Cell Biology Lecture 7 PDF

Lecture 7 7 Cellular Structure  Lysosome A lysosome is a membrane-bound organelle found in eukaryotic cells that contains hydrolytic enzymes responsible for breaking down biomolecules, including proteins, lipids, carbohydrates, and nucleic acids. Lysosomes play a key role in cellular processes s...

Lecture 7 7 Cellular Structure  Lysosome A lysosome is a membrane-bound organelle found in eukaryotic cells that contains hydrolytic enzymes responsible for breaking down biomolecules, including proteins, lipids, carbohydrates, and nucleic acids. Lysosomes play a key role in cellular processes such as degradation of waste materials, autophagy, and recycling of cellular components, contributing to cellular homeostasis and defense against pathogens. Low internal pH assists with enzymatic degradation of proteins and lipids (i.e. hydrolysis) by hydrolytic enzymes. Assist with digestion of material that entered by phagocytosis Assist with recycling of internal organelles, autophagy.  Lysosomal storage disorders ~50 genetic disorders associated with malfunctioning of lysosomes. Tay-Sachs: Tay-Sachs disease is named after Warren Tay, a British ophthalmologist, and Bernard Sachs, an American neurologist, who identified key aspects of the disease in the late 19th century. In 1881, Tay observed the characteristic “cherry-red spot” on the retina, while in 1887, Sachs detailed the neurological symptoms, inheritance patterns, and prevalence among Ashkenazi Jews. Their contributions led to the naming of the disease, recognizing their pioneering work in its clinical and genetic understanding. Tay-Sachs disease - a defect in a lysosomal enzyme that digests gangliosides (a type of lipid); lipid builds up in brain causing neurological and other defects.  Lysosomal storage disorders Gaucher’s disease Gaucher's disease, named after French physician Philippe Gaucher, was first described in 1882. He identified abnormal cells accumulating in the spleen due to a lipid storage disorder. The disease is caused by a deficiency of the enzyme glucocerebrosidase, leading to glucocerebroside buildup in the spleen, liver, and bone marrow, resulting in:enlarged liver and spleen, fatigue, anemia, bone pain and fractures, and easy bruising and bleeding.  Vacuoles in plants/fungi, similar to Central vacuole lysosomes plants: central vacuole, stores water, ions (K+, Cl-) Cytosol Nucleus Central vacuole Cell wall Chloroplast 5 µm  Peroxisomes Peroxisomes are roughly spherical and often have a granular or crystalline core that is thought to be a dense collection of enzyme molecules. Chloroplasts and mitochondria cooperate with peroxisomes in certain metabolic functions.  Peroxisomes Bound by a single membrane Contain enzymes such as catalase for the removal of hydrogen atom, producing Hydrogen peroxide (H2O2) Use Oxygen to break down Fatty acids In liver peroxisome breaks down alcohol  Mitochondria Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Inner membrane Cristae Matrix 0.1 µm - cellular respiration occurs here  contain chlorophyll Thylakoids– inner membranes where the light reactions of photosynthesis take place found in plants, algae Endosymbiont Theory Endosymbiont Theory Both mitochondria and chloroplasts have their own genomes, transcription and ribosomes. I have an idea… let’s eat some algae, suck out their chloroplasts, and store them in our cells… Elysia chlorotica  The Cytoskeleton microtubules microfilaments Microtubule DNA Microfilaments 0.25 µm - organelles do not just ‘float’ in cells - three types of cytoskeletal fibers: - Microtubules, microfilaments, and intermediate filaments  Microtubule Microtubule is a component of the cytoskeleton in eukaryotic cells. It is a hollow, tube-like structure made of protein subunits called tubulin. Microtubules provide structural support, help maintain cell shape, and play key roles in long distance intracellular transport, cell division (forming the mitotic spindle), and the movement of organelles and vesicles within the cell.  Microfilaments Microfilaments are thin, thread-like structures made of the protein actin, found in the cytoskeleton of eukaryotic cells. They provide mechanical support, maintain cell shape, and play key roles in cell movement, short distance intracellular transport, and division. They are the smallest filaments in the cytoskeleton, typically involved in dynamic cellular processes like cytokinesis and amoeboid movement.  Intermediate filaments Intermediate filaments are strong, rope-like fibers made of proteins such as keratin or vimentin. They provide mechanical support, maintain cell shape, and anchor organelles.  Concepts Eukaryotic cells have internal membranes that compartmentalize their functions The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes The endomembrane system regulates protein traffic Mitochondria and chloroplasts change energy from one form to another and performs metabolic functions The cytoskeleton is a network of fibers that organizes structures and activities in the cell Extracellular components and connections between cells help coordinate cellular activities A cell is greater than the sum of its parts Many components work together in a functioning cell. Which of the following statements best describes the structure of a membrane based on the fluid mosaic model? A) The membrane is composed of a fluid bilayer of phospholipids between two layers of hydrophilic proteins. B) The membrane is composed of a single layer of fluid phospholipids between two layers of hydrophilic proteins. C) The membrane is composed of a mosaic of fluid polysaccharides and amphipathic proteins. D) The membrane is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins. Which of the following statements best describes a characteristic of biological membranes? A) Phospholipids move laterally within the plane of the membrane. B) Phospholipids frequently flip-flop from one layer of the membrane to the other. C) Phospholipids generally occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane. D) Phospholipids are arranged with hydrophilic tails in the interior of the membrane. Which of the following types of molecules are excluded from the hydrophobic portion of the phospholipid bilayer? A) transmembrane proteins B) integral membrane proteins C) peripheral membrane proteins D) cholesterol Which of the following statements best describes how unsaturated fatty acids increase membrane fluidity at lower temperatures? A) The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly. B) Unsaturated fatty acids have a higher cholesterol content, which prevents adjacent lipids from packing tightly. C) Unsaturated fatty acids are more nonpolar than saturated fatty acids. D) The double bonds block interaction among the hydrophilic head groups of the lipids.