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Chapter 9 Energy in a Cell ATP

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1 Chapter 9 Energy in a Cell ATP

2 9.1 – The Need for Energy (p ) Energy is essential to life. Energy is essential to life. Organisms are endergonic systems. Organisms are endergonic systems. What do we need “E” for? What do we need “E” for?  Active Transport  Cell Division  Transport  Synthesis (proteins)  others

3 ATP is the universal currency of energy exchange in biological systems. ATP is the universal currency of energy exchange in biological systems. No matter what form of energy a cell uses as its primary source, the energy is ultimately transformed and conserved as ATP. No matter what form of energy a cell uses as its primary source, the energy is ultimately transformed and conserved as ATP. adenosine monophosphate (AMP) nucleotide two phosphate groups pyrophosphate bonds (~P). These two bonds are energy rich in the sense that their hydrolysis (breakage which releases water) yields a great deal more energy than a covalent bond of another molecule.

4 The ATP reaction is commonly written as: The ATP reaction is commonly written as: ADP + Pi + energy  ATP The forming of ADP into ATP The forming of ADP into ATP requires energy (endothermic) – 8 kcal/mole requires energy (endothermic) – 8 kcal/mole is pH dependent. is pH dependent. Note: Forming ADP is like making a bank deposit or coiling a spring for each phosphate bond. (see figure 9.2 on p. 223)

5 The Calorie Kcal – kilocalorie Kcal – kilocalorie equivalent to 1000 calories. equivalent to 1000 calories. When we say that a cup of milk has 120 calories we really mean 300 kilocalories or calories. When we say that a cup of milk has 120 calories we really mean 300 kilocalories or calories. Even though we use the word calorie it is, by definition, kilocalorie. Even though we use the word calorie it is, by definition, kilocalorie.

6 The Mole ABOUT THE MOLE: Analogous to a dozen, it is a ”count” of molecules used in chemistry and biochemistry. 1 mol = x molecules 0.5 mol = x molecules 2.0 mol – x molecules or x molecules

7 9.2 Photosynthesis: Trapping the Sun’s Energy p We’ve seen in our past learning that the cell uses energy during ACTIVE TRANSPORT. Where does this energy come from? We’ve seen in our past learning that the cell uses energy during ACTIVE TRANSPORT. Where does this energy come from?

8 RECALL FROM EARLIER GRADES All animals are heterotrophs - require food sources of energy. i.e. trophic levels in a food chain

9 We do not make our own food for energy like plants, algae and some bacteria (autotrophs). This is summarized by the carbon- oxygen cycle below: We do not make our own food for energy like plants, algae and some bacteria (autotrophs). This is summarized by the carbon- oxygen cycle below:

10 Photosynthesis: The Energy Maker Autotrophs under go PHOTOSYNTHESIS to produce sugars (starches made up of glucose molecules)—we say the sun’s energy is stored in a chemical bond. Autotrophs under go PHOTOSYNTHESIS to produce sugars (starches made up of glucose molecules)—we say the sun’s energy is stored in a chemical bond. Recall: Recall: UV energy + CO 2 + 6H 2 O  C 6 H 12 O O 2

11 In actuality, this reaction is elegant, but is not simple. In actuality, this reaction is elegant, but is not simple. MANY reactions occur inside the chloroplast’s grana membrane. MANY reactions occur inside the chloroplast’s grana membrane. The chlorophyll in chloroplasts is one pigment (a green one, there are others) that absorbs sun energy (all colours except green) which excite electrons and cause a phosphate to attach to ADP molecules. The chlorophyll in chloroplasts is one pigment (a green one, there are others) that absorbs sun energy (all colours except green) which excite electrons and cause a phosphate to attach to ADP molecules.

