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LG 3: Photosynthesis & Cellular Respiration

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Alexa Ayala

on 30 May 2016

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Transcript of LG 3: Photosynthesis & Cellular Respiration

using NADH to convert pyruvate to lactate (lactic acid)
NAD+ is reused to continue the cycle








occurs when glycolysis exceeds oxygen supply, therefore in oxygen debt
Cellular Respiration Review
Aerobic Cellular Respiration
Fermentation
Photosynthesis
Photosynthesis


Photosynthesis Review
Chloroplasts
Structure and Function
LG 3: Cellular Respiration & Photosynthesis
Chapter 5
Mitochondria
Characteristics of Mitochondria
in eukaryotic organisms

convert glucose into energy

bound by two membranes
Structure of the Mitochondria
matrix
: fluid-filled space of the inner membrane
contains substances needed to break down carbohydrates
cristae
: folds of the inner membrane that provide surface area for ATP production
Metabolism
all the chemical reactions that occur within a cell to support and sustain functions
anabolic
: make larger molecules from smaller ones, requiring energy
catabolic
: break down large molecules into small ones, releasing energy
started by enzymes
Oxidation versus Reduction
oxidation
: lose electrons
reduction
: gain electrons
more energy in reduced form, therefore have
reducing power
glucose
Energy Pathways
Aerobic versus Anaerobic
1. creatine phosphate = _______________

2. cellular respiration = _________________

3. fermentation = ___________________
Releasing Energy Because...
oxidation reaction
transfer of electrons from glucose to oxygen

energy is ATP
Steps of Cellular Respiration
Glycolysis
occurs in the cytoplasm
anaerobic
occurs in all living cells
generates pyruvate and small amount of ATP
1. glucose splits into two intermediate three-carbon molecules
• uses 2 ATP -> 2 ADP energy

2. two intermediate three-carbon molecules convert to two pyruvate
• converts 4 ADP -> 4 ATP
• uses 2 NAD+ -> 2NADH
Glycolysis
Energy Production
glycolysis generates 2 ATP overall
used 2 ATP at first, but then generates 4 ATP
Kreb's Cycle Prepartion
if oxygen is present, pyruvate proceeds to mitochondria's membrane
1. each pyruvate loses a carbon atom (as CO2)
2. leftover two-carbon molecule bonds to Coenzyme A (CoA)
• uses NAD+ -> NADH
3. now called acetyl CoA enters Kreb's Cycle in mitochondria's matrix
Kreb's Cycle
1. a 4-carbon molecule accepts the two acetyl CoA (2-carbon) to make a 6-carbon molecule
2. this 6-C molecule loses a carbon in the form of CO2
twice
• 3 NAD+ ---> 3NADH
• 1 ADP+P ---> 1 ATP
• FAD ---> FADH2
Energy Production
1. glycolysis = _________

2. Kreb's preparation = ________

3. Kreb's cycle =
____________________________
Electron Transport Chain
high energy electrons are passed to a chain of electron-carrying molecules that are attached to the inner membrane of the mitochondria
when they pass from carrier to carrier, energy is released in small amounts
this energy is used to pump hydrogen ions across the membrane from the matrix to the intermembrane space, creating a concentration gradient
an enzyme called ATP synthase uses the energy from the concentration gradient to produce ATP
Oxygen's Role
at the end of the ETC, oxygen is present to receive electrons
Electron Transport Chain
Energy Production
1. glycolysis = _________

2. Kreb's preparation = ___________

3. Kreb's cycle =
______________________________

4. Electron Transport Chain =
32 ATP


After glycolysis, if there is no oxygen available*, pyruvate enters fermentation.
*Why might there be no oxygen?
Anaerobic Cellular Respiration versus Aerobic Cellular Respiration
although it includes an electron transport system and a concentration gradient (for ATP production), there is no oxygen to be the final electron acceptor
instead uses sulfate, nitrate, or carbon dioxide

not as efficient (makes less ATP)
Fermentation
metabolic pathway that includes glycolysis and one or two reactions in which NADH is oxidized to NAD+ by reducing pyruvate to other compounds
Two Types of Fermentation
1. Lactate fermentation

