Cell Energy ATP

1
Chapter 10

• Cell Energy- ATP
• Photosynthesis and Cellular Respiration

2
Cool Fires Attract Mates and Meals

• Fireflies use light, instead of chemical signals,
  to send signals to potential mates
• Females can also use light flashes to attract
  males of other firefly species as meals, not
  mates

3

• The light comes from a set of chemical reactions,
  the luciferin-luciferase system

• Fireflies make light energy from chemical energy
• Life is dependent on energy conversions

4
ENERGY AND THE CELL

• Living cells are compartmentalized by membranes
• Membranes are sites where chemical reactions can
  occur in an orderly manner
• Living cells process energy by means of
  enzyme-controlled chemical reactions

5
Energy is the capacity to perform work

• Energy is defined as the capacity to do work
• All organisms require energy to stay alive
• Energy makes change possible

6
Chemical reactions either store or release
energy

• Cells carry out thousands of chemical reactions
• The sum of these reactions constitutes cellular
  metabolism

7
ATP shuttles chemical energy within the cell

• In cellular respiration, some energy is stored in
  ATP molecules
• ATP powers nearly all forms of cellular work
• ATP molecules are the key to energy coupling

8

• When the bond joining a phosphate group to the
  rest of an ATP molecule is broken by hydrolysis,
  the reaction supplies energy for cellular work

Adenine
Phosphategroups
Hydrolysis
Energy
Ribose
Adenosine triphosphate
Adenosine diphosphate(ADP)
9

• How ATP powers cellular work

Reactants
Products
Potential energy of molecules
Work
Protein
10

• The ATP cycle

Hydrolysis
Dehydration synthesis
Energy from exergonic reactions
Energy for endergonic reactions
11
Life in the Sun

• Light is central to the life of a plant
• Photosynthesis is the most important chemical
  process on Earth
• It provides food for virtually all organisms
• Plant cells convert light into chemical signals
  that affect a plants life cycle

12

• Light can influence the architecture of a plant

• Plants that get adequate light are often bushy,
  with deep green leaves
• Without enough light, plants become tall and
  spindly with small pale leaves
• Too much sunlight can damage a plant
• Chloroplasts and carotenoids help to prevent
  such damage

13
AN OVERVIEW OF PHOTOSYNTHESIS

• Photosynthesis is the process by which
  autotrophic organisms use light energy to make
  sugar and oxygen gas from carbon dioxide and
  water

Carbondioxide
Water
Glucose
Oxygengas
PHOTOSYNTHESIS
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Autotrophs are the producers of the biosphere

• Plants, some protists, and some bacteria are
  photosynthetic autotrophs
• They are the ultimate producers of food consumed
  by virtually all organisms

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On land, plants such as oak trees and cacti are
the predominant producers
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In aquatic environments, algae and photosynthetic
bacteria are the main food producers
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Photosynthesis occurs in chloroplasts

• In most plants, photosynthesis occurs primarily
  in the leaves, in the chloroplasts
• A chloroplast contains
• stroma, a fluid
• grana, stacks of thylakoids
• The thylakoids contain chlorophyll
• Chlorophyll is the green pigment that captures
  light for photosynthesis

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• The location and structure of chloroplasts

Chloroplast
LEAF CROSS SECTION
MESOPHYLL CELL
LEAF
Mesophyll
Intermembrane space
CHLOROPLAST
Outer membrane
Granum
Innermembrane
Stroma
Grana
Thylakoidcompartment
Stroma
Thylakoid
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Plants produce O2 gas by splitting water

• The O2 liberated by photosynthesis is made from
  the oxygen in water

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Overview Photosynthesis occurs in two stages
linked by ATP and NADPH

• The complete process of photosynthesis consists
  of two linked sets of reactions
• the light reactions and the Calvin cycle
• The light reactions convert light energy to
  chemical energy and produce O2
• The Calvin cycle assembles sugar molecules from
  CO2 using the energy-carrying products of the
  light reactions

