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Photosynthesis
Unit 6
Unit 6 Packets and “What’s in a Leaf?” POGILs
are at the desks already – grab one. Turn in
completed Winter Break assignments and be
ready to get some notes!
Unit 6 Overview
• Day 1 – Notes on Photosynthesis and “What’s in a leaf?”
POGIL
• Day 2 – Photosynthesis GIZMO and set up Photosynthesis
Research Notebook/LAB
• Day 3- Carry out Photosynthesis Lab (must bring notebooks
and dress properly)
• Day 4 – Quiz on Photosynthesis and continue to work in
class on lab
• Day 5 – Lab Notebooks Due, take Cell Respiration notes in
class
• Day 6 – Compare and Contrast Photosynthesis and Cell
Respiration. Complete POGIL in Class and review for test.
• Day 7 – Unit 6 Test
• Day 8 – SOL Diagnostic (Not Graded)
Autotrophs & Heterotrophs
• Autotrophs – organisms use can make
their own food
– Some autotrophs capture light energy from
the sun in the process of photosynthesis
• Heterotrophs – obtain energy from the
foods they consume
ATP & Energy
Structure of ATP
A. ATP (Adenosine Triphosphate) – shuttles
energy for cells
B. ATP is composed of ribose (a sugar),
adenine (a nitrogenous base), and three
phosphate groups
ATP & Energy
A. The bond between the terminal phosphate
groups of ATP’s can be broken, releasing
organic phosphate and leaving ADP
(adenosine diphosphate).
B. Energy is released from ATP when the
terminal phosphate bond is broken.
C. This release of energy comes from the
chemical change to a state of lower free
energy (stabilizing), not from the phosphate
bonds themselves.
ATP & Glucose
• ATP is not good for storing energy for a
long time.
• Cells only have a small amount of ATP.
• One Glucose can store more than 90
times more energy than one ATP.
• Cells store glucose, and use glucose to
regenerate ATP as needed (cellular
respiration).
*Photosynthesis – process of capturing light
energy from the sun to convert water & CO2
into oxygen and high energy carbohydrates
(food, ex: glucose, starch, & other sugars)
Investigating Photosynthesis
1. Van Helmont’s Experiment – do plant’s
grow by taking material from the soil?
• Found mass of dry soil
• Planted a seedling, watered it at regular
intervals until it grew to a mass of 75kg.
• Found mass of soil to be unchanged
• Concluded the mass the plant gained came
from the water he added.
• Partially correct, but did not determine where
the carbon in the carbohydrate comes from
2. Priestley’s Experiment – oxygen is
produced by plants
• Determined that oxygen was required to keep
a flame lit/burning.
• Removed oxygen from a jar by placing a lit
candle under it until the flame went out.
• Then placed a sprig of mint in the jar (empty
of oxygen)
• After a few days, he found he could relight a
candle in this jar and it would remain lit for a
while!
3. Jan Ingenhousz – light is essential to
photosynthesis!
•
•
Showed the effect observed by Priestley
occurred only when the plant is exposed to
light!
Together, Priestly and Ingenhousz showed
the plants need light and water to produce
oxygen.
I. Photosynthesis Basics – occurs in
the chloroplasts of plants, protists,
and some bacteria cells.
A. Chloroplast – organelle where
photosynthesis occurs
1. Surrounded by 2 membranes.
2. Thylakoid – flattened sac made of
membrane inside the chloroplast
3. Granum – stack of multiple thylakoids
4. Stroma – fluid that surrounds the grana
and fills the chloroplast
B. Pigments – compound that absorbs light
1. Chlorophyll – pigment on thylakoid
membrane
that absorbs light for photosynthesis
• Chlorophyll a – absorbs less blue and more
red light; directly absorbs sunlight
• Chlorophyll b – absorbs more blue and less
red light; helps chlorophyll a absorb light
• Both chlorophyll a and b reflect green light
• Caretenoid – another pigment that absorbs
blue and green light, but not orange; also
helps chlorophyl a absorb light.
C. Photosynthesis is chemically the
opposite of
Respiration.
Respiration
Uses glucose to make ATP
Photosynthesis
1st converts light to ATP
2nd uses ATP to make
glucose
**Equations are also the reverse!
D. NADPH
1. As chlorophyll absorb sunlight, their
electrons become excited (gain a lot of
energy).
