Photosynthesis

Cellular Respiration

6CO2 + 6H2O  C6H12O6 + 6O2 Photosynthesis Carbon dioxide + water  glucose + oxygen

Chloroplast

ATP Adenosine Triphosphate

ATP & ADP ATP: Adenosine triphosphate adenine + ribose + 3 phosphates Energy storing molecule Source of all cell energy When one phosphate group breaks off, energy is released ADP = Adenosine Diphosphate Adenine 3 Phosphate groups Ribose

ADP: Adenosine diphosphate Adenine + ribose + 2 phosphates Molecule that results from ATP losing one P Another P may be added later ADP ATP Energy Energy Adenosine diphosphate (ADP) + Phosphate Adenosine triphosphate (ATP) Partially charged battery Fully charged battery

Overview Photosynthesis Photosynthesis: process using energy from sunlight to convert water and CO2  carbohydrates (glucose) & oxygen Two parts: Light dependent reactions: produce O2 & converts ADP to ATP Calvin cycle (dark reactions), Light independent reactions: use ATP from light reactions to produce sugar Light Energy Chloroplast CO2 + H2O Sugars + O2

Moves energy to electrons that drive reactions Chlorophyll: green pigment in cells that absorbs blue & red light energy (does NOT absorb light in the green area of the spectrum) Moves energy to electrons that drive reactions FORMULA: 6CO2 + 6H2O  C6H12O6 + 6O2 Sugars Chloroplast Light- Dependent Reactions Calvin Cycle

Chloroplast

Thylakoid: saclike photosynthetic membranes arranged in stacks called granum Stroma = area outside the thylakoid membrane Light Dependent Reaction: thylakoid Light Independent Reaction aka Calvin Cycle: Stroma

Light Dependent Reaction

Photosystem II Happens first (but was discovered after Photosystem I) E (from light) is absorbed by e These high E electrons are passed on to the electron transport chain H2O molecules are broken into 2H+, 1 oxygen molecule, and 2 electrons (these electrons are then used at the beginning of the elec trans chain)

Electron Transport Chain High E electrons move through chain to Photosystem I The E from the electrons is used to move H+ from stroma into the thylakoid

Photosystem I E from light is added (again) to the electrons These high E electrons are picked up by electron carriers (NADPH+) at the outer surface of the thylakoid NADPH+ converts to NADPH when electron is added

Hydrogen Ion Movement Inside of thylakoid membrane is positively charged (result of H+ released when H2O molecule was split) Outside of thylakoid is negatively charged (comparatively)

ATP Formation The H+ ions pass through thylakoid membrane, getting “spun” by ATP synthase This action allows ADP to convert to ATP

Calvin Cycle aka Light Independent Cycle

6CO2 enter(from atmosphere) combining with 6 5-carbon molecules Yield = 12 3-carbon molecules

E from ATP and the high E electrons in NADPH convert the 12 3-carbon molecules to high E molecules ATPADP NADPHNADP+

2/12 of 3-carbon molecules are used to form various 6-carbon sugars

Remaining (10) 3-carbon molecules re-enter the cycle as 6 5-carbon molecules

Van Helmont (1643)

Priestley (1771)

Ingenhousz (1779)

What affects photosynthesis? Water shortage Intensity of light Temperature CO2

Cellular Respiration Process that releases E by breaking down glucose in the presence of oxygen

Cellular Respiration

Glycolysis Begins this process If O2 present: leads to 2 pathways that release a lot of E If O2 not present: a different pathway is followed Glycolysis: happens in cytoplasm Krebs Cycle: happens in mitochondrion Electron Transport Chain: mitochondrion

If Oxygen is Present: Glycolysis is followed by Krebs cycle and the electron transport chain Glycolysis/Krebs Cycle/Electron Transport= Cellular Respiration Oxygen + Glucose  Carbon Dioxide + Water + ENERGY

Glycolysis 1st set of reactions in cellular respiration 1 molecule of glucose is broken in half yielding 2 molecules of pyruvic acid Needs 2 ATPs to get started; yields 4 ATPs Net gain of 2 ATPs

Glycolysis Removes 4 high E electrons and passes them to NAD+ (an electron carrier) Thousands of ATPs produced in milliseconds in cells No oxygen required NAD+ get filled up with electrons so ATP production stops

Krebs Cycle aka Citric Acid Cycle Occurs in mitochondrion Pyruvic acid (from glycolysis) is used to make CO2 NADH, ATP, FADH2 also produced

Krebs Cycle Begins when pyruvic acid enters mitochondrion One C removed (forming CO2 ) Citric Acid is formed Citric Acid then broken down More CO2 is released 1 ATP is formed 4NADH & 1FADH2 also formed (electron carrier molecules)

Electron Transport Chain Uses the high E electrons from the Krebs Cycle to convert ADP  ATP NADH & FADH2 passed into/along the e transport chain High E electrons help transport H+ ions across the membranes affect the charge inside/outside the membrane Enzymes help attach a phosphate to ADP, converting ADP  ATP

What happens to pyruvic acid during Krebs Cycle? It’s broken down into CO2 in a series of energy extracting reactions How does the e transport chain use the high E electrons from Krebs cycle? To convert ADP  ATP Why is cellular respiration more efficient than Krebs Cycle alone? 34 (additional) ATPs produced in Cellular Respiration/2 ATPs produced in Glycolysis

What happens if no O2 is available? Fermentation (anaerobic) Alcoholic Fermentation Yeasts and other microorganisms Forms ethyl alcohol & CO2 as wastes Forms “bubbles” in bread

What happens if no O2 is available? Lactic Acid Fermentation (anaerobic) Forms lactic acid as waste Causes “burn” in muscles Creates “oxygen debt”

Photosynthesis & Cellular Respiration