This document discusses cellular energy processes like photosynthesis and respiration. It provides information on: - Photosynthesis uses light energy from the sun to produce glucose from carbon dioxide and water. It occurs in two stages: the light-dependent reactions in the chloroplasts that produce ATP and NADPH, and the light-independent Calvin cycle in the stroma that uses these products to form glucose. - Cellular respiration breaks down glucose to release energy, occurring either aerobically with oxygen in the mitochondria to produce 36-38 ATP, or anaerobically through fermentation to produce 2 ATP. Aerobic respiration involves glycolysis, the Krebs cycle, and the electron transport chain. - ATP is

1. Unit 2
Cellular Energy
Photosynthesis & Respiration

2. Energy
• Energy is the ability to do work.
• Thermodynamics is the study of the flow and
transformation of energy in the universe.
• 1st Law – energy can be converted from one
form to another, but it cannot be created
nor destroyed.
• 2nd Law – energy cannot be converted
without the loss of usable energy.

3. Autotrophs vs. Heterotrophs
Use light energy from
sun to make own food
Obtain energy from other
organisms
ALL ORGANISMS NEED ENERGY TO CARRY OUT LIFE FUNCTIONS
(reproduction, repair, growth, development, movement) AND MUST
RELEASE ENERGY FROM SUGARS AND OTHER COMPOUNDS!!

4. Cellular Energy
Processes
• Photosynthesis – light energy from the Sun is
converted to chemical energy for use by the
cell.
• Cellular Respiration – organic molecules (such
as glucose) are broken down to release energy
for use by the cell.

5. Photosynthesis
Photosynthesis is the process by which the solar
energy of sunlight is converted into the chemical
energy of glucose by producers such as plants,
algae (protists) and some bacteria.

6. Photosynthesis
• Photosynthesis occurs in the cell organelle
called the chloroplasts. Chloroplasts contain
thin, disk-like structures called thylakoids. The
space/substance surrounding the thylakoids is
called the stroma.

7. Photosynthesis
• Chlorophyll is the pigment
inside the thylakoid of
chloroplasts, that absorbs light
for photosynthesis (and makes
the plant green).
• Other pigments include the
colors red, orange, and yellow.

8. 8

9. Electron Carriers
• When a potato is very hot, you wouldn’t dare
grab it with your bare hand, rather you use an
oven mitt to carry the potato. As the potato
cools, you no longer need the oven mitt.
• This is similar to an electron carrier. Once an
electron receives energy from the sun, it is
considered a “high-energy electron.” The
electron does not travel on its own from place
to place. Another substance (in this case NADP)
carries the electron to its destination. As the
electron loses it’s high energy levels, it no
longer needs an electron carrier.
• An electron carrier then is “a compound that
can accept a pair of high-energy electrons and
transfer them, along with most of their energy,
to another molecule.”
NADP+ / NADPH
= electron carrier

10. Photosynthesis
Photosynthesis occurs in two phases:
• Light-dependent Reactions
• H20 is broken down and light energy is
stored temporarily in inorganic energy
carriers, ATP and NADPH
• Light-independent Reactions (Calvin Cycle)
• Energy is transferred from ATP and NADPH
to the organic compound glucose

12. Photosynthesis
Light-dependent Reactions
• Require light and H2O
• Occurs in the thylakoid membrane
• Use energy from light to produce O2 and
convert ADP and NADP+ into the energy
carriers ATP and NADPH.

13. Photosynthesis
Light-independent Reactions
• Does NOT require light
• Occurs in the stroma
• Uses ATP and NADPH from light-dependent
reactions (and CO2 from the environment) to
produce high-energy sugars that can be stored
for a long time.

14. Summary of Photosynthesis
H2OO2
Glucose
H2O
ATP & H+
CO2
Light-dependent
Reaction
Light-independent
Reaction
Light

15. Factors that Affect
Photosynthesis
Light Intensity
Temperature
Water and Carbon Dioxide levels

16. Alternate Pathways
• In hot, dry environments plants have adapted
to a different way to perform photosynthesis:
• C4 Plants
•Able to make glucose in different cells.
Ex: Corn and Sugarcane
• CAM Plants
•Are able to make glucose at different
time of the day.
Ex: Pineapples and Cacti

17. Cellular Respiration
• Cellular respiration is the process by which the
energy of glucose is released in the cell to be
used for life processes.
• Respiration occurs in ALL CELLS!
• The equation for cellular respiration is the
opposite of the equation for photosynthesis.

