Key Concepts - All Cells Use Energy Energy Conversions - Reactions Absorb or Release Energy Endergonic, Exergonic - ATP is Cellular Energy

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1 Key Concepts - All Cells Use Energy Energy Conversions - Reactions Absorb or Release Energy Endergonic, Exergonic - ATP is Cellular Energy ATP Cycle - Enzymes Speed Up Reactions Enzyme Function, Factors Affecting Enzyme Activity - Membrane Transport Passive and Active Transport, Endocytosis, Exocytosis A female firefly eating a male of another species 1!

2 Cellular respiration I. Membrane Structure and Function II. Energy and the Cell III. How Enzymes Function The Big Ideas 2!

3 Chemical Reactions Release/Store Energy Chemical rxns either Release energy (exergonic) Cellular respiration Require energy input and store energy (endergonic) Photosynthesis Cells manage energy w/ energy coupling - Use energy from exergonic rxns to drive endergonic rxns 3!

4 Reactants Potential energy of molecules Energy released Products Amount of energy released Exergonic reaction, energy released 4!

5 Products Potential energy of molecules Reactants Energy required Amount of energy required Endergonic reaction, energy required 5!

6 Cellular Respiration Happens in the Mitochondria Chemical breakdown of glucose using O 2 releases CO 2, water and energy That energy is captured to make ATP! 6!

7 Fuel Energy conversion Waste products Heat energy Cellular respiration Glucose Carbon dioxide + + ATP ATP Oxygen Energy for cellular work Water Energy conversion in a cell 7!

8 ATP is Cellular Energy Currency Adenosine triphosphate (ATP) is a nucleotide that temporarily stores energy ATP has high energy phosphate bonds Figure 4.6 8!

9 Removing the endmost phosphate group (by hydrolysis) releases the energy stored in ATP. The cell uses this energy to do work! 9!

10 Phosphorylation Hydrolysis The ATP Cycle ATP Energy from exergonic rxns ADP + P Energy for endergonic rxns ATP is a renewable energy source for cells When energy is released in exergonic rxns, it can be used to make more ATP 10!

11 Enzymes Speed Up the Cell s Chemical Rxns Enzymes are proteins that speed up cellular metabolism (biological catalysts) They are not used up in the process 11!

12 The Catalytic Cycle of an Enzyme 1 Enzyme available with empty active site Active site Substrate (sucrose) 2 Substrate binds to enzyme with induced fit Glucose Enzyme (sucrase) Fructose 4 Products are released H 2 O 3 Substrate is converted to products 12!

13 Specific Enzymes Catalyze Specific Rxns Enzymes 3-D shape determines its specificity The specific reactant(s) that it acts on is substrate The substrate fits into the enzymes active site Enzymes are specific b/c the shape of the active site must fit the shape the substrate 13!

14 Temperature affects enzyme activity Most enzymes have an optimal temperature, at which their activity is greatest Figure !

15 For optimum activity, enzymes require specific conditions Temperature - human enzymes work best at 35-40ºC, ~ body temp. High temps denature enzymes Cold temps slow their activity ph - optimum enzyme activity is near neutral Stomach enzymes work best at low ph 15!

16 Question According to the graph, at what temperature do you predict the bacterial enzyme becomes denatured? A. 55 C B. 66 C C. 73 C D. 78 C 16!

17 How Do You Tell An Enzyme to STOP Making Product? TWO ways:

18 Enzyme Inhibitors You May Know 1. Roundup- Inhibits an enzyme in weed (plant) cells. 2. Aspirin- Blocks an enzyme that cells use to produce pain-related molecules.

19 Mastering Concepts What functions do enzymes perform in living cells?

20 Membranes A Fluid Mosaic Membranes are composed of A phospholipid bilayer Embedded and attached proteins Commonly described as a fluid mosaic The plasma membrane of an animal cell 20!

21 Fibers of extracellular matrix (ECM) Enzymatic activity Phospholipid Cholesterol CYTOPLASM Cell-cell recognition Receptor Signaling molecule Transport ATP Intercellular junctions Glycoprotein Attachment to the cytoskeleton and extracellular matrix (ECM) Signal transduction Microfilaments of cytoskeleton CYTOPLASM Some functions of membrane proteins 21!

22 Membranes are selectively permeable Not all molecules can cross the cell membrane Small non-polar molecules (CO 2 and O 2 ) diffuse freely Polar molecules (H 2 O, glucose and other sugars), ions, and large molecules can not diffuse across membrane Transport proteins allow molecules that can not diffuse to enter and leave a cell 22!

23 Passive Transport = Diffusion Across a Membrane (no energy added) Diffusion - tendency of particles to spread out evenly in an available space Particles move from high to low concentration They move down their concentration gradient Eventually, particles evenly disperse (equilibrium) High concentration areas Solute evenly dispersed Figure !

24 Osmosis the Diffusion of Water Figure 4.14

25 Red Blood Cells are Affected by Tonicity Figure 4.15

26 Transport Proteins Facilitate Diffusion Across Membranes Polar or charged substances do not cross membranes easily They require the help of specific transport proteins Process called facilitated diffusion, a type of passive transport that does not require energy Rapid diffusion of water into/out of cells made possible by Protein channel called an aquaporin 26!

27 Solute molecule Transport protein Transport protein providing a channel for diffusion of a specific solute across a membrane 27!

28 Cells Expend Energy in Active Transport Cells have a mechanism for moving a solute against its concentration gradient Requires use of energy from ATP Shape of the membrane protein altered by phosphorylation using ATP 28!

29 Active Transport 29!

30 Mastering Concepts Distinguish between simple diffusion, facilitated diffusion, and active transport.

31 Endocytosis and Exocytosis Transport Large Molecules Across Membranes Exocytosis is used to export lg. molecules, such as proteins or polysaccharides Endocytosis is used to import substances useful to cell s life In both cases, material to be transported is packaged within a vesicle that fuses with the membrane 31!

32 Exocytosis and Endocytosis 32!