Transcript Cell Energy - Brookwood High School

Cell
Energy &
Photosynthesis
Cell Energy
Source of Energy
In most living organisms the energy in most food
comes from?
• the sun
• autotroph – ‘auto’ – self, ‘troph’ – food.
organisms which are able to make their own
food
– examples?
Cell Energy
Source of Energy
• heterotroph –‘heteros’– other,‘troph’– food.
obtain energy from the foods they eat.
– Impalas ?
– Leopards ?
– Mushrooms ?
• to live, all organisms must release the energy
stored in sugars and other compounds
Cell Energy
Source of Energy
In nature there are many forms that energy can
take
• examples?
– heat
– light
– nuclear
– kinetic – motion
– electrical
– and chemical
Cell Energy
Stored Energy
One of the principal chemical compounds that
living things use to store energy is?
• adenosine triphosphate (ATP)
• an ATP molecule consists of the following
– a nitrogen-containing compound - adenine
Cell Energy
adenosine tri-phosphate (ATP)
Adenine
Cell Energy
Stored Energy
One of the principal chemical compounds that
living things use to store energy is?
• adenosine triphosphate (ATP)
• an ATP molecule consists of the following
– a nitrogen-containing compound – adenine
– a 5-carbon sugar - ribose
Cell Energy
adenosine tri-phosphate (ATP)
Adenine
Ribose
Cell Energy
Stored Energy
One of the principal chemical compounds that
living things use to store energy is?
• adenosine triphosphate (ATP)
• an ATP molecule consists of the following
– a nitrogen-containing compound – adenine
– a 5-carbon sugar – ribose
– and 3 phosphate groups
Cell Energy
adenosine tri-phosphate (ATP)
Adenine
Ribose
3 Phosphate groups
Cell Energy
Stored Energy
adenosine diphosphate (ADP)
• has a structure similar to ATP but with one
important difference
– ADP has 2 phosphate groups instead of 3
• the addition of that 3rd phosphate group allows the
cell to store small amounts of energy
• similar to a battery storing energy
Cell Energy
ATP – stored energy
Adenosine Diphosphate (ADP) + phosphate
Cell Energy
ATP – stored energy
Adenosine Diphosphate (ADP) + phosphate
Partially
charged
battery
Cell Energy
ATP – stored energy
energy
Adenosine Diphosphate (ADP) + phosphate
Partially
charged
battery
Cell Energy
ATP – stored energy
energy
Adenosine Diphosphate (ADP) + phosphate
Partially
charged
battery
Adenosine triphosphate (ATP)
Cell Energy
ATP – stored energy
Adenosine Diphosphate (ADP) + phosphate
Partially
charged
battery
energy
Adenosine triphosphate (ATP)
Fully
charged
battery
Cell Energy
Releasing energy from ATP
• the energy stored in ATP is released when
ATP is converted to ADP and a phosphate
group.
– this adding and subtracting of a third
phosphate group is a way of a cell storing
and releasing energy as needed
Cell Energy
Releasing energy from ATP
the ATP molecule carries just enough energy to
power a variety of cellular activities
• active transport – sodium-potassium pump.
enough energy to transport 3 sodium ions and
2 potassium ions
• move organelles along microtubules inside
cell
Cell Energy
ATP-ADP cycle
Cell Energy
ATP and Glucose
most cells have only a small amount of ATP –
enough to last for a few seconds of activity.
– why?
• ATP is very efficient at transferring energy but
not very good at storing large amounts of
energy
• what can store lots of energy for a cell?
Cell Energy
ATP and Glucose
• glucose – stores more than 90 times the
chemical energy of a molecule of ATP
• cells can therefore use carbohydrates like
glucose to regenerate ATP from ADP
Cell Energy
Investigating Photosynthesis
Voan Helmont’s experiments (1600’s)
• he devised a way to find out if plants grew by
taking material out of the soil
– determined the mass of a pot of dry soil and
a small seedling
– planted the seedling in the pot of dry soil
– watered the plant regularly
Cell Energy
Investigating Photosynthesis
Voan Helmont’s experiments
• results
– at the end of 5 years
• the seedling had gained about 75 kg.
• the mass of the soil was almost
unchanged
- conclusions
- most of the mass gained had come from
water
Cell Energy
Investigating Photosynthesis
Voan Helmont’s experiments
• conclusions told part of the story of the growth.
what was missing?
