Transcript Cell Energetics

What is energy?
 The
capacity to do
work
 Work
Kinetic Energy
 The
energy of moving objects
A
capacity to do work that results from
the location or position of an object
First Law of Thermodynamics
 Energy
can never
be created or
destroyed.
Second Law of
Thermodynamics
 Every
conversion
of energy
includes the
transformation
of some energy
into heat.
Energy Conversions
 Only
~1% of the energy released by the sun
that earth receives is captured and converted
by plants.
• Converted into chemical bond energy
ATP
Recycling in the Cell
ADP + phosphate group + energy = ATP
How do cells regulate the speed
of reactions?
• Enzymes
• protein catalysts
• speed up
reactions
• not consumed
• Require energy to
initiate breaking of
existing bonds &
begin reaction
(activation energy)
= energy barrier
Cellular Respiration
catabolism: breaking
down organic
molecules to
extract energy
Two Catabolic
Pathways
1) Fermentation
(anaerobic)
2) Cellular Respiration
(aerobic)
Cellular Respiration




Requires fuel and oxygen
Potential energy stored in
chemical bonds of sugar,
protein, and fat molecules.
Breaks bonds to release the
high-energy electrons
captured in ATP.
Oxygen is electron magnet.
Note locations
Cellular
Respiration
The big picture
Three-Step
Process
Biggest ATP
“payoff” (90%)
occurs during the
electron transport
chain.
1st Step
Glycolysis
Study Slide
Four Main Steps in Cellular Respiration
1) Glycolysis (“sugar breaking”)
- location = cytoplasm
- each glucose breaks into 2 molecules
of pyruvic acid (pyruvate)
- 2 ATP’s used in reaction
- 4 ATP’s generated
- net gain = 2 ATP + 2 NADH
NADH (nicotinamide adenine dinucleotide)
- carries H atoms (e-) & ultimately loses e-
The Preparatory Phase to the Krebs Cycle
2nd Step
Getting Ready for the Krebs Cycle
Four Main Steps in Cellular Respiration
2) Formation of acetyl coenzyme A
- occurs in mitochondria (of eukaryotes)
- pyruvic acid loses e-; given to NAD+
- 1 C atom removed & leaves as CO2
- coenzyme A is added to modified
pyruvic acid
Result of last reaction = acetyl coenyme A
(Acetyl CoA) = high energy fuel that is
now ready to enter the next step
3rd Step
Four Main Steps in Cellular Respiration
3) Krebs (Citric Acid) Cycle
- location = matrix of mitochondria
For each turn in the cycle:
2 CO2 leave
3 NADH made
1 FADH2 made
1 ATP made
FADH2 = (flavin adenine dinucleotide)
same function as NADH = hydrogen (e-) carrier
Study Slide
4th Step
Follow the Electrons
#2) This proton concentration
gradient represents a significant
source of potential energy!
Four Main Steps in Cellular Respiration
4) Electron Transport Chain
- NADH & FADH2 transported to
mitochondria cristae
- electron carriers = membrane proteins
Four Main Steps in Cellular Respiration
4) Electron Transport Chain
- chemiosmosis
- cascading effect – protons travel
down an energy gradient
- 32-34 ATP generated
How Does Electron Transport Chain Work?
+
-
• NADH & FADH2 lose e- (H+ by-product)
• H+ gradient results in electrical gradient
• Flow of H+ through ATP synthase = ATP
Study Slide
Anaerobic Conditions (Fermentation)
Alcoholic (Glycolysis)
2 ATP’s
2 Ethanol
Lactic Acid
(Glycolysis)
2 ATP’s
2 Lactic Acid
4.17 Eating a
complete diet:
cells can run
on protein and
fat as well as
on glucose.
“Photo” and “Synthesis”
3
inputs
2
products
Photosynthesis = plants make food from
CO2 & H2O with the aid of solar energy
Chloroplast
- thylakoid
- granum
(grana)
- stroma
A Closer Look at Chloroplasts
Two Processes
1) Light Reactions (“Photo”)
(Light Energy to Chemical Energy)
- location = granum (a) / thylakoid
- Produce O2 as waste
- Light energy used to generate ATP &
NADPH (H carrier = e- source)
Two Processes
2) Calvin Cycle (“Synthesis”)
(CO2 to Sugar)
- location = stroma
- NADPH provides e- ATP powers the Cycle
Light Reactions
What is Sunlight?
- energy = radiation or
electromagnetic energy
- travels in waves
- also travels as particles of energy =
photons = kinetic energy
Photosynthetic pigments:
1) chlorophyll a (impt in light reactions)
2) chlorophyll b
3) carotene
4) xanthophyll
How Do the Light Reactions Work?
- Photosynthetic pigments absorb photons
- One of the pigment’s e- gain this energy
How Do the Light Reactions Work?
- High-energy e- is lost to a
primary e- acceptor
- e- shuttled through an e- transport chain,
thereby generating ATP
- Final e- acceptor = NADP+
Light Reactions
The “Photo” Part



Sunlight
ATP
A high-energy electron carrier
Electrons That Leave the
Photosystem Are Replenished
Where does oxygen come from?
An Electron Transport Chain
Connects the two photosystems
The Second Photosystem
 Follow
the electrons
Study Slide
How Do the Light Reactions Work?
** ATP & NADPH now ready to enter the
Calvin Cycle
Calvin Cycle
carbon fixation: convert CO2 into organic
compound (sugar)
What are the Ingredients?
What are the Products?
What is the Price?
-
The Calvin Cycle

Series of chemical
reactions

Occurs in stroma

Involves enzyme
The Processes in the Calvin Cycle
Occur in Three Steps:
Study Slide