Chapter 6: Photosynthesis & Cellular Respirations Flashcards
Photosynthesis turns light energy into
Chemical energy occurs in autotrophs
Reactants
CO2, H2O, light (+pigment)
Products
Glucose O2
Photosynthesis occurs in
Chloroplast (found in green sections of plants)
Plants create solid tissue out of thin air, water, and a few elements
In the soil
The overview photosynthesis
Step 1: Capture light energy (thylakoid/chlorophyll), aka light-dependent reaction
Step 2: Make glucose using captured energy (stroma/Calvin cycle), aka light-independent reaction
Light travels in waves of different lengths at
Different energy levels
Visible light is
Just a fraction of the energy of light (the visible spectrum) involved in photosynthesis
Key ideas: Wavelengths can be
Absorbed or reflected
Photosynthetic pigments
Primary pigment = chlorophyll (green): Reflects greenish li.ght; absorbs other colors
Light capture
Chlorophyll uses light energy to bump up an electron to a higher energy state
Photons are
“Packets” of light energy
Light-dependent reaction
Clusters of chlorophyll pass energy captured from sunlight to a primary election acceptor in the reaction center
Light-independent reaction
Aka the Calvin Cycle - where sugar is made, using the NADPH and ATP from the light dependent reaction, and CO2 from the atmosphere
Evolution Tie-In
1) The quantity of light around the globe differs
2) Hot climate plants would lose too much water if their stomata were open all the time to allow CO2 absorption
3) Plants in these areas had to adapt and develop alternate methods of maintaining photosynthesis without dehydrating
Cellular respiration
Release chemical energy from food (acquired via photosynthesis, directly or indirectly)
In a nutshell:
1) Reactants: organic molecule + oxygen
2) Products: CO2+H2O+ATP
It occurs in three stages
1) Glycolysis
2) Krebs (Citric acid) cycle
3) Electron transport chain (oxidative phosphorylation)
Glycolysis
The splitting of glucose (sugar)
Glycolysis occurs in the
Cytosol
It breaks one molecule of glucose into
Two molecules of pyruvate
Glycolysis invest
Two ATP molecules
Glycolysis receive
Four ATP + Two NADH
Glycolysis net gain
Two ATP + Two NADH
Cellular respiration: Krebs
1) Complete the breakdown of pyruvate
2) Occurs in the mitochondria
Cellular respiration: Krebs key events
1) Acetyl-CoA Production
2) Krebs cycle
Acetyl-CoA: Compound that pyruvate is
Converted to upon entering mitochondrion
The enzyme-catalyzed reaction leads to
1) Release of the CO2 molecule
2) Acetate creation transform NAD+ to NADH
3) Coenzyme A (from a B vitamin) is added to acetate (forming acetyl-CoA), making it unstable
Krebs Cycle
8-steps process that adds the unstable acetyl-CoA to a recycled molecule (oxaloacetate) resulting in the production of CO2, NADH, FADH2, and ATP
More energy is released from the original glucose molecule, and CO2 is
Released
Electron transport chain
One glucose molecule = Four net ATP molecules, plus NADH and FADH2
Similar to photosynthesis, the electron transport chain lies on
The inner membrane of the mitochondria and is where ATP is synthesized
ATP synthesis occurs on the matrix membrane with
The protein ATP synthase
Only part of the membrane that is
H+ permeable (allow H+ in)
Using the concentration gradient from the ion pumps of the electron transport chain
ATP synthase uses the movement of the ions to add a phosphate group to ADP, creating ATP
Get ~34 ATP
Per glucose molecule
Cellular respiration overview of the process
Glucose, pyruvate, NADH+FADH2, membrane proteins + ATP synthase, and ATP
Cellular respiration using glycolysis, Krebs, and electron to
Transport chain
The math: 1 NADH creates 2-3 ATP
1 FADH2 creates ~ 2 ATP
Combination of all cellular respiration processes =
38 ATP from one glucose
Glycolysis revisited: Some organisms use glycolysis exclusively for
Energy, and the process of fermentation
Alcohol fermentation
Pyruvate is converted to ethanol (brewing/wine production)
Lactic acid fermentation
Pyruvate reduced to lactate (dairy products, anaerobic exercise)
Fermentation
Anaerobic, electron acceptor: organic molecule, net 2 ATP molecules, and location: cytosol
Respiration
Aerobic, electron acceptor: oxygen, net 38 ATP molecules, and location: cytosol and mitochondria
Cellular respiration can run on
Fats, carbs, or proteins
Cellular respiration typically occurs by breaking them into
Simple sources of carbon
Fatty acids can be modified to
Acetyl-CoA
Take-away lesson: food can enter
The process at any point, it doesn’t have to go through every step
