Biology Crash Course Notes

Organic Compounds

  • All matter is composed of elements, which are composed of atoms.
  • Organic compounds are essential molecules containing carbon.
  • Four main categories:
    • Nucleic acids
    • Proteins
    • Carbohydrates
    • Lipids
  • Monomers (basic units):
    • Nucleic acids: Nucleotides
    • Proteins: Amino acids
    • Carbohydrates: Monosaccharides
    • Lipids: Fatty acids and glycerol
  • Mnemonic: "Clean Later Party Now" (Carbohydrates, Lipids, Proteins, Nucleic acids).
  • Enzymes (E) are a type of protein.

Water

  • Universal solvent.
  • Polar molecule (partially positive and partially negative).
  • Hydrophilic: Water-loving, soluble.
  • Hydrophobic: Water-fearing, insoluble.
  • Properties:
    • Cohesion: Attraction to itself.
    • Adhesion: Attraction to other molecules.
    • Capillary action: Cohesion and adhesion working together against gravity.
    • High surface tension: Allows small bugs and leaves to float.

Cells

  • Basic units of life.
  • All cells have:
    • Cell membrane (phospholipid bilayer)
    • Genetic information (DNA)
    • Cytoplasm

Cell Membrane

  • Phospholipid bilayer:
    • Heads are hydrophilic.
    • Tails are hydrophobic.

Types of Cells

  • Eukaryotic:
    • Have a nucleus and membrane-bound organelles (e.g., mitochondria).
  • Prokaryotic:
    • No nucleus or membrane-bound organelles (except ribosomes).
    • DNA floats freely in cytoplasm.
  • Examples:
    • Eukaryotic: Animals, plants
    • Prokaryotic: Bacteria, archaea

Animal vs. Plant Cells

  • Animal cells: Cell membrane.
  • Plant cells: Cell wall, chloroplasts (for photosynthesis), large vacuole.
  • Both are eukaryotic.

Cell Membrane Transport

  • Simple diffusion: Movement from high to low concentration (no energy required).
  • Facilitated diffusion: Movement from high to low concentration with help of a protein channel (no energy required).
  • Active transport: Movement from low to high concentration, requires energy (ATP).
  • Osmosis is water moving from a higher concentration of water particles to a lower concentration of water.
  • Isotonic Solution: An equal balance of particles in and out of the cell that are not water.
  • Hypotonic Solution: Fewer solute particles outside the cell, more water outside the cell, a lower concentration of water inside the cell, so water would move in.
  • Hypertonic Environment: More solute particles outside the cell or a higher concentration of solute particles. Water will move outside the cell.

Enzymes

  • Proteins that act as biological catalysts.
  • Examples: Ligase, helicase, polymerase, amylase (often end in -ase).
  • Temperature and pH can affect enzyme function.
  • High temperatures can denature (unfold) enzymes.
  • Active site: Where enzyme interacts with substrate.

Cellular Respiration

  • Occurs in mitochondria.
  • Converts glucose and oxygen into ATP (energy).
  • Produces carbon dioxide and water as byproducts.
  • C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O + ATP
  • Eukaryotic organisms perform respiration.

Photosynthesis

  • Plants use sunlight energy to convert carbon dioxide and water into glucose and oxygen.
  • 6CO2 + 6H2O + \text{Sunlight Energy} \rightarrow C6H{12}O6 + 6O2
  • Complementary to cellular respiration.

Fermentation

  • Anaerobic respiration (without oxygen).
  • Less efficient than cellular respiration (2 ATP vs. 36 ATP).
  • Examples:
    • Lactic acid fermentation (in muscle cells): Produces lactic acid as byproduct.
    • Alcoholic fermentation (by yeast): Produces ethanol (alcohol) and carbon dioxide.

DNA

  • All living things contain DNA.
  • DNA is organized into chromosomes.
  • Chromosomes condense before cell division.
  • Each chromosome is a duplicated set of DNA with two sister chromatids connected by a centromere.
  • Chromatin: Unwound, uncondensed DNA.

Mitosis

  • Asexual reproduction that makes exact copies of cells.
  • One cell generates two identical daughter cells.
  • Phases: Prophase, Metaphase, Anaphase, Telophase (PMAT).
  • Cytokinesis: Cytoplasm divides.
  • Prophase: Nuclear envelope dissolves, chromosomes condense.
  • Metaphase: Chromosomes align in the middle, spindle fibers attach.
  • Anaphase: Sister chromatids separate and move away.
  • Telophase: New nuclear envelopes form, cell starts to separate.

