General Biology: Week 3 Study Guide (Chapters 2, 3, 5, 6, 7, 8, 9)

Chapter 2: The Chemical Context of Life

Concept Checkpoint 2.1: Elements and Compounds

The study of biology begins with understanding the chemical elements that compose living matter. Elements combine to form compounds, which are essential for life.

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

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

• Major elements in organisms: Carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur.

• Trace elements: Elements required by organisms in minute quantities.

Example: Oxygen, carbon, hydrogen, and nitrogen account for most of the mass of living organisms.

Concept Checkpoint 2.2: Atomic Structure

The properties of elements depend on the structure of their atoms.

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

• Atomic number: Number of protons in the nucleus.

• Valence electrons: Electrons in the outermost shell, determining chemical reactivity.

• Noble gases: Elements with filled valence shells, generally unreactive.

Example: Atoms are most stable when their valence shell is full.

Concept Checkpoint 2.3: Chemical Bonds

Molecules and ionic compounds are formed by chemical bonding between atoms.

• Covalent bond: Sharing of electron pairs between atoms.

• Ionic bond: Transfer of electrons from one atom to another, resulting in oppositely charged ions.

• Polar covalent bond: Unequal sharing of electrons, leading to partial charges.

Example: Water molecules are held together by polar covalent bonds.

Concept Checkpoint 2.4: Chemical Reactions

Chemical reactions make and break chemical bonds, transforming substances.

• Reactants: Starting materials in a chemical reaction.

• Products: Resulting substances after a chemical reaction.

• Chemical equilibrium: State in which the forward and reverse reactions occur at the same rate.

Example: In biological systems, reactions rarely reach equilibrium, allowing for continuous metabolic processes.

Chapter 3: Water and Life

Concept Checkpoint 3.1: Hydrogen Bonding in Water

Water molecules form hydrogen bonds, which are crucial for many of water's unique properties.

• Hydrogen bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen).

• Cohesion: Water molecules stick together due to hydrogen bonding.

• Adhesion: Water molecules stick to other substances.

• High specific heat: Water resists changes in temperature.

Example: Water's high specific heat helps regulate Earth's climate.

Concept Checkpoint 3.2: Water's Role in Life

Water's properties contribute to Earth's suitability for life.

• Surface tension: Measure of how difficult it is to break the surface of a liquid.

• Solvent properties: Water dissolves many substances, facilitating chemical reactions.

• Acid-base chemistry: Water can dissociate into H+ and OH- ions.

Example: Rainwater becomes slightly acidic when carbon dioxide dissolves in it, forming carbonic acid.

Chapter 5: The Structure and Function of Large Biological Molecules

Concept Checkpoint 5.1: Macromolecules

Macromolecules are large molecules built from monomers.

• Dehydration reaction: Builds polymers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Example: Proteins, carbohydrates, and nucleic acids are macromolecules.

Concept Checkpoint 5.2: Carbohydrates

Carbohydrates serve as fuel and building material.

• Monosaccharides: Simple sugars (e.g., glucose).

• Disaccharides: Two monosaccharides joined by a glycosidic bond.

• Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose).

Example: Glucose is an aldose sugar; the difference between aldose and ketose sugars is the position of the carbonyl group.

Concept Checkpoint 5.3: Lipids

Lipids are a diverse group of hydrophobic molecules.

• Fats: Composed of glycerol and fatty acids.

• Phospholipids: Major component of cell membranes.

• Steroids: Lipids with a carbon skeleton consisting of four fused rings.

Example: Lipids are not true polymers and are insoluble in water.

Concept Checkpoint 5.4: Proteins

Proteins include a diversity of structures, resulting in a wide range of functions.

• Amino acids: Building blocks of proteins.

• Primary structure: Sequence of amino acids.

• Secondary structure: Alpha helices and beta sheets.

• Tertiary structure: Overall 3D shape of a polypeptide.

• Quaternary structure: Association of multiple polypeptides.

Example: Denaturation disrupts protein structure and function.

Concept Checkpoint 5.5: Nucleic Acids

Nucleic acids store, transmit, and help express hereditary information.

• DNA: Deoxyribonucleic acid, stores genetic information.

• RNA: Ribonucleic acid, involved in protein synthesis.

