CH 12: metabolism and bioenergetics

overview of metabolism

-includes metabolism and anabolism

catabolism→ breakdown process, glucose → CO2 + H2O + ATP

-generates energy to be used in anabolism

oxidative

Anabolism→synthesis process, require energy, reductive

starchy foods are hydrolyzed by amylases

digestion:

carbs.→monosaccharides

proteins→amino acids

lipids→ free fatty acids/glycerols

• bonds are covalent, need enzyme to break bonds

• amylase is in the mouth, where digestion begins

  -proteins are hydrolyzed by proteases

  -Fatty acids are hydrolyzed by lipases:released from glycerol backbine, don’t travel well in blood due to hydrophobic character

for transport some fatty acids are linked to cholesterol

-cholesteryl stearate- fatty acids, lipids, cholesterol, proteins

-packed into lipoprotein or chylomicron→ travel through lymphatic system and be processed by liver → high density lipoporteins

-protein travel through blood

adipocytes hold triacylglycerols

-store excess lipids

-carbs used as main energy source

-excess energy/carbon→stored as lipids

1. lipids do not interact with H2O, not hydrated so takes up less weight

2. more energy when oxidize lipids

glycogen structure

-stored only in liver/muscle

-limit of storage for glycogen

-can store a lot glucose and stay stored

-in liver: regulate blood glucose

in muscle: only used for muscle

-only have 1 reducing end, can break off glucose for energy

glycogen breakdown

-occurs via phosphorolysis

-liver break down glycogen

-cleave glycosidic bond and add a phosphate

intermediates of glucose metabolism

glucose→ glyceraldehyde-3-phosphate (in photosynthesis, precursor for glycerol) → pyruvate ( intermediate)→acetyl-coA (intermediate)

many metabolic pathways include redox reactions

carbons in fatty acids and carbohydrates are oxidized to CO2

some cofactors undergo redox reactions

-has intermediate thats oxidized when NAD+ is reduced

reduction of ubiquinone to ubiquinol is stepwise

-ubiquinone (q) is the oxidized form, and ubiquinol ( qh2) reduced form

cofactors are recylced through oxidative phosphorylation

outline of metabolism

NADP+→NADPH - used in anabolism

NAD+→NADH- used in catabolism

things to know: humans do not synthesize some important molecules that are essential

-humans do not synthesize vitamins-need to consume vitamins for metabolic processes to work

complexity of metabolic pathways

1. all connected

2. highly/tightly regulated-energy efficient

3. not every cell involved in every pathway

4. unique metabolic repertoire

5. organisms may be metabolically interdependent

the free energy change depends on reactant concentrations

calculating actual free energy changes

ATP is often involved in coupled processes

-couples an endergonic reaction with an exergonic reaction

-lot of protential to release energy in phosphoanhydride bond →couple with adding phosphate to glucose : unfavorable

favorable : ATP + H2O →ADP + Pi

unfavorable: glucose + Pi→ glucose-6-phosphate

-ATP hydrolysis provides energy for glucose phosphorylation

whats so special about ATP?

-anaerobic proceses to make product-generate energy as breakdown precursors

negative delta G prime → hydrolyze it

-releases a lot of energy-cleavage of phosphoanhydride bond to get energy from

-several different molecules can serve as energy currency within a cell, ex: phosphoenolpyruvate releases -61.p kj of energy

-thioester hydrolysis also releases a large amount of free energy-thioester bond, cleavage is energetically favorable and releases energy

-regulation occurs at steps with the largest free energy changes-tight regulation. if rxn is near equilibrium it could go forward or backward

-if the delta G is very negative, reaction can only go forward