Transcript video slide - yayscienceclass

CHAPTER 6
Cellular Respiration:
Obtaining Energy from
Food
Interesting facts! Which intrigue you?
How does cellular respiration relate to you?
• When you exercise,
– Muscles need energy in order to perform
work.
– Your cells use oxygen to release energy
from the sugar glucose (C6H12O6).
Metabolism
• Aerobic metabolism
– Occurs when enough oxygen reaches cells
to support energy needs.
• Anaerobic metabolism
– Occurs when the demand for oxygen
outstrips the body’s ability to deliver it.
Metabolism
• Anaerobic metabolism
– Without enough oxygen, muscle cells break
down glucose to produce lactic acid.
– Lactic acid is associated with the “burn”
associated with heavy exercise.
– If too much lactic acid builds up, your
muscles give out.
How does cellular respiration relate to you?
• Physical conditioning allows your body to
adapt to increased activity.
– The body can increase its
ability to deliver oxygen
to muscles.
• Long-distance runners wait
until the final sprint to
exceed their aerobic
capacity.
Energy Flow and Chemical Cycling in the Biosphere
• Fuel molecules in food represent solar
energy.
– Energy stored in food can be traced back
to the sun.
• Animals depend on plants to convert solar
energy to chemical energy.
– This chemical energy is in the form of
sugars and other organic molecules.
Producers and Consumers
• Photosynthesis
– Uses light energy from the sun to power a
chemical process that makes organic
molecules.
– Occurs in the leaves of terrestrial plants.
Producers and Consumers
• Autotrophs
– Are “self-feeders”.
– Include plants and other organisms that
make all their own organic matter from
inorganic nutrients.
• Heterotrophs
– Are “other-feeders.”
– Include humans and other animals that
cannot make organic molecules from
inorganic ones.
Producers and Consumers
• Producers
– Biologists refer to
plants and other
autotrophs as the
producers in an
ecosystem.
• Consumers
– Heterotrophs are
consumers, because
they eat plants or
other animals.
What is Cellular Respiration?
•The release of chemical energy for use by cells in
the form of ATP.
•It occurs in ALL living things.
•Once the energy that was in sunlight is changed
into chemical energy by photosynthesis, an
organism has to transform the chemical energy
into a form that can be used by the organism.
•This process is cellular respiration.
Chemical Cycling between
Photosynthesis and Cellular Respiration
• The ingredients for photosynthesis are
carbon dioxide and water.
– CO2 is obtained from the air by a plant’s
leaves.
– H2O is obtained from the damp soil by a
plant’s roots.
• Chloroplasts rearrange the atoms ofof
these
ingredients to produce sugars (glucose)photosyn
and
other organic molecules.
thesis
– Oxygen gas is a by-product of photosynthesis.
.
Both plants and animals
perform cellular
respiration!!
– Cellular respiration is
a chemical process
that harvests energy
from organic molecules.
– Cellular respiration
occurs in mitochondria.
• The waste products of
cellular respiration,
CO2 and H2O, are used in
photosynthesis.
of
.
photosyn
thesis
Cellular Respiration:
The Aerobic Harvest of Food Energy
• Cellular respiration
– Is the main way that chemical energy is
harvested from food and converted to
ATP.
– Is an aerobic process—it requires oxygen.
The Relationship between Cellular
Respiration and Breathing
• Cellular respiration and breathing are
closely related but they are NOT the same!
– Cellular
respiration
requires a cell
to exchange
gases with its
surroundings.
– Breathing
exchanges these
gases between
the blood and
outside air.
The Overall Equation for Cellular Respiration
• A common fuel molecule for cellular
respiration is glucose.
– The overall equation for what happens to
glucose during cellular respiration
MEMORIZE!!
The Role of Oxygen in Cellular Respiration
• During cellular respiration, hydrogen and its
bonding electrons change partners.
– Hydrogen and its electrons go from sugar
to oxygen, forming water.
• Chemical reactions that transfer electrons
from one substance to another are called
oxidation-reduction reactions, or redox
reactions for short.
Redox Reactions
• The loss of electrons during a redox
reaction is called oxidation.
• The acceptance of electrons during a
redox reaction is called reduction.
