i.Free __is not common in diets; calories are from__ ii.Glycolysis can accept several carbs (especially disaccharides) for __ 1.Starch à __ -->__à __ 2.Glycogenà __
glucose
fats, proteins, sucrose and other disaccharides, and starch
catabolism
glucose
pyruvate by glycolysis
CAC
glucose between meals as fuel
Proteins can be used, but what must happen first?
- a.Many amino acids used to__ i.If in excess, they are __ 1.Firstwhatmusthappen?
digested to amino acids first
build new proteins
converted by enzymes to intermediates of glycolysis and the CAC
, their amino groups must be removed (deamination) and excreted
i.Fats 1.After digestion into __, the __is converted to glyceraldehydes-3-phosphate__, an intermediate of glycolysis
glycerol and fatty acids
glycerol
glycerol
a.Most energy in fatty acids i.__breaks the fatty acids down to__, which enter CAC as __ 1.__also generates NADH and FADH2
Beta oxidation
two-carbon fragments
acetyl CoA
Beta oxidation
True or Flase: Carbs make twice as much ATP as fats.
false; other way around
a.Biosynthesis i.Cells need substance as well as energy; not all organic molecules destined for__ ii.Food also provides__ for production of molecules 1.Amino acidsà directly into proteins iii.Molecules not present readily 1.Compounds formed as intermediates of glycolysis and the CAC can be __ iv.__and the __function as metabolic interchanges that enable our cells to convert some kinds of molecules to others as we need them
oxidation to make ATP
carbon skeletons
changed into precursors for synthesis of molecules
Glycolysis and the CAC
a.Feedback Mechanisms i.The cell doesn’t waste energy making unneeded molecules 1.If excess, the anabolic pathway that synthesizes that molecule is __ (ex: amino acid) a.__: end product inhibits the enzyme that catalyzes an early step of the pathway, preventing the needless diversion of key metabolic intermediates from uses that are more urgent
s turned off
Feedback inhibition
i.Cell also controls __ 1.If ATP concentration drops, respiration __ 2.Plenty of ATP results in __ 3.Control is regulated at strategic points in the pathway
catabolism
speeds up
slowing down of respiration
Explain phosphofructokinase.
a.Phosphofructokinase catalyzes step three of glycolysis
i.First step that commits substrate irreversibly to the glycolytic pathway
1.Through control, the cell can speed up or slow down the entire catabolic process
ii.It is a pacemaker
i.Phosphofructokinase 1.Allosteric enzyme with receptor sites for specific __ and __ a.Inhibited by __, which slows down glycolysis b.Stimulated by __
inhibitors and activators
ATP
AMP
Explain citrate.
If accumulates in mitochondria, some of it inhibits phosphofructokinase, helping synchronize the rates of glycolysis and the CAC
- citrate accumulates: glycolysis slows down and supply of acetyl groups to CAC decreases
- citrate consumption increases, glycolysis accelerates and meets demand
