week 1:intro to genes, cells and life
Cellular & Molecular Principles of Life
Module Overview - Lectures
Week-by-week topics covered:
Building blocks of life – molecules, genes & cells (Phil Dash)
Genome organization & DNA replication (Susanna Cogo)
Gene expression control (Susanna Cogo)
Protein synthesis (Susanna Cogo)
Transport and trafficking in cells (Phil Dash)
Cytoskeleton (Phil Dash)
Energy production (Phil Dash & Renee Lee)
Cell death and the cell cycle (Phil Dash)
Cell communication and cell differentiation (Phil Dash)
Connecting cells in tissues (Phil Dash)
Robustness and adaptation (Phil Da
Cells: The Basis of Life
All life is composed of cells:
Single cells:
Prokaryotes (e.g. bacteria)
Eukaryotes (e.g. yeast)
Multicellular organisms: Include invertebrates, vertebrates, plants, and humans.
Cells and Disease
Link between diseases and cellular functions.
Examples of medicines related to cellular functions:
Paracetamol: Analgesic with a composition of 500 mg/tablet.
Penicillin: Antimicrobial agent.
Atenolol: Medication for hypertension (50 mg per tablet).
Salbutamol: Bronchodilator used for asthma.
Herceptin (Trastuzumab): Treatment for certain types of breast cancer.
Are Viruses Alive?
Distinction made between viruses and cells:
Viruses: Lack cellular structure but can hijack host cells for replication.
Example: SARS-CoV-2 virus structure including:
Single-strand RNA
Spike glycoprotein (S)
Proteins involved in viral replication (e.g., NSP3, NSP5, NSP12).
Viruses are categorized based on their ability to replicate within host cells.
no metabolic activity
not made of cells however do need cells in order to survive eg. infecting them to reproduce
Viruses are inert outside of cells
Defining Life
Challenges and complexity associated with defining life:
Common criteria of life:
Ability to grow, reproduce, respond to stimuli, adapt to the environment, and evolve. However there are many exceptions to these cases making it hard to define
Living organisms possess cell boundaries (e.g., membranes) and are metabolically active. Viruses meet some criteria but cycle between being alive and not when in host cells.
evolution from natural selection, separated by environment and metabolically active and anything with cells include this.
Molecular Building Blocks of Life
Four primary types of molecules foundational to life:
Nucleic acids (DNA and RNA)
Proteins(made up of a combo 20 amino acids)
Lipids
Sugars
all molecules are made up of 68 molecules
Each group demonstrates diversity; for instance, proteins consist of 20 different amino acids.
Nucleic Acids: DNA and RNA
Structure: Nucleic acids are polymers with a sugar-phosphate backbone.
DNA Characteristics:
Double-helix structure with two anti-parallel strands connected by specific base pairs (A-T, C-G).
Information is read from the 5' (attached to phosphate) to 3' (attached too OH) direction.
instruction on how to make proteins
RNA Characteristics:
Usually single-stranded, also read from the 5' to 3' direction.
Amino Acids: Building Blocks of Proteins
General Structure: Composed of an amino group (NH2), carboxyl group (COOH), and variable R group (side chain).
Only 20 amino acids are encoded in the genome despite over 500 types.
8 non essential due to body being able to make them and 12 essential from food.
Genetic Code
Codons: A set of three nucleotides corresponding to specific amino acids.
64 possible codons exist for encoding the 20 amino acids, with mRNA's codons read in ribosomes for protein synthesis.
Proteins and Their Functions
Proteins perform critical cellular functions, including:
Catalyzing metabolic reactions
Structural support
Transport roles across membranes
Damage repair and communication.
Proteins can undergo post-translational modifications affecting their function.
Lipids and Their Functions
Role in Cells: Form cellular membranes that act as barriers.
Lipids can be amphiphilic (hydrophobic and hydrophilic), creating bilayers spontaneously in aqueous solutions.
Additional functions include energy storage and facilitating communication between cells.
Sugars' Role in Energy
Sugars, like glucose produced during photosynthesis, serve as major energy sources and structural components (e.g., in complex carbohydrates like cellulose).
combo into carbs
Introduction to Cells
Individual molecular building blocks themselves are non-living; however, their assembly forms living cells.
Lipids spontaneously create membranes to enclose chemical processes catalyzed by enzymes encoded by DNA.
Types and Structures of Cells
Prokaryotic Cells: These cells are generally smaller and simpler, lacking a nucleus (common examples include bacteria and archaea).
Eukaryotic Cells: Larger and more complex, containing membrane-bound organelles such as the nucleus. (include plant cells.) around 1000 times larger than prokaryotic
Surrounded by a lipid membrane, capable of environmental response, and containing DNA.
Common building blocks: proteins, amino acids, carbohydrates, nucleic acids.
Specialized components in complex cells facilitate numerous biological functions.
Compartmentalization in Eukaryotic Cells
Enables efficiency by organizing internal components, aiding in the specialization of different functions.
eg. Dna is made in nuclues and ATP is made in mitochondria instead of all being mixed together (basically organelles)
also more organelles may be found in certain cells that need them eg muscles cells require more mitochondria
Introduction to Genes
A gene is defined as a segment of DNA that gets transcribed into RNA, which includes:
mRNA: translated into proteins.
tRNA and rRNA: involved in protein synthesis.
miRNA: involved in gene regulation.
Most of the human genome (around 98%) consists of non-coding DNA, which plays significant roles despite being termed 'junk DNA'.
non coding regions act as control elements eg. act as reulatory regions
also act as telemores that act as a protective cap for DNA
Gene Structure in Eukaryotes
DNA is read from the 5' to 3' end, with coding regions flanked by regulatory sequences impacting gene transcription.
exons are the bit of a gene that codes for a protein while introns t
Transcription involves RNA polymerase binding to DNA and splicing away introns in the mRNA.
The reason why the introns are there in the first place is for flexibility eg. splicing out some introns will cause exons past it to not be transcribed
Gene Count Across Species
Human gene count: approximately 22,000
Other species' gene counts:
Tomato: ~31,700 genes
Chicken: ~17,000 genes
Fruit fly: ~17,000 genes
Mycoplasma: ~475 genes but can be made with 382 genes in a perfect lab conditions (only require a few essential genes)
this shows how amount of genes doesn’t= complexity of species
only about 9.2% of our genome is essential for cell survival
330 unknown function of genes
Origins of Life
Earth’s geological timeline reflects significant events impacting the development of life:
Aspects includes the emergence of liquid water, the Great Oxidation Event, and mass extinctions shaping evolutionary paths.
Evidence presented from fossil records and geological changes support the transition from simple microbial life to complex organisms over billions of years.
Origins of Eukaryotic Cells: Endosymbiotic Theory
Endosymbiotic Theory suggests that mitochondria and chloroplasts evolved from free-living prokaryotes engulfed by ancestral eukaryotic cells, leading to the symbiotic relationships seen today.
The last eukaryotic common ancestor (LECA) is proposed to possess a nucleus, mitochondria, and other organelles, fundamentally transforming cellular complexity.
Current Discoveries in Cell Origins
2015 discovery of Asgard archaea offered insight into early evolutionary processes, suggesting ancestral links to eukaryotic characteristics.
The complexity of eukaryotic cells derived from these early symbiotic relationships has allowed for diverse multicellular life forms.