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week2 - chp3.docx

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Health Sciences
HSCI 100
Nienke Van Houten

Chapter 3: the cell PROKARYOTIC CELLS EUKARYOTIC CELLS (third domain of life) - First cells to evolve - Nucleus that has DNA - Lacks nucleus - Membrane bound organelles - Represented by bacteria & archaea - Plants, animals, fungi, protists - Circular DNA in cytoplasm - Coiled, linear DNA - cytoskeleton - cytoskeleton SURFACE TO VOLUME RATIO - as cell gets larger, SA increases much more slowly than volume o nutrients enter cell and waste leaves @ surface  larger cell difficulty moving nutrients across inadequate surface  would not survive PLASMA MEMBRANE - functions o boundary between internal/ext enviro o selectively permeable o cell-cell recognition  recognize glycoproteins – foreign invaders like bacteria o communication between cells  receptors o binding pairs/group of cells together  cell adhesion molecules (CAMs)  stick cells together to form tissues and organs - fluid mosaic model o cholesterol as support o carbohydrates on proteins & lipids on the outer layer o selectively permeable – allows some things in, keeps other substances out - structure o hydrophilic heads face outside cell interact with extracellular fluid o hydrophilic heads facing inside interact with cytoplasm o hydrophobic tails point toward and hold membrane together MEMBRANE TRANSPORT 1. Diffusion - Random move from higher concentration to lower concentration - Passive transport (doesn’t require energy) - Concentration gradient: difference in relative number of molecules/ions in given substance in two adjacent areas 2. Facilitated diffusion - Doesn’t require energy - Water soluble substances repelled - Carrier proteins bind to water-soluble substance - With concentration gradient - Protein channel carries particles through 3. Osmosis (cross through protein) - Water moves from higher h2o concentration to lower - Hypo/hypertonic 4. Active transport - Carrier protein + energy from ATP - Against concentration gradient (lower concentration to higher) - Na+/K+ pump – bodies have higher potassium, lower sodium - Sodium out/Potassium in 5. Exocytosis - Fusion of vesicle with plasma membrane - Transports molecules outside cell 6. Endocytosis - Transports molecules inside cell - Invagination of plasma membrane to form vesicle - Membrane pinches in and forms vesicle that brings substances in TONICITY: - Hypertonic – more solute than inside of cell o Water flows out of cell o Cell shriveling - Hypotonic – less solute than inside of cell o More water outside – water flows into cell o Cell swelling/burst - Isotonic – solutions equal amounts of solute inside & outside of cell. No effect ORGANELLES – discrete compartments that work together - Nucleus o Function:  Contains DNA and controls cell activity  separates genome/dna from cytosol, transcription from translation o Structure:  Nuclear envelope - Double membrane surrounds nucleus and separates from cytoplasm (nuclear envelope)  Nuclear pores – communication between nucleus and cytoplasm  Chromosomes – threadlike structures made of DNA and associated with proteins  Nucleolus – specialized region in nucleus  Forms an
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