Life 102 - Week 05 Notes
Life 102 - Week 05 Notes Life 102
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This 6 page Class Notes was uploaded by AveryLemler on Friday September 30, 2016. The Class Notes belongs to Life 102 at Colorado State University taught by Dr. Erik Arthun in Fall 2016. Since its upload, it has received 2 views. For similar materials see Attributes of Living Systems in Life Sciences at Colorado State University.
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Date Created: 09/30/16
Life 102 - CSU Week 05 Notes StudySoup - Avery Chapter 7: Membrane Structure and Function Highlight: Topics covered extensively in lecture Highlight: Helpful examples 7.1: Cellular membranes are fluid mosaics of lipids and proteins ● Plasma Membrane: an amphipathic, selectively permeable phospholipid bilayer with proteins embedded that serves as a structural boundary ○ Amphipathic: hydrophobic and hydrophilic regions ○ Phospholipids can move freely within the bilayer ■ Lateral movement is very common ■ Flip-flop is very rare ● Membrane Proteins: proteins embedded in the plasma membrane that give the membrane its function ○ Integral Membrane Proteins: proteins inserted in the membrane that usually go all the way through to both sides of the plasma membrane ■ Channel Protein: specific for specific molecules ● Like a tunnel ● Water diffuses through a channel protein called an aquaporin ○ Aquaporins speed up the process even though water can diffuse directly through the membrane ■ Carrier Protein: changes shape to pass specific substances down their concentration gradients ● Like a revolving door ○ Peripheral Membrane Proteins: proteins attached to the surface of one side of the plasma membrane ○ 50% of the weight of the membrane is made of proteins ○ Functions of membrane proteins: ■ Transport of molecules across membranes ● Like a revolving door Life 102 - CSU Week 05 Notes StudySoup - Avery ■ Receptor for extracellular signals ● Send chemical messages across the membrane ■ Recognition of other cells ● Ex: different blood types ● Ex: glycoproteins in membrane serve as identification ■ Forming intercellular junctions ● Proteins from different cells binding together ● Like anchors ■ Anchoring cytoskeleton to extracellular ● Helps maintain cell shape and location of proteins ■ Catalyzing enzymatic reactions ● Help with chemical reactions and can be grouped into metabolic pathways ● Fluid Mosaic Model: components of the membrane can move freely in lateral direction ○ Like a swimming pool with different types of balls floating around in it ○ Membrane proteins float freely ○ Things that affect membrane fluidity: ■ Temperature ■ Type of phospholipids ● Saturated vs. Unsaturated ○ Solid or liquid at room temperature ■ Cholesterol ● Keeps membrane fluidity optimal at different temperatures ○ At moderate temperatures, cholesterol reduces the fluidity ○ At low temperatures, cholesterol disrupts regular packing of phospholipids, hindering solidification Life 102 - CSU Week 05 Notes StudySoup - Avery 7.2: Membrane structure results in selective permeability ● Transport of Molecules Over Membranes: maintains the potential energy of the cell by moving inorganic ions in and out ○ Metabolic Needs: ■ Nutrients and oxygen in, wastes and carbon dioxide out ● Selectively Permeable: some substances can cross easily, others cannot (based on polarity) ○ Small, uncharged/hydrophobic molecules slip through easily ○ Large, uncharged/hydrophobic molecules get through easily by dissolving in the hydrophobic lipids ○ Large, charged molecules do not pass through easily, need to go through membrane proteins 7.3: Passive transport is diffusion of a substance across a membrane with no energy investment ● Diffusion: the movement of molecules so they spread out evenly in a given space ○ Different molecules diffuse independently of each other down their own concentration gradient ● Passive Transport: driven by diffusion, no energy required, goes from high to low concentration ○ Molecules can go right through the membrane or use channel/carrier proteins ● Facilitated Diffusion: diffusion across membrane with the help of a carrier of channel protein down a concentration gradient with no energy required ○ Mainly