Transcript ATP

Chapter 4
The ENERGY of LIFE
Energy
Energy = the ability to do work
Potential energy = stored energy
available to do work
Kinetic energy = energy being used to do
work
Laws of Thermodynamics
& Entropy
First law – energy cannot be created nor
destroyed, it can only be converted to
other forms
Second law – all energy transformations
are inefficient because every reaction
loses some energy to the surroundings in
the form of heat
Entropy = a measurement of the disorder
in a system
Chemical Reactions
Absorb or Release Energy
Reactions that absorb
energy – the products
contain more energy than
the reactants
Reactions that release
energy – the reactants
contain more energy than
the products
Energy in
Energy in
Energy out
Energy out
Redox Reactions
Reduction = gain of an electron
Oxidation = loss of an electron
Redox reaction:
Ae- + B → A + Be-
Figure 4.5
Electron Transport Chain
A chain of electron donors and recipients
(redox reactions)
e−
Energy
Energy
Energy
Energy
Electron donor
molecule
Electron acceptor
molecule
e−
Figure 4.17
ATP is Cellular Energy Currency
Release of energy:
Storage
ADP
ATP ++ H
P2O
+ energy
→ ADP→
+P
ATP
+ energy
+ H 2O
ATP represents short-term energy
storage
P
H2O
P
P
P
P
P
Hydrolysis
ATP
ADP
+
Energy
Enzymes
Enzyme = a biological catalyst
• Catalyst = a substance that speeds up a
biochemical reaction without being
used up or altered in the reaction
• Enzymes are typically proteins
Figure 4.10
How Enzymes Work
Enzymes bring reactants together
Enzymes lower activation energy
Active site exhibits exactness with the
substrate
Substrate
Products
Active site
Enzyme
Enzyme
Enzyme-substrate complex
Figure 4.11
Enzyme Inhibition:
Non-competitive & Competitive
Competitive
Normal
Non-competitive
binding
inhibition
–inhibition
the active
– an –inhibitor
site
an inhibitor
is
unobstructed
molecule
binds
and
to is
a site
the
anactive
exact
othersite;
match
thanthe
the
to
the substrate;
active
substrate
site,can
changing
no
thelonger
substrate
the shape
is free
of the
to bind
to thetoenzyme
active
bind
site;
the active
the substrate
site
can no longer bind to the
active site
Substrate
Inhibitor
Active site
Enzyme
Enzyme
Enzyme
Inhibitor
Noncompetitive
Competitive
Normal
inhibition
inhibition
binding
Factors That Affect Enzyme Activity
pH changes
Salt concentration changes
Temperature
Pharmaceuticals
Poisons
Membrane Transport – Passive:
Requires No Input of Energy
Osmosis == simple
Diffusion
net movement
diffusionofofa water
substance
down down
across
a selectively
a concentration
permeable
gradient
membrane
(from a region of high concentration to a
region ofsolutions:
Osmotic
low concentration)
• Isotonic – the concentration of solute is
Simple
equaldiffusion
by comparison
= diffusion of a
•substance
Hypotonic
without
– the concentration
the aid of a transport
of solute
protein
is lower by comparison
• Hypertonic – the concentration of
Facilitated
solute is diffusion
higher by=comparison
diffusion of a
substance with the aid of a transport
protein
Membrane Transport – Active:
Requires An Input of Energy
Creates and maintains concentration
gradients (e.g. Sodium-potassium pumps)
Requires energy-demanding transport
proteins
Figure 4.19
4.18
Endocytosis & Exocytosis
