General Biology: Foundations, Chemistry, and Cell Structure Study Guide

Study Guide - Smart Notes

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Cell Structure and Function

Prokaryotic vs. Eukaryotic Cells

Cells are the basic units of life, and they are classified as either prokaryotic or eukaryotic based on their structural features.

Prokaryotic Cells: Lack a nucleus and membrane-bound organelles. DNA is located in a region called the nucleoid. Examples: Bacteria and Archaea.
Eukaryotic Cells: Have a true nucleus enclosed by a membrane and possess various membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum). Examples: Plants, Animals, Fungi, Protists.
Key Differences: Eukaryotes are generally larger and more complex than prokaryotes.

Characteristics of Living Organisms

What Makes an Organism Living?

Living organisms share several fundamental characteristics:

Organization (cellular structure)
Metabolism (energy use and chemical reactions)
Homeostasis (regulation of internal environment)
Growth and development
Reproduction
Response to stimuli
Evolutionary adaptation

Biological Organization and Classification

Complexity of Biological Systems & Ecological Organization

Biological systems are organized into hierarchical levels:

Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

Feedback Regulation in Nature

Positive vs. Negative Feedback

Feedback mechanisms regulate biological systems:

Negative Feedback: Reduces the output or activity to maintain homeostasis (e.g., body temperature regulation).
Positive Feedback: Enhances or amplifies changes (e.g., blood clotting, childbirth contractions).

Evidence for Evolution

Common Ancestry and Natural Selection

Evidence for common ancestry includes similarities in DNA, fossil records, and anatomical structures. Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring.

Darwin vs. Lamarck: Darwin proposed natural selection; Lamarck suggested inheritance of acquired traits.

The Scientific Method

Steps and Descriptions

The scientific method is a systematic approach to inquiry:

Observation: Gathering information about phenomena.
Question: Formulating a question based on observations.
Hypothesis: Proposing a testable explanation.
Experiment: Testing the hypothesis with controlled experiments.
Data Collection: Gathering and recording results.
Analysis: Interpreting data to draw conclusions.
Conclusion: Accepting, rejecting, or modifying the hypothesis.

Variables in Experiments

Independent Variable: The factor that is changed or manipulated.
Dependent Variable: The factor that is measured or observed.
Control: The standard for comparison in an experiment.
Data: Collected observations and measurements.

Redi's 1668 Experiment (Spontaneous Generation)

Francesco Redi tested the idea that life could arise spontaneously. He showed that maggots only appeared in meat when flies could lay eggs on it, disproving spontaneous generation for larger organisms.

Basic Chemistry for Biology

Essential Elements of Life

Four Essential Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)

Atoms and Subatomic Particles

Atom: Smallest unit of matter retaining properties of an element.
Subatomic Particles: Protons (positive), Neutrons (neutral), Electrons (negative)
Atomic Number: Number of protons in an atom.
Atomic Mass: Sum of protons and neutrons.
Atoms are stable when: Their outer electron shell is full.

Chemical Bonds

Polar Covalent: Electrons shared unequally.
Non-polar Covalent: Electrons shared equally.
Ionic: Electrons transferred from one atom to another.
Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom.

Molecular Representations

Molecular Formula: Shows types and numbers of atoms (e.g., H2O).
Structural Formula: Shows arrangement of atoms.
Ball and Stick Model: 3D representation of atoms and bonds.
Space Filling Model: Shows relative sizes and spatial relationships.

Chemical Reactions

Substrate: Reactant in a chemical reaction.
Reactant: Starting material in a reaction.
Product: Substance formed from a reaction.
Balancing Equations: Number of atoms of each element must be equal on both sides of the equation.

Example Equation:

pH and Water Properties

pH: Measure of hydrogen ion concentration;
Acids: Donate H+ ions.
Bases: Accept H+ ions.
Buffer: Substance that minimizes changes in pH.
Properties of Water: Cohesion, adhesion, high specific heat, high heat of vaporization, less dense as a solid (ice floats), excellent solvent.
Why Ice Floats: Hydrogen bonds stabilize and keep molecules further apart in solid form, making ice less dense than liquid water.

Hydrophobic vs. Hydrophilic

Hydrophobic: Repels water (nonpolar molecules).
Hydrophilic: Attracts water (polar molecules).

Solutions

Solvent: Substance that dissolves another (e.g., water).
Solution: Homogeneous mixture of solute and solvent.

Greenhouse Gases and Effects

Greenhouse Gases: CO2, CH4, N2O, water vapor.
Greenhouse Effect: Trapping of heat in Earth's atmosphere by greenhouse gases, leading to global warming.

Organic vs. Inorganic Compounds

Organic: Contains carbon-hydrogen bonds (e.g., glucose).
Inorganic: Does not contain C-H bonds (e.g., NaCl, H2O).

Characteristics of Carbon

Can form four covalent bonds.
Forms the backbone of organic molecules.
Can form chains, rings, and complex structures.

Isomers and Enantiomers

Isomer: Compounds with the same molecular formula but different structures.
Structural Isomer: Differ in covalent arrangement.
Enantiomer: Mirror-image isomers.

Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties.

Amino (-NH2): Acts as a base.
Methyl (-CH3): Nonpolar, affects gene expression.
Carboxyl (-COOH): Acts as an acid.
Hydroxyl (-OH): Polar, forms hydrogen bonds.
Sulfhydryl (-SH): Forms disulfide bonds in proteins.

Organic Chemistry

Organic Chemistry: Study of carbon-containing compounds.

Dehydration and Hydrolysis Reactions

Dehydration Reaction: Joins monomers by removing water.
Hydrolysis: Breaks polymers by adding water.

Hydrogenated Vegetable Oil

Produced by adding hydrogen to unsaturated fats, making them more solid.
Used to increase shelf life and stability of foods.

Genetics and Macromolecules

Central Dogma of Genetics

Describes the flow of genetic information: DNA → RNA → Protein

Dietary Fiber and Lactose Intolerance

Insoluble Fiber: Important for digestive health; adds bulk to stool.
Lactose Intolerance: Caused by lack of lactase enzyme, leading to inability to digest lactose in dairy.

Biological Macromolecules

There are four major classes of biological macromolecules, each with specific monomers:

Macromolecule	Monomer (Subunit)	Example
Carbohydrates	Monosaccharides	Glucose
Proteins	Amino acids	Enzymes
Nucleic Acids	Nucleotides	DNA, RNA
Lipids	Glycerol and fatty acids	Triglycerides

Example: Carbohydrates are composed of monosaccharides such as glucose.

Additional info: Some explanations and examples were expanded for clarity and completeness based on standard General Biology curricula.