^Definition:

• ^{Energy plateau that needs to be overcome in order for a reaction to occur.}

• ^{Factors: Temperature, pH, concentration, and pressure.}

^Example:

• ^{Glycolysis, cellular respiration, and photosynthesis. Enzymes reduce activation energy.}

^{Process it Supports: Enzymes lower activation energy to enable life-sustaining reactions at normal body temperatures.}

• ^{Optimize chemical processes, improve efficiency, and reduce energy consumption.}

^Definition:

• ^{Process in which a single gene can produce multiple mRNA variants by including or excluding specific exons during RNA processing.}

^Example:

• ^{Tumor suppressor p53 protein, undergoes alternative splicing to generate multiple isoforms. Different p53 variants regulate various cellular processes, such as DNA repair, apoptosis, and cell cycle control.}

^{Process it Supports:}

• ^{Mis regulation of alternative splicing can cause cancer and genetic conditions.}

^Definition:

• ^{Type of cellular respiration that occurs without oxygen, using an alternative electron acceptor (like sulfate, nitrate, or carbon dioxide) to make ATP.}

^Example:

• ^{Lactic Acid Fermentation in Human Muscles}

^{Process it Supports:}

• ^{Generates byproducts like lactic acid or ethanol; occurs in cytoplasm (in contrast to aerobic respiration, which takes place in the mitochondria).}

• ^{Common in prokaryotes (bacteria, archaea) and some eukaryotic cells under low-oxygen conditions (like the human gut).}

^Definition:

• ^{Uncontrolled cell growth and division due to genetic mutations that disrupt normal cell cycle regulation. These abnormal cells escape programmed cell death (apoptosis), proliferate uncontrollably, and can invade surrounding tissues or spread to distant parts of the body (metastasis).}

^{Example: Breast Cancer}

• ^{Affects breast tissue and can spread to nearby lymph nodes if not treated.}

^{Process it Supports:}

• ^{Mutations in genes like p53 can increase cancer risk; lifestyle factors such as smoking, diet, radiation exposure, and infections (HPV for cervical cancer).}

^Definition:

• ^{Ensures the proper progression of the cell cycle by detecting DNA damage, incomplete replication, or misaligned chromosomes. If errors are found, the checkpoint either pauses the cycle for repair or triggers apoptosis (programmed cell death) to prevent the propagation of faulty cells.}

^{Example: The cell cycle (G1, S, G2, M phases).}

^{Process it Supports: Prevents Cancer}

• ^{Malfunctioning checkpoints allow mutated cells to divide uncontrollably, leading to cancer. Many tumors have defective p53 or other checkpoint proteins.}

^Definition:

• ^{DNA → RNA → Protein}

^{Explains how genetic instructions stored in DNA are transcribed into RNA and then translated into functional proteins that drive cellular processes.}

^Example:

• ^{The immunoglobulin heavy chain (IgH) gene is involved in producing antibodies (immunoglobulins) that fight infections.}

^Composition:

• ^{Protein Synthesis: Ensures cells produce the proteins they need to function.}

• ^{Cell Differentiation: Different gene expression patterns create specialized cells like neurons and muscle cells.}

^Definition:

^{Green pigment found in plants, algae, and some bacteria that absorbs light energy.}

^Example:

• ^{In plant cells, chlorophyll is found in the chloroplasts and is responsible for capturing sunlight.}

^{Process it Supports: Oxygen Production}

• ^{After absorbing light, chlorophyll excites electrons. Then they are transferred through the electron transport chain, driving the production of ATP and NADPH used in the Calvin cycle to produce glucose.}

^{Visualization}

^Definition:

^{Complex of DNA and proteins, like histones, that make up chromosomes in the nucleus of eukaryotic cells.}

^Example:

^{During Interphase}

• ^{Chromatin is loose and spread out in the nucleus, allowing for the transcription of genes.}

^Composition:

• ^{It exists in two forms: euchromatin (loosely packed = active in gene expression) and heterochromatin (tightly packed = inactive).}

^{Significance: These activities release greenhouse gases (GHGs) like carbon dioxide (CO2) which trap heat and lead to the warming of the planet.}

^{Example: Melting Polar Ice Caps}

• ^{The Arctic has warmed at about twice the global average rate, causing glaciers and ice caps to melt at an accelerated rate, contributing to rising sea levels.}

^{Process it is a part of: Rising Sea Levels}

• ^{As glaciers and ice sheets melt, and oceans expand due to warming, sea levels rise, threatening coastal cities, marine life, and ecosystems.}

^{Definition: Specific pairing of nitrogenous bases in DNA and RNA held together by hydrogen bonds.}

^{Example: DNA Replication}

• ^{Two strands of the helix separate, and each serve as a template for a new complementary strand. In DNA, if one strand has the sequence A-T-G-C, the complementary strand will be T-A-C-G.}

^{Composition/Characteristics: Nitrogenous Bases:}

• ^{Purine: Adenine (A) and Guanine (G) are double-ringed structures. Pyrimidines: Cytosine (C) and Thymine (T) (or uracil (U) in RNA) are single-ringed structures.}

^{Significance: Play a role in energy production by facilitating oxidation-reduction (redox) reactions.}

^{Example: Lactate Dehydrogenase (LDH):}

• ^{Lactate dehydrogenase converts lactate to pyruvate during anaerobic respiration. This process regenerates NAD+ from NADH and allows glycolysis to continue.}

