Unit I Study Notes: Introduction to Biology, Chemistry of Life, and The Cell

Chapter 1: An Introduction to the Science of Life

Properties of Life

All living organisms share a set of fundamental properties that distinguish them from non-living matter. Understanding these properties helps define what it means to be alive.

• Order: Living things exhibit complex but ordered organization.

• Regulation: Organisms can adjust their internal environment to maintain homeostasis.

• Growth and Development: Information carried by genes controls the pattern of growth and development.

• Energy Processing: Organisms obtain and use energy to power activities and chemical reactions.

• Response to the Environment: Living things respond to environmental stimuli.

• Reproduction: Organisms reproduce their own kind.

• Evolutionary Adaptation: Populations evolve over generations as individuals with traits best suited to their environments have greater reproductive success.

Levels of Biological Organization

Life can be studied at various levels, from the smallest chemical building blocks to the entire biosphere.

• Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism → Population → Community → Ecosystem → Biosphere

Example: The human body is composed of cells (cellular level), which form tissues, organs, and organ systems, all functioning together as an organism within a population and ecosystem.

Major Themes in Biology

Several overarching themes unify the study of biology:

• Emergent Properties: New properties arise at each level of organization that are not present at the preceding level.

• Evolution: The process by which modern organisms have descended from ancient ancestors, explaining the unity and diversity of life.

The Scientific Method

Scientists use systematic methods to investigate the natural world and build reliable knowledge.

• Observation → Question → Hypothesis → Experiment → Data Collection → Analysis → Conclusion

• Data: Recorded observations or measurements.

• Scientific Literature: Published reports of scientific work.

Types of Scientific Ideas

• Hypothesis: A tentative explanation that can be tested.

• Theory: A broad explanation supported by a large body of evidence.

• Fact: An observation that has been repeatedly confirmed.

• Experiment: A controlled test of a hypothesis.

Experimental Design and Controls

Controlling variables is essential for reliable experiments.

• Control Group: The group not exposed to the experimental treatment; used for comparison.

• Positive Control: A group where a known response is expected.

• Negative Control: A group where no response is expected.

• Placebo: An inactive substance used to control for psychological effects.

• Blind Experiment: Subjects do not know which group they are in.

• Double-blind Experiment: Neither subjects nor experimenters know group assignments.

Data Presentation

Scientists use various types of graphs to communicate data:

• Bar Graph: Compares quantities across categories.

• Line Graph: Shows trends over time or continuous data.

• Pie Chart: Shows proportions of a whole.

• x-axis/y-axis: Axes of a graph; x is horizontal, y is vertical.

• Error Bars: Indicate variability or uncertainty in data.

Types of Scientific Studies

• Clinical Trial: Research study involving human volunteers.

• Observational Study: Observes subjects without intervention.

• Epidemiological Study: Examines patterns, causes, and effects of health and disease in populations.

• Double-blind Placebo-controlled Trial: Gold standard for testing interventions.

Critical Thinking and Scientific Claims

• Anecdotal Evidence: Personal stories, not reliable for scientific conclusions.

• Pseudoscience: Claims presented as scientific but lacking evidence or proper methodology.

• Critical Thinking: Evaluating information and arguments logically and systematically.

Reliable Sources of Information

• Peer Review: Evaluation of scientific work by others in the field.

• Primary Source: Original research articles.

• Secondary Source: Summaries or interpretations of primary sources.

Chapter 2: The Chemistry of Life

Atoms, Molecules, and Compounds

All living things are composed of molecules, which are made of atoms. The interactions of atoms and molecules underlie all biological processes.

• Atom: The smallest unit of an element, retaining its properties.

• Molecule: Two or more atoms held together by chemical bonds.

• Compound: A substance consisting of two or more elements in a fixed ratio.

• Chemical Reaction: The process of making and breaking chemical bonds, transforming substances.

• Reactant/Product: Substances present before/after a chemical reaction.

Chemical Elements and the Periodic Table

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

• Atomic Number: Number of protons in an atom.

• Atomic Weight: Average mass of an atom, accounting for isotopes.

• Symbol: One- or two-letter abbreviation for an element.

• Trace Element: Essential element required in minute quantities.

Structure of Atoms

• Subatomic Particles: Protons (positive), neutrons (neutral), electrons (negative).

• Nucleus: Central core containing protons and neutrons.

• Isotope: Atoms of the same element with different numbers of neutrons.

• Ion: Atom or molecule with an electrical charge due to loss or gain of electrons.

Chemical Bonds

• Covalent Bond: Atoms share electrons (can be single or double bonds).

• Ionic Bond: Attraction between oppositely charged ions.

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom.

• Polar/Nonpolar Bonds: Polar bonds have unequal sharing of electrons; nonpolar have equal sharing.

Properties of Water

• Cohesion: Water molecules stick together.

• Adhesion: Water molecules stick to other substances.

• Solvent: Substance that dissolves other substances; water is the universal solvent.

• Solution: Homogeneous mixture of two or more substances.

pH and Acidity

• pH: Measure of hydrogen ion concentration; scale from 0 (acidic) to 14 (basic).

• Acid: Substance that increases H+ concentration.

• Base: Substance that decreases H+ concentration.

• Buffer: Substance that minimizes changes in pH.

Equation:

$\mathrm{pH} = -\log_{10}[\mathrm{H}^+]$

Carbon and Organic Molecules

• Organic Compound: Molecule containing carbon and hydrogen.

• Functional Group: Group of atoms that participate in chemical reactions.

• Macromolecule: Large molecule (e.g., protein, nucleic acid, carbohydrate, lipid).

