1. UNIT IV – CELLULAR ENERGY
Hillis-
Ch 2.5, 6
Big Campbell ~
Ch 8,9,10
Baby Campbell ~ Ch 5,6,7

2. I. THE WORKING CELL Metabolism
Totality (sum) of an organism’s chemical reactions
Catabolic Pathways -
Breaks down molecules; releases energy; EX: Cellular Respiration
Anabolic Pathways -
Pathway that synthesizes larger molecules from smaller ones; requires energy; EX: synthesis of AA, synthesis of proteins 2

3. I. THE WORKING CELL, cont Energy
Kinetic Energy –energy associated with the relative motion of objects. EX: pool stick  cue ball  other balls
Potential Energy – energy that matter possesses (stored) because of its location or structure. EX: water behind a dam
Chemical Energy – Potential energy of molecules
Thermodynamics
First Law of Thermodynamics states that total amount of energy in universe is constant – can be transferred or transformed, but it cannot be created or destroyed
Principle of the Conservation of Energy
Second Law of Thermodynamics states that energy is lost to the environment as heat; that is, some energy becomes unusable
EX: Bear catching fish for food
Entropy – measure of disorder or randomness that is a consequence of the loss of useable energy during energy transfer.

4. I. THE WORKING CELL, cont
Chemical Reactions are classified according to whether they require or produce energy
Endergonic – Requires net input of energy. Energy is then stored in products as potential energy.
Exergonic - Release energy.
Energy Coupling – Often used in cellular metabolism. Energy released in exergonic rxn is used to drive endergonic rxn. 4

5. ATP It’s energy
1 – 2 – In bonds of P
ATP Energy
Energy in the bonds of P! 

6. II. ATP Powers 3 kinds of work: - Chemical (synthesis of polymers)
- Transport (pumping substances across the membrane)
- Mechanical (beating of cilia, contraction of muscle cells, chromosome
movement) 6

7. II. ATP Adenosine Triphosphate
Nucleotide that stores & provides usable energy to the cell
Structure of ATP
5-C Sugar called Ribose
Nitrogen base Adenine
3 Phosphate groups
ATP contains potential energy, especially between 2nd and 3rd phosphate groups.
P – P bond is unstable
Easily broken by HYDROLYSIS 7

8. II. ATP, cont ATP → ADP + Pi Catabolic Pathway Exergonic
Coupled with endergonic rxn – specifically, by transferring phosphate group from ATP to another molecule.

9. II. ATP, cont ADP + Pi → ATP Anabolic pathway Endergonic
Mechanisms for “making” ATP
Substrate-level Phosphorylation – enzyme transfers a P from a substrate molecule to an ADP (organic molecule generated as an intermediate)
Oxidative Phosphorylation – powered by the redox reactions of the ETC (on the membranes) during chemiosmosis
Photophosphorylation – generation of ATP in the light reactions using chemiosmosis

10. II. ATP, cont Substrate-Level Phosphorylation vs
II. ATP, cont Substrate-Level Phosphorylation vs. Oxidative/Photo Phosphorylation

11. II. ATP, cont
In a human, 10 million molecules of ATP are “made” and “used” per second!!
We use 1 X 1025 (10,000,000,000,000,000,000,000,000 or 10 quadrillion) molecules of ATP per day!!
That translates to 100 lbs of ATP At any given moment, the amount present is ~ 2 oz!!
A working muscle cell recycles its entire supply of ATP in less than a minute!!
Bacteria contain a 1 second supply of ATP!!

12. III. ♪ ♫ THE CYCLE OF LIFE ♪ ♫
Photosynthesis
6CO2 + 6H2O + sun  C6H12O6 + 6O2
Occurs in the chloroplasts of plants
Cellular Respiration
C6H12O6 + 6O2  6CO2 + 6H2O + ATP
Occurs in the mitochondria of plants and animals
CO2 + H2O
Organic molecules + O2

13. IV. ENERGY IN THE CELL Oxidation-Reduction Reactions
Energy yield in catabolism comes from transfer of electrons
Movement of electrons releases chemical energy of molecule
Released energy used to generate ATP from ADP and Pi
Known as redox reaction
One molecule loses an electron and a 2nd molecule gains an e-
Oxidation
Electron donor (which is oxidized)is known as reducing agent (EX: glucose)
Reduction
Electron acceptor (which is reduced)is known as oxidizing agent (EX: O2)
Electron movement in molecules often traced by changes in H atom distribution

14. IV. ENERGY IN THE CELL, cont
Oxidation-Reduction Reactions, cont
Reactants
Products
Becomes oxidized
Becomes reduced
Carbon dioxide
Water
Oxidizing agent - oxygen
Reducing agent - methane

15. IV. ENERGY IN THE CELL, cont
Importance of Electron Carriers
Energy contained in molecules (for example, glucose) must be released in a series of steps
Electrons released as hydrogen atoms with corresponding proton
Hydrogen atoms are passed to an electron carrier
Electron carriers are coenzymes
“Carry” 2 electrons in the form of H-atoms
Allow for maximum energy transfer, minimum energy loss

