1. NOTE SHEET 9 – Cell Energy

2. Why do cells need energy?

3. In what ways are our cells like a tower?
Are they organized? Do they have structure?
There are forces in the environment that disrupt the cell’s structure
Disorder (entropy) is always on the increase

4. How can cells maintain their highly ordered structure?
It takes energy, work, and information to maintain order
Cells need energy just to stay the way they are and not break down

5. What do cells use energy for?
Repair themselves
Growth
Reproduction
Movement
Active transport
Protein synthesis

6. Chemistry Review
Molecule – two or more atoms held together by covalent bonds
EX. H2O, CO2, C6H12O6
Covalent bond – atoms are held together by shared electrons
Forming covalent bonds between atoms stores energy (endergonic)
Breaking covalent bonds between atoms releases energy (exergonic)

7. What do eukaryotic cells use for energy?
Glucose - a type of sugar used by cells for energy
Like all sugars, glucose is a carbohydrate
The chemical formula of glucose is C6H12O6

8. Where does glucose come from?
Photosynthesis – the process where plants make glucose
Photosynthesis takes place in the chloroplasts of plant cells
Photosynthesis requires 3 ingredients: light energy, water (H2O), and carbon dioxide (CO2)

9. Why are plants green? Visible light is made up of many colors (ROYGBIV)
When light shines on an object, you see whatever colors are reflected

10. Why are plants green?
Chlorophyll – a green pigment found in the chloroplasts of plant cells
A pigment is a chemical that absorbs certain colors of light, while reflecting other colors - the color you see is what is being reflected
Chlorophyll absorbs most colors of light EXCEPT green, which is reflected

11. Green light is reflected by the chlorophyll in the chloroplast

12. Plant cells have lots of chloroplasts…
…so you see green when you look at plants

13. Chlorophyll Absorption Spectrum

14. Photosynthesis in a chloroplast

15. How does photosynthesis work?
Light energy is absorbed by chlorophyll
The plant takes in H2O and CO2
The H in the H2O, the C and O from the CO2 is rearranged to make a glucose molecule (C6H12O6)
The energy from the light is used to bond the C,H, and O together storing the energy for later use
Leftover oxygen is released into the air

16. What is the chemical equation for photosynthesis?
6 H2O + 6 CO2 + light energy  C6H12O6 + 6 O2

17. At the end of photosynthesis, the energy from the sun that the plant absorbed is now stored in a molecule of glucose The glucose is a form of food that cells can use when they need energy

18. Where do eukaryotic cells get glucose?
Plant cells make glucose during photosynthesis
Animal cells get glucose whenever animals eat foods that have carbohydrates

19. What do eukaryotic cells do with glucose?
Before cells can use the energy in glucose, the energy must be removed and broken up into smaller units
Respiration – the process where cells break down glucose in order to release energy
The released energy is stored in small molecules called ATP
Respiration takes place in the mitochondria of eukaryotic cells
Respiration requires 2 ingredients: glucose (C6H12O6) and oxygen (O2)

20. Respiration takes place in the mitochondria of plant and animal cells

21. Respiration releases energy from glucose and stores it in smaller molecules called ATP

22. Respiration in mitochondria

23. How does respiration work?
C6H12O6 and O2 are taken into cells by cell transport and enter the mitochondria
The C6H12O6 is broken down into CO2 and H2O
The released energy is stored in ATP molecules that the cell can use for anything that requires energy
The CO2 and H2O exit the cells and are released back into the air

24. What is the chemical equation for respiration?
C6H12O6 + 6 O2  36 ATP (energy) + 6 H2O + 6 CO2

25. Respiration releases the energy that was stored in the glucose during photosynthesis so the cell can use it

26. What is the relationship between photosynthesis and respiration?

27. What is the relationship between photosynthesis and respiration?

28. What is the relationship between photosynthesis and respiration?
Photosynthesis and respiration are opposite processes – photosynthesis stores energy, respiration releases energy
The products of photosynthesis are the ingredients needed for respiration

29. Eukaryotic cells use glucose for energy Photosynthesis makes glucose (energy is stored) Respiration breaks glucose down (energy is released)