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Vacuoles are membranous sacs Vacuoles –Two types are the contractile vacuoles of protists and the central vacuoles of plants Contractile vacuoles Central vacuole (a) Contractile vacuoles in a protist(b) Central vacuole in a plant cell

Cytoskeleton Mitochondrion Nucleus Rough endoplamsic reticulum (ER) Ribosomes Smooth endoplasmic reticulum (ER) Golgi apparatus Plasmodesmata Plasma membrane Chloroplast Cell wall Central vacuole Not in animal cells Plant Cells

Plant cells are encased by cell walls Walls of two adjacent plant cells Vacuole Plasmodesmata (channels between cells) Plant Cells

Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy Chloroplasts Inner and outer membranes of envelope Space between membranes Stroma (fluid in chloroplast) Granum

Conservation of Energy Energy is defined as the capacity to perform work. Kinetic energy is the energy of motion. Potential energy is stored energy. Climbing the steps converts kinetic energy of muscle movement to potential energy. On the platform, the diver has more potential energy. Diving converts potential energy to kinetic energy. In the water, the diver has less potential energy.

Energy Conversion Fuel rich in chemical energy Energy conversion Waste products poor in chemical energy Gasoline  Oxygen Carbon dioxide  Water Energy conversion in a car Energy for cellular work Energy conversion in a cell Heat energy Heat energy Carbon dioxide  Water Food  Oxygen Combustion Cellular respiration Kinetic energy of movement ATP

Food Calories A calorie is the amount of energy that raises the temperature of one gram of water by 1 degree Celsius. (a) Food Calories (kilocalories) in various foods Cheeseburger Spaghetti with sauce (1 cup) Pizza with pepperoni (1 slice) Peanuts (1 ounce) Apple Bean burrito Fried chicken (drumstick) Garden salad (2 cups) Popcorn (plain, 1 cup) Broccoli (1 cup) Baked potato (plain, with skin) Food CaloriesFood

Food Calorie Consumption (b) Food Calories (kilocalories) we burn in various activities Activity Food Calories consumed per hour by a 150-pound person* Running (7min/mi) Sitting (writing) Driving a car Playing the piano Dancing (slow) Walking (3 mph) Bicycling (10 mph) Swimming (2 mph) Dancing (fast) *Not including energy necessary for basic functions, such as breathing and heartbeat

ATP and Cellular Work Main types of (cellular) work: mechanical transport chemical

The Structure of ATP TriphosphateDiphosphate Adenosine Energy ATPADP PPPPPP Phosphate (transferred to another molecule) – ATP (adenosine triphosphate) Consists of adenosine plus a tail of three phosphate groups Is broken down to ADP and a phosphate group, releasing energy

ATP ADP P P P P P P P P X XY Y (a) Motor protein performing mechanical work (b) Transport protein performing transport work (c) Chemical reactants performing chemical work Solute Solute transported Protein moved Product madeReactants Transport protein Motor protein ATP and Cellular Work

Enzymes – Metabolism is the total of all chemical reactions in an organism. – Most metabolic reactions require the assistance of enzymes, proteins that speed up chemical reactions. Induced Fit: Every enzyme is very selective, catalyzing a specific reaction.

(a) Without enzyme (b) With enzyme Reactant Products Activation energy barrier Activation energy barrier reduced by enzyme Enzyme Energy level Activation Energy – Activation energy Activates the reactants Triggers a chemical reaction – Enzymes lower the activation energy for chemical reactions.

(a) Enzyme and substrate binding normally (b) Enzyme inhibition by a substrate imposter (c) Enzyme inhibition By a molecule that Causes the active site to change shape Substrate Active site Inhibitor Enzyme Enzyme Inhibitors

Traffic Across Membranes Passive transport Active transport Exocytosis Endocytosis

Traffic Across Membranes Diffusion – a process in which molecules move from an area of high concentration to an area of low concentration Molecules of dyeMembrane (a) Passive transport of one type of molecule Net diffusion Equilibrium

Traffic Across Membranes Animal cell Plant cell Normal Flaccid (wilts) Lysing Turgid Shriveled Plasma membrane H2OH2O H2OH2O H2OH2OH2OH2O H2OH2O H2OH2O H2OH2O H2OH2O (a) Isotonic solution (b) Hypotonic solution (c) Hypertonic solution

Traffic Across Membranes – Active transport requires energy to move molecules across a membrane. Lower solute concentration Higher solute concentration ATP Solute

Traffic of Large Molecules – Exocytosis is the secretion of large molecules within vesicles. Outside of cell Cytoplasm Plasma membrane

Traffic of Large Molecules – Endocytosis takes material into a cell within vesicles that bud inward from the plasma membrane.

Passive Transport (requires no energy) Active Transport (requires energy) DiffusionFacilitated diffusionOsmosis Higher solute concentration Lower solute concentration Higher water concentration (lower solute concentration) Lower water concentration (higher solute concentration) Solute Higher solute concentration Lower solute concentration ATP Solute Water Solute MEMBRANE TRANSPORT