Transcript ATP - hdueck

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Chapter 9
Energy in a Cell
ATP
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9.1 – The Need for Energy (p. 221-224)
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Energy is essential to life.
Organisms are endergonic systems.
What do we need “E” for?
 Active Transport
 Cell Division
 Transport
 Synthesis (proteins)
 others
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ATP is the universal currency of energy
exchange in biological systems.
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No matter what form of energy a cell uses as its
primary source, the energy is ultimately
transformed and conserved as ATP.
•adenosine monophosphate (AMP)
nucleotide
• two phosphate groups
•pyrophosphate bonds (~P).
•These two bonds are energy rich in
the sense that their hydrolysis (breakage
which releases water) yields a great deal
more energy than a covalent bond of
another molecule.
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The ATP reaction is commonly written as:
ADP + Pi + energy ATP
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The forming of ADP into ATP
requires energy (endothermic) – 8 kcal/mole
 is pH dependent.
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Note: Forming ADP is like making a bank deposit
or coiling a spring for each phosphate bond. (see
figure 9.2 on p. 223)
The Calorie
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Kcal – kilocalorie
equivalent to 1000 calories.
 When we say that a cup of milk has 120 calories we
really mean 300 kilocalories or 300 000 calories.
 Even though we use the word calorie it is, by
definition, kilocalorie.
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The Mole
ABOUT THE MOLE:
Analogous to a dozen, it is a ”count” of molecules used in
chemistry and biochemistry.
1 mol = 6.022 x 1023 molecules
0.5 mol = 3.011 x 10 23 molecules
2.0 mol – 12.044 x 10 23 molecules or
1.2044 x 10 24 molecules
9.2 Photosynthesis: Trapping the
Sun’s Energy p. 225-230
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We’ve seen in our past learning that the cell uses
energy during ACTIVE TRANSPORT. Where
does this energy come from?
RECALL FROM EARLIER GRADES
All animals are heterotrophs - require food
sources of energy.
i.e. trophic levels in a food chain
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We do not make our own food for energy like plants, algae and
some bacteria (autotrophs). This is summarized by the carbonoxygen cycle below:
Photosynthesis: The Energy Maker
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Autotrophs under go PHOTOSYNTHESIS to
produce sugars (starches made up of glucose
molecules)—we say the sun’s energy is stored in
a chemical bond.
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Recall:
UV energy + CO2 + 6H2O  C6H12O6 + 6 O2
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In actuality, this reaction is elegant, but is not
simple.
MANY reactions occur inside the chloroplast’s
grana membrane.
The chlorophyll in chloroplasts is one pigment
(a green one, there are others) that absorbs sun
energy (all colours except green) which excite
electrons and cause a phosphate to attach to
ADP molecules.
LIGHT DEPENDENTREACTIONS
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Energized electrons provide energy that:
Forms ATP.
 Releases oxygen molecules (from the splitting of
H2O)
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See Fig. 9.5 p. 227
Fig. 9.6 p. 228
Light Independent Reactions/Dark
Reactions
At the same time (and more so at night when
there is no sun) the Calvin cycle takes place in
the stroma of the chloroplast.
 Powered by ATP
from photosynthesis
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Carbon dioxide gas (CO2) is taken in and used
to form sugars (CH2O is short hand to represent
many different types of sugar molecules, most
importantly glucose).
These are stored as starch granules in
chloroplasts.
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They are also transported to other cells and
accumulate in roots.
See Fig. 9.7 p. 229
The new summary of photosynthesis:
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Light dependent reactions:
12H2O + 12NADP + 18ADP → 6O2 + 12NADPH + 18ATP
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Light Independent reactions (*Calvin cycle)
6CO2 + 12NADPH + 18ATP→C6H12O6+12NADP+18ADP+6H2O
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Can you see how we get the overall Photosynthesis
equation?
The whole point of these reactions is to make a
safe, energy rich molecule, glucose.
9.3 Getting Energy to Make ATP
Cellular Respiration
 When we consume the sugars from plants,
(producers) or animals that have eaten plants
(primary consumers), energy from the sugar
bonds is released.
 The release of this energy is called respiration.
Recall:
C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy (ATP)
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Again, the reaction is elegant but far from
simple!
When animals and plants consume energy
molecules like starch and glucose, many
reactions occur.
Glycolysis (anaerobic)
 Citric Acid Cycle (aerobic)
 Electron Transport Chain
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-also aerobic
The last two occur
inside the mitochondrion.
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Glycolysis
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Glycolysis is the only metabolic pathway shared
by ALL organisms.
Occurs in the cytoplasm.
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i.e. not in an organelle
Glycolysis (cont’d)
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A process whereby glucose molecules are split in half
(makes a 3-C compound called pyruvate) in a series of
steps.
Glycolysis releases a 2 – ATP molecules per glucose
molecule that are used to drive other reactions AND
This process does not require O2
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Anerobic
See Fig. 9.8 p. 232
Aerobic vs. Anaerobic
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From here, pathways diverge in different organisms and
in different situations—oxygen poor (anaerobic) and
oxygen rich (aerobic).
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More about that later.
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BUT more ATP is made inside the mitochondrion
in two separate pathways:
The Citric Acid Cycle, CAC (KREBS CYCLE, KC)
 ELECTRON TRANSPORT CHAIN (ETC)
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CAC releases 1 ATP molecule
ETC releases 30 ATP molecules!