• carbohydrate –
– ‘hydrate’ – water
– ‘carbo’ – from carbon dioxide
Cell Energy
Investigating Photosynthesis
Joseph Priestley’s experiments
• 100 years after Helmont’s experiments
• experiment set-up
– placed a candle under a glass jar
- results
- flame of candle eventually goes out
- conclusions
- something in air was necessary to keep
flame burning
Cell Energy
Investigating Photosynthesis
Joseph Priestley’s experiments
• additional experiments
- if a live sprig of mint is placed under the jar
and allowed a few days to pass, the candle
could be relighted and remain lighted for a
while
• conclusions
- the mint plant had produced the substance
required for burning - oxygen
Cell Energy
Investigating Photosynthesis
Jan Ingenhousz experiments
• Dutch scientist who later showed that the
effect observed by Priestley occurred only
when the plant was exposed to light
• conclusion
- light is necessary for plants to produce
oxygen
Cell Energy
Investigating Photosynthesis
the experiments performed by these and other
scientists reveal that
• in the presence of light
Cell Energy
Light energy
chloroplast
Cell Energy
Investigating Photosynthesis
the experiments performed by these and other
scientists reveal that
• in the presence of light
– plants transform carbon dioxide and water
Cell Energy
Light energy
chloroplast
Carbon dioxide + water
Cell Energy
Investigating Photosynthesis
the experiments performed by these and other
scientists reveal that
• in the presence of light
– plants transform carbon dioxide and water
– into carbohydrates and release oxygen
Cell Energy
Light energy
chloroplast
Carbon dioxide + water
Sugars + oxygen
Cell Energy
Photosynthesis Equation
light
6CO2 + 6H2O
carbon dioxide + water
C6H12O6 + 6O2
sugar + oxygen
Cell Energy
Light and Pigments
In addition to water and carbon dioxide,
photosynthesis requires?
• light &?
• chlorophyll, a molecule in chloroplasts
Cell Energy
Light and Pigments
energy from the sun travels to the Earth in many
forms.
• one of these forms is light (sunlight) which
your eyes perceive as ‘white light’
– it is actually a mixture of different
wavelengths of light
– many of these wavelengths are visible to
your eyes and are referred to as the visible
spectrum
–R O Y G B I V
Cell Energy
Light and Pigments
• plants gather the sun’s energy with lightabsorbing molecules called pigments
• the plants principal pigment is chlorophyll
– there are 2 main types of chlorophyll
• chlorophyll a and chlorophyll b
Absorption of light by
chlorophyll a and chlorophyll b
Cell Energy
chlorophyll b
chlorophyll a
chlorophyll absorbs light very well in the
blue and red regions
however, it does not absorb it very well in
the green and yellow regions
Cell Energy
Light and Pigments
• light is a form of energy, any compound that
absorbs light also absorbs the energy from
that light.
• when chlorophyll absorbs light much of the
energy is transferred directly to electrons in
the chlorophyll molecules, raising the energy
levels of these electrons
• these high energy electrons make
photosynthesis work
Cell Energy
Inside a Chloroplast
• thylakoid membranes
– saclike photosynthetic membranes
– contain clusters of chlorophyll and other
pigments and proteins known as
photosystems
– able to capture the energy of sunlight
• grana – (singular: granum) stacks of
thylakoids
• stroma – fluid region outside the thylakoid
membranes
Cell Energy
Photosynthesis
• light-dependent reactions
– occurs in the __________ _________
Cell Energy
Photosynthesis
• light-dependent reactions
– occurs in the thylakoid membranes
Cell Energy
Photosynthesis
lightdependent
reactions
Chloroplast
Cell Energy
Photosynthesis
• light-dependent reactions
– occurs in the thylakoid membranes
– requires – ?
Cell Energy
Photosynthesis
• light-dependent reactions
– occurs in the thylakoid membranes
– requires – light energy, water & raw
materials
Cell Energy
Photosynthesis
light
H 2O
raw
materials
lightdependent
reactions
Chloroplast
Cell Energy
Photosynthesis
• light-dependent reactions
– occurs in the thylakoid membranes
– requires – light energy, water & raw
materials
– produces – ?
Cell Energy
Photosynthesis
• light-dependent reactions
– occurs in the thylakoid membranes
– requires – light energy, water & raw
materials
– produces – oxygen, ATP & NADPH
Cell Energy
Photosynthesis
light
H 2O
lightdependent
reactions
Chloroplast
O2
ATP
NADPH
Cell Energy
Photosynthesis
• light-independent reactions
– also referred to as the ?
• Calvin cycle
– occurs in the ?
• stroma
Cell Energy
Photosynthesis
light
H 2O
lightdependent
reactions
Chloroplast
O2
Calvin
Cycle
ATP
NADPH
Cell Energy
Photosynthesis
• light-independent reactions
– also referred to as the ?
• Calvin cycle
– occurs in the ?
• stroma
– requires?
