Living things transform energyEnergy makes things happen• Energy-the capacity to do work, to make things happen• Forms of energy – Radiant-solar energy – Chemical-food – Mechanical-motion – Electrical – Nuclear• Heat – Motion of atoms, ions, or molecules (mechanical) – Low quality energy because it is too dispersed to do useful work
• Potential energy-stored energy• Kinetic energy-energy in action• Ex. Person climbing ladder to diving board and diving into water. – Chemical-food – Kinetic-climbing ladder – Potential-higher altitude – Kinetic-diving to the water• Measuring energy – Calorie-amount of heat required to raise the o temperature of 1g of water by 1 C – Kilocalorie • 1,000 calories • Calories listed on nutrition labels
Two laws apply to energy and its use• The first law of thermodynamics – The law of conservation of energy-states that energy cannot be created or destroyed, but it can be changed from one form to another• The second law of thermodynamics – States that energy cannot be changed from one form to another without a loss of usable energy• Energy flows through living things, it does not cycle• The second law of thermodynamics tells us that as energy conversion occurs, disorder (entropy) increases because it is difficult to use heat to perform more work
Cellular work is powered by ATP (adenosine triphosphate)• ATP is a nucleotide-a monomer for DNA and RNA• Phosphate groups are unstable• ATP can break down into ADP+P• ADP can break down into AMP+P• ATP beakdown and regeneration is the ATP cycle• Exergonic reaction-releasing energy, performing work• Endergonic reaction-energy is required, constructing a building
ATP breakdown is coupled to energy-requiring reactions• Coupled reactions occur in the same place, at the same time, and is such a way that an energy-releasing (exergonic) reaction drives an energy-requiring (endergonic) reaction• Energy releasing reaction-hydrolysis of ATP
Enzymes speed chemical reactionsEnzymes speed reactions by lowering activation barriers• Enzyme-typically a protein molecule that functions as an organic catalyst to speed a chemical reaction without itself being affected by the reaction• A certain amount of energy (energy of activation) has to be put into a reaction and then the reaction will occur. An enzyme will lower the amount of energy required to start the reaction.• Each enzyme has a specific reaction it speeds
• Substrate-reactants in an enzymatic reaction• Active site-part of the enzyme where substrate forms an enzyme-substrate complex• Induced fit model-enzyme slightly changes shape to achieve optimum fit with the substrate• Products are released after reaction is complete• Active site is then ready to bind with another substrate molecule
Enzyme speed is affected by local conditions• Substrate concentration-enzyme activity increases as substrate concentration increases• Temperature-enzyme activity increases as temperature increases. If temperature is too high, the enzyme denatures and can no longer bind with substrate.• pH-enzymes have optimal pH for reactions. Extreme pH can denature the enzyme
• Cofactors – Inorganic ions or nonprotein organic molecules required by enzyme in order to be active – Inorganic ions-copper, zinc, iron – Nonprotein organic molecules-coenzymes- assist the enzyme and may accept or contribute atoms to the reaction • Vitamins are required for synthesis of coenzymes. If vitamin is not available, enxymatic activity decreases. – Inhibitor-reduces amount of product produced by an enzyme per unit time
Enzymes can be inhibitednoncompetitively and competitively• Metabolic pathway-series of linked reactions• Noncompetitive inhibition- inhibitor binds to the enzyme at a location other than the active site• Competitive inhibition-inhibitor and substrate compete for the active site of an enzyme• Inhibition is benefitial because once sufficient end product of a metabolic pathway is present, it is best to inhibit further production to conserve raw materials and energy.
The plasma membrane has many and various functionsThe plasma membrane is a phospholipid bilayer with embedded proteins• Plasma membrane in both bacteria and eukaryotes are phospholipid bilayer• Proteins are found within and along the membrane• Cholesterol-supports the membrane• Phospholipids and proteins can have cabohydrates attached. These are glycolipids and glycoproteins.
Proteins in the plasma membrane have numerous functions•Channel proteins-allow molecule to moveacross the membrane•Carrier proteins-combine with substance andhelp it move across the protein•Cell recognition proteins-glycoproteins (havecarbohydrates attached)-foreign cells have theirown glycoproteins that enable the immunesystem to recognize them and mound adefense
•Receptor proteins-have a binding site for aspecific molecule, protein then changesshape and causes a cellular response•Enzymatic proteins-carry out metabolicreactions directly•Junction proteins-form junctions betweencells, assist cell-to-cell communications
Malfunctioning plasma membrane proteins• Type 2 Diabetes-not enough carrier proteins for the amount of glucose in the blood• Color blindness-lack functional red or green photopigment protein• Cystic fybrosis-channel proteins that are not properly regulated
The plasma membrane regulates the passage of molecules into and out of cellsDiffusion across a membrane requires no energy• Diffusion-molecules move from a high concentration to a low concentration. The molecules follow the concentration gradient until equilibrium is reached – Passive transport since no energy is required – Small molecules, such as CO2 and O2, can diffuse through the plasma membrane
• Facilitated diffusion-water, glucose, amino acids, Na+, Cl-, and Ca2+ facilitated passage through membrane – Requires a transporter but no energy since it’s moving down its concentration gradient – Transporter moves specific substancesCarrier proteins are slower than channel proteins
• Osmosis-diffusion of water from low solute to high solute – Isotonic solutions-solute concentration is the same on both sides – Hypotonic solution-higher solute inside cell so water moves into the cell • Lysis-cells bursting when in hypotonic solution • Plant cells-experience turgor pressure, which allows plants to stand up – Hypertonic solution-solute concentration higher outside cell, water moves outFigure 5.10C
Active transport across a membrane requires a transporter and energy• Active transport-molecules more across plasma membrane accumulating on one side of the cell. Moving against the concentration gradient so energy is required
Bulk transport involves the use of vesicles• Endocytosis or exocytosis• Moves molecules too large to be moved by carrier proteins such as polypeptides, polysaccharides, or polynucleotides• Phagocytosis-large particle (like food) is taken in, common in unicellular organisms• Pinocytosis-take in very small particles• Receptor-mediated endocytosis. Allows bulk transport of specific substances.
In multicellular organisms, cells communicateExtracellular material allows cells to join together and communicate• Plant cells- – Plasmodesmata-numerous channels that pass through the cell wall. This allows direct exchange of some materials between adjunct plant cells and, ultimately, all the cells of a plant.
• Animal cells – Anchoring junctions- connect cells in tissues that stretch – Tight junctions-prevent digestive juices from leaking – Gap junctions-plasma membrane channels join – Extra-cellular matrix- where junctions are not present • Cartilage and bone