Biology Chapter on Carbohydrates and Evolution

Nature of Science

• Biology aims to understand the living world, encompassing various specialties and interconnected with other scientific disciplines.
• Science employs a systematic approach involving observation, logic, and experimentation, driven by the scientific method.
• The scientific method begins with observations leading to questions, followed by the formulation and testing of hypotheses via experimentation.
• Data is then collected, analyzed, and used to draw logical conclusions.
• A hypothesis is a testable and falsifiable tentative explanation for an observation, tested through controlled experiments where most variables remain constant except for a single variable being changed.
• Scientific facts are observable and measurable phenomena agreed upon by experts.
• Scientific theories provide comprehensive explanations of natural phenomena, integrating multiple hypotheses, including examples such as cell theory, the theory of evolution, and the chromosomal theory of inheritance.
• Scientific laws are descriptions of consistently observed phenomena but do not explain the underlying reasons.

Characteristics of Living Organisms

• Living organisms are composed of membrane-bound cells.
• All organisms are capable of reproduction.
• All organisms process hereditary information (genes) and environmental information.
• Organisms acquire and use energy to survive.
• Populations of organisms evolve over time.

Life on Earth

• All living organisms are composed of one or more cells, replicate, use matter and energy, process information, and evolve over multiple generations.
• All cells arise from pre-existing cells, and crucial figures such as Robert Hooke, Anton van Leeuwenhoek, and Louis Pasteur established this concept.
• Genetic information is stored in DNA within chromosomes, the fundamental units of inheritance.
• DNA structure involves a double helix made of four nucleotides (A, T, C, G), allowing for accurate copying.

Chemistry of Life

• Life is fundamentally based on chemistry, and all living organisms share atomic structures with essential elements such as carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).
• Essential chemical bonds in living organisms include: covalent (polar and non-polar), ionic, and hydrogen bonds.
• Biological molecules, such as proteins, lipids, carbohydrates, and nucleic acids, are composed of macromolecules and their structures dictate their functions.

Water

• Water is essential for life, as it constitutes a significant portion of living cells (70%-75%).
• Water's properties, like polarity, cohesion, adhesion, high specific heat, and high heat of vaporization, are crucial for maintaining life functions.
• Water facilitates various metabolic processes and biological reactions as a solvent and reactant.
• Water is a key solvent in biological systems, capable of dissolving polar and charged molecules.

Acids, Bases and pH

• Acids release protons (H+) increasing hydrogen ions, while bases accept protons decreasing the concentration of hydrogen ions.
• pH is a measure of acidity or basicity, and buffers maintain homeostasis in biological systems by resisting changes in pH.

Carbohydrates

• Carbohydrates play critical roles in cell structure, function, and energy storage.
• They are classified as monosaccharides (single sugars), disaccharides (double sugars), and polysaccharides (many sugars).
• Common examples include glucose, fructose, and sucrose, as well as starch and glycogen.
• Functional groups like hydroxyl groups contribute to carbohydrate properties.

Lipids

• Lipids, hydrophobic molecules, play crucial roles in creating cell membranes, energy storage, and signaling.
• Fats (triglycerides) are composed of glycerin and three fatty acids; they are used for energy storage.
• Sterols, like cholesterol, have a four-ring structure, crucial for membrane fluidity and hormone precursors.
• Phospholipids are amphipathic, having both hydrophilic and hydrophobic parts, essential components of cell membranes.

Selective Permeability of Membranes

• The plasma membrane's composition of phospholipids ensures a selective barrier for certain molecules.
• Small, nonpolar molecules easily pass through, while ions and large polar molecules require specific transport mechanisms such as facilitated or active transport.
• The fluid mosaic model describes the cell membrane's structure and dynamic characteristics.

Bulk Transport

• Substances, both large and small, may pass into or out of the cell via endocytosis (bringing substances into the cell) and exocytosis (releasing substances out of the cell or bringing them through vesicles).
• Types of endocytosis include phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis.

Cell Types Overview

• Prokaryotic cells lack a nucleus and membrane-bound organelles; their DNA is located in the nucleoid; examples include bacteria.
• Eukaryotic cells have a membrane-bound nucleus and various organelles; examples include animal and plant cells.
• Basic cell components include: proteins to carry out tasks, nucleic acids to hold genetic information, and carbohydrates as both an energy source and a structural component.

Cytoskeleton

• The cytoskeleton maintains and modulates cell shape and movement via actin filaments (microfilaments), intermediate filaments, and microtubules.
• These protein filaments are organized into a network and are essential for intracellular transport, cell division, and maintaining overall cell shape.

Cell Cycle and Mitosis

• Cell cycles are a crucial component of cellular processes, involving phases like interphase (G1, S, G2) and mitosis (prophase, prometaphase, metaphase, anaphase, telophase), leading to the formation of new cells via division.
• Mitosis is a form of cell division producing two genetically identical daughter cells from one parent cell.
• Cytokinesis is the physical separation of the cytoplasm to complete cell division.

Cell Cycle and Meiosis

• Meiosis is a form of cell division resulting in four genetically distinct daughter cells with half the number of chromosomes of the parent cell.
• Meiosis occurs in reproductive cells (gametes) to ensure genetic diversity and variation among offspring.
• Meiosis I and II involves several phases similar to mitosis, but they also involve crossings over and independent assortment.

Chemical Evolution and Mendelian Genetics

• Early chemical evolution involved the possibility of polymerizations and macromolecule formations.
• Mendelian genetics describes the principles of inheritance, including concepts like genes, alleles, genotypes, and phenotypes, using a model system focused on traits of garden peas.
• Mendel's rules outline predictable patterns of inheritance in traits, showcasing complete and incomplete dominance, codominance, and multiple alleles.

Evolution by Natural Selection

• Evolution is the process of change in heritable traits of biological populations over successive generations.
• Natural selection is a mechanism of evolution where heritable traits increasing reproductive success become common in populations over time.
• Evolution is driven by variation within a population where certain traits provide advantages in surviving and reproducing.

Protein Structure and Function

• Proteins are polymers of amino acids, built and folded into specific shapes based on their primary structure (linear sequence of amino acids).
• Protein structure is categorized into multiple levels: primary, secondary (α-helix, β-sheets), tertiary, and quaternary.
• Protein structure determines the function of the protein in living organisms; proteins are involved in vital functions like catalysis, transport, structural support, and immune defense.

How Enzymes Work

• Enzymes, proteins, act as catalysts speeding up reaction rates in living organisms; they are specific to the reactions they perform.
• Enzymes work by lowering the activation energy, a crucial parameter.
• Feedback inhibition regulates enzyme activity, preventing overproduction of a certain molecule in processes.

Introduction to Nucleic Acids

• DNA and RNA are the two fundamental types of nucleic acids holding genetic information.
• DNA has two polynucleotide chains that are antiparallel and held together by complementary base pairings (adenine with thymine, and guanine with cytosine).
• RNA is a single strand-based nucleic acid with different structural arrangements and types (messenger RNA, ribosomal RNA, and transfer RNA) performing a multitude of functions.

Energy in Biological Systems

• Energy is crucial for life processes, and enzymes facilitate these critical biochemical conversions.
• The different types of energy include heat, chemical energy released during hydrolysis (ATP), and kinetic energy.
• Energy transfer often involves the movement of electrons or phosphate groups between molecules and metabolic processes.

Explore the crucial roles of carbohydrates in cells, including their functions in energy storage, cell identity, and photosynthesis. Delve into the principles of evolution, focusing on natural selection, genetic drift, and examples such as Mycobacterium tuberculosis and Galapagos finches.