chapter 9: cellular respiration. chemical energy and food a calorie is the energy required to raise...
TRANSCRIPT
Chapter 9: Cellular Respiration
Chemical Energy and Food
A calorie is the energy required to raise 1g of water 1˚C– 1g of glucose releases 3811
calories 1 Calorie (capital “C”) on
food labels is actually a kilocalorie (1000 calories)– 1g of glucose releases
3.811 Calories
Using Chemical Energy
Plants and animals both use glucose for metabolic fuel
Glucose is not directly usable– Must be converted into ATP
first
Cellular Respiration Overview
Converts glucose into ATP Occurs in both plants and
animals Cellular Respiration
Reaction:– C6H12O6 + 6O2 → 6CO2 + 6H2O
Opposite of photosynthesis- 6CO2 + 6H2O → C6H12O6 + 6O2
Glycolysis
Series of reactions which break a 6-carbon glucose molecule into two 3-carbon molecules called pyruvic acid (a.k.a. pyruvate)
Occurs in the cytoplasm
Glucose
to electron transport chain
2 Pyruvate2 G3P
Glycolysis
Process is ancient – all organisms from simple bacteria to humans perform
it the same way Yields 2 ATP and 2 NADH per glucose molecule
Glucose
to electron transport chain
2 Pyruvate2 G3P
Glycolysis
Overview: Glucose is converted
into 2 pyruvic acid molecules– A.K.A. pyruvate
Pyruvic acid is a reactant in the Krebs Cycle
Glycolysis
Step 1: The cell invests 2 ATP
to convert glucose 2 G3P
Glycolysis
Step 2: 4 ATP molecules are
produced from the conversion of 2 G3P 2 pyruvic acid
2 NADH molecules are produced– Used in E.T.C.
Aerobic Cellular Respiration
Oxygen required = aerobic 2 more sets of reactions which occur in a
specialized organelles called mitochondria1. The Krebs Cycle
2. The Electron Transport Chain
The Krebs Cycle
AKA The Citric Acid Cycle Completes the breakdown of glucose
– Carbon and oxygen atoms end up in CO2 and H2O, respectively
Produces only 2 more ATP – but produces electron carriers NADH and FADH2
which move to the 3rd stage (The Electron Transport Chain)
The Krebs Cycle
Citric Acid Production
The Krebs Cycle
Products (per glucose): 6 CO2
2 ATP 8 NADH 2 FADH2
to E.T.C.
Electron Transport Chain
Powered by electron carriers from the Kreb’s Cycle
Produces a total of 32 ATP Water is formed when oxygen combines with
protons
The Electron Transport Chain
Electron Transport
Hydrogen Ion Movement
ATP Production
ATP synthase
H+ Diffusion
Intermembrane
Space
Inner Membrane
Mitochondrial Matrix
H+ Active Transport
Energy Tally
36 ATP for aerobic vs. 2 ATP for anaerobic
– Glycolysis 2 ATP
– Krebs 2 ATP
– Electron Transport Chain 32 ATP 36 ATP
Anaerobic organisms can’t be too energetic but are important for global recycling of carbon
Anaerobic Cellular Respiration
Also called fermentation Some organisms thrive in environments with little or no
oxygen– Marshes, bogs, digestive tracts, sewage treatment tanks, etc.
No oxygen used = anaerobic Results in no more ATP
– The final steps in these pathways serve ONLY to regenerate NAD+ so it can keep glycolysis running
End products such as ethanol and CO2 (yeast in beer/bread) or lactic acid (muscle cells)
Fermentation Overview
Alcoholic Fermentation
Used by yeasts and other microorganisms Produces carbon dioxide and ethanol Used to make bread and alcoholic drinks (beer, wine,
etc.)
Lactic Acid Fermentation
Used by both unicellular and multicellular organisms Lactic acid buildup in muscles causes a burning sensation Used in the production of sour cream, cheese, yogurt, and
many other foods & beverages
Glucose Pyruvic Acid Lactic Acid
Fermentation Overview