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Cellular Respiration + Photosynthesis - Coggle Diagram
Cellular Respiration + Photosynthesis
Photosynthesis (Ch.10)
Light Reactions
Photosystems
photosystem = reaction-center complex surrounded by light-harvesting complexes
Structure
reaction-center complex
Organized protein association
special pair of chlorophyll a molecules
pair transfers electrons to primary electron receptor
primary electron receptor
light-harvesting complex
Contains pigment molecules bound to proteins
Photosystem I
reaction-center chlorophyll a = p700
Photosystem II
reaction-center chlorophyll a = p680
Linear Electron Flow
Flow of electrons thru photosystems/components in thylakoid membrane
8 Steps
electrons passed to psI via ETC, more h+ pumped into thylakoid space
proton gradient used to make ATP (chemiosmosis)
Water split, electrons supplied to psII to fill in missing space; h+ released to thylakoid space
light energy transferred to psI, electron in p700 chlorophyll a pair excited, transferred to psI primary electron receptor
electron transferred to primary electron receptor
electrons passed down 2nd ETC
electron in psII excited to higher level
NADP+ reduced to NADPH using 2 electrons
Excitation of Chlorophyll
Light energy absorbed cannot disappear
Photon absorbed = excites electron to higher-energy orbital
Electron returns to normal orbital
Heat (+ sometimes light) released
release of light = flourescence
Cyclic Electron Flow
Uses photosystem I but not II
No NADPH production, no oxygen release
Makes ATP
Photosynthetic Pigments
Pigments = substances that absorb light
Color of object = wavelength most reflected
Measuring
Spectrophotometer = measures ability to absorb wavelengths
Absorption spectrum = graph plotting absorption vs wavelength
Chloroplasts
Chlorophyll a = key light-capturing pigment
action spectrum confirms violet-blue + red light best for photosynthesis
Chlorophyll b
Accessory pigment; broadens amount of light that can drive photosynthesis
Other Pigments
Carotenoids
Absorb violet + blue-green light
Function = photoprotection (absorb/dissipate excess light energy)
Chemiosmosis in Chloroplasts vs Mitochondria
ETC pumps protons across membrane, creates gradient
ATP synthase couples diffusion w/ phosphorylation of ADP
Chloroplasts
Electrons come from water
Use light energy instead of water
Mitochondria
Electrons come from food
Need food to make ATP
Nature of Sunlight
Light = electromagnetic energy/radiation
Electromagnetic Spectrum = entire range of wavelength variation
Visible light = Detected as color by humans
~380nm to 740nm
Wavelength = distance between crests of electromagnetic waves
Photons = intangible "particles" of light
Have fixed energy quantities
Amount inverse to wavelength (shorter = more energy)
The Calvin Cycle
Location = stroma
Anabolic
3 cycles = Produces 1 G3P
Phases
Reduction
3-phosphoglycerate receives phosphate, gets reduced + loses phosphate, becomes G3P
Regeneration
C skeletons of 5 G3P molecules made into RuBP
Requires 3 ATP
Carbon Fixation
C attaches to RuBP (catalyzed by rubisco)
Products = 2 3-phosphoglycerate
Conversion of Light Energy
Tracking Atoms
General equation = 6CO2 + 6H2O + light energy --> C6H12O6 + 6O2
Splitting of Water
Photosynthesis splits water
O2 = byproduct
Photosynthesis = redox process
Electrons + Hydrogen ions transferred from water to CO2
CO2 reduced to sugar
Two Stages
Light reactions
Convert light energy to chemical energy
Water split, O2 as byproduct
light drives electrons + H ions to NADP+
NADP+ reduced to NADPH (electron pair added + H ion)
ATP created via photophosphorylation
Calvin Cycle
Produces sugar
Occurs in stroma
Starts w/ carbon fixation (incorporating C into organic compounds)
reduces fixed C to carbohydrates
Does not require direct light energy
Chloroplasts
Found mainly mesophyll (interior leaf tissue) cells
CO2 enters, O2 leaves via stomata (pores)
Chloroplast structure
Membrane system in stroma
Made of thylakoids (sacs)
Thylakoid stacks = grana
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Chlorophyll = green pigment inside thylakoid membranes
Absorbs light energy, drives photosynthesis
2 membranes surrounding stroma (fluid)
Alternative Mechanisms
C4 Plants = Have C fixation method that forms 4-C compound
Photosynthesis begins in mesophyll cells
Completed in bundle-sheath cells (cells arranged in tightly-packed sheaths
Steps
oxaloacetate exported to bundle-sheath cells
Enzyme releases CO2 from 4-C compounds
CO2 refixed to organic compounds in calvin cycle
regenerates pyruvate
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1st carried out by enzyme (PEP carboxylase)
Adds CO2 to PEP, forms 4-C oxaloacetate
CAM Plants
Open stomata at night
crassulacean acid metabolism (CAM)
Stores acids until light reactions can supply ATP + NADPH
Photorespiration
Rubisco binds O2 instead of CO2
Uses ATP
Produces no sugar
Costly; other methods available for minimizing photorespiration
Occurs in light, consumes O2, produces CO2
Photosynthesis feeds Biosphere
Photosynthesis = Process of converting light energy into chemical energy in plants
