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4
ATP: What’s the Big Deal?
• Life = endergonic• Organisms …1. Require energy input• Plants—sunlight • Animals—food
2. Use this energy to maintain life• Build & repair• Reproduce
• Evidence?• Without sunlight (plants) or food
(animals), organisms die
P
R
EA
ΔGG
Time
Life
5
ATP: What’s the Big Deal?
• Where does ATP fit into this? Analogy: Just as …• Vehicles run on Gasoline• Household appliances run on Electricity• Cells?
• How would this look on energy graph?• Conclusion:
Life
P
R
EA
ΔGG
Time
ATP ATP = general form of energy that cells use to maintain endergonic “lifestyle”
run on ATP
6
ATP: What’s the Big Deal?
• Another analogy:• ATP = energy “currency” of
cell
• What does this mean?• $, Electricity, ATP = all easily
convertible• $ = wealth• Electricity = energy• ATP = energy for cells
• Food/Sunlight ATP Growth/Reproduction
• Work $ Make Purchases• Coal/Oil/Gas Electricity Run Machines
Energy FlowConvert … To … To …
7
ATP: What’s the Big Deal?
• So … what’s the big deal?• ATP is fundamental to life• All cells run on ATP• Without ATP, there is no
life!
• OK, so ATP is important• What, exactly, is ATP?
9
ATP: What is ATP?
• What does ATP stand for?
• Biological molecule class:• Monomer:
• What is a Nucleotide?• Phosphate• 5-Carbon Sugar• Nitrogenous Base
• What is ATP?
NucleotideNucleic Acid
Adenosine Triphosphate
3 parts
Nucleotide
11
ATP: How Do Cells “Run” on ATP?• We know …
• Life = endergonic• ATP supplies energy to “run” endergonic “lifestyle”
• If ATP supplies energy, then ATP molecule must …• Contain energy• Transfer energy to endergonic reactions
• 3 questions:1. Where is energy in ATP molecule?2. How is energy in ATP released?3. How is energy transferred to endergonic reactions to
make them “run”?
Life
P
R
EA
ΔGG
Time
ATP
12
ATP: How Do Cells “Run” on ATP?
Energy!
1. Where is energy in ATP molecule?• In bonds between phosphates
• How is energy stored here? (Hint: look at the 2 Pi below)• What do you notice?• Phosphates negative• How does this explain how energy stored?• 3 repel each other• To force 3 close together requires energy• Covalent bond between holding
these ions together contains this energy
PP
P P
( )P
13
ATP: How Do Cells “Run” on ATP?2. How is energy in ATP released?• What do you notice?• Bonds between broken by hydrolysis• Energy released
ATP hydrolysis ADP + Pi + energy
PP
14
ATP: How Do Cells “Run” on ATP?
• Can represent on energy graph …• Graph:• Include: axes labels, Reactants, Products,
EA, ΔG
• Reaction = endergonic / exergonic• ΔG = + / –• Reaction = spontaneous / not
spontaneous• On graph, what represents energy ATP
supplies to endergonic reaction to make it run?
ATP hydrolysis ADP + Pi + energy
ADP + Pi
ATPEA
ΔGG
Time
ΔG
15
ATP: How Do Cells “Run” on ATP?• We know: • Can update our graph …
P
R
EA
ΔGG
Time
ADP + Pi
ATP
Life
P
R
EA
ΔGG
Time
ATP
ATP hydrolysis ADP + Pi + energy
Life
↓ energy
↑ energy
Energy transferred from ATP to R
16
ATP: How Do Cells “Run” on ATP?
3. How is energy transferred to endergonic reactions to make them “run”?
• Use energy graphs …
2
3
4
5
1
G
Time
R
P+
• Couple Endergonic Reaction with ATP hydrolysis (= Exergonic)
• Overall reaction = Exergonic
ATP
ADP, Pi
Time
R, ATP P,
ADP, Pi
Time
P
R
EA
ΔGG
Time
ADP + Pi
ATP
Endergonic Reaction ATP Hydrolysis Coupled Reaction
17
ATP: How Do Cells “Run” on ATP?• Example ATP making
endergonic reaction “run”
• Label concentrations• What process is
occurring?• How can you tell?
• Na+ & K+ moving up their gradients
• ATP supplying energy
↑[Na+]
↓[Na+]
↓[K+]
↑[K+]Active Transport
• What is actually happening? How is energy from ATP moving ions up their gradients?
Inside Cell
Outside Cell
↓ energy↑ energy
Transport protein
18
ATP: How Do Cells “Run” on ATP?• What do you notice?• Na+ moves out, up gradient• K+ moves in, up gradient• ATP transfers Pi to transport
protein• Transport protein changes shape
• What can you conclude?• Energy in ATP transferred with Pi
• Energy causes protein to change shape• Shape change allows ions to move
up their gradients↑[Na+], ↓[K+]
↓[Na+], ↑[K+]
Transport Protein
OutsideCell
Membrane
InsideCell
20
ATP: How Do Cells Make ATP?• Average human
• Mass: 62 kg (62.000 g)• Amount of ATP: 51 g (0.08%)• Amount of ATP used per day: 100-150 kg
(100.000-150.000 g), about 2X body mass!
• What do you notice?• You have very little ATP but use a HUGE
amount every day
• How is this possible?• ATP recycled• Reverse reaction occurs also• ADP + Pi ATP
• We know …
ATP hydrolysis ADP + Pi + energy
ADP + Pi
ATPEA
ΔGG
Time
ADP + Pi
ATPEA
ΔGG
Time
21
ATP: How Do Cells Make ATP?• Remember, we said …
• Life = endergonic• Organisms …1. Require energy input
• Plants—sunlight • Animals—food
2. Use this energy to maintain life• Build & repair• Reproduce
• Where does energy to make ATP come from?
