Biology 1020: Unit 4.3 Energy Conversion and Metabolic Compartmentalization: Mitochondria & Chloroplasts

endosymbiosis

mitochondria and chloroplasts are thought to be domesticated bacteria… they were prokaryotes that ended up inside of other cells by phagocytosis and survived

anaerobic

no oxygen required

aerobic

oxygen required

mitochondria structure

has inner and outer membrane; inner membrane covers the matrix, creating cristae pockets. the inner membrane is the site of the electron transport chain and is heavily folded to maximize workable surface area

chloroplasts structure

inner and outer membrane in addition to internal stacks of thylakoid membranes. energy harvesting ETC is in the thylakoid membranes

inner membrane is not connected to thylakoid membrane

photosynthesis

plants and cyanobacteria do photosynthesis carried out by chloroplasts; converts sunlight to energy in the form of glucose 6H2O + 6CO2 + light → C6H12O6 + 6O2. consists

cellular respiration

mitochondrai burn food and sugar molecules to produce ATP. plants and animals both do this. 6O2+C6H12O6 —> 6CO2 + 6H2O + energy (ATP)

how do animal eukaryotic cells get glucose

the food you eat is broken down into glucose molecules that are transported from intestinal lumen through intestinal epithelial cells: RE: apical vs basolateral transporters…

when blood levels go up, it signals your pancreas to release insulin (helps glucose get into cells)

insulin binds to insulin receptor (RTK) resulting in activation of glucose channels in membrane

anaerobic respiration

produces 2 ATP molecules from glycolysis (happens in absence of oxygen)

aerobic respiration

produces 36 net ATP molecules (glycolysis + krebs cycle (Citric Acid) + oxidative phosphorylation (ETC)). glucose is oxidized to eventually form carbon dioxide and water

Glycolysis

first 10 reactions of cellular respiration that occurs in the cytosol.

• glucose is converted into 2 molecules of pyruvate (3 carbonmolecule) through oxidation

• electrons from glucose are used to make 2 NADH

• 2 ATP are invested but 4 are made —> 2 net

when pyruvate is moved into mitochondria for krebs cycle, it is converted into Acetyl CoA (another 3 carbon molecule)

what is reduced and oxidized during glycolysis?

glucose is oxidized, NAD+ is reduced

Krebs cycle

• occurs in mitochondrial matrix

Products per cycle (goes around twice per 1 glucose molecule) (the following are given per acetyl coA)

• oxidizes acetyl coA: electrons are used to make 3 NADH and 1 FADH2

• one ATP produced

• 2 waste molecules of CO2 produced

oxidative phosphorylation

(ETC in cellular respiration) NADH and FADH2 transfers its electrons to oxygen through three large enzyme complexes. NADH drops off at Complex I and FADH2 drops off at Complex II. each time electrons pas through, energy is released. this energy is used to pump protons across the membrane from matrix into intermembrane space. this generates a charge gradient and protons can only pass through with ATP synthase, which generates 3 ATP per turn driven by the flow of 10 protons down the gradient. oxygen finally arrives at the end, serving as the final electron acceptor and picks up protons to form water.

where do glucose’s electrons go in aerobic respiration?

electron carriers NADH and FADH2 bring them to the ETC.

how was it proved that ATP synthase rotates?

fluorescently labeled actin filament was attached to tip of shaft: could see the fiber rotate via fluorescnece

what were the first photosynthetic organisms

cyanobacteria

oxygen produced from photosynthesis allowed for aerobic cellular respiration —> new complex life forms

light reactions

ETC of photosynethesis: a photon of light knocks an electron out of the chlorophyll within a rxn center protein complex in thylakoid membrane and is transfered to second rxn center, resulting in proton gradient used by ATP synthase to generate ATP. also produces NADPH

what is the ATP produced from light rxns used for

to power the carbon fixation rxns, to make sugards

photosystem

clusters of hundreds of photosynthetic pigments that collect light energy and pass it to special chlorophyll at rxn center. contains chlorophyll

chlorophyll

green pigment (light absorbing molecule) of photosynthetic organisms has a long hydrophobic tail that makes it behave like a lipid plus ring structure that has delocalized electrons in double bonds and a central Mg atom

what happens when chlorophyll absorbs light

• photon hits PSII reaction center, causing an electron to reach high energy level, escape, and is caught by quinone

• PSII is desperate for electron, so it splits water (1/2O + e- + 2H+)

• pumps protons into lumen and produces oxygen and gets electrons from water

reaction centers

special pair of chlorophyll molecules at core of photosystems

carbon fixation/calvin cycle (dark rxns)

uses ATP and NADPH to convert CO2 into sugars