Bulk Transport of Materials
Exocytosis – –allows
Endocytosis
allowsa acell
celltotouse
usevesicles
vesicles
to
transport
to transport
bulk quantities
bulk quantities
of fluids and
of
fluid and
large
molecules
large molecules
outside inside
• Pinocytosis = the cell takes
in small amounts of fluid
and dissolved particles
• Phagocytosis = the cell
takes in large particles
Chapter 5
PHOTOSYNTHESIS
Autotrophs & Heterotrophs
Autotroph (“self-nourish”) – an organism
that produces organic compounds from
inorganic substances
Heterotroph (“other-nourish”) – an
organism the obtains organic compounds
by consuming other organic compounds
Photosysthesis
Reaction:by which organisms convert
Process
solar energy (light) into chemical energy
6 CO2 + 6 H2O → C6H12O6 + 6 O2 *
Series of reactions that generate glucose
*from
Light
carbon
energy
dioxide
and photosynthetic
pigments must be present
Water is a reactant; oxygen is a product
Figure 5.2
Electromagnetic Spectrum
Visible light is only a small portion of the
electromagnetic spectrum
Short wavelength (high energy)
Gamma rays
Visible light
400
X-rays
Violet
450
Portion of
spectrum that
reaches Earth's
surface
Ultraviolet
radiation
Infrared
radiation
Wavelength in nanometers
Photons = discrete packets of energy
found in light
500
550
Orange
650
Wavelength
700
750
Radio waves
Long wavelength (low energy)
Green
Yellow
600
Wavelength = the distance a photon
moves during one complete vibration
Microwaves
Blue
Cyan
Red
Photons & Wavelength
Photons = discrete packets of kinetic
energy found in visible light
Wavelength = the distance a photon
moves during a complete vibration
• The shorter the wavelength, the more
energy
• Different wavelengths are perceived as
different colors
Plant Pigments Capture Light Energy
Chlorophyll a – primary green pigment in
plants
Accessory pigments:
• Chlorophyll b
• Carotenoids
Figure 5.3
Plant Absorption Spectrum
Relative absorption (percent)
80
Chlorophyll a
Chlorophyll b
Carotenoids
Sunlight
Reflected
light
60
40
20
0
400
500
Wavelength of light (nanometers)
600
700
Figure 5.4
Leaf Anatomy:
Stoma & Mesophyll
Plants exchange gases with the
atmosphere through stomata (= small
openings in the epidermis
Most photosynthesis occurs in the
interior of the leaf
(= mesophyll)
Mesophyll
cells
Stoma
CO2
O2
+ H2O
Figure 5.4
Leaf Anatomy:
Chloroplast Structure
DNA
Outer
membrane
Inner
membrane
Granum
Stroma
Ribosomes
Figure 5.4
Leaf Anatomy:
Granum/Thylakoid Anatomy
Thylakoid
Thylakoid
membrane
Proteins
Thylakoid
space
Chlorophyll
Figure 5.6
Overview of Photosynthesis
Photosynthesis occurs in two stages:
• Light reaction – converts solar energy
into chemical energy
• Carbon reaction – uses chemical
energy to assemble glucose from
carbon dioxide
Light
H2O
CO2
ATP
Light
reactions
NADPH
NADP+
Carbon
reactions
ADP
Photosynthesis is a redox reaction:
• Oxygen atoms in H2O are oxidized
• Carbon atoms in CO2 are reduced
O2
Glucose
Figure 5.7
The Light Reaction:
Photosystem II Produces ATP
Photosystem II
Light energy
Electron transport chain
H+
Reaction center
chlorophyll
H+
Stroma
Pigment
molecules
H2O
2e–
½ O2 + 2H+
Thylakoid space
ATP synthase
H+
Stroma
ADP +
P
ATP
Figure 5.7
The Light Reaction:
Photosystem I Produces NADPH
Photosystem II
Light
