Cell Energy: Photosynthesis Academic: Chapter 8 Honors: Chapter 7

Energy- Ability to do work No energy = no life Laws of thermodynamics Energy and life Energy- Ability to do work No energy = no life Laws of thermodynamics First law- energy can be converted from one form to another, but it cannot be created nor destroyed. Second law- energy cannot be converted without the loss of useable energy (thermal energy/heat) Example : Food chains

Forms of Energy Energy comes in many forms: Light Heat Electricity . . . Energy can also be stored in the bonds of chemical compounds.

Autotrophs and heterotrophs Autotrophs- organisms that make their own food from energy from the sun or other sources Known as producers Heterotrophs- organisms that need to ingest or consume food to obtain energy Known as consumers ALL organisms have to release the energy in sugars and other compounds to live.

Metabolism- all of the chemical reactions in a cell Photosynthesis- light energy from the sun is converted into chemical energy for use by the cell Cellular respiration- Organic molecules are broken down to release energy for use by the cell.

Chemical Energy and atp ATP- Adenosine Triphosphate- Energy for the cell Made of adenosine, ribose and three phosphates ATP releases energy when the bond between the second and third phosphate groups is broken, forming a molecule called adenosine diphosphate (ADP) and a free phosphate ADP + P

CHEMICAL ENERGY AND ATP (Not in notes) Storing energy- when bonds are formed, energy is stored ADP- Adenosine diphosphate is similar to ATP, but with two phosphates instead of three Energy is stored when another phosphate is added to ADP

Energy is released when bonds are broken Releasing energy Energy is released when bonds are broken When a phosphate is removed from ATP, energy is released As many as two phosphates can be removed from ATP Remove one phosphate = ADP Remove two phosphates = AMP (Adenosine Monophosphate)

Using biochemical energy 1. Cells use ATP for active transport, to move organelles in the cell, and to synthesize proteins and nucleic acids 2. Cells do not keep large amounts of ATP in the cell. The cell can regenerate ATP from glucose as needed Cellular Respiration 3. ATP is great for transferring energy, but not for storing it.

Where do trees get their mass from? Veritasium Video Video from: http://www.youtube.com/watch?v=2KZb2_vcNTg

Photosynthesis overview Photosynthesis- The process by which plants use sunlight to convert water and carbon dioxide into sugar The photosynthesis equation: 6 CO2 + 6 H20  C6H12O6 + 6 O2 Carbon dioxide and water  sugar and oxygen What are the products and the reactants?

photosynthesis requires light Light is a mixture of wavelengths – ROY G BIV Pigments- light absorbing molecules- there are different types of pigments Chlorophyll- principal pigment that absorbs light in the blue-violet and red regions, but not the green There are accessory pigments: like carotenoids (think carrot) Chlorophyll is found in the chloroplasts of leaves This is why chloroplasts look green

Chlorophyll a & b Blue and red Chlorophyll is best at absorbing ____________ Does not absorb ______________________ Green and yellow

Blackest Substance

Photosynthesis Reactions Photosynthesis occurs within the chloroplasts of specialized cells within the leaves of plants.

Parts of the Chloroplast Stroma – Liquid inside the chloroplast. Surrounds the thylakoid membranes. Grana – (granum plural) Stacks of thylakoid membranes Thylakoid – Membranes containing photosystems Photosystems – Light capturing systems Parts of the Chloroplast

Draw this in your notes

Two Processes of Photosynthesis 1. Light Dependent Reaction 2. Calvin Cycle (Light Independent Reaction)

The light reaction Takes place in the membrane of the thylakoids

Steps to the light reaction: Thylakoid membrane 1. Photons of light strike photosystem II in the thylakoid membrane Light dependent 2. This causes water to split H2O  H+ AND O The hydrogen's are now positive (protons) because the e- (electron) that they had are now “excited” and move to the Electron Transport Chain- ETC ETC- think of a frying pan to move hot coal…… As the e- travels through the ETC, the energy is used to pump more H+ into the thylakoid space

The oxygen leaves out the stomata (pores in the leaf) The H+ remain in the inside of the thylakoid 3. The e- travels through the ETC until it reaches photosystem I where it is re-excited with another photon of light 4. The re-excited electron is used to convert NADP+ into NADPH NADP+ is an electron carrier that will take the electrons into the second phase of photosynthesis

5. The H+ (protons) that are now in a HIGH concentration in the thylakoid space are now used to create ATP from ADP. As they flow through to the stroma they pass through a protein that adds a phosphate to ADP (ADP + P = ATP) 6. The ATP and the NADPH now head to the Calvin Cycle to act as the energy to drive the reaction Summary: Reactants- H20 and Light Products – O2 ( as waste), ATP and NADPH

The Calvin Cycle Takes place in the stroma (empty space)

Steps to the Calvin cycle: stroma The ATP and NADPH from the light reaction are used to “fuel “ the Calvin Cycle 1. (6) CO2 enter through the stomata (pores in the leaf) 2. CO2 combines with a (6) 5-carbon sugar Ribulose (1+5=6) (6) 6-carbon sugars! 3.The 6 carbon sugars are then broken down into 12 3-carbon sugars Because they were unstable 4. The 2 3-carbon sugars leave to make Glucose 5. The remaining 3-carbon sugars continue in the cycle for the next round

What it really looks like

Summary of the Calvin cycle Reactants- ATP, NADPH , and CO2 Products: Glucose

Summary of photosynthesis Two step process 1. Light Dependent Reaction in the Thylakoid membrane 2. Light Independent Reaction (Calvin Cycle) in the Stroma The reactants : CO2 and H2O The products: C6H12O6 AND O2

What effects the rate of photosynthesis? Temperature CO2 Light Water