Cell Bio Final Notes.pdf

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Biological Sciences
Rene Harrison

CELL BIOLOGY FINAL EXAM NOTES Lectures 7 & 8: Mitochondria vs. Chloroplast Mitochondria Chloroplast Arose from... phagocytosis of aerobic prokaryote phagocytosis of photosynthetic bacteria - can divide in the cell: “mitochondrial fission”, powerhouse of the - can divide by fission cell Function - site of aerobic respiration: utilizing oxygen to extract energy - site of photosynthesis: utilizes energy to convert carbon dioxide and water from macromolecules (primarily glucose) and converting it to into glucose ATP (ATP production) - we use 2 x 10 26molecules of ATP/day - Energy is released when ATP is hydrolyzed to ADP Present in muscle cells, liver cells, fat cells, plant cells & sperm plants, eukaryotic algae, some protists and several prokaryotes Structure - Outer membrane (Intermembrane space in between): - Outer envelope membrane (Intermembrane space in between) - 50% protein: lipid ratio - Contain porin proteins: large channels - contain porin (bacteria protein) proteins: - Allow very large molecules through large channels - Inner envelope membrane - Allow very large molecules through - Highly impermeable: requires transporters - Inner membrane (cristae): has high surface area for more ATP - Thylakoid Sacs (Internal Membrane System) made - Arranged into grana (stacks of thylakoids) - Cristae: many thin folds to increase - membrane has 75:25 protein:lipid ratio surface area - Huge amound of surface area: increase - 75% protein: 25 lipid ration (lipid = photosynthesis cardiolipin [also found in bacterial - Have lumen inside membranes]) - Stroma Lamellae - Very impermeable: requires channels & - Flattened membrane structures that connect pumps for movement across thylakoids from different grana - 100 different proteins: including proteins - Stroma in ETC - contains DNA and ribosomes, tRNA - Matrix: Krebʼs cycle happens in here - chloroplast DNA encodes for 100 genes - gel-like from high protein concentration - However, 90% of chloroplast proteins are - contains DNA and ribosomes, tRNA encoded by nuclear DNA - mitochondrial DNA encodes 37 genes - Therefore many chloroplast proteins must be - Mitochondrial function requires 3,000 imported (targeted) to chloroplasts proteins, therefore mitochondria function - Protein translocons are also involved in import requires nuclear gene products, and of proteins into chloroplasts these proteins must imported (targeted) to mitochondria - Protein translocons are also involved in import of proteins into mitochondrias Mitochondria Chloroplast Posttranslational - Mitochondria proteins are completely translated on free - Chloroplast proteins are translated on free ribosome in cytosol uptake of proteins ribosomes in cytosol - What is the targeting sequence of chloroplast proteins? - What is the targeting sequence of mitochondrial protein? - Chloroplast “transit peptide” 1) Mitochondrial “presequence” - at amino terminus of chloroplast protein - at amino terminus of “preprotein” - Has a stroma-targeting domain (stroma proteins) - several (+) charged amino acids for - and can also have a thylakoid transfer domain (for soluble matrix proteins thylakoid proteins) 2) Internal sequence & stop transfer - To enter chloroplast: sequence for integral IMM proteins - Protein is first unfolded by HSP 70 (chaperone protein) - To enter mitochondria: - Transit peptide binds to its receptor - Protein is first unfolded by HSP 70 - located next to a translocon on outer chloroplast (chaperone protein) membrane - Protein binds to its receptor on OMM - TOC (translocon of outer chloroplast membrane) - located next to a translocon on OMM - HSP 70 proteins in intermembrane space keep protein - TOM (translocon of outer membrane) unfolded - IMM integral proteins: - Moves though TIC (translocon of inner membrane of - directed to TIM22 complex of IMM chloroplast) complex - TIM (translocon of inner membrane) - If destined for stroma: - stop transfer seuqnce embeds protein in - HSP 60 refolds protein and stroma-targeting domain is the IMM includes all the protein of the cleaved by a protease) ETC and the ATP synthase - If destined for thylakoid lumen: - Matrix Proteins: - Stroma-targeting domain is cleaved to reveal thylakoid - directed to TIM23 complex of IMM transfer domain - preprotein moves through TIM because - Protein is transported into lume: bacterial translocan- of membrane potential differences across type machinery IMM - Proteins on the Thylakoid Membrane: - associates with mt-HSP 70 which also - encoded by chloroplast genes helps to pull it through - ribosomes assemble on thylakoid membrane (like - Once in matrix: RER) and stop transfer sequences retain proteins in - associates with HSP 60 (folds protein) the membrane - mitochondrial processing peptidase (MPP); a protease, then cuts off presequence to create mature protein (includes all the enzymes of the Krebʼs/citric acid cycle) Mitochondria Chloroplast How does... Mitochondria make ATP: Chloroplast make glucose: - Total Result of Aerobic Respiration: - Total result of photosynthesis: C6H 12+ 6O = 62O + 6H O2+ 38 2TP 6 CO +26H O 2 light + ATP = 6O + C 2 O 6 12 6 - Chemical reactions are performed enzymes (proteins): act on - Start with Light energy substrates (targets) to produce a chemical change in the 1) Light-Dependent Reaction (in thylakoid membranes) substance - Light energy is absorbed and converted to chemical energy
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