Ch. 8 & 9 – Photosynthesis and
Cellular Respiration
I. Energy and Life
A. All organisms require energy for survival.
1. Ultimately, all of the energy in food comes from
the sun.
I. Energy and Life
2. Autotrophs – organisms that make their own food
using energy from the sun
a. Example: Plants, algae, and some bacteria
can trap energy from the sun (light energy) and
convert it into food (chemical energy)
I. Energy and Life
3. Heterotrophs – organisms that eat plants or other
animals to get energy
b. Example: Animals and other organisms
cannot trap sunlight directly for food; instead
they eat green plants or animals for food.
I. Energy and Life
4. Why do organisms need energy?
To move, breathe, reproduce
5. Why do cells need energy?
Active transport, cell division, to make proteins
6. Where does energy come from?
Food (carbohydrates = quick energy)
(lipid= long term energy)
I. Energy and Life
B. Two Types of Cellular Energy
I. Energy and Life
1. ATP (Adenosine Triphosphate) – a molecule
with 3 phosphate groups, ribose (a sugar), and
adenine (a nitrogen base).
I. Energy and Life
2. ADP (Adenosine Diphosphate) – a molecule with 2
phosphate groups, ribose (a sugar), and adenine (a
nitrogen base).
a. ADP is created when ATP loses energy and a
phosphate.
I. Energy and Life
ATP vs. ADP
I. Energy and Life
3. How is energy released and stored?
a. Energy is released by breaking the bond and
removing a phosphate.
ATP  ADP
b. Energy is stored by adding 1 phosphate to ADP.
ADP  ATP
Energy
I. Energy and Life
I. Energy and Life
4. Most cells only have a small quantity of ATP (just a
few seconds worth)!
a. ATP is not efficient at storing energy for a long
time.
b. Cells rely on the ability to make more ATP from
ADP by using energy from carbohydrates and
lipids.
II. Photosynthesis
A. Photosynthesis – when an autotroph uses
carbon dioxide, water, and sunlight to make
glucose, with oxygen as a byproduct.
II. Photosynthesis
1. Photosynthesis Equation –
CO2 + H2O + light energy
C6H12O6 + O2
II. Photosynthesis
2. Chloroplast – organelle where photosynthesis occurs
3. Chlorophyll – Most common pigment in chloroplasts; it
reflects green light
a. Must be present for photosynthesis to occur.
II. Photosynthesis
Photosynthesis has 2 stages or reactions:
– Light dependent reactions
– Light independent reactions (a.k.a. Calvin Cycle)
II. Photosynthesis
B. Two Steps of Photosynthesis
1. Step One: Light Dependent
Reactions
a. Require light!
b. Chlorophyll absorbs
sunlight, which causes
electrons to gain lots of
energy; ATP (energy
carrier) and NADPH
(electron carrier) are
stored for light
independent reactions.
II. Photosynthesis
NADP+
NADPH
NADP+
II. Photosynthesis
c. Water molecules
broken apart into
hydrogen gas and
oxygen gas.
- H2O + Light  O2 + H2
- Oxygen is released
as a byproduct to the
atmosphere.
II. Photosynthesis
2. Step Two: Light Independent Reactions (A.K.A. The Calvin
Cycle)
a. Does not require light!
b. Carbon dioxide and hydrogen gas form glucose
(sugar), using energy from ATP and electrons from
NADPH.
CO2 + H2  C6H12O6
II. Photosynthesis
3. Factors That Influence Photosynthesis Rate
a. Lack of Water
Example/Adaptation: Desert
plants/conifers (pines)  waxy coating
and needle “leaves” to reduce water loss
II. Photosynthesis
b. Temperature – Influences the activity of enzymes
- Best around 35 degrees.
c. Intensity of Light (varies by plant)
- Excess UV rays/sunlight can decrease
photosynthesis.
Chapter 9:
Cellular Respiration
Energy Review
• Plants—make food (sugar) through
photosynthesis
• Animals and other organisms—get food by
eating plants and animals
III. Cellular Respiration
A. Cellular Respiration – glucose and food are
broken down to make energy (ATP) in ALL
organisms.
1. Occurs in the mitochondria of eukaryotes.
2. Occurs in the cytoplasm of prokaryotes.
III. Cellular Respiration
3. Cellular Respiration Equation –
C6H12O6 + O2
CO2 + H2O + energy
III. Cellular Respiration
B. Two Types of Cellular Respiration
1. Aerobic Respiration – breaking down of
glucose molecules into smaller pieces in the
presence of oxygen to produce ATP
III. Cellular Respiration
THREE STEPS OF AEROBIC RESPIRATION
1. Glycolysis
2. Kreb’s/Citric Acid Cycle
3. Electron Transport Chain (ETC)
III. Cellular Respiration
2. Three Steps of Aerobic Respiration
a. Glycolysis – occurs in cytoplasm; glucose is
split in half, forming a pyruvate molecule
- 2 ATP released
- electrons released and carried to
mitochondria by NADH
III. Cellular Respiration
III. Cellular Respiration
b. Kreb’s/Citric Acid Cycle – occurs in the
mitochondria; pyruvate is split into smaller
pieces
- CO2 gas released (we breathe it out)
- 2 ATP released
- electrons released and move to
mitochondrial membrane by NADH and
FADH
Cellular Respiration
NAD+
NADH
NAD+
FAD+
FADH
FAD+
III. Cellular Respiration
c. Electron Transport Chain (ETC) – occurs in
the mitochondria; electrons forced through
the mitochondrial membrane
- 32 ATP released
III. Cellular Respiration
- TOTAL ENERGY: 36 ATP
III. Cellular Respiration
3. Anaerobic Respiration – breaking down
glucose molecules into smaller pieces in the
absence of oxygen to produce ATP
III. Cellular Respiration
4. Two Steps of Anaerobic Respiration
a. Glycolysis – occurs in cytoplasm; glucose
is split in half, forming a pyruvate molecule
- 2 ATP released
- electrons released and carried to
mitochondria
III. Cellular Respiration
b. Fermentation – breaking down pyruvate
without oxygen
III. Cellular Respiration
Two Types of Fermentation
1. Lactic Acid Fermentation – pyruvate is broken down
into lactic acid + ATP
– 2 ATP release
– Lactic acid builds up as in muscle cells and causes burning
sensation (muscle cramping) during strenuous exercise.
C-C-C
pyruvate
+
NADH
e’ carrier
 H-C-C-C + ATP + NAD+
 lactic acid energy
carrier
III. Cellular Respiration
2. Alcoholic Fermentation – pyruvate is broken
down into alcohol, carbon dioxide, and ATP in
yeast and bacterial cells
- 2 ATP released
- Used in making bread and
beer
C-C-C + NADH  C-C-OH +
CO2 + ATP
Pyruvate + e’ carrier alcohol + carbon + energy
dioxide
Cellular Respiration
Eat
Digestion
Glycolysis
Oxygen is
present
Aerobic
respiration
No oxygen is
present
Fermentation
(anaerobic respiration)
Citric acid
cycle
In yeast
In animals
Electron
transport chain
Alcoholic
fermentation
Lactic acid
fermentation
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Cellular Respiration
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Photosynthesis
food synthesized
requires energy
Chloroplast
Only autotrophs
vs. Respiration
food broken down
produces energy
mitochondria/cytoplasm
Autotrophs and
heterotrophs (all living cells)