18. Cellular Respiration
• Types of Respiration
• Aerobic Respiration – requires oxygen
• Anaerobic Respiration – uses no oxygen

19. Aerobic Respiration
• Occurs in the mitochondria of the cell
• Total of 34-36 ATP molecules are produced
• 3 stages of aerobic respiration
• Glycolysis
• Krebs Cycle
• Electron Transport Chain & Chemiosmosis
(34-36

20. 20

21. Aerobic Respiration
Glycolysis
• Occurs in the cytoplasm of the cell
• This stage occurs in both aerobic and
anaerobic respiration because oxygen is not
required!
• Glucose breaks down into 2 pyruvate
• 2 ATP are produced

22. Aerobic Respiration
Glycolysis
Inputs Outputs
• 1 glucose
• 2 ATP (needed to start)
• 2 pyruvates (go to Krebs)
• 4 ATP (2 are gained)
• 2 NADH (go to ETC)

23. Aerobic Respiration
Krebs Cycle
• Occurs in the mitochondria
• A series of reactions occur (not just one step)
• Main purpose is to generate electrons of use in
the electron transport chain (ETC)
• 2 ATP is given off

24. Aerobic Respiration
Krebs Cycle
Inputs Outputs
• 2 pyruvate • 2 ATP
• 6 NADH (go to ETC)
• 2 FADH2 (go to ETC)
• 4 CO2 (given off as waste)

25. Aerobic Respiration
Electron Transport Chain (ETC) and Chemiosmosis
• Occurs in the inner membrane of mitochondria
• Series (chain) of coupled reactions (electrons
are transported through the chain)
• Electrons carried to this step by NADH and
FADH2 (produced in Kreb’s Cycle)
• Oxygen is used in this step
• Water is given off

26. Aerobic Respiration
Electron Transport Chain and Chemiosmosis
Inputs Outputs
• 8 NADH
• 2 FADH2
• Oxygen
• 32 ATP
• H2O

27. Aerobic Respiration
Where do we get
36 ATP?
• 2 ATP made in
glycolysis
• 2 ATP made in
Krebs Cycle
• 32 ATP made
in ETC

28. Anaerobic Respiration
• Also called fermentation!
• Uses Glycolysis
• Yields 2 pyruvate and 2 ATP
• With no oxygen present, cellular respiration
does not occur.
• ONLY 2 ATP ARE PRODUCED (compared to
aerobic respiration)
• 2 types of fermentation:
• Alcoholic Fermentation
• Lactic Acid Fermentation

29. Anaerobic Respiration
Alcoholic Lactic Acid
• Pyruvate
ethyl alcohol, CO2
2ATP
• Carried out by
and some bacteria
• Used in producing
alcohol (both
consumable and
ethanol), and for
• Pyruvate converted
lactic acid and 2
• Carried out by
when working hard
(muscles need ATP
can’t get O2)
• Causes muscle
soreness and

30. 30
Glycolysis
Pyruvic acid
2 ATP
Anaerobic
Aerobic
Lactic Acid
Fermentation
Alcoholic
Fermentation
Lactic Acid
2 ATP
Ethyl Alcohol,
CO2, 2 ATP
In
cytoplasm
Electron Transport
Chain 32
ATP
Kreb’s Cycle
2 ATP
36 ATP, CO2
& H2O
Cellular Respiration
Summary

31. 31
Characteristic Inputs 1st step
Uses
oxygen?
Cell location Outputs
Number
of ATP
produced
Net Gain
of ATP
Aerobic
Respiration
Glucose Glycolysis Yes Mitochondria
CO2, H2O,
energy
(ATP)
38 ATP 36 ATP
Lactic Acid
Fermentation
Glucose
Glycolysis
No
Cytoplasm Lactic
acid, ATP
4 ATP 2 ATP
Alcoholic
Fermentation
Glucose Glycolysis No Cytoplasm
Ethyl
alcohol,
CO2, ATP
4 ATP 2 ATP
Cellular Respiration
Summary

32. Factors that Affect Cellular
Respiration
Temperature
Oxygen levels

34. Adenosine Triphosphate
(ATP)
• ATP is one of the principal chemical
compounds that cells use to store and release
energy.
• ATP powers all cellular work!
Ribose
(sugar)
3 Phosphate groups
Adenine
(base)

35. Cycling of ATP
How is energy stored and released in a cell?
• All energy is stored in the bonds of compounds –
breaking the bond releases the energy.
• When the cell has energy available it can store this
energy by adding a phosphate group to ADP,
producing ATP.

36. Cycling of ATP
ATP is converted into ADP by breaking the bond
between the second and third phosphate groups
and releasing “stored” energy for cellular
processes.
ATP + H2O  ADP + P + ENERGY