1. The Working Cell: Energy from Food
Chapter 7
The Working Cell:
Energy from Food

2. Do Now What do plants need to make sugar?
What do animals get from plants?

3. Why is the sun important to life?
7.1 Sunlight Powers Life
Why is the sun important to life?
Food
Water Cycle
Climate

4. Autotrophs autotroph: organism that makes its own food: “self-feeder”
Inorganic materials --> organic materials
photosynthesis: uses the sun’s energy to convert to food
Light(energy) + water + CO2 --> sugar + O2
producers: produce organic molecules that serve as food for other organisms in the ecosystem

5. Heterotrophs
heterotrophs: organisms that can’t make food; “other eaters”
consumers: must obtain food by eating producers or other consumers
depend on producers for energy and materials for life and growth

6. Cellular Respiration
cellular respiration: chemical process that uses oxygen to convert the chemical energy stored in organic molecules into another form (ATP)
food into energy
C6H12O6 + O2 --> H2O + CO2 + energy

8. Do Now Take out your homework (7.1 & 7.2 CC) HW: 7.3 CC
What is the equation for cellular respiration?

9. 7.2 Food Stores Chemical Energy
energy: the ability to perform work
kinetic energy: the energy of motion
potential energy: energy stored due to an object’s position or arrangement
gain potential energy the higher you go against gravity
thermal energy: random molecular movement which causes collisions and heat
energy used is provided by food

10. Chemical Energy Chemical energy
the potential to perform work is due to the arrangement of atoms within the molecules
depends on the structure of the molecules
(carbs, fats, and proteins are rich in chemical energy)
sugar (high potential)  carbon dioxide + water (kinetic energy)

11. Cellular Respiration is like a Car Engine
high chemical energy = glucose and oxygen (gasoline and oxygen)
“exhaust” = carbon dioxide and water
40% from food to work
60% thermal energy as heat = 100W light bulb
calorie: amount of energy required to raise the temperature of 1g water by 1 degree Celsius
1000 calories = 1 kcal =
C (on food labels)

12. Do Now Take out your homework
4 people at a time take the survey on the computers in the back

13. 7.3 ATP ATP: adenosine triphosphate
Adenosine = adenine + ribose
Triphosphate = 3 phosphates
One phosphate is lost in a chemical reaction
ATP --> ADP
The molecule that accepts the phosphate undergoes a change (for work)

14. Work chemical work: building large molecules
Ex. Proteins
ATP energy for dehydration synthesis links AA
mechanical work: contraction of muscle
ATP transfers P to proteins --> change shape --> muscle cells contract
transport work: pumping solutes (ions) across a cellular membrane
P --> change shape

15. ATP Cycle ATP is continuously converted to ADP
Muscle cell recycles all ATP once a minute
10 million spent and regenerated per second

17. Do Now What is the overall purpose of cellular respiration? Homework:
Work on video critique lyrics
Questions 1-12 on CR worksheet

18. Food to Oxygen Relationship of Cellular Respiration to Breathing
aerobic: process that requires oxygen
ETC
Anaerobic: does not require oxygen
Glycolysis
fermentation

19. In Cellular Respiration…
Oxygen attracts electrons very strongly
“electron grubber”
Carbon and hydrogen exert much less pull
Several carbon-hydrogen bonds in sugar
Carbon and hydrogen change partners and bond with oxygen
Electrons in these bonds “fall” toward oxygen and release energy
Ex. Burning sugar

20. 7.5 CR Converts Energy Mitochondria
Envelope of 2 membranes; inner and outer with space
Inner membrane encloses thick fluid (matrix)
Enzymes and other molecules built into inner membrane
Complex folding allows many sites of reactions to maximize ATP production

21. Metabolism metabolism: a cell’s chemical processes Metabolic Pathway
Series of reactions
Specific enzymes catalyzes each reaction
3 Stages of CR
Glycolysis, Kreb cycle, ETC and ATP synthase

22. Stage 1: Glycolysis “splitting of sugar”
Outside the mitochondria in the cytoplasm
2 ATP molecules split a 6-carbon glucose in half and adds a phosphate to each
C-C-C-P
Each 3-C molecule transfers electrons and H+ to a carrier molecule NAD+
NAD+ accepts 2 electrons and one H = NADH
“payback” = 4 new ATP molecules produced
Result is 2 pyruvic acid molecules

23. Cycle
Input
Output
ATP
Glycolysis
Glucose
Pyruvic acid 2
Krebs
Acetyl CoA
(from pyruvate)
CO2
ETC
Electrons, O2
H2O 34
Overall
C6H12O6 + O2
CO2 + H2O
+38

24. Stage 2: Krebs Cycle (Hans Krebs)
Finishes breakdown of pyruvic acid molecules to CO2 which releases more ATP
Enzymes are dissolved in the fluid matrix
Pyruvic acid does not take part in the Krebs cycle
Diffuses into the mitochondrion and loses a molecule of CO2
Converted to a 2-C compound = acetyl CoA (Acetyl coenzyme A )

25. Krebs Cycle Steps Acetyl CoA molecules joins a 4-C acceptor molecule
Produce 2 more CO2 molecules and an ATP per acetyl CoA
NADH and FADH2 trap most of energy
The 4-C acceptor regenerates and cycle continues

26. Cycle
Input
Output
ATP
Glycolysis
Glucose
Pyruvic acid 2
Krebs
Acetyl CoA
CO2
ETC
Electrons, O2
H2O 34
Overall
C6H12O6 + O2
CO2 + H2O
+38

27. Stage 3: ETC and ATP Synthase
NADH transfers electrons from glucose to ETC
Each transfer in the chain releases energy which is used to pump H across the membrane
Less concentrated to more
Stores potential energy
ATP synthases: protein structures in mitochondria that act as miniature turbines
H+ rush back “downhill” through the ATP synthase
Energy used to convert ADP to ATP

28. Cycle
Input
Output
ATP
Glycolysis
Glucose
Pyruvic acid 2
Krebs
Acetyl CoA
CO2
ETC
Electrons, O2
H2O 34
Overall
C6H12O6 + O2
CO2 + H2O
+38

29. Summary of Cellular Respiration

30. 7.6 Fermentation
fermentation: process that can make ATP without oxygen (only 2 ATP)
anaerobic: environment without oxygen
Fermentation makes ATP entirely from glycolysis
Not enough oxygen being supplied
Produces waste product called lactic acid
Temporary build-up results in soreness & fatigue
Eventually converts back into pyruvic acid

31. Fermentation in Microorganisms and plants
Yeast is forced to ferment sugar
Produces alcohol and CO2, not lactic acid
Some fungi and bacteria produce lactic acid
Transform milk into cheese and yogurt
Oxygen allows most energy from food
Much more efficient
38 ATP (w/oxygen) vs. 2 ATP (w/out)