12 LIGHT DEPENDENT- REACTIONS Energized electrons provide energy that: Energized electrons provide energy that: Forms ATP. Forms ATP. Releases oxygen molecules (from the splitting of H 2 O) Releases oxygen molecules (from the splitting of H 2 O) See Fig. 9.5 p. 227 Fig. 9.6 p. 228 Fig. 9.6 p. 228

13 Ligh t Independent Reactions/Dark Reactions At the same time (and more so at night when there is no sun) the Calvin cycle takes place in the stroma of the chloroplast. At the same time (and more so at night when there is no sun) the Calvin cycle takes place in the stroma of the chloroplast. Powered by ATP Powered by ATP from photosynthesis

14 Carbon dioxide gas (CO 2 ) is taken in and used to form sugars (CH 2 O is short hand to represent many different types of sugar molecules, most importantly glucose). Carbon dioxide gas (CO 2 ) is taken in and used to form sugars (CH 2 O is short hand to represent many different types of sugar molecules, most importantly glucose). These are stored as starch granules in chloroplasts. These are stored as starch granules in chloroplasts. They are also transported to other cells and accumulate in roots. They are also transported to other cells and accumulate in roots. See Fig. 9.7 p. 229 See Fig. 9.7 p. 229

15 The new summary of photosynthesis: Light dependent reactions: Light dependent reactions: 12H 2 O + 12NADP + 18ADP → 6O NADPH + 18ATP Light Independent reactions (*Calvin cycle) Light Independent reactions (*Calvin cycle) 6CO NADPH + 18ATP→C 6 H 12 O 6 +12NADP+18ADP+6H 2 O Can you see how we get the overall Ps equation? Can you see how we get the overall Ps equation? The whole point of these reactions is to make a safe, energy rich molecule, glucose. The whole point of these reactions is to make a safe, energy rich molecule, glucose.

16 9.3 Getting Energy to Make ATP Cellular Respiration When we consume the sugars from plants, (producers) or animals that have eaten plants (primary consumers), energy from the sugar bonds is released. When we consume the sugars from plants, (producers) or animals that have eaten plants (primary consumers), energy from the sugar bonds is released. The release of this energy is called respiration. The release of this energy is called respiration.Recall: C 6 H 12 O O 2  6 CO H 2 O + Energy (ATP)

17 Again, the reaction is elegant but far from simple! Again, the reaction is elegant but far from simple! When animals and plants consume energy molecules like starch and glucose, many reactions occur. When animals and plants consume energy molecules like starch and glucose, many reactions occur. Glycolysis (anaerobic) Glycolysis (anaerobic) Citric Acid Cycle (aerobic) Citric Acid Cycle (aerobic) Electron Transport Chain Electron Transport Chain -also aerobic The last two occur The last two occur inside the mitochondrion.

18 Glycolysis Glycolysis is the only metabolic pathway shared by ALL organisms. Glycolysis is the only metabolic pathway shared by ALL organisms. Occurs in the cytoplasm. Occurs in the cytoplasm. i.e. not in an organelle i.e. not in an organelle

19 Glycolysis (cont’d) A process whereby glucose molecules are split in half (makes a 3-C compound called pyruvate) in a series of steps. A process whereby glucose molecules are split in half (makes a 3-C compound called pyruvate) in a series of steps. Glycolysis releases a 2 – ATP molecules per glucose molecule that are used to drive other reactions AND Glycolysis releases a 2 – ATP molecules per glucose molecule that are used to drive other reactions AND This process does not require O 2 This process does not require O 2 Anerobic Anerobic See Fig. 9.8 p. 232

20 Aerobic vs. Anaerobic From here, pathways diverge in different organisms and in different situations—oxygen poor (anaerobic) and oxygen rich (aerobic). From here, pathways diverge in different organisms and in different situations—oxygen poor (anaerobic) and oxygen rich (aerobic). More about that later. More about that later.

21 BUT more ATP is made inside the mitochondrion in two separate pathways: BUT more ATP is made inside the mitochondrion in two separate pathways: The Citric Acid Cycle, CAC (KREBS CYCLE, KC) The Citric Acid Cycle, CAC (KREBS CYCLE, KC) ELECTRON TRANSPORT CHAIN (ETC) ELECTRON TRANSPORT CHAIN (ETC) CAC releases 1 ATP molecule CAC releases 1 ATP molecule ETC releases 30 ATP molecules! ETC releases 30 ATP molecules! These reactions drive far more chemical reactions in our tissues because of it. These reactions drive far more chemical reactions in our tissues because of it.