^{Function: Oxidation-Reduction (Redox) Reactions: Dehydrogenases facilitate the transfer of electrons (as hydrogen atoms) from one molecule to another, thereby assisting in redox reactions. "OIL RIG"}

^{Significance: Ensures that each daughter cell gets an identical copy of the genetic material.}

^{Example: DNA polymerase reads 3' to 5'. It can also correct mistakes in base pairing during replication. If a wrong nucleotide is added, the enzyme removes it and adds the correct one.}

^{Context of Significance: Cell Division and Growth}

• ^{Without DNA polymerase, the cell would not be able to replicate its DNA, leading to failure in cell division.}

^Composition:

• ^{Active Site: Where the incoming nucleotides are added to the growing DNA strand in a 5' to 3' direction.}

^{Context: DNA replication is semiconservative, meaning each of the two new DNA molecules consists of one original strand and one newly synthesized strand.}

^{Example: The origin of replication is recognized, and the DNA is unwound by helicase. Then DNA polymerase synthesizes new strands by adding nucleotides that are complementary to the template strand.}

^{Composition/Characteristics:}

^{Enzymes Involved:}

• ^{Helicase: Unwinds the double helix by breaking hydrogen bonds between base pairs.}

• ^{DNA polymerase III: Adds complementary nucleotides to the growing DNA strand.}

• ^{DNA polymerase I: Removes RNA primers and replaces them with DNA.}

• ^{Primase: Synthesizes short RNA primers to start the replication process.}

• ^{Ligase: Joins Okazaki fragments on the lagging strand.}

• ^{Topoisomerase: Relieves the tension generated ahead of the replication fork by making temporary cuts in the DNA.}

^{Context: The dominant allele is typically represented by a capital letter. If an individual carries both a dominant allele and a recessive allele for a particular trait, the dominant allele will determine the organism's phenotype.}

^{Example: Human Eye Color}

• ^{Brown eye color (represented by capital B) is dominant over blue eye color (represented by lower case b). A person with the genotype Bb (one brown allele and one blue allele) will have brown eyes because the brown allele is dominant.}

^{Process it Supports: Genetic Disorders:}

• ^{Some genetic diseases are caused by dominant alleles. For example, Huntington's disease is caused by a dominant allele, meaning an individual only needs one copy of the gene to develop the disease.}

^{Significance: For a recessive allele to be expressed in the phenotype, an individual must inherit two copies of the recessive allele—one from each parent (homozygous recessive genotype, aa). If only one copy of the recessive allele is present (heterozygous genotype, Aa), the dominant allele will determine the phenotype.}

^{Example: In Gregor Mendel's experiments with pea plants, white flower color was caused by a recessive allele (p), while purple flower color was caused by a dominant allele (P).}

• ^{A pea plant with the genotype pp (homozygous recessive) will have white flowers, as it lacks the dominant P allele to mask the recessive trait. If the plant is Pp (heterozygous), it will have purple flowers because the dominant P allele masks the recessive p allele.}

^{Context of Significance:}

^{Recessive Inheritance:}

• ^{Recessive alleles are important for understanding inheritance patterns. For a recessive trait to be expressed, both parents must either carry the recessive allele (heterozygous) or express it themselves (homozygous recessive).}

^{Genetic Disorders:}

• ^{Some genetic disorders, such as sickle cell anemia, are caused by recessive alleles. An individual must inherit two copies of the recessive allele (one from each parent) to develop the disorder.}

^{It's a series of protein complexes and other molecules that transfer electrons from electron carriers (NADH and FADH2) to oxygen molecules through a series of redox reactions, ultimately producing ATP and water.}

^{Context/Significance: The ETC plays a crucial role in cellular energy production, contributing to oxidative phosphorylation.}

^Example:

^{Human Cellular Respiration:}

• ^{In human cells, after glycolysis and the citric acid cycle (Krebs cycle), NADH and FADH2 carry high-energy electrons to the electron transport chain.}

^{Composition/Characteristics:}

^{Protein Complexes:}

• ^{Complex I: Transfers electrons from NADH to coenzyme Q and pumps protons into the intermembrane space.}

• ^{Complex II: Transfers electrons from FADH 2 to ubiquinone but does not pump protons.}

• ^{Complex III: Transfers electrons from ubiquinone to cytochrome c and pumps protons.}

• ^{Complex IV: Transfers electrons to oxygen, forming water, and pumps protons.}

• ^{Coenzyme Q and Cytochrome c: Electron carriers that shuttle electrons between complexes.}

• ^{ATP Synthase: A protein complex that uses the proton gradient to generate ATP by allowing protons to flow back into the matrix, driving the conversion of ADP to ATP.}

^{The products have more free energy than the reactants, meaning the process is not spontaneous. The change in free energy is positive in endergonic reactions.}

^{Significance: These reactions are typically associated with biosynthesis and processes that build molecules (anabolic) or store energy, such as photosynthesis.}

^Example:

^{Photosynthesis in plants:}

• ^{Photosynthesis is an endergonic reaction because plants absorb light energy and convert carbon dioxide and water into glucose (C6H12O6) and oxygen. The energy required to drive this reaction comes from sunlight making it endergonic because it is an energy-consuming process.}

  
  

^Function:

