STAAR/BENCHMARK REVIEW BIOLOGY

Biomolecules (Macromolecules)

Biomolecules are large molecules essential for life. There are four main types:

1. Carbohydrates

• Examples: Sugar (glucose), starches, fiber

• Function:

  • Provides quick energy for cells.

  • Plants make carbohydrates through photosynthesis (using sunlight, water, and CO₂ to create glucose).

  • Used in cellular respiration (cells break down glucose to produce energy in the form of ATP).

• Structure: Made of carbon (C), hydrogen (H), and oxygen (O) in a 1:2:1 ratio.

2. Lipids (Fats and Oils)

• Examples: Butter, oils, waxes

• Function:

  • Long-term energy storage (more energy per gram than carbohydrates).

  • Insulation (helps regulate body temperature).

  • Forms cell membranes (phospholipids).

• Structure: Made of fatty acids and glycerol; does not dissolve in water (hydrophobic).

3. Proteins

• Examples: Meat, eggs, beans

• Function:

  • Builds physical traits like hair, muscles, and skin.

  • Enzymes are a special type of protein that speeds up chemical reactions.

  • Transport (hemoglobin carries oxygen in blood).

• Structure: Made of amino acids linked together in a chain.

4. Nucleic Acids

• Examples: DNA & RNA

• Function:

  • Stores genetic information and provides instructions for making proteins.

  • DNA is found in the nucleus of eukaryotic cells.

  • RNA is used in protein synthesis (helps make proteins).

• Structure: Made of nucleotides (sugar, phosphate, nitrogen base).

Viruses (Not Living)

• Viruses do not meet all characteristics of life because they cannot reproduce on their own.

• Must infect a host cell to make copies of themselves.

• Parts of a virus:

  • Capsid: A protein shell that protects viral genetic material.

  • DNA or RNA: Holds the instructions for making new viruses.

Enzymes (Biological Catalysts)

• Function:

  • Speed up chemical reactions in the body.

  • Work by breaking molecules apart (digestion) or putting them together (DNA replication).

• How enzymes work:

  • The substrate (reactant) must fit into the enzyme’s active site like a key in a lock.

• Factors that affect enzyme function:

  • Temperature & pH: If too high or too low, the enzyme denatures (loses its shape and stops working).

Cells

There are two main types of cells:

1. Prokaryotic Cells (Bacteria Only)

• Smaller & simpler than eukaryotic cells.

• No nucleus (DNA floats in cytoplasm).

2. Eukaryotic Cells (Plants & Animals)

• Larger & more complex than prokaryotic cells.

• Has a nucleus (stores DNA).

• Has many organelles (tiny structures with specific jobs).

Organelles & Their Functions

DNA (Genetic Material)

• Function: Holds instructions to build proteins.

• Other names: Genes, chromosomes, chromatin.

• Made of 4 nitrogen bases: A (Adenine), T (Thymine), C (Cytosine), G (Guanine).

  • The order of these bases makes each organism unique.

• Humans have 46 chromosomes (23 pairs) in normal cells, but 23 chromosomes in sex cells (sperm/egg).

DNA Replication (Making a Copy of DNA)

• Happens before a cell divides.

• Ensures each new cell gets an identical copy of DNA.

Protein Synthesis (Making Proteins)

• Purpose: Cells make proteins using DNA instructions.

• Steps:

  1. Transcription (in the nucleus): DNA → mRNA.

  2. Translation (in ribosomes): mRNA → Proteins (amino acids).

Cell Cycle & Mitosis (Cell Division)

• Purpose: Cells divide for growth, repair, and reproduction.

• Phases:

  • Interphase (cell grows & prepares to divide).

  • Mitosis (divides DNA into two identical cells).

    • Prophase → Metaphase → Anaphase → Telophase.

• Cancer: Uncontrolled cell division that forms tumors.

Cell Transport (How Molecules Move)

• Purpose: Helps cells maintain homeostasis.

• Types:

  1. Passive Transport: No energy needed.

     • Moves molecules from high to low concentration until balanced (equilibrium).

  2. Active Transport: Requires ATP energy.

     • Moves molecules from low to high concentration (against the gradient).

Mutations (Changes in DNA)

• Substitution: One base is replaced with another.

  • Silent Mutation: Does not change the protein.

• Frameshift Mutations (more severe):

  • Insertion: Extra base is added.

  • Deletion: Base is removed.

Meiosis (Formation of Sex Cells)

• Purpose: Creates sperm & egg cells.

• Outcome:

  • 4 genetically different cells.

  • Half the chromosomes (23 in humans).

  • Crossing over: Chromosomes swap DNA for genetic diversity.

Genetics (Inheritance of Traits)

• Each trait = 2 alleles (one from mom, one from dad).

• Alleles (versions of a gene):

  • Dominant (strong, uppercase): BB or Bb = trait shows.

  • Recessive (weak, lowercase): bb = trait only shows if both alleles are recessive.

• Genotype (letter combination): BB, Bb, bb.

• Phenotype (physical trait): Hair color, eye color.

• Homozygous (BB or bb); Heterozygous (Bb).

Cell Energy

Photosynthesis (in Plants, Chloroplasts)

• Purpose: Converts sunlight into glucose (food for plants).

• Equation: 6CO2+6H2O+sunlight→C6H12O6(glucose)+6O26CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ (glucose) + 6O₂

Cellular Respiration (in Mitochondria, All Organisms)

• Purpose: Converts glucose into ATP (usable energy).

• Equation:

  C6H12O6+6O2→6CO2+6H2O+ATP(energy)C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (energy)

• Connection: The products of photosynthesis are the reactants for cellular respiration!