• Nucleotide: Monomer of nucleic acids, composed of a sugar, phosphate, and nitrogenous base.

Example: Complementary base pairing enables DNA replication.

Concept Checkpoint 5.6: Genomics and Proteomics

Genomics and proteomics have transformed biological inquiry and applications.

• Genomics: Study of whole sets of genes and their interactions.

• Proteomics: Study of sets of proteins and their properties.

Example: DNA sequence comparisons can reveal evolutionary relationships.

Chapter 6: A Tour of the Cell

Concept Checkpoint 6.1: Microscopy and Cell Structure

Biologists use microscopes and biochemistry to study cells.

• Light microscope: Used to view cells and large organelles.

• Electron microscope: Used to view subcellular structures.

• Cell fractionation: Technique to separate cell components.

Example: Ribosomes are visible only with electron microscopy.

Concept Checkpoint 6.2: Eukaryotic Cell Structure

Eukaryotic cells have internal membranes that compartmentalize their functions.

• Nucleus: Contains genetic material.

• Endoplasmic reticulum: Synthesizes proteins and lipids.

• Golgi apparatus: Modifies, sorts, and ships proteins.

• Lysosomes: Digestive organelles.

Example: Plant cells have large central vacuoles.

Concept Checkpoint 6.3: Genetic Instructions

The nucleus contains most of the cell's genetic instructions.

• Chromatin: DNA and proteins in the nucleus.

• Nucleolus: Site of ribosome synthesis.

Example: Ribosomes synthesize proteins in the cytoplasm and on the rough ER.

Concept Checkpoint 6.4: Endomembrane System

The endomembrane system regulates protein traffic and performs metabolic functions.

• Vacuoles: Storage and transport in plant cells.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

Example: Disruption of mitochondria decreases ATP synthesis.

Concept Checkpoint 6.5: Energy Conversion

Mitochondria and chloroplasts change energy from one form to another.

• Mitochondria: Site of cellular respiration.

• Chloroplasts: Site of photosynthesis in plants.

Example: Thylakoids are found in chloroplasts.

Concept Checkpoint 6.6: Cytoskeleton

The cytoskeleton is a network of fibers that organizes structures and activities in the cell.

• Microtubules: Shape the cell and guide organelle movement.

• Microfilaments: Involved in cell movement and shape.

• Intermediate filaments: Provide structural support.

Example: Motor proteins interact with the cytoskeleton for cellular movement.

Concept Checkpoint 6.7: Cell Connections

Extracellular components and connections between cells help coordinate cellular activities.

• Cell wall: Found in plants, provides structural support.

• Plasmodesmata: Channels between plant cells.

• Tight junctions, desmosomes, gap junctions: Connections in animal cells.

Example: Gap junctions allow communication between animal cells.

Chapter 7: Membrane Structure and Function

Concept Checkpoint 7.1: Membrane Structure

Cellular membranes are fluid mosaics of lipids and proteins.

• Phospholipid bilayer: Forms the basic structure of membranes.

• Integral proteins: Embedded in the membrane.

• Peripheral proteins: Attached to the membrane surface.

Example: Membranes are selectively permeable, allowing some substances to cross more easily than others.

Concept Checkpoint 7.2: Selective Permeability

Membrane structure results in selective permeability.

• Small hydrophobic molecules: Pass easily through the membrane.

• Large or charged molecules: Require transport proteins.

Example: Oxygen and carbon dioxide diffuse rapidly across membranes.

Concept Checkpoint 7.3: Passive Transport

Passive transport is diffusion of a substance across a membrane with no energy investment.

• Diffusion: Movement of molecules from high to low concentration.

• Facilitated diffusion: Transport proteins help molecules cross the membrane.

Example: Water moves through aquaporins by facilitated diffusion.

Concept Checkpoint 7.4: Active Transport

Active transport uses energy to move solutes against their gradients.

• ATP: Provides energy for active transport.

• Ion pumps: Maintain membrane potential.

Example: Sodium-potassium pump moves Na+ out and K+ into cells.

Concept Checkpoint 7.5: Bulk Transport

Bulk transport across the plasma membrane occurs by exocytosis and endocytosis.

• Phagocytosis: Cell engulfs large particles.

• Pinocytosis: Cell takes in fluid.