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• An overview of photosynthesis

H2O
CO2
Chloroplast
Light
NADP
ADP
P
LIGHTREACTIONS(in grana)
CALVINCYCLE(in stroma)
ATP
Electrons
NADPH
O2
Sugar
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THE LIGHT REACTIONS CONVERTING SOLAR ENERGY TO
CHEMICAL ENERGY

• Certain wavelengths of visible light drive the
  light reactions of photosynthesis

Gammarays
Micro-waves
Radio waves
X-rays
UV
Infrared
Visible light
Wavelength (nm)
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Reflectedlight
Light
Chloroplast
Absorbedlight
Transmittedlight
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Photosystems capture solar power

• Each of the many light-harvesting photosystems
  consists of
• an antenna of chlorophyll and other pigment
  molecules that absorb light
• a primary electron acceptor that receives excited
  electrons from the reaction-center chlorophyll

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Primaryelectron acceptor
PHOTOSYSTEM
Photon
Reaction center
Pigmentmoleculesof antenna
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• Fluorescence of isolated chlorophyll in solution

Heat
Photon(fluorescence)
Photon
Chlorophyllmolecule
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• Excitation of chlorophyll in a chloroplast

Primaryelectron acceptor
Othercompounds
Photon
Chlorophyllmolecule
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In the light reactions, electron transport chains
generate ATP, NADPH, and O2

• Two connected photosystems collect photons of
  light and transfer the energy to chlorophyll
  electrons
• The excited electrons are passed from the primary
  electron acceptor to electron transport chains
• Their energy ends up in ATP and NADPH

29

• Photosystem II regains electrons by splitting
  water, leaving O2 gas as a by-product

Primaryelectron acceptor
Electron transport
Primaryelectron acceptor
Electron transport chain
Photons
Energy forsynthesis of
PHOTOSYSTEM I
PHOTOSYSTEM II
by chemiosmosis
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• The production of ATP by chemiosmosis in
  photosynthesis

Thylakoidcompartment(high H)
Light
Light
Thylakoidmembrane
Antennamolecules
Stroma(low H)
ELECTRON TRANSPORT CHAIN
PHOTOSYSTEM II
PHOTOSYSTEM I
ATP SYNTHASE
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THE CALVIN CYCLE CONVERTING CO2 TO SUGARS
ATP and NADPH power sugar synthesis in
the Calvin cycle

• The Calvin cycle occurs in the chloroplasts
  stroma
• This is where carbon fixation takes place and
  sugar is manufactured

CALVINCYCLE
OUTPUT
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• Details of the Calvin cycle

INPUT
3
In a reaction catalyzed by rubisco, 3 molecules
of CO2 are fixed.
CO2
Step Carbon fixation.
1
1
3
P
P
P
6
RuBP
3-PGA
6
ATP
3 ADP
Step Energy consumption and redox.
2
6 ADP
P
CALVINCYCLE
3
ATP
2
6
NADPH
4
6 NADP
Step Release of one molecule of G3P.
3
6
P
5
P
G3P
G3P
3
Step Regeneration of RuBP.
4
Glucoseand other compounds
OUTPUT
1
P
G3P
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PHOTOSYNTHESIS REVIEWED AND EXTENDED
Review Photosynthesis uses light energy to make
food molecules
Chloroplast
Light

• A summary of the chemical processes of
  photo-synthesis

Photosystem IIElectron transport chains
Photosystem I
CALVIN CYCLE
Stroma
Electrons
Cellular respiration
Cellulose
Starch
Other organic compounds
LIGHT REACTIONS
CALVIN CYCLE
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• Many plants make more sugar than they need

• The excess is stored in roots, tuber, and fruits
• These are a major source of food for animals

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STAGES OF CELLULAR RESPIRATION AND FERMENTATION
Overview Respiration occurs in three main stages

