Gen Bio Lessons 4-5 PDF

Lesson 4: Cellular Transport What is the difference between a Membrane and Cell Wall? - Membrane: Composed of Phospholipid bilayer - Cell Wall: Composed of Cellulose Remember this (Membrane): - Composed of Proteins and lipids, most abundant layer is Phospholipid bilayer What is the function...

Lesson 4: Cellular Transport What is the difference between a Membrane and Cell Wall? - Membrane: Composed of Phospholipid bilayer - Cell Wall: Composed of Cellulose Remember this (Membrane): - Composed of Proteins and lipids, most abundant layer is Phospholipid bilayer What is the function of the Cell Membrane? - Barrier: it keeps the internal environment of the cell protected and anything harmful outside - Gatekeeper: semi-permeable, it selects what molecules or ions that can enter the cell - Communication Channel: cell to cell communication - Signaling: once the cell membrane receives the signal, it responds - Adhesion: forms junctions among the cells for them to be connected Structure of Cell Membrane: Amphipathic: semi-permeable - Head - negatively charged, polar, hydrophilic - Tail - uncharged, nonpolar, hydrophobic Phospholipid bilayer - Two adjacent layers 3 Components of Phospholipid 1. Phosphate group 2. Glycerol backbone 3. Fatty acids Fluid Mosaic - fluid: not a rigid structure, phospholipids flow and move constantly - mosaic: composed with proteins, carbohydrates, and lipids embedded within the phospholipid bilayer What is the function of cholesterol embedded in the cell membrane? - reduces membrane fluidity, “fluidity buffer” - temperature regulator: prevents melting or solidifying of cell membrane Membrane Proteins 1. Integral proteins - embedded in the cell membrane permanently Different Integral Proteins Transport proteins (carrier and channel): - Carrier proteins bind to the proteins and undergo conformational change, change shape - Channel proteins on the other hand allow specific ions to enter, already in that state - Receptor proteins: signals and initiate a cellular response - Enzyme proteins: catalyzing specific reactions, speeds up reaction - Other proteins: - Attachment proteins for support and binding to cytoskeleton - Glycoproteins for cell to cell recognition, “id-tags” and vital immune system 2. Peripheral proteins - not embedded in the cell membrane; loosely bound to the surface and sometimes attached to the integral proteins, play roles in signaling, structural support Membrane structure results in selective permeability: form fits function, allows some substances to cross more easily than others Permeability of the Lipid Bilayer - What is not allowed to enter and exit the cell membrane? Polar molecules like glucose and ions Important Terms for LAB ACTIVITY: Diffusion - simple and facilitated (passive transport), movement of different molecules of different substances down the concentrated region Concentration Gradient - region where there are equal concentration between the environment Osmosis - water molecules are moving across the region from high to low concentration, diffusion of water molecules through the membrane Tonicity - (remove and add water inside the cell) - hypotonic: less solute in the cell which makes the movement of the water towards the cell, it becomes turgid - isotonic: no change between solute and water concentration, it is flaccid - hypertonic: more solute outside the environment of the cell, movement of the water is outside the cell which undergoes plasmolysis, water moves outside cell Flaccid - water loss Plasmolysis - osmotically-induced shrinkage of the cytoplasm Turgid - healthy state for most plant cells Types of Transport Across the Cell Membrane 1. Passive - simple diffusion, osmosis, facilitated diffusion 2. Active - sodium-potassium pump, bulk transport (endocytosis, exocytosis) Passive - movement of the substance across the membrane without energy investment, non-polar molecules - moves across the membrane in any direction until the equilibrium is reached Simple Diffusion - does not require the assistance of membrane proteins - nonpolar and hydrophobic (oxygen, nitrogen, carbon dioxide) molecules simply diffuse - substance moves down its concentration gradient, high to low concentration What is the driving force for the movement of molecules through simple diffusion? - Concentration gradient: there is an equal concentration in the region in order to achieve balance and equilibrium Osmosis - passive movement of water molecules from an area of high concentration to low concentration - tonicity: removing or adding of water inside cell, concentration of solutes that cannot cross the membrane (nonpenetrating solutes) relative to that inside the cell - hypertonic: higher solute outside, higher water inside, water moves out, cell shrinks - isotonic: equal solute, equal water, no net