^{Energy Storage:}

• ^{Endergonic reactions allow cells to store energy by building complex molecules from simpler ones. For example, in photosynthesis, light energy is stored in the chemical bonds of glucose molecules, which can later be used as a source of energy for cellular processes.}

^{Molecule Synthesis:}

• ^{These reactions are essential for the biosynthesis of complex molecules like proteins, nucleic acids, lipids, and carbohydrates, which are crucial for cell structure and function.}

^{A type of chemical reaction that releases energy as it proceeds. In these reactions, the products have less free energy than the reactants, meaning the process is spontaneous. The change in free energy is negative in exergonic reactions.}

^{Significance: These reactions are typically associated with catabolic processes, where larger molecules are broken down into smaller molecules, releasing energy that can be used for cellular functions.}

^Example:

^{Cellular Respiration:}

• ^{Cellular respiration is a prime example of an exergonic reaction. In this process, glucose (C6H12O6) is broken down into carbon dioxide and water, releasing energy that is used to produce ATP. The energy released is harnessed to power cellular functions, making the reaction exergonic.}

^Function:

^{Energy Release:}

• ^{The function of exergonic reactions is to release energy that can be used by the cell for various activities. This includes providing the energy necessary for biosynthesis, muscle contraction, cell division, and maintaining homeostasis.}

^{Driving Cellular Processes:}

• ^{Exergonic reactions power endergonic reactions. The energy released from exergonic reactions is often used to drive energy-consuming processes, such as the synthesis of ATP, protein synthesis, or active transport across membranes.}

^{A cellular process in which cells engulf external substances and bring them into the cell by forming vesicles. It is a type of active transport that requires energy (usually in the form of ATP) to move materials from outside the cell into the cytoplasm.}

^{Context/Significance: Endocytosis allows cells to take in large molecules, such as nutrients, hormones, viruses, and other substances that cannot pass through the cell membrane directly.}

^Example:

^{Phagocytosis in Immune Cells:}

• ^{In phagocytosis, a type of endocytosis, white blood cells (e.g., macrophages) engulf pathogens (such as bacteria) or debris. The cell membrane extends around the pathogen, forming a vesicle called a phagosome, which then fuses with a lysosome to digest the material.}

^{Composition/Characteristics:}

^{Types of Endocytosis:}

• ^{Phagocytosis: The process by which cells engulf large particles such as debris or pathogens.}

• ^{Pinocytosis: Often referred to as "cell drinking," it involves the uptake of extracellular fluid and dissolved solutes into small vesicles.}

^{Process by which cells expel substances from the cytoplasm to the outside of the cell. This process involves the fusion of vesicles containing cellular material with the plasma membrane, releasing the contents into the extracellular space.}

^{Context/Significance: Exocytosis is essential for processes such as secretion, waste removal, and membrane recycling.}

^Example:

^{Insulin Secretion:}

• ^{Pancreatic beta cells release insulin via exocytosis. After glucose is detected in the blood, the cells release insulin stored in vesicles into the bloodstream to regulate blood sugar levels.}

  
  

^{Process/Structure it Supports:}

^{Hormone Secretion:}

• ^{Exocytosis supports the release of hormones like insulin, adrenaline, and growth factors from endocrine cells into the bloodstream, helping regulate various bodily functions.}

^{Cells that have a true nucleus and membrane-bound organelles. Found in organisms in the kingdoms of Animals, Plants, Fungi, and Protists.}

^{Context/Significance: Eukaryotic cells are more complex than prokaryotic cells, which do not have a nucleus or membrane-bound organelles.}

^Example:

^{Animal Cells:}

• ^{Human cells, as well as the cells of all other animals, are eukaryotic. They contain structures such as the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus.}

  
  

^{Composition/Characteristics:}

^Nucleus:

• ^{The defining feature of eukaryotic cells is the presence of a nucleus, a membrane-bound structure that contains the cell’s genetic material (DNA). This allows for the storage and protection of DNA.}

^{Membrane-Bound Organelles:}

• ^{Eukaryotic cells contain various organelles, each enclosed by membranes, such as:}

• ^{Mitochondria, Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, and chloroplasts.}

^{Larger Size:}

• ^{Eukaryotic cells are generally larger than prokaryotic cells and can be more complex in their internal organization.}

^{A type of passive transport in which molecules move across the cell membrane through protein channels or carriers without requiring energy.}

^{Context/Significance: This process helps molecules that are too large or polar (and cannot diffuse freely through the lipid bilayer) to cross the membrane down their concentration gradient (from high to low concentration).}

^Example:

^{Glucose Transport:}

• ^{Glucose moves into the cell through glucose transporter proteins. Since glucose is a large and polar molecule, it cannot diffuse through the lipid bilayer directly. Instead, it binds to a glucose transporter protein, which undergoes a change and allows glucose to move into the cell, following its concentration gradient.}

^{Context of Significance:}

^{Protein Channels:}

• ^{Channel proteins form pores in the membrane that allow specific molecules or ions to pass through. These channels may be gated, meaning they open or close in response to specific signals or changes in the environment.}

^{Regulatory mechanism in biochemical pathways where the end product of a pathway inhibits an enzyme that is involved earlier in the pathway, thereby preventing overproduction of that product.}

^{Significance: It is a form of negative feedback, where the accumulation of a substance signals the system to slow down or stop production, helping maintain homeostasis and prevent excessive accumulation.}