• Cellular respiration oxidizes sugar and produces
  ATP in three main stages
• Glycolysis occurs in the cytoplasm
• The Krebs cycle and the electron transport chain
  occur in the mitochondria

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• An overview of cellular respiration

High-energy electrons carried by NADH
GLYCOLYSIS
ELECTRONTRANSPORT CHAINAND CHEMIOSMOSIS
KREBSCYCLE
Glucose
Pyruvicacid
Cytoplasmicfluid
Mitochondrion
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Glycolysis harvests chemical energy by oxidizing
glucose to pyruvic acid
Glucose
Pyruvicacid
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The Krebs cycle completes the oxidation of
organic fuel
Acetyl CoA

• The Krebs cycle is a series of reactions in which
  enzymes strip away electrons and H from each
  acetyl group

2
KREBSCYCLE
CO2
39
2 carbons enter cycle
Oxaloaceticacid
1
Citric acid
CO2 leaves cycle
5
KREBSCYCLE
2
Malicacid
4
Alpha-ketoglutaric acid
3
CO2 leaves cycle
Succinicacid
Step Acetyl CoA stokesthe furnace
Steps and NADH, ATP, and CO2 are
generatedduring redox reactions.
Steps and Redox reactions generate
FADH2and NADH.
1
2
3
4
5
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• Chemiosmosis in the mitochondrion

Proteincomplex
Intermembranespace
Electroncarrier
Innermitochondrialmembrane
Electronflow
Mitochondrialmatrix
ELECTRON TRANSPORT CHAIN
ATP SYNTHASE
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ConnectionCertain Poisons can interrupt the
chain
Rotenone
Oligomycin
Cyanide,carbon monoxide
ELECTRON TRANSPORT CHAIN
ATP SYNTHASE
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For each glucose molecule that enters cellular
respiration, chemiosmosis produces up to 38 ATP
molecules
Cytoplasmic fluid
Mitochondrion
Electron shuttleacrossmembranes
KREBSCYCLE
GLYCOLYSIS
2AcetylCoA
KREBSCYCLE
ELECTRONTRANSPORT CHAINAND CHEMIOSMOSIS
2Pyruvicacid
Glucose
by substrate-levelphosphorylation
used for shuttling electronsfrom NADH made in
glycolysis
by substrate-levelphosphorylation
by chemiosmoticphosphorylation
Maximum per glucose
43
Fermentation is an anaerobic alternative to
aerobic respiration

• Under anaerobic conditions, many kinds of cells
  can use glycolysis alone to produce small amounts
  of ATP
• But a cell must have a way of replenishing NAD

44

• In alcoholic fermentation, pyruvic acid is
  converted to CO2 and ethanol

• This recycles NAD to keep glycolysis working

released
GLYCOLYSIS
2 Pyruvicacid
2 Ethanol
Glucose
45

• In lactic acid fermentation, pyruvic acid is
  converted to lactic acid

• As in alcoholic fermentation, NAD is recycled
• Lactic acid fermentation is used to make cheese
  and yogurt

GLYCOLYSIS
2 Pyruvicacid
2 Lactic acid
Glucose
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Food molecules provide raw materials for
biosynthesis

• In addition to energy, cells need raw materials
  for growth and repair
• Some are obtained directly from food
• Others are made from intermediates in glycolysis
  and the Krebs cycle
• Biosynthesis consumes ATP

47

• Biosynthesis of macromolecules from intermediates
  in cellular respiration

ATP needed todrive biosynthesis
GLUCOSE SYNTHESIS
KREBSCYCLE
AcetylCoA
Pyruvicacid
G3P
Glucose
Aminogroups
Amino acids
Fatty acids
Glycerol
Sugars
Polyscaccharides
Fats
Proteins
Cells, tissues, organisms
48
The fuel for respiration ultimately comes from
photosynthesis

• All organisms have the ability to harvest energy
  from organic molecules
• Plants, but not animals, can also make these
  molecules from inorganic sources by the process
  of photosynthesis