Meiosis

  • Generates sex cells (gametes).
  • One parent cell produces four daughter cells with half the genetic information.
  • Goes through PMAT twice.
  • Genetic information is mixed, creating diversity.

Genetics

  • Gregor Mendel: Father of genetics.
  • Traits are controlled by two alleles (versions of a gene).
  • Alleles can be dominant or recessive.
  • Definitions:
    • Heterozygous: Two different alleles (e.g., Bb).
    • Homozygous: Two identical alleles (e.g., BB or bb).
    • Genotype: Combination of genes.
    • Phenotype: Physical characteristics resulting from genotype.
  • Punnett squares predict probability of offspring genotypes and phenotypes.
  • Most human traits are more complicated than simple Mendelian genetics.
  • Incomplete dominance: Blending of traits.
  • Codominance: Both traits are represented.
  • Sex-linked traits: Carried on X and Y chromosomes.
  • Environmental influences: Genes can be influenced by the environment. Example: Hydrangea colors differ based on soil pH.
  • Nondisjunction: Failure of chromosomes to separate properly during meiosis/mitosis leads to cells with different numbers of chromosomes.
  • Trisomy 21: Three copies of the 21st chromosome (Down syndrome).

DNA Structure and Replication

  • Four bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C).
  • A pairs with T, G pairs with C.
  • DNA replicates during the S phase of the cell cycle.
  • Semi-conservative replication: Each new DNA strand has half the old strand and half brand new.
  • Nucleotide: Phosphate, sugar, and a base (A, T, G, or C).
  • Backbone: Phosphate and sugar molecules.

Protein Synthesis

  • DNA \rightarrow mRNA \rightarrow Protein
  • Transcription: mRNA is built off of the DNA template in the nucleus.
  • Translation: mRNA goes to a ribosome, tRNA molecules match up with mRNA codons and bring amino acids to link up and form a polypeptide chain which is a protein.

DNA vs. RNA

FeatureDNARNA
StructureDouble-strandedSingle-stranded
SugarDeoxyriboseRibose
BasesA, T, G, CA, U, G, C

Transcription and Translation Practice

  • Given a DNA sequence, transcribe it into mRNA.
  • Remember to replace T with U in mRNA.
  • Use a codon chart to translate mRNA into amino acids.

Biotechnology

  • Emerging technologies: Lab-grown meat, DNA tests, genetically engineered organisms, CRISPR.
  • Ethical questions arise with new techniques.
  • Gel electrophoresis: Identifies different parts of DNA to study evolutionary relationships, identify DNA at crime scenes, and for paternity testing.

Evolution

  • Change in genetic makeup of a population over time.
  • Natural selection: Major mechanism behind evolution.
  • Evolutionary fitness: Ability to survive and reproduce.
  • Environments act as selective pressures.
  • Adaptation: Inherited trait that is favorable for survival.
  • Charles Darwin: Developed the theory of natural selection.
  • Evidence: Fossil record, biochemical and DNA evidence, embryology.
  • Phylogenetic Tree/Cladogram: Shows evolutionary relationships over time.

Ecology

  • Levels of organization: Molecule to biosphere.
  • Biodiversity: Variety of organisms in an ecosystem.
  • Biodiversity increases resilience of an ecosystem.
  • Ecosystems change due to nutrient addition, fires, droughts, floods, earthquakes.
  • Food chain: Shows flow of energy.
  • Arrows point towards the organism that is doing the eating.
  • Trophic levels:
    • Producers (autotrophs): Make their own food.
    • Consumers (heterotrophs): Consume other organisms.
    • Primary, secondary, tertiary consumers.
  • Trophic pyramid: Most energy at the bottom, energy lost as you go up.
  • Carbon cycle: Photosynthesis, respiration, decomposition, combustion.
  • Renewable resources: Can be replaced quickly.
  • Nonrenewable resources: Cannot be replaced quickly.
  • Ozone layer hole: Caused by CFCs, led to harmful UV radiation.
  • Global warming: Caused by burning fossil fuels, can lead to rising sea levels.
  • Human impacts: Invasive species, diseases, habitat change, deforestation, industrialization.
  • Positive impacts: Reducing consumption, recycling, planting native species, protecting wildlife, sustainable practices.