Chapter 3: Section E: Metabolic Pathways AKA DEATH Flashcards Preview

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Flashcards in Chapter 3: Section E: Metabolic Pathways AKA DEATH Deck (21):

Cellular respiration

- process by which a series of metabolic reactions uses the energy in food to produce ATP
- 3 main processes: 1) glycolysis 2) Krebs cycle 3) oxidative phosphorylation


Aerobic respiration

- requires O2
- in mitochondria
- glucose is completely broken down
- generates 36 ATP


Anaerobic respiration

- doesn't require O2
- in cytosol
- glucose is incompletely broken down generating only 2 ATP



- takes place in cytosol
- generates 2 ATP molecules via substrate-level phosphorylation, 2 NADH molecules, and 2 pyruvic acid (pyruvates)
- in absence of O2, pyruvate undergoes fermentation
- if O2 present, pyruvate enters mitochondrion and aerobic respiration proceeds
- under anaerobic conditions of high demand, lactate is created when muscles working hard


Transitional step

- under aerobic conditions in mitochondrial matrix
- pyruvic acid is converted to acetyl-CoA
- 2 pyruvate + 2 Coenzyme A = 2 acetyl-CoA + 2CO2 + NADH
- acetyl-CoA enters Krebs cycle


Krebs Cycle (citric acid cycle)

- occurs in mitochondrial matrix
- generates: 2 ATP, 6 NADH, 2 FADH2 (34 CO2 waste product)
- turns twice per molecule of glucose (2 acetly coa)


Oxidative phosphorylation/Electron transport chain

- located on cisternae (folds of inner mitochondrial membrane)
- made of series of integral membrane proteins (cytochromes) that act as electron carriers
- NADH and FADH2 donate e- to ETC
- electrons are passed from one cytochrome to next, it drives the pumping of H+ ions from inner compartment of the mitochondrion to the outer compartment
- O2 is the final electron acceptor! Is reduced and combines with H+ to form H2O without O2 the chain stops!!!


Chemiosmotic hypothesis

- ATP synthases (enzyme complexes associated with the inner mitochondrial membrane) and they catalyze the production of ATP
- ADP+Pi --> ATP
- ATP synthase activity is driven by H+ moving through it. H+ move from increase to decrease concentration
- for every NADH that reaches ETC, 3 ATP made
- for every FADH2, 2 ATP made


Carbohydrate Metabolism

- glucose catabolism results in ATP synthesis via a combination of substrate-level and oxidative phosphorylation
- glycogen storage and breakdown
- enzymes located in cytosol
- excess of glucose in liver or muscle cells --> glycogenesis
- deficiency of glucose --> glycogenolysis activated
- glycogen --> glucose - 6- phosphate
- G-6-P undergoes glycolysis in most cells
- G-6-P can be converted to free glucose in liver and kidney cells and enters blood



synthesis of glucose from non-carbo sources in liver and kidney cells
- enzymes located in cytosol for process
- controlled by hormones released in response to changes in blood sugar levels


Fat metabolism

- 78% body = triglycerides
- fatty acid catabolism occurs in mitochondria
- one gram of fat generates about 2.5 times as much ATP as 1 gram of carbo
- process initiated by linking a coenzyme A molecule to the carboxyl end of fatty acid
- fatty acid derivative then undergoes beta oxidation
- splits off an acetyl CoA molecule from the fatty acid which removes 2 carbons
- another CoA is added and cycle repeats until all C atoms have been transferred
- acetyl coA enters the krebs
- transfers a pair of H atoms to FAD and NAD+ (oxidative phosphorylation)
- fatty acid synthesis involves same enzymes and reactions as catabolism but in reverse
- enzymes located in cytosol
- 2 carbons at a time are added to growing fatty acid via acetyl coa
- fatty acids are joined to glycerol via enzymes associated with sER --> triglyceride
- glucose can be readily converted into fat, but the fatty acid portion of fat cant be converted into glucose



- proteases: splits off one amino acid at a time OR breaks peptide bonds between specific amino acids, forming peptides
- amino acids can be catabolized to produce ATP, reused in protein synthesis, or to provide intermediates for the synthesis of molecules other than proteins


Steps of catabolism

1) amino group must be removed from the amino acid through oxidative deamination or transmination
2) remainder of the amino acid can be metabolized to intermediates that enter the krebs cycle or glycolytic pathway, undergo glyconeogenesis, etc


oxidative deamination

- amino group removed from amino acid and converted to ammonia and then an O2 atom replaces amino group forming keto acid



- amino group is transferred from amino acid to keto acid
- the amino acid from which the amino group has been removed has an oxygen added forming keto acid
- keto acid picks up amino acid
- responsible for converting one amino acid to another


Keto Acids

- produced in either krebs or glycolysis
- can be used to generate ATP or undergo gluconeogensis or to be used to synthesize fatty acids or other amino acids


Amino Acid synthesis

- synthesized from keto acids, derived from carbos and fats
- glucose --> pyruvic acid and a-ketoglutaric acid --> transamination --> glutamate and alanine
- 11 of 20 amino acids can be synthesized by the body
- 9 must be obtained in diet


Amino acid pools

- total free amino acids in body
- come from ingested proteins, synthesized from keto acids derived from carbs and fats, and breakdown of body proteins
- used to resynthesize body proteins, amino acid derivates, and conversion to carbos and fats
- primary way a.a. lost from pool is from oxidative deanimation --> excretion of nitrogen atoms as urea in the urine


Negative nitrogen balance

- net loss of amino acids over a given period of time


Positive nitrogen balance

- net gain of amino acids over a given period of time


Essential nutrients

- nutrients essential to health that are not synthesized by the body in adequate amounts
- required in diet!!
- water, minerals, amino acids, fatty acids, vitamins, and nutrients