ions and large polar molecules ○ Faster than diffusion across the membrane ● Osmosis: diffusion of water across a membrane towards the side with the lowest water concentration Life 102 - CSU Week 05 Notes StudySoup - Avery ○ WATER FOLLOWS SOLUTES: water will go to the area with more solute to make the concentration of solute equal on both sides ■ If you drink salt water, your cells will shrivel because there is a higher solute concentration on the outside of the cells ● Tonicity: the relative concentration of solutes dissolved in solution which determines the direction of diffusion ○ Hypertonic Solution: the solution with the relatively higher total solute concentration ■ Cell loses water when in a hypertonic solution ○ Hypotonic Solution: the solution with the relatively lower total solute concentration ■ Cell gains water when in a hypotonic solution ■ Plant cells need a hypotonic environment so water comes into the cell and puts positive pressure on the cell wall so the plant doesn’t wilt ○ Isotonic Solution: solutions with the same total solute concentration ■ No net movement of water ■ Animal cells need an isotonic environment (shrivel in a hypertonic environment and burst in a hypotonic solution) 7.4: Active transport uses energy to move solutes against their gradients ● Active Transport: process where a transport proteins pumps a molecule/ion across a membrane against its concentration gradient, requiring the input of ATP ○ Sodium/Potassium Pump: proteins in the cell membrane of animal cells that pump Na away from the cytoplasm, and K towards the cytoplasm, requiring ATP ● Membrane Potential: unequal distribution of charged ions on two sides of a membrane, caused by ions being pumped across a membrane ○ Like a battery Life 102 - CSU Week 05 Notes StudySoup - Avery ■ Creates a voltage across the membrane and an electrochemical gradient ● Electrochemical Gradient: diffusion gradient for charged substances, created by combined effects of membrane potential and concentration gradient 7.5: Bulk transport across the plasma membrane occurs by exocytosis and endocytosis ● Exocytosis: substances leave cells in a vesicle formed by the plasma membrane ○ Proteins, complex particles, and polysaccharides ● Endocytosis: substances enter cells in a vesicle formed by the plasma membrane ○ Proteins, complex particles, and polysaccharides ○ Phagocytosis: cell engulfs a particle and digests it with a lysosome ■ “Cellular eating” ○ Pinocytosis: cell captures extracellular fluid that contains dissolved substances ■ “Cellular drinking” ○ Receptor Mediated Endocytosis: cell acquires a specific substance that is found in low abundance; receptors are recycled ■ Much more specific that phagocytosis and pinocytosis ■ Like using a magnet to find a needle in a haystack Chapter 8: An Introduction to Metabolism 8.1: An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics ● Metabolism: all the biochemical reactions that occur in cells ○ Transformation of matter and energy Life 102 - CSU Week 05 Notes StudySoup - Avery ● Catabolism: breakdown of larger molecules into smaller ones ○ Releases energy stored in ATP ○ Ex: cellular respiration ● Anabolism: build-up of larger molecules out of smaller ones ○ Uses the ATP released in catabolism ○ Ex: synthesis of proteins from amino acids ● Energy: the capacity to cause change ○ Rearrange matter, physically move or change bonds ○ Potential Energy: e nergy provided by location or structure ○ Kinetic Energy: e nergy of motion ○ Chemical Energy: energy stored in bonds and released in chemical reactions ● Law of Energy Conservation (first law of thermodynamics): energy cannot be created nor destroyed, but can only be transferred or converted to a different form ○ Amount of energy released in a catabolic reaction is the same amount of energy used in an anabolic reaction ■ Energy of the universe is constant 8.2: The free-energy change of a reaction tells us whether or not the reaction occurs spontaneously ● Gibb’s Energy/Free Energy: the amount of energy in a molecule that is available to do work ○ “Useful energy” ● Exergonic Reaction: reaction that releases energy ● Endergonic Reaction: reaction that costs energy
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