• carbon dioxide, ATP & NADPH
Cell Energy
Photosynthesis
light
lightdependent
reactions
Chloroplast
CO2
H 2O
O2
Calvin
Cycle
ATP
NADPH
Cell Energy
Photosynthesis
• light-independent reactions
– also referred to as the ?
• Calvin cycle
– occurs in the ?
• stroma
– requires?
• carbon dioxide, ATP & NADPH
– produces?
• sugars, NADP+, & ADP + P
Cell Energy
Photosynthesis
light
CO2
H 2O
NADP
+
ADP
+P
lightdependent
reactions
Chloroplast
O2
Calvin
Cycle
ATP
NADPH
sugars
Cell Energy
NADPH
• when sunlight excites electrons in chlorophyll,
the electrons gain a great deal of energy
• a special carrier is needed to move these
high-energy electrons
– similar to hot coals of a fire
Cell Energy
NADPH
• carrier molecule
– compound that can accept a pair of highenergy electrons and transfer them along
with most of their energy to another
molecule
Cell Energy
NADPH
• NADP+ - carrier molecule that accepts and
holds 2 high-energy electrons along with a
hydrogen ion (H+)
– results in the production of NADPH
– this conversion to NADPH allows some
energy of light to be trapped in a chemical
form
– chemical energy can then be used by cell
for chemical reactions elsewhere in cell
Cell Energy
Light-Dependent Reactions
• Step A – Photosystem II
– pigments in photosystem II absorb light via
antenna complexes
– energy from light is absorbed by electrons –
increasing their energy level
– energy is then passed on to the electron
transport chain
– enzymes break up water molecules into
electrons, hydrogen ions (H+), and oxygen
Cell Energy
Light-Dependent Reactions
inner
thylakoid
membrane
thylakoid
membrane
Stroma
Cell Energy
Light-Dependent Reactions
• Step B – Electron transport chain (ETC)
– high-energy electrons move through
electron transport chain
– energy from electrons is used by molecules
to transport H+ ions from stroma to the inner
thylakoid
Cell Energy
Light-Dependent Reactions
inner
thylakoid
membrane
thylakoid
membrane
Stroma
Cell Energy
Light-Dependent Reactions
• Step C – Photosystem I
– Pigments in photosystem I use light energy
to reenergize the electrons
– NADP+ picks up these high-energy
electrons plus a H+ ion and becomes
NADPH
Cell Energy
Light-Dependent Reactions
inner
thylakoid
membrane
thylakoid
membrane
Stroma
Cell Energy
Light-Dependent Reactions
• Step D – Hydrogen Ion movement
– H+ ions released during water-splitting and
electron transport result in a slight positive
charge inside the thylakoid membrane and a
slight negative charge outside
Cell Energy
Light-Dependent Reactions
inner
thylakoid
membrane
thylakoid
membrane
Stroma
Cell Energy
Light-Dependent Reactions
• Step D – Hydrogen Ion movement
– H+ ions cannot cross the membrane directly
– membrane contains a protein called ATP
synthase that allows H+ ions to pass
through it
– as H+ ions pass through the protein, the
protein rotates like a turbine
– as it turns, ATP synthase binds ADP and a
phosphate group to form ATP
Cell Energy
Light-Dependent Reactions
inner
thylakoid
membrane
thylakoid
membrane
Stroma
Cell Energy
The Calvin Cycle
• Step A – CO2 enter the cycle
– six CO2 molecules enter cycle from
atmosphere
– they combine with six 5-carbon molecules
– the end result is twelve 3-carbon molecules
Cell Energy
The Calvin Cycle
Cell Energy
The Calvin Cycle
• Step B – Energy input
– the twelve 3-carbon molecules are
converted into higher-energy forms
– energy for this conversion comes from ATP
and high-energy electrons of NADPH
Cell Energy
The Calvin Cycle
Cell Energy
The Calvin Cycle
• Step C – 6-carbon sugar produced
– two of the twelve 3-carbon molecules are
converted into two similar 3-carbon
molecules
– These molecules are used to form various
6-carbon sugars and other compounds
Cell Energy
The Calvin Cycle
Cell Energy
The Calvin Cycle
• Step D – 5-carbon molecules regenerated
– The remaining ten 3-carbon molecules are
converted back into six 5-carbon molecules
– These molecules combine with six new CO2
molecules to begin the next cycle
Cell Energy
The Calvin Cycle
Cell Energy
Factors affecting photosynthesis
• water
– because it is a raw material, a shortage can
slow or stop process
• temperature
– enzymes used in process work best
between 0o C and 35o C. Temps above or
below range may damage enzymes and
slow down process
• intensity of light
– increasing intensity also increases rate of
photosynthesis up to a certain point