1. Converting Food into Energy!
Cellular Respiration
Converting Food into Energy!
Review photosynthesis
What is the photosynthesis equation? 6 H2O + 6 CO2  C6H12O6 + 6 O2
What does photosynthesis occur (what organelle)? chloroplast
What are the two phases of photosynthesis? Light dependent and light independent/Calvin
Where does each happen? Light dependent (thylakoid) and light independent (stroma)
What happens in each stage? Light dependent (energy captured from sun and stored in ATP and NADPH; water broken into hydrogen and oxygen); light independent (sugar made using stored energy from light dependent stage, hyrodgen from water molecules, and carbon dioxide from air)
Draw chloroplast and label parts (thylakoid, grana, stroma)
Why is photosynthesis important? Oxygen (waste for plants but good for us) and glucose (food source)
We can’t use light for energy, but we can use the chemical energy that is stored in organic compounds
This is all about the release of stored energy

2. Cellular Respiration Process of breaking down food to produce energy
Equation:
C6H12O6 + 6 O2  6 CO2 + 6 H2O + ATP (energy)
Cellular respiration = process of breaking down food to produce energy
Notice that the equation is very similar to photosynthesis, just the reverse
we start with glucose, which is what our body breaks carbohydrates into when we eat them
we add some oxygen and we end up with energy in the form of ATP (along with some carbon dioxide which we breathe out and water)
What I expect you to know about cellular respiration:
- what we start with / end with
- what is made along the way
- what the two options are (because there are two different pathways that can be taken depending on how much oxygen is present)

3. Respiration Video
Photosynthesis and cellular respiration both convert energy to different forms within cells
- photosynthesis: light energy  chemical energy
- cellular respiration: chemical energy  different form of chemical energy that can be used by cells
Cellular respiration occurs in every cell
- not the same as breathing
Cellular respiration occurs in producers (autotrophs) and consumers (heterotrophs) b/c occurs in all cells

4. 2 Types of Respiration
Aerobic Respiration: uses Oxygen to break down food to produce energy
Anaerobic Respiration (“Fermentation”): does NOT use Oxygen to break down food to produce energy
There are two types of cellular respiration, depending on whether there is oxygen present
Aerobic respiration – most efficient (meaning you get the most energy out of this way)
Anaerobic respiration – less efficient, but still allows organism to get energy from the glucose
this is also known as fermentation

5. Comparison of Pathways
Respiration Pathways
Comparison of Pathways
To efficiently get energy out, need to use a lot of little steps (if we just broke the big glucose molecule apart at once, it would release so much heat that we would burn up)
This is the basic overview of cellular respiration
Log in to textbook
select the textbook
select Ch. 5 (and press Go)
select visual concepts tab
click on Comparing aerobic and anaerobic respiration
Stage 1 of cellular respiration:
breaking glucose (6 carbon molecule) into 2 molecules of pyruvate (3 carbon molecule)
cell invests a little bit of energy to break the glucose apart, but gets more out
still not a lot of energy has been released
this step does NOT require oxygen
Stage 2: 2 pathways dependent on presence/absence of oxygen

6. 2 Steps of AEROBIC Respiration
1) Glycolysis: Glucose (6-C sugar) is split into Pyruvate (3-C molecule) 2 ATP(net) & NADH produced
Occurs in cytoplasm
2) Oxidative Respiration: (Krebs Cycle and Electron Transport chain)
Oxygen + Pyruvate + NADH produce 34 ATP, CO2, and H2O
Occurs in mitochondria
Let’s start with aerobic respiration (occurs when oxygen is present)
Stage 1: glycolysis (glyco = sugar and lysis = breaking so it is breaking down of sugar)
let’s say you eat a candy bar or a baked potatoe  body breaks it down to glucose in digestion
glucose is taken into the cells of your body and into the cytoplasm (where glycolysis occurs)
remember: this stage is the same with both aerobic and anaerobic respiration
6 carbon glucose is split into two 3 carbon pyruvate molecules
energy produced: 2 ATP and NADH (cousin of NADPH – one with P is in photosynthesis)
Review: what is happening? Whay is product of glycolysis? Where is it happening?
Oxidative Respiration: happens in the mitochondria (cells that need a lot of energy, like muscle cells, will have a lot of mitochondria)
here we add oxygen to the pyruvate and the NADH produced in glycolysis and the end result is 34 ATP (lot of energy) and carbon dioxide and water
where does the oxygen come from (from air – we breathe it in)