The Release of Energy
• Why does electron
transfer to oxygen
release energy?
– When electrons move
from glucose to oxygen, it is as though
they were falling.
– This “fall” of electrons
releases energy during
cellular respiration.
NADH and Electron Transport Chains
• The path that electrons take on their way
down from glucose to oxygen involves many
steps.
NADH and Electron Transport Chains
• The first step is an electron acceptor called
NAD+.
– The transfer of electrons from organic
fuel to NAD+ reduces it to NADH.
• The rest of the path consists of an electron
transport chain.
– This chain involves a series of redox
reactions.
– These lead ultimately to the production
of large amounts of ATP (34-36!).
The Metabolic Pathway of Cellular Respiration
• Cellular respiration is an example of a
metabolic pathway,
– A series of chemical reactions in cells.
• All of the reactions involved in cellular
respiration can be grouped into three main
stages:
1. Glycolysis
2. The citric acid cycle (The Krebs Cycle)
3. Electron transport
A Road Map for Cellular Respiration
• The path of glucose through cellular
respiration
Stage 1: Glycolysis
• A molecule of glucose is split into two
molecules of pyruvic acid. In other words
glycolysis breaks a six-carbon glucose into
two three-carbon molecules.
• These molecules then donate high energy
electrons to NAD+, forming NADH.
Stage 1: Glycolysis
• Glycolysis makes some ATP directly when
enzymes transfer phosphate groups from
fuel molecules to ADP.
• Note that 2
ATP used to
start Glycolysis
so while
Glycolysis
produces 4 ATP
only 2 are really
gained.
Stage 2: The Citric Acid Cycle (Krebs Cycle)
• The citric acid cycle completes the
breakdown of sugar.
• In the citric acid cycle, pyruvic acid from
glycolysis is first “prepped” into a usable
form, Acetyl CoA.
of
.
photosyn
thesis
Stage 2: The Citric Acid Cycle (Krebs Cycle)
• The citric acid cycle extracts the energy of
sugar by breaking the acetic acid molecules
all the way down to CO2.
– The cycle uses some of this energy to
make ATP. 2 ATP are produced.
– The cycle also forms NADH and FADH2.
Stage 2: The Citric Acid Cycle (Krebs Cycle)
of
.
photosyn
thesis
Stage 3: Electron Transport
• Electron transport releases the energy your
cells need to make most of their ATP.
• The molecules of electron transport chains
are built into the inner membranes of
mitochondria, called cristae.
– The chain functions as a chemical machine
that uses energy released by the “fall” of
electrons to pump hydrogen ions across
the inner mitochondrial membrane.
– These ions store potential energy.
Stage 3: Electron Transport
• When the hydrogen ions flow back through
the membrane, they release energy.
– The ions flow through ATP synthase
(an enzyme).
– ATP synthase takes the energy from this
flow, and synthesizes ATP. (32-34!)
of
.
photosyn
thesis
The Versatility of Cellular Respiration
• Cellular respiration can “burn” other kinds
of molecules besides glucose:
1. Diverse types of carbohydrates
2. Fats
3. Proteins
Cellular Respiration Overview
Adding Up the ATP from Cellular Respiration
• A summary of ATP yield during cellular
respiration
of
.
photosyn
thesis
Respiration
PROTEINS
CYTOPLASM
GLYCOLOSIS
HAPPENS HERE!
CARBO’S
(SUGARS)
FATS
(LIPIDS)
AMINO
ACIDS
GLUCOSE
C6H12O6
GLYCOLOSIS
IN CYTOPLASM
NO OXYGEN!
ATP TOTALS
GLYCOLOSIS=2
PYRUVIC
ACID
RESPIRATION=36
BOTH=38!
MAKES
2 ATPS
ACETYL-CoA
CO2 IS
RELEASED
of
O2 ENTERS
HERE
MITOCHONDRIA
RESPIRATION HAPPENS IN
THIS ORGANELLE!
KREBS CYCLE
AND
ELECTRON
TANSPORT
MAKES
34 ATPS
.
photosyn
thesis
Fermentation:
Anaerobic Harvest of Food Energy
• Some of your cells can actually work for
short periods without oxygen.