• Monomer/Polymer: Monomers are building blocks; polymers are chains of monomers.

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates

• Monosaccharide: Simple sugar (e.g., glucose, fructose).

• Disaccharide: Two monosaccharides joined (e.g., sucrose, lactose, maltose).

• Polysaccharide: Many monosaccharides (e.g., starch, glycogen, cellulose, chitin).

• Isomer: Compounds with the same formula but different structures.

Lipids

• Lipid: Hydrophobic molecule (e.g., fats, oils, steroids).

• Fatty Acid: Building block of many lipids.

• Triglyceride: Glycerol + 3 fatty acids.

• Phospholipid: Major component of cell membranes; forms bilayers.

• Steroid: Lipid with four fused rings (e.g., cholesterol, anabolic steroids).

• Hydrophobic: Repels water.

Types of Fats

• Saturated Fat: No double bonds; solid at room temperature.

• Unsaturated Fat: One or more double bonds; liquid at room temperature.

• Trans Fat: Unsaturated fat with trans double bonds; unhealthy.

• Omega-3 Fatty Acid: Essential unsaturated fat beneficial for health.

• Hydrogenation: Process of adding hydrogen to unsaturated fats to make them solid.

Proteins

• Amino Acid: Building block of proteins.

• Polypeptide: Chain of amino acids.

• Peptide Bond: Covalent bond between amino acids.

• Protein: Functional molecule made of one or more polypeptides.

Enzymes

• Enzyme: Protein that speeds up chemical reactions by lowering activation energy.

• Substrate: Reactant acted upon by an enzyme.

• Active Site: Region on enzyme where substrate binds.

• Inhibitor: Substance that decreases enzyme activity (competitive or noncompetitive).

Equation (Enzyme Reaction):

$\mathrm{E} + \mathrm{S} \rightleftharpoons \mathrm{ES} \rightarrow \mathrm{E} + \mathrm{P}$

Where E = enzyme, S = substrate, ES = enzyme-substrate complex, P = product.

Chapter 3: The Cell: The Fundamental Unit of Life

3.1 Prokaryotic and Eukaryotic Cells

Cells are the basic units of life. They can be classified as prokaryotic or eukaryotic.

• Prokaryotic Cells: Lack a nucleus; include Bacteria and Archaea.

• Eukaryotic Cells: Have a nucleus and membrane-bound organelles; include plants, animals, fungi, and protists.

• Key Structures: Plasma membrane, cytoplasm, ribosomes, cell wall (in many prokaryotes), nucleoid (prokaryotes), flagellum, capsule, plasmid, pilus.

3.2 Structures of Plant and Animal Cells

Plant and animal cells share many structures but also have unique features.

• Common Structures: Nucleus, plasma membrane, cytoplasm, ribosomes, mitochondria, endoplasmic reticulum, Golgi apparatus, vesicles, cytoskeleton.

• Plant Cell Unique Structures: Cell wall, chloroplasts, central vacuole.

• Animal Cell Unique Structures: Lysosomes, flagella (in some), centrioles.

3.3 Membrane Structure

Cell membranes are composed of a double layer of phospholipids with embedded proteins, forming a fluid mosaic.

• Phospholipid Bilayer: Hydrophilic heads face outward; hydrophobic tails face inward.

• Membrane Proteins: Facilitate transport, communication, and structural support.

• Carbohydrates: Attached to proteins/lipids for cell recognition.

• Extracellular Fluid: Surrounds the cell.

3.4 Membrane Transport

Membranes regulate the movement of substances into and out of cells.

• Passive Transport: Movement down a concentration gradient; no energy required (includes diffusion, osmosis, facilitated diffusion).

• Active Transport: Movement against a concentration gradient; requires energy (ATP).

• Endocytosis/Exocytosis: Bulk transport into/out of the cell.

3.5 The Nucleus and Chromosomes

The nucleus contains the cell's genetic material organized as chromosomes.

• Nucleus: Surrounded by nuclear envelope with pores; contains nucleolus and chromatin.

• Chromatin: DNA and proteins; condenses to form chromosomes during cell division.

• Nucleolus: Site of ribosome synthesis.

3.6 Protein Production

Several organelles work together to produce and transport proteins.

• Ribosomes: Sites of protein synthesis (translation).

• Endoplasmic Reticulum (ER): Rough ER has ribosomes; synthesizes proteins. Smooth ER synthesizes lipids.

• Golgi Apparatus: Modifies, sorts, and packages proteins.

• Vesicles: Transport materials within the cell.

• Lysosomes: Digestive organelles.

3.7 Energy Conversion: Chloroplasts and Mitochondria

Chloroplasts and mitochondria are organelles that convert energy for cellular use.

• Chloroplast: Site of photosynthesis in plants; contains thylakoids (stacked as grana), stroma.

• Mitochondrion: Site of cellular respiration; produces ATP.

Equation (Cellular Respiration):

$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2 \rightarrow 6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + \mathrm{ATP}$

Equation (Photosynthesis):

$6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + \text{light energy} \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2$

3.8 Cellular Structures for Storage, Movement, and Shape

• Cytoskeleton: Network of protein fibers for support and movement.

• Vacuole: Storage organelle; large central vacuole in plants.

• Cell Wall: Rigid structure outside the plasma membrane in plants, fungi, and some protists.

• Flagellum/Cilium: Structures for movement.

• Extracellular Matrix: Network outside animal cells for support and signaling.

Additional info: These notes expand on the provided outline by defining key terms, explaining concepts, and providing relevant examples and equations for foundational biology topics.