Title: CHAPTER 6 PHOTOSYNTHESIS
1CHAPTER 6PHOTOSYNTHESIS
2ENERGY FOR LIFE PROCESS
- All organisms
- require a constant supply
- of energy
- Energy does not recycle
- almost all energy is from
- the sun
- 3. Organisms capture the energy of light and
store it in organic compounds
3ENERGY FOR LIFE PROCESS
- Classifying Organisms By How They Get Their
Energy - Autotrophs manufacture their
- own food from inorganic
- substances and energy
- Heterotrophs cannot
- manufacture their own
- organic compounds from
- inorganic substances
4AUTOTROPHS
- MAKE FOOD
- Use photosynthesis to convert light energy from
the sun into chemical energy -
- They store the chemical energy in organic
compounds (carbohydrates) -
- Examples are plants, algae, and cyanobacteria
5HETEROTROPHS
- Take in food
- They eat autotrophs or other heterotrophs
- A caterpillar (H) feeds on grass (A)
- A bird (H) feeds on the caterpillar (H)
- Examples are animals, most bacteria, fungi, and
protozoa
6All fuel originates with the Autotrophs
7Energy Transfer Compounds
- Photosynthesis a biochemical pathway that
converts solar energy to chemical energy (STORE
ENERGY FOOD) - Autotrophs manufacture organic compounds from
carbon dioxide and water and oxygen is released -
- 6CO2 6H2O LIGHT C6H12O6 6O2
-
-
-
8How Do We Get Energy?
- Cellular Respiration A biochemical pathway
that breaks down chemical energy for use by the
cell (RELEASE ENERGY) - In both autotrophs and heterotrophs, organic
compounds are combined with oxygen to produce
ATP, carbon dioxide and water - C6H12O6 6O2 6CO2 6H2O ENERGY
(ATP) -
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10Energy Transfer Compounds
- Adenosine Triphosphate molecule of stored
energy - Energy stored in bonds between phosphate
(A M P P P) - AMP, ADP, ATP
- Nicotinamide Adenine Dinucleotide Phosphate -
molecule that transports energy - NADP to NADPH
11Do Now
- 1. What is the difference between autotrophs and
heterotrophs? - 2. What is photosynthesis?
- 3. What is cellular respiration?
- 4. What are the 2 energy transfer compounds we
talked about?
12LIGHT ABSORPTION IN CHLOROPLASTS
- Chloroplasts - membrane bound organelles that
contain - 1. the pigment chlorophyll
- 2. enzymes for photosynthesis
- Both light and dark reactions take place here
13Chloroplasts
- Inner/outer membrane
- Thylakoids flattened sacs where photosynthesis
takes place - Granum (pl. grana) stack of thylakoids
- Stroma liquid solution that surrounds the
thylakoids
14CHLOROPLASTS IN PLANT CELL
15Light
- A. White light composed of visible spectrum
- ROY G BIV
- B. Light travels in energy waves
- C. Wavelength (?) determines color of light
- D. UV ? violet ? red
- Short ? ? Long ?
- E. Pigment compound that absorbs light
- F. Ex. Green pigment absorbs colors other than
green reflects/transmits green
16Chloroplast Pigments
- There are several different
- pigments in the thylakoid
- membranes
- Chlorophyll is a pigment
- that absorbs red and blue
- light and reflects green light
- Chlorophyll a is directly involved with the light
reaction -
17Chloroplast Pigments
- Accessory pigments trap wavelengths of light that
can not be absorbed by chlorophyll a (help
capture more light) - a. Chlorophyll b also reflects green, but
absorbs more blue than red - b. Carotenoids reflect orange, yellow, and
brown and absorbs green and blue - c. Phycobilins reflect violet blue and
absorb orange, brown and green
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21Do Now
- 1. What important process occurs in chloroplasts?
- 2. What are the flattened sacs in chloroplasts
called? - 3. What is a pigment and what important pigment
is found in the chloroplast?
