Chapter 14- Cellular Energetics

How to gain energy in the cell

Acetyl CoA

where/which molecules converted into Acetyl CoA

mitochondria using:

sugars/polysaccharides

fats

sugars/polysaccharides

sugars/polysaccharides --> sugars --> glucose --> pyruvate --> acetyl CoA

fats

fats --> fatty acids --> acetyl coA

glycolysis

processing sugar

occurs in the cytoplasm

main process of oxidizing sugars in the cell

ten steps divided among three phases of glycolysis

1. energy investment

2. cleavage/split

3. energy liberation

energy investment

glucose --> fructose 1,6 biphosphate

use 2 ATP

cleavage/split phase

fructose 1,6 biphosphate --> 2 glyceraldehyde-3-phosphates

no energy required

energy liberation

2-glyceraldehyde-3-phosphate --> pyruvate

produces 4 ATP and 2 NADH

net gain of glycolysis

2 ATP, 2 NADH, 2 pyruvate

electron carriers

NAD+/NADH and FAD/FADH2

does glycolysis require oxygen

NO

glycogen

glucose storage polysaccharide found in the liver and muscle of animals; broken down for energy

starch

A storage polysaccharide in plants consisting entirely of glucose.

fat produces __________ the amount of energy as glycogen oxidation

twice

triglycerides

triglycerides -(hydrolysis)-> fatty acids --> ATP

pyruvate oxidation

occurs in mitochondrial matrix

Conversion of pyruvate to acetyl CoA.

citric acid cycle

occurs in the matrix of the mitochondria

breakdown of acetyl CoA and produce NADH, FADH, and ATP

citric acid cycle process

acetyl coA --> citrate --> oxaloacetate

citrate

the conjugate base (or salt/ion form) of citric acid

forms when the enzyme citrate synthase combines a two-carbon acetyl group from acetyl-CoA with a four-carbon oxaloacetate molecule

oxaloacetate

a four-carbon starting and ending intermediate of the citric acid cycle

regenerated from citrate through a multi-step sequence

how many turns of the citric acid cycle turn per glucose

twice

one glucose makes two acetyl coA

net gain of the citric acid cycle

NADH (3 per cycle)

FADH (1 per cycle)

ATP (1 per cycle)

oxidative phosphorylation

occurs inner mitochondria membrane

harness energy from electron transfer

generates lots of ATP

requires oxygen

needs lots of electrons to drive process

oxidative phosphorylation process

NADH + 1/2O + H+

ADP + Pi

--> NAD+ + H2O + ATP

why is cellular respiration multiple steps

to prevent combustion or explosive release of energy

why is oxygen needed in oxidative phosphorylation

e- put into H2O as a safe disposal method that will not harm the cell

ATP synthase (cellular respiration)

to synthesize ATP (adenosine triphosphate), the main chemical energy currency of living cells, by using the energy derived from a transmembrane proton (or hydrogen ion) electrochemical gradient

electron transport chain complexes

four main protein complexes embedded in the inner mitochondrial membrane that transfer electrons and pump protons to drive ATP synthesis

complex I

NADH dehydrogenase (bring e- from NADH)

proton pump

complex II

succinate dehydrogenase (bring e- from FADH2)

do not pump protons

complex III

cytochrome-c-reductase

proton pump

complex IV

cytochrome-c-oxidase

proton pump H2O formation

ubiquinone

transports electrons from I to III

cytochrome c

transports electrons from III to IV

electron transports relies on

co-factors

co-factors

accept and give up electrons readily

useful for processing electrons between and through complexes

common co-factors in the ETC

iron-sulfur clusters

cytochrome c

quinones (coenzyme Q)

quinones (coenzyme Q)

change shape based on number of electrons obtained

uniquinone

Coenzyme Q

Vital electron carrier associated with complexes I, II and III of the ETC

ubisemiquinone

QH

partially reduced free radical of ubiquinone

ubiquinol

QH2

reduced form of ubiquinone

redox potential

- molecules with high redox pull electrons

- molecules with low redox give up electrons

more negative molecules

more likely to give up electrons

change in redox potential drives ETC

increasing positive redox potential down chain pulls electrons through

NADH dehydrogenase complex

L-shaped

Peripheral Arm (Hydrophilic / Matrix Arm)

