BioChem CH15/16 E2

how are molecules in food broken doen

-large molecules are broken down into smaller molecules in digestion
-small molecules are processed into key molecules of metabolism (acetyl CoA)
-ATP is produced from the complete oxidation of acetyl CoA

why is energy required? and how do phototrophs/chemotrophs obtain energy

-required to power muscle contraction, cell movement, and biosynthesis
-phototrophs: catpure sunlight
-chemotrophs: through oxidation of carbon fuels

what are the basic principles of energy manipulation

1.molecules are degraded or synthesized stepqise in a metabolic pathway
2.ATP is energy currency of life
3.ATP can be formed by oxidation of carbon fuels
4.a limited number of reaction types hat involve particular intermediates ar3e common to all metabolic pathways
5.metaabolic pathways are highly regulated (by allosteric enzymes)
6.enzymes involved in metabolism are organized into large complexes

what is metabolism/intermediary metabolism

-metabolism is a series of linked reactions that convert a specific reactant into a specific product
-intermediary: entire set of cellular metabolic reactions

what are the 2 types of metabolic pathways

-catabolic and anabolic

what are amphibolic pathways

-pathways that function anabolically or catabolically

what 2 criteria must be met to construct a metabolic pathway

1.individual reactions must be specific
2.pathway in total must be thermodynamically favorable

how is ATP hydrolysis exergonic

-it releases energy
-energy released on ATP hydrolysis is used to power a host of cellular function

how is ATP in cells

-cells maintain a very high concentration of ATP
-ATP may function as a biological hydrotrope
-ATP prevents the formation of protein aggregates and dissolves those that form

why are phosphates and its esters prominent in biology

1.phosphate esters are thermodynamically unstable, yet they are kinetically stable
2.they are stable because the inherent negative charages resist hydrolysis
3.since they are kinetically stable, they are ideal regulatory molecules

what is ATP for biological activities

-its the immediate donor of free energy
-amount of ATP is limited
-ATP must be constantly recycled to provide energy to power the cell

how/why is oxidation paired with reduction

-oxidation reactions involve loss of electrons
-must be coupled with reactions that gain electrons (reduction)
-paired reactions are called oxidation-reduction reactions or redox reactions
-the more reduced a carbon atom is the more free energy is released

what are 2 characteristics to activated carriers

1.carriers are kinetically stable in the absence of specific cataylsts
2.the metabolism of activated froups is accomplished with a small number of carriers

what is ATP an activated carrier for

phosphoryl groups

what kind of activated electrons do NAD+ and FAD carry

-derived from the oxidation of fuels

what is NADP+ an activated carrier for

-carrier of electrons for reductive biosynthesis

what is coenzyme A an acitivated carrier of

-acyl groups such as the acetyl group
-transfer of acyl group is exergonic because the thioester is unstable

how is homeostasis maintained? what are the 3 regulatory controls

1.the amount of enzymes present
2.the catalytic activity of enzymes
3.the accessibility of substrates

what level is the quantity of enzymes present regulated at? how is catalyitc activity regulated

-level of gene transcription
-catalytic: regulated allosterically or by reversible covalent modification

why is glucose a prominent fuel

1.may have been availiable for primitive biochemical systems bc it can form under prebiotic conditions
2.most stable hexose
3.has low tendency to nonenzymatically glycosylate proteins

what does glycolysis convert one molecule of glucose to

-two molecules of pyruvate witht he generation of 2 molecules of ATP

what are the 2 stages of glycolysis

Stage 1: Energy investment

• Glucose is trapped and prepared for splitting.

• Uses 2 ATP to make the molecule ready for energy extraction.

Stage 2: Energy payoff

• The 3-carbon pieces are converted to pyruvate.

• Makes 4 ATP, so net gain is 2 ATP.
  
  stage 1: traps glucose int he cell and modifies it so that it can be cleaved into a pair of phosphorylated 3-carbon compounds (2ATP molecules consumed)
  stage 2: oxidizes the 3-carbon compounds to pyruvate while generating 2 molecules of ATP (4 ATP are produced→ 2-2=2 made)

what does hexokinase do

-traps glucose in the cell and begins glycolysis
-catalyzes the reaction
-it employs substrate binding induced fit to minimize hydrolysis of ATP

what are the 2 steps to form 1,3-bisphosphoglycerate

1.the highly exergonic oxidation of carbon 1 in GAP to an acid
2. and the highly endergonic formation of 1,3-bisphosphoglycerate from the acid

how can 1,3-bisphosphoglycerate power the sysnthesis of ATP to ADP

because it has a greater phosphoryl transfer potential than ATP

what does the conversion of glucose into pyruvate generate? and how is it continued

-generates ATP but for ATP synthesis to continue, NADH must be reoxidized to NAD+
-NAD+ can be regenerated by further oxidation of pyruvate to CO2 or by formation of ethanol or lactate from pyruvate

what are fermentations

-are ATP generating pathways in which electrons are removed from one organic compound and passed to another organic compound

what is alcohol fermentations

-the conversion of glucose into 2 molecules of ethanol

what is lactic acid fermentation

-conversion of glucose into 2 molecules of lactate

how is galactose converted into glucose 6-phosphate

by the galactose-glucose interconversion pathway

what causes classic galactosemia

-results if galactose 1-phosphate urigyl transferase activity is deficient
-sugars cause cataracts (galactose is converted into galactitol which is poorly metabolized; galactitol is osmotically active and causes water to diffuse into the lens)

^{what is the key regulator of glycolysis in mammals}

phosphofructokinase
-enzyme is allosterically inhibited by ATP and allosterically stimulated by AMP

what is the key regulatory of phosphofructokinase in the liver

citrate
-it inhibits phosphofructokinase

what is hexokinase responsible for in the liver

-for phosphorylating glucose (glucokinase)
-is active only after a meal, when blood glucose levels are high

what do 5 glucose transporters facilitate

-the movement of glucose across the cell membrane

what is aerobic glycolysis

-rapidly gorwing tumors obtain ATP by metabolizing glucose to lactate even in the presence of oxygen

what does aerobic glycolysis generate

-Aerobic glycolysis makes lactic acid to support fast tumor growth, even with low oxygen.

-generates lactic acid which acidifies the environment and may allow further tumor growth
-because tumors can grow faster than the blood vessels, aerobic glycolysis allows growth in the absence of oxygen

how does glycolysis help pancreatic beta cells snese glucose

-insulin is secreted by beta cells of the pancreas in response to high blood levels of glucose.