^Example:

^{Regulation of ATP Production:}

• ^{In cellular respiration, the production of ATP can inhibit key enzymes in the glycolysis pathway (such as phosphofructokinase). When ATP levels are high, glycolysis slows down, preventing unnecessary consumption of resources. When ATP is low, the pathway speeds up to produce more ATP.}

^{Context of Significance:}

^Homeostasis:

• ^{Feedback inhibition is essential for maintaining balance within cells and organisms. By regulating the production of molecules, cells avoid wasting energy and resources.}

^{Enzyme Regulation:}

• ^{The key feature of feedback inhibition is the inhibition of enzyme activity. This usually happens when the end product of a pathway binds to the allosteric site of an enzyme, causing a conformational change that reduces its activity.}

^{Metabolic process that produces energy (ATP) through the breakdown of organic molecules (usually glucose) in the absence of oxygen. It is an anaerobic process, meaning it does not require oxygen.}

^{Context/Significance: Fermentation enables cells to continue producing ATP when oxygen is scarce or unavailable, though it is much less efficient than aerobic respiration.}

^Example:

^{Lactic Acid Fermentation (Muscle Cells):}

• ^{In muscle cells during intense exercise, when oxygen is not available for aerobic respiration, glucose is converted to lactic acid (lactate) to produce ATP. This process is less efficient and can lead to muscle fatigue due to the accumulation of lactate.}

^{Composition/Characteristics:}

^{Anaerobic Process:}

• ^{Fermentation occurs in the absence of oxygen. Unlike aerobic respiration, which involves the electron transport chain and oxygen as the final electron acceptor, fermentation does not use oxygen and operates through other biochemical pathways.}

^{Substrate-Level Phosphorylation:}

• ^{ATP is produced through substrate-level phosphorylation, which involves the transfer of a phosphate group from an organic molecule (such as glucose) to ADP to form ATP.}

^{A segment of DNA that contains the instructions for making a specific protein or RNA molecule.}

^{Context/Significance: The sequence of nucleotides in a gene encodes the information needed to synthesize proteins or functional RNA molecules, which carry out a wide range of activities in cells.}

^Example:

^{Human Hemoglobin Gene (HBB):}

• ^{The HBB gene encodes the hemoglobin protein, which is responsible for carrying oxygen in red blood cells. Variations or mutations in the HBB gene can lead to genetic disorders like sickle cell anemia, where the hemoglobin protein is abnormal, affecting its ability to carry oxygen properly.}

^{Context of Significance:}

^{Gene Expression:}

• ^{The process by which a gene's information is used to synthesize a functional product, typically a protein or RNA, is called gene expression. This process includes both transcription (making RNA) and translation (making protein).}

^{A covalent bond formed between two monosaccharides through a dehydration reaction, where a molecule of water is released. This linkage connects the anomeric carbon of one sugar molecule to a hydroxyl group (-OH) of another sugar.}

^{Context/Significance: Glycosidic linkages are crucial for the formation of molecules, such as starch, cellulose, and glycogen.}

^Example:

^{Lactose (Milk Sugar):}

• ^{Lactose is a disaccharide made up of galactose and glucose, connected by a glycosidic bond between the anomeric carbon of galactose and the hydroxyl group of glucose.}

^{Composition/Characteristics:}

^{Dehydration Reaction:}

• ^{A glycosidic bond is formed through a condensation reaction (also called dehydration), where a hydroxyl group (-OH) from one sugar and a hydrogen atom (H) from another sugar combine to form water (H₂O). This removes a water molecule and creates the bond between the two sugars.}

^{Refers to a cell or organism that contains one complete set of chromosomes—half the number of chromosomes found in a diploid cell.}

^{Context: In organisms that reproduce sexually, haploid cells are typically the gametes (sperm and egg cells) and are involved in sexual reproduction. After fertilization, the two haploid gametes combine to form a diploid zygote.}

^Example:

^{Human Gametes:}

• ^{In humans, the haploid number of chromosomes is 23. The sperm cell from the father and the egg cell from the mother each contain 23 chromosomes. When they combine during fertilization, the resulting zygote has 46 chromosomes, or 23 pairs, making it diploid.}

^{Context of Significance:}

^{Sexual Reproduction:}

• ^{Haploid cells are crucial for sexual reproduction, as they allow the fusion of male and female gametes (sperm and egg) during fertilization, restoring the diploid chromosome number in the zygote. This process ensures genetic diversity and stability in the offspring.}

^{A weak electrostatic attraction between a hydrogen atom (H) covalently bonded to an electronegative atom (such as oxygen (O), nitrogen (N), or fluorine (F)) and another electronegative atom in a nearby molecule or within the same molecule.}

^{Context/Significance: Hydrogen bonds can break and reform quickly, allowing processes like DNA replication and protein folding to occur efficiently.}

^Example:

^{Protein Folding:}

• ^{Hydrogen bonds help stabilize the secondary structure of proteins, such as the alpha-helix and beta-sheet structures in enzymes and structural proteins.}

^{Composition/Characteristics:}

• ^{Hydrogen bonding in water gives it cohesion, high heat capacity, and solvent properties, making it essential for sustaining life.}

^{Context/Significance: Mendelian Genetics:}

• ^{This principle, formulated by Gregor Mendel, is one of the foundations of classical genetics and helps explain how traits are inherited across generations.}