2. These high energy electrons require a
special carrier called NADP+
3. NADP+ holds and carries 2 high energy
electrons, along with a H+ ion to become
NADPH
II. Light-Dependent Reactions – first step,
converts sunlight to ATP
1. Occurs on the thylakoid membrane & is
made of PHOTOSYSTEM I and
PHOTOSYTEM II
2.Light is absorbed by chlorophyll in
PHOTOSYSTEM II.
3. The light energy provides electrons for the
Electron Transport Chain (chain of
proteins).
•
•
•
•
Electrons in PHOTOSYSTEM II split water (H+ &
O2 are released).
Some H+ is added to NADP+ and produces
NADPH as electrons move from
PHOTOSYSTEM II to the ETC
The O2 is released to the atmosphere.
A photon of light is absorbed by chlorophyll in
PHOTOSYSTEM I and combines with electrons
from ETC
4. Chemiosmosis
•
•
•
Also happens on the membrane of the thylakoids.
Electrons from PHOTOSYSTEM II provide the
energy for pumping H+ into the thylakoids
Rest of the H+ (from the splitting of water) turn
ATP Synthase proteins (like a turbine) to make
ATP.
*Chemiosmosis and the ETC happen at the
same time!!!
* ATP and NADPH are products of the Light
Reactions
III. Calvin Cycle – the 2nd step of
photosynthesis. Also called the Lightindependent Reactions (used to be called
Dark Reactions), as light does not play
any direct role.
Uses ATP & NADPH to make Glucose
Occurs in the Stroma
Cycles 6 times to make 1 Glucose
Steps of the Calvin Cycle
1. RuBP (carbohydrate in plants) reacts
with NADPH, 6 CO2 (from the
atmosphere), and ATP to make Glucose.
2. Catalyzed by the enzyme Rubisco
3. In the final step, RuBP is remade so the
cycle can occur again.
4. Overall, uses 6 CO2 to make 1 glucose
and cycles 6 times.
Factors Affecting Photosynthesis
1. Water – is a needed raw material;
shortage of water slows or even stops
photosynthesis
2. Temperature – photosynthesis relies on
enzymes, which only function between
0oC and 35oC
3. Intensity of Light – up to a specific level,
as light intensity increases, so does the
rate of photosynthesis
Amoeba Sister Video!
https://www.youtube.com/watch?v=uixA8ZXx0KU
Glycolysis & Fermentation
I. Harvesting Chemical Energy
A. Cellular Respiration – the break down of
organic compounds (food, glucose, etc.) in
cells to make energy, ATP molecules
C6H12O6 + 6O2  6CO2 + 6H2O + Energy
B. Glycolsysis
1. Biochemical pathway that always starts
cellular respiration!!!
2. Does produce a small amount of ATP.
3. Other products can follow two other
pathways, depending on whether oxygen is
present not.
ATP
Glycolysis
Oxygen Absent
Fermentation
(anaerobic)
Oxygen Present
Aerobic
Respiration
ATP
Cellular Respiration Overview
Carbon
Glucose
Electron
(C6H12O2) → Glycolysis → Krebs → Transport →
+
Cycle
Chain
Dioxide
(CO2)
+
Oxygen
Water
(O2)
(H20)
C. Two (2) Types of Cellular Respiration
1. Fermentation– respiration without oxygen
– Can also be called anaerobic respiration
2. Aerobic Respiration – respiration with oxygen
Aerobic = “with
oxygen” like
aerobic workouts
Anaerobic =
“without oxygen”
like weightlifting
workouts
II. Glycolysis
A. Basics of Glycolysis
1.
glyco: sugar
lysis: break up
• Begins to break down glucose & releases a small
amount of energy (ATP)
2. Occurs in the cytoplasm.
3. All types of cellular respiration begin with
glycolysis!!!!!!!!!!
B. Major events in Glycolysis
1. Start with (invest) 1 glucose, 2 NAD+, and 2 ATP
molecules.
2. Glucose, a 6-carbon molecule, is split into 2 PGAL,
or glyceraldehyde-3-phosphate, molecules (each a
3-carbon molecule).
3. Hydrogens are transferred from the 2 PGAL
molecules to the 2 NAD+ molecules. This produces
2 NADH molecules.
4. 4 ATP molecules are then produced (2 ATP overall).
This also produces 2 pyruvic acid molecules.
