1 Chapter 8 Cellular Energy 8.1 How Organisms Obtain Energy

2 Transformation of Energy  Energy is the ability to do work. 8.1 How Organisms Obtain Energy Cellular Energy  Thermodynamics is the study of the flow and transformation of energy in the universe. Chapter 8

3 Laws of Thermodynamics  First law—energy can be converted from one form to another, but it cannot be created nor destroyed. 8.1 How Organisms Obtain Energy Cellular Energy  Second law—energy cannot be converted without the loss of usable energy. Chapter 8

4 Autotrophs and Heterotrophs  Autotrophs are organisms that make their own food. 8.1 How Organisms Obtain Energy Cellular Energy  Heterotrophs are organisms that need to ingest food to obtain energy. Chapter 8

5 Metabolism  All of the chemical reactions in a cell 8.1 How Organisms Obtain Energy Cellular Energy  Photosynthesis—light energy from the Sun is converted to chemical energy for use by the cell  Cellular respiration—organic molecules are broken down to release energy for use by the cell Chapter 8

6 Cells need energy for:  Making new molecules  Maintaining homeostasis  Active transport Endocytosis Exocytosis Going against the concentration gradient  Movement Cilia and flagella Muscle contraction including cardiac muscle  Cell division

7 ATP stores energy in chemical bonds  A= adenosine  T= tri  P= phosphate

8 ATP and ADP recycle

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10 ATP is like currency  Cells can only use the ATP for energy even though they store energy as fats, carbohydrates or proteins  Carbohydrates, fats and proteins must be changed to ATP before they can be used by the cell (process of cellular respiration)  You can only use coins in the soda machine even though you may have a $5 bill in your pocket

11 How cells tap into the energy stored in ATP  Many enzymes have a site where ATP fits in like a battery to provide the energy for that enzyme to work

12 Chapter 8 Cellular Energy 8.2 Photosynthesis

13 Photosynthesis: The Big Picture  Plants change solar energy (sunlight) into ATP then into glucose (chemical energy)  Two step process

14 Overall reaction of photosynthesis

15 Role of Chloroplasts  Chlorophyll is the pigment found in the chloroplasts of plants and algae  Chloroplast is the location for photosynthesis

16 Chloroplast Structure  Thylakoid membrane is the site for photosynthesis

17 Chlorophyll  Plants have two types of chlorophyll Chlorophyll a is yellow green Chlorophyll b is blue green  We see plants as green because green is reflected not absorbed by the chlorophyll  Plants also contain red, orange and yellow pigments  When leaves “turn colors” in the fall it is because chlorophyll productions ceases and the other colors are exposed

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20 Photosynthesis: A Two Step Process  Step One: Light Dependent Reactions  Step Two: Light Independent Reactions (previously called the Dark Reactions or the Calvin Cycle)

21 Light Dependent Reactions of Photosynthesis  Light strikes a chlorophyll molecule and excites an electron  Electron gets passed to a series of proteins in an electron transport chain and an ATP gets made  Electron goes to a second electron transport chain and another energy molecule (NADPH) gets made

22 Light Dependent Reactions of Photosynthesis  Photolysis must happen to “fill in the hole” left by the electron that was excited  Photolysis is the splitting of water; the hydrogen goes to fill the electron’s place and the oxygen is what we breathe (O 2 )

23 Light Dependent Reactions of Photosynthesis  Start with sunlight and get ATP and NADPH Energy molecules used for Step Two  Start with water and get oxygen

24 Light Independent Reactions of Photosynthesis Light dependent Light independent

25 Light Independent Reactions of Photosynthesis  ATP and NADPH from the light dependent reaction provide the energy to convert CO 2 to C 6 H 12 O 6 (glucose)  Uses many enzymes in a cycle to produce glucose Cycles are important in organisms because they allow for constant production

26 Light Independent Reactions of Photosynthesis

27 Light Independent Reactions of Photosynthesis  Each “turn” of the cycle produces ½ of a glucose  ATP and NADPH are used to produce this glucose  No sunlight is needed, reactions happen independent of light

28 Alternative Pathways  C 4 Plants: fix CO 2 into four-carbon compounds keep stomata closed during hot days (less transpiration water loss) Sugar cane and corn

29 Alternative Pathways  CAM plants: conserve water by allowing CO 2 to enter only at night (stomata closed during day to conserve water)  Examples: pineapple, cacti, orchids and other desert or salt march plants

30 Chapter 8 Cellular Energy 8.3 Cellular Respiration

31 Cellular Respiration  Process of breaking down food to produce ATP  ALL living things do cellular respiration, even: Plants Bacteria  Eukaryotes in the mitochondria  Prokaryotes in the cytoplasm

32 Cellular Respiration Overall reaction C 6 H 12 O 6 + O 2 CO 2 + H 2 O + energy

33 Cellular Respiration  Three Stage Process 1.Glycolysis: anaerobic 2.Citric Acid Cycle: aerobic 3.Electron Transport Chain: aerobic

34 Cellular Respiration Overview

35 Glycolysis  Happens in the cytoplasm  Need to use two ATP before can get ATP out of the process  One glucose is split and converted into two pyruvate yields four ATP (two net ATP)

36 Citric Acid Cycle or Krebs Cycle  Happens in the mitochondrial matrix  CO 2 produced  Per turn of the cycle yields: 1 ATP 3 NAPH 1FADH 2

37 Electron Transport Chain

38 Electron Transport Chain  Located within the inner mitochondrial membrane  Converts NADH and FADH 2 into ATP  Energized electrons are passed along a series of proteins Some energy is converted directly into ATP Other energy causes H + ions to be forced out of the inner mitochondrial matrix

39 Electron Transport Chain cont.  The force of H + ions back into the mitochondrial matrix through the enzyme ATP synthase provides the energy for ATP synthesis  Oxygen is the final electron acceptor Without oxygen the transport chain would shut down like a traffic jam Traffic (electrons) would back up and shut down the Krebs Cycle as well

40 Electron Transport Chain cont.  For every NADH get 3 ATP  For every FADH 2 get 2 ATP  Overall get a net of 32 ATP from one molecule of glucose  Balanced equation: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + 32 ATP

41 Fermentation  Occurs when O 2 is not present, no aerobic respiration, no Krebs Cycle, no Electron Transport Chain  Allows the continuation of glycolysis by the removal of pyruvate  Some organisms in anaerobic environments produce energy by fermentation all the time

42 Fermentation: Two Types  Alcoholic Yeast Produce CO 2, ethyl alcohol and 2 ATP from pyruvate Important in bread and alcoholic beverage industries  Lactic Acid Animal muscle cells, some bacteria and some plants Produce lactic acid and 2 ATP from pyruvate Get sore, burning muscles Liver converts lactic acid back to pyruvate when O 2 is present

43 Comparing Photosynthesis and Cellular Respiration  Both use electron transport chains  Both use cycles of chemical reactions  Both use electron carrier proteins  Both use concentration gradient of H + ions

44 Comparing Photosynthesis and Cellular Respiration  Photosynthesis Food accumulated Solar energy stored in glucose CO 2 taken in, O 2 given off Occurs only in presence of chlorophyll with sunlight  Cellular Respiration Food broken down Glucose energy released O 2 taken in, CO 2 given off Occurs in all living things all the time