Download ATP, Photosynthesis and Respiration

Energy
Functions of ATP
• Chemical work – synthesizing compounds
• Transport work – moving substances across
the plasma membrane
• Mechanical work – moving cell structures and
cells
•Energy coupling: use of
an exergonic process to
drive and endergonic
process
•ATP mediates most
energy coupling in cells
ATP
• Consist of
– a sugar
called ribose
– N containing
Adenine
– Three
phosphate
groups

Unstable w/3 PO4• All negative charge-repel each other


ADP is more stable
A change from a less stable molecule
to a more stable molecule always
releases energy.
The structure and hydrolysis of ATP
All are negatively charged
– crowded and repel,
creating instability
When bonds are broken
from ATP to ADP
(hydrolysis),
7.3 kcal/mol of energy
is released (exergonic)
Phosphorylation
Recipient of phosphate
group when ATP loses it.
 Done by Kinases

The ATP cycle
ATP is a renewable resource that can be regenerated…
FAST – working muscle cell recycles its
entire ATP pool once each minute;
-Turnover represents 10 million molecules
of
ATP generated per second in a cell.
• The energy can then
be used to drive other
reactions
– ATP “carries” Energy
• Photosynthesis is
the process by
which plants and
other organisms
use sunlight, CO2
& H20 to produce
high energy
carbohydrates
such as sugars and
starches.
• Prokaryotesphotosynthetic
capability is
present within five
major groups of
bacteria.
Where
Photosynth
esis Occurs
The Internal Structure of a Leaf
Section 23-4
CO2 enters
through the
stomata
Epidermis
Chloroplasts
Stomata
Guard
cells
• Chloroplasts are only found in photosynthetic,
eukaryotic cells. Chloroplasts are capable of
harnessing energy from the sun's rays of light.
•Using this
energy from
the sunlight,
chloroplasts
are able to
form ATP as
well as
synthesizing
sugars from
water and
carbon dioxide.
Things to know about Chloroplasts
• have a double membrane
• have their own DNA (carries the
info to make enzymes)
• have their own ribosomes (more like the
ribosomes of prokaryotes) -used to
synthesize proteins
• make their own enzymes required for
photosynthesis
• require CO2 and H2Oproduce C6H12O6
• contain chlorophyll (green chemical "traps"
sunlight energy)
• The chloroplast is made up of 3 types of membrane:
1.A smooth outer membrane which is freely permeable
to molecules.
2.A smooth inner membrane which contains many
transporters
3.A system of thylakoid membranes
Chloroplast
• Organelle where photosynthesis takes place.
Stroma
Outer Membrane
Inner Membrane
Thylakoid
Granum
Thylakoid
Thylakoid Membrane
Granum
Thylakoid Space
Light and Pigments
In addition to water and carbon dioxide,
photosynthesis requires light and
CHLOROPHYLL and Accessory Pigments
Light – radiant energy from the sun,
travels in waves
(light energy is measured in units called photons)
amplitude
Crest – high
point
Baseline
amplitude
One wavelength
Trough – low point
• Amplitude – height of wave; distance
between crest and/or trough (must use a
reference point from which to start…)
• Wavelength – distance between where
waves begin to repeat themselves
• Frequency – how many waves pass a
certain point in a given amount of time
(high frequency vs. low frequency)
Sunlight is a mixture of many
different wavelengths…
ROYGBIV
• Colors in visible light spectrum
• Each of these has a different wavelength…
Chlorophyll A and B
• Absorb red, blue,
and violet range.
b
a
Chlorophyll Light Absorption
Photosynthetic Pigments
-absorb light and use it to provide energy to carry out
photosynthesis
• Plants absorb certain wavelengths of light
• 2 major groups of pigments.
• Chlorophylls (green) and carotenoids (yellow,
orange and red.)
Pigments
• Substances in organisms that can absorb light (remember –
light must be absorbed before it can be converted and used
by living systems…)
• The color that you see is the one being REFLECTED
• CHLOROPHYLL is the major photosynthetic pigment in
plants
• 2 types: chlorophyll a – directly involved in
transformation of photons to
chemical energy
chlorophyll b – helps trap other wavelengths
and transfers it to chlorophyll a
Location and structure of chlorophyll molecules in plants
The pigment molecules have a
large head section that is
exposed to light in the surface
of the membrane; the
hydrocarbon tail anchors the
pigment molecules into the lipid
bilayer.
Double bonds
are the source
of the e- that
flow through
the ETC
Accessory Pigments
• Other pigments that trap other wavelengths -found in chromoplasts
• Ex. Carotenoids
* xanthophyll – yellows
* beta carotene – oranges
• These are masked by presence of chlorophylls,
except in autumn (when leaf cells stop
synthesizing chlorophyll) – “fall colors”
• Also is very obvious in “ripe” fruits, veggies
Ex. Apple, tomato
• Chlorophyll B, the carotenoids, and the
phycobilins are known as antenna pigments.
• They capture light and pass the enrgy along
to chlorophyll A.
• Chlorophyll A directly participates in the
light reaction of photosynthesis.
Photosystems
• Light-harvesting complexes in the thylakoid
membranes. (few 100 in each)
• Structure:
– Reaction Center- contains chlorophyll A and a region
containing several 100 antenna pigments.
• Two Types:
– PS I and PS II
– PS II acts BEFORE PS I……..go figure...
PSII
• 680nm range
• Also referred to as P680.
PS I
• 700nm range
• Also referred to as P700
Now that you know all of
that……let’s actually look at
the process of photosynthesis
Photosynthesis: Quick Overview
STAGE 1
Photosynthesis: Quick Overview
STAGE 1
Photosynthesis: Quick Overview
STAGE 1
STAGE 2
Light Independent
Reaction

