BLG151 - Catabolism and Anabolism

heterotrophs

use organic molecules as a carbon source

autotrophs

use carbon dioxide as a carbon source

phototrophs

use light

chemotrophs

obtain energy via oxidation of either organic or inorganic compounds

lithotrophs

use reduced inorganic substances

organotrophs

extract electrons from reduced organic sources

respiration

uses ETC and a PMF is generated to synthesize ATP

fermentation

does not use ETC but ATP is synthesized by substrate level phosphorylation

aerobic respiration

organic energy source is reduced to CO2 using the glycolytic pathway and the TCA with O2 as the final electron acceptor

glucose catabolism

pyruvate --> CO2 (producing GTP, NADH and FADH2) --> oxidation of NADH and FADH2 using O2

Embden-Meyerhof pathway

1 gluose yields 2 pyruvate, NADH, 2 ATP

TCA cycle

needs 2 turns to oxidize one gluose molecule, yielding 4 CO2, 6 NADH, 2 FADH2, 2 GTP (ATP)

ETC

found in the mitochondria, electron carriers transfer electrons from NADH to FADH2 to a terminal O2 molecule

which way do electrons flow?

flow from carriers with more negative to positive electron potentials

oxidative phosphorylation

ATP is made using electron transport energy driven by oxidation of a chemical energy source

basis of chemiosmotic hypothesis

protons are driven outward from the mitochondrial matrix and transported down ETC, resulting in the formation of a proton concentration and charge gradient

proton motive force (PMF)

the combined potential of chemical and electrical differences

where does ATP synthesis occur in the ETC?

PMF drives this at complex V

how does ATP synthesis occur?

exergonic flow of protons across membrane due to PMF turns ADP into ATP

maximum total yield of ATP from aerobic respiration

32 ATP produced by substrate level phosphorylation

terminal electron acceptors in anaerobic respiration

nitrate, sulfate, CO2, metals, organic molecules

why does anaerobic respiration yield less ATP?

the reduction potential of electron acceptors other than O2 is less positive, resulting in a shorter ETC and smaller PMF

fermentation

NADH must be oxidized to NAD+ so pyruvate or a derivative is used as an electron acceptor

carbohydrate catabolism

saccharides are converted into their monomers by hydrolysis of phospholysis so they can be fed into the glycolytic pathway

lipid catabolism

triglycerides are hydrolyzed to glycerol and fatty acids by lipases

protease

hydrolyzes proteins to amino acids

deanimation

removal of amino group from amino acid, yielding organic acids that can be converted to pyruvate, acetyl-CoA or intermediate

deamination occurs through?

transamination

chemolithotrophy

electrons are obtained by oxidizing inorganic molecules, terminal acceptor is usually O2

chemolithotrophs can either oxidize?

hydrogen, nitrogen or sulfur

light reactions

light energy is trapped and converted to chemical energy

dark reactions

energy produced by light is used to reduce CO2 and synthesize cell constituents

oxygenic photosynthesis

chloroplasts are requires so oxygen can be generated and released

antenna

arrays of chlorophylls and accessory pigments that capture light and transfer it to a reaction center pair

photosystem I

absorbs long wavelengths of light and funnels it to chlorophyll a

photosystem II

absorbs short wavelengths of light and funnels them to chlorophyll pair P680

noncyclic photophosphorylation

ATP and NADPH are made

cyclic photophosphorylation

only ATP made

how does oxygenic photosynthesis work?

- reaction center absorbs light and molecules are changed from positive to negative reduction potentials
- chlorophyll acts as electron donors and electrons flow down ETC, generating PMF
- ATP and NADPH are made