Honors Bio Review

  1. Scientific Method Steps:

    • Observation: Noticing something in the natural world.

    • Hypothesis: A testable explanation or prediction about a phenomenon.

    • Experiment: A procedure to test the hypothesis.

    • Data Collection: Gathering measurable information during the experiment.

    • Analysis: Interpreting the data and comparing results to the hypothesis.

    • Conclusion: Determining if the hypothesis was supported or refuted.

    • Repeat: Repeating experiments to ensure consistency.

  2. Definitions:

    • Hypothesis: A proposed explanation for a phenomenon based on prior knowledge, testable and falsifiable.

    • Theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence.

    • Observation: The process of noting and recording something in the natural world.

    • Control Group: The group in an experiment that does not receive the experimental treatment.

    • Experimental Group: The group that is exposed to the experimental treatment.

    • Constants: Factors in an experiment that are kept the same across all groups.

    • Qualitative Data: Descriptive data (e.g., color, texture, appearance).

    • Quantitative Data: Numerical data (e.g., length, mass, temperature).

Graphing

  • Parts of a Graph:

    • Title: Describes the content of the graph.

    • X-axis: Horizontal axis (typically independent variable).

    • Y-axis: Vertical axis (typically dependent variable).

    • Legend: Explains the meaning of different symbols or lines.

    • Scale: Ensures that data points are evenly spaced.

    • Data Points: Represent individual measurements.

    • Trend Line: Line that shows the general direction or relationship in the data.

Microscopes

  1. Types of Microscopes:

    • Light Microscope: Uses visible light to magnify objects. Can view living cells, up to 1000x magnification.

    • Electron Microscope: Uses electron beams for high magnification (up to 500,000x). Includes scanning electron microscope (SEM) and transmission electron microscope (TEM).

  2. Parts of a Light Microscope:

    • Eyepiece (ocular lens): Where you look into the microscope.

    • Objective lenses: Different lenses with various magnifications.

    • Coarse Focus: Used for general focusing.

    • Fine Focus: Used for fine-tuning the focus.

    • Stage: Hold the slide.

    • Diaphragm: Controls the amount of light.

    • Condenser lens: Focuses light onto the specimen.

    • Arm: Supports the microscope.

Carbon-Based Molecules

  1. Four Carbon-Based Molecules:

    • Carbohydrates:

      • Monomer: Monosaccharides (e.g., glucose).

      • Polymer: Polysaccharides (e.g., starch, cellulose).

    • Lipids:

      • Monomer: Fatty acids and glycerol.

      • Polymer: Fats, phospholipids.

    • Proteins:

      • Monomer: Amino acids.

      • Polymer: Polypeptides (proteins).

    • Nucleic Acids:

      • Monomer: Nucleotides.

      • Polymer: DNA, RNA.

  2. Why Carbon is Important: Carbon forms four covalent bonds, allowing it to create diverse and complex molecules essential for life.

Atoms, Ions, and Isotopes

  • Atom: Basic unit of matter (protons, neutrons, electrons).

  • Ion: An atom with a charge due to losing or gaining electrons.

  • Isotope: Atoms of the same element with different numbers of neutrons.

  • Determine Protons, Neutrons, Electrons:

    • Protons: Equal to the atomic number.

    • Neutrons: Atomic mass - atomic number.

    • Electrons: Equal to protons in a neutral atom, but can vary in ions.

Water Properties

  1. Properties:

    • Cohesion: Water molecules stick to each other (e.g., surface tension).

    • Adhesion: Water molecules stick to other substances (e.g., capillary action).

    • High Specific Heat: Water absorbs a lot of heat before changing temperature.

    • Universal Solvent: Water dissolves many substances due to its polarity.

Enzymes

  1. How Enzymes Work: Enzymes are proteins that catalyze chemical reactions by lowering the activation energy.

    • Structure: Enzymes have an active site where the substrate binds.

    • Effect of External Factors: Temperature, pH, and concentration can affect enzyme activity.

    • Cricket Lab: Examined how temperature affects enzyme activity.

  2. Enzyme Specificity: Enzymes are specific to substrates due to their shape.

Chemical Reactions

  • Reactants: Substances that undergo the reaction.

  • Products: Substances formed by the reaction.

  • Exothermic Reactions: Release energy (e.g., combustion).