Light Dependent
Reaction

The Process of Photosynthesis does NOT Happen all at
Once; rather it occurs in TWO STAGES:
STAGE 1: LIGHT DEPENDENT REACTIONS.
– PS I and PS II capture energy from sunlight. Water is
Split into Hydrogen Ions, Electrons, and Oxygen
(O2). The O2 Diffuses out of the Chloroplasts
(Byproduct).
– The Light Energy is Converted to Chemical Energy,
which is Temporarily Stored in ATP and NADPH.
•Two possible routs for the e- flow:
•Cyclic photophosphorylation
•noncyclic
Steps of Light Dependent Reaction
(Noncyclic Photophosphorylation)
Overview:
–E- enter two electron transport
chains
–ATP is formed
–NADPH (Nicotinamide
dinucleotide phosphate) is
formed
Steps of Light Dependent Reaction
(Noncyclic Photophosphorylation)
1.
2.
3.
4.
5.
6.
•
•
7.
8.
9.
10.
11.
12.
13.
PSII absorbs energy.
e- from double bonds in the head of ChloroA become energized and move to a
higher energy level. They are captured by a primary electron acceptor.
Photolysis: H2O gets split apart into 2 e- , 2 H+, and one oxygen atom.. The ereplace those lost by ChloroA.
2 oxygen molecules combine and is released into the air.
H+ are released into the inner thylakoid space, which creates a higher [ H+ ]
inside the thylokoid.
e- from ChloroA are passes along a ETC consisting of plastoquinone (PQ)--complex of 2 cytochromes and several other proteins.
This flow is exergonic and provided energy to produce ATP by chemiosmosis.
(photophosphorylation)
The ATP is used to power the Light Independent Reaction (Calvin Cycle)….this is a coupled
reaction!
The e- end up at PS I.
PS I absorbs energy.
e- from double bonds in the head of ChloroA become energized and move to a
higher energy level. They are captured by a primary electron acceptor.
E- that are lost are replaced by the e- from PSII (step7).
e- from ChloroA are passes along a ETC – consisting of ferrodoxin.
NADPH is produced.
NADP in the stroma pick up 2 H+ and form NADPH and enter the calvin cycle.
Figure 10.11 How a photosystem harvests light
Chlorophyll a
The light reactions and chemiosmosis: organization of the thylakoid membrane
The production of ATP using the energy of
sunlight is called photophosphorylation.
H+
H+
H+
H+
H+ H+ H+
H+
+
H+ H
H+
Chemiosmosis
“Chemiosmotic Theory”
-Peter Mitchell -1961
• Energy coupling
mechanism.
– Uses potential
energy stored
in the form of
a proton
gradient to
phosphorylate
ADP to
produce ATP.
ATP synthase-The Movie
Chemiosmosis
Proton gradient
ALSO creates a pH
difference as well as
a charge difference.
Protons can not
diffuse through the
membrane.
SO they must
flow through the
ATP synthase
protein channel.
90% of all ATP is
produced this way.
Photosynthesis:
Light Dependent Reaction
Clip
Figure 10.13 A mechanical analogy for the light reactions
A. Photosystem II -Light is absorbed by pigment. Energy is transferred to e-, which
Figure 8-10 Light-Dependent
go into ETC. Hydrolysis breaks water up into e-, H+, and O2
Reactions
B. ETC Section
moves H+
8-3 ions from stroma into inner thylakoid.
C. Photosystem I -light is absorbed by pigments, energy goes to e-, NADPH is formed
D. Hydrogen movement makes inside positively charged.
E. As H+ diffuses through ATP synthase, ADP is made into ATP.
Photosystem II
Hydrogen
Ion Movement
Chloroplast
ATP synthase
Inner
Thylakoid
Space
Thylakoid
Membrane
Stroma
Go to
Section:
Electron
Transport Chain
Photosystem I
ATP Formation
Cyclic Photophosphorylation
•Periodically the chloroplasts runs low on ATP.
•Does this to replenish ATP levels.
•e- travel from the P680 ETC to P700 then to
a primary eacceptor,
then back to
the
cytochrome
complex in
the P680
ETC.
• No NADPH is
produced.
• No O2 is
released.
STAGE 2: Dark Reaction /Light Independent
reaction/Calvin-Benson Cycle).
•The ATP and NADPH created in the light reaction
is used to power the formation of Organic
Compounds (Sugars), using CO2.
•This is a light Independent reaction. It can
happen during the daylight, it just does NOT need
to light be completed.
•Occurs in the stroma.
•Cyclical pathway where carbon enters as CO2 and
exits as PGAL (phosphoglyceraldehyde.)
•Carbon is fixed into PGAL.
•Called carbon fixation.
•This is a reduction reaction (carbon is GAINING
hydrogen)
•Must repeat 6 times.
C3 plants
The Calvin cycle
6
CO2 attaches to
a 5-C sugarRuBP.Ribulose
biphosphate.
This forms a 6C molecule
(PGA)
The Calvin cycle
6
6-C molecule
breaks (PGA)
down into 2 3-C
molecules (3PGAL-3phosphoglycera
te)
12
Catalyzes by
the enzyme
Rubisco.
12
12
PGAL
2
PGAL
1
PGA
The Calvin cycle
6
PGAL
converted to
RuBP
12
12
12
PGAL
Summary:
H+
6CO2 + 18 ATP + 12 NADPH +

