General Biology Exam 1 Review: Foundations, Chemistry, Macromolecules, and Cell Structure

Study Guide - Smart Notes

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Chapter 1: Foundations of Biology

Major Themes of Life

Biology is the study of living organisms and their interactions with the environment. Understanding the major themes of life provides a framework for exploring biological concepts.

Organization: Life is organized in a hierarchical manner (biosphere → ecosystem → molecules).
Information: Genetic information is stored and transmitted in living organisms.
Energy and Matter: Life requires energy and matter to sustain processes.
Interactions: Organisms interact with each other and their environment.
Evolution: Populations evolve over time through natural selection.

Scientific Method

The scientific method is a systematic approach to understanding natural phenomena.

Observation: Gathering data about the natural world.
Hypothesis: Formulating a testable explanation.
Experiment: Testing hypotheses under controlled conditions.
Controlled Experiment: An experiment in which only one variable is changed at a time, while others are kept constant.

Chapter 2: Chemistry of Life

Atoms and Elements

Atoms are the basic units of matter, and elements are defined by the number of protons in their nuclei.

Atomic Number: Number of protons in an atom; defines the element.
Electron Configuration: Electrons fill shells around the nucleus; first shell holds 2, second holds 8, etc.
Valence Electrons: Electrons in the outermost shell; determine chemical reactivity.
Unpaired Electrons: Atoms with unpaired electrons in their valence shell are more reactive.

Chemical Bonds

Chemical bonds form when atoms interact to achieve stable electron configurations.

Covalent Bonds: Atoms share electrons to fill their valence shells.
Ionic Bonds: Atoms transfer electrons, resulting in charged ions that attract each other.
Hydrogen Bonds: Weak attractions between partially charged regions of molecules, important in water and biological macromolecules.

Properties of Water

Water is essential for life due to its unique chemical and physical properties.

Cohesion: Water molecules stick to each other via hydrogen bonds.
Adhesion: Water molecules stick to other surfaces.
High Specific Heat: Water resists temperature changes.
Evaporative Cooling: As water evaporates, it removes heat from surfaces.

Acids, Bases, and pH

The pH scale measures the concentration of hydrogen ions () in a solution.

Acid: Substance that increases in solution; pH < 7.
Base: Substance that decreases in solution; pH > 7.
Neutral: pH = 7.

Formula:

Macromolecules and Cell Structure

Macromolecules: Structure and Function

Biological macromolecules are large molecules essential for life, including carbohydrates, proteins, nucleic acids, and lipids.

Carbohydrates: Monomers are monosaccharides ("one sugar"); polymers are polysaccharides ("many sugars").
Proteins: Monomers are amino acids; polymers are polypeptides.
Nucleic Acids: Monomers are nucleotides; polymers are DNA/RNA polynucleotides.
Lipids: Not true polymers; include fats, phospholipids, and steroids.

Isomers and Molecular Shape

Isomers are molecules with the same chemical formula but different structures.

Structural Isomers: Differ in the arrangement of atoms.
Cis-trans Isomers: Differ in spatial arrangement around double bonds.
Enantiomers: Mirror-image isomers.
Molecular Shape: Influences biological activity and function.

Linkages and Polymer Formation

Monomers are joined to form polymers via dehydration reactions, which remove water to form covalent bonds.

Carbohydrates: Glycosidic linkages.
Proteins: Peptide bonds.
Nucleic Acids: Phosphodiester bonds.

Levels of Protein Structure

Proteins have four levels of structure:

Primary: Sequence of amino acids.
Secondary: Alpha helices and beta sheets formed by hydrogen bonding.
Tertiary: 3D folding due to side chain interactions.
Quaternary: Association of multiple polypeptide chains.

ATP: Cellular Energy

ATP (adenosine triphosphate) is the primary energy carrier in cells, storing energy in its phosphate bonds.

Cell Structure and Organelles

Phospholipid Bilayer and Membranes

Cell membranes are composed of a phospholipid bilayer, which forms a selective barrier around cells.

Phospholipids: Have hydrophilic heads and hydrophobic tails.
Bilayer: Hydrophobic tails face inward, hydrophilic heads face outward.

Organelles: Structure and Function

Organelles are specialized structures within cells that perform distinct functions.

Ribosomes: Sites of protein synthesis; can be bound (to rough ER) or free (in cytosol).
Vesicles: Membrane-bound sacs for transport and storage.
Lysosomes: Contain digestive enzymes to break down macromolecules and cellular debris.
Peroxisomes: Break down fatty acids and detoxify harmful substances.
Mitochondria: Powerhouse of the cell; site of ATP generation and cellular respiration.
Chloroplasts: Site of photosynthesis in plant cells.
Nucleus: Contains DNA; site of ribosome manufacturing (nucleolus).
Endoplasmic Reticulum (ER):
- Rough ER: Protein synthesis (with bound ribosomes).
- Smooth ER: Lipid synthesis, detoxification, carbohydrate metabolism, Ca2+ storage.
Golgi Apparatus: Protein modification, sorting, and shipping.
Cytoskeleton: Provides cell structure and enables movement.

Protein Transport and Secretion

Proteins synthesized in the cell may be exported or used internally. The pathway for secreted proteins is:

DNA → mRNA → protein synthesis in rough ER → transport vesicle → Golgi apparatus → transport vesicle → cell membrane (exocytosis)
Proteins destined for the cytosol are synthesized by free ribosomes.

Endosymbiotic Theory

The endosymbiotic theory explains the origin of mitochondria and chloroplasts, suggesting they were once independent prokaryotes engulfed by ancestral eukaryotic cells.

Both have their own DNA and can reproduce independently within the cell.

Table: Comparison of Major Macromolecules

Macromolecule	Monomer	Polymer	Main Function
Carbohydrate	Monosaccharide	Polysaccharide	Energy storage, structure
Protein	Amino acid	Polypeptide	Catalysis, structure, transport
Nucleic Acid	Nucleotide	DNA/RNA	Genetic information
Lipid	Fatty acid (not true monomer)	Triglyceride, phospholipid	Energy storage, membranes

Additional info: Some explanations and examples have been expanded for clarity and completeness.