Cell Energy & Photosynthesis. Source of Energy In most living organisms the energy in most food comes from? the sun autotroph – ‘auto’ – self, ‘troph’

Cell

Energy & Photosynthesis

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

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Adenine

Cell Energy

adenosine tri-phosphate (ATP)

Stored Energy




– a nitrogen-containing compound – adenine

– a 5-carbon sugar - ribose

Cell Energy


Adenine Ribose

Cell Energy

Stored Energy




– a nitrogen-containing compound – adenine

– a 5-carbon sugar – ribose

– and 3 phosphate groups

Cell Energy

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


Partiallychargedbattery


Cell Energy



energy


Cell Energy




Adenosine triphosphate (ATP)energy

Cell Energy




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

Is there another molecule similar to ATP & ADP?

AMP

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

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ATP-ADP cycle

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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?

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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

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Photosynthesis Equation

light

6CO2 + 6H2O C6H12O6 + 6O2

carbon dioxide + water sugar + oxygen

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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

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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

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Photosynthesis• light-dependent reactions

– occurs in the __________ _________

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– occurs in the thylakoid membranes

Cell Energy

Chloroplast

light-dependentreactions

Photosynthesis

Cell Energy



– requires – ?

Cell Energy



– requires – light energy, water & raw materials

Cell Energy

Chloroplast


lightH2O

rawmaterials

Photosynthesis

Cell Energy




– produces – ?

Cell Energy




– produces – oxygen, ATP & NADPH

Cell Energy

Chloroplast


lightH2O

O2

ATPNADPH

PhotosynthesisCell Energy

Photosynthesis• light-independent reactions

– also referred to as the ?

• Calvin cycle

– occurs in the ?

• stroma

Cell Energy

Chloroplast


lightH2O

O2

ATPNADPH

CalvinCycle

Photosynthesis

Cell Energy



• Calvin cycle

– occurs in the ?

• stroma– requires?

• carbon dioxide, ATP & NADPH

Cell Energy

Chloroplast


lightH2O

O2

ATPNADPH

CalvinCycle

CO2

Photosynthesis

Cell Energy



• Calvin cycle

– occurs in the ?

• stroma– requires?

• carbon dioxide, ATP & NADPH– produces?

• sugars, NADP+, & ADP + P

Cell Energy

Chloroplast


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

Stroma

innerthylakoid

membrane

thylakoidmembrane

Cell Energy



• 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

Stroma

innerthylakoid

membrane

thylakoidmembrane

Cell Energy



• 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

Stroma

innerthylakoid

membrane

thylakoidmembrane

Cell Energy



• 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

Stroma

innerthylakoid

membrane

thylakoidmembrane

Cell Energy



• 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

Stroma

innerthylakoid

membrane

thylakoidmembrane

Cell Energy


Z – scheme: PII & PI

http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf



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

Cell Energy

The Calvin Cycle

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

Cell Energy

The Calvin Cycle

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

Cell Energy

The Calvin Cycle

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

Cell Energy

The Calvin Cycle

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

Documents

Cell Energy & Photosynthesis. Source of Energy In most living organisms the energy in most food comes from? the sun autotroph – ‘auto’ – self, ‘troph’