Unit 4 Cellular Respiration and Photosynthesis

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Unit 4 Cellular Respiration and Photosynthesis
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I. Sunlight powers Life A. Obtaining Food 1.
Autotroph- self-feeder an organism that
makes its own food a) Make food during
photosynthesis b) Producers- organisms
that produce the organic molecules that
serve as food for the organisms in their
ecosystem
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2. Heterotroph- other eaters organisms that
cannot make their own food a) Consumers-
organisms that must obtain food by eating
producers or other consumers
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B. Harvesting Energy in Food 1. Cellular
Respiration a chemical process that uses
oxygen to convert the chemical energy stored in
organic molecules into another form of chemical
energy (ATP) a) Cells in plants and animals
then use ATP as their main energy supply.
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2. Photosynthesis and Cellular respiration
recycle a common set of chemicals water, carbon
dioxide, oxygen, and organic compounds
(glucose). a) Water and carbon dioxide are
raw ingredients for photosynthesis plants
use energy from sunlight to rearrange the
atoms of water and carbon dioxide to produce
glucose and oxygen.
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b) Oxygen is used by both plant and animal cells
during cellular respiration to release the energy
stored in glucose the released energy enables
cells to produce ATP Cellular respiration also
produces carbon dioxide and water.
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Figure 7-3The products of photosynthesis are the
chemical ingredients for cellular respiration,
while the products of cellular respiration are
the chemical ingredients for photosynthesis.
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II. Food stores chemical energy A. Introduction
to Energy 1. Energy is the ability to perform
work. 2. Basic forms of Energy a) Kinetic
energy of motion 1) Thermal energy- total
amount of energy associated with the
random movement of atoms and molecules
in a sample of matter
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b) Potential energy- energy stored due to an
objects position or arrangement
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B. Chemical Energy 1. The potential to perform
work due to the arrangement of atoms within
molecules
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Figure 7-5The stored chemical energy of foods
such as peanuts can be released through cellular
respiration.
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C. Putting Chemical Energy to Work
Figure 7-7Both engines and cells use oxygen to
convert the potential energy in complex molecules
to energy that can be used for work.
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D. Calories Units of Energy 1. The amount of
energy required to raise the temperature of 1
gram of water by 1 degree Celsius 2. Energy in
food is expressed as kilocalories. a) 1
kilocalorie (kcal) 1,000 calories
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Figure 7-8Different daily activities require
different amounts of energy. Organic molecules in
food are the source of this energy.
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III. ATP provides energy for Cellular Work A.
How ATP packs energy 1. ATP stands for
adenosine triphosphate 2. Releasing energy
from ATP occurs when a phosphate is pulled
away during a chemical reaction. a) The
resulting molecule is ADP (adenosine
diphosphate).
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Figure 7-9An ATP molecule contains potential
energy, much like a compressed spring. When a
phosphate group is pulled away during a chemical
reaction, energy is released.
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B. ATP and Cellular Work 1. 3 types of work done
by cells a) Chemical work 1) Example
building a large molecule such as
proteins b) Mechanical work 1) Example the
contraction of a muscle c) Transport
work 1) Example pumping solutes across a
cellular membrane
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C. The ATP cycle 1. ATP is continuously
converted to ADP as your cells do work. a)
ATP is recyclable. 2. A working muscle cell
recycles all of its ATP about once every
minute. a) Thats 10 million ATPs spent and
regenerated per second.
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IV. Electrons fall from food to Oxygen during
Cellular Respiration A. Relationship of Cellular
Respiration to Breathing 1. Cellular
respiration is aerobic, meaning it requires
oxygen. 2. During Cellular Respiration, a
cell exchanges 2 gases with its
surroundings a) The cell takes in oxygen
and releases carbon dioxide.
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B. Overall Equation for Cellular Respiration 1.
C6H12O6 O2 CO2 H20 ATP (glucose)
(oxygen) (carbon dioxide) (water)
ATP 2. Produces up to 38 ATPs.
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V. Cellular Respiration converts energy in food
to energy in ATP A. Structure of
Mitochondria 1. An envelope of 2 membranes
encloses the mitochondrion. a) There is a
space between the inner and outer
membranes. b) The inner membrane
encloses a fluid called the matrix.
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B. A road map for cellular respiration 1.
Metabolism- all of a cells chemical processes
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C. Stage I Glycolysis 1. The splitting in half
of a glucose molecule a) takes place in the
cytoplasm of the cell. 2. Steps a) Using 2
ATPs as an initial investment, the cell
splits a 6- carbon glucose molecule in half.
b) The result is two 3-carbon molecules,
each with 1 phosphate group.
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c) Each 3-carbon molecule then transfers
electrons and hydrogen ions to a carrier molecule
called NAD and changes to NADH . d) The next
step is the payback on the ATP investment 4
new electrons are produced, a net gain of 2
ATPs. e) Finally, the original glucose
molecule has been converted to 2 molecules of
pyruvic acid.
