👩‍🔬Intro to Biotechnology Unit 2 – Cellular and Molecular Biology Basics

Key Concepts and Terminology

• Cells are the basic unit of life, performing essential functions to maintain an organism's survival
• Prokaryotic cells lack a nucleus and other membrane-bound organelles, while eukaryotic cells contain a nucleus and specialized organelles
• DNA (deoxyribonucleic acid) stores genetic information, while RNA (ribonucleic acid) plays a role in gene expression and protein synthesis
• Proteins are essential macromolecules that perform various functions within cells, including structural support, enzymatic reactions, and cell signaling
  • Amino acids serve as the building blocks of proteins, linked together through peptide bonds
• Cellular respiration is the process by which cells break down glucose to produce ATP (adenosine triphosphate), the primary energy currency of the cell
• Cell division allows for growth, repair, and reproduction in organisms
  • Mitosis results in two genetically identical daughter cells, while meiosis produces four genetically diverse haploid cells (gametes)
• Gene expression is the process by which genetic information is used to synthesize functional gene products, such as proteins

Cell Structure and Function

• The plasma membrane is a selectively permeable barrier that regulates the movement of substances in and out of the cell
  • Composed of a phospholipid bilayer with embedded proteins, the plasma membrane maintains cellular homeostasis
• The nucleus contains the cell's genetic material (DNA) and is the site of DNA replication and transcription
  • The nuclear envelope, consisting of a double membrane with nuclear pores, separates the nucleus from the cytoplasm
• Ribosomes are the sites of protein synthesis, translating mRNA (messenger RNA) into polypeptide chains
  • Ribosomes can be found freely in the cytoplasm or attached to the rough endoplasmic reticulum (ER)
• The endoplasmic reticulum is a network of membranous channels involved in protein and lipid synthesis, as well as transport within the cell
  • Smooth ER lacks ribosomes and plays a role in lipid synthesis and detoxification, while rough ER is studded with ribosomes and participates in protein synthesis and modification
• Mitochondria are the powerhouses of the cell, generating ATP through the process of cellular respiration
  • Mitochondria contain their own DNA and ribosomes, suggesting an endosymbiotic origin
• The Golgi apparatus is responsible for modifying, packaging, and sorting proteins and lipids for transport to their final destinations
• Lysosomes are membrane-bound organelles containing digestive enzymes that break down cellular waste, foreign particles, and damaged organelles

DNA, RNA, and Protein Synthesis

• DNA is a double-stranded helix composed of nucleotides, each containing a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases (adenine, thymine, guanine, or cytosine)
  • Complementary base pairing (A-T and G-C) and hydrogen bonds stabilize the DNA double helix
• DNA replication is the process by which a cell duplicates its genetic material before cell division
  • DNA replication is semiconservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand
• Transcription is the process of creating an RNA copy of a gene, which occurs in the nucleus
  • RNA polymerase catalyzes the synthesis of RNA from a DNA template, producing mRNA, tRNA (transfer RNA), or rRNA (ribosomal RNA)
• Translation is the process of synthesizing a protein from an mRNA template, which occurs at the ribosomes
  • tRNAs carry specific amino acids to the ribosome, where they are linked together based on the codons in the mRNA
• The genetic code is the set of rules that determines which amino acid corresponds to each three-base codon in mRNA
  • The genetic code is nearly universal across all living organisms, with a few exceptions (mitochondrial DNA)

Cell Division and Reproduction

• The cell cycle is the series of events that take place in a cell, leading to its division and duplication
  • The cell cycle consists of interphase (G1, S, and G2 phases) and the mitotic phase (mitosis and cytokinesis)
• During interphase, the cell grows, performs its normal functions, and prepares for cell division
  • The S phase is when DNA replication occurs, doubling the cell's genetic material
• Mitosis is the process of nuclear division, resulting in two genetically identical daughter nuclei
  • Mitosis consists of four stages: prophase, metaphase, anaphase, and telophase
• Cytokinesis is the division of the cytoplasm, which occurs after mitosis and results in two separate daughter cells
  • In animal cells, cytokinesis involves the formation of a cleavage furrow, while in plant cells, a cell plate forms between the daughter cells
• Meiosis is a specialized form of cell division that produces four haploid gametes, each with half the genetic material of the parent cell
  • Meiosis involves two rounds of cell division (meiosis I and II) and includes crossing over, which increases genetic diversity
• Errors in cell division can lead to genetic disorders or cancer
  • For example, Down syndrome is caused by an extra copy of chromosome 21 (trisomy 21), which occurs due to nondisjunction during meiosis

