Download chapter 6 - Biochemical Pathways

BIOCHEMICAL
PATHWAYS
CHAPTERS 6 & 7
All organisms require Energy
AUTOTROPHS
Use basic energy sources to make
energy containing organic materials
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Glucose
Sucrose
Starch
self-feeders-Make their own food
AUTOTROPHS
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Photosynthetic autotrophs
Photosynthesis
 Use light energy & CO2
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Chemosynthetic autotrophs
chemosynthesis
 Use chemicals (e.g N, S, CHO, Pn) & CO2
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HETEROTROPHS
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Obtain energy by breaking down the organic
molecules they consume.
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Cannot derive energy directly from light or from
inorganic chemicals, and so must feed on other
life-forms.
ATP –
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adenosine
triphosphate
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A-----P-----P-----P
High energy
phosphate bond
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break off a
phosphate 
energy is released
add a phosphate 
energy is stored
ATP structure
Adenine,
 ribose sugar,
 3 phosphates
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aerobic cellular respiration - in
one sentence
convert stable
glucose molecules
to ATP, CO2 + H2O
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AEROBIC CELLULAR
RESPIRATION
C6H12O6 +6O2  6CO2 + 6H2O+ energy (ATP + heat)
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Composed of many steps:
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biochemical pathway
Reactants: Glucose ingested & O2
Products: CO2 & H2O
Where in a cell
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Eukaryotes: cytoplasm & mitochondria
Prokaryotes: cytoplasm & cell membrane
ACR involves Electron Transfer
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Oxidation / Reduction
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Oxidation
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energy containing electrons are transferred from one molecule to
another
large molecule losses eGlucose is oxidized- pulled apart
Reduction: Gain of e
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e- carriers /coenzymes pick up e and H ions
Nicotinamide adenine dinucleotide (NAD+)
Flavin adenine dinucleotide (FAD)
O2 is reduced– final e- acceptor
step one – glycolysis (fig 6.4; 6.7)
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occurs in the
cytoplasm
Glucose (6C) -> 2
pyruvic acid (3C)
2ATP used
Generates 4 ATPs
NAD carries e- & H+
Transition Step to the Krebs Cycle
Aerobic
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PA is converted to Acetyl CoA & CO2
Yields NADH
Occurs in the mitochondria
NAD
CO2, NADH
Pyruvate (3 C)
Acetyl-CoA (2 C)
Pyruvate dehydrogenase
step two - Krebs cycle (Figs 6.5; 6.8)
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Named after Hans Krebs
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A British biochemist
Series of biochemical
reactions that are catalyzed by
enzymes
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Completes break down of glucose
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Hydrogen and electrons are
stripped and loaded onto
NAD+ and FAD to produce
NADH and FADH2
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CO2 released as a byproduct
1 ATP per pyruvic acid
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step three –
electron transport system
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Occurs in the inner mitochondrial membrane
Electron carriers loaded with electrons and protons from the Kreb’s
cycle move to this chain - like a “series of steps (staircase)”
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NADH & FADH2 transfer electrons to other carriers
Oxygen final electron acceptor: forms water
Energy released used to synthesize ATP
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ADP + P = ATP
Oxidative phosphorylation
Enzyme is ATP synthase
Net 32 ATP
Electron Transport System
total ATP’s - 36
glycolysis - 2
 krebs cycle - 2
 electron transport system -32
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anaerobic cellular respiration
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Strict anaerobes do not use O2 as
terminal e- acceptor.
Use the following instead
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Sulfur; N or an organic molecule
ATP yield lower than in aerobes
fermentation 
Anaerobic pathway
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no krebs cycle or ETS
net ATP = 1 or 2
end products
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Alcoholic fermentation: ethanol and CO2 (in yeast )
Lactic Acid fermentation: lactic acid (in bacteria)
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Aerobic cellular
respiration vs
Anaerobic cellular
respiration
Chapter 7: photosynthesis
PHOTOSYNTHESIS
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Is the biochemical process by which plants capture
energy from sunlight and store it in carbohydrates
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Converts light energy to chemical bond energy
Fixes carbon from CO2
Biochemical pathway.
Light energy + 6CO2 + 12H2O -> C6H12O6 + 6O2 + 6H2O
Reactants =
 Products =
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Chapter 7: photosynthesis
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occurs in chloroplasts in
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Eukaryotes
Occurs in cell membranes in
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prokaryotes
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step 1 - light capturing
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occurs in the chloroplasts
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chlorophyll absorbs light energy
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In Grana or Thylakoid membranes
Chlorophyll a & b
e- get excited due to added
energy
step 2 - light dependent
reaction: Light Reaction
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Occurs in Grana
Excited electrons used for
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Making ATP : oxidative phosphorylation
Enzymes split H2O; e- and H+
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O2 released
NADP used as a coenzyme
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ATP, NADPH go into the Stroma
step 3 - light independent reaction: Dark
Reaction/Calvin cycle
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Occurs in the stroma
ATP donates energy to link C, H, O
NADPH donates hydrogen
CO2 used as a carbon source
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Linked to 5 carbon starter molecules: Ribulose( 5-C sugar)
Enzyme is ribulose biphosphate carboxylase (RuBisCo)
Product is 2 molecules of glyceraldehyde –3 Phosphate
[PGAL]
Surplus G-3-P used to make glucose or other
molecules (proteins, nucleic acids, etc)
Summary
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Aerobic Respiration
Anaerobic Respiration
Fermentation
Glycolysis
Krebs Cycle
Electron transport system
Light and dark reactions of photosynthesis
Autotrophs
Heterotrophs
Chemosynthesis