IB Bio HL: Unit 4B

ATP

Adenosine Triphosphate

Monomer of ATP

modified nucleotide

Organelle that produces ATP

Mitochondria

Aerobic Cellular Respiration

Process of producing ATP

Processes ATP is used for

• active transport

• anabolic reactions

• muscle contractions

• movement of cells or parts within cells

Diagram of ATP

Why is ATP like a spring

• phosphate groups have negative charges and repel each other

• keeping the phosphate groups in close contact, creating bonds, is similar to compressing a spring

How is energy released from ATP

when the 3rd phosphate is broken off

ATP Hydrolysis

• process of releasing energy from ATP

• a water molecule is used to break the bond between the 2nd and 3rd phosphate groups

• an exergenic reaction occurs and energy is released

Products in ATP Hydrolysis

ADP + P

ADP

Adenosine Diphosphate

ADP Phosphorylation

• process of ATP regeneration from ADP

• adding a phosphate group to ADP

• requires energy, making a bond

• removing a water molecule

• an endergenic reaction occurs, storing energy

Where do humans get the energy needed to perform ADP Phosphorylation? Where does the energy ultimately come from?

• from energy from the glucose humans consume in food

  • photosynthesis; therefore, sunlight

Diagram of ATP-ADP cycle

ATP and active transport

• transport of molecules across membranes can be a passive process, but when molecules need to be moved against their concentration gradient, active transport is required

• for this process to occur transport proteins are needed and ATP is used

• ATP binds to the transport protein, releasing the third phosphate, and energy is transferred to the transport protein allowing it to move the molecule across the membrane

ATP and anabolic reactions

• formation of the bonds in these molecules requires energy and the energy comes from ATP

• bonds need to be formed and that requires a source of energy

• the enzymes that catalyse the reactions that form the bonds require ATP to function properly

ATP and movement

• involves the cell moving or the movement of components within the cell

• cell movement will involve the cytoskeleton of protein filaments. ATP is used to grow these filaments by providing the energy to bond fragments of the filaments together

• the growth and contraction of these extensive networks of filaments produce changes in cell structure, which can lead to movement

• when a phagocyte moves to engulf an invading bacterium, it is the movement of the cytoskeleton, using ATP that causes the membrane of the phagocyte to extend around the bacterium, leading to its destruction

Location of Light Reaction

Thylakoids

Location of Calvin Cycle

Stroma

Description of Light Reaction

utilizes photosynthetic pigments to absorb light

Description of Calvin Cycle

uses ATP and NADPH from the light reaction

Inputs and Outputs of Light reaction

• light energy splits H₂O and produces O₂ as a byproduct

• creates ATP and NADPH to be used by Calvin cycle

Inputs and Outputs of Calvin cycle

• carbon fixation of CO₂ from the atmoshpere

• produces sugar

How are the Light reaction and the Calvin cycle linked together

• the light reaction produces the inputs of the Calvin cycle

• happen simultaneously

• producing O₂ is waste, but humans need it

• light reaction charge the ATP and that is needed to make sugars in the Calvin cycle

Diagram of the Light Reaction and Calvin Cycle

Where does O₂ come from in photosynthesis

• it comes from the 12 H₂O by becoming 6 O₂, no change in numbers

• the C in CO₂ actually goes to the glucose

Reduction

• gaining electrons

• the charge is “reduced” because it becomes more negative

Oxidation

loses electrons

OIL RIG

Oxidation Is Losing, Reduction Is Gaining

LEO says GER

Loss of Electrons (oxidation), Gain of Electrons (Reduction)

Photosystems

integral protein complexes located within the phospholipid bilayer

Location of Photosystems in Chloroplasts

the thylakoid membrane

Location of Photosystems in Cyanobacteria

the cell membrane, no chloroplasts in prokaryotes

why can photosystems absorb light

they contain chlorophylls and other accessory pigments that will absorb light

process of photoactivation in photosynthesis

• photons of light strike the pigment molecules within the photosystems

• excites the electrons in the pigments contained in the photosystems

• excited electrons are transferred between the array of pigments within the photosystem

• excited electrons finally reach the reaction center: a special chlorophyll a molecule

• at the reaction center, the excited electrons will be emitted from the photosystem

are photosystems reduced or oxidized after photoactivation

the photosystem has been oxidized

photosystem I vs photosystem II

• PSII comes before PSI

• PSII is 680nm

• PSI is 700nm

most important particle during light reaction

electron

photosystem undergoing photo activation first

photosystem II

where the electron goes after it leaves PSII

• after the electron is emitted from PSII, it is transferred from the reaction center to the first Electron Transport Chain (ETC)

• PSII is now missing an electron: this is very unstable

• electrons are replaced during the process of photolysis

photolysis

• process of using light energy to break water molecules in order to replace missing electrons in PSII

• occurs in the thylakoid space (lumen)

equation of photolysis

2 H₂O → 4H⁺ + O₂ + 4e^-

e → e → e

H₂O PSII ETC

where photolysis occurs

in the thylakoid space (lumen)

what happens to the H⁺ produced during photolysis

H⁺ remain in the thylakoid space, beginning to build a concentration gradient

what happens to the O₂ produced during photolysis

O₂ diffuses out of the chloroplast → cell → leaf → atmosphere

what happens to the e^- produced during photolysis

e^- from H₂O are transferred to PSII

structure of the 1st ETC

• a series of integral protein complexes within the thylakoid membrane

• the 1st ETC receives excited electrons from the PSII

functions of the 1st ETC (2)

1. transfer electrons from PSII to PSI

2. harness extra energy from excited electrons + use it to pump H⁺ into the thylakoid space (lumen) - this establishes a protein concentration gradient: high (H⁺) in the thylakoid, low (H⁺) in the stroma

location of high concentration vs low concentration of protons

high concentration in the thylakoid space, low concentration in the stroma

ways protons concentrated inside the thylakoid (3)

1. H⁺ produced in the thylakoid during photolysis

2. H⁺ pumped into the thylakoid by the first ETC

3. thylakoids are small spaces so H⁺ accumulates quickly

what is able to occur once the proton gradient is established

• the proton concentration