• Receptor-mediated endocytosis: Specific molecules are taken in after binding to receptors.

Example: White blood cells use phagocytosis to engulf bacteria.

Chapter 8: An Introduction to Metabolism

Concept Checkpoint 8.1: Metabolism

An organism's metabolism transforms matter and energy.

• Metabolic pathway: Series of chemical reactions that build or break down molecules.

• Anabolic pathways: Build complex molecules from simpler ones.

• Catabolic pathways: Break down complex molecules to release energy.

Example: Cellular respiration is a catabolic pathway.

Concept Checkpoint 8.2: Free Energy and Spontaneity

The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously.

• Exergonic reaction: Releases energy; spontaneous.

• Endergonic reaction: Requires energy input; non-spontaneous.

• Gibbs free energy equation:

$9G = 9H - T9S$

Example: ATP hydrolysis is an exergonic reaction.

Concept Checkpoint 8.3: ATP and Energy Coupling

ATP powers cellular work by coupling exergonic reactions to endergonic reactions.

• ATP (adenosine triphosphate): Main energy currency of the cell.

• Phosphorylation: Transfer of a phosphate group to another molecule.

Example: ATP drives muscle contraction and active transport.

Concept Checkpoint 8.4: Enzymes

Enzymes speed up metabolic reactions by lowering energy barriers.

• Catalyst: Substance that increases the rate of a reaction without being consumed.

• Active site: Region of the enzyme where substrate binds.

• Competitive inhibition: Inhibitor binds to the active site.

• Noncompetitive inhibition: Inhibitor binds elsewhere, changing enzyme shape.

Example: Enzymes are specific to their substrates.

Chapter 9: Cellular Respiration and Fermentation

Concept Checkpoint 9.1: Catabolic Pathways

Catabolic pathways yield energy by oxidizing organic fuels.

• Substrate-level phosphorylation: Direct transfer of phosphate to ADP to form ATP.

• Oxidative phosphorylation: ATP formation via electron transport chain.

Example: Glycolysis produces ATP by substrate-level phosphorylation.

Concept Checkpoint 9.2: Glycolysis

Glycolysis harvests chemical energy by oxidizing glucose to pyruvate.

• Net products per glucose: 2 pyruvate, 2 ATP, 2 NADH.

• Pyruvate oxidation: Produces acetyl-CoA for the citric acid cycle.

Example: Most CO2 released during cellular respiration comes from the citric acid cycle.

Concept Checkpoint 9.3: Citric Acid Cycle

After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules.

• Products: NADH, FADH2, ATP, CO2.

Example: NADH and FADH2 carry electrons to the electron transport chain.

Concept Checkpoint 9.4: Oxidative Phosphorylation

During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis.

• Electron transport chain: Series of protein complexes that transfer electrons.

• Chemiosmosis: Use of a proton gradient to drive ATP synthesis.

Example: ATP synthase produces ATP as protons flow back into the mitochondrial matrix.

Concept Checkpoint 9.5: Fermentation

Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen.

• Lactic acid fermentation: Pyruvate is reduced to lactate.

• Alcohol fermentation: Pyruvate is converted to ethanol and CO2.

Example: Muscle cells use lactic acid fermentation when oxygen is scarce.

Concept Checkpoint 9.6: Metabolic Pathways Integration

Glycolysis and the citric acid cycle connect to many other metabolic pathways.

• Metabolic intermediates: Can be used for biosynthesis of amino acids, nucleotides, and lipids.

Example: Plant mitochondria oxidize pyruvate in the light and dark, but photosynthesis only occurs in the light.

Chapter	Key Concept	Example/Application
2	Elements and chemical bonds	Water's polarity and hydrogen bonding
3	Properties of water	High specific heat regulates climate
5	Macromolecules	Proteins, carbohydrates, lipids, nucleic acids
6	Cell structure	Eukaryotic vs. prokaryotic cells
7	Membrane structure	Phospholipid bilayer, selective permeability
8	Metabolism	ATP, enzymes, metabolic pathways
9	Cellular respiration	Glycolysis, citric acid cycle, fermentation

Additional info: These study notes expand upon the provided practice questions and concept checkpoints, offering definitions, examples, and academic context for key topics in General Biology. Equations and tables are included for clarity and completeness.