BSC2010 week 4
BSC2010 week 4 BSC 2010
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This 4 page Class Notes was uploaded by Tori Ruby on Friday January 29, 2016. The Class Notes belongs to BSC 2010 at University of Florida taught by Staff in Winter 2016. Since its upload, it has received 15 views. For similar materials see Integrated Principles of Biology 1 in Biological Sciences at University of Florida.
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Date Created: 01/29/16
January 25, 2016 Plant and algae cells contain plastids that can differentiate into organelles Chloroplast has double membrane o Stack of thylakoids is called a granum o Light energy is converted to chemical energy o Carbohydrate synthesis occurs in the stroma o Stroma: aqueous fluid in chloroplast Peroxisomes collect and break down toxic by-products of metabolism using specialized enzymes Vacuoles: mainly in plants and fungi o Store waste and toxins o Provide structure in plant cells called turgor pressure o Reproduction- colors attract insects o Catabolism: hydrolyze stored food for growth o Contractile vacuoles get rid of extra water Enlarge as water enters, quickly contract to dispel water Cytoskeleton o Supports o Hold organelles in position o Move organelles o Involved in cytoplasmic streaming o Interacts with extracellular structures to anchor cell o 3 types Microfilaments: 7 nm Intermediate: 10 nm Microtubules: 25 nm Plant cell wall: semi-rigid structure o Polysaccharide cellulose o Gel-like matrix contains cross-linked polysaccharides and proteins o Support o Barrier to infection January 27, 2016 Membrane structure o Lipids, proteins, carbohydrates contained in membrane o Called the fluid mosaic model o Phospholipids form a bilayer in which a variety of proteins “float” o Lipids form the hydrophobic core of the membrane Hydrophilic head interacts with water Hydrophobic tail o Lipid composition: types of fatty acids can increase or decrease fluidity (cholesterol is long-chain, saturated fat vs. unsaturated fat) o Temperature- cold decreases fluidity o Carbohydrates play a role in communication and adhesion Glycolipid Glycoproteins Proteoglycan How to cross membrane o Selective permeability: allows some substances to pass o 3 ways Passive transport does not require energy Simple diffusion Facilitated diffusion: channel or carrier proteins Active transport requires metabolic energy Vesicles transport large molecules o Diffusion: process of random movement toward equilibrium Diameter Temperature Concentration High concentration to low concentration Small nonpolar and uncharged molecules o Osmosis: diffusion of water across membranes Depends on concentration of structure molecules on either side Passes through aquaporins Isotonic: equivalent concentration of solute on either side of a bilayer Hypertonic: higher solute concentration on the outside of a cell Hypotonic: lower solute concentration on the outside of a cell o Facilitated diffusion for charged substances Channel proteins: used for ions, water Carrier proteins: used for sugars and amino acids o Active transport Primary active transport involves direct ATP hydrolysis Secondary active transport involves indirect ATP hydrolysis Macromolecules are too large Endocytosis Phagocytosis “cellular eating” Pinocytosis “cellular drinking” Receptor-mediated: specific molecules January 29, 2016 Cells can respond to many signals if they have specific receptors Signal transduction pathway Different responses o Autocrine: signals diffuse and affect same cells o Paracrine: signals diffuse and affect nearby cell o Hormones: signals reach distant cells Signal to receptor to response o Specific receptors for each signal o No signal can activate non specific receptors o No receptors respond to non specific signal Allosteric regulation: alteration in a protein’s shape as a result of bonding Ligand: signal molecules that fits in a 3D site on receptor proteins Ligands generally do not metabolize further. Binding may change the binding cite. o Change is reversible o An inhibitor can bind in place of a ligand Classified by location o Cytoplasmic receptors have ligands diffuse across membrane o Membrane receptors located through the membrane Classified by activity o Ion channel: gated ion channels, change 3D shape of a receptor o Protein kinase: change shape when ligand binds Can be activators or inhibitors Ex. Insulin o G protein-linked: partially inserted in bilayer, partially exposed on cytoplasmic surface Activated G protein- linked receptor exchanges GDP to GTP Ex. Fight or flight Second messenger: is intermediary between the receptor and the cascade of responses o Cyclic AMP o Distribute signal to activate more than one target
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