Autotroph photosynthesis Nutrition Herbivores Carnivores Omnivores Heterotroph.
Cell Energy & Photosynthesis. Source of Energy In most living organisms the energy in most food...
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Transcript of Cell Energy & Photosynthesis. Source of Energy In most living organisms the energy in most food...
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
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
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
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
Adenosine Diphosphate (ADP) + phosphate
Partiallychargedbattery
energy
ATP – stored energy
Cell Energy
ATP – stored energy
Adenosine Diphosphate (ADP) + phosphate
Partiallychargedbattery
Adenosine triphosphate (ATP)energy
Cell Energy
ATP – stored energy
Adenosine Diphosphate (ADP) + phosphate
Partiallychargedbattery
Adenosine triphosphate (ATP)
Fullychargedbattery
energy
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 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
Photosynthesis Equation
light
6CO2 + 6H2O C6H12O6 + 6O2
carbon dioxide + water 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 light-absorbing molecules called pigments
• the plants principal pigment is chlorophyll
– there are 2 main types of chlorophyll
• chlorophyll a and chlorophyll b
Cell Energy
Absorption of light bychlorophyll a and chlorophyll b
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 thylakoid membranes
– requires – ?
Cell Energy
Photosynthesis• light-dependent reactions
– occurs in the thylakoid membranes
– requires – light energy, water & raw materials
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-independent reactions
– also referred to as the ?
• Calvin cycle
– occurs in the ?
• stroma
Cell Energy
Photosynthesis• light-independent reactions
– also referred to as the ?
• Calvin cycle
– occurs in the ?
• stroma– requires?
• carbon dioxide, ATP & NADPH
Cell Energy
Chloroplast
light-dependentreactions
lightH2O
O2
ATPNADPH
CalvinCycle
CO2
Photosynthesis
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
Chloroplast
light-dependentreactions
lightH2O
O2
ATPNADPH
CalvinCycle
CO2
sugars
ADP + PNADP+
Photosynthesis
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 high-energy 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
• 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
• 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
• 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
• 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
Z – scheme: PII & PI
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
• 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
• 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
• 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
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
Cell Energy