Basic Metabolism: Respiration and Photosynthesis • Respiration: Breakdown of fuel (food) molecules to release energy. • All living organisms. • Photos...
Basic Metabolism: Respiration and Photosynthesis • Respiration: Breakdown of fuel (food) molecules to release energy. • All living organisms. • Photosynthesis: Using sunlight energy & atmospheric CO2 to make food molecules. • Autotrophs.
Chapter 6: Cellular Respiration: Obtaining Energy for Food (P. 91) • Breakdown of fuel organic molecules to release energy (& generate ATP). • Aerobic respiration: (p. 94). • Respiration pathway that requires oxygen • Main pathway of most organisms. • Overview: equation for aerobic respiration (p. 96): • C6H12O6 (carbohydrate) + O2 6CO2 + 6H2O + energy.
The 3 Steps of Aerobic Respiration Step 1: Glycolysis: (p. 96-99) • Starts with sugar glucose (6 carbons): • Split into two pyruvate (=pyruvic acid) (3C). • Releases energy: • 2 ATP formed /glucose • Energized electrons captured by NAD+. • The most primitive pathway: occurs in cytoplasm of all cells. • Can go forward without oxygen: • = Anaerobic respiration.
2: Citric Acid (=Krebs) Cycle (p. 98) (Including Acetyl CoA formation step) • Pyruvate completely broken down to CO2. • Mitochondrial matrix (inner compartment. • Non-sugars may enter here: • fragments of fatty acids, amino acids, etc. • Produces 2 ATP/ glucose. • Captures energized electrons & holds them on a coenzyme called NADH. (also related FADH2) Folded inner membrane
Matrix (inner compartment)
Outer compartment (between membranes)
Mitochondrion
Outer membrane
3: Electron Transport System: The Big Energy Payoff (p. 99). • Mitochondrial inner membrane. • Electron transfer chains: • Use energized electrons captured during Gylcolysis & citric acid (krebs) cycle. • Electrons flow along series of membrane-embedded carriers. • flow generates ATP (p. 99) • Final electron acceptor is O2 • O2 combines with electrons & H+ to Form water. • Roughly 32 ATP formed per glucose.
Electron Transport System (mitochondrial inner membrane)
High
2 NADH
2 NAD+ Energy level
2H+ 4e-
Electron Transport proteins
ADP ATP
2H+
ADP ATP Low
4e-
O2
2H2O
Summing Up: The Energy Harvest (p. 100 )
• Glycolysis: • 2 ATP • Citric acid cycle: • 2 ATP • NADH & FADH2 – captured energized electrons: • generate 32-34 ATP during electron transfer. • Grand Total: 36-38 ATP • 4 directly + 32 from electron transfer.
Use of Substances Other than Sugar: (p. 100)
Food Proteins
Complex carbohydrates Simple sugars
Amino acids
Fats Glycerol
Glycolysis Pyruvate NH3
Acetyl CoA Krebs cycle O2 ADP
Electron Transfer
CO2 H2O ATP
Fatty acids
Anaerobic Harvest of Food Energy p. 101
• Oxygen-limited situations: • Glycolysis works alone: Fermentation. • But: NAD+ still captures electrons. • And: resulting NADH must get rid of them. • So: Pyruvate converted to ethyl alcohol (plants, yeasts) or lactic acid (animal/ human muscles, p. 101). • Yield: Only 2 ATP /glucose from glycolysis. • Some bacteria: use alternate electron acceptors (iron compounds, etc.) for electron transport. • Louisiana wetland soil (right): Gray colors result from bacteria using iron as a respiratory ereceptor. • ferric iron oxide (rust) transformed to ferrous oxides (gray).
Alcoholic Beverages (p.103): • Yeast ferments carbohydrates in grain, fruit or grapes under low oxygen conditions: • Wine: -------- grapes • Beer: --------- Barley, flavored with hops • Whiskey------ corn* • Vodka--------- wheat or potatoes* •
* Whiskey, Vodka and other hard liquors are distilled to concentrate the alcohol after fermentation.
Cheers!
Ch. 7 Photosynthesis: Using Light to Make Food (Energy Acquiring Pathways) • Basics of Photosyntheis (p. 108-109): • Energy + 6CO2+ 6H2O C6H12O6+ 6O2 • Reverse of respiration: • Synthesizes carbohydrates (food) • Location: Chloroplasts--in leaf mesophyll cells, etc. • The Players: photosynthetic autotrophs: • Produce the food for most ecosystems • Plants & green algae. • Photosynthetic (mostly aquatic) non-plant eukaryotes (kelps, diatoms, & others). • Photosynthetic bacteria (cyanobacteria, etc).
Chloroplasts: Sites of Photosynthesis (p. 109)
Location of Photosynthesis:
Leaf
Mesophyll cells
Chloroplasts
Sunlight as an Energy Source: Electromagnetic Energy Spectrum (P. 110) • Radio waves to X-rays & gamma rays. • Visible light: Only a small portion. • The Visible spectrum:
Uv-Violet-Blue-Green-Yellow-Orange-Red-IR. 400 nm
500 nm
600 nm
700 nm
2 Stages of Photosynthesis: 1) Light reactions: Converting solar energy to chemical energy (p. 110) • Location: chloroplast thylakoids. • Another electron transfer system! • Light energy generates flow of electrons. • ATP from ADP. • NADPH Captures energized electrons. • Electrons taken from water; byproduct: O2 • Main light-capturing pigment: Chlorophyll A (p. 112). • Also accessory pigments (p. 95). • Chlorophyll uses mainly Red & Blue/ violet light (p. 111).
How Light Reactions generate ATP & NADPH (Fig. 7.10, P. 113) 2nd acceptor High
1st acceptor 2e-
Energy 2elevel Light
Low
ADP
Water-splitting Photosystem
Electron Transport Chain
2e-
2eH+ NADP+ Light
ATP
2eH2O
NADPH-making Photosystem H+
+ 1/2O2
NADPH
2) The Calvin Cycle: Making Sugar from
Carbon Dioxide
(Also called 'Light Independent Reactions' or 'Carbon Fixation Reactions')
• The “Sugar Factory” (p. 115). • Power source: ATP & energized electrons from light reactions. • Location: Chloroplast interior or stroma. • Carbon fixation: • Carbon-dioxide (atmosphere) used to form glyceraldehyde 3 phosphate (PGAL or GP3). • PGAL is a 3-carbon sugar-phosphate. • Two combine to form phosphorylated Glucose. • GP3 (PGAL): The basic building block for all other organic molecules! • Multi-step process: reaction diagram, p. 115.
Sunlight-driven; on thylakoids. H2O split to obtain electrons & H+; O2 released. ATP formed. NADPH (electron source) formed.
• Calvion Cycle: • CO2 fixed, ATP & NADPH consumed, G3P (=PGAL) formed. • G3P (=PGAL) → glucose & all other organic molecules.
Energy Flow & Chemical Cycling in the Biosphere (p. 92-93 in ch 6):
Global Relationship Between Respiration & Photosynthesis Sunlight Energy Photosynthesis (Chloroplast) 6 CO2 + 6H2O
6 O2
C6H12O6
ATP Aerobic Respiration (Mitochondria)
ADP
Work
A Burning Concern: The Carbon Cycle & The Greenhouse Effect • Respiration & photosynthesis naturally in balance worldwide: • The "greenhouse effect" • Burning fossil fuels, deforestation cause Imbalance in this cycle. • Global Temperature increases & climate changes. • Catastrophic sea level rises. • More unstable/ extreme weather? More hurricanes? • 2011 drought? • Extinctions: climate changes faster than species can migrate.
