Honors Bio Semester 1 Exam
Definitions & Concepts
Active Site
Definition: The region on an enzyme where the substrate (reactant) binds during a chemical reaction.
Function: This is where the enzyme catalyzes the conversion of substrate(s) into product(s).
Aerobic
Definition: A process that requires oxygen to produce energy.
Example: Cellular respiration (glucose + oxygen → energy, carbon dioxide, and water).
Anaerobic
Definition: A process that does not require oxygen.
Example: Fermentation (e.g., lactic acid fermentation in muscles).
Asexual Reproduction
Definition: Reproduction where offspring are produced from a single parent without the fusion of gametes.
Result: Offspring are genetically identical to the parent (a clone).
Examples: Binary fission in bacteria, budding in yeast.
Autosomes
Definition: Chromosomes that do not determine sex.
Humans: There are 22 pairs of autosomes, making up 44 chromosomes total.
Function: Carry the majority of an individual's genetic information (e.g., eye color, height).
Biodiversity
Definition: The variety of life on Earth, including species, ecosystems, and genetic variation.
Highest Biodiversity: Tropical regions, particularly rainforests like the Amazon rainforest.
Carbohydrates
Definition: Organic compounds made of carbon, hydrogen, and oxygen.
Function: Provide energy for cells.
Examples: Bread, rice, pasta, fruits, vegetables.
Carbon Cycle
Definition: The movement of carbon through Earth's atmosphere, biosphere, geosphere, and hydrosphere.
Organic Carbon: Found in plants, animals, and living organisms.
Inorganic Carbon: Found in CO₂, carbonates in rocks, and fossil fuels.
Catalyst
Definition: A substance that speeds up a chemical reaction without being consumed or permanently altered.
Function: Lowers the activation energy of a reaction, making it proceed faster.
Example: Enzymes are biological catalysts.
Centromere
Definition: The region of a chromosome where two sister chromatids are held together.
Function: Crucial for chromosome movement during cell division (attachment site for spindle fibers).
Compound
Definition: A substance made up of two or more different elements chemically bonded together.
Example: H₂O (water), CO₂ (carbon dioxide).
Concentration Gradient
Definition: The difference in the concentration of a substance between two areas.
Example: Substances move from areas of high concentration to low concentration, a process called diffusion.
Consumers (Heterotrophs)
Definition: Organisms that cannot produce their own food and obtain energy by consuming other organisms.
Examples: Animals, fungi, and certain bacteria.
Cytoplasm
Definition: The jelly-like substance inside the cell, between the cell membrane and the nucleus.
Function: Holds organelles in place and is the site for many biochemical reactions.
Dehydration Synthesis
Definition: A chemical reaction where two molecules are joined together by removing a water molecule.
Example: Joining two monosaccharides (glucose + fructose) to form sucrose (a disaccharide).
Dependent Variable
Definition: The variable that is measured or observed in an experiment, depending on the independent variable.
Graph Representation: Typically plotted on the y-axis of a graph.
Example: In a plant growth experiment, the dependent variable might be the plant height.
Diploid
Definition: A cell that contains two complete sets of chromosomes (2n).
Examples in Humans: Somatic cells (e.g., skin, muscle cells) have 46 chromosomes (23 pairs).
Electron Transport Chain (ETC)
Definition: A series of protein complexes in the inner mitochondrial membrane that transfers electrons and pumps protons (H⁺) to produce ATP.
Location: Inner mitochondrial membrane.
Function: Drives ATP synthesis in aerobic respiration.
Element
Definition: A pure substance made up of only one type of atom.
Examples: Carbon (C), Oxygen (O), Hydrogen (H).
Enzyme
Definition: A protein that catalyzes biochemical reactions, speeding them up by lowering the activation energy.
Example: Amylase breaks down starch into sugars.
Facilitated Diffusion
Definition: Passive transport of molecules across a membrane via a protein channel or carrier.
Example: Glucose entering a cell via GLUT transporters.
Fermentation
Definition: An anaerobic process by which energy is produced without oxygen.
Types:
Lactic Acid Fermentation: Occurs in muscle cells and certain bacteria, producing lactic acid.
Alcoholic Fermentation: Occurs in yeast, producing ethanol and CO₂.
Fertilization
Definition: The union of male and female gametes (sperm and egg) to form a zygote.
Result: Restores the diploid chromosome number.
Fluid Mosaic Model
Definition: Describes the structure of the cell membrane as a "mosaic" of proteins floating in a fluid lipid bilayer.
Function: Allows the membrane to be flexible and proteins to move laterally within the membrane.
Gametes (Sex Cells)
Definition: Haploid cells involved in sexual reproduction.
Examples in Humans: Sperm (male) and egg (female), each containing 23 chromosomes.
Gametogenesis
Definition: The process by which gametes (sperm and eggs) are produced.
Male: Spermatogenesis (produces sperm).
