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Photosynthesis & Cellular Respiration

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Serena Boyaci

on 25 September 2012

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Transcript of Photosynthesis & Cellular Respiration

Photosynthesis & Cellular Respiration By Serena Boyaci & Angela Chung The process in which light energy is transferred to chemical energy. Photosynthesis

Both chlorophyll and other pigments within the chloroplast are able to absorb solar energy.

Plants convert solar energy to chemical energy.

Throughout the cell, chemical energy can be transported to other parts of the plant and kept in store. How it works... Stage 1: Absorbing solar energy and transferring it to electrons

Stage 2: Using the captured solar energy to make ATP and to transfer high-energy electrons to NADP->NADPH, which is then used as a high-energy electron carrier molecule

Stage 3: Using the energy stored in ATP and high-energy electrons carried by NADPH to form energy-rich organic molecules, like glucose, from CO2

The first two light-dependent stages occur in the thylakoid membranes of chloroplasts The 3 Stages Potential energy is released as it travels down the electron transport chain. What type of energy is released as electrons travel down the chain? In chloroplasts, chlorophyll and other pigments are found in clusters in the thylakoid membranes, the clusters are identified as photosystems.

There are two photosystems -photosystem I & II, their job is to capture solar energy when an electron in a chlorophyll molecule absorbs a photon. Photosystems The electrons that are removed from each photosystem must be replaced. The electrons that are being replaced come from water molecules, this process is called photolysis. How are the electrons that are removed from each photosystem replaced? What are the products of this process? The products of this process are hydrogen and oxygen. 1. Electrons from photosystem II are moved along an e;ectron transport chain and across the thylakoid membrane to the inner surface.
2. Part of their energy is used to "pull" hydrogen ions across the membrane which results in a buildup of positive charge in the lumen.
3. Low-energy electrons are transferred to chlorophyll molecules in the photosystem I -they absorb solar energy and become excited (high energy).
4. Excited electrons from photosystem I are transferred to NADP to make NADPH that goes to the calvin cycle. Steps in Electron Transfer During Light-Dependent Reactions of Photosynthesis Photosystems are located in the thylakoid membrane and they are found in clusters. Where are the photosystems located? What is the role of the photosystems? Their job is to capture solar energy when an electron in a chlorophyll molecule gets absorbed. What happens to an electron when a photon strikes the photosytem? Where does it go? Once a photon strikes the photosystem, the electron gets excited (has high energy) and is then passed to the electron transport chain. What is the released energy used to generate? The released energy is then used to capture ATP. What do electrons combine with after travelling down the chain? Electrons combine with H+ ions to make new compounds. Oxidation: atom or molecules loses electrons
Reduction: atom or molecule gains electrons

Molecules that lose electrons= Electron Donors
Molecules that gain electrons= Electron Acceptors

NADP+ is an acceptor (Taxi Cab)
NADPH is an electron donor

Losing electrons = absorbing energy
Gaining electrons= releasing energy Oxidation-Reduction Reactions The electrons that are energized in photosystem 1 do not pass across the thylakoid membrane, they are transferred to NADP+ The process of making ATP using the energy from an H+ ion gradient.

The diffusion of ions across a selectively permeable membrane. What is Chemiosmosis? *Light energy is consumed to produce ATP & NADPH* Glucose Overall, 18 ATP and 12 NADPH, 6 CO2 and 6H2O molecules are consumed to produce one molecule of glucose. Cellular Process in which cells produce the energy they need to survive. Animal and fungal cells combine together glucose molecules to form the storage compound glycogen. Plants produce starch for long-term storage from many glucose molecules. When cells require energy from a process, it must be supplied from ATP. The intermediate products including NADH, FADH2 and ATP are used by the cells. The transfer of electrson releases energy that can be used to make ATP, this ATP energy can be used in cellular respiration or other processes. Is energy absorbed or released when chemical bonds are formed? Is cellular respiration an extremely efficient process? Cellular respiration is not 100% efficient, 36% of the energy in a single glucose molecule is converted into the energy of ATP, the remaining 64% is released to heat. This benefits warm blooded animals because they use the thermal energy to maintain a constany body temperature. Aerobic: takes place in the presence of oxygen and involves the oxidization of glucose
End products = CO2(g), water, 36 ATP molecules

Anerobic: takes place in the absence of oxygen and glucose is not completely oxidized, there are two types of anerobic respiration with different end-products
1st stage: glycolysis
2nd stage: fermentation

*Both stages take place in the cytoplasm*

Aerobic respiration produces the most ATP= 36 Anaerobic and Aerobic Respiration -Takes place in the cytoplasm of the cell

-Glycolysis is an anaerobic process= does NOT require oxygen

-Two ATP molecules are used in the first stage of glycolysis, this shows an "investment of energy"

-The molecules that are consumed during glycolysis are glucose, 2 NAD+, 2 ATP and 4ADP

-The molecules that are produced during glycolysis are 2 pyruvate, 2NADH, 2ADP and 4 ATP Glycolysis Mitochondrion Pyruvate Oxidation: a chemical pathway that connects glycolysis in the cytoplasm
Krebs Cycle: located in the mitochondrial matrix
Electron Transport Chain: located in the inner membrane of the mitochondria Chemiosmosis Respiration The process of making ATP using the energy from a H+ ion gradient

The diffusion of ions across a selectively permeable membrane -Since two molecules of acetyl-CoA are formed from one molecule of glucose, the Krebs cycle occurs twice for each molecule of glucose processed
-As acetyl-CoA enters the cycle the CoA is released and can be used for the next pyruvate
-During one complete cycle a total of three NAD+s and one FAD are reduced to form three NADHs and one FADH2
-During one complete cycle an ADP and a Pi are combined to form one ATP
-During one complete cycle two CO2 molecules are produced which are then released as waste Krebs Cycle Approximately 36 ATP molecules are produced from one molecule of glucose.

Total theoretical ATP yield= 36 Aerobic cellular respiration includes four main stages:

Krebs cycle preparation
Krebs cycle
Electron transport chain AEROBIC CELLULAR RESPIRATION Stage 1: Glycolysis -10 step process
Stage 2: fermentation -recycles some of the products of glycolysis in two different pathways (CO2 & ethanol or lactic acid= final waste products) Anaerobic Eukaryotes: organisms whose cells contain nuclei, such as humans

Eukaryotes primarily use two methods:
alcohol fermentation
lactic acid fermentation Alcohol fermentation creates ethanol and carbon dioxide from glucose. In the process, NADH is oxidized to NAD+, allowing glycolysis to continue.

Humans make great use of these products, alcohol fermentation carried out by yeast is of great historical, economic and culturual importance. Alcohol Lactic acid fermentation produces lactic acid from glucose. In the process, NADH is oxidized to NAD+, allowing glycolysis to continue. Lactic Acid Fermentation Cellular Respiration Fermentation The End!! :)
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