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Glycolysis
Life needs energy to survive and function
efficiently.
Cells need to harvest energy
• Energy needed to grow and function
• Unicellular organisms
• Ex. Yeast, bacteria
• Multicellular organisms
• Human body has 3 trillion cells
Chemical Energy: ATP
• “Energy currency”
• Adenine, ribose, and 3
phosphate groups
• Transfers energy from one
source to another
• 3rd phosphate group acts as
energy
• ATP
• “active”: can donate extra
phosphate group
• ADP
• 2 phosphate groups
• “non-active”: must go try to
recruit a phosphate group
Metabolism
• All chemical activities in a cell or organism
• Two types
• Synthesis
− Building large, more complex molecules
− “uses” free energy
• Decomposition
− “breaking down” rxn to smaller, simpler things
− “releases” free and heat energy
Cell Respiration
• A type of decomposition Reaction
• A pathway
• Made up of several steps
• Generate energy by breaking down
molecules
• Sugar first choice
• Also breaks down starch, fats, proteins
Sources of energy
• Carbohydrates
• Simple Sugars
• Broken down very fast
• Ex. Sucrose, glucose, fructose
• Starches
• Sugar units strung together
• Broken down into glucose first for
energy
• Protein
• Lipids
Glucose
Steps of Cellular Respiration
• Pathway made up of 3 major steps
• 1. Glycolysis
• 2. Kreb’s Cycle
• 3. Electron transport system
First stage in
Respiration:Glycolysis
• Happens in cell
cytoplasm
• a.k.a. “cytosol”
• Fluid filling cell
• Breaks down glucose
into pyruvate http://www.ebi.ac.uk/microarray/biology_intro_files/cell.jpe
Starting Material: Glucose
• Common raw material
• C6H12O6
• Complex sugars get broken down
by enzymes to make glucose
C
C
C
C
C
C
Step 1: Adding phosphates
• Enzyme converts glucose to glucose-6phosphate
• 2 ATP needed for this step
• 1 ATP gives energy
• 1 ATP donates a phosphate group
P
C
C
C
C
C
C
P
Step 2: Breaks in Half
• Glucose-6-biphosphate
• unstable
• breaks down into two 3-carbon sugarphosphates
P
C
C
C
C
C
C
P
Step 3:Form Pyruvate
• Enzymes rearrange and oxidize(remove
electrons) to form 2 pyruvate
• A.k.a “pyruvic acid”
• Electrons add to NAD+ to make 2 NADH
• 4 ATP are produced(overview)
C
C
pyruvate
C
C
C
pyruvate
C
Next step depends on O2
• After glycolysis, next step depends on
oxygen
• Growing Yams in Australia
• Oxygen= normal aerobic respiration
• Creates more energy(ATP)
• No oxgyen=anaerobic respiration
Anaerobic respiration
• NO OXYGEN!!!!
• Produces less energy
• Starts with glycolysis
• Glucose breaks down into 2 pyruvate
• Does not continue on til Kreb’s cycle
• A.k.a “fermentation”
• Lactic acid fermentation
• Ethanol fermentation
PYRUVATE
Ethanol
Lactate
Carbon
dioxide
http://biology.clc.uc.edu/courses/bio104/cellresp.htm
Anaerobic:Lactic acid
fermentation
• Animal cells and some bacteria will reverse the
rxn that produced pyruvate
• NADH and pyruvate become NAD+ and
lactate(3-carbon acid)
• Yogurt: sour taste
• Sore muscles
http://www.lekkerplantaardig.net/images/f-yogurt.jpg
:Anaerobic: Ethanol
Fermentation
• Done by yeast and some bacteria
• “waste” products
• Ethanol
• Carbon dioxide
• Alcohol
• Bread
Bread: Ethanol
Fermentation
• Add baker’s yeast
• Yeast perform anaerobic fermentation
• Produce carbon dioxide and ethanol
• Carbon dioxide gets trapped in
gluten(protein in wheat)
• Air bubbles in bread
• Ethanol evaporates during baking
• Gives it that wonderful smell when baking
Aerobic Respiration
• There is oxygen!!!
• Pyruvate is transported to second step of
respiration:
The Kreb’s Cycle
Making Homemade Ginger Ale
• Ethanol fermentation
• Produces carbon dioxide and a unalcoholic
form of ethanol
• Organism: yeast
• Dry baker’s yeast
• Used by bakers for making dough
• Add water to revive yeast
• Feed it sugar
• Add 1 cup of sugar
• Add ¼ cup of dry
yeast
• Mix by shaking
• Add 2 tbspoons of
ginger to a cup
• Juice a whole lemon
• Stir lemon and ginger
together
• Add slurry of lemon and
ginger to bottle
• Rinse cup with water and
add to bottle
• Cap bottle and shake
• Fill bottle with clean, cool
water
• Leave only an inch of air at
the top
• Cap bottle and invert to
dissolve sugar.