Download Chapter 7: The Working Cell: Energy from Food Concept 7.1

Chapter 7: The Working Cell: Energy from Food
Concept 7.1: Sunlight Powers Life
I. Obtaining Food
A. Autotrophs are organisms that obtain their energy through the process of
photosynthesis such as green plants (aka self feeders, producers)
B. Heterotrophs are organisms that cannot make their own food but must obtain it from
another source. Animals are heterotrophs and depend on producers for energy (aka
consumers)
II.
Harvesting the Energy in Food
A. Plants and certain other producers use light energy to make organic
molecules (energy source).
1. H2O and CO2 are the raw ingredients
2. Glucose (C6H12O6) and CO2 are the products
3. Occurs by rearranging the atoms
B. Cellular Respiration is the process that converts this stored organic chemical
energy into a usable form ATP (adenosine triphosphate)
C. Both plant and animal cells then use ATP for energy and release CO 2 and
H2O (fig. 7.3)
Concept 7.2: Food Stores Chemical Energy
I. What is Energy? Forms of?
A. The ability to perform work or to move against an opposing force.
B. Kinetic Energy: Energy of motion
C. Potential Energy: Stored energy
D. B and C are inversely proportional!
II. Law of Conservation of Energy. Two important changes.
A. You cannot create or destroy energy you can only change its form.
B. Random molecular motion: Thermal energy!
1. Caused by atoms bouncing of off each other.
2. Thermal energy transferred from warmer to cooler is called Heat. (Can’t
be retrieved and put back to work that is one reason why we must
continue to eat.)
C. Stored potential energy: Chemical energy!
1. Potential to perform work is due to arrangement of the atoms and the
bonds holding them together. (create bond = stored energy;
break a
bond = release of energy)
2. Almost all organisms use one or more of the following: Carbohydrates,
Fats, and Proteins (fig. 7-5)
III. Chemical Energy at Work.
A. Cells vs. Engines: both work by breaking down complex chemicals into simple
ones (breaking bonds!)
B. Both use O2 to accomplish this and some energy is converted to thermal
(heat). (fig. 7-7)
C. Cell slower and more efficient than auto engines.
IV. Calories: Units of Energy
A. Amt. of energy required to raise 1g of H2O by 1 deg. C. (very small)
B. We use kcal or 1,000 calories. (food labels)
C. Calorimeter used to determine kcal. by burning dried food. (H2O has no
kcal’s)
D. Cells use enzymes not flame to release energy thus it is easier to manage.
Concept 7.3: ATP Provides Energy for Cellular Work
I. How ATP Packs Energy
A. Draw fig. 7-9.
B.
A=Adenine and 5-C sugar
T=Tri or Three (ref. to # of P)
P=Phosphate
B. Each P is a neg. charged molecule since likes repel, they want to separate
from each other- this contributes to the amount of potential energy avail. in
each bond. (break bond=release energy)
II. ATP and Cellular Work
A. Chemical reactions break ATP’s P bonds.
B. Enzymes enable this to occur.
C. The molecule that undergoes the change drives the work (creatine
phosphate)
D. Cells perform 3 types of work (fig. 7-10
1. Mechanical: muscle contraction
2. Chemical: building/breaking large molecules
3. Transport: pumping molecules across cell membrane
III. The ATP Cycle: (fig. 7-11)
A. ATP continuously converts to ADP and back
B. ADP can be converted back to ATP by reattaching the P with energy from
foods organic molecules
C. A working muscle regenerates all of its ATP molecules about once each min.
or 10 million per sec.
Concept 7.4: Electrons “fall” from food to O2 during cellular respiration
I. Relationship of Cellular Respiration to Breathing
A. Aerobic process-requires O2
B. O2 into the cell and out
C. Cellular respiration is not breathing or exchange of gasses in the lungs
(fig. 7-4)
II. Overall Equation for Cellular Respiration
A. Glucose+Oxygen-->Carbon Dioxide+Water+ATP
B. C6H12O6 + O2 --> CO2 + H2O + ATP
C. Main function is to create 38 ATP for each glucose
III. “Falling” Electrons as an Energy Source
A. Falling elect. like waterfall-at the top the potential energy is high as it falls it
becomes less
B. Atom’s positive nucleus pulls negative electrons the closer they get the more
potential energy they lose.
C. Positive O2 pulls strongly on electrons in the H2 and C thus rearranging the
atoms and releasing energy.
IV. Electron Transport Chain (fig. 7-15)
A. Controlled fall of electrons “step-by-step” walk.
B. Not burst (like flame) but series of controlled reactions
C. Electrons passed by carriers until O2 finally pulls electrons off at the end to
form H2O and release energy to make ATP.
Concept 7.5: Cellular respiration converts energy from food to energy in ATP
I. Mitochondria Structure (fig. 7-16)
A. Outer membrane and Inner highly folded membrane enclosing thick fluid
called matrix
B. Folds increase amt. of surface area for more reactions to occur. (fig. 7-16)
C. All chemical processes make up a cell’s metabolism
D. Specific enzymes catalyze (speeds up) each reaction in a metabolic
pathway
II. Stage I: Glycolysis (splitting of sugar)
A. Occurs in cytoplasm (fig.7-17)
B. 2 ATP “initial investment” to break the sugar
C. 1 C6H12O6 in and 2 pyruvic acids out (3-C each)
D. 2 ATP spent and 4 produced (net gain of 2)
III. Stage 2: The Krebs Cycle
A. Occurs in the matrix
B. Occurs twice for each glucose that entered stage one
C. Produces 1 ATP and electron carrier molecules
IV. Stage 3: Electron Transport Chain and ATP Synthase Action
A. Occurs in the inner membrane of mitoch.
B. Refer to the previous information on “falling electrons” 7-4.
C. Hydrogen ions pumped across the membrane to store energy like a dam
holding back water
D. ATP synthases (enzymes) act like mini turbines to convert ADP back into
ATP slowly.
E. As many as 38 ATP’s produced for each glucose that entered glycolysis.
Concept 7.6: Energy without O2
I. Fermentation in Human Muscle Cells
A. Fermentation makes ATP without using oxygen
B. This process is entirely glycolysis, which does not produce a lot of ATP
compared to all of cellular respiration but it is enough for short bursts of energy
C. The byproduct of fermentation is the build up of lactic acid in your muscles,
this is the soreness you feel after intense exercise
II. Fermentation and microorganisms
A. Like your muscles, yeast is capable of both cellular respiration and
fermentation
B. When yeast is kept in an anaerobic environment, they are forced to convert
sugar and other foods.
C. Instead of producing lactic acid as a waste product, fermentation in yeast cells
produces alcohol and carbon dioxide
D. There are also fungi and bacteria that produce lactic acid during fermentation
and help transform milk into cheese and yogurt giving them their
characteristic flavors