Chapter 5. The Working Cell

Transcription

1 Chapter 5 The Working Cell

2 ENERGY CONCEPTS Conservation of Energy The world both in and around us runs on energy. But, what exactly is energy? Energy the capacity to cause change Potential energy stored energy Food, muscles, standing on a diving board Kinetic energy energy of motion Using muscles (moving), falling from diving board Conservation of energy energy cannot be created or destroyed. It just changes. Potential Kinetic

3 On the platform, the diver has more potential energy. Climbing the steps converts kinetic energy of muscle movement to potential energy. Diving converts potential energy to kinetic energy. In the water, the diver has less potential energy. Figure 5.1

4 Heat & Entropy Every energy conversion/change releases some randomized energy in the form of heat. Heat is: A type of kinetic energy A product of all energy conversions Energy in its most disordered, chaotic form the energy of aimless molecular movement Entropy the measure of the amount of disorder in a system The Bedroom Effect : easily becomes messy (chaos) & requires effort to clean (order)

5 Chemical Energy Chemical energy energy stored in molecules Bonds between atoms can store a lot of energy Organic compounds (carbs, fats, hydrocarbons) are rich in chemical energy Example: Car engine Gasoline + oxygen + spark = combustion Reaction breaks down gasoline à releases energy (combustion) Explosive energy pushes pistons that turn wheels Only 25% of fuel powers the car, the rest is turned into heat

6 Fuel rich in chemical energy Energy conversion Waste products poor in chemical energy Heat energy Gasoline + Oxygen Combustion Kinetic energy of movement Energy conversion in a car Carbon dioxide + Water

7 Fuel rich in chemical energy Energy conversion Waste products poor in chemical energy Heat energy Gasoline + Oxygen Combustion Kinetic energy of movement Energy conversion in a car Carbon dioxide + Water Heat energy Food + Cellular respiration ATP Carbon dioxide + Oxygen Energy for cellular work Energy conversion in a cell Water Figure 5.2

8 Chemical Energy Cellular Respiration = Food (fuel) à Energy Cells break down organic molecules (carbs & fats) from food for energy Humans use 34% of food energy to do useful work (move muscles). The rest = heat to regulate body temperature Calories amount of energy needed to raise the temp. of 1 gram of water 1 degree Celsius Food Calories (kilocalories) 1 kilocalorie = 1,000 Calories

9 Food Food Calories Cheeseburger Spaghetti with sauce (1 cup) Baked potato (plain, with skin) Fried chicken (drumstick) Bean burrito Pizza with pepperoni (1 slice) Peanuts (1 ounce) Apple Garden salad (2 cups) Popcorn (plain, 1 cup) Broccoli (1 cup) (a) Food Calories (kilocalories) in various foods Figure 5.3a

10 Activity Running (7min/mi) Dancing (fast) Bicycling (10 mph) Swimming (2 mph) Walking (3 mph) Dancing (slow) Playing the piano Driving a car Sitting (writing) Food Calories consumed per hour by a 150-pound person* *Not including energy necessary for basic functions, such as breathing and heartbeat (b) Food Calories (kilocalories) we burn in various activities Figure 5.3b

11 ATP & Cellular Work Chemical energy is: ATP Released by the breakdown of organic molecules Used to generate ATP Acts like an energy shuttle Stores energy obtained from food Releases it later when needed Structure = adenine + 3 phosphates Broken down to ADP + 2 phophates

12 Energy Triphosphate Diphosphate Adenosine P P P Adenosine P P P ATP ADP Phosphate (transferred to another molecule) Figure 5.4

13 ATP & Cellular Work Energy from ATP helps cells perform: 1. Mechanical work Muscle contractions 2. Transportation work Exchange molecules in/out of cells 3. Chemical work Creates chemical reactions

14 Motor protein ATP ADP P ADP P Protein moved (a) Motor protein performing mechanical work Figure 5.5a

15 Transport protein Solute P P ATP ADP P Solute transported (b) Transport protein performing transport work Figure 5.5b

16 P ATP X P X Y ADP P Y Reactants Product made (c) Chemical reactants performing chemical work Figure 5.5c

17 The ATP Cycle Cellular work spends ATP ATP à ADP Food à cellular respiration + ADP à ATP A working muscle cell spends and recycles about 10 million ATP molecules/second!

18 ATP Cellular respiration: chemical energy harvested from fuel molecules ADP P Energy for cellular work Figure 5.6

19 ENZYMES Metabolism all chemical reactions in an organism Most require the assistance of enzymes Enzymes proteins the speed up chemical reactions Very selective Act like docking stations for specific molecules (substrates) Example: Sucrase breaks down sucrose

20 Substrate (sucrose) Sucrase can accept a molecule of its substrate. Substrate binds to the enzyme. Enzyme (sucrase) Fructose Glucose H 2 O The products are released. The enzyme catalyzes the chemical reaction. Figure 5.9-4

21 Enzyme Inhibitors Enzyme Inhibitors prevent reactions by: Binding to enzymes first (imposters) Changing the enzyme s shape

22 Substrate Enzyme (a) Enzyme and substrate binding normally Figure 5.10a

23 Inhibitor Substrate Enzyme (b) Enzyme inhibition by a substrate imposter Figure 5.10b

24 Substrate Inhibitor Enzyme (c) Enzyme inhibition by a molecule that causes the active site to change shape Figure 5.10c

25 Enzyme Inhibitors Many beneficial drugs work by inhibiting enzymes. Penicillin (antibiotic) bacterial cell walls Ibuprofen (Motrin) stops pain signals Cancer drugs stop mitosis (cell division) Nerve gases & pesticides stop nerve signals

26 Membrane Function Membrane proteins perform many functions. The most important is transportation of materials in & out of the cell. Passive Transport: Diffusion & Osmosis Active Transport Endocytosis & Exocytosis

27 PASSIVE TRANSPORT Diffusion Passive Transport no energy required Diffusion movement of molecules from high concentration to low concentration Air = low concentration Bottle = high concentration

28 Molecules of dye Membrane Net diffusion Net diffusion Equilibrium (a) Passive transport of one type of molecule Figure 5.12a

29 Net diffusion Net diffusion Equilibrium Net diffusion Net diffusion Equilibrium (b) Passive transport of two types of molecules Figure 5.12b

30 PASSIVE TRANSPORT Osmosis Osmosis diffusion of water across a membrane Solute molecules dissolved in a liquid (water) Hypertonic higher concentration of solute Hyper = above Hypotonic lower concentration of solute Hypo = under Isotonic equal concentration of solute Iso = equal Diffusion = high to low

31 Hypotonic solution Hypertonic solution Isotonic solutions Sugar molecule Osmosis Selectively permeable membrane Osmosis Figure

32 Animal cell H 2 O H 2 O H 2 O H 2 O Normal Lysing Shriveled Plant cell H 2 O H 2 O H 2 O Plasma membrane H 2 O Flaccid (wilts) Turgid Shriveled (a) Isotonic (b) Hypotonic (c) Hypertonic Figure 5.14

33 Figure 5.15

34 Active Transport Active Transport requires energy (ATP) to move molecules across a membrane

35 Active Transport requires energy (ATP) to move molecules across a membrane Lower solute concentration Solute ATP Higher solute concentration Figure

36 Exocytosis secretion (release) of large molecules Exo = out Outside of cell Plasma membrane Cytoplasm Figure 5.17

37 Endocytosis absorption of large molecules En = in Figure 5.18

38 STUDY OF LIFE: Properties of Life Two types of endocytosis: 1. Phagocytosis cellular eating engulfs particles 2. Pinocytosis cellular drinking gulps fluid droplets