1. Photosynthesis and Cellular Respiration
ENERGY AND THE CELL
Photosynthesis
and
Cellular Respiration

2. Energy and the Cell
“Mitochondria and Chloroplast” – providing energy to living things
MITOCHONDRIA
CHLOROPLAST

3. Energy and the Cell
Breakdown of starch
Energy is released form starch in a series of enzyme – assisted chemical reactions.

4. Energy and the Cell
ENERGY FLOWS BETWEEN ORGANISMS IN LIVING THINGS
Sunlight is a non-usable form of energy for living cells.
Autotrophs (organisms that make their own food) use energy from sunlight to run metabolic processes that result in the production of food (organic compounds).
Heterotrophs are organisms that cannot make their own food. They need to eat or consume something else.

5. Energy and the Cell
ATP STORES AND RELEASES ENERGY
There is a great amount of energy stored in the bonds between the phosphate groups especially in the third phosphate. When these bonds are broken the energy released is used to run a cellular (metabolic) process.
ATP ADP + P + Energy

6. Energy and the Cell
ATP STORES AND RELEASES ENERGY
ATP - Adenosine triphosphate, is an organic molecule composed of a base (adenine), sugar (ribose), and three phosphate groups. That acts as the main energy currency of cells.
The Biochemistry of energy release.

7. Energy and the Cell
The diagram to the right and the chemical reaction above show the reactants and products of photosynthesis.
Energy from the sun is used to run this reaction. A glucose molecule is produced.
The chemical bonds that hold the atoms of glucose together are rich in chemical energy.
So the reason plants make glucose is to store energy for later use that will run metabolic processes.

8. Energy and the Cell
PHOTOSYNTHESIS –The process by which light energy originating from the sun is used to produce organic compounds.
These compounds that are produced are rich in chemical energy, which can be harnessed, when these organic compounds are broken down through metabolic processes.

9. Energy and the Cell
PHOTOSYNTHETIC ORGANISMS USE THE ENERGY IN SUNLIGHT
Chloroplasts reflect green light (not used). Blue and red light is absorbed from electromagnetic spectrum.
Splitting water in thylakoid membrane keeps the process
going.
Responsible for powering photosynthesis.

10. Photosynthesis Overview
Stage 1: Energy is captured from sunlight.
Stage 2: Light energy is converted into chemical energy, which is temporarily stored in ATP and the electron carrier molecule NADPH
Stage 3: The chemical energy stored in ATP and NADPH powers the formation of organic compounds, using carbon dioxide (CO2).

11. Stage 1: Light Energy is Absorbed
Energy released from the sun is radiation.
Different types of radiation (heat, light) have different wavelengths.
Visible Spectrum of Light is absorbed by different pigments in skin, leaves, clothing, etc.

12. Chlorophyll and other Pigments
Chlorophyll absorbs red and blue light and reflects green and yellow - making plants look green
Chlorophyll a and Chlorophyll b
Fall colors are produced by other pigments - carotenoids which reflect orange and yellow

14. THYLAKOID – Disc shaped membrane sac structure found inside the chloroplast. Site where light energy is absorbed and used to run the photosynthesis reaction that energy is also converted into chemical energy.
CHLOROPHYLL - Primary pigment responsible for trapping light energy in photosynthesis. It is the pigment that gives many plants their green appearance.

15. Production of Oxygen Photosynthesis occurs in the chloroplasts.
Within the chloroplasts are disk-shaped structures called thylakoids
Has TWO membranes
A “bi-bilayer!”
The inner membrane is called the thylakoid.
The thylakoid is folded and looks like stacks of coins called granum (grana singular).
The stroma is the space surrounding the granum

16. Chloroplasts
Chlorophyll molecules are embedded in the thylakoid membrane
Act like a light “antenna”
These molecules can absorb sunlight energy.

17. Production of Oxygen
When light strikes the thylakoid, energy is transferred to electrons in chlorophyll
Electrons become “excited” with extra energy
Excited electrons jump from chlorophyll to chlorophyll molecule

18. Outside Thylakoid e- Thylakoid Space 4H+ 2H2O O2
Outside Thylakoid e-
Thylakoid Space
Water-splitting Enzyme
4H+
2H2O O2
When electrons leave a chlorophyll they are replaced by the electron in a hydrogen atom from water - releasing oxygen.

19. Stage II: Light Energy Converted to Chemical Energy
Excited electrons are used to create new molecules (including ATP) that temporarily store energy
Excited electrons are passed through down through the thylakoid membrane via the Electron Transport Chain
As electrons are passed, their energy allows Hydrogen ions to pass into the thylakoid - concentration gradient

21. Stage II: Light Energy Converted to Chemical Energy
Hydrogens diffuse back out of the thylakoid through carrier proteins.
As they pass through, they assist the production of ATP from ADP and P.
Second electron transport chain provides energy to produce NADPH which will help make C-H bonds later.

23. The Light (Dependent) Reaction of Photosynthesis
Stages I and II
Pigment molecules in the thylakoids of chloroplasts absorb light energy
Electrons are excited and move through electron transport chains in the thylakoid membrane
These electrons are replaced by those from water, releasing oxygen gas
Hydrogen ions accumulate inside the thylakoid and then diffuse out creating ATP and NADPH

24. Light Independent Reactions (formerly the “dark reactions”)
Happen in sunlight, and in the dark.
Hence “independent of light”
ATP generated by sunlight drives the Calvin Cycle.
Monosaccarides (eg. glucose) are manufactured in the cycle.
Monosaccarides are used to “build” polysaccharides (eg. Starch).