Membrane Arm (Hydrophobic / Transmembrane Arm)

electron transfer of NADH dehydrogenase complex

separate from proton pumping

electrons transferred in through matrix from NADH

iron-sulfur clusters in NADH dehydrogenase complex

transport up from the matrix arm

electrons meet ubiquinone in the arm

alpha helix in NADH dehydrogenase complex

runs along the length of the membrane arm

move back and forth

open mechanically gated H+ pumps

NADH dehydrogenase complex pump

4 protons pumped into crista from matrix space

Q-cycle

NADH dehydrogenase complex passes on electrons via fully reduced quinones

fully oxidized quinones

pick up more electrons

cytochrome c reductase

electrons transport through this complex

quinone with a single unpaired electron; free radical

allows for ubisemiquinone to become fully reduced

cytochrome c oxidase

reduction of O2 to form two molecules of H2O without releasing partially reduced, dangerous oxygen intermediates

bi-metallic center of cytochrome c oxidase

Cu and Fe

holds reactive oxygen intermediates

electron transport chain complexes

Mitochondrial ATP synthase

spinning rotor/central stalk

static stator

flow of electrons

triggers ATP synthase rotor to turn

rotor rotation

triggers movement of subunits in the stator

ATP synthesis

1 turn of ATP synthesis

3 ATP

Beta barrels in outer mitochondrial membrane

allow it to be more porous than inner mitochondrial membrane

Pool of protons

electron transport chain pools protons in the cristae

dimer ATP synthase

always at the end of the crista

- stabilizing

- benefit from pool of protons

ADP/ATP carrier proteins

shuttle ATP into the cytosol, to be used

shuttle AP into the matrix, to be make into ATP

collaboration of chloroplasts and mitochondria

plants are not consumers and need chloroplasts to generate sugars for mitochondria

photosynthesis

process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches

chloroplasts

contain membrane bound compartments (thylakoids)

significantly larger than mitochondria

thylakoids

where machinery for electron transport chain exist

light reactions

electrons used for photosynthetic electron transfer are energized by photons from sunlight

electrons in photosynthesis

taken from split H2O molecule

energized by light reaction

fed through ETC, forming a proton sink in thylakoid space

ATP in photosynthesis

generated along with NADH

Water

has very high redox potential (terrible electron donor)

photosystem II

charged with light ( - redox) and bring electrons from water to a more negative redox potential

electron carried by photosystem II

more negative redox potential; brought to:

plastoquinone --> cytochrome b6t complex --> plastocyanin

now has more positive redox potential

photosystem I

charged with light ( - redox) and bring electrons from water to a more negative redox potential

electron carried by photosystem I

more negative redox potential; brought to:

ferredoxin--> ferredoxin-NADP+ reductase

now has more positive redox potential

ferredoxin-NADP+ reductase

reduces NADP+ to NADPH

Chloroplast co-factors

quinones

plastocyanin

iron-sulfur clusters

quinones

movee electrons from photosystem II to cytochrome b6f complex

plastoquinones

plastocyanin

move electrons from cytochrome b6f to photosystem I

iron-sulfur clusters

move electrons within photosystem

cytochrome b6f

proton pump to make proton gradient

ATP synthase (photosynthesis)

uses proton gradient to make ATP

Ferredoxin—NADP⁺ reductase

makes NADPH with carried electrons

pH in mitochondria

intermembrane space, more protons (pH = 7.4)

matrix, protons pumped out (pH = 7.9)

mitochondria electron source

NADH

high energy NADH to low energy water

mitochondria cofactors

Q-cycle, iron-sulfur clusters

mitochondria redox potential

starts negative

mitochondria proton pumping

3 complexes

pH in chloroplast

thylakoid space, more protons (pH = 5.5)

stroma, protons pumped out (pH = 8)

intermembrane space (pH = 7.4)

chloroplast electron source

water

low energy water to high energy NADH

chloroplast cofactors

Q cycle, iron-sulfur clusters

chloroplast redox potential

starts positive

chloroplast proton pumping

one complex

carbon fixation

utilize NADPH and ATP from light reactions to drive Calvin cycle

Calvin cycle

in the chloroplast

electrons from NADPH

PO4 from ATP

carbon from CO2

dark reaction

the portion of photosynthesis that does not need light to occur; the building of the glucose molecule

phosphoglycerate

made from 3 CO2 fused with RuBP by rubisco

glyceraldehyde-3-phosphate

made from phosphoglycerate energized by ATP and reduced by NADPH

1 glyceraldehyde-3-phosphate

Three-carbon sugar produced in the Calvin cycle.