18ADP + 18 Pi + 12NADP+ + 1 Glucose
2
PGAL
1
PGA
Factors affecting Photosynthesis
• Amount of water available – too
little, stop photosynthesis
• Temperature – best between Oo
Celsius and 35o Celsius (too high,
damage enzymes; too low, stop
photosynthesis)
• Intensity of light – up to a point,
increasing light intensity increases rate
• C-3
Other Pathways
– Calvin cycle occurs in all photosynthetic cells-both palisade and
mesophyll layers.
• C-4
– Called C4 because the CO2 is first incorporated into a 4-carbon
compound.
– Light reaction occurs ONLY in the mesophyll cells and the calvin
cycle occurs in the bundle-sheath cells.
• CAM
• CAM plants live in very dry condition and, unlike other
plants, open their stomata to fix CO2 only at night.
Figure 10.18 C4 leaf anatomy and the C4 pathway
Cellular
Respiration
Objectives
• Describe the role of ATP in coupling the cell's
anabolic and catabolic processes.
• Explain how chemiosmosis functions in
bioenergetics.
• How are organic molecules broken down by the
catabolic pathways of cellular respiration?
• Explain the role of oxygen in energy-yielding
pathways of cellular respiration.
• Explain how cells generate ATP in the absence of
oxygen.
Cellular Respiration
• the process that occurs
in cells in which cells
break down sugar for
ENERGY!
• Occurs in cytoplasm
and Mitochondria.
Glycolysis
Important points:
• Occurs in Cytoplasm
• First 3 steps are endothermic-Energy of
activation = 2 ATP
• Last 6 steps are exothermic; producing 4
ATPs.
• 4-2= 2 ATP (net yield)
• Releases less then 25% of energy from
glucose.
A closer look at glycolysis
Step 1
Step 2
Step 4
Step 3
Step 5
Step 6
Step 7
Step 5
Step 8
Step 6
Step 9
Step 7
Cellular Respiration
Overview:
• We get our energy from the food we eat.
• The unit for energy is the calorie.
• Plants are producers and make glucose by
the process of photosynthesis.
• Heterotrophs breakdown glucose for
energy.
• There are two important ways a cell can
harvest energy from food: fermentation
and cellular respiration.
30
Step1: Glycolysis
•
•
•
•
Means “Splitting Glucose”
Both pathways start with Glycolysis.
Glycolysis starts with Glucose.
Glucose is broken down into 2
molecules called Pyruvate.
• Happens in the Cytoplasm.
31
Products of
Gylcolysis
32
33
Summary of Glycolysis
• 1. One glucose (6C)
converted into 2 pyruvates
(3C).
• Net yield of 2 ATP for use
by cell.
• CLIP
34
REVIEW
• Glycolysis is the first step of
reactions that break glucose apart
to release the energy it holds in its
C-H bonds.
• Where did this energy come from?
• Glycolysis occurs in the Cytoplasm.
• Glycolysis does not need oxygen!
• Glycolysis occurs in both aerobic
(With oxygen) and anaerobic
(without oxygen) respiration!
In the presence of OXYGEN:
Step 2: Krebs Cycle
Step 3: Electron Transport
• Happens in the Mitochondria
• Starts with Pyruvate.
• Pyruvate moves into the
mitochondria and is broken
down into CO2 , O2 and ATP.
Krebs and ETC take place in a
mitochondrion
Double membrane
Mitochondria Anatomy
Krebs Cycle Overview
(Citric Acid Cycle)
• Occurs in the mitochondrial matrix
• Pyruvate (product of glycolysis) enters the mito.
and combines with coenzyme A (vitamin A) to
form acetyl coenzyme A.
 Yields 1 NADH
• Krebs starts with acetyl coA.
• Cyclical series of enzyme-catalyzed reactions.
• Each turn (cycle) uses 1 pyruvate and yields
– 3 NADH, 1 ATP, 1 FADH
– Byproduct=CO2
NAD and FAD