16. IV. ENERGY IN THE CELL, cont
Electron Carriers
NAD+
Nicotinamide adenine dinucleotide
Electron acceptor in cellular respiration
Reduced to _NADH_
FAD
Flavin adenine dinucleotide
Electron acceptor in Krebs Cycle
Reduced to _FADH2__
NADP+
Nicotinamide adenine dinucleotide phosphate
Electron acceptor in light reaction of photosynthesis
Reduced to _NADPH_

17. IV. ENERGY IN THE CELL, cont
A Closer Look at Electron Carriers
Reduction of NAD+
Dehydrogenase oxidizes substrate by removing 2 H-atoms
NAD+ is reduced, creating NADH + H+
NADH shuttles electrons to electron transport chain. Electrons “fall” down to oxygen in a series of steps, each releasing energy in small amounts.

18. V. PHOTOSYNTHESIS – AN OVERVIEW
Photosynthesis – Process of capturing light energy and converting it to chemical energy
Endergonic – b/c e- increase in potential energy as they move from water to sugar.
Plants are _Producers_; also known as _Autotrophs_
Redox Reaction
becomes oxidized
6CO2 + 6H2O + sunlight C6H12O6 + 6O2
becomes reduced (e- added)
Water is split and e- are transferred with H+ to CO2, reducing it to sugar. 18

19. V. PHOTOSYNTHESIS – AN OVERVIEW
Chloroplast Structure
Thylakoids –
Site of Light Reaction
First step in photosynthesis
Grana
Stroma
Site of Calvin Cycle
Second step in photosynthesis

20. V. PHOTOSYNTHESIS – AN OVERVIEW, cont
Location of Photosynthesis
Occurs in region of leaf known as mesophyll
Cells contain abundant chloroplasts
CO2 enters leaf through openings known as stomata
H2O enters via roots; transported up the xylem

21. V. PHOTOSYNTHESIS OVERVIEW, cont
Oxidation
Reduction 21

22. V. PHOTOSYNTHESIS OVERVIEW, cont
Sunlight: giant thermonuclear reactor – energy comes from fusion reactions similar to those in a hydrogen bomb.
When light hits matter, it can be reflected, transmitted, or absorbed.

23. VI. LIGHT REACTION OF PHOTOSYNTHESIS
Occurs in thylakoid membranes
Converts light energy to chemical energy
Light energy
Visible light is a small portion of the electromagnetic spectrum.
Light absorbed by chlorophyll and other photosynthetic pigments to power reactions is not seen. Light not utilized by plant is reflected & seen by human eye. (Leaf appears green b/c it reflects green &absorbs red and blue light)
Light energy measured in photons, which each have a fixed quantity of energy inversely related to the wavelength. 23

24. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont
Photosynthetic pigments - (substances that absorb visible light)
Chlorophyll a – absorbs mainly blue-violet and red light
Chlorophyll b – absorbs mainly blue and orange light
Cartenoids – other accessory pigments; expand spectrum of light energy that can be used for photosynthesis
carotenoid
xanthophyll
Chlorophyll a
Chlorophyll b

25. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont
The ability of a pigment to absorb various wavelengths of light can be measured with a spectrophometer which directs beams of light of different wavelengths through a solution of pigment and measures light transmitted at each wavelength.

26. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont26

27. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont
A photon of light energy is absorbed by pigment molecule in Photosystem II.
Energy is passes from one molecule to another until it reaches P680 - pair of chlorophyll a molecules.
Electron in each is excited to higher energy state – transferred to primary electron acceptor.
Water is split to replace electron lost by P680. O2 is released. H+ ions remain. 27

28. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont
Excited electron moves from primary electron acceptor to Photosystem I via electron transport chain. As electron “falls”, energy is released. Used to synthesize ATP through chemiosmosis.
Known as photophosphorylation

29. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont
Light energy is transferred via light-harvesting complexes to P700 in Photosystem I.
Excited electron is captured by primary electron acceptor. P700’s electron is replaced by electron transport chain on Photosystem II.
Electron from P700 moves through a short electron transport chain, reducing NADP+ to NADPH. 29

30. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont
Linear Electron Flow 30

31. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont
Cyclic Electron Flow
Alternative pathway seen in some bacteria, plants
May be photoprotective in plants
Only utilizes Photosystem I
No NADPH production
No O2 release
Does generate ATP 31

32. VII. CALVIN CYCLE OF PHOTOSYNTHESIS
Also known as Dark Reaction, Light-Independent Rxn
Occurs in stroma of chloroplasts
“Synthesis” part of photosynthesis; utilizes ATP, NADPH generated in Light Reaction + CO2 to produce organic molecules
Anabolic; endergonic
Requires enzyme Rubisco
Three basic steps
Carbon Fixation
Reduction
Regeneration of RuBP 32

33. VII. CALVIN CYCLE OF PHOTOSYNTHESIS, cont33

34. VIII. PHOTORESPIRATION
Counterproductive pathway that produces 2-C molecule, which is then released as CO2
Due to oxygen competing for active site of Rubisco
Consumes ATP; decrease carbohydrate yield