2. Ethanol fermentation
Lactate Fermentation
Ethanol Fermentation
1. converts pyruvate into a two-carbon compound
loses the carbon to CO2

2. two-carbon compound uses NADH ---> NAD+ to produce ethanol
yeasts for bread and beverages
Using Ethanol Fermentation
ethanol is a waste to organisms, but can be used for other purposes
lamp fuel
internal combustion

combustion of ethanol = CO2 emission
but also reduces the amount of carbon monoxide in exhaust and eliminates the release of other substances into the environment

Not quite the opposite....
Structure
two membranes: inner and outer
stroma
: fluid in the inner space of a chloroplast
contains proteins and other chemicals used in the synthesis of carbohydrates
thylakoids
: interconnected flattened sacs
grana
: stacks of thylakoids
Chlorophyll
located in the thylakoid membrane
pigment that absorbs certain wavelengths of visible light, which reflects green
traps light energy and passes it on to other chemicals, which use the energy to synthesize glucose
photosystems
: groups of pigments in thylakoid membrane

Types of Pigments
1. chlorophyll
a
absorbs violet, blue and red
reflects green, yellow and orange

2. chlorophyll b
absorbs blue and orange
reflects green and yellow

3. beta carotene
absorbs blue and green
reflects red, orange, and yellow
Absorbance Spectrum versus Action Spectrum
Two Reactions
photo - synthesis
1. light-dependent reactions

2. light-independent reactions
Light-Dependent Reactions
solar energy is trapped and used to generate ATP and NADPH
both have high reducing power

involves all the pigments
chlorophyll a
chlorophyll b
beta-carotenoids
occurs in thylakoid membrane's photosystems
Light-Independent Reactions
occurs in stroma

energy of ATP and the reducing power of NADPH are used to reduce carbon dioxide to make glucose

glucose is then converted into starch for storage
Photosynthesis Steps
3. the electron from the electron-acceptor molecule is transferred along an electron transport system
releases small amount of energy at each jump which is used to push H+ from stroma, across the thylakoid membrane, and into the thylakoid space (more in thylakoid space than in stroma)
creates a concentration gradient used to generate ATP


4. simultaneously, light energy is being absorbed in
photosystem I
, which excites an electron at it's reaction center, which then goes through another electron transport chain
the lost electron is replaced by the electron from
photosystem II

5. the electron received from photosystem I is used to reduce NADP+ to NADPH
NADPH will now be used in light-independent reactions
Chemiosmosis
name given to relationship between hydrogen ion movement and production of ATP
Part 1: Light-Dependent
Part 2: Light-Independent
NADPH and ATP in the stroma are used synthesize glucose in the Calvin-Benson Cycle
1. Carbon Dioxide Fixation
the carbon of CO2 joins RuBP, a five-carbon molecule, producing an unstable six-carbon molecule
the six-carbon molecule breaks down into two three-carbon molecules
2. Reduction
low-energy three-carbon compounds are converted to high-energy compounds by ATP and NADPH, resulting in PGAL
PGAL may leave the cycle to make glucose, or it can continue on to the next step of the cycle
3. Replacing RuBP
PGAL molecules are broken and reformed to make RuBP with the help of ATP
Synthesizing Glucose
Calvin-Benson Cycle must occur 6 times, which produces 12 PGAL molecules
2 PGAL leave the chloroplast to make glucose
10 PGAL are used to regenerate RuBP
1.
Photosystem II
absorbs light and pass the energy to the
reaction center
on chlorophyll
a

2. electron in reaction center is now "excited," so it is passed to an electron-accepting molecule
reaction center becomes oxidized and must replace the lost electron before it can absorb more light
replaced by an electron of a split water molecule (H2O -> 2H+ + 1/2O2)
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