^{Example: Human Traits:}

• ^{A child may inherit brown eyes from one parent and curly hair from another, because the genes for eye color and hair texture assort independently.}

^{Process it supports: Genetic Variation:}

• ^{Independent assortment contributes to the vast diversity observed in sexually reproducing organisms. It ensures that different combinations of alleles are passed down, leading to unique genetic makeup in offspring.}

^{States an enzyme’s active site is flexible and undergoes a slight shape change when binding to a specific substrate, improving the fit and enhancing catalytic efficiency. This contrasts with the lock-and-key model, which suggests a rigid fit.}

^{Context: Enhances Enzyme Efficiency:}

• ^{The model explains how enzymes can increase reaction specificity by adjusting their active site to hold substrates more tightly.}

^Example:

^{HIV Protease and Drug Inhibition:}

• ^{Some antiviral drugs work by abusing the induced fit model, binding to viral enzymes in a way that prevents them from properly functioning.}

^{Composition/Characteristics:}

^{Enzyme Flexibility:}

• ^{The active site is not rigid but can change slightly to better fit the substrate.}

^{Higher Specificity:}

• ^{Unlike the lock-and-key model, the induced fit model explains why enzymes can still work efficiently even if substrates are not a perfect fit initially.}

^{Molecules that reduce or prevent enzyme activity by interfering with the enzyme’s ability to bind to its substrate or carry out a reaction.}

^{Context/Significance: Inhibitors can be classified into reversible and irreversible types, affecting enzyme function in different ways.}

^Example:

^{Ibuprofen (Reversible Inhibitor):}

• ^{Ibuprofen reduces the production of prostaglandins by inhibiting enzymes, which cause pain and inflammation.}

^{Composition/Characteristics:}

^{Reversible Inhibitors:}

• ^{Competitive: Bind to the active site, competing with the substrate.}

• ^{Non-competitive: Bind to an allosteric site, changing the enzyme's shape.}

• ^{Uncompetitive: Bind only when the enzyme-substrate complex is formed, locking the substrate in place.}

^{Irreversible Inhibitors:}

• ^{Form permanent covalent bonds with the enzyme, rendering it inactive.}

^{A type of chemical bond formed when one atom transfers one or more electrons to another atom, creating oppositely charged ions that are held together by electrostatic forces.}

^{Context/Significance: This usually occurs between a metal (which loses electrons and becomes a cation) and a nonmetal (which gains electrons and becomes an anion).}

^Example:

^{Sodium Chloride (NaCl - Table Salt):}

^{Sodium (Na) donates one electron to chlorine (Cl), forming Na⁺ (cation) and Cl⁻ (anion).}

^{These oppositely charged ions attract each other, forming an ionic bond.}

^Function:

^{Maintains Cell Function:}

• ^{Sodium (Na⁺) and potassium (K⁺) ions help regulate nerve impulses.}

• ^{Calcium (Ca²⁺) is crucial for muscle contraction and bone formation.}

• ^{Ionic bonds break apart in water, allowing ions to participate in osmosis, nerve signaling, and muscle contractions.}

^{A variant of a chemical element that has the same number of protons but a different number of neutrons in its nucleus.}

^{Context/Significance: This difference in neutron count gives isotopes different atomic masses while maintaining the same chemical properties.}

^Example:

^{Carbon Isotopes:}

• ^{Carbon-12 (¹²C): The most common isotope, with 6 protons and 6 neutrons.}

• ^{Carbon-14 (¹⁴C): A radioactive isotope with 6 protons and 8 neutrons, used in radiocarbon dating.}

^{Composition/Characteristics:}

^{Same Chemical Properties:}

• ^{Since isotopes of an element have the same number of protons and electrons, they behave chemically identical in reactions.}

^{An enzyme that transfers a phosphate group from a high-energy molecule (usually ATP) to a specific substrate, a process called phosphorylation.}

^{Context/Significance: This modification is essential in cell signaling, metabolism, and regulation of protein activity.}

^Example:

^{Cyclin-Dependent Kinases (CDKs - Cell Cycle Regulation):}

^{Phosphorylate proteins to control cell cycle progression, ensuring cells divide at the right time.}

^{Context of Significance:}

^{Cell Signaling & Communication:}

• ^{Kinases regulate signal transduction pathways, controlling how cells respond to their environment like hormone signaling.}

^{ATP Dependency:}

• ^{Kinases require ATP as a phosphate donor, transferring the gamma-phosphate to the substrate.}

^{Regulation by Phosphorylation:}

• ^{Many kinases are themselves activated or inactivated by phosphorylation in signaling cascades.}

^{Organisms with traits best suited to their environment are more likely to survive and reproduce, leading to gradual evolutionary changes over generations.}

^{Context/Significance: Darwin’s finches – He observed that birds on different islands evolved different beak shapes suited for their food sources.}

^Example:

^{Antibiotic resistance in bacteria – Overuse of antibiotics selects for resistant bacteria that survive and multiply.}

^{Composition/Characteristics:}

^{Requires genetic variation within a population.}

^{Operates through differential survival and reproduction.}

^{Environmental pressures (predators, climate) influence which traits are favored.}

^{A cluster of genes controlled by a single promoter, allowing bacteria to regulate genes efficiently.}

^{Context/Significance: Regulates gene expression in response to environmental changes.}

^Example:

