bio lesson 9

after first 3 stages of aerobic resp (glycolysis, pyruvate oxidation, krebs)

-1 glucose molecules is reduced to

1. 6 CO2

2. 4 ATP

3. 10 NADH

4. 2FADH

• 10 NADH and 2FADH proceed to ETC so that energy carried in the electrons can be harvested and used to drive ATP synthesis (oxidative phosphorylation)

-oxidative phosphorylation prod majority of ATP derived from glucose oxidation

ETC

-allows for the stepwise extraction of energy as electrons are passed from one component to the next

-the energy delpeted electrons are eventually transferred to a final acceptor (O2)

-electron energy is converted to ATP after the ETC

*high energy electrons enter ATC and in a step by step fashion, descend into progressively lower energy levels as some of their energy is collected to ultimately synthesize ATP

ETC components

-ETC is a series of membrane-bound protein complexes and lipid soluble electron carriers

-in eukaryotes, ETC is embedded in the inner mitochondrial membrane

-inner membrane separates the matrix from intermembrane space

how does the ETC work?

-3 transmembrane enzyme complexes harvest some energy from electrons and pass lower energy electrons forward

-complexes use energy harvested from electrons to pump proteins from matrix to intermembrane space

-matrix has low H+, intermembrane space has high H+

chemiosmosis

-the proton gradient represents potential energy

-ATP synthase uses energy released by movement of protons to synthesize ATP from ADP and Pi

-mvmt of 4H+ through ATP synthase, powers synthesis of 1 ATP molecules

-proton motive force drives the formation of ATP

-involves the enzymatic head which catalyzes the production of ATP and a membrane bound channel protein

-protons travel through channel protein from intermembrane space to matrix

calculating the energy yield of respiration

-NADH: (10 H+ transported/4 H+ or ATP)= 2.5 ATP/NADH

-FADH2: (6 H+ transported/4 H+ or ATP)= 1.5 ATP/FADH

-total net ATP yield= 32 (30 in eukaryotes)

anaerobic respiration

-inorganic molecules (not O2) used as final electron acceptor

-many prokaryotes use sulfur, CO2, inorganic metals

-free energy and ATP prod is less that w/ O2

-ex: methanogens

1. CO2 is reduced to CH4 (methane)

2. found in diverse environments (including cows)

fermentation

-in anaerobic conditions, specific organic molecules will serve as the final electron acceptors in fermentation

-glycolysis is only source of ATP

-reduces organic molecules in order to regenerate NAD+

-ex: thanol fermentation in yeast

1. CO2, ethanol, NAD+ are prod

-ex: lactic acid fermentation

1. occurs in animal cells (esp muscles)

2. electrons are transferred from NADH to pyruvate to produce lactic acid

extraction of energy from macromolecules

-proteins, polysaccharides, lipids/fats are sources of energy for cells

-the oxidation of these food groups prod a common group of key intermediates such as pyruvate and acetyl-CoA that are metabolized by krebs

catabolism of proteins

-first, broken down into individual amino acid subunits

-amino acids undergo deamination to remove amino group

-remainder of amino acid is converted to a molecule that enters glycolysis or krebs

catabolism of fats

-fats are first broken down to fatty acids and glycerol

-fatty acids are converted to acetyl groups by beta oxidation

1. each acetyl group is combined with Coenzyme A to form acetyl-CoA

2. acetyl-CoA enterns krebs

3. respiration of 6-C fatty acid yields 20% more energy than 6C glucose