Molecular Biology and Cell Biology Overview
Unit 1 – Molecular Biology
1) Water as a Polar Molecule
Explanation: Water (H₂O) has a bent molecular shape, causing an uneven distribution of charge.
Negative end: Oxygen atom has a partial negative charge because it is more electronegative than hydrogen.
Positive end: The two hydrogen atoms have partial positive charges.
Drawing: A water molecule should depict the bent structure and the polarity (with δ- on oxygen and δ+ on hydrogen).
Cohesion: The tendency of water molecules to stick to each other due to hydrogen bonding.
Adhesion: The tendency of water molecules to stick to other substances.
Causes: These properties arise from the polar nature and hydrogen bonding of water molecules.
Importance: Cohesion helps in water transport in plants; adhesion helps water to rise against gravity (capillarity).
2) Annotate a DNA Molecule
Structure includes:
Double helix structure
Sugar-phosphate backbone
Nitrogenous bases: Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
Base pairing: A pairs with T and C pairs with G.
3) Base Pairing Rules in DNA
Adenine (A) pairs with Thymine (T).
Cytosine (C) pairs with Guanine (G).
These pairs are stabilized through hydrogen bonding.
Importance for replication and transcription in genetic information fidelity.
4) Alpha-Glucose and Condensation Reaction
Drawing: Alpha-glucose is depicted with its hydroxyl group on carbon-1.
Condensation reaction of 2 glucose molecules:
Reaction forms maltose (C₁₂H₂₂O₁₁) and releases H₂O.
Overall equation:
5) Structure and Function of Starch, Cellulose, and Glycogen
Starch:
Structure: Polymers of alpha-glucose; amylose (linear) and amylopectin (branched).
Function: Energy storage in plants.
Cellulose:
Structure: Polymers of beta-glucose; linear chains.
Function: Structural component of plant cell walls.
Glycogen:
Structure: Highly branched polymer of alpha-glucose.
Function: Energy storage in animals.
Monosaccharides: Glucose, Fructose, Galactose.
Disaccharides: Sucrose (glucose + fructose), Lactose (glucose + galactose), Maltose (glucose + glucose).
6) Comparison of Triglycerides and Phospholipids
Triglycerides:
Structure: Glycerol + 3 fatty acids.
Function: Long-term energy storage.
Phospholipids:
Structure: Glycerol + 2 fatty acids + phosphate group.
Function: Major component of cell membranes.
Saturated: No double bonds between carbons; solid at room temperature.
Monounsaturated: One double bond; liquid at room temperature.
Polyunsaturated: Multiple double bonds; liquid at room temperature.
7) Joining of Two Amino Acids
Drawing: Depict an amino acid with an amine group, carboxyl group, and R-chain.
Condensation reaction: Formation of a peptide bond between the carboxyl group of one and the amine group of another.
Equation:
8) Effect of pH and Temperature on Proteins
pH: Affects protein structure by altering ionization of side chains, potentially leading to denaturation if too extreme.
Temperature: High temperatures can disrupt non-covalent interactions and lead to denaturation.
Importance: Proteins must maintain their specific structures to function effectively.
Unit 2 – Cell Stuff
1) Parts of the Cell Theory
All living organisms are composed of cells.
Cells are the basic unit of life.
All cells arise from preexisting cells.
Microscope magnification: 100X; actual cell size is found using: .
If cell appears 1 mm, actual size is .
For hair: 2 mm real thickness; appears 2 mm under 100X magnification (thickness ratio unchanged).
2) Universal Cell Components
Three parts in all cells:
Plasma membrane: Defines cell boundary and regulates transport.
Cytoplasm: Jelly-like substance within the cell where organelles reside.
Genetic material: DNA or RNA that carries the cell's hereditary information.
Importance: Essential for cell function and survival.
3) Life Processes in Unicellular Organisms
Homeostasis: Maintaining stable internal environment.
Example: Regulation of water balance.
Metabolism: Sum of chemical reactions in the cell.
Nutrition: Taking in nutrients for growth and energy.
Movement: Ability to move in response to stimuli.
Excretion: Removal of waste products.
Growth: Increase in cell size and number.
Response to stimuli: Reacting to environmental changes.
Reproduction: Asexual or sexual means of ensuring species survival.
4) Annotate Prokaryotic Cell
Cell Wall: Provides structure and protection (composed of peptidoglycan).
Plasma Membrane: Controls entry/exit of substances.
Cytoplasm: Site for metabolic activities.
Naked DNA in a loop: Genetic material not contained within a nucleus.
70S Ribosomes: Site of protein synthesis, smaller than eukaryotic ribosomes.
5) Fungi, Plant, and Animal Cell Differences
Cell Walls:
Plant cells: Cellulose;
Fungi: Chitin;
Animal: None.
Vacuoles:
Plant: Large central vacuole for storage and support;
Animal: Small and numerous vacuoles.
Chloroplasts: Present in plant cells for photosynthesis, absent in animal cells.
Centrioles: Present in animal cells (involved in cell division), absent in plant cells.
Cilia/Flagella: Present in certain animal and some prokaryotic cells, help in movement.
6) Organelles and Their Benefits
Organelle: Specialized structure within a cell that performs a specific function.
Benefits of separating nucleus from cytoplasm:
Protects DNA.
Regulates gene expression.
Compartmentalization advantages:
Increases efficiency of metabolic processes.
Lysosomes: Contain digestive enzymes, safely separated from cytoplasm.
Phagocytic vacuoles: Store engulfed materials.
7) Stem Cells
STEM Cell: Undifferentiated cells that have the potential to develop into many different cell types.
Bone Marrow: Source of hematopoietic stem cells; important for producing blood cells.
Hair Follicles: Contain stem cells that renew hair growth.