22Electron Transport Chain (ETC)
- Photosystem a cluster of pigment molecules found
in the thylakoid membrane - 2 Photosystems each has different roles in
photosynthesis - Photosystem I
- Photosystem II
23Electron Transport Chain (ETC)
- Light Reaction Photosystem II
- 1. Light energy absorbed by pigments and
transferred to chlorophyl a . Electron from
chlorophyl a gets excited enters a higher
energy level - 2. Electron leaves chlorophyl a enters
primary e- acceptor - 3. Primary e- acceptor transfers e- to series
of molecules (electron transport chain) loses
Energy (E used to move p into thylakoid) -
-
24Electron Transport Chain (ETC)
- Light Reaction Photosystem I
- 4. Light is absorbed by photosystem I, electrons
move from chlorophyll a molecules to another
primary electron acceptor. These e- are replaced
with those from photosystem II - 5. e- used to make NADPH from NADP (NADP
H ?NADPH)
25 Waters role
- e- from splitting of H2O replaces lost e- in
photosystem II - 2 H2O ? 4 H 4 e- O2
- O2 leaves plant or used for cellular respiration
- H stays in thylakoid ? concentration gradient
26Electron Transport Chain
27 E. Biochemical pathways series of
biochemical reactions
28Chemiosmosis - Make ATP
- Concentration gradient causes protons (H) to
move from thylakoid (high conc) to stroma (low
conc) - ATP synthase uses movement of protons/change in
potential energy to make ATP - Converts potential E to chemical E
- ATP synthase (multifunctional protein)
- Carrier protein carries protons across
thylakoid membrane - Enzyme catalyzes synthesis of ATP from ADP
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30Calvin cycle
- Uses ATP NADPH from the light reaction as
energy to make organic compounds - Carbon from CO2 fixed into organic compounds
- Each cycle uses 3 ATP 2 NADPH
- Occurs in stroma of chloroplast
- Called the Dark Reaction
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32Photosynthesis Balance Sheet
- 3 turns of the Calvin Cycle are required to
produce each molecule of PGAL - This uses up 9 molecules of ATP and 6 molecules
of NADPH - Most of the molecules made in the Calvin Cycle
are built up into - Amino Acids
- Lipids
- Carbohydrates
- Heterotrophs use the energy in these organic
compounds for living
33Photosynthesis Equation
- 6CO2 6H2O Light Energy C6H12O6 6O2
34Do Now
- 1. What is a photosystem?
- 2. What is the electron transport chain?
- 3. What is the purpose of the Calvin cycle?
- 4. What is the equation for photosynthesis?
35C3 Plants Alternative Pathways
- Plants that use Calvin cycle are called C3 plants
because they fix CO2 into a 3C compound PGA - Stomata (pl.) - small pores on the underside of a
leaf where water, CO2, and O2 pass through - Plants can partially close stomata to minimize
water loss - Plants open stomata during day close _at_ night
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37C3 Plants Alternative Pathways
- When stomata close up, CO2 cant get into the
plant and O2 cant get out of the plant - This inhibits carbon fixation by the Calvin Cycle
in the plant - Plants have to find other ways
- to fix carbon and make food
38C4 Plants
- Partially close stomata during hottest part of
day - Certain cells have enzymes that can fix CO2 into
4C compound even when CO2?, O2? - Lose ½ the amount of water as C3 plants but
produce the same amount of carbs - Ex. Corn, sugar cane, crab grass
39CAM Plants
- Open stomata _at_ night
- close during day
- B/C of this CO2 enters when colder ? slower
growth, less water loss - Fix CO2 into a variety of diff. C comp.
- at night, use for Calvin Cycle during day
- Cactuses, pineapple, and others with different
adaptations to hot climate
40Rate of Photosynthesis
- Effected by the Environment
- Light Intensity as light increases rate of
photosynthesis increases and then levels off when
available electrons are already excited - CO2 as CO2 levels increase rate of
photosynthesis increases and then levels off - Temperature raising the temp. speeds up
chemical reactions and increases the rate of
photosynthesis, but soon the temp gets too high
and photosynthesis rate decreases
41Rate of photosynthesis
- 1. Light, CO2 eventually level off _at_ maximum
- 2. Temperature reach a maximum decrease
- Enzymes begin to become unstable ineffective
- Stomata close limit water loss CO2 entry
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44Cellular Respiration
45Cellular Respiration Overview
- A. Releases energy from organic molecules
(sugars) to make ATP (available cell energy) - B. Done by autotrophs and heterotrophs
- C. Aerobic respiration organic molecules broken
down with oxygen yields a lot of ATP - D. Anaerobic respiration organic molecules
broken down without oxygen little or no ATP. - E. Living organisms could specialize in one, or
switch depending on available oxygen.
46- Glycolysis
- All organisms begin respiration with glycolysis
(to break glucose) small amount of energy (net
2 ATP produced), but makes energy carrying
(electron) molecule NADH and pyruvic acid
(organic product) - Anaerobic in nature
- Products can either be fermented (recycle NADH)
or aerobically broken (lots of ATP) - Takes place in cytoplasm
- Reactions in the biochemical pathway
47Glycolysis
- 2 phos. groups attach to glucose from 2 ATPs to
form a new 6 C compound - 6 C comp. splits into 2 PGAL molecules (3 C)
- 2 phos. groups attach to PGALs and PGALs
oxidized. NAD reduced to NADH. - Phos. groups removed and combine with ADPs ? ATP.
