Ch. 4 Cellular Processes

1. Ch. 4 Cellular Processes Ms. Whipple Brethren Christian High School

2. 4A-1 Energy Relationships • Organism’s depend on many conditions in their environment and the most important of these is a constant supply of energy. An Organism’s primary need is ENERGY!! • Cells use and reuse different substances (amino acids, sugars, lipids, etc.) but energy must be constantly supplied as every time it is used, some is lost and becomes unusable (2nd law of thermodynamics) • Cells store energy in the bonds of large stable organic molecules (starch, fat, sugar) and need energy to make these bonds.

3. 4A-1 Energy Relationships • Organisms are in constant battle to maintain a supply of energy because it is difficult to store, is used and never reused, and escapes constantly as entropy (2nd law of thermodynamics)

4. 4A-1 Energy Relationships • Obtaining energy!! There are two classifications of organisms based on how they obtain energy. • Autotrophs (Producer): Organisms that make their own food by photosynthesis. Plants, Algae, and some other organisms capture light energy to produce their own food. (Photosynthesis). The process of photosynthesis uses CO2 and H2O in the presence of sunlight to make Glucose and O2. Equation for Photosynthesis: 6CO2 + 6H2O C6H12O6+ 6O2 • Heterotrophs (Consumer and Decomposers): Organisms that depend on other organisms for their energy. Humans, animals, fungi and bacteria must rely on the energy of other organisms for their food. To obtain energy, Glucose is broken down into CO2 and H2O releasing the energy to make ATP (cellular energy). Equation for Cellular Respiration: C6H12O6+ 6O2 6CO2+ 6H2O Reactants Products Reactants Products

5. 4A-1 Energy Relationships Heterotroph (Koala) Autotroph (tree)

6. 4A-1 Energy Relationships • The Food Chain: linear consequence of links in a food web (non-linear web of food relationships between species) starting from producers and ends at decomposers.

7. 4A-1 Energy Relationships • ATP: The Energy Currency of Cells • To use energy, it must be in an easily accessible form. Many molecules that store energy, like starch and lipids, have too much energy to be used at one time (and that could potentially be destructive!). So, the energy from these molecules must be converted into smaller units. In all know organisms this small unit is the molecule ATP (Adenosine Triphosphate).

8. 4A-1 Energy Relationships • Structure of ATP • An ATP molecule consists of Ribose (5-carbon sugar backbone), Adenine (one of the bases from DNA), and a chain of three Phosphate Groups.

9. 4A-1 Energy Relationships • Using ATP: ATP stores energy in the bonds between the phosphate groups. When these bonds are broken a small unit of energy is released and can be immediately used for a cellular function. • In most reactions, the third phosphate group is broken off to release energy. This leaves a molecule of ADP (Adenosine Diphospate), a free phosphate group, and energy. ATP ADP + P + Energy!

10. 4A-1 Energy Relationships • Once ATP has been converted to ADP and the energy used, an enzyme takes it and combines it with a phosphate group and energy to make ATP again. In this way it is a reusable energy source. ADP + P + Energy ATP • This cycle of breaking down ATP to use energy and then rebuilding it with energy is how we stay alive. It is very much like a prepaid debit card, once you use the money from the card (break the bond) you must put more money in to use it again (reform the bond).

11. 4A-1 Energy Relationships

12. 4A-3 Cellular Respiration • Respiration is commonly thought to be breathing, but breathing is really only the first step in respiration (obtaining oxygen). • Cellular Respiration: breaking down of food substances into usable cellular energy in the form of ATP. This occurs in the mitochondria. • There are 2 types of cellular respiration: Aerobic (requiring oxygen) and Anaerobic (not requiring oxygen).

13. 4A-3 Cellular Respiration • Aerobic Respiration: Requires Oxygen!! Most cells require oxygen to break down sugar and release heat in much the same way that a match needs oxygen to light and will go out if deprived air. • In aerobic respiration, cells use a series of enzymes with a little activation energy to break glucose into energy, CO2 and H2O. Therefore, it can be seen as the opposite of Photosynthesis (which uses CO2 and water to make glucose). • Chemical Equation of Aerobic Respiration + ATP (energy)

14. 4A-3 Cellular Respiration • The Process of Aerobic Respiration • Every process of cellular respiration begins with Glycolysis in the cytoplasm.It does not require oxygen but it is involved in both aerobic or anaerobic pathways. • Glycolysis (Stage I): Takes place in the cytoplasm. converts glucose C6H12O6into pyruvate, CH3COCO+ . To start this process, 2 ATP are put into the reaction (energy investment). In the second stage, the free energy release forms 4 ATPs (net gain: 4 – 2 = 2 ATP) and 2 NADH • Net Gain: • 2 Pyruvate • 2 H2O • 2 AtP • 2 NADH + 2H+

