Transcript Ch 8 Cellular Energy

Chapter 8 Cellular Energy
8.1 How Organisms Obtain Energy
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Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
Transformation of Energy
 Energy is the ability to do work.
 Thermodynamics is the study of the flow
and transformation of energy in the
universe.
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Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
Laws of Thermodynamics
 First law—energy can be converted from
one form to another, but it cannot be created
nor destroyed.
 Second law—energy cannot be converted
without the loss of usable energy.
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Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
Autotrophs and Heterotrophs
 Autotrophs are organisms that make their
own food.
 Heterotrophs are organisms that need to
ingest food to obtain energy.
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Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
Metabolism
 All of the chemical reactions in a cell
 Photosynthesis—light energy from the Sun
is converted to chemical energy for use by
the cell
 Cellular respiration—organic molecules are
broken down to release energy for use by
the cell
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Cells need energy for:
 Making new molecules
 Maintaining homeostasis
 Active transport
 Endocytosis
 Exocytosis
 Going against the concentration gradient
 Movement
 Cilia and flagella
 Muscle contraction including cardiac muscle
 Cell division
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ATP stores energy in chemical
bonds
 A= adenosine
 T= tri
 P= phosphate
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ATP and ADP recycle
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ATP is like currency
 Cells can only use the ATP for energy even
though they store energy as fats,
carbohydrates or proteins
 Carbohydrates, fats and proteins must be
changed to ATP before they can be used by
the cell (process of cellular respiration)
 You can only use coins in the soda machine
even though you may have a $5 bill in your
pocket
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How cells tap into the energy
stored in ATP
 Many enzymes have a site where ATP
fits in like a battery to provide the
energy for that enzyme to work
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Chapter 8 Cellular Energy
8.2 Photosynthesis
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Photosynthesis: The Big Picture
 Plants change solar
energy (sunlight)
into ATP then into
glucose (chemical
energy)
 Two step process
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Overall reaction of photosynthesis
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Role of Chloroplasts
 Chlorophyll is the pigment found in
the chloroplasts of plants and algae
 Chloroplast is the location for
photosynthesis
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Chloroplast Structure
 Thylakoid
membrane is the
site for
photosynthesis
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Chlorophyll
 Plants have two types of chlorophyll
 Chlorophyll a is yellow green
 Chlorophyll b is blue green
 We see plants as green because green is
reflected not absorbed by the chlorophyll
 Plants also contain red, orange and yellow
pigments
 When leaves “turn colors” in the fall it is
because chlorophyll productions ceases and
the other colors are exposed
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Photosynthesis: A Two Step
Process
 Step One: Light Dependent Reactions
 Step Two: Light Independent
Reactions (previously called the Dark
Reactions or the Calvin Cycle)
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Light Dependent Reactions of
Photosynthesis
 Light strikes a chlorophyll molecule
and excites an electron
 Electron gets passed to a series of
proteins in an electron transport
chain and an ATP gets made
 Electron goes to a second electron
transport chain and another energy
molecule (NADPH) gets made
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Light Dependent Reactions of
Photosynthesis
 Photolysis must happen to “fill in the
hole” left by the electron that was
excited
 Photolysis is the splitting of water;
the hydrogen goes to fill the
electron’s place and the oxygen is
what we breathe (O2)
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Light Dependent Reactions of
Photosynthesis
 Start with sunlight and get ATP and
NADPH
 Energy molecules used for Step Two
 Start with water and get oxygen
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Light Independent Reactions of
Photosynthesis
Light
dependent
Light
dependent
Light independent
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Light Independent Reactions of
Photosynthesis
 ATP and NADPH from the light
dependent reaction provide the
energy to convert CO2 to C6H12O6
(glucose)
 Uses many enzymes in a cycle to
produce glucose
 Cycles are important in organisms
because they allow for constant
production
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Light Independent Reactions of
Photosynthesis
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Light Independent Reactions of
Photosynthesis
 Each “turn” of the cycle produces ½
of a glucose
 ATP and NADPH are used to produce
this glucose
 No sunlight is needed, reactions
happen independent of light
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Alternative Pathways
 C4 Plants: fix CO2
into four-carbon
compounds
keep stomata
closed during hot
days (less
transpiration water
loss)
Sugar cane and
corn
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Alternative Pathways
 CAM plants: conserve
water by allowing CO2
to enter only at night
(stomata closed during
day to conserve water)
 Examples: pineapple,
cacti, orchids and
other desert or salt
march plants
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Chapter 8 Cellular Energy
8.3 Cellular Respiration
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Cellular Respiration
 Process of breaking down food to
produce ATP
 ALL living things do cellular
respiration, even:
 Plants
 Bacteria
 Eukaryotes in the mitochondria
 Prokaryotes in the cytoplasm
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Cellular Respiration
Overall reaction
C6H12O6 + O2
CO2 + H2O + energy
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Cellular Respiration
 Three Stage Process
1. Glycolysis: anaerobic
2. Citric Acid Cycle: aerobic
3. Electron Transport Chain: aerobic
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Cellular Respiration Overview
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Glycolysis
 Happens in the
cytoplasm
 Need to use two
ATP before can get
ATP out of the
process
 One glucose is
split and converted
into two pyruvate
yields four ATP
(two net ATP)
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Citric Acid Cycle or Krebs Cycle
 Happens in the
mitochondrial
matrix
 CO2 produced
 Per turn of the
cycle yields:
 1 ATP
 3 NAPH
 1FADH2
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Electron Transport Chain
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Electron Transport Chain
 Located within the inner
mitochondrial membrane
 Converts NADH and FADH2 into ATP
 Energized electrons are passed along
a series of proteins
 Some energy is converted directly into
ATP
 Other energy causes H+ ions to be forced
out of the inner mitochondrial matrix
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Electron Transport Chain cont.
 The force of H+ ions back into the
mitochondrial matrix through the
enzyme ATP synthase provides the
energy for ATP synthesis
 Oxygen is the final electron acceptor
 Without oxygen the transport chain
would shut down like a traffic jam
 Traffic (electrons) would back up and
shut down the Krebs Cycle as well
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Electron Transport Chain cont.
 For every NADH get 3 ATP
 For every FADH2 get 2 ATP
 Overall get a net of 32 ATP from one
molecule of glucose
 Balanced equation:
C6H12O6 + 6O2
6CO2 + 6H2O + 32 ATP
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Fermentation
 Occurs when O2 is not present, no
aerobic respiration, no Krebs Cycle,
no Electron Transport Chain
 Allows the continuation of glycolysis
by the removal of pyruvate
 Some organisms in anaerobic
environments produce energy by
fermentation all the time
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Fermentation: Two Types
 Alcoholic
 Yeast
 Produce CO2, ethyl
alcohol and 2 ATP
from pyruvate
 Important in bread
and alcoholic
beverage industries
 Lactic Acid
 Animal muscle cells,
some bacteria and
some plants
 Produce lactic acid
and 2 ATP from
pyruvate
 Get sore, burning
muscles
 Liver converts lactic
acid back to pyruvate
when O2 is present
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Comparing Photosynthesis and
Cellular Respiration




Both
Both
Both
Both
ions
use
use
use
use
electron transport chains
cycles of chemical reactions
electron carrier proteins
concentration gradient of H+
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Comparing Photosynthesis and
Cellular Respiration
 Photosynthesis
 Food accumulated
 Solar energy stored
in glucose
 CO2 taken in, O2
given off
 Occurs only in
presence of
chlorophyll with
sunlight
 Cellular Respiration
 Food broken down
 Glucose energy
released
 O2 taken in, CO2
given off
 Occurs in all living
things all the time
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