Biology Review:

Properties of Life and Feedback Mechanisms

• Properties of Life: Essential for the exam. Students should be able to identify which characteristics are considered properties of life and recognize those that are not.

• Feedback Loops: Note that this information may not be present on the lecture PowerPoints but is testable material.

• Negative Feedback: A process that works to decrease a stimulus or result.     - Example: Eating a doughnut increases blood glucose levels; negative feedback mechanisms then act to decrease the amount of glucose in the bloodstream back to a baseline.

• Positive Feedback: A process that enhances or amplifies the effect of a stimulus.     - Example (Chemical/Environmental): A bag of oranges where one orange turns bad, triggering a chemical positive feedback loop that causes the rest of the oranges to turn bad.     - Example (Biological): The hormone oxytocin in the human body.

Basic Chemistry and Isotopes

• Atomic Structure:     - Atomic Number: Defined by the number of protons in an atom. This number is constant for any given element.     - Oxygen: Has an atomic number of $8$.     - Boron ($B$): Has an atomic number of $5$, meaning it always has $5$ protons.     - Carbon ($C$): Always has $6$ protons.

• Isotopes: Atoms of the same element that have the same number of protons but a different number of neutrons.     - Carbon-14: An isotope of carbon. While carbon typically has $6$ electrons, $6$ neutrons, and $6$ protons, the weight changes in isotopes due to the neutron count. (Note: Transcript mentions Carbon 14 in relation to a change of two neutrons).

• Ionization and Charge: If an atom has a charge of $+2$, it can be assumed that it has lost electrons (specifically two electrons).

Molecular Interactions and Water Properties

• Hydrophobicity and Hydrophilicity:     - Hydrophobic: "Water-fearing" molecules that do not interact well with water.     - Hydrophilic: "Water-loving" molecules that interact or dissolve in water.

• Buffers: Substances that minimize changes in pH by accepting or donating protons.

• Bases: Compounds that can accept a proton ($H^+$).

• Functional Groups: Specific groups of atoms that confer specific properties. One specific functional group (pointed to in the review session) is known for its ability to accept protons.

Chemical Reactions and Macromolecules

• Hydrolysis versus Dehydration Synthesis:     - Dehydration Reaction: The process of connecting molecules by removing a water molecule ($H_2O$).     - Hydrolysis: The process of breaking molecules apart by adding a water molecule ($H_2O$).

• Polysaccharides:     - Glycogen: The storage form of glucose (polysaccharide) in animals.     - Starch: The storage form of glucose (polysaccharide) in plants.

• Proteins:     - Structure: Proteins have four structural levels of folding.     - Primary Structure: The basic linear sequence of amino acids, comparable to a string of beads.     - Secondary Structure: Involves the formation of alpha-helix structures, driven by hydrogen bonding between the amino acids.     - Denaturation: High temperatures cause proteins to lose their structure (denature), which affects their function in the body.

• Nucleic Acids: Molecules that make up genetic material.     - DNA and RNA: Students must know the structural and functional differences between these two types of nucleic acids.

Cell Biology and Organelles

• Prokaryotes versus Eukaryotes:     - Prokaryotes: Lack membrane-bound organelles; genetic material is not enclosed in a membrane.     - Eukaryotes: Contain various membrane-bound organelles, such as the mitochondria and the nucleus.

• Cell Communication and Junctions: Important types of communication/structural connections between cells include:     - Tight junctions     - Desmosomes     - Gap junctions

• The Lysosome: Functions as the "garbage can" of the cell, responsible for breaking down waste materials.

• Organelle Function Reference: Review all organelles and their specific functions as part of a comprehensive exam prep.

Membrane Transport and Tonicity

• Tonicity: The ability of a surrounding solution to cause a cell to gain or lose water. There are two specific questions on the test regarding this.     - Salt Solutions: If a cell is placed in a high-salt solution, water will move out of the cell toward the higher solute concentration, causing the cell to shrink.     - Hypotonic vs. Hypertonic: Essential to distinguish between these states and their effects on cell volume.

• Large Molecule Transport:     - Exocytosis: The process where large macromolecules leave the cell via the formation of a vesicle that pops out through the membrane.     - Endocytosis: The process of bringing large macromolecules into the cell.

• Active versus Passive Transport:     - Active Transport: Requires energy in the form of $ATP$ to move substances against their gradient.     - Facilitated Diffusion: A form of passive transport where molecules move through a membrane via specific proteins (e.g., Aquaporins, which facilitate the movement of water) without the use of energy.

• Membrane Permeability: The plasma membrane is selectively permeable.     - Easily Diffused: Small, non-polar molecules can pass through easily.     - Difficulty Passing: Charged particles and large polar molecules generally cannot pass through the membrane without assistance.

Energy, ATP, and Cellular Respiration

• Thermodynamics:     - Exergonic: Reactions that release energy (compared to a bomb releasing energy).     - Endergonic: Reactions that require or absorb energy.

• ATP (Adenosine Triphosphate): Contains high-energy covalent bonds between phosphate groups that act like a "spring." When a phosphate group is released, energy is provided to drive chemical reactions in the cell.

• Cellular Respiration:     - Flow of Electrons: Electrons start with Glucose ($C_6H_{12}O_6$) and are eventually transferred through the system.     - Oxidation/Reduction: In cellular respiration, Glucose is oxidized because it gives up electrons.     - Final Electron Acceptor: In the electron transport chain, Oxygen ($O_2$) is the final electron acceptor.     - Electron Carriers: $FADH$ and $NADH$ serve as carriers that hold and transport electrons.     - Phosphorylation:         - Oxidative Phosphorylation: Drives the majority of $ATP$ production.         - Substrate-level Phosphorylation: An enzyme transfers a phosphate group directly from a substrate to $ADP$. This occurs during Glycolysis and the Citric Acid Cycle (Krebs Cycle).

• Fermentation: Two main types include Alcohol Fermentation and Lactic Acid Fermentation.

Photosynthesis

• Photosynthesis in Plants: Plants use photosynthesis to build up nutrients. It occurs during the day when sunlight is available.

• Plant Respiration: Cellular respiration occurs constantly in plants, breaking down what the plant builds.

• Water Conservation (Cacti/Garden Plants):     - Plants have pores (Stomata) to manage gas and water exchange.     - During the day, some plants (like cacti) close their pores to prevent water loss and wilting.     - At night, they open their pores to take in carbon dioxide ($CO_2$).

• Pigments: The primary purpose of Chlorophyll and other pigments is to absorb light energy from the sun.

• Reaction Components:     - Reactants: Carbon Dioxide ($CO_2$) from the air and Water ($H_2O$).     - Products: Oxygen ($O_2$) and Glucose / Starches.

• The Calvin Cycle: This is the light-independent part of photosynthesis. The carbon source used is Carbon Dioxide ($CO_2$). (Specific numbers or ratios for calculations are not required for the test).

Mitosis, Meiosis, and Genetics

• The Cell Cycle:     - Interphase: The phase of the cell cycle where the cell grows and replicates its DNA.     - Mitosis Phases: Prophase, Prometaphase, Metaphase, Anaphase, and Telophase (sometimes followed by Cytokinesis).

• Mitotic Spindle: A structure that plays a critical role in lining up and separating chromosomes during cell division.

• Genetics Definitions:     - Gene: A basic unit of heredity.     - Allele: A specific version or variation of a gene (e.g., everyone has genes for hair, but alleles determine the specific color or type).

• Meiosis:     - Independent Assortment: The random separation of homologous chromosomes during meiosis, which contributes to genetic variation.     - Law of Segregation: One of Mendel's principles regarding how alleles separate into different gametes.