7. Glycolysis: 6 carbon glucose is broken down into two 3 carbon pyruvate molecules (net of 2 ATP and some NADH)
Oxidative respiration: involves both the Krebs cycle and an electron transport chain
pyruvate (3 carbon) enters the mitochondria and becomes a 2 carbon molecule (acetyl-CoA) releasing carbon dioxide
goes through the Kreb’s cycle (releasing more carbon dioxide) and electron transport chain (releasing water that is formed from oxygen) to produce a net of 34 ATP
Use large construction paper items to illustrate on board

8. 2 Steps of ANAEROBIC Respiration
1) Glycolysis: Glucose is split into Pyruvate 2 ATP produced & NADH
2) Fermentation: Pyruvate combines with an energy carrier (NADH) to produce ethanol and CO2 or lactic acid
Alcoholic fermentation: ethanol + CO (bread, wine, beer)
Lactic Acid fermentation: lactic acid (sore muscles)
When there isn’t enough oxygen, what happens?
Stage 1 is the same (glycolysis) – the aerobic/anaerobic pathway is determined by the presence or absence of oxygen after glycolysis is complete
If after glycolysis there is no oxygen present, then Stage 2 is fermentation
there are 2 types of fermentation – one you experience physically and the other you experience at breakfast
Ask if anyone ever made bread – what did you do? what went into it?
yeast are single-cell fungus: they take the sugar in the bread dough and start to break it down; run out of oxygen in the dough, so they start to undergo alcoholic fermentation; this releases ethanol (alcohol – gives bread dough a distinctive smell) and carbon dioxide (gas that causes the bread ball to rise or get bigger); when you bake the bread the alcohol evaporates away
Wine and beer are produced the same way (if CO2 stays in, you have carbonated wine or champagne)
Lactic acid fermentation occurs in muscle cells and bacteria
when you are working hard (eg., sprinting) and the muscle cells can’t get enough oxygen to the cells fast enough for their needs, they start producing lactic acid from the pyruvate; the acid builds up and it causes pain in the muscles; how get rid of it – stretch, drink lots water, breathing
yogurt is another example – bacteria in yogurt are alive; they break down the sugar in milk and make lactic acid which produces the tart taste that yogurt has
Summarize: which type of fermentation produces gas? Alcoholic fermenation (CO2)

9. Respiration Pathways- another look!

10. Respiration Video
Energy is released whenever bonds are broken (so when I break the bonds that form the glucose molecule what is released?)
Protein, fat and carbs can all be used to release energy (by our bodies)
fat and carbs are used most often
fat stores more energy, but takes longer to break down
carbs store less energy, but can be broken down much quicker
Diet recommended for athletes: high carb diet
Why? 1. breaks down easier and 2. working muscles rely on carbs

11. Compare to Photosynthesis
Cellular Respiration
Compare to Photosynthesis
What are the similarities?
What are the differences?
Similarities:
1. Both are part of the energy cycle (how energy flows through living systems)
2. Both involve many of the same compounds (glucose, carbon dioxide, oxygen, water, ATP)
Differences:
1. cellular respiration occurs in all cells; photosynthesis occurs in plants
2. cellular respiration produces energy from food; photosynthesis produces food using energy (each process uses the products of the other process)
3. cellular respiration gives off CO2 and uses oxygen; photosynthesis gives off oxygen and uses CO2 (really part of #2)

12. References Holt, Rinehart,Winston. (2007) Biology (CA Ed.).
Simply Science: Energy Converters. Distribution Access Discovery Education. 7 November 2009 <