2 pyruvic acid molecules formed.
48Do Now
- 1. What is cellular respiration?
- 2. What is anaerobic respiration?
- 3. What is aerobic respiration?
- 4. What is glycolysis?
49Fermentation
- Performed in the absence of oxygen
- Makes no ATP, occurs in cytoplasm
- Regenerates NAD which can keep glycolysis going
- Types
- 1. Lactic Acid
- 2. Ethyl alcohol
50Lactic Acid Fermentation
- Enzyme converts pyruvic acid into lactic acid
- Some bacteria fungi do this ? yogurt,
- cheese
- Animal cells (Muscle cells w/o oxygen)
51Lactic Acid Fermentation
- Occurs when you are
- exercising strenuously
- Muscle cells use up oxygen
- faster than you can breathe it in
- Muscle cells switch from aerobic respiration to
lactic acid fermentation - Can make muscles sore and cause cramping
- Eventually the lactic acid gets turned back into
pyruvate in the liver
52Alcoholic Fermentation
- Plants and yeast
- Pyruvic acid is broken down and a CO2 is removed,
the resulting 2C compound is ethyl alcohol.
53Alcoholic Fermentation
- The basis of the beer
- and wine industry
- Yeast cells are added
- to either crushed grapes
- or grains
- They perform fermentation to produce ethyl
alcohol - Regular wine CO2 is released
- Beer and champagne CO2 is retained
54Anaerobic Energy Yield
- When glucose is broken down anaerobically, only 2
ATPs are produced during glycolysis - Most of the energy is still trapped in the
pyruvic acid - The efficiency of energy transfer is very low at
3.5 - This is OK for small, unicellular organisms, but
larger organisms need more energy!!
55Do Now
- 1. Is fermentation done in the presence or
absence of oxygen? - 2. What are the 2 types of fermentation we talked
about? - 3. Is fermentation efficient for energy transfer?
56Aerobic Respiration
- If oxygen is present, pyruvic acid goes from
glycolysis to aerobic respiration - Aerobic respiration produces 20 X as much ATP
- 2 major stages
- 1. Krebs Cycle small amount of ATP
- 2. Electron transport chain large amount of ATP
57Aerobic Respiration
- Occurs in mitochondria of eukaryotes (cytoplasm
in prokaryotes) - Outer membrane
- Inner membrane (cristae folds)
- Matrix inside inner membrane contains enzymes
needed to catalyze the Krebs Cycle
58Coenzyme A/Acetyl CoA
- 1. As Pyruvic acid enters the mitochondrial
matrix it bonds with Coenzyme A (CoA) and
produces CO2 Acetyl CoA - a.NAD ? NADH
- 2. Acetyl CoA begins the Krebs cycle
59Krebs CycleBreaks down Acetyl CoA producing
CO2, H atoms, and ATP
- 1. Acetyl CoA rxts w/ oxaloacetic acid ? CoA
citric acid - 2. 1 glucose does 2 cycles
- 3. Krebs cycle produces 2 CO2, 3 NADH, 1 FADH2
and 1 ATP per cycle - (x2 b/c 2 cycles)
- 4. NADH FADH2 used in ETC
60Energy So Far
- Bulk of the energy released by the oxidation of
glucose is still not in form of ATP - This will require the NADH and FADH2 that we have
made so far - Glycolysis 2 NADH
- Convert Pyruvic Acid to Acetyl CoA 2 NADH
- Krebs Cycle 6 NADH, and 2 FADH2
- These 10 NADH and 2 FADH2 molecules will enter
the electron transport chain and make ATP
61Electron Transport Chain
- 1. Electrons for the ETC are supplied by the
splitting of NADH and FADH2 - 2. Protons from NADH and FADH2 are pumped through
the inner mitochondrial membrane away from the
matrix by the ETC - 3. The pumping of protons across the membrane
creates a conc. gradient which is then used to
make ATP by ATP synthase. - 4. Final e- acceptor is O2. (H20 is produced)
62Electron Transport Chain
63Energy
- 1. Converted in the ETC
- a. 1 NADH 3 ATP
- b.1 FADH2 2 ATP
- 2.
- a. 38 ATP (12 kcal)/Glucose (686 kcal)
- b. Aerobic Efficiency 66
64Respiration Equation
- C6H12O6 6O2 6CO2 6H2O Energy
- This equation is the opposite of the equation for
Photosynthesis!
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