^{Lac Operon – Activated when lactose is present, enabling bacteria to metabolize it.}

^{Composition/Characteristics:}

^{Includes a promoter, operator, and structural genes.}

^{The movement of water across a semi-permeable membrane from low solute concentration to high solute concentration.}

^{Context/Significance: Keeps cell turgor pressure in plants and prevents dehydration.}

^{Supports cellular homeostasis and transport across membranes.}

^Example:

^{Red blood cells in hypotonic solution – Water enters the cells, causing them to burst.}

^{Composition/Characteristics:}

^{Passive transport, driven by concentration gradients.}

^{A covalent bond between two amino acids in proteins, formed by dehydration synthesis.}

^{Context/Significance: It supports protein structure, enzyme function, muscle formation.}

^Example:

^{Linking amino acids during protein synthesis in ribosomes.}

^{The main structure of proteins.}

^Function:

^{Holds amino acids together in polypeptide chains.}

^{Context/Significance: Separates cell interior from the environment.}

^{Example: Phospholipid bilayer in the cell membrane bilayer.}

^{Composition/Characteristics:}

• ^{Contains polar phosphate head and nonpolar fatty acid tails.}

• ^{Provides selective permeability in cell membranes.}

^{Context/Significance: Important for solubility, hydrogen bonding, and cell function. Facilitates dissolving solutes and biochemical reactions.}

^{Example: Water (H₂O), Glucose, Amino Acids.}

^Function:

• ^{Contributes to the stability of hydrogen atoms bonding and proteins folding.}

^{Context/Significance: Disease links: Aberrant PTMs are involved in diseases like cancer, diabetes, and neurodegeneration (misfolded tau proteins in Alzheimer’s).}

^{Example: Addition of an acetyl group, often to lysine residues on histones. Acetylation of histones in active gene regions to allow transcription.}

^Function:

• ^{Critical in protein activation, degradation, and cell signaling.}

• ^{Includes phosphorylation and regulates protein stability, localization, and activity.}

^{Context/Significance: Promoters are key players in regulating when, where, and how much of a gene is expressed.}

^{Example: TATA Box in eukaryotic genes: A gene that produces hemoglobin uses a TATA box to begin transcription.}

^{Composition/Characteristics:}

• ^{Located upstream of a gene}

• ^{Controls when and where a gene is transcribed.}

^{Context/Significance: Nerve Function: The Na⁺/K⁺ pump is essential for generating resting membrane potential in neurons.}

^{Example: Sodium-Potassium Pump (Na⁺/K⁺ ATPase) maintains nerve cell function.}

^{Composition/Characteristics:}

• ^{Pumps 3 sodium ions out of the cell and 2 potassium ions into the cell, using 1 ATP molecule.}

• ^{Requires ATP to function. Active transport.}

^{Context/Significance: Many are pathogens (E. coli, Mycobacterium tuberculosis), but many are also beneficial, like gut microbiota which also has E. coli.}

^{Example: Bacteria (Escherichia coli, Streptococcus pneumoniae); Archaea (Methanogens, Halophiles)}

^{Composition/Characteristics:}

• ^{No nucleus (DNA is in a nucleoid region) or membrane-bound organelles (no mitochondria, no ER).}

• ^{Smaller in size (~0.1-5 μm) compared to eukaryotes.}

• ^{Cell wall present in most (except some archaea).}

• ^{Circular DNA and may have plasmids (extra DNA).}

• ^{Binary fission for reproduction (asexual).}

^{Context/Significance: Each codon specifies an amino acid or a stop signal, and the reading frame determines how the ribosome reads the sequence to build a protein.}

^{Example: For the mRNA sequence 5'–AUG GCU UGC UGA–3', the reading frame starts at the first codon (AUG), translating to methionine (start codon). Alanine (GCU), cysteine (UGC), and then a stop codon (UGA).}

^{Composition/Characteristics:}

• ^{Codons: Sequences of three nucleotides (A, U, C, G) that represent an amino acid or a stop signal.}

  • ^{Start codon: The first codon (usually AUG) that begins the translation process.}

  • ^{Stop codon: Codons like UAA, UAG, and UGA that signal the end of translation.}

  • ^{Open reading frame (ORF): The continuous stretch of codons that codes for a protein.}

^{Context/Significance: Ensures the correct alignment of tRNAs and catalyzes the formation of peptide bonds between amino acids.}

^Example:

• ^{During protein synthesis, a ribosome translates the mRNA sequence 5'–AUG GCU UGC–3' into the amino acids methionine (Met), alanine (Ala), and cysteine (Cys).}

^Function:

• ^{The primary function of the ribosome is to initiate protein synthesis by decoding the mRNA sequence into a polypeptide chain.}

^{The start codon is the first codon of a messenger RNA (mRNA) sequence that signals the beginning of protein synthesis.}

^{Context/Significance: It marks where translation begins and directs the assembly of the ribosome at the start of the gene.}

^{Example: AUG (adenine-uracil-guanine) is the start codon in most organisms. It codes for the amino acid methionine in Eukaryotes.}

^{Composition/Characteristics:}

• ^{Composed of a three-nucleotide sequence (AUG in most cases).}

• ^{Always the first codon of the mRNA sequence.}

• ^{Signals translation so that the protein, DNA Polymerase, reads the mRNA correctly from the beginning.}