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Figure 7-17 A cell invests two ATP molecules to
break down glucose. The products of glycolysis
are two pyruvic acid molecules, two NADH
molecules and four ATP molecules.
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D. Stage 2 The Krebs Cycle 1. This stage
finishes the breakdown of pyruvic acid to
carbon dioxide in the mitochondria 2.
Steps a) The starting molecule for the
Krebs cycle is the pyruvic acid produced at
the end of glycolysis. b) First, the pyruvic
acid loses a molecule of carbon dioxide.
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c) The resulting molecule is then converted into
a 2-carbon compound called acetyl coenzyme A or
Acetyl CoA. d) Third, each acetyl CoA joins a
4-carbon acceptor molecule. The reactions in
the Krebs cycle produce 2 more carbon dioxide
molecules and one ATP molecule per acetyl CoA
molecule. 1) However, NADH and FADH2 (both
are electron carriers) trap most of the
energy.
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e) Remember, glycolysis produces 2 pyruvic acids
from one glucose molecule. Each pyruvic acid is
converted to one acetyl CoA. Since each turn of
the Krebs cycle breaks down one acetyl CoA, the
cycle actually turns twice for each glucose
molecule, producing a total of 4 carbon dioxide
molecules and 2 ATP molecules.
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E. Stage 3 Electron Transport Chain and ATP
Synthase Action 1. Occurs in the inner
membranes of the mitochondria 2. Steps of the
Electrons Transport Chain a) First, the
carrier molecule NADH transfers electrons from
the original glucose molecule to an electron
transport chain.
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b) The electrons move from carrier to carrier
within the inner membrane of the mitochondria,
eventually being pulled to an oxygen at the end
of the chain to form water.
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3. Steps of ATP Synthase Action a) Each
transfer in the chain releases a small amount of
energy. This energy is used to pump hydrogen
ions across the membrane from where they are
less concentrated to where they are more
concentrated. 1) This pumping action stores
potential energy. b) The mitochondria have
protein structures called ATP synthases that
act like miniature turbines.
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c) Hydrogen ions pumped by electron transport
rush back downhill through the ATP synthase.
The ATP synthase uses the energy from the flow of
hydrogen ions to convert ADP to ATP. 1) This
process can produce up to 34 ATPs per original
glucose molecule.
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F. Adding up the ATP molecules 1. Glycolysis
produces 4 ATPs, but it requires an initial
investment of 2 ATPs, so the net gain is a
total of 2 ATPs. 2. The Krebs Cycle produces
2 more ATPs (one for each pyruvic acid) 3.
The Electron Transport Chain produces about 34
ATPs. 4. Grand total 38 ATP molecules
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VI. Some cells can harvest energy without
oxygen A. Fermentation in Human Muscle
Cells 1. A way that cells can make ATP
without using oxygen 2. Fermentation makes
ATP entirely from glycolysis a) Remember
that glycolysis produces a net gain of 2 ATP
molecules.
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b) This might not seem very efficient, but by
burning enough glucose, fermentation can
regenerate enough ATP molecules for short burst
of activity such as a sprinting.
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3. Fermentation in muscle cells produces a waste
product called lactic acid. The temporary build
up of lactic acid contributes to the fatigue you
feel during and after a long run or set of push
ups. Your body consumes oxygen as it converts
the lactic acid back to pyruvic acid. You
restore your oxygen supply by breathing heavily
for a few minutes after you stop exercising.
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B. Fermentation in Microorganisms 1. Yeast is
capable of both cellular respiration and
fermentation. 2. When yeast cells are kept in
an anaerobic environment (an environment
without oxygen), they are forced to ferment
sugar and other foods. 3. Fermentation in
yeast produces alcohol as a waste product
(called alcoholic fermentation) also releases
carbon dioxide.
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VII. Photosynthesis uses light energy to make
food A. The structure of Chloroplasts 1.
Photosynthesis takes place inside the
chloroplast. 2. Chloroplasts contain
chemical compounds called chlorophylls that
give these organelles a green color.
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a) The chloroplasts are concentrated in the
mesophyll or the inner layer. b) Tiny pores
called stomata are found on the surface of the
leaf. Carbon dioxide enters the leaf and
oxygen exits the leaf through the stomata.
Veins carry water and nutrients from the plants
roots to the leaves.
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3. Structure of the Chloroplast a) The
chloroplast has an inner and outer
membrane. 1) The inner membrane encloses a
thick fluid called stroma. Suspended in
the stroma are many disk- shaped sacs called
thylakoids. The thylakoids are arranged in
stacks called grana.
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Figure 8-2Photosynthesis takes place in cellular
organelles called chloroplasts. In this
sunflower, the greatest numbers of chloroplasts
are located in the leaves. Chlorophylls give the
chloroplastsand in turn the leavestheir green
color.
