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, 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

3. I. THE WORKING CELL 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 Metabolism
Totality (sum) of an organism’s chemical reactions
Two types of reactions
Catabolic Pathways
Breaks down molecules; releases energy; EX: Cellular Respiration
Exergonic
Anabolic Pathways
Pathway that synthesizes larger molecules from smaller ones; requires energy; EX: synthesis of AA, synthesis of proteins
Endergonic 4

5. I. THE WORKING CELL, cont
Gibbs Free Energy (ΔG)

6. I. THE WORKING CELL, cont
ΔG and Enzyme Catalysis

7. I. THE WORKING CELL, cont Energy Coupling
Energy released in exergonic rxn is used to drive endergonic rxn.

8. 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) 8

9. 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 9

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

11. 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

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

13. 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!!

14. 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

15. 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)

16. IV. ENERGY IN THE CELL, cont
Oxidation-Reduction Reactions
Electron movement in molecules often traced by changes in H atom distribution
Reactants
Products
Becomes oxidized
Becomes reduced
Water
Reducing agent - methane
Oxidizing agent - oxygen
Carbon dioxide

17. 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

18. 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_

19. 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_

20. V. PHOTOSYNTHESIS – AN OVERVIEW
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. 20

21. V. PHOTOSYNTHESIS – AN OVERVIEW, cont
Water Movement
Root Structure Ψ
Transpiration

22. V. PHOTOSYNTHESIS – AN OVERVIEW, cont
Leaf Structure
Epidermis
Cuticle
Stomata & Guard Cells
Mesophyll
Chloroplast Structure
Thylakoids –
Site of Light Reaction
First step in photosynthesis
Granum
Stroma
Site of Calvin Cycle
Second step in photosynthesis

23. V. PHOTOSYNTHESIS OVERVIEW, cont
Oxidation
Reduction 23

24. 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.

25. 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. 25

26. 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

27. 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.

28. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont28

29. 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. 29

30. 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

31. 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. 31

32. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont
Linear Electron Flow 32

33. 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 33

34. 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 34

35. VII. CALVIN CYCLE OF PHOTOSYNTHESIS, cont35

36. VII. CALVIN CYCLE OF PHOTOSYNTHESIS, cont Sugar Transport
From sugar source  sugar sink
Sieve tubes – pathway for translocation of sugars (phloem)
Moves by Bulk Flow which is driven by positive pressure known as pressure flow.
Building of pressure at source & reduction of that pressure at the sink causes sap to flow source sink

37. VIII. PHOTORESPIRATION
Counterproductive pathway
Plants close stomata to prevent water loss; decreases CO2
Oxygen binds to active site of Rubisco – product splits and a 2C compound leaves chloroplast… Peroxisomes & mitochondria rearrange & split this compound, releasing CO2
Consumes ATP; decrease carbohydrate yield
Purpose = neutralize damaging products of the light Rxns which build up when Calvin cycle is limited.

38. VIII. PHOTORESPIRATION, cont
Plant Adaptations
C4 Plants (C4 Photosynthesis)
- Alternate mode of carbon
fixation to minimize photorespiration
and optimize Calvin cycle
- Uses PEP carboxylase to bond
CO2 to PEP to form a 4-C compound
- Occurs in mesophyll cells
- Passes the 4-C compound through
plasmodesmata to Bundle sheath cells
- EX: sugarcane, corn, grasses

39. VIII. PHOTORESPIRATION, cont
Plant Adaptations, cont
CAM Plants
- Crassulacean acid metabolism
- Adaptation to dry, arid
- Stomata open at night &
closed during day.
- Incorporate CO2 at night &
convert into 4-C organic acids
- Organic acids stored in
vacuoles of mesophyll cells
until am when stomata close.
- EX: succulents such as
cacti and pineapple

40. 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

41. IX. CELLULAR RESPIRATION OVERVIEW, cont
Glycolysis
“Sugar-breaking”
Initial breakdown of glucose to intermediate, some ATP
Pyruvate Oxidation
Occurs in mitochondria
Krebs 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

42. 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

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

44. X. GLYCOLYSIS, cont
Summary of Glycolysis

45. XI. OXIDATIVE RESPIRATION
Pyruvate Oxidation
Oxygen must be available
Takes place in mitochondrial matrix prior to Citric Acid Cycle …
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

46. XI. OXIDATIVE RESPIRATION, cont
Citric Acid Cycle (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!

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

48. 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

49. 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

50. XI. OXIDATIVE RESPIRATION, cont
A summary of oxidative phosphorylation . . .

51. XI. OXIDATIVE RESPIRATION, cont

52. XII. CELLULAR RESPIRATION – A SUMMARY
Each NADH shuttled through ETC results in approximately ___2.5___ ATP
Each FADH2 shuttled through ETC results in approximately __1.5___ ATP.
Total ATP Gain in Cellular Respiration =
_2_ (glycolysis) + _2_ (citric acid cycle) + _28_ (oxidative phosphorylation) = _32__ ATP / glucose

53. XII. CELLULAR RESPIRATION – A SUMMARY, cont

54. XIII. CELLULAR RESPIRATION & OTHER FOOD MOLECULES

55. 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

56. 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

57. XV. FERMENTATION, cont

58. XV. FERMENTATION, cont