Transcript Energy

Cellular
Energy
Photosynthesis
and
Respiration
Chapter 8
Section 1: How Organisms Obtain Energy
Section 2: Photosynthesis
Section 3: Cellular Respiration (not breathing!)
Sect 1: Obtaining Energy
All energy for life comes from the
sun.
Autotrophs
Heterotrophs
You “lose” energy
at each trophic
level.
Energy = the ability to do work
1st Law = Law of Conservation of
Energy
Energy cannot be created or destroyed,
only change form.
2nd Law = Energy cannot be changed
without the loss of usable energy.
(think food chain or energy pyramid)
Metabolism =
• Means the sum of all chemical
changes in a cell or the body of an
organism.
• It has two subdivisions:
1. Anabolic
2. Catabolic
Anabolic pathway: uses energy to
build molecules
Ex: photosynthesis
Light energy
chemical energy
mechanical energy.
This happens in the chloroplasts!
Catabolic Pathways release energy by
breaking down larger molecules into smaller
molecules
Ex: Cellular Respiration
Organic molecules are broken down to
release energy for use by the cell.
This happens in the mitochondria!
How are these related?
PHOTOSYNTHESIS EQUATION:
6CO2 + 6H2O
C6H12O6 + 6O2
CELLULAR RESPIRATION EQUATION:
C6H12O6 + 6O2
6CO2 + 6H2O + ATP
ATP
The Unit of Cellular Energy
ATP: adenosine triphosphate
• Provides chemical energy
• Found in all types of organisms
• Releases energy when the bond
with the 3rd phosphate is broken.
ATP
Notice the 3 high energy phosphate bonds!
Energy is released when 3rd phosphate bond is broken!
Section 2
Photosynthesis
(Anabolic Pathway)
Photosynthesis
Occurs in 2 phases:
Phase 1: Light Reactions
• Occurs in thylakoids
• Pigments absorb light (chlorophyll)
• Water is split, O2 released
• Energy stored temporarily in ATP and NADPH
Light reaction in the thylakoids.
Phase 2: Light-Independent Reactions
(Dark Reactions, The Calvin Cycle)
• Occurs in stroma
• Energy in ATP and NADPH is used to
produce glucose.
• CO2 is used.
• Glucose is better for long term energy
storage.
MEMORIZE ME!!!!
How do water, nutrients and CO2 enter the cell?
In the leaves, CO2, water and O2
move through the stomata (guard cells).
Plants have a vascular system!
Water and nutrients move up through the xylem.
Sugars and other molecules move throughout the
plant through the phloem.
Xylem and phloem in celery.
Section 3: Cellular Respiration
• This is a catabolic pathway.
• Organisms obtain energy by
breaking down organic molecules.
Purpose of Cellular Respiration
To harvest electrons from carbon
compounds (ex: glucose), and use that
energy to make ATP.
ATP is used to provide energy for cells to
do work.
Cellular Respiration
• Takes place in the cytoplasm and
mitochondria
• Releases the energy stored in glucose
to form ATP
• A total of 36 ATP can be made from
one molecule of GLUCOSE.
1 molecule glucose = 36 ATP
Cellular Respiration occurs in 2 stages.
Stage 1
(cytoplasm)
Stage 2
(depends on the
presence of oxygen)
STAGE 1
• Glycolysis – occurs without oxygen,
anaerobic, in the cytoplasm
• Uses 2 ATP, forms 4 ATP (net of 2 ATP)
• Forms pyruvate
– stores majority of energy
STAGE 2
Pyruvate is broken down:
2 options:
1. Aerobic option (with O2)
Occurs in the mitochondria in the
presence of oxygen and produces 34 ATP.
Anaerobic option (no O2)
Occurs in the cytoplasm.
Net gain of 2 ATP
In humans:
A. Lactic acid fermentation
Occurs in skeletal muscles when no
oxygen is available. (painful!)
In yeast (fungi) and bacteria:
B. Alcohol fermentation
(produces CO2 and ethanol)
Occurs in yeast and bacteria to make
bread, beer, wine, ethanol
Recap of cellular respiration stage 2 options:
PHOTOSYNTHESIS EQUATION:
6CO2 + 6H2O
C6H12O6 + 6O2
CELLULAR RESPIRATION EQUATION:
C6H12O6 + 6O2
6CO2 + 6H2O + ATP
Think about it!
Plants perform photosynthesis
and cellular respiration.
Animals perform cellular
respiration only!