energy
Electron transport chain
H+
Reaction center
chlorophyll
H+
Photosystem I
Light
energy
Stroma
Pigment
molecules
H2O
2e–
½ O2 + 2H+
Thylakoid space
ATP synthase
H+
Stroma
ADP +
P
ATP
Electron transport chain
NADP+
NADPH
Figure 5.8
The Carbon Reaction
(Calvin Cycle)
Step 2:
1: PGAL
3:
Carbonsynthesis
Regeneration
Fixation
of –
RuBP
three
six molecules
–molecules
five
molecules
of
CO2 combine
PGA
(two
offrom
PGAL
with
each
are
three
intermediate)
used
molecules
to assemble
are
of
RuBPmolecules
three
converted
to form
to six
three
of
molecules
RuBP
molecules
of PGAL
of an
unstable intermediate
P
3 P
3 P
3
P
Unstable intermediates
CO2
RuBP
6
From light
reactions
P
Rubisco
PGA
enzyme
3 ADP
6
ATP
6 NADPH
3
3 P
RuBP
ATP
P
6
6 NADP+
P5
PGAL PGAL
3 P
P6 ADP + 6 P
6
P
Unstable intermediates
P
PGAL
Glucose Formation
Six molecules of PGAL are synthesized,
but only five are needed to regenerate the
three molecules of RuBP
The remaining PGAL is the raw material
for the glucose
5
P
6
PGAL
Two turns of the Calvin
cycle results in one
molecule of glucose
P
PGAL
1
P
PGAL
Glucose
Carbon Fixation Pathways
C3, C4, and CAM plants use different
carbon fixation pathways
Photorespiration:
• RuBP combines with oxygen instead of
carbon dioxide
• ATP and NADPH are wasted
• Limits the efficiency of photosynthesis
• Most likely to occur in hot, dry climates
where plants risk losing too much water
if stomata remain open too long
Figure 5.9
Carbon Fixation Pathways – C4
C4 plants separate the light reactions and
the carbon reactions
• Light reactions occur in mesophyll cells
• Carbon reactions (Calvin Cycle) occurs
in bundle sheath cells
• Bundle-sheath cells
are not exposed to
atmospheric O2
C4 plant
Photorespiration is
avoided
Bundle-sheath
cell
Stoma
Mesophyll
cell
Vein (vascular tissue)
Figure 5.10
Carbon Fixation Pathways – CAM
CAM = crassulacean acid metabolism
CAM plants only open their stomata at
night for carbon fixation
Light reactions and carbon reactions take
place during the day
Photorespiration is avoided
Figure 5.10
Carbon Fixation:
C4, C4, and CAM Pathways Compared
C3 plant
C4 plant
CO2
CO2 or O2
CAM plant
Night
Mesophyll
cell
Mesophyll
cell
4-carbon molecule
4-carbon molecule
Mesophyll
cell
Pathway
Calvin
cycle
Glucose
Bundlesheath
cell
CO2
CO2
CO2
Calvin
cycle
Calvin
cycle
Glucose
Glucose
Habitat
Cool, moist
Hot, dry
Day
Hot, dry
Chapter 6
HOW CELLS
RELEASE ENERGY
Aerobic Respiration
Process by which organisms use oxygen
gas and glucose to produce chemical
energy (ATP)
Essentially the reverse of photosynthesis
Reaction:
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 36 ATP
Fermentation
Process by which organisms use glucose
to produce chemical energy (ATP) when
oxygen gas is unavailable
Figure 6.2
Overview of
Aerobic Cellular Respiration
Aerobic cellular
Process
occurs in
respiration
three stages:
is a redox
• Glycolysis – splits one molecule of
reaction:
• Carbon
glucoseatoms
into two
in CO
molecules
of pyruvate
2 are oxidized
• Oxygen
Krebs Cycle
atoms
– oxidizes
in H2O reduced
pyruvate and
releases carbon dioxide
• Electron
The
reaction
transport
releaseschain
energy
– generates
stored in
the
ATP
glucose molecule
Glycolysis
Glucose
ATP
NADH
2 Pyruvate
CO2
NADH
NADH
Krebs
cycle
FADH2
O2