Nourishes directly and indirectly
Autotrophs
Make their own food; "producers"
Plants = photoautotrophs (use light as energy)
Heterotrophs
Live on compounds created by other organisms; "consumers"
Decomposers = eat remains + organic litter
Review
Photosynthesis Steps
Light reactions
capture solar energy, use to make ATP
transfers electrons from water to NADP+ (makes NADPH)
Calvin Cycle
Uses ATP + NADPH to produce sugar from CO2
Photosynthetic Products
Enzymes convert GP3 to other compounds
~50% organic products used as fuel
Carbs transported out of leaves as sucrose
Used in synthesis + cellular respiration
Cellular Respiration (Ch.9)
Citric Acid Cycle
Oxidation of pyruvate
pyruvate converted to acetyl CoA
Steps
Electrons transferred to NAD+, converts it to NADH
coenzyme A attached to 2-C intermediate, forms acetyl CoA
carboxyl group fully oxidized, released as CO2
Citric acid cycle
Generates 1 ATP per turn via substrate-level phosphorylation
Most chemical energy transferred to NAD+ and FAD
NADH and FADH2 shuttle electrons into ETC
8 steps, each catalyzed by enzyme
Another CO2 lost, NAD+ reduced to NADH, remaining molecule attached to coenzyme a
GTP formed
isocitrate oxidized, NAD+ reduced to NADH, CO2 released
2 hydrogen transferred to FAD, forms FADH2
citrate converted to isocitrate
Acetyl CoA adds its 2 C group to oxaloacetate, produces citrate
Water added, rearranges bonds in substrate
substrate oxidized, reduces NAD+ to NADH, oxaloacetate regenerated
Oxidative Phosphorylation
Chemiosmosis
ATP synthase = enzyme that makes ATP
Uses energy of ion gradient to power ATP synthesis (chemiosmosis)
ATP production
Energy flow
glucose -> NADH -> ETC ->protonmotive force ->ATP
Each NADH contributes to generation of ~3 ATP
Electron transport pathway
ETC = collection of molecules embedded in inner membrane of mitochondrion
Most = proteins labeled I thru IV
Glycolysis (sugar splitting)
2 phases
Energy investment phase
Cell uses ATP
energy payoff phase
ATP produced by substrate-level phosphorylation
NAD+ reduced to NADH
Net energy yield = 2 ATP, 2 NADH
Catabolic Pathways
Catabolic Pathways
Compounds that can participate in exergonic reactions can be fuels
Aerobic Respiration
Requires oxygen, most efficient method
Anaerobic respiration = uses reactants other than oxygen to harvest chemical energy
Cellular Respiration = includes both aerobic and anaerobic
Fermentation
Partial breakdown of sugars/other fuels
No oxygen required
Redox Reactions = when electron(s) transfer between molecules in reactions
Principle of Redox
Reduction = gaining of electrons
Reducing agent = electron donor
Oxidation = loss of a substance
Oxidizing agent = electron remover
Oxidation During Cellular Respiration
Respiration = oxidation of glucose + other molecules
Stepwise Energy Harvest
Glucose broken down in series of steps
Each step catalyzed by enzyme
Stages of Cellular Respiration
Pyruvate Oxidation + Citric Acid Cycle
Pyruvate oxidized to acetyl CoA
Enters citric acid cycle
Citric Acid Cycle
Breakdown of glucose to carbon dioxide completed
Oxidative Phosphorylation
Electrons travel down ETC
Combined with oxygen + H ions, forms water
Energy from each step used to make ATP
Glycolysis
Occurs in cytosol
Breaks glucose into 2 pyruvate
Fermentation
Comparing to Aerobic + Anaerobic Respiration
Differences
NO ETC in fermentation
ETC in cellular respiration
Fermentation yields 2 ATP
Cellular respiration yields up to 32 ATP
Organisms
Obligate anaerobes
can only ferment or carry out anaerobic respiration
Facultative anaerobes
Can survive using fermentation or respiration
Similarities
All 3 use glycolysis, have net production of 2 ATP, and have NAD+ as oxidizing agent during glycolysis
Evolutionary Significance of Glycolysis
Thought to be used before oxygen present in atmosphere
Evidence
Does not require membrane-bound organelles in eukaryotic cells
Oldest bacteria fossils dated to before oxygen was present
Widespread
Types of Fermentation
Alcohol
pyruvate converted to ethanol in 2 steps
CO2 released from pyruvate
Pyruvate converted to acetaldehyde
acetaldehyde reduced by NADH to ethanol
Lactic acid
pyruvate reduced directly by NADH, forms lactate
no CO2 release
Other Metabolic Pathways
Biosynthesis (anabolic pathways)
Food must provide C skeletons required for molecule synthesis
Some compounds diverted to anabolic pathways
Example: synthesis of amino acids
consumes ATP
Feedback Mechanisms
feedback inhibition
product of anabolic process inhibits catalysis in an early step of the process; supply and demand
cell controls catabolism
respiration speeds up if ATP concentration low
respiration slows if concentration high
Example: pace regulation of phosphofructokinase catalysis
Versatility of Catabolism
Glycolysis can accept various carbs for catabolism
Proteins also used for fuel; must be broken down to amino acids
amino groups must be removed (deamination)
Can harvest energy from fats
beta oxidation = breaks down fatty acids to 2-C fragments
enter citric acid cycle as acetyl coa
NADH and FADH2 produced, can enter ETC