Energy and Photosynthesis

S. Burnham

Biology

HHS

Energy in Living Things

Two Groups of Living Organisms in the Way they meet their Energy needs: Autotrophs: plants and other living things that

build organic molecules from inorganic substances internally (auto-by themselves)

Heterotrophs: organsims that do not make their own food but depend on autotrophs for their food directly or indirectly (hetero – different)

How do autotrophs make their own food?

Photosynthesis

Almost all of the Energy on the Earth comes from the Sun and it drives the chemical reactions that creates all other forms of energy in life.

Therefore, most all autotrophs get their food directly or indirectly from the sun.

Photosynthesis

The Sun’s energy is trapped in the organelles of a plant cell called the CHLOROPLAST, which is a type of PLASTID.

It uses the suns energy with the help of chlorophyll,CO2, AND H2O to produce glucose and O2 .

Photosynthesis

Is the process of breaking that Glucose molecule down and releasing that stored energy and Oxygen.

Overall-Photosynthesis-Allows Plants to take in Light and Carbon dioxide- turn it in to Sugar and release Oxygen into the atmosphere---Yipee.

ATP

USABLE Energy is stored in a molecule called ATP.

ADENOSINE TRI PHOSPHATE

ATP

THREE PARTS: Adenine Ribose 3 Phosphate groups Its written as A-P-P-P the energy is

between the P’s. When the P bonds are broken energy is released.

Biochemical Cycle-ATP-ADP

Those P bonds must be broken before cells can use the energy stored in ATP.

An enzyme (a Protein that CUTS stuff) called ATPase---- -ase means to cut whatever the word is in front of it…is sent out to cut the bond between the 2nd and 3rd Phosphate group

ADP is formed.(If ATP is triphosphate…what is ADP?)

ATP-ADP Cycle continuedSo, then energy is released…and then

ATPase comes along and breaks the P bond between the 1st and 2nd P group and you are left with AMP and energy.

(If ADP is Adenosine Diphosphate- I wonder what AMP stands for)

ATP-ADP Cycle continued

The formation of ADP or ATP is the reverse of its breakdown. It occurs with the help of an enzyme (protein) called ATP synthetase….a protein that builds-not breaks.

Photosynthesis-Chemical ReactionsPhostosynthesis:Sun Energy+6CO2+6H20

This chemical reaction takes place in basically two steps: Light and Dark reactions

C6H12O6+6O2

Photosynthesis-Chemical ReactionsThe light reactions-which require light

to form ATP and the Hydrogen carrier molecule

The dark reactions- which require no light to use ATP and Carbon dioxide to form sugar

The ChloroplastBoth the Light and Dark reactions take

place in the Chloroplast.OrganelleA number of Chloroplasts in Plant CellsPlant cell onlyStructure of Chloroplast:

Thylakoid, lumen, grana, stroma – see page 208

Plant cell and chloroplast

Chlorophyll

Primary pigment of plantsJob is to capture sun’s raysWhen sun’s rays…blue and red only

are captured, the green rays are reflected and thus plants are seen as green.

Chlorophyll

When Chlorophyll absorb those waves their molecules are excited and electrons jump off ..which is necessary for photosynthesis.

Light ReactionsPAY ATTENTION OR YOU WILL GET

LOST….Sunlight hits chlorophyllChlorophyll’s electrons get excited and one

escapes….this happens more than once during photosynthesis

Two molecules of water are split. Two hydrogens form ions H+. Then the two Oxygen ions come together to form Oxygen gas and are released into the atmosphere.

Two more Molecules

The Hydrogen Ions that split from the water are picked up by NADP-to form NADPH—its just a bucket used to pick up H’s. Now if the H+s build up, the cell becomes like a magnet and it needs to be balanced out by electrons (e-’s) They both travel up and down the electron transport chain creating ENERGY to be used in the next reaction and the H+s are carried over for the next reaction…IN THE DARK.

Let me give you the overall equation for Photosynthesis and you can see just how much we have covered:

Energy from Sun+6CO2+6H20 C6H12O6 +6O2

So what have we used so far?

Dark Reactions or the CALVIN CYCLEThese are called the Dark reactions because they

do not require sunlight to occur. BUT they do require the ATP and NADPH from the light dep. Reactions to occur.

This time CO2 enters the plant and mixes with the ATP and NADPH to form a 6 carbon sugar called GLUCOSE.

This cycle has to happen 6 times just to get 1 molecule of glucose.

IN REVIEWGlucose is the product of Photosynthesis as well as

Oxygen…However, plants store the glucose and release the oxygen.

So to reviewPhotosynthesis happens in the chloroplasts.Light dep. Reactions happen in the thylakoidLight indep. reactions happen in the stromaLight dep. Uses light to form ATP, NADPH, split water

and make oxygen gasLight indep. Brings in carbon dioxide plus all of the stuff

from light dep. Reactions to make six turns of the CALVIN cycle to produce glucose.

Cellular Respiration

If animals and other life forms use a process that is directly reversed from the plants…what would its equation look like?

Energy from Sun+6CO2+6H20

Or ATPCELLULAR RESPIRATION??????

C6H12O6 +6O2

RespirationBefore food can be used to perform work its

energy must be released in the process of respiration.

There are two forms of respiration:AerobicAnerobic

Aerobic RespirationBasically, how do humans use sugar or food as

chemical energy?Please look at the following formula:

C6H12O6 +6O2 6CO2+6H20 + 38 ATP REACTANTS PRODUCTS

Basically

Sugar and Oxygen break down and give off water, Carbon Dioxide, and 38 molecules of Energy.

This happens in 3 STAGESGLYCOLYSISKREB’s CYCLE

ELECTRON TRANSPORT CHAIN

ReviewGlycolysis which occurs without oxygen and

turns glucose into Pyruvic Acid ( which is a 3-carbon molecule)…takes place in the cytoplasm of the cell.

KREB’s CYCLE occurs in the MITOCHONDRIA and turns pyruvic acid into citric acid and ATP and Carbon dioxide.

And the electron transport chain helps take the NADH and combine it with O2 to make water.

The Formation of ATPThe Electron Transport Chain…. In the inner membrane of the

mitochondria ..it acts like a giant magnet… the positive parts of the magnet are the H+ molecules of the NADH+H and the FADH and H+ molecules…as they move through the membrane they attract electrons which are negative particles of the magnet.

The formation of Water and ATPAt the end of this magnet…oxygen picks up some Hydrogens and makes a

water molecule.Now did you know that the word “electricity”

comes from the movement of electrons…so, as our electrons in this inner membrane of the mitochondria are moving with the Hydrogens as a magnet, they are creating enough energy to help that enzyme ATP synthetase to create molecules of ATP and that is why ATP is found in the mitochondria.

Anerobic Respiration

Anerobic respiration is the breakdown of food into energy without the use of oxygen.

So, if you are not breathing properly, you will undergo glycolysis-break down of glucose into pyruvic acid- but the acid will turn into either ALCOHOL or LACTIC ACID…which one do animals do?

Fermentation-anerobic respirationThe breakdown of Pyruvic Acid without the

use of oxygen to form LACTIC ACID or ALCOHOL

Fermentation occurs in two forms: Lactic Acid –when pyruvic acid is turned into

lactic acid-which pierces muscle cells in animals

Alcoholic Fermentation – occurs in some plant and yeast cells as pyruvic acid is converted into ethyl alcohol without the use of oxygen

Aerobic Respiration

Pathways of cellular respiration require oxygen

Cellular respiration releases energy by breaking down glucose and other food molecules in the presence of oxygen!