35. VIII. PHOTORESPIRATION, cont
Plant Adaptations 35

36. IX. CELLULAR RESPIRATION – AN OVERVIEW
Process used by cells to convert chemical energy in glucose (and other molecules) to ATP
Primarily takes place in mitochondria of eukaryotic cells
Overall Reaction
becomes oxidized
C6H12O6 + 6O2  6CO2 + 6H2O + energy
becomes reduced
Steps in Cellular Respiration
Glycolysis
“Sugar-breaking”
Initial breakdown of glucose to intermediate, some ATP
Citric Acid Cycle
Completes oxidation of glucose to CO2
Produces ATP, but more importantly provides high-energy electrons for etc
Electron Transport Chain
Oxidative Phosphorylation
Highest ATP yield; uses energy released from downhill flow of electrons to generate ATP
Citric Acid Cycle + Electron Transport Chain = Oxidative Respiration

37. IX. CELLULAR RESPIRATION OVERVIEW, cont

38. X. GLYCOLYSIS Occurs in cytosol of cell Does not require oxygen
First part of pathway is energy investment phase
Second part of pathway is energy pay-off phase
Energy Investment Phase

39. X. GLYCOLYSIS, cont
Energy Pay-Off Phase

40. X. GLYCOLYSIS, cont
Summary of Glycolysis

41. XI. OXIDATIVE RESPIRATION
2 pyruvates formed from glycolysis still contain a tremendous amount of chemical energy
If oxygen is available, pyruvate enters mitochondrion for citric acid cycle and further oxidation
Upon entering mitochondrion but prior to entering citric acid cycle
“Grooming” Step
Carboxyl group of pyruvate is removed, given off as CO2
Remaining 2-C molecule is oxidized to acetate → NAD+ reduced to NADH + H+
Acetate binds to molecule known as Coenzyme A to form acetyl CoA

42. XI. OXIDATIVE RESPIRATION, cont
Grooming Step

43. XI. OXIDATIVE RESPIRATION, cont
In the citric acid cycle (AKA Krebs cycle, tricarboxylic acid cycle, TCA cycle), 2-C molecule goes through a series of redox rxns.
Occurs in mitochondrial matrix
Produces NADH, FADH2, ATP, and CO2.
CoA is not actually a part of the reaction it is recycled remember, it is an enzyme!

44. XI. OXIDATIVE RESPIRATION, cont
A Closer Look at the Citric Acid Cycle

45. XI. OXIDATIVE RESPIRATION, cont
Electron Transport – Oxidative Phosphorylation
Traditionally called Electron Transport, now more commonly called Oxidative Phosphorylation.
Occurs in inner mitochondrial membrane
Membrane organized into cristae to increase surface area
Two components to Oxidative Phosphorylation
Electron Transport Chain
Chemiosmosis

46. XI. OXIDATIVE RESPIRATION, cont
Electron Transport Chain
Collection of molecules, each more electronegative than the one before it
Molecules are reduced, then oxidized as electrons are passed down the chain
Oxygen is ultimate electron acceptor
Purpose is to establish H+ gradient on two sides of inner mitochondrial membrane
Energy from “falling electrons” used to pump H+ from matrix into intermembrane space

47. XI. OXIDATIVE RESPIRATION, cont
Chemiosmosis
Enzyme complexes known as ATP synthases located in inner mitochondrial membrane
H+ electrochemical gradient provides energy
Known as proton motive force
Movement of H+ ions through membrane rotates enzyme complex
Rotation exposes active sites in complex
ATP is produced from ADP and Pi

48. XI. OXIDATIVE RESPIRATION, cont
A summary of electron transport . . .

49. XII. CELLULAR RESPIRATION – A SUMMARY
Each NADH shuttled through ETC results in approximately _________ ATP
Each FADH2 shuttled through ETC results in approximately _________ ATP.
Total ATP Gain in Cellular Respiration =
____ (glycolysis) + ____ (citric acid cycle) + ____ (oxidative phosphorylation) = _____ ATP / glucose

50. XIII. CELLULAR RESPIRATION & OTHER FOOD MOLECULES

51. XIV. METABOLIC POISONS Blockage of Electron Transport Chain
Inhibition of ATP Synthase
“Uncouplers”
Prevent creation of H+ ion gradients due to leakiness of mitochondrial membrane

52. XV. FERMENTATION Anaerobic pathway Occurs in cytosol Purpose
In glycolysis, glucose is oxidized to 2 pyruvate, 2 NAD+ are reduced to 2 NADH, and there is a net gain of 2 ATP
In oxidative respiration, NADH is oxidized back to NAD+ in electron transport chain
If oxygen is not present, another mechanism must be available to regenerate NAD+ or glycolysis cannot continue
In fermentation, pyruvate is reduced thereby oxidizing NADH to NAD+
Allows glycolysis and net gain of 2 ATP per glucose to continue

53. XV. FERMENTATION, cont

54. XV. FERMENTATION, cont