Cellular Energy and Metabolism

• Metabolism refers to the sum of all chemical reactions that occur within a cell, including catabolic (breaking down molecules) and anabolic (building up molecules) processes
• ATP is the primary energy currency of the cell, used to power various cellular processes
  • ATP consists of an adenosine molecule bonded to three phosphate groups, and energy is released when these bonds are broken
• Cellular respiration is the process by which cells break down glucose to produce ATP
  • Cellular respiration occurs in three stages: glycolysis, the Krebs cycle, and the electron transport chain
• Glycolysis is the first stage of cellular respiration, taking place in the cytoplasm and breaking down glucose into two pyruvate molecules
  • Glycolysis produces a net gain of 2 ATP and 2 NADH (reduced nicotinamide adenine dinucleotide) molecules
• The Krebs cycle, also known as the citric acid cycle, occurs in the mitochondrial matrix and generates high-energy molecules (NADH and FADH2) from the oxidation of acetyl-CoA
• The electron transport chain is the final stage of cellular respiration, located in the inner mitochondrial membrane
  • The electron transport chain uses the high-energy molecules from the Krebs cycle to create a proton gradient, which drives the synthesis of ATP through chemiosmosis
• Fermentation is an anaerobic process that allows cells to generate ATP in the absence of oxygen
  • Lactic acid fermentation occurs in animal cells and some bacteria, while alcoholic fermentation occurs in yeast and some plant cells

Gene Regulation and Expression

• Gene regulation is the process by which cells control the expression of their genes, determining which genes are transcribed and translated into proteins
• Prokaryotic gene regulation often involves operons, which are clusters of genes under the control of a single promoter
  • The lac operon in E. coli is a well-studied example of gene regulation, where the presence of lactose induces the expression of genes necessary for its metabolism
• Eukaryotic gene regulation is more complex, involving transcriptional, post-transcriptional, and post-translational modifications
  • Transcriptional regulation involves the binding of transcription factors to regulatory sequences (enhancers and silencers) to control the initiation of transcription
• Epigenetic modifications, such as DNA methylation and histone modifications, can alter gene expression without changing the underlying DNA sequence
  • These modifications can be inherited across cell divisions and even generations, contributing to cellular differentiation and development
• Alternative splicing is a post-transcriptional modification that allows a single gene to produce multiple protein isoforms
  • Alternative splicing involves the selective inclusion or exclusion of exons during the processing of pre-mRNA
• Post-translational modifications, such as phosphorylation, glycosylation, and ubiquitination, can alter the function, stability, or localization of proteins
  • These modifications allow for rapid changes in protein activity in response to cellular signals or environmental stimuli

Lab Techniques and Applications

• Polymerase Chain Reaction (PCR) is a technique used to amplify specific DNA sequences, generating millions of copies from a small initial sample
  • PCR involves three main steps: denaturation, annealing, and extension, which are repeated for multiple cycles
• Gel electrophoresis is a method used to separate DNA, RNA, or proteins based on their size and charge
  • Agarose gel electrophoresis is commonly used for DNA and RNA, while polyacrylamide gel electrophoresis (PAGE) is used for proteins
• DNA sequencing determines the precise order of nucleotides in a DNA molecule
  • Sanger sequencing, also known as the chain termination method, was the first widely used sequencing technique
  • Next-generation sequencing (NGS) technologies, such as Illumina and Nanopore sequencing, have revolutionized the field by enabling high-throughput and cost-effective sequencing
• CRISPR-Cas9 is a powerful gene-editing tool derived from the bacterial adaptive immune system
  • CRISPR-Cas9 allows for precise editing of DNA sequences, with applications in basic research, agriculture, and medicine
• Recombinant DNA technology involves the insertion of foreign DNA into a host organism, enabling the production of desired proteins or the study of gene function
  • Plasmids and viral vectors are commonly used to introduce recombinant DNA into host cells
• Bioinformatics is the application of computational tools to analyze and interpret biological data
  • Bioinformatics plays a crucial role in managing and analyzing the vast amounts of data generated by modern biotechnology techniques, such as genome sequencing and proteomics

Biotech Connections and Real-World Examples

• The Human Genome Project, completed in 2003, aimed to sequence the entire human genome, providing valuable insights into human biology and disease
  • The project has led to the identification of genes associated with various genetic disorders and the development of targeted therapies
• Genetically modified organisms (GMOs) are organisms whose genetic material has been altered using genetic engineering techniques
  • GMO crops, such as Bt corn and herbicide-resistant soybeans, have been developed to improve yield, nutritional content, and pest resistance
• Biopharmaceuticals are drugs produced using living organisms, such as bacteria, yeast, or mammalian cells
  • Examples include insulin for diabetes treatment, erythropoietin for anemia, and monoclonal antibodies for cancer therapy
• Personalized medicine aims to tailor medical treatments to an individual's genetic profile, lifestyle, and environment
  • Pharmacogenomics studies how a person's genetic makeup influences their response to drugs, enabling the development of targeted therapies with fewer side effects
• Forensic DNA analysis uses DNA profiling techniques to identify individuals based on their unique genetic fingerprint
  • DNA evidence has revolutionized criminal investigations and has been used to exonerate wrongfully convicted individuals
• Synthetic biology is an emerging field that combines principles from biology, engineering, and computer science to design and construct novel biological systems
  • Applications of synthetic biology include the production of biofuels, the development of biosensors, and the creation of artificial organs
• Stem cell research explores the potential of using stem cells, which have the ability to differentiate into various cell types, for regenerative medicine and disease modeling
  • Induced pluripotent stem cells (iPSCs) are adult cells that have been reprogrammed to a pluripotent state, offering a promising alternative to embryonic stem cells