Biology 1 – Cells, Molecular Biology and Genetics (Biol 1000) PDF

Biology 1 – Cells, Molecular Biology and Genetics (Biol 1000) Professor: Dr. Michael Cardinal-Aucoin Winter 2025  The Eukaryotic Cell Internal Organization of Eukaryotic Cells – Nucleus – Endomembrane system Endoplasmic reticulum...

Biology 1 – Cells, Molecular Biology and Genetics (Biol 1000) Professor: Dr. Michael Cardinal-Aucoin Winter 2025  The Eukaryotic Cell Internal Organization of Eukaryotic Cells – Nucleus – Endomembrane system Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles – Mitochondria – Chloroplasts – Peroxisomes – Cytoskeleton Biol 1000 - Dr. M. Cardinal-Aucoin 2  Eukaryotes Eukaryotic cells have internal membranes that divide the cell into compartments called organelles. Each organelle is specialized for a particular function. – Plant, animal, and protist cells have most of the same organelles. nucleus organelles size Animal cell Plant cell Biol 1000 - Dr. M. Cardinal-Aucoin 3  Internal Organization of Eukaryotic Cells Non-organellar components Plasma membrane Prokaryotes ENDOPLASMIC RETICULUM (ER) Ribosomes have these Rough Smooth ER ER Nuclear envelope NUCLEUS Cytoskeleton too! Nucleolus Chromatin Organelles (membrane-bound compartments) Plasma membrane Nucleus Endomembrane system – Nuclear membrane Ribosomes – ER (rough and smooth) – Golgi body Golgi apparatus – Lysosome – Vacuole Mitochondrion Lysosome Mitochondria Chloroplast Peroxisome Biol 1000 - Dr. M. Cardinal-Aucoin 4  Nucleus Most conspicuous organelle. (hence eukarya: eu = ‘true’ + karya = ‘nut’) Nucleus: stores the DNA Nuclear envelope: defines the boundary of the nucleus. consists of two membranes (inner and outer) each is a lipid bilayer with associated proteins. Nuclear pores: act as gateways allowing molecules to enter and leave the nucleus. Nucleolus: appears as a mass of densely stained granules and fibers. site where rRNA is synthesized. assembly site of large and small ribosomal subunits. Biol 1000 - Dr. M. Cardinal-Aucoin 5  Nucleus In the nucleus, DNA is organized into chromatin, DNA molecule associated with proteins such as histones and others. During cell division the chromatin condenses to form distinct units called chromosomes. Chromatin (DNA + proteins) Condensed Chromosome DNA molecule (during cell division) Histone proteins (DNA is wrapped around them) Biol 1000 - Dr. M. Cardinal-Aucoin 6 If the DNA in a single cell were laid out end to end it would measure about: A. 6.5 inches The average human body contains 16 to 32 billion B. 6.5 feet kilometers of DNA distributed among trillions of cells. Enough C. 6.5 meters to wrap around the circumference of the Earth about D. 6.5 kilometers 500 000 times!!! Biol 1000 - Dr. M. Cardinal-Aucoin 7  Nuclear Pore Controls traffic in and out of nucleus. – Multi-protein complex. – What molecules travel into or out of nucleus? Biol 1000 - Dr. M. Cardinal-Aucoin 8  Ribosomes Present in both prokaryotes and eukaryotes. In eukaryotes, made in the nucleolus. complexes made of rRNA and proteins (forming large and small subunits). sites of proteins synthesis, in which amino acids are assembled into polypeptides. can be free in the cytosol or bound with the endoplasmic reticulum membrane. Biol 1000 - Dr. M. Cardinal-Aucoin 9  Protein Synthesis Proteins synthesized by free ribosomes and those attached to the rough ER have different fates. Out of cell (secretion) ER Secretory vesicles Golgi Plasma membrane apparatus Lysosomes Biol 1000 - Dr. M. Cardinal-Aucoin 10  How do the proteins end up where they should? They possess a signal peptide = signal sequence. protein A protein B signal sequence A signal sequence B signal sequence A signal sequence B directs (sorts) protein directs (sorts) protein A to the organelle A. B to the organelle B. Organelle A Organelle B Nucleus: -Lys-Lys-Lys-Arg-Lys- Peroxisome: - Ser-Lys-Leu- + + + + + Polar + Hydrophobic Biol 1000 - Dr. M. Cardinal-Aucoin 11 Proteins destined for nucleus have a nuclear localization signal Take a protein and attach: 1. Fluorescent tag 2. NLS Intact NLS; protein locates to Altered NLS; protein locates nucleus. to cytoplasm. Biol 1000 - Dr. M. Cardinal-Aucoin 12  Endomembrane System The endomembrane system is composed of internal membranes that communicate through physical connections (they are continuous with each other) or via transfer vesicles (small membrane-bound sacs). Components of the endomembrane system: – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane Biol 1000 - Dr. M. Cardinal-Aucoin 13 Endomembrane System Biol 1000 - Dr. M. Cardinal-Aucoin 14  Endomembrane System Endoplasmic Reticulum Nuclear envelope continuous with the nuclear envelope. accounts for more than half of the total membrane in many eukaryotic cells. network of membranous tubules and cisternae. two distinct regions of the E.R. that differ in structure and function: Rough E.R. Smooth E.R. Biol 1000 - Dr. M. Cardinal-Aucoin 15  Endomembrane System Endoplasmic Reticulum Rough E.R.: ribosomes flattened sacs called cisternae. studded with ribosomes on the surface of the membrane. synthesis of proteins that are to be cisternae secreted. synthesis of membrane components. Smooth E.R.: network of tubules. outer surface lacks ribosomes (smooth). functions in diverse metabolic processes, vary with cell type. tubules E.g. synthesis of lipids, metabolism of carbohydrates, detoxification of drugs/poisons, storage of calcium ions. Biol 1000 - Dr. M. Cardinal-Aucoin 16  Endomembrane System Golgi Apparatus looks like a series of flattened membrane sacs, called cisternae, surrounded by many small vesicles. not physically continuous with the E.R. next stop for most vesicles budding from the E.R. three primary roles: 1. further modifies the lipids and proteins produced by the E.R. 2. synthesis of carbohydrates 3. acts as sorting station Lysosome/vacuole exocytosis cell membrane Biol 1000 - Dr. M. Cardinal-Aucoin 17  Endomembrane System Example: Insulin synthesis and secretion Insulin is a peptide hormone, produced by pancreas beta cells. Insulin regulates glucose levels in the body, by signaling cells to absorb glucose from the blood. Diabetes mellitus is a result of defective insulin production or function. Biol 1000 - Dr. M. Cardinal-Aucoin 18  Endomembrane System Example: Insulin synthesis and secretion Insulin is translated as preproinsulin as a single oligopeptide. Proinsulin is formed by cleaving the signal peptide. Insulin is formed by cleaving off the C peptide from proinsulin. Biol 1000 - Dr. M. Cardinal-Aucoin 19  Endomembrane System signal peptide (sequence of approx. 20 amino acids) is bound by signal- recognition particle (SRP) which directs ribosome with mRNA to the ER membrane where it binds with the SRP receptor. translation continues and peptide crosses through channel into lumen (secreted or internal proteins) or inserts into membrane (membrane proteins). Biol 1000 - Dr. M. Cardinal-Aucoin 20  Endomembrane System Example: Insulin synthesis and secretion “tags” proteins for sorting to their final destinations. protein modification (glycoprotein, lipoprotein) Proinsulin -> insulin Biol 1000 - Dr. M. Cardinal-Aucoin 21  Endomembrane System Example: Insulin synthesis and secretion Insulins to be secreted from the cell are transported to the membrane in secretory vesicles which release their contents to the exterior by exocytosis. Biol 1000 - Dr. M. Cardinal-Aucoin 22  Endomembrane System Lysosomes specialized vesicles derived from the Golgi body. full of hydrolytic enzymes. degrade damaged or unneeded macromolecules (e.g., proteins, nucleic acids, lipids, complex carbs). Break down polymers