^{---------------------------------------}

^{Stop Codon Definition:}

^{A stop codon is a specific codon in mRNA that signals the end of translation, instructing the ribosome to release the newly synthesized protein.}

^{Context/Significance: Prevents the addition of further amino acids, marking the end of the translation process.}

^{Example: UAA, UAG, UGA are the three stop codons. They do not code for any amino acids but instead signal the termination of the protein synthesis process.}

^Function:

• ^{Stops translation, causing the ribosome to release the completed protein chain.}

^{A substrate is a molecule or compound that an enzyme acts upon during a biochemical reaction.}

^{Context/Significance: It binds to the active site of the enzyme, where the enzyme catalyzes a specific reaction that alters the substrate.}

^Example:

^{Glucose is the substrate for the enzyme hexokinase, which catalyzes the conversion of glucose to glucose-6-phosphate in the first step of glycolysis.}

^Function:

^{Initiates the enzymatic reaction by binding to the enzyme’s active site.}

^{Important for cellular respiration, photosynthesis, and DNA replication.}

^{Context/Significance:}

^{It provides a quick way for cells to generate ATP, especially when oxygen is not available (during anaerobic conditions).}

^{Example: Krebs Cycle (Citric Acid Cycle):}

• ^{The conversion of succinate to fumarate in one of the reactions generates GTP (which can be converted to ATP), through substrate-level phosphorylation.}

^{Composition/Characteristics:}

• ^{Occurs when a phosphate group is transferred from a high-energy substrate molecule to ADP, forming ATP.}

• ^{Generates ATP directly from substrates without the need for oxygen or complex electron transport mechanisms.}

^{Transcription is the process by which an RNA molecule is synthesized from a DNA template. It involves the conversion of a specific gene on the DNA into a complementary messenger RNA (mRNA) strand.}

^{Context/Significance: This mRNA then carries the genetic information from the nucleus to the cytoplasm for protein synthesis.}

^Example:

^{Transcription of ribosomal RNA (rRNA): rRNA is transcribed from DNA and is a critical component of ribosomes, which are essential for protein synthesis.}

^Function:

• ^{Creates mRNA from a DNA template to carry the genetic code from the DNA in the nucleus to the ribosomes in the cytoplasm.}

• ^{Regulates gene expression by controlling which genes are transcribed into RNA and subsequently translated into proteins.}

^---

^STEPS:

^Initiation:

^{RNA polymerase binds to the promoter region of the gene.}

^{The DNA double helix unwinds to expose the template strand.}

^Elongation:

^{RNA polymerase moves along the template DNA strand, synthesizing a complementary RNA strand.}

^{The RNA strand grows in the 5' to 3' direction, with uracil (U) replacing thymine (T) in the RNA.}

^Termination:

^{RNA polymerase reaches a terminator sequence in the DNA, signaling the end of transcription.}

^{The mRNA is released, and the DNA reforms its double helix.}

^{Transcription factors are proteins that regulate the transcription of specific genes by binding to nearby DNA. They help control the rate at which RNA polymerase transcribes the gene into mRNA, thus regulating gene expression.}

^{Context/Significance:}

^{Mediate Cellular Responses: They respond to external signals or checkpoints to ensure the proper gene expression needed for the cell’s adaptation.}

^Example:

^{p53: A transcription factor that plays a role in the cell cycle checkpoint and responds to DNA damage by activating genes involved in cell cycle arrest or apoptosis.}

^Function:

^{Activate or Repress Transcription: By binding to specific regions of DNA (such as promoters, enhancers, or silencers), transcription factors influence the ability of RNA polymerase to transcribe the gene.}

^{When mRNA is decoded by a ribosome to create a polypeptide chain (protein).}

^{Context/Significance: It is the second step of gene expression, after transcription, where the genetic code carried by mRNA is translated into the amino acid sequence of a protein.}

^Example:

^{Hemoglobin production is initiated when the mRNA for the hemoglobin gene is translated into a protein that binds oxygen in red blood cells.}

^{Process it's a part of/supports:}

^Initiation:

^{The small ribosomal subunit binds to the mRNA at the 5' cap in eukaryotes.}

^{The start codon (AUG) on the mRNA signals the beginning of translation.}

^{The large ribosomal subunit joins the complex, forming a functional ribosome.}

^Elongation:

^{The ribosome moves along the mRNA, reading each codon (a sequence of three nucleotides).}

^{tRNA molecules bring the corresponding amino acids, and the ribosome links them together through peptide bonds, elongating the polypeptide chain.}

^Termination:

^{When the ribosome reaches a stop codon (UAA, UAG, or UGA), translation ends.}

^{The newly synthesized polypeptide is released, and the ribosomal subunits dissociate.}

^{A vesicle is a membrane-bound sac within a cell that transports, stores, or digests substances.}

^{Context/Significance: Vesicles help us understand how materials move inside cells, how cells communicate, and how they maintain balance.}

^Example:

^{Lysosomes is a type of vesicle filled with enzymes that digest unwanted materials inside the cell.}

^{Process it Supports:}

^{Intracellular Transport: Vesicles help move molecules between organelles, ensuring efficient cellular communication and functioning.}

^{A compound made up of only two elements: carbon (C) and hydrogen (H).}

^{Significance: Hydrocarbons are the primary building blocks of many organic compounds and are found in natural sources like crude oil, natural gas, and coal.}