16. 4A-3 Cellular Respiration • Aerobic Respiration (after glycolysis): Divided into 2 phases: the Citric Acid Cycle (Kreb’s Cycle) and the Hydrogen and Electron transport chain. • Citric Acid Cycle (or Kreb’s Cycle) (Stage II): Occurs in the matrix of the mitochondria. An enzyme breaks the pyruvic acid from glycolysis into acetyl coA, C, Hydrogen ions, ATP, and electrons. The C is releases as waste out of the cell and the hydrogen and electrons move on the next phase. For every 1 molecule of glucose, the Citric Acid Cycle turns twice! • NET GAIN: • 8 NADH • 2 FADH2 • 2 ATP • 6 CO2 (waste!)

18. 4A-3 Cellular Respiration • Hydrogen and Electron Transport Chain(Stage III): Occurs along the membrane of the inner mitochondrial membrane (cristae). The energy from NADH and FADH2 are used to pump H+ into the outer compartment of the mitochondria. This creates a chemiosmotic gradient which is used to produce ATP. ATP is generated as H+ moves down its concentration gradient through a special enzyme called ATP synthase. • NET GAIN: • 32 ATP • H2O

19. 4A-3 Cellular Respiration

20. 4A-3 Cellular Respiration • So, altogether the output of aerobic respiration: • Glycolysis: 2 ATP • Citric Acid Cycle: 2 ATP • Hydrogen and Electron Transport Chain: 32 ATP • Total: 36 ATP from 1 molecule of glucose

21. 4A-3 Cellular Respiration • The Process of Anaerobic Respiration: • Some organisms live in environments without oxygen and even our bodies are sometimes put into a anaerobic situation (during exercise when the blood cannot carry oxygen to the muscles fast enough), so we must use anaerobic respiration. • Fermentation: The process of breaking down food without oxygen. This process does not produce as much usable energy (ATP) but is used by many organisms. There are 2 different pathways: Alcoholic Fermentation and Lactic Acid Fermentation.

22. 4A-3 Cellular Respiration • Alcoholic Fermentation: The process is carried out by many bacteria and yeast. The yeast that are used in making bread rise use this process. During this process, the pyruvic acid from glycolysis is changed into ethyl alcohol. The net gain of this process is 2 ATP. Fizzy bubbles and bread rising!!

23. 4A-3 Cellular Respiration • Lactic Acid Fermentation: This process is carried out by many bacteria, including the bacteria found in cottage cheese and yogurt. This is also the process animals cells will use if necessary. During this process the pyruvic acid from glycolysis is converted into lactic acid, which can cause cramping in muscle cells. The net gain from this process is 2 ATP.

24. 4A-2 Photosynthesis • All energy for living organisms comes from the sun. However, to be usable this solar energy must be converted into chemical energy. The process of converting light energy into chemical energy is called Photosynthesis, carried out by green plants and algae. • Photosynthesis is important to life because it provides glucose but also, it produces oxygen. This oxygen is needed for many organisms (including us!) to survive.

25. 4A-2 Photosynthesis • Equation of Photosynthesis: 12 H2O + 6CO2 + Light Energy C6H12O6 + 6H2O + 6O2 • Chlorophyll: A green pigment which is the primary catalyst for photosynthesis. It is found in the membranes of the thylakoids in the chloroplasts.. CHLOROPHYLL

26. 4A-2 Photosynthesis • There are a few different types of chlorophyll. Each designed to absorb and reflect different colors. When an object reflects a color, it is absorbing all other colors. For example, a red sweater is reflecting red and absorbing all the other colors. White light has wavelengths of all the colors of light.

27. 4A-2 Photosynthesis • Chlorophyll a: a blue-green pigment that reflects blues and greens and absorbs violets and reds. • Chlorophyll b: a yellow green that reflects yellows and greens while absorbing blues and reds. • By having different types of chlorophyll the plant is able to successfully absorb more colors from the spectrum.

28. 4A-2 Photosynthesis • The Process of Photosynthesis: • Photosynthesis takes place on the thylakoid membranes in clusters of chlorophyll molecules. • There are 2 separate and distinct phases of photosynthesis: The Light Dependent Phase and the Light Independent Phase.

