Download 2 - Warner Pacific College

METABOLISM
METABOLISM

What is metabolism?


Total of all chemical reactions occurring within the
body
Categories of metabolic reactions

Catabolic reactions


Degradation pathways
Anabolic reactions

Synthesis pathways
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METABOLISM
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ENERGY

What is energy?

No mass; does not take up space

Has the capacity to do work (potential energy) or to
put matter into motion (kinetic energy)

Can be converted into different forms but is not
created or destroyed
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ENERGY

What types of energy are there?

Chemical


Electrical


Involves movement of charged particles
Mechanical


Energy stored in chemical bonds
Involves movement of matter
Electromagnetic (radiant)

Energy traveling in waves
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Quick Quiz: Potential energy can be
“stored” in all of the following forms
except…
A) Electromagnetic energy
B) Electrical energy
C) Mechanical energy
D) Chemical energy
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ENERGY

Where does our energy for metabolism come
from?

Chemical energy


Nutrients (food)
Electromagnetic energy

Heat (thermal)


Sun or geothermal sources
Visible light
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ENERGY

Energy for cellular metabolism must be “refined”, or
converted to useful types of energy

Photosynthesis


Electromagnetic energy (sunlight)  chemical energy
Aerobic respiration

Chemical energy (chemical bonds of certain molecules)
 chemical energy (more usable form for cells)
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ATP (adenosine triphosphate)
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Quick Quiz: ATP is an example of
which of the following energy forms?
A) Electromagnetic energy
B) Thermal energy
C) Mechanical energy
D) Chemical energy
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Energy Flow & Nutrient Cycling
in Biological Systems


Energy

1-way flow

Ultimately lost as
heat
Nutrients

Cycled
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Nutrients

What are nutrients?

Chemical substances needed for normal metabolism &
growth

O C

Ca
H N
P K S Na
Cl Mg I Fe

Organic vs. inorganic nutrients

Macronutrients

Proteins

Carbohydrates

Lipids

Nucleic acids
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Quick Quiz: Which of the following is
NOT recycled in an ecosystem?
A) Carbon
B) Electromagnetic energy
C) Water
D) Nitrogen
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ENZYMES

Chemical reactions

Reactants are converted into products

Atoms become combined in new forms
O2 + 2 H2

2 H2O
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ENZYMES


Reaction rates

Typically too slow to sustain life

Need help to speed up
Enzymes are biological catalysts



Catalysts speed up reactions
They do not make a reaction happen that wouldn’t
have happened otherwise
Enzymes are usually made out of protein
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ENZYMES


Reaction rates

Typically too slow to sustain life

Need help to speed up
Enzymes are biological catalysts



Catalysts speed up reactions
They do not make a reaction happen that wouldn’t
have happened otherwise
Enzymes are usually made out of protein
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ENZYMES

In order to react, molecules go through awkward
transitions


Unstable, high-energy states: Transition states
Enzymes help to speed up reactions by stabilizing
transition states
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ENZYMES
Reactants:
2H2
O2
Free energy
Activation energy
Difference between free energy
of reactants and products
Time
Products: 2H2O
Quick Quiz: True or false: An enzyme
makes a reaction that wouldn’t have
happened
A) True
B) False
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Quick Quiz: The difference between
the amount of energy in reactants and
the maximal amount of energy in the
transition state is called…
A) Activation energy
B) Free energy
C) Catalyst
D) Potential energy
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Photosynthesis
C6H12O6
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Photosynthesis

Occurs in chloroplasts

Outer membranes (2)

Thylakoid membrane system

Stroma
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Photosynthesis

Two distinct events


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Light-dependent reactions (light reactions)

Occurs in thylakoids of chloroplasts

Energy from sunlight used to generate ATP &
NADPH

Splits H2O, releasing O2 as a byproduct
Light-independent reactions (dark reactions)

Occurs in stroma of chloroplasts

Uses CO2, ATP &
NADPH to synthesize
glucose
Photosynthesis

Process summary
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Photosynthesis

How is light energy actually captured and
converted into chemical energy?