^Example:

^{Methane (CH4):}

• ^{Methane is a simple alkane (saturated hydrocarbon) consisting of one carbon atom bonded to four hydrogen atoms. It is the main component of natural gas and is used as a fuel.}

^{Context of Significance:}

^{Energy Source:}

• ^{Hydrocarbons are a major source of energy. When burned, they release energy in the form of heat, which can be harnessed for electricity generation, heating, and powering vehicles. The combustion of hydrocarbons produces carbon dioxide (CO₂) and water vapor as by-products.}

^{A molecule that has no significant charge separation, meaning it is hydrophobic and does not dissolve in water.}

^{Context/Significance: Forms cell membranes, stores energy in fats, and allows gas exchange.}

^Example:

^{Lipids, fats, oils, and gases like O₂ and CO₂.}

^{Composition/Characteristics:}

^{Made of covalent bonds with equal electron sharing. Hydrocarbons.}

^{"aero-" refers to air or oxygen-related processes in biology.}

^Example:

^{Aerobic Respiration: A metabolic process where cells use oxygen to break down glucose for energy (ATP production).}

^{Composition/Characteristics:}

^{Involves Oxygen: Any process labeled with "aero-" generally requires or interacts with oxygen or air. Important for cellular respiration.}

^{The prefix "auto-" means "self-regulating". In biology, we learned about autotrophs and how they are self-sufficient by making their own food.}

^Example:

^{Autotrophs: Organisms like plants and algae that produce their own food via photosynthesis (cyanobacteria and trees).}

^{Process/Structure it Supports:}

^{Photosynthesis & Chemosynthesis (Energy Production in Autotrophs)}

^{The prefix "cyto-" comes from the Greek word kytos, meaning "cell" or "hollow container."}

^Example:

^{Cytoplasm: The gel-like substance inside a cell that surrounds organelles and supports cellular functions.}

^{Composition/Characteristics:}

^{Involves internal cellular structures.}

^{The prefix "haplo-" comes from the Greek word haploos, meaning "single" or "simple." In biology, it typically refers to having a single set of chromosomes rather than paired sets.}

^Example:

^{Haploid Cells: Cells that contain only one set of chromosomes (n), such as gametes (sperm and egg cells) in humans.}

^{Context of Significance:}

^{Sexual Reproduction: Haploid sperm and egg cells combine to form a diploid zygote, which increases genetic diversity.}

^{The prefix "endo-" comes from the Greek word éndon, meaning "within" or "inside." It is used in biology and chemistry to describe the behavior or a process of something.}

^Example:

^{Endocytosis: The process by which a cell engulfs external materials (nutrients, bacteria) into its cytoplasm using vesicles. Endo-related processes help regulate nutrient intake and how organelles function.}

^{The prefix "exo-" comes from the Greek word exō, meaning "outside" or "external." It describes processes, structures, or reactions that occur outside a system, cell, or organism.}

^Example:

^{Exocytosis: The process by which a cell expels molecules (hormones, waste, neurotransmitters) through vesicles, pores, vessels/lymph nodes.}

^{The prefix "hetero-" comes from the Greek word heteros, meaning "different" or "other." It is used in biology, chemistry, and other sciences to describe things that are diverse.}

^Example:

^{Heterotroph: An organism that cannot produce its own food and must obtain nutrients by consuming other organisms (humans, animals, fungi).}

^{The prefix "hyper-" comes from the Greek word huper, meaning "above," "excessive," or "beyond." It is used to describe an increase, excess, or overactivity of a certain process or condition.}

^Example:

^{A hypertonic solution that has a higher solute concentration compared to another solution, causing water to move out of a cell (saltwater causing cell shrinkage).}

^{The prefix "hypo-" comes from the Greek word hypó, meaning "under," "below," or "insufficient." It describes something is lower than normal, reduced, or deficient.}

^Example:

^{Hypotonic Solution: A solution with a lower solute concentration compared to another, causing water to move into a cell, potentially leading to swelling or bursting.}

^{Hypothermia: A dangerously low body temperature, which can slow down metabolism and lead to organ failure.}

^{Lysis comes from the Greek word lysis, meaning "a loosening" or "dissolution." In biology, lysis refers to the breaking down/eating/chopping of cells or other biological structures.}

^{Example: Cell Lysis:}

• ^{The breaking open of a cell, often caused by osmotic pressure or the action of enzymes or viral infection (bacterial cells breaking open due to viral infection).}

^{Hemolysis: The rupture of red blood cells, typically caused by a hypo-osmotic solution (where water rushes into the cell, causing it to burst).}

^{The prefix "glyco-" comes from the Greek word glykys, meaning "sweet" or "sugar." It commonly involves sugars, carbohydrates, or their derivatives.}

^Example:

^{Glycolysis is the metabolic pathway that breaks down glucose (a type of sugar) to produce energy, generating ATP in the process.}

^{Glycoprotein is a protein molecule that has sugars (carbohydrates) attached to it, playing a key role in cellular communication and immune response.}

^{The term "peptide" comes from the Greek word peptos, meaning "digested." A peptide is a short chain of amino acids linked together by peptide bonds. Peptides are smaller than proteins and serve as hormones, neurotransmitters, or signaling molecules.}

^{Example: Insulin:}

• ^{A peptide hormone that regulates blood sugar levels by helping cells absorb glucose.}