Download ATP powers cellular work

ATP powers cellular work
Ch. 3 – Mitochondria and
Cellular Metabolism
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Most cells receive energy in a form they
can’t use directly
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ATP and cellular work
Enzymes
Cell respiration
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ATP
A complex organic molecule
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ATP (adenosine triphosphate)
NAD (nicotinamide adenine dinucleotide)
ATP power
The Structure of ATP
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Energy from food
This energy has to be converted into a
usable form of energy
ADP
Adenosine plus a “tail” of 3 phosphate groups
containing a high-energy bond
The energy in ATP is used to
drive cellular work
Cells use ATP to build
macromolecules
The ATP Cycle
To transport molecules
across the membrane
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To move cells - by cilia or flagella
ATP stores energy obtained from food and
releases it as needed at a later time
Chemical reactions in the cell
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The making or breaking of
chemical bonds
Energy
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Substrate
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Cell chemistry–catalyzed reactions
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Substrates – starting
molecules
Products – molecules at the
end of the reaction
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Activation energy–energy
needed to start the
reaction
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4 characteristics of enzymes
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speed up chemical reactions
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Decrease the activation
energy
Recycled
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Lower the activation energy
This process is called
catalysis
We say that enzymes are
catalysts
How enzymes work
Proteins
Act as catalysts
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Cells use enzymes to
speed up chemical
reactions
Each enzyme is very
selective – it recognizes
its substrate
The substrate binds to a
special region of the
enzyme, the active site
enzymes can function over
and over again
How enzymes work
Cells can control enzymes
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Enzyme inhibitors
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Molecules in the cell
inhibit (slow down or
stop) enzymatic
reactions
Many bind to the
active site, as
substrate imposters.
Recap: Enzymes
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Workhorse proteins
Speed up reactions
Orchestrate the majority of chemical reactions
needed for life
Obtaining energy from food
Cellular respiration
We use the energy that plants
capture from the sun
Cellular respiration
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How Cells
Harvest Energy
from Food
Sugar (Glucose)
Where Is the Energy in Food?
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Cellular Respiration:
Sugar  ATP
Stored in chemical bonds between the
C, H and O atoms
+
Cellular respiration
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the process of harvesting this energy and
converting it to ATP
6 O2

6 CO2
+
Glucose
C6 H12O6
Gives electrons & hydrogen to
Energy Released
+
What is cellular respiration?

An overview of cellular respiration
Cells break down glucose and capture the
released energy as ATP
3 steps
1.
Glycolysis
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Inside cell
electrons
transferred
by NADH
glucose
1
2
Citric
acid
cycle
Glycolysis
glucose
electrons
transferred
by NADH
pyruvate
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2.
Citric acid cycle
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3
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Electron
transport
chain
3.
occurs in the cytosol
Produces ATP
occurs in mitochondria
Produces ATP, high
energy electrons
Electron transport
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generates most ATP
oxygen
mitochondrion
2
ATP
2
ATP
32
ATP
Outside cell
Step 1: Glycolysis
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Breaks down glucose
into 2 pyruvic acid
molecules
Generates ATP
Occurs in cytoplasm
Anaerobic – does not
require oxygen
Step 2: the Citric Acid Cycle
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A series of chemical reactions
that yields a small amount of ATP
Step 1: Glycolysis
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Glycolysis yields only a
small amount of ATP
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only 2 ATP are made for
each molecule of glucose
But it’s the only way to
get energy from food in
the absence of oxygen
Step 3: Electron Transport
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many high-energy
electrons carried by NADH
and
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Glycolysis
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High-energy electrons move to
electron transport chain where
more ATP is produced
mitochondria
Aerobic (requires O2)
Occurs in the
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NADH transfers
electrons to the
electron transport
chain
Cells use the stepwise
release of energy to
make ATP
Adding up the ATP from
cell respiration
Some of the deadliest poisons
disrupt electron transport
Both carbon monoxide and
cyanide kill by blocking the
transfer of electrons to
oxygen and stopping ATP
synthesis.
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The glucose molecule is entirely consumed
The energy from its chemical bonds is transformed into highenergy molecules
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Glycolysis
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occurs in the cytoplasm
does not require oxygen
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generates ATP
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occurs in mitochondria
requires oxygen
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anaerobic
Citric acid cycle
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aerobic
generates ATP and high-energy
electrons
Products
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Citric acid cycle and
electron transport don’t
operate
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occurs in mitochondria
requires oxygen
Generates most of the ATP
Fermentation:
an anaerobic process
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Fermentation in muscle cells
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A little ATP
Lactic acid
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When you run, your muscle
cells use up the oxygen
Muscle cells switch over to
making ATP by fermentation
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Lactic
acid
ATP
Some cells can work
for short periods
without O2
How do they get
energy from glucose in
the absence of
oxygen?
Electron transport chain
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More
Fermentation
Recap: Cellular respiration
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4 ATP molecules
10 NADH electron carriers
2 FADH2 electron carriers
Convert glucose to lactic
acid
When O2 is available, lactic
acid is converted back to
pyruvic acid
It takes about 10
million ATP
molecules per second to power
an active muscle cell