  • Endothermic Reactions: Absorb energy (e.g., photosynthesis).

Polarity

  • Polar: Molecules with unequal charge distribution (e.g., water).

  • Nonpolar: Molecules with equal charge distribution (e.g., oil).

Cell Theory

  • Principles:

    1. All living things are made of cells.

    2. Cells are the basic unit of structure and function.

    3. All cells arise from pre-existing cells.

Cell Structure & Function

  1. Parts of the Cell:

    • Nucleus: Contains DNA.

    • Mitochondria: Powerhouse of the cell (cellular respiration).

    • Endoplasmic Reticulum (ER): Rough ER (protein synthesis) and smooth ER (lipid synthesis).

    • Golgi Apparatus: Modifies and packages proteins.

    • Ribosomes: Protein synthesis.

    • Cytoplasm: Fluid that holds organelles.

  2. Eukaryotic vs. Prokaryotic Cells:

    • Eukaryotic: Have membrane-bound organelles (e.g., animals, plants, fungi).

    • Prokaryotic: Lack membrane-bound organelles (e.g., bacteria).

Cell Membrane

  • Selective Permeability: The membrane controls what enters and exits the cell.

  • Fluid Mosaic Model: The membrane is fluid with proteins embedded within it.

  • Phospholipid Bilayer: The cell membrane is composed of two layers of phospholipids.

Transport Mechanisms

  • Passive Transport: Movement of substances down a concentration gradient (no energy required).

    • Simple Diffusion: Movement of small, nonpolar molecules.

    • Facilitated Diffusion: Uses carrier proteins for larger or polar molecules.

    • Osmosis: Diffusion of water through a semipermeable membrane.

  • Active Transport: Movement of substances against the concentration gradient (requires energy).

    • Requires Proteins: For both passive and active transport.

Osmosis and Solutions

  • Types of Solutions:

    • Hypertonic: More solute outside the cell, water moves out.

    • Hypotonic: More solute inside the cell, water moves in.

    • Isotonic: Equal solute concentration, no net movement of water.

Proteins in Cells

  • Roles: Transport (e.g., channels), enzymes, structural support, communication (e.g., receptors).

Cellular Respiration

  1. Equation:
    C6H12O6+6O2→6CO2+6H2O+ATPC_6H_{12}O_6 + 6O_2 =6CO_2 + 6H_2O + AT C6​H12​O6​+6O2​→6CO2​+6H2​O+ATP

  2. Steps:

    • Glycolysis (cytoplasm): Breaks glucose into pyruvate, produces small ATP.

    • Krebs Cycle (mitochondria): Produces electron carriers (NADH, FADH2).

    • Electron Transport Chain (mitochondria): Uses electrons to produce ATP.

  3. Aerobic vs. Anaerobic:

    • Aerobic: Requires oxygen (more ATP).

    • Anaerobic: Occurs without oxygen (produces less ATP).

      • Fermentation (Lactic acid or alcoholic).

Photosynthesis

  1. Equation:
    6CO2+6H2O+light→C6H12O6+6O26CO_2 + 6H_2O + light \rightarrow C_6H_{12}O_6 + 6O_26CO2​+6H2​O+light→C6​H12​O6​+6O2​

  2. Pigment: Chlorophyll absorbs light, primarily blue and red light.

  3. Location: Takes place in chloroplasts (thylakoid membranes for light-dependent reactions, stroma for light-independent reactions).

Mitosis & Meiosis

Mitosis

  • Purpose: Mitosis is the process by which a single eukaryotic cell divides to produce two identical daughter cells. It is used for growth, repair, and asexual reproduction.

  • Organisms: Most eukaryotic organisms (e.g., humans, animals, plants).

  • Phases of Mitosis:

    1. Interphase (precedes mitosis, not part of mitosis itself):

      • G1 phase: Cell grows and prepares for DNA replication.

      • S phase: DNA replication occurs.

      • G2 phase: Cell continues to grow and prepares for mitosis.

    2. Mitosis:

      • Prophase: Chromosomes condense and become visible. The nuclear membrane breaks down. Spindle fibers form from the centrosomes.

      • Metaphase: Chromosomes line up at the cell’s equator (metaphase plate).

      • Anaphase: Sister chromatids are pulled apart toward opposite poles.