5. Ends with 2 pyruvic acid, 2 ATP, 2 NADH molecules.
Glycolysis
III. Fermentation
A. Basics
1. Also known as Anaerobic Respiration
2. Does not make any ATP!
3. Does remake NAD+, which goes back through
Glycolysis to make 2 more ATP.
B. 2 Types of Fermentation
1. Alcoholic Fermentation
• A CO2 molecule is removed from each pyruvic
acid, creating acetaldehyde.
• 2 H+ are removed from 2 NADH to make NAD+.
• Acetaldehyde is converted into ethyl alcohol
by gaining the 2 H+.
• NAD+ goes back through glycolysis to make
more ATP.
Figure 9.17a
2 ADP  2 P i
Glucose
2 ATP
Glycolysis
2 Pyruvate
2 NAD 
2 Ethanol
(a) Alcohol fermentation
2 NADH
 2 H
2 CO2
2 Acetaldehyde
2. Lactic Acid Fermentation
• 2 H+ are removed from 2 NADH to make NAD+.
• Pyruvic acid is converted into lactic acid by
gaining the 2 H+.
• NAD+ goes back through glycolysis to make
more ATP.
2 ADP  2 P i
Glucose
2 ATP
Glycolysis
2 NAD 
2 NADH
 2 H
2 Pyruvate
2 Lactate
(b) Lactic acid fermentation
IV. Mitochondria Review
A. Structure
1. Surrounded by a double membrane
2. The 2nd, inner membrane, is highly folded to
increase surface area. Each fold is called a
cristae
3. The very interior of the mitochondria is called
the mitochondrial matrix.
IV. Cellular Respiration (aerobic)
A. Basics
1. Cellular Respiration requires oxygen (O2)!
2. Produces nearly 20 times more ATP than
glycolysis alone.
3. Begins with Glycolysis, followed by the Kreb’s
Cycle, the Electron Transport Chain, and
Chemiosmosis.
B. Glycolysis
1. Converts glucose into 2 pyruvic acids.
2. Makes 2 NADH and a net of 2 ATP.
3. Occurs in the cytoplasm
C. Pyruvic acid is converted into Acetyl CoA.
1. The 2 Pyruvic Acids pass through both
mitochondrial membranes into the
mitochondrial matrix.
2. As this happens, the 2 pyruvic acids reacts with a
molecule called coenzyme A to form Acetyl CoA.
3. 2 NADH’s and CO2 are produced.
D. Kreb’s Cycle
1. Each Acetyl CoA is broken down to make 1 ATP, 3
NADH, and 1 FADH2.
2. 1st product is remade in the last step, so the
Kreb’s Cycle can happen again.
3. Remember, there are 2 Acetyl CoA’s, so the
Kreb’s cycle will happen twice.
4. Our totals are therefore: 2 ATP, 6 NADH, and 2
FADH2.
Acetyl CoA
CoA-SH
NADH
+ H
H2O
1
NAD
8
Oxaloacetate
2
Malate
Citrate
Isocitrate
NAD
Citric
acid
cycle
7
H2O
Fumarate
NADH
3
+ H
CO2
CoA-SH
-Ketoglutarate
4
6
CoA-SH
5
FADH2
NAD
FAD
Succinate
GTP GDP
ADP
ATP
Pi
Succinyl
CoA
NADH
+ H
CO2
E. Electron Transport Chain
1. Occurs across the inner membrane of the
mitochondria (cristae).
2. H+ ions are released from NADH and FADH2 into
the mitochondrial matrix.
3. The electrons in the hydrogen atoms are at a
high energy level!
4. The high energy electrons are passed along a
series of molecules called the Electron Transport
Chain.
E. Electron Transport Chain (cont.)
5. As the electrons move from molecule to
molecule, they lose some of their energy.
6. This energy pumps H+ out of the mitochondrial
matrix, into the space between the two
mitochondrial membranes.
7. A high concentration of H+ builds up in this
space.
Electron Transport Chain
F. Chemiosmosis
1. H+ ions diffuse from the high area of
concentration made in between the 2
mitochondrial membranes to the low are in the
matrix.
2. Specifically the H+ ions move through a protein
called ATP Synthase.
3. As H+ ions move through ATP Synthase, ATP is
made!
4. 32 ATP are made in chemiosmosis.
5. The H+ ions then combine with oxygen to form
water.
Electron Transport Chain
Summary of Cellular Respiration
Total ATP made aerobically: 36 ATP’s
Glycolysis = 2
Kreb’s Cycle = 2
ETC/Chemiosmosis = 32