• How would this look on the graph?
P
R
EA
ΔGG
Time
Life
Food or Sunlight
Food/ Sunlight
22
ATP: How Do Cells Make ATP?• Consider food
• Burn food• Releases energy• Capture energy to make ATP
• Can represent on energy graph
• Conclusion:• Couple reactions so energy
Released from burning food added to ADP + Pi to synthesize ATP
• Overall reaction = exergonic
+ O2 CO2 + H2OFood (carbs,
fats)Energy
ADP + Pi ATP
+
Coupled Reaction
Time
ADP, Pi, Food,
O2
ATP, CO2, H2O
ATPADP,
Pi
Time
ATP Synthesis
Time
Food,O2
CO2, H2O
Burn Food
G2
3
4
5
1
23
ATP: Overview
• Covered 2 reactions:• ATP ADP + Pi + energy• ADP + Pi + energy ATP
• Both reactions occur in cycle
• Here, emphasis on ATP• Shift focus to surrounding
reactions
ATP ADP + Pi
Energy released to drive endergonic reaction
Energy absorbed from food/sunlight to synthesize ATP
Exergonic
Endergonic
High Energy
Low Energy
24
ATP: What’s the Big Deal?
• Another analogy:• ATP = energy “currency” of
cell
• Food/Sunlight ATP Growth/Reproduction
• Work $ Make Purchases• Coal/Oil/Gas Electricity Run Machines
Energy FlowConvert … To … To …
25
ATP: Overview
• Energy output from catabolic reactions• Energy input to anabolic reactions• ATP connects reactions, shuttling
energy from catabolic to anabolic pathways
CO2, H2O
Food, O2
EA
G
Time
ΔG
P
R
EA
ΔG
Time
Catabolism:Exergonic Reactions
Anabolism:Endergonic Reactions
ADP + Pi
ATP
Food/Sunlight ATP Growth/ReproductionEnergy Flow
26
• If ATP captures & holds energy, why don’t organisms use ATP for energy storage?• What molecules do cells use for energy storage?
• Carbohydrates (polysaccharides)• Lipids (fats)
• Why not use ATP?• Not stable• Only useful for short-term storage (immediate
energy transfer)
• How much ATP do you use per day?• Twice your mass!
ATP: Overview
28
Redox: What is it?• Oxidation/Reduction• How to identify oxidation & reduction?• Oxidation• Loss of electrons• Often: gain of O / loss of H
• Reduction• Gain of electrons• Often: gain of H / loss of O
• How to remember oxidation & reduction?• OIL—Oxidation Is Loss (of electrons)• RIG—Reduction Is Gain (of electrons)
29
Redox: How does it work?• Oxidation & Reduction = coupled reactions
• 1 atom loses an e- (= )• Another atom gains e- (= )
• NaCl = ionic compound• Define:
• But organisms made of covalent compounds• Define:
• Do redox reactions occur in covalent compounds?
oxidationreduction
Na Na+
Cl Cl-
e-
Na is gaining / losing e-
oxidized / reduced
Cl is gaining / losing e-
oxidized / reduced
ionic bond
Atoms gain/lose electrons= Redox Reaction
Atoms share electrons
30
Redox: Does it occur in reactions with covalent compounds?
• Add electrons
• What do you notice?1. Bonds
• Reactants = nonpolar covalent• Products = polar covalent
2. Redox• C, H losing electrons = oxidation• O gaining electrons = reduction
• Conclusion:
Covalent compounds undergo redox reactions
nonpolar covalent bonds polar covalent bondsO gaining e- = reduction
H losing e- = oxidation
C losing e- = oxidation
Reactants Products
methane
31
Redox: Is redox related to energy?• Burning methane releases energy• Energy release related to redox?
• What do you notice?• Nonpolar covalent bond = high energy
e-
• Polar covalent bond = low energy e-
• As e- transition from nonpolar to polar covalent bond• e- lose energy• Energy released• Energy lost from system
• How much energy released?
• Conclusion:
energy
C H C OTime
G
nonpolar covalent bond polar covalent bondhigh energy e- low energy e-
• = electron
Energy changes in reactions are related to redox
CH4 + 2O2 CO2 + 2H2O + energy
covalent bond
energy in bond
ΔG
ΔG
33
Electron Carriers: What are they?
• Compounds that transfer (“carry”) e- from 1 compound to another compound
• Ex. NAD+ (nicotinamide adenine dinucleotide; main electron carrier in cellular respiration)• (Neither full name nor structure
required … whew!)
34
Electron Carriers: How do they carry electrons?Equation: NAD+ NADH• How are electrons carried? Look at how
get from NAD+ to NADH• Add H, but H (or H2) not present, only H+;
Result?• But want NADH, not NADH2+; How to fix?• Add 2 e-; Result?• Overall reaction?
• Is NAD+ being oxidized or reduced? How do you know?• Gaining 2 e-/Gaining H, so reduced
• Which compound carrying electrons, NAD+ or NADH ?
• Another way to look at this reaction
NAD+ + H+ NADH2+ NADH + 2e- ( )
Summary: NAD+ + H+ + 2e- NADH
NAD+ NADH
H+ + 2 e-
H+ + 2 e-
oxidation
reduction
35
Electron Carriers: How do they carry electrons?
• Let’s look at actual compound• Relevant portions shaded
• What do you notice when NAD+ NADH?• Added H+ & 2 e-
• New covalent bond (attached to H)
• Where are electrons “carried”? • In new covalent bond• (Remember: 1 covalent bond = 2 e-)
• Are these low or high energy electrons? How can you tell?
• High energy because 2 e- in nonpolar covalent bond
• Remember: vertices = C, so C—H bond
new covalent bond
Summary: NAD+ + H+ + 2e- NADH