Download Chapter 7- Energy

Chapter 7-Energy from Food
Life on Earth is solar-powered.
Photosynthetic organisms convert the
energy of sunlight into chemical
energy in foods.
Classification of Organisms
 Autotrophs (self-feeders)=Producers.
– Start with inorganic molecules and make
organic molecules.
– Process of Photosynthesis:
reactants
products.
6CO2 + 6H2O + energy
C6H12O6 + 6O2.
– Plants, algae,seaweed, and photosynthetic
bacteria.
 Heterotrophs (other eaters)=Consumers.
 Obtain food by eating producers or other
consumers.
Cellular Respiratation
Producers and consumers-plants and
animals.
Chemical process- oxygen converts
chemical energy in food into chemical
energy of ATP
Reactants
Products
C6H12O6 + 6O2
6CO2 + 6H2O + energy
(38 ATP)
ATP main energy source for work.
Chemical Recycling

 Water, carbon
dioxide (CO2),
oxygen, and
glucose are
continually
recycled.
Concept 7.2- Energy
Definition of energy2 basic forms–
–
–
–
–
–
Kinetic energy- energy in motion
Potential energy- stored energy
Example- climbing stairs.
Class examplesEnergy is not created or destroyed.
Energy is converted from one form to another.
Water slide analogy-.
– What happens to the energy as we come
to a stop?
– What is thermal energy?
– A type of kinetic energy in which there
is random movement of molecules.
– Heat is thermal energy that is transferred
from a warmer object to a cooler one.
– The thermal energy that occurs when we
exercise cannot be retrieved. To do more
work we need more energy provided by
the foods we eat.
Chemical Energy -a form of
potential energy found stored in
foods.

Putting Chemical Energy to
Work
 Organic molecules in food are high in chemical
energy
 Glucose reacts with oxygen in cellular
respiration.
 The “exhaust” is water and carbon dioxide.
 Cells are more efficient than autos. 40% of
energy from food is used for work.
 The other 60% is lost as heat (thermal energy)
 Calorie= amount of energy to raise the
temperature of 1 gram of water by 10 C.
 A calorie is too small- We use kcal=1,000 cal.
ATP provides energy for the cell
Key- Chemical energy in food has to be
converted to energy stored in ATP.
ATP Adenosine triphosphate.
Adenosine= 5 carbon sugar ribose +
nitrogen containing compound adenine.
Triphosphate= tail of 3 phosphate groups.
How ATP Packs Energy
 The phosphate groups are the source of energy.
 Each phosphate group is negatively charged and
since like charges repel, this contributes to the
potential energy stored in ATP.
 Spring comparison.
 A chemical reaction breaks one of the phosphate
bonds and potential energy is released.
 The result is ADP= Adenosine diphosphate.
Types of Cellular Work
 The Phosphate group is transferred to another
molecule by specific enzymes.
 The molecule that accepts the phosphate group
changes, driving the work.
 3 types of work– Chemical work- building molecules
– Transport Work- moving solutes across membranes
– Mechanical Work- muscle contractions.
ATP Cycle is Continuous

 Work consumes ATP.
 ADP and phosphate
regenerate ATP.
 The source of this
energy is the organic
molecules in the food
we eat.
 Very fast reaction.
Cellular Respiration
 An aerobic process- Oxygen is needed
 Cellular respiration’s main function to generate
ATPs
 Cellular respiration transfers hydrogen and
carbon atoms from glucose to oxygen forming
CO2 and H2O.
 “Falling electrons”-released from C-H bonds fall
towards oxygen ( an electron grabber), releasing
energy.
 Electron Transport Chains- a series of transfers in
which electrons are passed from one electron
carrier to the next releasing energy to make ATP.
3 stages of Cellular Respiration
Stage 1- Glycolysis- “splitting of sugar.”
– occurs in the cytoplasm of the cell.
– Oxygen is not used in this step- Anaerobic.
– 6 C glucose molecule is broken down into two
3C pyruvic acid molecules.
– Results in 2 ATPs being produced.
– Glycolysis transparency- figure 7-17 pg. 149.
Glycolysis:

Stage 2- Krebs Cycle.
– Occurs in the cell’s mitochondria.
– Each Pyruvic acid (from glycolysis) is broken
down into a 2C molecule called Acetyl CoA.
– Each AcetylCoA enters the Krebs cycle and
produces 1 ATP.
– Since there are two Pyruvic acid molecules
this results in 2 ATPs per glucose molecule.
– Krebs Cycle transparency- figure 7-18 pg.150.
Krebs Cycle

 Stage 3- Electron Transport Chain.
– Occurs in inner membrane of mitochondria.
– 2 parts.
• Electron transport chain.
– Electrons are pulled to oxygen at the end
of the chain.
• ATP production.
– Energy released during each transfer
provides for ATP to be formed from
ADP and Phosphate.
– Results in 34 ATPs per glucose molecule.
Electron Transport Chain.
A staircase, releasing energy at each step.
Electron Transport Chain

Result of Cellular Respiration
To generate ATP for cellular work.
One glucose molecule yields 38 ATP.
– Glycolysis= 2 ATP.
– Krebs Cycle= 2 ATP.
– Electron Transport Chain= 34 ATP.
Most ATP production requires oxygen.
We cannot survive long without oxygen!!!
Fermentation- Anaerobic
 Makes ATP when oxygen is not available.
 Makes ATP from glycolysis.
 Yield of 2 ATP.
 Fermentation regenerates enough ATP for short
bursts of activity.
– Ex. A sprint (not a marathon).
 Fermentation in muscle cells produces lactic acid
– a waste product resulting in fatigue.
 Since oxygen is consumed to convert lactic acid
back to pyruvic acid, we have increased breathing
after exercise.
Fermentation in Microorganisms
Yeast ferment sugar producing alcohol.
– This is alcoholic fermentation.
– Beer, wine, champagne.
– Baker’s yeast- CO2- makes bread rise.
Fungi and bacteria produce lactic acid in
fermentation.
– Milk is transformed into yogurt and cheese.
– Cabbage is transformed into sauerkraut.