movement, normal - hypotonic: higher solute inside, higher water outside, water moves in, cell swells Plasmolysis - plasmo refers to cytoplasm, lysis refers to process of losing water Why are vegetables sprayed in the grocery stores? - This is to maintain the water content within the vegetable, prevent it from evaporating and drying out the contents, fibers, and vitamins. Contractile - pumps water Glucose and Ions - polar molecules, hydrophilic in nature, which is why they are unable to pass through the cell membrane Facilitated Diffusion - transport proteins: carrier and channel - glucose: carrier channel, stay within the fell, keeps entering inside - ions: moves via channel proteins (ion channels), for muscle contraction and nerve signal transmission Active - low to high concentration, atp (adenosine triphosphate) is needed, goes against concentration gradient Sodium-Potassium Pump - pumps 3 Na+ out of the cell - pumps 2 K+ into the cell - creates the electrochemical gradient - 3 Na+ binds to the protein, triggering phosphorylation - phosphorylation - atp (adenosine triphosphate) becomes adp (adenosine diphosphate) - as the 3 Na+ exits the cell, the K+ binds into the protein indicating the release of the phosphate group Proton pumps (primary active transport) - active transport protein that uses atp to transport hydrogen ions out of a cell against concentration gradient that generates voltage in the process Cotransporter (secondary active transport) - two or more molecules across a membrane together in the same or opposite directions - indirectly uses atp - rely on the energy of the concentration gradient created by the primary active transporters Can Na-K pump be a cotransporter? - no, as the movement of both are not simultaneous Endocytosis and Exocytosis - bulk transport: movement of large molecules like proteins and polysaccharides across the cell membrane through vesicles Endocytosis - endo: inside or internal, cyto: refers to cell, sis: process or movement - process of substances moving inside the cell, requires energy - a small area in a cell membrane will sink inward and form a pocket - pocket deepens and pinches in - vesicle forms with materials from outside of the cell and will be released inside - 3 Types of Endocytosis - Phagocytosis - cell eating, engulfs the molecule and will be released within the cell - Pinocytosis - cell drinking - Receptor - mediated - receptor proteins Exocytosis - exo: outside or external, cyto: refers to cell, sis: process or movement - process of substances moving outside the cell, requires energy - fusion of vesicles with the cell membrane, secretory cells that export products Lesson 5: Photosynthesis Photosynthesis - feeds the biosphere - Photoautotrophs - can produce their own source of energy via photosynthesis - Ecosystem Service Type - Supporting Services - As a Redox Process - - 2 Stages - Light Dependent Reactions (photo) - depends energy of the sun in order to process ; the carbon cycle ; thylakoid - Light Independent Reactions (x) - what it needs: products of the light reactions - Redox Reaction - 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 - Carbon dioxide is reduced into sugar and water oxidation gives molecular oxygen “Why do plants appear green?” - the presence of chlorophyll - every color is absorbed EXCEPT the green pigment (not limited to every plant) Roles of Photosystems - Photosystem II: gets excited, splits water to provide electrons and H+ ions, creating oxygen as by-product, primary electron acceptor, chlorophyll a and accessory pigments - Photosystem I: reduce NADP+ to NADPH Steps in Light Reaction: Photosystem II and I 1. Excitation of photosystems by light energy 2. Photolysis of water = electrons, H+, oxygen 3. Production of ATP via an electron transport chain (PSII) 4. Reduction of NADP+ to NADPH Photosystem II Excitation - light energy is absorbed until it reaches chlorophyll a What is P680? - pair or chlorophyll a = P680 nm - What will happen to P680 after the electron has been transferred? Becomes oxidized, more protons than electrons - Oxidation: P680 moves to primary electron acceptor, because it loses electrons Photolysis - water is split and electrons replenished the pigment - oxygen is by-product, 2 H+ are released in the thylakoid space ATP Formation - going against the proton gradient - loses energy as they move across - proton gradient come from the hydrogen ions that were released from the splitting of water (photolysis) - the energy from the gradient is used to make ATP called chemiosmosis, first product has been created Photosystem I - like PSII, it will also capture light and other process - production happens again to form NADP+ to NADPH - 2 electrons are needed to catalyze NADP+ to NADPH, second product has been created Why P700? - required wavelength for PSI to happen