29. 4A-2 Photosynthesis • Light Dependent Phase • An Electron Transport Chain!! Occurs in the grana (stacks of thylakoids) on the membrane of the thylakoids. There are 4 main protein complexes assisting in this process: : Photosystem II (PSII), Cytochrome b6f complex, Photosystem I (PSI), and ATP synthase. • A Photon (light energy) is absorbed by PSII and the energy is used to excite an electron and split a molecule of water. This releases 2H+ (protons) into the inside of the thylakoid (lumen) and Oxygen is released as waste. • The energized electron leave PSII and go to Cytochrome b6f complex which pumps more H+ into the lumen, creating a chemiosmotic gradient (more H+ inside the thylakoid than outside) • The depleted electron flows to PSI. It is re-energized with another photon (light energy) and that energy is used to convert NADP+ to NADPH, a energy-carrying molecule. • ATP Synthase makes ATP from H+ ions rushing back through the membrane into the stroma. • Net Reaction of Light Dependent Phase: 2H2O + 2NADP++ 3ADP + 3Pi → O2+ 2NADPH + 3ATP

30. 4A-2 Photosynthesis

31. 4A-2 Photosynthesis • Light Independent Phase (or dark phase) • Also called the Dark Phase, Calvin Cycle, or Carbon Fixation Cycle. • Occurs in the stroma, the fluid-filled area of a chloroplast outside of the thylakoid membranes: • The enzyme RuBisCo takes a molecule of CO2 and binds it to a 5-carbon sugar called ribulosebiphosphate (RuBP). • The energy from ATP and NADPH (from the light dependent reactions) are used to convert RuBP into a 3-carbon sugar called phosphoglyceraldehyde (PGAL) • Some of the PGAL molecules are then connected to make glucose while others form more RuBP to continue the cycle. Net Equation for Light Independent Reaction: 3CO2+6NADPH+5H2O+9ATP → glyceraldehyde-3-phosphate(G3P/PGAL)+2 H++6NADP++9ADP+8 Pi (Pi = inorganic phosphate)

32. 4A-2 Photosynthesis

33. 4A-2 Photosynthesis • PUTTING IT ALL TOGETHER!!!

34. 4A-2 Photosynthesis • Proper Conditions for Photosynthesis: • For Photosynthesis to be successful it must have the right conditions: • Right Temperature: Proper temps vary from plant to plant but for most it is room temperature (21. When it is very hot or freezing most plants shut down photosynthesis as the function of chlorophyll is temp. dependent. • Adequate Light: Plants must receive the proper amount of wavelengths and intensity of light. If plants cannot absorb enough energy, their chlorophyll a molecules will not become sufficiently energized. • Sufficient CO2: Plant cells must be able to absorb enough CO2 but this can be a problem as it makes up only .03% of the atmosphere. • Adequate Water: Plants must have enough water absorbed from the roots to support photosynthesis.

35. 4A-2 Photosynthesis • Photorespiration Problem: • In all plants CO2 is fixed by the enzymeRubisco. It catalyzes that reaction where CO2 combines with RuBP leading to two molecules of 3-phosphoglyceratewhich later become PGAL. • Unfortunately, instead of CO2, Rubiscocan also fix oxygen to RuBP resulting in one molecule each of 3-phosphoglycerate and 2-phosphoglycolate. Phosphoglycolate has no known metabolic purpose and in higher concentrations it is toxic for the plant!!! • This Phosphoglycolate has to be processed (gotten rid of) by a metabolic pathway called photorespiration. Photorespiration is not only energy demanding, but furthermore leads to a net loss of CO2. Thus the efficiency of photosynthesis can be decreased by 40% under unfavorable conditions including high temperatures and dryness. • The unfavorable reaction of Rubiscowith O2 is thought to be a relic of the evolutionary history of this enzyme, which is thought to have evolved more than 3 billion years ago when atmospheric CO2 concentrations were high and oxygen concentrations low. • Plants in harsh environments developed different ways to cope with this problem.

36. 4A-2 Photosynthesis • The CAM Pathway • Plants like Cacti and Pineapples use the CAM pathway of photosynthesis. They open their stomata during to night and keep them closed all day. As the plants take in CO2 at night, they bind the CO2 to special organic molecules. These molecules release the CO2 during the day to keep Photosynthesis running.

37. 4A-2 Photosynthesis • The C4 Pathway. • Plants like corn and crabgrass use the C4 pathway. They only partially close their stomata during the hottest part of the day. They have special enzymes to fix CO2 in cells closer to the surface of the leaf. This CO2 is then moved to lower bundle sheath cells within the leaf, away from O2.