CO2
ATP
Electron
transport
chain
ATP
H2O
Mitochondria
Mitochondria produce the most ATP in
eukaryotic cells
Krebs cycle and electron transport chain
occur in the mitochondria (glycolysis
occurs in the cell’s cytoplasm)
Figure 6.3
Mitochondrion Anatomy
Outer
membrane
Inner
membrane
Cristae
Cellular Respiration:
Glycolysis
+ are reduced to
Two molecules
Occurs
in the cell’s
of NAD
cytoplasm
two molecules of NADH
ATP “activates the glucose molecule,
which
Net
gain:
splits into two three-carbon
•molecules
2 molecules of pyruvate
• 2 molecules of NADH
•Two
2 molecules
three-carbon
of ATP
molecules are
converted into two molecules of pyruvate
Cellular Respiration:
Oxidation of Pyruvate
Two molecules
Occurs
in the mitochondrial
of NAD+ are reduced
matrix to
two molecules of NADH
A molecule of CO2 is removed from each
molecule
Net
gain: of pyruvate
• 2 molecules of acetyl CoA
•The
2 molecules
remaining of
two-carbon
NADH
molecules are
an acetyl groups
Each acetyl group is added to a
coenzyme A to form two molecules of
acetyl CoA
Cellular Respiration:
Krebs Cycle
Net gain:
Occurs
Remaining
in the
reactions
mitochondrial
rearrange
matrix
and
•oxidize
4 molecules
the citric
of acid
CO2 molecules to reform
Turns
•the
6 original
molecules
twice,four-carbon
once
of NADH
for each
compound
molecule of
•acetyl
2 molecule
CoA of FADH2
•Per
2 molecules
molecule ofofacetyl
ATP CoA:
•Each
Twoacetyl
molecules
CoA releases
of CO2 are
itsremoved
coenzyme
•and
Three
combines
molecules
with of
a four-carbon
NAD+ are reduced
compound
to three molecules
to form two
of molecules
NADH
of citric
•acid
One molecule of FAD is reduced to
FADH2
Figure 6.7
Cellular Respiration:
Electron Transport Chain
Occurs on the inner membrane of the
mitochondria
NAD+
NADH
FADH2
1/2 O2 + 2 H+
FAD
H+
H+
2e-
H2O
H+
2e-
Uses the energy in electrons carried by
NADH and FADH2 to generate ATP
H+
H+
H+
Net gain:
• 34 molecules of ATP
Outer membrane
Inner membrane
ATP
synthase
H+
ADP + P
MATRIX
ATP
INTERMEMBRANE
COMPARTMENT
Cellular Respiration:
Theoretical Yield of ATP
Ten NADH . . . . . . . . . . . . . . . . . . . . . 30 ATP
Two FADH2 . . . . . . . . . . . . . . . . . . . . . 4 ATP
Glycolysis/Krebs cycle . . . . . . . . . . . 4 ATP
Active transport of two NADH . . . . -2 ATP
———
Theoretical yield of ATP . . . . . . . . . 36 ATP
Other Organic Molecules Provide Energy
Starch – broken down into glucose
molecules that go directly into glycolysis
Protein – broken down into molecules
that enter as pyruvate, acetyl CoA, or
intermediates in the Krebs cycle
Lipids – glycerol is converted into
pyruvate; fatty acids are broken down
into two-carbon molecules of acetyl CoA
Fermentation
Includes glycolysis, but lacks the Krebs
cycle and the electron transport chain
Keeps glycolysis going by generating
NAD+ through the reduction of an organic
compound by NADH
Figure 6.10
Alcohol fermentation
Pyruvate is converted to a two-carbon
ethanol molecule
CO2 is released
Glycolysis
Glucose
Net gain:
• 2 ATP
• 2 CO2
• 2 ethanol
2
ATP
2 NAD+
2 Pyruvate
2
NADH
2
Ethanol
2
CO2
Figure 6.10
Lactic Acid Fermentation
Pyruvate is converted to a three-carbon
lactic acid molecule
Net gain:
• 2 ATP
• 2 lactic acid
Glycolysis
2
Glucose
ATP
2 NAD+
2 Pyruvate
2
NADH
2
Lactic acid