Bioenergetics: Photosynthesis and Cellular Respiration
Need-to-Know/SG-Academic Biology
Keystone Eligible Content:
A311 Describe the fundamental role of plastids (eg chloroplasts) and mitochondria in energy transformations.
A321 Compare the basic transformation of energy during photosynthesis and cellular respiration.
A322 Describe the role of ATP in biochemical reactions.
Photosynthesis
balanced chemical equation:
o
o
o
o
o
o
o
autotroph
heterotroph
Chemical Equation
 How does CO2 get into leaf?- stomata
Absorption of Sunlight
 Pigments
 Chlorophyll
 Wavelengths and colors of light absorbed
Chloroplast
 Structure - diagram
 Function
Light Reactions- require light
 Reactants: water, light energy, chlorophyll
 Stages:
 1. light absorption
o photosystems
 2. electron transport
o electron transport chain
 3. oxygen production
o water molecule split
 4. ATP production
o charge gradient between inside and outside membrane
o ADP ATP
 location: thylakoids
 Products:oxygen, ATP, NADPH
Dark Reactions – do not require light
 Other names: Calvin Cycle, Light Independent
 Reactants: NADPH, ATP, CO2 (enters through stomata on leaves)
 Stages:
 rubisco catalyzes 3-C molecules
 PGAL-can be recycled
 glucose
 location: stroma
 Products: glucose (C6H12O6)
Bioenergetics: Photosynthesis and Cellular Respiration
Need-to-Know/SG-Academic Biology
o
o
o
Energy Storing Compounds
 ATP v ADP
 Formation and importance
 NADP+ v NADPH
Describe how light and dark reactions work together
Factors that affect photosynthesis:
 1. temp
 2. light
 3. water
Photosynthesis vs. Respiration
- almost opposite processes
-equations are opposites
-Photosynthesis- deposits energy
-occurs only in plants, algae, and some bacteria
-Respiration withdraws energy
-takes place in all eukaryotes and some prokaryotes
Calorie- the amount of energy needed to raise 1 g. of water 1 degree Celsius
-cells gradually release energy from glucose
Cellular Respiration
6O2 + C6H12O6  6CO2 + 6H2O + ATP (Energy)
-the process that releases energy by breaking down food molecules in the presence of oxygen
3 Pathways: - each captures some of the energy available in food molecules and uses it to produce ATP
1. Glycolysis
2. Krebs Cycle
3. Electron Transport
1. Glycolysis
-process in which 1 molecule of glucose is broken in half, producing 2 molecules of pyruvic acid
-does NOT require oxygen
-location: cytoplasm
Uses: 2 stored ATP, 1 molecule of glucose
Makes: 4 ATP molecules, 2 molecules of pyruvic acid
NET GAIN: 2 ATP (2% of the total chemical energy in glucose), 2 molecules pyruvic acid
Oxidative Respiration
aerobic- requires oxygen – the reason we need to breathe (respire)!
respiration- process that involves oxygen and breaks down food molecules to release energy
location: mitochondria
2. Krebs Cycle/ Citric Acid Cycle
Uses: carbon from pyruvic acid (from glycolysis) is broken down
Makes: CO2 (waste product, released when you exhale), NADH, FADH2
Bioenergetics: Photosynthesis and Cellular Respiration
Need-to-Know/SG-Academic Biology
3. Electron Transport
Uses: NADH and FADH2 (from the Krebs Cycle)- passed from one carrier protein to the next,
uses the high energy electrons
Makes: converts ADP  ATP, H20
*Aerobic Cellular Respiration
PRODUCES 36 TOTAL ATP molecules from each glucose molecule (37% efficient)
Fermentation
-occurs when oxygen is NOT present
-anaerobic respiration that occurs in the absence of oxygen
-cells perform glycolysis followed by fermentation
(this means Krebs cycle and electron transport DO NOT occur)
Uses: 1 glucose molecule
Produces: NAD+ so that glycolysis can continue to make small amounts of ATP
2 main types:
1. Alcoholic Fermentation
2. Lactic Acid Fermentation
1. Alcoholic Fermentation
Pyruvic Acid + NADH  ethyl alcohol + CO2 + NAD+
-used by yeast (facultative anaerobes- will use aerobic respiration when oxygen is present, but if
not they will use fermentation)
-ethyl alcohol and CO2 are “waste” products
-CO2 production causes bread dough to rise, bubbles in beer, etc.
2. Lactic Acid Fermentation
Pyruvic Acid + NADH  lactic acid + NAD+
-happens in many cells during rapid exercise
- muscles don’t get enough oxygen to produce all the ATP they need through the Krebs Cycle and
electron transport, so they use lactic acid fermentation to get ATP made
-lactic acid buildup causes the painful, burning sensation in muscles after intense activity
- bacteria use this process to make foods like sour cream, yogurt, buttermilk, and sauerkraut