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B. Overview of Photosynthesis 1. 6CO2
6H2O C6H12O6 602 (carbon dioxide)
(water) (sugar) (oxygen) 2. The Light
Reactions a) Convert energy in sunlight to
chemical energy.
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b) First, chlorophyll captures light energy.
Then the chloroplasts use captured energy to
remove electrons from water. This splits water
into oxygen and hydrogen ions. The oxygen is a
waste product and it leaves through the stomata.
The electrons and hydrogen ions are used to make
NADPH. The chloroplasts also use light to make
ATP.
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3. The Calvin Cycle a) Makes sugar from the
atoms in carbon dioxide plus the hydrogen ions
and high-energy electrons carried by NADPH. b)
Referred to as the light- independent reactions
because it does not directly require light to
begin.
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Figure 8-4This "road map" shows the two main
stages of photosynthesis the light reactions,
which occur in the thylakoids, and the Calvin
cycle, which occurs in the stroma.
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VIII. The light reactions convert light energy to
chemical energy A. Light energy and
Pigments 1. Sunlight is a form of
electromagnetic energy. a) This kind of
energy travels in waves. b) Wavelength-
the distance between 2 adjacent waves
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b) Electromagnetic spectrum- the range of types
electromagnetic energy from gamma waves to radio
waves 1) Visible light, wavelengths that your
eyes see as different colors, consists of
wavelengths from 400 nanometers (violet) to 700
nanometers (red). 2) Shorter wavelengths have
more energy than longer wavelengths.
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Figure 8-5Different forms of electromagnetic
energy have different wavelengths. Shorter
wavelengths have more energy than longer
wavelengths.
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2. Pigments-chemical compound that determines a
substances color a) The pigments in the
chloroplasts absorb blue-violet and red-orange
light very well. They do not absorb green light
very well. Leaves look green because the green
light is not absorbed.
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Figure 8-6Of the visible light striking this
chloroplast, the green light is reflected and
transmitted more than other colors, which are
absorbed. As a result, a leaf containing
chloroplasts appears green in color.
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B. Harvesting Light Energy 1. Photosystem- a
cluster of chlorophyll and other molecules in a
thylakoid
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2. Each time a pigment molecule absorbs light,
one of the pigments electrons gains energy (the
electron becomes excited). Almost immediately,
the electron passes its energy onto its neighbor
and falls back down to ground state.
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Figure 8-8When light strikes the chloroplast,
pigment molecules absorb the energy. This energy
jumps from molecule to molecule until it arrives
at the reaction center.
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C. Chemical Products of the Light Reactions 1.
The first photosystem traps light and transfers
the excited electrons to an electron
acceptor.
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a) This photosystem can be thought of as the
water-splitting photosystem because the
electrons are replaced by splitting a molecule
of water. b) This process releases oxygen as a
waste product and also releases hydrogen ions.
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2. The electron transport chain connecting the
two photosystems releases energy, which the
chloroplast uses to make ATP. a) Hydrogen ions
are pumped across a membrane and travel through
ATP synthase. The backflow of hydrogen ions
out of the thylakoid causes ADP to be converted
to ATP.
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3. The second photosystem can be thought of as
the NADPH-producing photosystem. a) NADPH
is produced by transferring excited
electrons and hydrogen ions to NADP.
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IX. The Calvin cycle makes sugar from carbon
dioxide A. A trip around the Calvin Cycle 1.
Steps of the Calvin Cycle a) 3 carbon
dioxide molecules enter the Calvin
Cycle. An enzyme adds each carbon dioxide
to a 5 carbon molecule called RuBP,
forming three 6 carbon molecules.
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b) Next, the three 6 carbon molecules break into
six 3 carbon molecules called PGA.
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c) ATP and NADPH from the light reactions provide
energy and electrons that are used to convert the
three PGA molecules to G3P (this is a smaller
sugar molecule). Carbon exits the cycle in one
molecule of G3P. Plant cells use the G3P to make
glucose and other organic compounds.
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d) ATP provides energy used to rearrange the G3P
molecules and regenerate RuBP. ADP and NADP are
returned to the light reactions.
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B. Summary of Photosynthesis 1. Light reactions
(takes place in the thylakoid membrane)
converts light energy to ATP and NADPH. 2.
Calvin Cycle (takes place in the stroma) uses
ATP and NADPH to convert carbon dioxide to sugar.
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X. Photosynthesis has a global impact A. The
Carbon Cycle 1. The process by which carbon
moves from inorganic to organic compounds and
back.
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B. Photosynthesis and Global Climate 1.
Greenhouse effect-process by which atmospheric
gases trap heat close to Earths surface and
prevent it from escaping into space
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Figure 8-16Some heat radiating from Earth's
surface back out toward space is trapped by
carbon dioxide (along with some other types of
gases) in the atmosphere. This greenhouse effect
keeps Earth warm enough for living things.