Biology Chapter: Scientific Inquiry and Molecules

Scientific Inquiry

• Components of a well-designed experiment are crucial for understanding.
• Control groups provide baselines for comparison.
• Experimental groups are exposed to the tested variable.
• Independent variables are manipulated factors, and dependent variables are measured.
• Constant variables are factors kept consistent for both groups.
• Interpreting graphs and charts is vital for data analysis.
• Scientific methodology, including experimental design and data analysis, is important.
• The EOC exam assesses understanding of core concepts, processes, and theories.

Life Molecules (Macromolecules/Polymers)

• Carbohydrates: Monosaccharides (single sugars like glucose) are short-term energy sources.
• Proteins: Amino acids form structural components, transport molecules, enzymes, and energy sources.
• Lipids (Fats): Fatty acids and glycerol provide insulation, hormones, long-term energy storage, and cell membranes.
• Nucleic Acids: Nucleotides comprise DNA, RNA, and ATP (energy currency).

Cell Structure and Function

Prokaryotes vs. Eukaryotes

• Prokaryotes: Single-celled, lack membrane-bound organelles and a nucleus (bacteria).
• Eukaryotes: Single or multi-celled, contain a nucleus and membrane-bound organelles (plants, animals).

Plant vs. Animal Cells (both eukaryotic)

• Shared features: Nucleus, nucleolus, cell membrane, cytoplasm, nuclear envelope, lysosomes, ER, Golgi, mitochondria, ribosomes, microtubules, and cytoskeleton.
• Animal cells uniquely contain centrioles.
• Plant cells possess cell walls, chloroplasts, and a central vacuole.

Movement of Molecules Across Cell Membranes

Passive Transport (no energy required)

• Diffusion: High concentration to low concentration until equilibrium (oxygen, carbon dioxide).
• Facilitated diffusion: Diffusion with transport protein assistance (glucose, large molecules).
• Osmosis: Water's movement across a membrane. (water).

Osmotic Responses

• Hypertonic: Higher solute concentration than cell; water leaves (cell shrinkage).
• Hypotonic: Lower solute concentration than cell; water enters (cell rupture in animal cells, no rupture in plants due to cell wall).
• Isotonic: Equal solute concentration; water movement is balanced.

Active Transport (energy required)

• Endocytosis: Molecules enter the cell via vesicles (food, liquids, bacteria).
• Exocytosis: Molecules exit the cell via vesicles (cell products, waste).
• Sodium-Potassium Pump: Protein moving sodium and potassium against concentration gradients.
• Contractile Vacuole: Pumps water out in single-celled organisms.

Cell Theory

• All organisms are composed of one or more cells.
• Cells are the basic units of structure and function.
• Cells arise from pre-existing cells.

Energy and Cells

• ATP: The primary energy carrier in cells (adenine, ribose, 3 phosphate groups).
• ATP stores energy in the second and third phosphate bonds, releasing energy when broken. It can be remade and recycled repeatedly.

Photosynthesis

• Endothermic process (requires light) where autotrophs manufacture glucose.
• Takes place in chloroplasts. 6CO2 + 6H2O → C6H12O6+ 6O2
• Two stages: Light-dependent reactions (thylakoid membrane), light-independent reactions (Calvin Cycle, stroma)

Cellular Respiration

• Exothermic process (releases energy) where all organisms break down food molecules for energy.
• Takes place in the mitochondria. C6H12O6+ 6O2 →6CO2 + 6H2O + ATP
• Stages: Glycolysis (cytoplasm), Krebs Cycle (mitochondrial matrix), Electron Transport Chain (inner mitochondrial membrane).
• Aerobic pathways require oxygen, while anaerobic pathways do not.
• Fermentation is an anaerobic process enabling glycolysis continuation when oxygen is scarce.