Photopigments capture photons of light

Chlorophylls (a, b)

Accessory pigments (carotenoids, phycobilins)
Electron carriers transfer energy to form ATP &
NADPH
Calvin-Benson cycle uses the ATP & NADPH to “fix”
CO2 into sugars (glucose)
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Quick Quiz: Which stage of
photosynthesis requires carbon
dioxide?
A) Light-dependent reactions
B) Light-independent reactions
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Quick Quiz: True or false: the goal of
photosynthesis is to produce oxygen.
A) True
B) False
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Light-Dependent Reactions

Photopigments & the Electromagnetic Spectrum
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Photopigments & the Electromagnetic Spectrum
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Englemann’s Experiment
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Light Capture & Energy Transport

Two photosystems for capturing light energy
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Quick Quiz: In a plant cell, which of the
following is NOT where you would find
chlorophyll?
A) Photosystem I
B) Photosystem II
C) ATP synthase
D) Thylakoid membrane
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Quick Quiz: What is the final product
of the “light reactions”?
A) glucose
B) starch
C) ATP
D) NADPH
E) C and D only
F) All of the above
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Light-Independent Reactions

Calvin-Benson cycle

Occurs in stroma of chloroplast

Use ATP & NADPH generated during light-dependent
reactions

Carbon fixation

6 CO2 + 6 RuBP  1 glucose

Rubisco (enzyme)
RuBP = ribulose bisphosphate
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Photosynthesis

Process summary
C6H12O6
ATP + NADPH
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Quick Quiz: How many carbon atoms
does RuBP have?
(Just press the number on your
keypad that corresponds with your
answer.)
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Quick Quiz: Which of these is a
product of the Calvin-Benson cycle
(aka the “dark-reactions” or “lightindependent reactions”)
A) ATP
B) glucose
C) NADPH
D) CO2
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Variations to Photosynthetic Systems in Plants

Differences in environments (light intensity,
temperature, rainfall, soil conditions, etc) can
affect how photosynthesis proceeds in plants

How to deal with hot, dry conditions
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Stomata

Allow gas exchange through leaves (O2, CO2,
H2O)

Close in hot dry weather to prevent excess water loss

Causes increase in O2 levels; decrease in CO2 levels

Triggers photorespiration (bad news!)
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C3 Plants
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
E.g., evergreen trees (temperate zones)

With stomata closed…

Rubisco fixes O2 when CO2 levels drop

Efficiency reduced
by 1/2
C4 Plants


E.g., grasses, corn, tropical plants
Two carbon fixation steps

Each fixed in different types of cells
Maintain higher internal
CO2 levels in the cells that
make sugar than C3’s


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Lose less water, make
more glucose than C3
plants during hot/dry
conditions
CAM Plants
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
E.g., cactus, desert plants

Stomata close during the day and open at night

Carbon fixation occurs at night

Most efficient under
hot/dry conditions
Quick Quiz: Which of the following
plants uses a 4-carbon molecule in the
Calvin cycle?
A) Corn
B) Douglas fir
C) Saguaro cactus
D) A and B
E) A and C
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“The Circle of Life”
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“The Circle of Life”
36 ATP
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Aerobic Respiration
C6H12O6 + 6 O2  6 CO2 + 6 H2O + 36 ATP
glucose
oxygen
carbon dioxide
water
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Aerobic Respiration

Involves 3 linked processes

Glycolysis

Citric acid cycle


TCA (tricarboxylic acid cycle) / Krebs cycle
Oxidative phosphorylation

Respiratory transport chain / electron transport
chain

ATP synthase
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Aerobic Respiration
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Glycolysis

“Sugar splitting”