These reactions drive far more chemical reactions
in our tissues because of it.
Citric Acid Cycle (CAC)
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The CAC occurs inside the mitochondrial
matrix.
It is called a cycle, because one of its endproducts is recycled in the cycle.
Named because it forms citric acid
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an important intermediate molecule.
Citric Acid Cycle (cont’d)
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The main outcome is the generation of a variety of
energy intermediate molecules, not just ATP.
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GTP
NADH
FADH2.
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This cycle also releases 3 CO2 molecules per pyruvate
(3-C).
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See Fig. 9.10 p. 233
A diagram shows the numbers of energy
molecules generated:
animation
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The Electron Transport Chain (ETC)
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From the Krebs cycle (Citric Acid cycle) inside
the mitochondrion, the ETC occurs inside the
mitochondrial membrane.
It causes a cascade of energy release by using
the other energy molecules of NADH, FADH2
to cash in and make more ATP.
See Fig. 9.11 p. 234
The specialized molecules that do this are called
CYTOCHROMES and they pass excited
electrons from one cytochrome to another
stepwise—this releases even more ATP—30
more ATP!—in a controlled manner.
 This is where oxygen is consumed, and water
formed.
 TOTAL ATP from 1 glucose molecule:
- 2 gly - 2 (Act T)+ 2 CAC + 30 ETC = 32 ATP
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The schematic below shows how electrons transferred
from the NADH in Krebs are transferred in a cascade
of reactions in the ETC—note the need for flavin M
(part of the group of riboflavins, or B vitamins—B2)
and the role of iron ions (Fe).
This releases a LOT of ATP molecules.
Cellular Respiration Schematic
In summary
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In summary:
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SO, back to our original reaction—the
important component is the ENERGY:
C6H12O6 + 6O2  6CO2 + 6H2O + 32ATP
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We now know
where oxygen is consumed,
 how CO2 is generated,
 where the H2O comes from
 and how many energy molecules are made.
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Anaerobic Respiration
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If no oxygen continues to be present or, in some
organisms like yeast, where it is not used, fermentation
occurs.
This is also known as anaerobic respiration.
uses the 3-C molecules (pyruvate) and makes lactic
acid in our muscles or in yogurt) or ethanol (as in
brewing).
Anaerobic Respiration (cont’d)
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Only another 2 ATP molecules are made
This occurs with some fungi, and with
Lactobacillus acidophilus in yogurt, and in
yeasts.
This is the basis of cheese, yogurt, buttermilk,
root beer (real root beer), breads, wines, spirits.
Anaerobic Exercise
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In vigorous exercise, lactic acid builds up in our
muscles when we’ve exhausted the oxygen
supply in our haemoglobin
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i.e. We produce more lactic acid than our cells can
remove and they begin to seize up creating pain.
Athletes can increase their tolerance for lactic
acid.
Aerobic Respiration
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AEROBIC RESPIRATION occurs in our
mitochondria
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these pathways occur when oxygen is required (as in
us) and is present in sufficient amounts.
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Longer duration of exercise
For these cycles to occur, active transport of
pyruvate from glycolysis is needed – this uses up the
2 ATP that were made.
Metabolism
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METABOLISM refers to two contrasting cellular
activities:
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the total biochemical reactions required for energy making
reactions called CATABOLISM (includes breaking down
foods to store energy – ATP - in our tissues)
and
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the use of energy to synthesize cell material from small
molecules in the environment, called ANABOLISM (energy
consuming, using ATP to release energy).
Catabolic Reactions
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Produce energy in the chemical bonds of a molecule
called ATP (adenosine triphosphate).
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glycolysis
CAC
ETC
lead to end products, which are "waste products" like
water and CO2
most important—they generate ATP which is later
used in anabolic reactions to build cell material from
nutrients in the environment, like muscle tissue.
Anabolic Pathways
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Lead to release of the energy to drive other reactions.
These reactions make important molecules like
proteins for our muscles, hair, nails, lipids for our fatty
tissues, and so on.
When energy is required during anabolism, it may be
spent as the breaking of a high energy bond of ATP
which has a value of about 8 kcal/mol of ATP
molecules. This is like a withdrawal from your account.
Role of Water
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Breaking the ATP to make ADP releases 8
kcal/mol. The ATP reaction is commonly
written as:
ATP  ADP + Pi + 8 kcal/mol
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The diagram showing the relationships between
catabolism and anabolism is not to be
memorized, but to help you understand the
connections:
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IMP: During catabolism, energy is changed from one
form to another, but such energy transformations are
never completely efficient, i.e., some energy is lost in
the form of heat. This forms part of our body heat.
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In both catabolism and anabolism, energy is formed
stepwise and broken down stepwise in a number of
cycles.
This controls the amount of energy stored or released.
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The energy is passed along in two energy
processes: Exergonic reactions and
Endergonic reactions.
Videos
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YouTube - Photosynthesis and Cellular Respiration Rap
YouTube - cellular respiration (Hey There Delilah)
YouTube - Cellular Respiration (Original Song) Music Video
YouTube - austin powers in cellular respiration
YouTube - Cellular Respiration-Clay Animation
YouTube - Cellular Respiration-"I Believe in Glycolysis“
YouTube - Photosynthesis and Cellular Respiration-Parking
Garage
YouTube - Cellular Respiration
YouTube - Cellular Respiration Dance