Cellular Energy

Potential vs. Kinetic Energy Potential = stored Kinetic = motion

What kind of energy do cells use? ATP (adenosine triphosphate) The high energy is stored in the last P bond 3 Phosphates Ribose Sugar Adenine Base

Where do we get ATP? Our bodies have less than a gram of ATP! Our cells must recycle ATP

Recycling ATP Occurs in the cytoplasm and mitochondria We use the energy in glucose to reattach phosphates to ADP. This process is called Cellular Respiration Occurs in the cytoplasm and mitochondria

Cellular Respiration 1 Glucose = 38 ATP

Overview of Cellular Respiration Four stages: Glycolysis Transition Reaction Citric Acid Cycle Electron Transport Chain

Cellular Respiration Electron Transport Chain NADH FADH2 GLYCOLYSIS Glucose Pyruvate CITRIC ACID CYCLE Electron Transport Chain Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion and High-energy electrons carried by NADH ATP CO2 Cytoplasm

1. Glycolysis (cytoplasm) Glucose (6-carbon chain) is broken down to two Pyruvates (3-carbon chains) This cost 2 ATPs, but produced 4 ATPs Net gain = 2 ATPs In the process, 2 H+ ions combine with NAD+ to form NADH molecules – electron carriers Net gain = 2 NADH

2. Transition Reaction 2 Pyruvates (3-carbon chains) react with coenzyme A (CoA) to form 2 acetyl CoA’s (2- carbon chains) CoA is like a trailer loading up carbon to get into the Mitochondria Output = 2 CO2 Net gain = 2 NADH

Acetyl CoA (acetyl coenzyme A) Pyruvate NAD+ NADH + H+ CoA Acetyl CoA (acetyl coenzyme A) Coenzyme A Figure 6.8

3. Citric Acid Cycle (Krebs) In Mitochondria CoA drops off 2-C chain which combines with a 4-C compound to form a 6-C chain Through the cycle Carbons are snapped off and released as CO2 For 2 trips around the cycle: 4 CO2 released 6 NADH made 2 FADH2 made 2 ATP made

4. Electron Transport Chain (ETC) Located on inner membrane of Mitochondria Electrons from NADH and FADH2 Travel down the electron transport chain to oxygen, which picks up H+ to form water (H2O) Electron movement causes an H+ gradient H ions rush through ATP enzyme producing: NADH  3 ATP 10 NADH = 30 ATP FADH2  2 ATP 2 FADH2 = 4 ATP

Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron flow Electron carrier NADH NAD+ FADH2 FAD H2O ATP ADP ATP synthase H+ + P O2 Electron Transport Chain Chemiosmosis . OXIDATIVE PHOSPHORYLATION + 2 1 2 Figure 6.10

Electron Transport Chain Animation

Cellular Respiration Electron Transport Chain NADH FADH2 GLYCOLYSIS Glucose Pyruvate CITRIC ACID CYCLE Electron Transport Chain Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion and High-energy electrons carried by NADH ATP CO2 Cytoplasm

Photosynthesis

Can you account for everything? Cellular Respiration! Photosynthesis! Light energy 6 CO2 + H2O Carbon dioxide Water C6H12O6 O2 Glucose Oxygen gas

Potential vs. Kinetic Energy Through the process of photosynthesis, plants can store energy by making glucose.

They are so good at it that they make enough for us too! Plants are autotrophs They make their own food (sugars) They are so good at it that they make enough for us too! Plant cells full of chloroplasts!

Light Reactions Thylakoids – stacks of chlorophyll inside the chloroplast Wavelengths of visible light are absorbed by plant pigments This drives the light reactions of photosynthesis Increasing energy 10–5 nm 10–3 nm 1 nm 103 nm 106 nm 1 m 103 m Gamma rays X-rays UV Infrared Micro- waves Radio Visible light 400 500 600 700 750 650 nm Wavelength (nm) Transmitted light Absorbed Reflected Light Chloroplast 380

Light Reaction 18 ATPs will help make 1 glucose Photo system 1 & 2 Photons from sun split water into O2 (released) and H+ Photons absorbed by chlorophyll excite H+ ions H+ ions are passed between photosystems until they reach final electron carriers = NADPH The final H+ ion cycles six times to make a total of 18 ATPs Net gain = 12 NADPH and 18 ATP 18 ATPs will help make 1 glucose

Calvin Cycle ATP and NADPH from light reaction powers sugar production in the Calvin cycle Plant is taking in CO2 3 (5-Carbon) chains cycle around picking up CO2 Each cycle makes half a sugar, so two cycles will make a full sugar

TA-DA!!! Light energy 6 CO2 + H2O Carbon dioxide Water C6H12O6 O2 Glucose Oxygen gas