BIOL1110 M2 Lecture 2 PDF

BIOL1110 From Molecules to Cells (Lecture 2) Cell and Cell Structure II Dr. Gary Ying Wai Chan Office: Rm4N11 KBSB Email: [email protected] Smooth ER (Endoplasmic reticulum) Structure: tubular appearance and its outer membrane surface appears smooth Function:...

BIOL1110 From Molecules to Cells (Lecture 2) Cell and Cell Structure II Dr. Gary Ying Wai Chan Office: Rm4N11 KBSB Email: [email protected] Smooth ER (Endoplasmic reticulum) Structure: tubular appearance and its outer membrane surface appears smooth Function: 1) It synthesizes lipids, phospholipids, and steroids. 2) It also carries out metabolism of carbohydrates, e.g., gluconeogenesis. 3) In muscle cells, it regulates calcium ion concentration. 4) Break down toxic chemicals and drugs (detoxification) (ii) Rough ER Structure: Similar to smooth ER but with its outer surface studded with ribosomes Function: For synthesis, modification and trafficking of proteins 1) Nascent polypeptides are inserted into the lumen of RER. 2) Proteins are then modified by enzymes that add lipid or carbohydrate onto the protein. 3) Special molecular mechanisms will catalyze the formation of proper conformational structure of protein. 4) Proteins are transported to various compartments, plasma membrane or outside of the cell. (iii) Golgi Structure: stacks of flattened membranous sacs called cisternae - Each Golgi stack has the cis (entry) and trans (exit) face Function: modifying, sorting, and packaging of proteins 1)Modification such as proteolytic cleavage, glycosylation, phosphorylation and sulfation (a sulfate group is added to a tyrosine residue of a protein molecule). 2)Trafficking to different compartments of the cell, default pathway to the cell membrane. 3)Formation of lysosomes Protein Trafficking Via Golgi NDSU Virtual Cell Animations Project animation 'Protein https://www.youtube.com/watch?v=rvfvRgk Trafficking' 0MfA Protein transport within the cells Constitutive secretion https://www.youtube.com/watch?v=MrHULUxAsGg&index=14&list=UUcSThfV7yiW9I5hXBnEk9Z g Regulated secretion https://www.youtube.com/watch?v=guqCEa7Y4RA (iv) Lysosome Structure: Small sac storing digestive enzymes that are active under acidic condition (pH 5) Lysosome membrane confines its enzymes and their actions within lysosome. The Golgi apparatus adds a mannose- 6-phosphate label to proteins destined for lysosomes. Function: 1) Digestion and recycling of materials in of worn-out organelles (autophagy). 2) Digestion of engulfed viruses and bacteria for self-defense. 3) Programmed cell death by rupturing of all lysosomes in the cell.  Mitochondria and Chloroplasts Are energy-converting organelles - Mitochondria are in almost all eukaryotic cells - Chloroplasts are found only in algae and certain plant cells - Mitochondria and chloroplasts grow and reproduce themselves (have their own DNA, transcriptional and translational machineries) ansfer chemical energy in glucose to ATP Convert light energy to ATP for the synthesis of glucose Evolution and oxygen - Cyanobacteria was evolved 3 billion years ago that can utilize light energy and CO2 to produce glucose. - O2 generated is toxic to other life forms, leading to major extinctions or O2 catastrophe. - New life forms are evolved to adapted to consume O2 and glucose to create energy. Chloroplast - chloroplasts are cyanobacteria adapted to live inside a plant. - In evolution, cyanobacteria entered into a cell in an endosymbiotic relationship for photosynthesis, thus producing a plant cell. - Mitochrondria - similarly, mitochrondria are also bacteria that are adapted to live in another cell in an endosymbiotic relationship for aerobic respiration. Cell and Energy Mitochondria - ATP (adenosine triphosphate): The rechargeable energy carrier used by most cellular processes. - Energy is extracted from food to recharge ADP (adenosine diphosphate) to ATP in mitochondria. - InOxygen interacts the inner with electrons membrane to generate sac, the ATP synthasehigh pushenergy H +across H + ions ions. the membrane to recharge ADP to ATP. - In summary, respiration is oxygen in to burn the food, and ATP is generated with CO 2 out as a side product From: bodell.mtchs.org Stage 3: electron transport chain/ATP synthase action From Khan Academy Chloroplast - light energy is used to split H2O to generate H+ and O2. - O2 is a side product that leaves the plant cells. - H+ ions are used to generate ATP by ATP synthase. - Calvin cycle in the light-independent reaction produce glucose (in fact, glyceraldehyde-3-phosphate) using CO2 as the raw material driven by ATP and high energy H+. - In summary, photosynthesis is using light as the energy source and CO2 as raw material to synthesize glucose with the waste O 2 out as a side product Plasma membrane - Helps maintain the cell as a distinct entity and allows metabolic events physically separated from the outside environment - Regulate the passage of material into and out of the cell - Are complex and dynamic structure made of phospholipid and proteins (They are in constant motion) - Phospholipids form bilayers in water - A phosphoplipid contains two fatty acid chains (hydrophobic) linked to glycerol with a phosphate group (hydrophilic) => An Hydrophob Hydrophilic amphipathic molecule ic tails head Plasma membrane Fluid Mosaic Model: - Proteins embedded in a fluid bilayer of phospholipids Membrane fluidity (mosaic pattern) - The mosaic pattern is not static - Position of many proteins are constantly changing in a fluid sea of phospholipid rye and Edidin’s experiment Cell surface proteins perform many functions, including transporting materials, serving as enzymes for chemical reactions, and transmitting information.  Question time! True or False Q: Lysosomes are responsible for the programmed cell death or apoptosis. Q: Chloroplasts in plants were originally cyanobacteria that had adapted to live in the plant cells in an endosymbiotic manner. Q: O2 is the raw material for photosynthesis to produce glucose. Q: The Krebs cycle uses O2, so in the absence of oxygen, it does not occur. Q: Mitochondria are found only in animal cells but not in plant cells. Q: In Calvin cycle, light energy is used to split water into H+ ion and oxygen.