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 Cell Energy

Adenine Cell Energy adenosine tri-phosphate (ATP)

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

Adenine Ribose3 Phosphate groups Cell Energy adenosine tri-phosphate (ATP)

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 3 rd 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

Adenosine Diphosphate (ADP) + phosphate Partially charged battery ATP – stored energy Cell Energy

Adenosine Diphosphate (ADP) + phosphate Partially charged battery energy ATP – stored energy Cell Energy

ATP – stored energy Adenosine Diphosphate (ADP) + phosphate Partially charged battery Adenosine triphosphate (ATP) energy Cell Energy

ATP – stored energy Adenosine Diphosphate (ADP) + phosphate Partially charged battery Adenosine triphosphate (ATP) Fully charged battery 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-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 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 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 by chlorophyll 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 __________ _________ Cell Energy

Photosynthesis light-dependent reactions –occurs in the thylakoid membranes Cell Energy

Chloroplast light- dependent reactions Photosynthesis 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

Chloroplast light- dependent reactions light H2OH2O raw materials Photosynthesis 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

Chloroplast light- dependent reactions light H2OH2O O2O2 ATP NADPH Photosynthesis Cell Energy

Photosynthesis light-independent reactions –also referred to as the ? Calvin cycle –occurs in the ? stroma Cell Energy

Chloroplast light- dependent reactions light H2OH2O O2O2 ATP NADPH Calvin Cycle Photosynthesis 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- dependent reactions light H2OH2O O2O2 ATP NADPH Calvin Cycle CO 2 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- dependent reactions light H2OH2O O2O2 ATP NADPH Calvin Cycle CO 2 sugars ADP + P NADP + 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 inner thylakoid membrane thylakoid membrane 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

Stroma inner thylakoid membrane thylakoid membrane 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

Stroma inner thylakoid membrane thylakoid membrane 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

Stroma inner thylakoid membrane thylakoid membrane 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

Stroma inner thylakoid membrane thylakoid membrane Cell Energy Light-Dependent Reactions

The Calvin Cycle Step A – CO 2 enter the cycle –six CO 2 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 CO 2 molecules to begin the next cycle 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 0 o C and 35 o 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