BO101 Cell Biology Lecture 2 2024 PDF

Tour of the cell 2 BO101 - Cell Biology - Lecture 2 Dr Andrew Flaus, Biochemistry Tour of the Cell - Stop 2: Endomembrane system Protein traf cking and metabolic functions fi Endomembrane system as a factory ๏ Endoplasmic reticulum ‣ Production biosynthesis ๏ Golgi apparatus...

Tour of the cell 2 BO101 - Cell Biology - Lecture 2 Dr Andrew Flaus, Biochemistry Tour of the Cell - Stop 2: Endomembrane system Protein traf cking and metabolic functions fi Endomembrane system as a factory ๏ Endoplasmic reticulum ‣ Production biosynthesis ๏ Golgi apparatus ‣ Shipping and receiving ๏ Lysosomes ‣ Waste recycling Campbell g 7.15 fi Endoplasmic reticulum ๏ Structure ‣ ER = ‘little net within cytoplasm’ Large, convoluted membrane Lumen = ER interior ‣ Specialised environments for controlling processes ๏ Two parts ‣ Rough ER Ribosome-coated surface ‣ Smooth ER No ribosomes Campbell g 7.11 fi Rough ER ๏ Ribosomes on membrane ‣ Translation of mRNA to protein ‣ Proteins for secretion Often glycosylated ๏ Processing at membrane 1. Leader signal polypeptides targets ribosome to ER 2. Processive synthesis injects protein into lumen 3. Processing of protein Folding, sorting Images from Beckers World of the Cell ch 12 (top) and Mol Biology of the Cell ch 12 (bottom) Golgi apparatus structure ๏ Cisternae ‣ Pancake like chambers/sacs ‣ Direction of movement in Golgi ๏ Cis and trans faces ‣ Cis receiving, Trans shipping ๏ Vesicles ‣ Buds travel and link cisternae ๏ Functions ‣ Add sugar chains to proteins ‣ Export to lysosomes Campbell g 7.12 fi Lysosomes ๏ Structure ‣ Sac of hydrolytic enzymes Ready to degrade biomolecules ‣ Bud off from Golgi apparatus ๏ Function ‣ Related to bulk transport ‣ Merge with: a. Vesicles from outer membrane containing ‘food’ = phagocytosis b. Vacuoles of damaged materials from internal regions = autophagy Campbell g 7.13 fi Tour of the Cell - Stop 3: Energy organelles Transforming between energy forms Transforming between energy forms ๏ Mitochondria ‣ Chemical energy conversion ‣ Multiple per cell ๏ Chloroplasts ‣ Light to chemical energy ๏ (Peroxisomes) ‣ Chemical oxidations Contain toxic H2O2 Protected use of toxic processes ‣ Alcohol detoxi cation Campbell g 7.8 fi fi Endosymbiont hypothesis ๏ Two endosymbiotic events ‣ First for all eukaryotes Common ancestor takes up non-photosynthetic prokaryote ‣ Second later for all plant cells Plant ancestor takes up further photosynthetic prokaryote ๏ Evidence 1. Double membranes 2. Own genomes and ribosomes 3. Independent growth, replication Campbell g 7.16 fi Mitochondria ๏ Two membranes ‣ Outer is smooth ‣ Inner is in-folded = cristae Large surface area ๏ Two spaces ‣ Intermembrane space ‣ Matrix Enzymatic processes to produce ATP as energy of respiration Mitochondrial DNA, ribosomes Campbell gs 7.17, 10.15 fi Chloroplasts ๏ Two membranes ‣ Inner and outer ๏ Thylakoids ‣ In interior cytosol ‣ Interconnected sacs Granum = stacked thylakoids ‣ Light harvesting complexes Contains chlorophyll ๏ Genetic information ‣ DNA and ribosomes in stroma Campbell g 7.18, 11.8 fi Tour of the Cell - Stop 4: Cytoskeleton Structuring and moving the cell  3 types of cytoskeleton laments ๏ Functions ‣ Provide support for cell shape and structure ‣ Enable motility of components in cells Type lament polymer subunit 1 microtubules tubulin 2 actin laments actin 3 intermediate laments keratins Campbell g 7.29; adapted from table 7.1 fi fi fi fi fi Microtubules ๏ Monomer = tubulin ๏ Functions ‣ Maintaining cell shape ‣ Cell motility by cilia and agella ‣ Chromosome movement ‣ Organelle movement Campbell gs 7.20, 7.21 fi fl Actin micro laments ๏ Monomer = actin ๏ Functions ‣ Maintaining cell shape ‣ Muscle contraction ‣ Cell motility Campbell table 7.1; g 7.26a fi fi Tour of the Cell - Stop 5: Extracellular connections Interactions between cells Extracellular matrix of animal cells ๏ Structure ‣ Collagen 40% of human protein mass ‣ Proteoglycan Multiple sugars on protein scaffold ‣ Fibronectin Glycoprotein anchored to integrins ๏ Function ‣ Meshwork for rigidity Campbell g 7.28 fi  Junctions of animal cells ๏ Tight junctions ‣ Close membrane association ‣ No ow between layers ๏ Desmosomes ‣ Bond cells together via intermediate laments Muscle tearing = desmosome break ๏ Gap junctions ‣ Channels between cytoplasms Inter-cell exchange, communication Campbell g 7.30 fl fi fi Summary of tour of cell 1. Nucleus ‣ Chromosomes as DNA packaging 2. Endomembrane system ‣ Endoplasmic reticulum ‣ Golgi 3. Energy organelles ‣ Mitochondria ‣ Chloroplasts 4. Cytoskeleton 5. Extracellular connections Learning outcomes for lecture On successful completion of this lecture, you will be able to: ‣ Compare the roles played by the different parts of the endomembrane system in traf cking and metabolism ‣ Detail the structure and signi cance of mitochondria, chloroplast and peroxisome compartments in energy generation ‣ Give examples of how the cytoskeletal network organises structures and biochemical activities in eukaryotic cells ‣ Outline how extracellular structures connect and coordinate adjacent eukaryotic cells fi fi