Overview

Chapter 2: Science Fiction, Bad Science, and Pseudoscience: Biochemistry, Water, and Cells

Learning Objectives

• Understand the differences between science fiction, bad science, and pseudoscience

• Biological hierarchy (review from Chapter 1)

• Atoms & Types of Bonds: Covalent, Ionic, and Hydrogen

• pH

• Properties of Water

• Biomolecules (Macromolecules)

• Eukaryotic & Prokaryotic Cells

Science Fiction, Bad Science, and Pseudoscience

Key Differences in Worksheet Format

Biological Hierarchy

• Organism: Organ systems work together in a functional organism.

• Population: A population consists of organisms of the same species.

• Community: The populations of different species that populate the same area make up a community.

• Ecosystem: A community together with the nonliving environment forms an ecosystem.

• Biosphere: Earth and all of its communities constitute the biosphere.

• Cellular Level: Atoms and molecules make up the cytoplasm and form organelles (e.g., nucleus and mitochondria).

• Chemical Level: Atoms join to form molecules; macromolecules are large molecules like proteins and DNA.

Terms to Know

• Matter: Anything that has mass and occupies space. Matter is composed of elements.

• Element: A substance that cannot be broken down into other substances by chemical reactions.

• Atom: The smallest unit of matter that still retains the properties of an element.

Periodic Table Comparison

• Elements are organized based on atomic number, symbol, atomic mass, and electronegativity.

• Example Elements:

  • Hydrogen (H)

  • Carbon (C)

  • Oxygen (O)

  • Each element's properties and relation to biological processes are crucial for understanding biochemistry.

Elements in the Human Body

Atomic Structure

• Atom Structure:

  • Nucleus: Composed of protons (positive charge) and neutrons (no charge).

  • Electrons: Negatively charged and form an electron cloud surrounding the nucleus responsible for chemical behavior.

• Mass Number Calculation:

  • Mass number = number of protons + number of neutrons

  • For Sodium: 23 (mass number) = 11 (atomic number, which is the number of protons) + 12 (number of neutrons).

Isotopes

• Notable Isotopes:

  • Carbon-12 (6 protons, 6 neutrons)

  • Carbon-13 (6 protons, 7 neutrons)

  • Carbon-14 (6 protons, 8 neutrons)

Chemical Bonds

Types of Bonds:

Summary: Three Types of Bonds

• Covalent Bond:

  • Strong bond formed when atoms share electrons to become more stable, forming a molecule.

  • Bond Strength: Strong

  • Example: H₂ molecule (hydrogen gas)

• Ionic Bond:

  • Attraction between two oppositely charged ions, forming an ionic compound.

  • Bond Strength: Strong

  • Example: Sodium chloride (NaCl)

• Hydrogen Bond:

  • Attraction between the slightly positively charged hydrogen atom of one molecule and the slightly negatively charged atom of another.

  • Bond Strength: Weak

  • Examples include water molecules (H₂O).

Covalent Bonds

• A covalent bond is formed by the sharing of a pair of valence electrons by two atoms.

  • Importance: They form the strong, stable backbone of biological molecules (like DNA, proteins, carbohydrates) creating structures essential for life and energy storage (fats).

• Types of Covalent Bonds:

  • Nonpolar Covalent Bond: Atoms share electrons equally.

  • Polar Covalent Bond: Atoms do not share electrons equally, resulting in a polar molecule.

Ionic Bonds Creation and Importance

• Atoms can strip electrons from one another, creating cations (positively charged ions) and anions (negatively charged ions).

• Importance: Ionic bonds provide structural stability and play roles in nerve signals and muscle contractions through electrolytes (e.g., Na⁺, K⁺, Ca²⁺, Cl⁻).

Hydrogen Bonds Characteristics

• Form from the attraction of one molecule's positively charged atom to another's negatively charged atom.

• Importance: These bonds contribute to water's properties, help maintain DNA structure, and influence protein shapes.

Properties of Water

• Water's structure allows it to perform several critical functions:

  • Acts as a solvent

  • Facilitates chemical reactions

  • Exhibits cohesion

  • Moderates temperature

• Molecular representation:

  • Water molecule (H2O) shows a polar arrangement which is key for its solvent properties.

The pH Scale

• Definition of pH: It reflects the relative amounts of hydrogen ions (H⁺) and hydroxide ions (OH⁻) in a solution.

• Acids: More H⁺ ions and fewer OH⁻ ions (pH < 7).

• Bases: More OH⁻ ions and fewer H⁺ ions (pH > 7).

• Neutral Solution: Equal amounts of H⁺ and OH⁻ (pH = 7, pure water).

Biological Macromolecules

• Macromolecules: Large polymers built from monomers; not all biological molecules are macromolecules.

  • Classes of Macromolecules:

  • Carbohydrates

  • Proteins

  • Nucleic acids

  • Note: Lipids do not consist of monomers and are not considered macromolecules but are still vital.

• Function of Carbohydrates: Main energy source; composed of carbon, hydrogen, and oxygen (chemical formula CH₂O).

Biological Macromolecules - Specific Types

Carbohydrates

• Types:

  • Monosaccharides: Single sugar units.

  • Disaccharides: Two sugar units.

  • Polysaccharides: Multiple sugar units.

• Digestion of Cellulose: Cellulose remains calorie-free; the human body cannot digest it due to lack of corresponding enzymes.

Proteins

• Made of carbon, oxygen, hydrogen, and nitrogen; composed of 20 different amino acids joined by peptide bonds.

• Essential Amino Acids: Eight amino acids must be obtained from diet as the body cannot synthesize them.

Lipids

• Function as stored energy, components of membranes, steroids, and hormones.

• Lipids are hydrophobic and are not considered true polymers.

Nutritional Aspects of Lipids

• Classified into fats and oils.

• Fats: Solid at room temperature (saturated), generally of animal origin.

• Oils: Liquid at room temperature (unsaturated), plant-derived.

Nucleic Acids

• Main types include RNA and DNA.

• Functions: RNA is essential for protein synthesis. DNA stores genetic information.

• Structure:

  • RNA: Single-stranded, contains ribose.

  • DNA: Double-stranded (double helix), contains deoxyribose, structured with nitrogen base pairs.

Cell Types

Eukaryotic vs. Prokaryotic

• Eukaryotic Cells:

  • Contain a true nucleus and membrane-enclosed organelles.

  • Found in complex multicellular organisms (e.g., animals, plants).

  • Genetic material (DNA) is housed within the nucleus.

• Prokaryotic Cells:

  • Simple and smaller, lack a nucleus, and do not possess membrane-bound organelles.

  • Nucleoid region contains circular DNA.

  • Examples include bacteria and archaea.