22 Citric Acid Cycle (CAC) The CAC occurs inside the mitochondrial matrix. The CAC occurs inside the mitochondrial matrix. It is called a cycle, because one of its end- products is recycled in the cycle. It is called a cycle, because one of its end- products is recycled in the cycle. Named because it forms citric acid Named because it forms citric acid an important intermediate molecule. an important intermediate molecule.

23 Citric Acid Cycle (cont’d) The main outcome is the generation of a variety of energy intermediate molecules, not just ATP. The main outcome is the generation of a variety of energy intermediate molecules, not just ATP. GTP GTP NADH NADH FADH 2. FADH 2. This cycle also releases 3 CO 2 molecules per pyruvate (3-C). This cycle also releases 3 CO 2 molecules per pyruvate (3-C). See Fig p. 233 See Fig p. 233

24 A diagram shows the numbers of energy molecules generated: A diagram shows the numbers of energy molecules generated: animation

25 The Electron Transport Chain (ETC) From the Krebs cycle (Citric Acid cycle) inside the mitochondrion, the ETC occurs inside the mitochondrial membrane. From the Krebs cycle (Citric Acid cycle) inside the mitochondrion, the ETC occurs inside the mitochondrial membrane. It causes a cascade of energy release by using the other energy molecules of NADH, FADH2 to cash in and make more ATP. It causes a cascade of energy release by using the other energy molecules of NADH, FADH2 to cash in and make more ATP. See Fig p. 234 See Fig p. 234

26 The specialized molecules that do this are called CYTOCHROMES and they pass excited electrons from one cytochrome to another stepwise—this releases even more ATP—30 more ATP!—in a controlled manner. The specialized molecules that do this are called CYTOCHROMES and they pass excited electrons from one cytochrome to another stepwise—this releases even more ATP—30 more ATP!—in a controlled manner. This is where oxygen is consumed, and water formed. This is where oxygen is consumed, and water formed. TOTAL ATP from 1 glucose molecule: TOTAL ATP from 1 glucose molecule: - 2 gly - 2 (Act T)+ 2 CAC + 30 ETC = 32 ATP

27 The schematic below shows how electrons transferred from the NADH in Krebs are transferred in a cascade of reactions in the ETC—note the need for flavin M (part of the group of riboflavins, or B vitamins—B2) and the role of iron ions (Fe). The schematic below shows how electrons transferred from the NADH in Krebs are transferred in a cascade of reactions in the ETC—note the need for flavin M (part of the group of riboflavins, or B vitamins—B2) and the role of iron ions (Fe). This releases a LOT of ATP molecules. This releases a LOT of ATP molecules.

28 Cellular Respiration Schematic

29 In summary

30 In summary: SO, back to our original reaction—the important component is the ENERGY: SO, back to our original reaction—the important component is the ENERGY: C 6 H 12 O 6 + 6O2  6CO 2 + 6H 2 O + 32ATP We now know We now know where oxygen is consumed, where oxygen is consumed, how CO 2 is generated, how CO 2 is generated, where the H 2 O comes from where the H 2 O comes from and how many energy molecules are made. and how many energy molecules are made.

31 Anaerobic Respiration If no oxygen continues to be present or, in some organisms like yeast, where it is not used, fermentation occurs. If no oxygen continues to be present or, in some organisms like yeast, where it is not used, fermentation occurs. This is also known as anaerobic respiration. This is also known as anaerobic respiration. uses the 3-C molecules (pyruvate) and makes lactic acid in our muscles or in yogurt) or ethanol (as in brewing). uses the 3-C molecules (pyruvate) and makes lactic acid in our muscles or in yogurt) or ethanol (as in brewing).

32 Anaerobic Respiration (cont’d) Only another 2 ATP molecules are made Only another 2 ATP molecules are made This occurs with some fungi, and with Lactobacillus acidophilus in yogurt, and in yeasts. This occurs with some fungi, and with Lactobacillus acidophilus in yogurt, and in yeasts. This is the basis of cheese, yogurt, buttermilk, root beer (real root beer), breads, wines, spirits. This is the basis of cheese, yogurt, buttermilk, root beer (real root beer), breads, wines, spirits.

