1. Cellular Energy

2. All cells require energy to function
Methods of cellular energy:
Photosynthesis
Cellular respiration

3. Obtaining Energy
Organisms can be classified according to how they get energy
Autotrophs: organisms that use energy from sunlight or from chemical bonds in inorganic substances to make organic compounds
Heterotrophs: animals or other organisms that must get energy from food instead of directly from sunlight or inorganic substances

4. Photosynthesis
Most autotrophs use the process of photosynthesis for energy
Photosynthesis: process of converting light energy from the sun into chemical energy to form organic compounds, primarily carbohydrates
Photosynthesis can be divided into two stages:
Capturing light/Light reactions
Calvin cycle

5. Step 1: Capturing light
Plants capture the light energy from the sun
Chlorophyll absorbs the light energy
Pigment is good at absorbing a certain wavelength of light
Located in chloroplasts
Light energy captured by the chlorophyll is needed to turn energy into food

6. Plants use the captured light to produce “food”
Step 2: The Calvin Cycle
Calvin cycle: a series of enzyme-assisted chemical reactions that produces a three- carbon sugar
Plants use the captured light to produce “food”
Water (H2O) and carbon dioxide (CO2) are needed to make the food
Roots absorb water from the soil
Carbon dioxide enters the plant through stomata
Stomata: small openings on the underside of leaves
Light energy changes the water & carbon dioxide into oxygen (O2)
Stomata: small “pores” found in plants; stomata from the Greek stoma, meaning “mouth”

7. Photosynthesis Process

8. Chemical Formula for Photosynthesis

9. Importance of Photosynthesis
Releases oxygen into the atmosphere
Dead plant matter is a source of fossil fuel
All organisms use energy from the sun– direct or indirect– captured during photosynthesis
Factors that Affect Photosynthesis
Light intensity
Carbon dioxide levels
Temperature

10. Energy is stored in organic molecules!
Cellular Respiration
Energy is stored in organic molecules!
Cellular respiration: a complex process in which cells make adenosine triphosphate (ATP) by breaking down organic compounds
ATP = universal energy storage molecule
All organisms break down ATP for energy
Energy is released when the chemical bonds in ATP are broken
Both autotrophs & heterotrophs undergo cellular respiration
Can be divided into two stages:
Glycolysis
Aerobic Respiration

11. Step 1: Glycolysis
Glycolysis: the breakdown of glucose by enzymes, releasing energy and pyruvic acid
Occurs in the cytoplasm
Oxygen is not needed
Small amount of ATP released

12. Step 2: Aerobic Respiration Two major stages:
The Krebs cycle
Electron transport chain
Small molecules are broken into even smaller molecules
Occurs in the mitochondria of eukaryotes
Oxygen is required
A lot of energy (ATP) is released
Occurs in cytosol of prokaryotes

13. Cellular Respiration Process
Cellular respiration is nearly 20 times more efficient than glycolysis alone

14. Cellular Respiration Chemical Formula
How does it compare to the chemical formula for photosynthesis?

15. What if oxygen is missing?
English lesson:
aerobic = involving or requiring air
a-, an- prefix means “without” or “not”
anaerobic = without air
What if oxygen is missing?
Cannot complete aerobic respiration
Anaerobic respiration aka fermentation
Alcohol fermentation
Yeast
Glucose  ATP + CO2 + alcohol
Make beer, wine, bread
Lactic acid fermentation
Bacteria, animals
Glucose  ATP + lactic acid
Bacteria make yogurt
Animals feel muscle fatigue
No oxygen or no mitochondria (bacteria)
Can only make very little ATP
Large animals cannot survive
Lactic acid buildup in muscles = makes cells’ cytosol more acidic  reduced capacity for cell to contract, causing cramps

16. Turns energy into sugars Turns sugars into energy
Photosynthesis
Respiration
Turns energy into sugars
Turns sugars into energy
Summary:
Glucose is made during photosynthesis
Glucose is broken down and energy is released during respiration
All organisms use energy released to do everything