25. Steps of the Calvin Cycle (Carbon Fixation)
Step 1: Each CO2 molecule is added to a 5-carbon compound by an enzyme.
Step 2: Resulting 6-C compound splits in half, Phosphates are added to the 3-C compounds forming 3-C sugars.
Step 3: One of the 3-C sugars is used to make glucose.
Step 4: The other 3-C sugar is used to regenerate the original 5-C compound.

26. Occurs in the Stroma

27. Occurs in the Stroma
The Calvin cycle has three stages.
In stage 1, the enzyme RuBisCO incorporates carbon dioxide into an organic molecule, 3-PGA.
In stage 2, the organic molecule is reduced using electrons supplied by NADPH.
In stage 3, RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue.

28. Occurs in the Stroma
The Calvin cycle has three stages.

29. Factors affecting the rate of Photosynthesis
Amount of Light
Carbon Dioxide Concentration
Temperature

30. Photosynthesis: Overall Summary
Photosynthesis Occurs in Chloroplasts.
Light Reaction (Stages I and II): Capture of sunlight energy by electrons and splitting of water which releases oxygen gas.
Light-Independent Reaction (Stage III): Creation of Glucose from Carbon Dioxide; Calvin Cycle.
Overall Reaction:
CO2 + H2O + sunlight energy C6H12O6 + O2

31. Energy and the Cell

32. Cellular Respiration
Involves the Breakdown of Organic Matter to produce usable form of energy (ATP).
Two Types:
Aerobic - A metabolic process that requires oxygen by which living things harvest the energy from food molecules (organic compounds). This process yields large amounts of ATP (useable form energy in cells).
Anaerobic - A metabolic process that does not require oxygen. Living things still harvest the energy from food molecules (organic compounds). This process yields lower amounts of ATP as compared to aerobic respiration.

33. Energy and the Cell
The equation above shows the overall reaction of what happens in aerobic respiration, but not how it happens. Living things perform this chemical reaction to release biochemical energy, which is stored in or used to produce ATP molecules.
In the cytoplasm of the cell, glucose is split into two individual 3-carbon compounds (Pyruvate). No oxygen is needed for this to occur and very little ATP is produced.
In Eukarytoic cells these 3-carbon compounds enter one of the mitochondria in the cell, and with the presence of oxygen are broken down further to produce large amounts of useable energy (ATP). Carbon dioxide and water are also produced, but are wastes.

34. Energy and the Cell The three parts of Aerobic Cellular Respiration:
Glycloysis (happens in Cytoplasm)
Kreb Cycle (happens in in mitochondrial matrix)
Electron Transport Chain (happens in in mitochondrial membrane)

35. Glycolysis
Glycolysis is a metabolic pathway by which a 6-carbon glucose (Glc) molecule is broken down into two molecules of pyruvate.

37. Energy and the Cell Krebs Cycle
The pyruvate molecules produced during glycolysis contain a lot of energy in the bonds between their molecules.
In order to use that energy, the cell must convert it into the form of ATP.
To do so, pyruvate molecules are processed through the Kreb Cycle.
Prior to entering the Krebs Cycle, pyruvate must be converted into acetyl CoA.

38. Krebs Cycle

39. Energy and the Cell
Electron Transport Chain
The electron transport chain, is a sequence of complexes found in the mitochondrial membrane that accept electrons from electron donors.
These donors shuttle these electrons across the mitochondrial membrane creating an electrical and chemical gradient, and, through the proton driven chemistry of the ATP synthase, generate adenosine triphosphate.

40. Electron Transport Chain
Electron Transport Chain

41. Overall Energy Yield - Aerobic Cellular Respiration
Glycolysis - 2 ATP
Krebs Cycle - 2 ATP
Electron Transport Chain - 32 ATP
Total - 36 ATP

42. Energy and the Cell
FERMENTATION FOLLOWS GLYCOLYSIS IN THE ABSENCE OF OXYGEN
FERMENTATION – Anaerobic process of cellular respiration that recycles NAD+ needed to continue glycolysis.

43. Energy and the Cell
FERMENTATION FOLLOWS GLYCOLYSIS IN THE ABSENCE OF OXYGEN
When oxygen is not present organisms can break down organic compounds by using a different chemical mechanism.
Simple organisms like bacteria produce all of their energy (ATP) this way.
When a person feels that their muscles burning after working out it is because their muscles are breaking down sugar by anaerobic respiration because there is no oxygen available in the muscle cells.
There is a build of lactic acid in the muscle cells that is product of this reaction, it is what causes the burning sensation.

44. Comparison of Aerobic and Anaerobic Cellular Respiration
Glucose
2 ATP
Glycolysis
Without Oxygen
Pyruvate
With Oxygen
Krebs Cycle
2 ATP
Fermentation
Ethanol and Carbon Dioxide
Lactate
Electron Transport Chain
32 ATP

45. Comparison of aerobic and anaerobic respiration
in animals
in plants and yeast
Oxygen required?
yes no
Glycolysis occurs
ATP yield
36ATP
2ATP
Glucose completely broke down?
End products
Carbon dioxide and water
Lactic acid
Ethanol and carbon dioxide