Photosynthesis and
Cellular Respiration
Two ways to get food

“troph” = food

Autotrophs
–
–

Auto = self
Autotrophs make their own food
Heterotrophs
–
–
Hetero = different
Heterotrophs get their food from something else (they
have to eat it)
Two ways to get food

Autotrophs
–

Plants
Heterotrophs
–
Animals
Photosynthesis
Photosynthesis


Converts the sun’s energy
into chemical energy stored in
sugar
Takes place in specialized
structures inside plant cells
called chloroplasts
–
Chlorophyll is the pigment that
absorbs sunlight.
Photosynthesis Reaction

6CO2 + 6 H2O + light
energy → C6H12O6 + 6O2

The food plants make is called glucose (sugar)
Photosynthesis

2 different
reactions
–
Light Reactions

–
Capture light energy
for photosynthesis
Calvin Cycle

Produces glucose
sugar
Cellular Respiration
Cells
Breathing
Cellular Respiration

Happens in both plant and animal cells

Overall Reaction:
–
C6H12O6 + 6O2 → 6CO2 + 6H2O
Cellular Respiration Overview

Depends on whether or not there is oxygen

Aero = oxygen
Aerobic Respiration – makes energy
Anaerobic Respiration – Fermentation (makes
alcohol)


Step 1: Glycolysis

The energy that cells make and use is called
ATP
–


Adenosine triphosphate
Glycolysis makes 2 molecules of ATP (energy)
Glycolysis happens in the cytoplasm of the cell
Step 2: Check for Oxygen


If oxygen is present, the cell can make more ATP
If no oxygen is present, the cell has to recycle
the pieces from glycolysis and makes alcohol.
Step 3 with oxygen:
Cellular Respiration


Oxygen required=aerobic
2 more sets of reactions which occur the cell’s
mitochondria
–
1. Kreb’s Cycle – makes 2 ATP

–
Also called the Citric Acid Cycle
2. Electron Transport Chain – makes 32-34 ATP
Kreb’s Cycle (Citric Acid Cycle)
Step 3 without oxygen:
Fermentation



The cell must recycle the materials from
glycolysis.
This recycling process is called fermentation.
The product of fermentation is alcohol.
Energy Tally


36 ATP for aerobic vs. 2 ATP for anaerobic
–
Glycolysis
2 ATP
–
Kreb’s
2 ATP
–
Electron Transport
32 ATP
36 ATP
Anaerobic organisms can’t be too energetic but
are important for global recycling of carbon