• A process that does not use oxygen is called
anaerobic.
• Fermentation
– Is the anaerobic harvest of food energy.
Fermentation in Human Muscle Cells
• After functioning anaerobically for about 15
seconds,
– Muscle cells will begin to generate ATP by
the process of fermentation.
• Fermentation relies on glycolysis to produce
ATP.
Fermentation in Human Muscle Cells
• Glycolysis is the metabolic pathway that
provides ATP during fermentation.
– Pyruvic acid is reduced by NADH,
producing NAD+, which keeps glycolysis
going.
– In human muscle cells, lactic acid is a
by-product.
– This is known as lactic acid fermentation.
Fermentation Overview
Fermentation in Microorganisms
• Various types of microorganisms perform
fermentation.
– Yeast cells carry out a slightly different
type of fermentation pathway.
– This pathway produces CO2 and ethyl
alcohol.
– This is known as alcoholic fermentation.
A Comparison of Fermentation Types
A Comparison of Fermentation to Respiration
2 ATP
2 ATP
36-38 ATP
Fermentation in Industry
• The food industry uses yeast to produce
various food products.
• We will be making root beer!
mmmmmmMMMmmmm!
Evolution Connection:
Life on an Anaerobic Earth
• Ancient bacteria probably used glycolysis to
make ATP long before oxygen was present
in Earth’s atmosphere.
– Glycolysis is a metabolic heirloom from the
earliest cells that continues to function
today in the harvest of food energy.
CHAPTER 7
Photosynthesis: Using
Light to Make Food
Interesting facts! Which intrigue you?
Overview of Photosynthesis and Respiration
SUN
RADIANT
ENERGY
PHOTOSYNTHESIS
GLUCOSE
RESPIRATION
CELL
ACTIVITIES
ATP (ENERGY)
What is Photosynthesis?
The process of photosynthesis is a
chemical reaction.
It is the most important chemical
reaction on our planet.
Tell me… WHY?
Biology and Society: Plant Power for Power Plants
• On a global scale the productivity of
photosynthesis is astounding.
• All of the food consumed by humans can be
traced back to photosynthetic organisms.
• An “energy
plantation”
– Is a renewable
energy source.
The Basics of Photosynthesis
• Almost all plants are photosynthetic
autotrophs, as are some bacteria and
protists.
– They generate their own organic matter
through photosynthesis.
Cyanobacteria (Oscillatoria)
Chloroplasts: Sites of Photosynthesis
• Photosynthesis
– Occurs in chloroplasts.
• Chloroplasts
– Are found in the interior cells of leaves.
– Contain stroma, a thick fluid.
– Contain thylakoids, membranous sacs.
Chloroplasts: Sites of Photosynthesis
Figure 7.3
The Overall Equation for Photosynthesis
• The reactants and products of the reaction
MEMORIZE!!
Photosynthesis and Electrons
• In photosynthesis,
– Energized electrons are added to carbon
dioxide to make sugar.
– Sunlight provides the energy.
• Note that not all electrons contain the same
amount of energy. Some are low energy and
some are high energy (energized).
– The ability of electrons to gain or lose
energy is needed for all living things to
survive!
Photosynthesis and Electrons
• The electron gains energy by absorbing
photons.
• Once it gains enough it will leaves the
chlorophyll molecule. The electron is now
described as a “high-energy electron” and
can provide energy for the formation of
molecules of ATP.
– Remember: If an electron gains energy it moves to
an outer shell; if the electron gains enough energy,
the electron may be driven out of the atom.
– If an electron loses energy it moves to an inner
shell (i.e., closer to the nucleus of the atom).
A Photosynthesis Road Map
• Photosynthesis is composed of two processes:
1. The light reactions
convert solar
energy to chemical
energy.
2. The dark reactions,
also known as the
light independent
reactions or The
Calvin Cycle, make
sugar from carbon
dioxide.
The Light Reactions:
• Converting Solar Energy to Chemical Energy
• Chloroplasts are chemical factories powered
by the sun
– That convert solar energy into chemical
energy.
– Produces two high energy molecules
1. NADP-H
2. ATP
The Nature of Sunlight
• Sunlight is a type of energy called radiation
– Or electromagnetic energy.