by hydrolysis! proton pumps in lysosome membrane keep the lysosomal environment at an acidic pH of around 5 (optimal pH for the hydrolytic enzymes to function). Note: lysosomes only in animal cells. Plants have vacuoles that serve similar purpose. Biol 1000 - Dr. M. Cardinal-Aucoin 23  Endomembrane System Lysosome 1. Can digest material ingested by 2. Damaged/defective organelles cell through phagocytosis. are broken down by autophagy. Biol 1000 - Dr. M. Cardinal-Aucoin 24 Biol 1000 - Dr. M. Cardinal-Aucoin 25  Endomembrane System Vacuoles large vesicles derived from the endoplasmic reticulum and Golgi apparatus. perform a variety of functions: food vacuole stores nutrients. digestive vacuole acts like lysosome in plants. contractile vacuole (in many protists) expels water. central vacuole (in many plant cells) regulates (turgor) pressure in cell. Biol 1000 - Dr. M. Cardinal-Aucoin 26  The Endomembrane System Nucleus Rough ER Smooth ER cis Golgi lysosome Plasma trans Golgi membrane Biol 1000 - Dr. M. Cardinal-Aucoin 27 Biol 1000 - Dr. M. Cardinal-Aucoin 28 Mitochondria Sites of cellular respiration ➔ metabolic process that uses oxygen to generate ATP by extracting energy from sugars, fats and other fuels. Some cells have a a single large mitochondrion, more often a cell has hundreds to thousands of mitochondria (dependent on cell’s function). Q: which cells should have more mitochondria? Biol 1000 - Dr. M. Cardinal-Aucoin 29 Mitochondria Enclosed by two membranes; outer membrane is smooth, inner membrane is convoluted, with infoldings called cristae. Inner membrane divides mitochondrion into: Inter membrane space: narrow region between inner and outer membrane. Mitochondrial matrix: inner-most space; contains enzymes, mitochondrial DNA, and ribosomes. Biol 1000 - Dr. M. Cardinal-Aucoin 30  Chloroplasts Chloroplasts capture the energy of sunlight to synthesize sugars; a process known as photosynthesis. Chloroplasts are surrounded by a double membrane. Have internal membrane-bound compartments called thylakoid arranged in stacks called grana. Thylakoid membrane houses pigments that capture energy from light. Inner-most space called the stroma contains enzymes, chloroplast DNA, and ribosomes Biol 1000 - Dr. M. Cardinal-Aucoin 31  Origins of Mitochondria and Chloroplasts Theory of Endosymbiosis: Mitochondria developed from ingested aerobic bacteria aerobic (proteobacteria). bacterium Archaeal cell Chloroplasts developed from (host) ingested cyanobacteria. The bacteria survived, both Bacterial cell is protected and benefited, forming a symbiotic gets nutrients; relationship; eventually host and host gets energy. bacterium became inseparable. Biol 1000 - Dr. M. Cardinal-Aucoin 32 Origins of Mitochondria and Chloroplasts Endosymbiogenesis Theory To plants To animals Biol 1000 - Dr. M. Cardinal-Aucoin 33  Origins of Mitochondria and Chloroplasts Evidence: Similar size to bacteria. Enveloped by a double membrane. – Ancient phagocytosis event. Contain free ribosomes (similar to bacterial type) and circular DNA molecules. Grow and reproduce somewhat independently of host cell. – By binary fission similar to bacteria. Biol 1000 - Dr. M. Cardinal-Aucoin 34  Peroxisomes Peroxisomes are specialized metabolic compartments bounded by a single membrane. Peroxisomes perform reactions with many different functions (i.e. breakdown of fatty acids, reduction of reactive oxygen species). – As a result, peroxisomes produce hydrogen peroxide (H2O2) which they then convert to H2O + O2 using the enzyme catalase. How peroxisomes are related to other organelles is still unknown. 1 m Chloroplast Peroxisome Mitochondrion Mitochondria Peroxisomes Biol 1000 - Dr. M. Cardinal-Aucoin 35 Biol 1000 - Dr. M. Cardinal-Aucoin 36 Biol 1000 - Dr. M. Cardinal-Aucoin 37 Biol 1000 - Dr. M. Cardinal-Aucoin 38