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-6-phosphate

• 2 ATP needed for this step• 1 ATP gives energy• 1 ATP donates a phosphate group

C C C C C CP P

Step 2: Breaks in Half

• Glucose-6-biphosphate• unstable

• breaks down into two 3-carbon sugar-phosphates

C C C PC C CP

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 CC C Cpyruvate pyruvate

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

Lactate

Ethanol

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.