Year 1 Biochemistry: Notes Chiranth Badrinath
FoM Lecture 1: Basic Cell Biology Prokaryotes · No nucleus · Bacteria and archaea · Highly diverse · No distinct nucleus · 1-5 um · Visible under electron microscope · E. coli - flagellum, plasma and outer membrane, ribosomes, plasmid DNA · Commensal bacteria- harmless, gut bacteria are beneficial to health Eukaryotes · Contain a nucleus · Fungi, plants and animals · 10-50um · Nucleus and membrane-bound organelles · Diverse in structure and size Type of organelles Mitochondria . Produce most of the ATP by oxidative phosphorylation . Inner membrane: site of OP, cristae are formed via folds in the membrane · Outer membrane: highly permeable due a type of protein known as porins · Mitochondrial matrix is the site of citric acid cycle Smooth Endoplasmic Reticulum (SER) · No ribosomes · Site of lipid synthesis Rough Endoplasmic Reticulum (RER) · Bound by ribosomes · Site of protein synthesis Peroxisome · Contain oxidase enzymes that produce hydrogen peroxide · Hydrogen peroxide is used to detoxify molecules and kill bacteria Lysosomes · Degradation of unwanted/old cellular components · Low pH due to hydrolytic enzymes · Receive waste vesicles from Golgi body · Proteasomes breakdown proteins Ribosomes . Read sections of mRNA from start to stop codon · Translation of mRNA Nucleus . Contains most of the DNA
· DNA is condensed as chromatin · Surrounded by a double membrane, continuous with E.R . Nuclear pores allow RNA and proteins to move into and out of the nucleus . Nucleolus is the site of the ribosome assembly Golgi Body · Protein and lipid modification by addition of sugar groups - glycosylation · Sorting and packaging of proteins and lipids · Vesicular transport: allows exchange of material between organelles Other intracellular structures and components Cytosol and Cytoplasm · Cytosol is the fluid · Cytoplasm is the fluid and organelles Note: many cells are polarised, different ends of the cell may have difference structures and functions Cytoskeleton · Network of protein filaments · 3 types: actin, microtubules, intermediate filaments Actin · Polymer of a double-helix type structure . Can grow and shrink, changing the cell's shape and causing movement · Form cellular extensions, e.g. microvilli · Involved in muscular contraction Microtubules · Consists of alpha and beta subunits · Hollow cylinders of tubulin subunits . Extend from the centrosome · Pull apart chromosomes during division · Make up cilia and flagella · Provide 'tracks' for transports of molecules or proteins using motor proteins · Kinesins- outward transport, Dynesins- inward transport Intermediate filaments · Rope-like filaments found through cytoplasm · Provide mechanical strength for the cell - prevent shearing . Makes up the nuclear lamina, which is a cross-linked mesh beneath the inner membrane FoM Lecture 2: Amino acids and Proteins Amino Acids · 20 different types of amino acid . Can form L or D stereoisomer · Building blocks of proteins