Coenzymes that carry protons or electrons from
glycolysis & krebs to the ETC
• NAD:
• FAD:
A summary of the Krebs cycle
Electron Transport
• Utilizes a series of proteins called
cytochromes
• Made up of heme group with 4 organic
rings surrounding a single iron atom
(similar to hemoglobin)
• But, cytochromes transfer electrons rather
than oxygen….
• NADH and FADH2 provide sources of
electrons for the ETC
Electron Transport
• The ETC is a proton pump in the inner mito
membrane.
• Its uses the energy released from the
exergonic flow of electrons to pump protons
from the matrix to the inner membrance
space.
• This sets up a proton gradient across the
membrane=chemiosmosis.
Oxidative Phosphorylation and Chemiosmosis
Energy from falling e- (exergonic) is used
to pump H+ across the membrane
(endergonic).
Oxygen is the final eacceptor!!
H+ can’t get through the membrane, so they MUST pass through the channel.
Phosphorlation
• Substrate Level:
– When an enzyme transfers a PO4- from a substrate
DIRECTLY to ADP.
• Oxidatative:
– During Chemiosmosis.
– 90% of all ATP is produced this way in the ETC
– NAD & FAD lose protons (become oxidized) to the
ETC…pumps protons to innermembrane space creating
a gradient. This powers the phosphorlation of ADP
Aerobic Respiration
With
oxygen
Section 9-1
Respiration
Glucose
Glycolysis
Krebs
cycle
Fermentation
(without oxygen)
With out
oxygen
Go to
Section:
Electron
transport
Alcohol or
lactic acid
41
Figure 9.13 Free-energy change during electron transport
Figure 9.15 Chemiosmosis couples the electron transport chain to ATP synthesis
Figure 9.16 Review: how each molecule of glucose yields many ATP molecules during
cellular respiration
Figure 9.19 The catabolism of various food molecules
• In the presence of oxygen: Pyruvate is
converted into carbon dioxide and water in
the Krebs cycle.
• After the Krebs cycle, 36 ATP are created in
the electron transport chain.
42
Section 9-2
Flowchart
Cellular Respiration
Reactants
Glucose
(C6H1206)
+
Oxygen
(02)
Final Products
Glycolysis
Krebs
Cycle
Electron
Transport
Chain
Carbon
Dioxide
(CO2)
+
Water
(H2O)
43
Go to
Section:
Fermentation
• Without oxygen: Pyruvate is converted into
Lactic Acid or Alcohol during
Fermentation.
• Lactic Acid-Muscle cells
• Alcohol- Yeast
44
Anaerobic Respiration
45
Electrons carried in NADH
Electrons
carried in
NADH and
FADH2
Pyruvic acid
Glucose
Glycolysis
Electron
Transport
Chain
Krebs
Cycle
Cytoplasm
Mitochondrion
Electron Transport
Hydrogen Ion Movement
Channel
Mitochondrion
Intermembrane
Space
ATP synthase
Inner
Membrane
Matrix
ATP Production
Lactic Acid Fermentation
Section 9-1
Glucose
Pyruvic acid
Lactic acid
46
Go to
Section:
Section 9-2
Anaerobic:
Fermentation
Reactant
Glucose
(C6H1206)
Products
Glycolysis
Fermentation
Lactic Acid
Or
Alcohol
47
Go to
Section:
48
Respiration Formula
• 6____ + ___
Review Clip
___ and 6___ + 6__ + 36 ATP
49
50
35
Alternative Energy Sources
• From Fats:
– Enzymes cleave the bonds between the glycerol and
the fatty acids, which enter the blood stream.
Enzymes in the liver convert the glycerol into PGAL.
– Enzymes in cells break apart the fatty acids acetylCoA.
– More C-H bonds, so yields more ATP.
Alternative Energy Sources
• From Proteins:
– Cells don’t store protein.
– Enzymes breakdown proteins—into AA units,
then strip of the NH3+ group.
– Carbon backbone either gets converted into fats
or carbohydrates.
– Or, enter krebs cycle.