Topic 7: Energy (Part I)

where and why does ATP form?

forms in the mitochondria as part of the reactions of cellular respiration

cellular respiration

the collection of metabolic reactions that break down food molecules to produce energy in the form of ATP

aerobic respiration

in eukaryotes and many prokaryotes, a form of cellular respiration where oxygen is a reactant in ATP producing process

anaerobic respiration 

in some prokaryotes, a molecule other than oxygen (i.e. sulfate and nitrate) is used in the ATP producing process n

what are major steps in the carbon cycle?

cellular respiration and photosynthesis

what does photosynthesis produce?

• most food molecules broken down in cellular respiration

• oxygen used in aerobic respiration

Where does photosynthesis store energy from?

stores energy from sunlight in electron-rich fuel molecules (i.e. sugars) 

What does cellular respiration do?

moves electrons from a fuel to other molecules (i.e. oxygen) that act as electron acceptors 

oxidation

the removal of electrons from a substance

oxidized

describing the substance from which electrons are removed (electron donor)

reduction

the addition of electrons of a substance

reduced

describing the substance that receives the electrons (the electron acceptor 

redox reactions

reactions that remove electrons from a donor molecule and simultaneously add them to an acceptor molecule

What do electrons release in redox reactions? what can it be used for?

• release some of their energy 

• free energy is available for cellular work (ATP synthesis) 

chemical equation for cellular respiration

C₆H₁₂O₆ + 6O₂ + 32ADP + 32P → 6H₂O + 6CO₂ + 32ATP

dehydrogenase enzyme

facilitate the transfer of electrons from a fuel molecule to a molecule that acts as an electron carrier

nicotinamide adenine dinucleotide (NAD+)

most common electron carrier; oxidized form (reduced form = NADH) 

What does dehydrogenase transfer to NAD+?

2 electrons and 1 proton

what are the three stages of cellular respiration?

1) glycolysis

2) pyruvate oxidation 

3) oxidative phosphorylation 

glycolysis

• enzymes break a 6-carbon molecule of glucose into 2 3-carbon molecules of pyruvate 

• some ATP is synthesized by substrate level phosphorylation

substrate level phosphorylation 

an enzyme catalyzed reaction that transfers a phosphate group from a substrate to ADP

pyruvate oxidation

• enzymes convert the 3-carbon pyruvates to 2-carbon acetyl groups which enter the citric acid cycle and is completely oxidized into CO2

• some ATP is synthesized in the citric acid cycle 

oxidative phosphorylation

• high-energy electrons are delivered to oxygen by a sequence of electron carriers in the electron transfer system

• free energy released by the electron flow creates a H+ gradient by chemiosmosis

• uses ATP synthase

ATP synthase

enzyme that uses the H+ gradient as the energy source to make ATP