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CHAPTER 6 PHOTOSYNTHESIS

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Title: CHAPTER 6 PHOTOSYNTHESIS


1
CHAPTER 6PHOTOSYNTHESIS
  • BIOLOGY LECTURE

2
ENERGY 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

3
ENERGY 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

4
AUTOTROPHS
  • 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

5
HETEROTROPHS
  • 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

6
All fuel originates with the Autotrophs
7
Energy 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

8
How 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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10
Energy 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

11
Do 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?

12
LIGHT 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

13
Chloroplasts
  • Inner/outer membrane
  • Thylakoids flattened sacs where photosynthesis
    takes place
  • Granum (pl. grana) stack of thylakoids
  • Stroma liquid solution that surrounds the
    thylakoids

14
CHLOROPLASTS IN PLANT CELL
15
Light
  • 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

16
Chloroplast 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

17
Chloroplast 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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21
Do 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?

22
Electron 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

23
Electron 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)

24
Electron 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

26
Electron Transport Chain
27
E. Biochemical pathways series of
biochemical reactions
28
Chemiosmosis - 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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30
Calvin 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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32
Photosynthesis 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

33
Photosynthesis Equation
  • 6CO2 6H2O Light Energy C6H12O6 6O2

34
Do 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?

35
C3 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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C3 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

38
C4 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

39
CAM 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

40
Rate 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

41
Rate 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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44
Cellular Respiration
  • Chapter 7

45
Cellular 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

47
Glycolysis
  1. 2 phos. groups attach to glucose from 2 ATPs to
    form a new 6 C compound
  2. 6 C comp. splits into 2 PGAL molecules (3 C)
  3. 2 phos. groups attach to PGALs and PGALs
    oxidized. NAD reduced to NADH.
  4. Phos. groups removed and combine with ADPs ? ATP.
    2 pyruvic acid molecules formed.

48
Do Now
  • 1. What is cellular respiration?
  • 2. What is anaerobic respiration?
  • 3. What is aerobic respiration?
  • 4. What is glycolysis?

49
Fermentation
  • 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

50
Lactic Acid Fermentation
  • Enzyme converts pyruvic acid into lactic acid
  • Some bacteria fungi do this ? yogurt,
  • cheese
  • Animal cells (Muscle cells w/o oxygen)

51
Lactic 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

52
Alcoholic Fermentation
  • Plants and yeast
  • Pyruvic acid is broken down and a CO2 is removed,
    the resulting 2C compound is ethyl alcohol.

53
Alcoholic 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

54
Anaerobic 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!!

55
Do 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?

56
Aerobic 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

57
Aerobic 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

58
Coenzyme 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

59
Krebs 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

60
Energy 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

61
Electron 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)

62
Electron Transport Chain
63
Energy
  • 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

64
Respiration Equation
  • C6H12O6 6O2 6CO2 6H2O Energy
  • This equation is the opposite of the equation for
    Photosynthesis!

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