33 Anaerobic Exercise In vigorous exercise, lactic acid builds up in our muscles when we’ve exhausted the oxygen supply in our haemoglobin In vigorous exercise, lactic acid builds up in our muscles when we’ve exhausted the oxygen supply in our haemoglobin i.e. We produce more lactic acid than our cells can remove and they begin to seize up creating pain. i.e. We produce more lactic acid than our cells can remove and they begin to seize up creating pain. Athletes can increase their tolerance for lactic acid. Athletes can increase their tolerance for lactic acid.

34 Aerobic Respiration AEROBIC RESPIRATION occurs in our mitochondria AEROBIC RESPIRATION occurs in our mitochondria these pathways occur when oxygen is required (as in us) and is present in sufficient amounts. these pathways occur when oxygen is required (as in us) and is present in sufficient amounts. Longer duration of exercise Longer duration of exercise For these cycles to occur, active transport of pyruvate from glycolysis is needed – this uses up the 2 ATP that were made. For these cycles to occur, active transport of pyruvate from glycolysis is needed – this uses up the 2 ATP that were made.

35 Metabolism METABOLISM refers to two contrasting cellular activities: METABOLISM refers to two contrasting cellular activities: the total biochemical reactions required for energy making reactions called CATABOLISM (includes breaking down foods to store energy – ATP - in our tissues) the total biochemical reactions required for energy making reactions called CATABOLISM (includes breaking down foods to store energy – ATP - in our tissues) and and the use of energy to synthesize cell material from small molecules in the environment, called ANABOLISM (energy consuming, using ATP to release energy). the use of energy to synthesize cell material from small molecules in the environment, called ANABOLISM (energy consuming, using ATP to release energy).

36 Catabolic Reactions Produce energy in the chemical bonds of a molecule called ATP (adenosine triphosphate). Produce energy in the chemical bonds of a molecule called ATP (adenosine triphosphate). glycolysis glycolysis CAC CAC ETC ETC lead to end products, which are "waste products" like water and CO2 lead to end products, which are "waste products" like water and CO2 most important—they generate ATP which is later used in anabolic reactions to build cell material from nutrients in the environment, like muscle tissue. most important—they generate ATP which is later used in anabolic reactions to build cell material from nutrients in the environment, like muscle tissue.

37 Anabolic Pathways Lead to release of the energy to drive other reactions. Lead to release of the energy to drive other reactions. These reactions make important molecules like proteins for our muscles, hair, nails, lipids for our fatty tissues, and so on. These reactions make important molecules like proteins for our muscles, hair, nails, lipids for our fatty tissues, and so on. When energy is required during anabolism, it may be spent as the breaking of a high energy bond of ATP which has a value of about 8 kcal/mol of ATP molecules. This is like a withdrawal from your account. When energy is required during anabolism, it may be spent as the breaking of a high energy bond of ATP which has a value of about 8 kcal/mol of ATP molecules. This is like a withdrawal from your account.

38 Role of Water

39 Breaking the ATP to make ADP releases 8 kcal/mol. The ATP reaction is commonly written as: Breaking the ATP to make ADP releases 8 kcal/mol. The ATP reaction is commonly written as: ATP  ADP + Pi + 8 kcal/mol

40 The diagram showing the relationships between catabolism and anabolism is not to be memorized, but to help you understand the connections: The diagram showing the relationships between catabolism and anabolism is not to be memorized, but to help you understand the connections:

41 IMP: During catabolism, energy is changed from one form to another, but such energy transformations are never completely efficient, i.e., some energy is lost in the form of heat. This forms part of our body heat. IMP: During catabolism, energy is changed from one form to another, but such energy transformations are never completely efficient, i.e., some energy is lost in the form of heat. This forms part of our body heat. In both catabolism and anabolism, energy is formed stepwise and broken down stepwise in a number of cycles. In both catabolism and anabolism, energy is formed stepwise and broken down stepwise in a number of cycles. This controls the amount of energy stored or released. This controls the amount of energy stored or released.

42 The energy is passed along in two energy processes: Exergonic reactions and Endergonic reactions. The energy is passed along in two energy processes: Exergonic reactions and Endergonic reactions.


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