Occurs in cytoplasm

Net reaction:
1 glucose  2 pyruvate + 2 ATP + 2 NADH
C6H12O6
C3H3O3
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Glycolysis (part 1)
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Glycolysis (part 2)
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Glycolysis

Bottom line…
1 glucose  2 pyruvate + 2 ATP + 2 NADH

Glucose (6 C) split into 2 molecules of pyruvate (3C)
 To TCA cycle
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Glycolysis

Bottom line…
1 glucose  2 pyruvate + 2 ATP + 2 NADH


Glucose (6 C) split into 2 molecules of pyruvate (3C)
Uses 2 ATP, produces 4 ATP  net yield of 2 ATP
 Available for immediate energy needs
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Glycolysis

Bottom line…
1 glucose  2 pyruvate + 2 ATP + 2 NADH



Glucose (6 C) split into 2 molecules of pyruvate (3C)
Uses 2 ATP, produces 4 ATP  net 2 ATP
Produce reducing potential (NADH)
 To electron transport (oxidative phosphorylation)
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Quick Quiz: The end result of
glycolysis is 2 molecules of ________.
A) Carbon dioxide
B) Oxygen
C) Glucose
D) Pyruvate
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Quick Quiz: True or false: Plant cells
have mitochondria.
A) True
B) False
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TCA Cycle

Occurs in mitochondria


Matrix (inner compartment)
Net reaction:
2 pyruvate  6 CO2 + 2 “ATP” + 8 NADH + 2 FADH2
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TCA Cycle
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TCA Cycle

Bottom line…
2 pyruvate  6 CO2 + 2 “ATP” + 8 NADH + 2 FADH2

Glucose now completely oxidized to CO2


Diffuses from cell
Generates lots of reducing potential (NADH, FADH2)

To electron transport chain (ETC)
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Quick Quiz: Which of the following is
NOT a product (or byproduct) of the
TCA cycle?
A) NADH
B) FADH2
C) ATP
D) Pyruvate
E) CO2
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Oxidative Phosphorylation

Occurs in mitochondria (inner membrane)

Most efficient system for ATP generation

Net reaction:
10 NADH + 2 FADH2 + 6 O2  32 ATP + 6 H2O
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Oxidative Phosphorylation
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Oxidative Phosphorylation
ATP
INNER
COMPARTMENT
ADP
+
Pi
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Oxidative Phosphorylation
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Oxidative Phosphorylation

Bottom line…
10 NADH & 2 FADH2 + 6 O2  32 ATP + 6 H2O

Use “energy carriers” (NADH, FADH2) from glycolysis and
TCA cycle to generate ATP

O2 is the terminal acceptor for the transferred electrons

Involves ATP synthase

Uses H+ concentration gradient
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Aerobic Respiration
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Quick Quiz: Where is the electron
transport chain located?
A) Cytoplasm
B) Mitochondrial matrix
C) Outer mitochondrial membrane
D) Inner mitochondrial membrane
E) Intermembrane space (outer compartment)
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Quick Quiz: What would happen to
oxidative phosphorylation if oxygen
were not available?
A) Oxidative phosphorylation would cease
B) Oxidative phosphorylation would increase
C) Oxidative phosphorylation would occur at
the same rate
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Anaerobic Respiration

ATP generation in the absence of O2

Involve terminal electron acceptors other than
oxygen

E.g., O-containing salts (nitrates, nitrites, sulfates,
sulfites)

Anaerobic bacteria
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Anaerobic Respiration

ATP generation in the absence of O2

ATP produced through glycolysis with lactic acid
and/or ethanol and CO2 as end products

Fermentation


Lactic fermentation

Alcoholic fermentation
Decreased efficiency; have to deal with by-products
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Lactic Fermentation
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Alcoholic Fermentation
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Alternate
Energy
Sources &
Biosynthesis
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Quick Quiz: True or False – The TCA
cycle can only be used to oxidize
(process) pyruvate.
A) True
B) False
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