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TRANSCRIPT
Outline
I. Energy and Carbon Cycle
II. Photosynthesis
A. Introduction
B. Reactions
II. Cellular Respiration
A. Introduction
B. Reactions
Carbon Cycle
All organisms require energy to maintain life
The primary form of cellular energy is in ATP
adenosine triphosphate
adenosine diphosphate -- carrier
Carbon Cycle
ATP is generated in a process called cellular
respiration
Cellular respiration uses glucose molecules (a
carbohydrate commonly called sugar)
C6H12O6
Carbon Cycle
Glucose is an organic compound, which means it
contains carbon-hydrogen bonds
Glucose must be made by organisms
Organisms that make glucose are called
autotrophs (auto = self; troph = feed)
Autotroph means self-feeding, or an organism
that can make its own food
Autotrophs are called producers because they
produce their own food
Carbon Cycle
Producers create glucose in a process called
photosynthesis
Producers include plants, algae, and some
bacteria and protists
Once glucose is created, it can be used to make
the ATP that supplies energy
Carbon Cycle
Plants get the carbon they need to make glucose
(C6H12O6) from carbon dioxide (CO2)
This carbon is cycled through photosynthesis
and cellular respiration through a perpetual
process that reuses the carbon to create new
energy
Thus, it is called the Carbon Cycle – and is also
known as the Energy Cycle
Human Influence
Human civilization has a very
significant influence on the
carbon cycle.
Burning of fossil fuels (oil,
coal, natural gas) releases
CO2 into the atmosphere.
CO2 is a greenhouse gas and
traps heat in the atmosphere.
This has a warming effect on
the earth.
Human Influence
Human activity began releasing CO2 into the atmosphere
in unprecedented amounts starting with the Industrial
Revolution
In the last 150 years, the amount of CO2 in the
atmosphere has increased by more than 30%.
This is a major contributing factor to global warming.
2014, 2015, 2016, 2017, and 2018 rank as the 5 warmest
years (globally) on record.
125,000 years ago was the last time the Earth was this
warm. Sea levels were 18-27 feet higher at that time.
The last time CO2 levels were this high was 3-5 million years ago
during the warmest part of the Pliocene.
Global temperatures were 3-4 C (5-7 F) higher and temperatures at
the poles were 10 C (18 F) higher.
Ice caps were small and sea levels were as much as 90 feet higher
than today.
There was a cooling trend toward the end of this epoch, but
scientists are unclear what caused it.
Human Influence
Impacts of human caused global warming:
– Temperatures rise glaciers melt oceans warm more
glaciers melt temperatures rise further
– Sea levels rise
New Orleans, Miami, Boston, L.A., and New York City are among
the U.S. cities predicted to be underwater in the coming decades
– Ocean currents disrupted
Superstorms, hurricanes’ and
blizzards become more common
and more severe
– Desertification
Forests and grasslands
become arid deserts
Photosynthesis
Method of converting sun energy into chemical energy usable by cells
Autotrophs: self feeders, organisms capable of making their own food– Photoautotrophs: use sun energy e.g. plants
photosynthesis-makes organic compounds (glucose) from light
– Chemoautotrophs: use chemical energy e.g. bacteria that use sulfide or methane chemosynthesis-makes organic compounds from chemical energy contained in sulfide or methane
Photosynthesis
Photosynthesis takes place in specialized
structures inside plant cells called chloroplasts
– Light absorbing pigment molecules e.g. chlorophyll
Why Plants are Green
Light is composed of photons
Photon energy is measured in wavelengths
Different wavelengths generate different colors of
light
What is Seen
All wavelengths (colors) together appear as white light
The white light can be separated into the visible spectrum
– the rainbow…. ROYGBIV
Other wavelengths are not visible to humans – Infrared
(IR) and Ultraviolet (UV)
Why Plants are Green
What is seen is what is reflected back
All other detectable colors are absorbed
Chloroplasts contain pigments
The dominant pigment is chlorophyll, which absorbs red
and blue while reflecting green and yellow
The absorbed
wavelengths provide
the energy needed to
power photosynthesis
Photosynthesis
Most easily understood in two parts:
1. Light dependent reactions
– make the energy needed to connect carbons
2. Light independent reactions
– use the energy to connect the carbons
Overall Reaction
6CO2 + 12 H2O + light energy → C6H12O6 + 6O2+ 6H2O
Water appears on both sides because 12 H2O molecules
are required and 6 new H2O molecules are made
Important carrier molecules are used
– ADP ATP
– NADP NADPH
Light Dependent Reactions
Three important components
1. Harnesses sunlight
2. Splits water
3. Creates energy molecules
Composed of two separate processes
1. Photosystems – creates NADPH
2. Chemiosmosis – creates ATP
Both of these occur in the thylakoid membrane
Both use peripheral and integral proteins
Splitting Water
Water is split into H+, e-, and O2
– H+ and e- are used elsewhere
– O2 is a waste product
Photosystems
• Light energy is absorbed by
chlorophyll molecules
• Energy boosts e- to high energy
states
• As the e- fall back down to low
energy states, NADPH is created
*The H+ and e- come
from the split water
Chemiosmosis
Photosystems also create H+
concentration gradient
H+ diffuses back through ATP
synthase to create ATP
Calvin Cycle (light independent or “dark” reactions)
ATP and NADPH generated in light reactions
used to fuel the reactions which take CO2 and
break it apart, then reassemble the carbons into
glucose.
