Lecture 1 - Building Blocks of Life PDF
Document Details
Uploaded by LuxuriousBlackberryBush
University of Reading
Tags
Summary
These lecture notes cover the fundamental building blocks of life, including molecules, genes, and cells. The document details the importance of cells and their components, describing their functions and the processes involved in cell specialization. It also touches on the origins of eukaryotic cells and the endosymbiotic theory.
Full Transcript
Building blocks of life (1) Wednesday 2 October 2024 13:02 Building blocks of life - molecules, genes, cells (1) ASSESSMENTS : 40% scientific report (practical class). 60% exam. 50 mcq on everything in lectures and practicals. 5 possible answers. Cells are the fundamental units of life A...
Building blocks of life (1) Wednesday 2 October 2024 13:02 Building blocks of life - molecules, genes, cells (1) ASSESSMENTS : 40% scientific report (practical class). 60% exam. 50 mcq on everything in lectures and practicals. 5 possible answers. Cells are the fundamental units of life All life has a universal genetic code Recommended wider reading -what is life? Paul Nurse. Understanding life in five steps Life is defined by Evolution through natural selections , eg viruses Separated from their environment by a boundary like a membrane, eg viruses Metabolically active and use their metabolism to maintain themselves, grow and reproduce. Eg viruses only when in cells Anything made of cells meets this criteria All life on earth is made up of same fundamental molecular building blocks:. Nucleic acids. Proteins. Lipids. Sugars There are 68 molecules that contribute to the four major groups ^ Nucleic acids encode info in cells. DNA and RNA are polymers that consist of a sugar phosphate backbone, info is encoded in the sequence of bases. Joined by base pairing DNA - double helix with two anti parallel strands Info always read from 5’ to 3’ Amino acids make proteins. Have carboxyl group and amino group - diff R chains Only 20 amino acids encoded in the genome and used to make proteins The genetic code links the DNA sequence to protein structure. Set of 3 nucleotides makes specific amino acid - CODON. 4 nucleotides to choose from therefore 64 possible codons to encode info for the 20 amino acids Codons on a strand of mRNA are read in ribosomes, with tRNA bringing the correct amino acids to the growing polypeptide chain. Proteins carry out most cell fuctionms. Speed up metabolic reactions, act as transporters, provide structural support and repair. Function related to structure Can be modified post translation that can changee their shape and regulate their function. Lipids key function is to form membranes, which act like a barrier b between cell and external environment and a barrier between organelles and rest of cell. Usually hydrophobic, but can be amphiphilic. Other functions include energy storage and cell communication. Sugars are major energy source and structural support (as complex carbohydrates). Lipids can spontaneously form into membranes that enclose chemical reactions carried out by enzymes that are encoded by DNA. CELLS Prokaryotes (bacteria, arches) and eukaryotes (larger more complex, many membrane-bound organelles) Common features:. All cells can sense and respond to their environment. All cells contain DNA. All surrounded by a membrane made of lipids. Common building blocks Viruses are smaller than prokaryotes. Too small to function on their own and need larger cells in order to replicate. Prokaryote cell - 1 micrometer^3 Eukaryote cell - 1000 micrometer^3 Diffusion of molecules in larger cells takes longer, limiting reaction speed. Compartmentalisation allows cells to work more efficiently. ^ of eukaryote cells overcomes the problems associated with large volumes. Also creates new opportunity. Cells can change no. and type of organelles they produce in order to allow the cell to take on diff functions so specialise. Diff combinations of specialised cells creates the diversity of multicellular life on the planet. Gene = sequence of DNA which is transcribed into RNA. RNA types: mRNA - translated into protein tRNA and rRNA - protein synthesis miRNA - regulate gene expression Non coding regions (makes up 98% of our genome) include introns, regulatory regions, retroviral sequences, telomeres etc. EUKARYOTE GENE STRUCTURES DNA strands have a direction(5’-3’) Coding region in middle has regulatory regions at either end - guides molecules such as transcription factors and RNA polymerase to the start of the gene. During transcription, RNA polymerases are guided to start of gene following transcription factor binding to regulatory regions. Then transcribes the gene, leaving outnregulatory regions, until a stop codon appears. Introns are spliced out of the RNA sequence =mRNA. Leaves nucleus. 9.2% of our genome is essential for cell survival. ORIGINS OF LIFE (cells) Last universal common ancestor - LUCA roughly 4300 million years ago Smallest and simplest prokaryote cell is the Mycoplasma bacteria. Contains nearly 500 genes Origins of eukaryotic cells Thought that both mitochondria and chloroplasts were originally free living and were phagocytosed by a cell and kept rather than hydrolysed. This symbiosis b between two cells eventually evolved to cells today - this is the endosymbiotic theory. We don’t know which organnelles arose first. Last eukaryote common ancestor would have contained nucleus, mitochondria, Golgi, lysosomes, cytoskeleton. Eukaryotes emerged from the archaea. Asgard archaea were first discovered in 2015, Lokiarchaeota was first Asgard phylum identified - Norway.