      • Telophase: New nuclear membranes form around the separated chromatids. The chromosomes begin to uncoil.

    3. Cytokinesis (often overlaps with telophase):

      • In animal cells, a cleavage furrow forms, pinching the cell membrane to divide the cytoplasm.

      • In plant cells, a cell plate forms, eventually developing into a new cell wall.

  • Daughter Cells: Two genetically identical diploid cells (each with the same chromosome number as the parent cell).

  • Important Note: Mitosis maintains the chromosome number (2n → 2n).

Meiosis

  • Purpose: Meiosis is the process by which a single diploid cell undergoes two rounds of division to produce four genetically diverse haploid cells (gametes — sperm or eggs in animals).

  • Organisms: Occurs in organisms that reproduce sexually (e.g., humans, animals, plants).

  • Phases of Meiosis:

    • Meiosis I (reduction division):

      1. Prophase I: Homologous chromosomes pair up and exchange segments in a process called crossing-over, increasing genetic diversity. The nuclear envelope dissolves, and spindle fibers form.

      2. Metaphase I: Homologous chromosome pairs line up along the metaphase plate (random assortment occurs, which also increases genetic variation).

      3. Anaphase I: Homologous chromosomes are separated, with one chromosome from each pair moving to opposite poles.

      4. Telophase I: Two nuclear membranes form, and the cell divides through cytokinesis, resulting in two haploid cells, each with half the original chromosome number.

    • Meiosis II (similar to mitosis):

      1. Prophase II: Chromosomes condense, and a new spindle forms in both haploid cells.

      2. Metaphase II: Chromosomes line up along the metaphase plate.

      3. Anaphase II: Sister chromatids are separated and move toward opposite poles.

      4. Telophase II: Nuclear membranes form around the chromatids, and cytokinesis occurs.

  • Daughter Cells: Four genetically distinct haploid cells, each with half the chromosome number of the original diploid cell.

  • Important Note: Meiosis results in genetic diversity through crossing-over and independent assortment.

Comparison of Mitosis & Meiosis

Feature

Mitosis

Meiosis

Purpose

Growth, repair, asexual reproduction

Sexual reproduction (gametes)

Number of Divisions

One division (PMAT)

Two divisions (Meiosis I and II)

Chromosome Number

Same as parent (diploid to diploid)

Halved (diploid to haploid)

Number of Daughter Cells

Two identical cells

Four genetically different cells

Genetic Variation

No variation (identical cells)

High variation (crossing-over and independent assortment)

Type of Cells Produced

Somatic cells

Gametes (sperm, eggs)

Chromosome Alignment

Chromosomes line up individually in metaphase

Homologous chromosomes pair in metaphase I

Crossing-Over

Does not occur

Occurs in Prophase I

Key Concepts in Meiosis

  1. Crossing-over: Occurs during Prophase I when homologous chromosomes exchange genetic material, increasing genetic variation in the offspring.

  2. Independent Assortment: During Metaphase I, homologous chromosome pairs line up randomly, so the combination of chromosomes that end up in the gametes is random.

  3. Reduction Division: Meiosis reduces the chromosome number by half, ensuring that when two gametes fuse during fertilization, the resulting zygote has the correct diploid number of chromosomes.

Why Meiosis is Important for Sexual Reproduction

  • Genetic Diversity: The combination of crossing-over, independent assortment, and random fertilization creates genetic diversity, which is essential for evolution and adaptation.

  • Haploid Gametes: Meiosis ensures that gametes (sperm and eggs) are haploid, meaning they contain only one set of chromosomes, which is necessary for maintaining the correct chromosome number after fertilization.

Mitosis vs. Meiosis in Organisms

  • Mitosis: Occurs in somatic cells of all organisms for growth, repair, and asexual reproduction.

  • Meiosis: Occurs in reproductive cells (gametes) in sexually reproducing organisms, ensuring the production of offspring with genetic variation.

Summary

  • Mitosis is used for growth, repair, and asexual reproduction, resulting in two identical diploid cells.

  • Meiosis is used for sexual reproduction, producing four genetically unique haploid gametes, which ensures genetic diversity in offspring.

  • This process involves two rounds of division, meiosis I and meiosis II, where homologous chromosomes are separated in the first division and sister chromatids in the second, ultimately leading to the formation of gametes with half the number of chromosomes.