Types of Stem Cells:
Totipotent: Can differentiate into any cell type, including placental cells.
Pluripotent: Can become almost any cell type but not placental cells.
Multipotent: Limited to differentiating into a select cell types.
8) Surface Area to Volume Ratio in Cell Size
Importance: A high surface area to volume ratio allows for efficient nutrient uptake and waste removal.
Larger cells have a lower ratio, which can limit functions.
Unit 3 – Metabolism
1) Metabolism Definition
Metabolism: All chemical reactions occurring within a living organism.
Anabolism: Energy-requiring processes that build larger molecules from smaller ones.
Catabolism: Energy-releasing processes that break down larger molecules into smaller ones.
Enzymes: Biological catalysts that speed up chemical reactions.
Rates: Refers to how quickly metabolic reactions occur; influenced by various factors.
Purpose: Provide energy for cellular processes and form building blocks for cells.
2) Structure and Function of Enzymes
Structure: Proteins with a specific three-dimensional shape.
Active site: Region where substrate binds.
Function: Catalyze biochemical reactions by lowering the activation energy required.
3) Factors Affecting Enzymes
Graph: Enzyme activity plotted against variable (temperature, pH, substrate concentration).
Temperature: Generally increases reaction rates to an optimum, after which denaturation occurs.
pH: Each enzyme has a specific optimal pH; deviations can lead to reduced activity or denaturation.
Substrate Concentration: Increasing substrate concentration will increase reaction rate until enzyme saturation.
4) Cellular Respiration
Definition: The process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water.
Aerobic Respiration: Requires oxygen; produces more ATP.
Anaerobic Respiration: Occurs without oxygen; produces less ATP (e.g., fermentation).
Equation for aerobic respiration:
5) Photosynthesis
Definition: The process by which green plants, algae, and some bacteria convert light energy into chemical energy (glucose).
Equation:
Photosynthetic Pigments: Molecules such as chlorophyll that absorb light energy, mainly in the blue and red wavelengths.
Unit 4 – Central Dogma
1) Transcription Process
Definition: The synthesis of RNA from a DNA template.
Steps:
Initiation: RNA polymerase binds to the promoter region on DNA.
Elongation: RNA polymerase synthesizes RNA strand complementary to the DNA template.
Termination: RNA polymerase reaches a termination signal, completing the RNA strand.
2) Translation Process
Definition: The synthesis of proteins based on the sequence of mRNA.
Steps:
mRNA binds to ribosome.
tRNA brings corresponding amino acids to the ribosome.
Peptide bonds form between amino acids, creating a polypeptide chain.
Process continues until a stop codon is reached.
3) Genetic Code
Explanation: A set of rules that dictates how the sequence of nucleotides in mRNA is translated into a sequence of amino acids.
Deciphering-an mRNA Codon Table:
Given DNA Sequence: CTA GGG CAT GTC CAA
mRNA Sequence: GAU CCC GUA CAG GUU
Protein Sequence: Corresponds to specific amino acids as determined by codon table.
4) Mutation and Its Effects
Definition: A change in the DNA sequence that can affect protein synthesis.
Types of mutations:
Substitutions: One base is replaced by another; effects vary (could be trivial or harmful).
Insertions: Additional bases added; can cause frameshift leading to different amino acids being produced.
Deletions: Removal of bases; similar effects as insertions.
Possible consequences:
Good: Beneficial adaptations.
Bad: Cause diseases.
Neutral: No effect on function.
Unit 5 – Heredity
1) DNA Replication Process
Definition: The process of making identical copies of DNA for cell division.
Role of Helicase: Unwinds the double helix, separating the two strands.
Role of DNA Polymerase: Synthesizes new strands by adding nucleotides complementary to the template strands.
2) Polymerase Chain Reaction and Gel Electrophoresis
Polymerase Chain Reaction (PCR): A technique used to make millions of copies of a specific DNA segment.
Gel Electrophoresis: A method for separating DNA fragments based on size; smaller fragments move faster through a gel matrix.
Applications include genetic testing, forensic analysis, and medical diagnostics.
3) Mitosis and Meiosis Roles
Mitosis: Responsible for producing two genetically identical daughter cells for growth and repair.
Meiosis: Produces gametes (sperm and eggs) for sexual reproduction.
DNA replication is necessary for both to ensure daughter cells have the correct number of chromosomes.
4) Chromosome Movement in Mitosis and Meiosis
Chromosome condensation and movement occurs during prophase of both mitosis and meiosis.
Histones: Proteins that help condense DNA through supercoiling, hence facilitating chromosome formation.
5) Phases of Mitosis
Four Phases:
Prophase: Chromosomes condense and spindle fibers form.
Metaphase: Chromosomes align at the cell equator.
Anaphase: Sister chromatids are pulled apart to opposite poles.
Telophase: Nuclear membranes reform around separated chromosome sets and the cell divides.
6) Need for Meiosis in Sexual Life
Meiosis is essential for producing haploid gametes, ensuring genetic diversity.
Two Rounds of Segregation: Meiosis I (reductional) and Meiosis II (equational).
Down Syndrome: Caused by nondisjunction in meiosis leading to an extra chromosome 21.
7) Genotype and Phenotype Definitions
Genotype: Genetic makeup of an organism (alleles).
Phenotype: Observable traits expressed due to genotype.
Effects:
Dominant alleles: Mask the effect of recessive alleles.
Recessive alleles: Only expressed in homozygous condition.
Incomplete Dominance: Heterozygote exhibits an intermediate phenotype.
Codominance: Both alleles expressed in the phenotype.
8) Blood Type Cross Using IA, IB, and i Alleles
Example crosses between different blood type genotypes (IAIA, IAi, IBIB, IBi, ii) to predict blood type offspring.
Punnett squares utilized for visualizing outcomes.