Called carbon fixation: taking carbon from an
inorganic molecule (atmospheric CO2) and
making an organic molecule out of it (glucose)
Simplified version of how carbon and energy
enter the food chain
Calvin Cycle
Takes place in stroma
Single C m-cules cycled through to
create C3 m-cules
C3 m-cules made into glucose later
Harvesting Chemical Energy
Energy enters the food web via autotrophs when they convert light energy into chemical energy.
All organisms use this chemical energy (glucose) to create energy molecules (ATP) that fuel their metabolism.
Heterotrophs – unlike autotrophs they don’t create the fuel they use; they must consume it.
Cellular Respiration Overview
Transformation of chemical energy in food
(glucose and other macromolecules) into
chemical energy cells can use: ATP
These reactions proceed the same way in plants
and animals – CELLULAR RESPIRATION
Overall Reaction:
C6H12O6 + 6O2 → 6CO2 + 6H2O
Hint – Reverse Photosynthesis
Cellular Respiration is like photosynthesis in reverse…
sort of.
The products become reactants and the reactants the
products…
Just switch light energy for ATP
And don’t get any dumb tattoos… it’s
not that hard to remember.
Cellular Respiration Overview
Breakdown of glucose begins in the cytoplasm --
the liquid matrix inside the cell
There are two pathways:
– Anaerobic cellular respiration (aka fermentation)
– Aerobic cellular respiration
OR
C.R. Reactions
Glycolysis
– Series of reactions which break the 6-carbon glucose
molecule down into two 3-carbon molecules called
pyruvate
– Process is an ancient one-all organisms from simple
bacteria to humans perform it the same way
– Yields 2 ATP molecules for every one glucose
molecule broken down (net)
– Yields 2 NADH per glucose molecule
Anaerobic Cellular Respiration
Some organisms thrive in environments with little or no oxygen
– Marshes, bogs, gut of animals, sewage treatment ponds
Results in no more ATP: final steps in these pathways serve
ONLY to regenerate NAD+ so it can be recycled to be used in
gycolosis again.
an = without
aerobic = oxygen
anaerobic = without oxygen
Ferment yeast, make ethanol, get beer.
Work your muscles, make lactic acid, get sore.
Aerobic Cellular Respiration
Oxygen present
3 more steps, which occur in the mitochondria
1. Link Reaction
2. Kreb’s Cycle
3. Oxidative Phosphorylation
Link Reaction
Preps the 3C pyruvate for the Kreb’s cycle and
brings it into the mitochondria
Happens in matrix
Coenzyme A used, CO2 given off
NADH produced
Kreb’s Cycle Overview
Completes the breakdown of glucose
– Takes the Acetyl CoA (2-carbons) and breaks it down,
the carbon and oxygen atoms end up in CO2
– Hydrogens and electrons are stripped and loaded onto
NAD+ and FAD to produce NADH and FADH2
Occurs in the mitochondrial matrix
Production of only 1 more ATP (per Acetyl CoA)
– but loads up the carriers NAD+ and FAD to produce
large quantities of ATP in the final stage.
Kreb’s Cycle
Acetyl CoA
(2C)
3 NADH
3 NAD
1 ATP
1 ADP
1 FADH2
1 FADCO2
Kreb’s
Cycle
YIELD*: 1 ATP
3 NADH
2 FADH2
*REMEMBER: 2x
Oxidative Phosphorylation
The temporary carriers (NADH and FADH2) enter
the ETC (electron transport chain) in the cristae.
Their high energy e- are used to pump protons
(H+) across the cristae membrane to create a
concentration gradient.
The H+ then diffuse back through ATP synthase
to create ATP. (chemiosmosis again!)
In the process, the extra electrons and protons
are joined to oxygen to create water.
Energy Yield
Anaerobic
– Yields only 2 ATP (net)
– organisms that use this
can’t be too energetic
– important microorganisms
for carbon recycling
– fermentation
– lactic acid
Energy Yield --Aerobic Respiration
Gycolosis
Acetyl CoA
Kreb’s Cycle
ETC2 ATP
18 ATP
6 ATP
6 ATP
2 ATP
4 ATP
2 NADH
1 NADH x2
3 NADH x2
1 FADH2 x2
1 ATP x2
4 ATP -2
x3
x3
x3
x2
1 C6H12O6