Cell Cycle

• Interphase (G1, S, G2), Mitosis (prophase, metaphase, anaphase, telophase, cytokinesis)

Cell Reproduction

• Binary Fission: Asexual reproduction in prokaryotes.
• Mitosis: Asexual reproduction in eukaryotic body cells (growth, repair).
• Meiosis: Sexual reproduction in eukaryotic germ cells producing gametes (sperm and egg).

Cell Cycle Regulation

• External factors (hormones, cell-to-cell contact) and internal factors (cyclins, kinases).
• Cancer involves uncontrolled cell division due to damaged genes.

Multicellular Organization

• Cells, tissues, organs, organ systems, organisms.

Stem Cells

• Undifferentiated cells capable of differentiating into many cell types.
• Embryonic: Found in early development, can become any cell type.
• Adult: Partially differentiated, can become several cell types.

Genetics

Mendel's Laws

• Segregation: Organisms inherit two copies of each gene and donate one copy per gamete.
• Independent Assortment: Allele pairs separate independently in gametes (except for linked genes).

Genotypes, Phenotypes, and Punnett Squares

• Genotypes (e.g., TT, Tt, tt): Genetic makeup.
• Phenotypes (e.g., hair color): Physical characteristics.
• Punnett squares: Predicts offspring genotypes and phenotypes. Use Punnett squares for monohybrid and dihybrid crosses.

Types of Inheritance

• Dominant/Recessive: One allele masks another (e.g., freckles).
• Codominance: Both alleles are expressed (e.g., red and white fur in cows in heterozygous state).
• Incomplete dominance: Heterozygotes display an intermediate phenotype (e.g., pink flowers).
• Multiple alleles: (e.g., human blood types).
• Sex-linked: Traits carried on sex chromosomes (X chromosome).

Chromosome Theory of Inheritance

• Genes reside on chromosomes; chromosome behavior in meiosis explains inheritance patterns.

Pedigrees

• Charts tracking traits through generations.

Nucleic Acids

• DNA: Double-stranded, double helix (adenine-thymine, guanine-cytosine).
• Replication: Copying DNA.
• RNA: Single-stranded (adenine-uracil, guanine-cytosine).
• Types: mRNA (message carriers), tRNA (amino acid carriers), rRNA (part of ribosomes).
• Transcription: Copying a gene to mRNA.
• Translation: mRNA's message into a protein sequence.
• Amino Acid Chart: Translates codons to amino acids.
• Mutations: DNA sequence alterations; somatic and germ cell mutations. Gene mutations (substitution or frameshift) and chromosomal mutations can affect proteins.

Evolution

• Natural Selection: Fittest organisms survive and reproduce, leading to genetic changes within populations over time.
• Microevolution: Species changes within populations.
• Macroevolution: Species changes over vast spans of time—new species formation
• Evidence for Evolution: Paleontology (fossils), Biochemistry (DNA/protein similarities), Embryology (embryo similarities), Comparative Anatomy (homologous structures).
• Hardy-Weinberg Equilibrium: Allele frequencies stay constant unless disrupted by forces (mutations, migration, non-random mating, natural selection, small populations).

Ecology

• Levels of Organization: Organisms, populations, communities, ecosystems, biosphere.
• Energy Flow: Sun → Autotrophs → Heterotrophs
• Trophic Levels: Producers, herbivores, carnivores.
• Ecological Pyramids: Models illustrating energy/numbers/biomass distribution; only 10% of the energy available to one trophic level is available to the next.
• Food Chains/Webs: Feeding interactions within an ecosystem.
• Biogeochemical Cycles: (Carbon, Water, Nitrogen).
• Succession: Sequential ecosystem development (primary and secondary).
• Community Interactions: Predation, parasitism, mutualism, commensalism, competition.
• Population Dynamics: Population size, density, limiting factors (density-dependent/independent), predator-prey relationships;
• Environmental Science: Natural processes (biogeochemical cycles and greenhouse effect), impact of human activities (renewable vs. non-renewable resources).
• Biodiversity and its factors. Ecosystems. Different types of organisms and their characteristics (bacteria to mammals).