Female: Oogenesis (produces eggs).
Glycolysis
Definition: The first step in cellular respiration, where glucose is broken down into pyruvate.
Location: Cytoplasm.
Outcome: Produces 2 ATP and 2 NADH molecules.
Grana
Definition: Stacks of thylakoids inside the chloroplast.
Function: Site of the light-dependent reactions in photosynthesis.
Haploid
Definition: A cell that contains only one set of chromosomes (n).
Examples in Humans: Gametes (sperm and egg), each with 23 chromosomes.
Homeostasis
Definition: The regulation of a stable internal environment within an organism.
Examples: Regulation of body temperature, pH, and blood sugar levels.
Homologous Chromosomes
Definition: Chromosome pairs that have the same genes at the same loci, but possibly different alleles.
Example: Chromosome 1 from the mother and chromosome 1 from the father.
Hydrolysis
Definition: A chemical reaction where water is used to break down a molecule into smaller parts.
Example: The breakdown of ATP into ADP and a phosphate group releases energy.
Hypertonic
Definition: A solution with a higher concentration of solutes than another solution.
Effect on Cells: Water moves out of the cell, causing it to shrink.
Hypothesis
Definition: A testable and falsifiable explanation for a phenomenon.
Good Hypothesis: Specific, based on prior knowledge, testable, and predictive.
Example: "If plants are given more light, they will grow taller."
Hypotonic
Definition: A solution with a lower concentration of solutes compared to another solution.
Effect on Cells: Water moves into the cell, causing it to swell.
Independent Variable
Definition: The variable that is manipulated or changed in an experiment.
Graph Representation: Typically plotted on the x-axis of a graph.
Example: In a plant experiment, the amount of light provided to the plants.
Inner Membrane
Definition: The inner layer of a double-membraned organelle like the mitochondrion or chloroplast.
Function: Contains proteins for processes like the electron transport chain in mitochondria.
Inner Membrane Space
Definition: The space between the inner and outer membranes of an organelle.
Example: In mitochondria, it contains protons pumped across the inner membrane during cellular respiration.
Ion
Definition: An atom or molecule with a net electric charge due to the loss or gain of electrons.
Examples: Na⁺ (sodium ion), Cl⁻ (chloride ion).
Isotonic
Definition: A solution with the same concentration of solutes as another solution.
Effect on Cells: No net movement of water into or out of the cell.
Karyotype
Definition: A visual representation of an organism's
complete set of chromosomes.
Use: Used to check for chromosomal abnormalities (e.g., Down syndrome).
Krebs Cycle
Definition: A series of chemical reactions in the mitochondria that produce energy-rich molecules (NADH, FADH₂) and ATP.
Location: Mitochondrial matrix.
Outcome: Produces 2 ATP, 6 NADH, and 2 FADH₂ per glucose molecule.
Light-Dependent Reactions
Definition: The first stage of photosynthesis that requires light to produce ATP and NADPH.
Location: Thylakoid membranes of the chloroplast.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.
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
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).
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: Holds the slide.
Diaphragm: Controls the amount of light.
Condenser lens: Focuses light onto the specimen.
Arm: Supports the microscope.
Carbon-Based Molecules
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.
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
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
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.
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:
All living things are made of cells.
Cells are the basic unit of structure and function.
All cells arise from pre-existing cells.
Cell Structure & Function
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.
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
Equation:
C6H12O6+6O2→6CO2+6H2O+ATPC_6H_{12}O_6 + 6O_2 =6CO_2 + 6H_2O + AT C6H12O6+6O2→6CO2+6H2O+ATPSteps:
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.
Aerobic vs. Anaerobic:
Aerobic: Requires oxygen (more ATP).
Anaerobic: Occurs without oxygen (produces less ATP).
Fermentation (Lactic acid or alcoholic).
Photosynthesis
Equation:
6CO2+6H2O+light→C6H12O6+6O26CO_2 + 6H_2O + light \rightarrow C_6H_{12}O_6 + 6O_26CO2+6H2O+light→C6H12O6+6O2Pigment: Chlorophyll absorbs light, primarily blue and red light.
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:
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.
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.
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):
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.
Metaphase I: Homologous chromosome pairs line up along the metaphase plate (random assortment occurs, which also increases genetic variation).
Anaphase I: Homologous chromosomes are separated, with one chromosome from each pair moving to opposite poles.
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):
Prophase II: Chromosomes condense, and a new spindle forms in both haploid cells.
Metaphase II: Chromosomes line up along the metaphase plate.
Anaphase II: Sister chromatids are separated and move toward opposite poles.
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
Key Concepts in Meiosis
Crossing-over: Occurs during Prophase I when homologous chromosomes exchange genetic material, increasing genetic variation in the offspring.
Independent Assortment: During Metaphase I, homologous chromosome pairs line up randomly, so the combination of chromosomes that end up in the gametes is random.
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.