– Packets of light energy are called photons.
• The full range of radiation is called the
electro-magnetic spectrum.
• Shorter wavelengths have more energy than
longer wavelengths.
• When you see color, you are seeing the
reflection of that wavelength.
The Nature of Sunlight
Figure 7.5
Sunlight and Photosynthesis
• Chloroplasts absorb select wavelengths of
light that drive photosynthesis.
Light and Pigments
Chloroplast Pigments
• Chloroplasts contain several pigments:
– Chlorophyll a
– Chlorophyll b
– Carotenoids
Summary of How Photosystems
Harvest Light Energy
• Light behaves as photons, discrete packets
of energy.
• Chlorophyll molecules absorb photons.
– Electrons in the pigment gain energy.
– The energy is released and used.
How Photosystems Harvest Light Energy Details!
• A photosystem: Is an organized group of
chlorophyll and other molecules that are used
as a light-gathering antenna. When chlorphyll
absorbs light electrons gain energy.
• The two photosystems:
1. Photosystem I - High energy electrons
contained here are used to manufacture
molecules of NADP-H.
2. Photosystem II - High energy electrons
here are used to manufacture molecules
of ATP.
How Photosystems Harvest Light Energy
Figure 7.10
How the Light Reactions Generate ATP and NADPH
• The light reactions of photosynthesis
Photosystems I & II
• Two types of photosystems cooperate in the
light reactions.
Photosystems I & II
• An electron transport chain
– Connects the two photosystems.
– Releases energy that the chloroplast uses
to make ATP.
Photosystems I & II
• The light reactions in the thylakoid
membrane
Light Reactions
The Calvin Cycle (dark reactions)
• Making Sugar from Carbon Dioxide
• The Calvin cycle
– Functions like
a sugar
factory within
the stroma of
a chloroplast.
– Regenerates
the starting
material with
each turn.
The Calvin Cycle (dark reactions)
• The Calvin cycle requires the input of
carbon dioxide (as a source of carbon for
building carbohydrates)
• The availability of ATP and NADP-H to
provide energy to reduce the carbon
dioxides and construct high-energy
carbohydrates such as sugar.
The Calvin Cycle (dark reactions)
• A 3-carbon product of the Calvin cycle is
phosphoglyceraldehyde (which is also called
glyceraldehyde phosphate) and is commonly
symbolized as PGAL or G3P in your text.
Two of these will form glucose, the others
will be recycled to use again in this cycle.
• Note: For each carbon atom that is
released from the Calvin cycle in a highenergy carbohydrate molecule, one low
energy carbon dioxide molecule must enter
the cycle.
Calvin Cycle
Water-Saving Adaptations
• Three types of photosynthesis:
–
C3, C4 and CAM photosynthesis
• C3 plants
– Use CO2 directly from the air.
– Are very common and widely distributed.
Water-Saving Adaptations
C4 plants
– Close their stomata to save water during
hot and dry weather.
– Can still carry out photosynthesis.
CAM plants
– Open their stomata only at night to
conserve water.
The Environmental Impact of Photosynthesis
• A review of photosynthesis
• Photosynthesis has an enormous impact on
the atmosphere.
– It swaps O2 for CO2.
How Photosynthesis Moderates Climate Change
• Greenhouses used to grow plant indoors
– Trap sunlight that warms the air inside.
How Photosynthesis Moderates Climate Change
• A similar process, the greenhouse effect,
– Warms the atmosphere.
– Is caused by greenhouse gases such as
atmospheric CO2, methane and others.
How Photosynthesis Moderates Climate Change
• Greenhouse gases are the most likely cause
of global warming, a slow but steady rise in
the Earth’s surface temperature.
– Destruction of forests may be increasing
this effect.
Evolution Connection:The Oxygen Revolution
• The atmospheric oxygen we breathe is a
by-product of photosynthesis.
• Cyanobacteria were the first organisms to
carry out photosynthesis.
• The production of oxygen changed the
Earth forever.
– The “oxygen revolution” was a major
episode in the history of life on Earth.
Compare and Contrast
Photosynthesis
&
Cellular Respiration
Photosynthesis & Cellular
Respiration are Interconnected
The End