BioChem 2 Exam 2

basic principles governing energy manipulation in cells

1) molecules are degraded or synthesized stepwize in a series of reactions (metabolic pathways)

2) ATP is the nergy currency of life

3) ATP can be formed by the oxidation of carbon fuels

4) although many reactions occur inside a cell, there are limited number of reaction types involving particulat intermediates that are common to all metabolic pathways

5) metabolic pathways are highly regulated

10

glucose is metabolized to pyruvate in ___ linked reactions

lactate; acetyl CoA

under anaerobic conditions, pyruvate is metabolized to ____ and, under aerobic conditions, to _____

CO2

the glucose derived carbon atoms of acetyl CoA are subsequently oxidized to ___

catabolic and anabolic

metabolic pathways can be divided into two types:

catabolic pathway

combust fuels to synthesize ATP

anabolic pathways

use ATP and reducing power to synthesize large biomolecules

1) the individual reactions must be specific

2) the pathway in total must be thermodynamically favorable

in order to construct a metabolic pathway, two criteria must be met:

coupling it to a more favorable reaction

a thermodynamically unfavorable reaction in a pathway can be made to occur by _____

hydrolysis of ATP

is exergonic because the triphosphate unit contains two phasophoanhydride bonds that are unstable

energy

___released on ATP hydrolysis is used to power a host of cellular functions

ATP

the structure of this consist of adenine, a ribose, and a triphosphate unit

P_a , P_B , P_y

the inner most phosphorus atom of ATP is designated ___, the middle one ____, and the outermost one ____.

ATP

is an energy coupling agent

1) charge repulsion (4 negative charges)

2) resonance stabilization makde ATP a high energy phosphoryl transfer group

3) increase in entropy

4) stabilization by hydration

ATP has a high phosphoryl transfer potential because of four key factors:

creatine phosphate

a quick source of energy; enough ATP for less than a second

oxidation of fuel, molecules, or photosynthesis

ADP to ATP

motion, active transport, biosyntheses, signal amplification

ATP to ADP

recycled

ATP must constantly be ___ to provide energy to power the cell

oxidation-reduction reaction or redox reaction

an oxidation reaction must be coupled with ractions that gain electrons (reduced)

oxidized

the carbon atoms in fuels are ____ to yield CO2, and the electrons are ultimately accepted by oxygen to form H2O

free energy

the more reduced a carbon is the more ____ is released upon oxidation

ATP synthesis

compounds with high phosphoryl transfer potential can couple carbon oxidation to ____

catabolism

is capturing the energy of carbon oxidation as ATP

oxidation

____of the carbon atom may form a compound with high phosphoryl transfer potential that can then be use to synthesize ATP

high phosphoryl transfer potential

oxidation of the carbon atom may form a compound with ____ that can be then used to synthesize ATP

activated carriers

are kinetically stable in the absence of specific catalysts; the metabolism of activated groups is accomplished with a small number of carriers

vitamins

ATP is an activated carrier of phosphoryl groups. other activated carriers are common in iochemistry, and often they are derived from _____

Nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD)

carry activated electrons derived from the oxidation of fuels

nicotinamide adenine dinucleotide (NAD+)

is a prominent carrier of high energy electrons derived from the vitamin niacin (nicotinamide); reduced to NADH (accepts 2 electrons and 1 proton)

flavin adenine dinucleotide (FAD)

this electron carrier consists of the vitamin riboflavin and an ADP unit; accepts 2 electrons and 2 protons

NAD

accepts high energy electrons during cellular respiration to become NADH. it is involved in all stages of respiration; involved in cellular respiration processes throughout the cell inclusinfing glycolysis and the Krebs cycle

FAD

accepts high energy electrons during the Krebs cycle to become FADH2; primarily involved in the Krebs cycle, which occurs in the mitochondria

each reduced NADH molecule

is eventually used to produce more ATP in the electron trnasport chain, yielding a higher amount of energy

eahc reduced FADH2 molecule

is also used to produced ATP but it is oxidized later in the electron transport chain, resulting in a lower energy yield

higher; lower

NAD has a ____ redox potential, which allows it to carry more energy. FAD has a _____ redox potential which makes it suitable for metabolic steps that requires less energy

beginning; further along

NAD is oxidized at the ____ of the electron transport chain. FAD if oxidized ____ in the the electron transport chain

Nicotinamide adenine dinucleotide phosphate (NADH+)

is an activated carrier of electrons for reductive biosynthesis (fatty acid synthesis)

Coenxyme A (CoA-SH)

is an activated carrier of acyl groups such as the acetyl group; the transfer of the acyl group is exergonic because the thioester is unstable

vitamin A

roles in vision, growth, reproduction

deficiency: night blindness, cornea damage, damage to respiratory and gastrointestinal tracts

vitamin C (ascorbate)

antioxidant

deficiency: Scurvy

scurvy

swollen and bleeding gums, subdermal hemorrhaging

vitamin D

regulation of calcium and phosphate metabolism

deficiency: rickets (children): skeltal deformities, impaired growth; Osteomalacia (adults): soft, bending bones

vitamin E

antioxidant

deficiency: lesions in muscles and nerves (rare)

vitamin K

blood coagulation

deficiency: subdermal hemorrhaging

homeostasis

a stable biochemical environment, is maintained by careful regulation of biocheical processes

1) the amount of enzymes present

2) the catalytic activity of enzymes

3) the accessiility of substrates

3 regulatory control are especially prominent for homeostasis:

gene transcription

the quantity of enzyme present can be regulated at the level of ____

catayltic activity

is regulated allosterically through feedback inhibition or by covalent modification

hormones

coordinate metabolic activity, often by insitgating the covalent modification of allosteric enzymes

eninephrine

breakdown glycogen to glucose for energy (muscle)

glucagon

glucose relase from glycogen (liver)

opposing reactions

may occur in different cellular compartments (fatty acid synthesis and degradation)

metabolism

regulating the flu of substrates between compartments is used to regulate _____

glucose

a prominent fuel in all life forms because it may have been available for primitive biochemical system because it can form under prebiotic conditions; the msot stable haxose; a low tendency to nonenzymatically glycosylate proteins

formaldehyde

is the source of glucose

first stage of glycolysis

glucose is trapped, destabilized, and cleaved into two interconvertible 3C molecules, generated by the cleavage of 6C fructose (phosphorylation, isomerization, phosphorylation)

stage two of glycolysis

the 3C units are oxidized to pyruvate, generating ATP (oxidation reaction, ATP formation, ATP formation)

hexokinase

this enzyme is used for the first step of glycolysis; phosphorylates glucose to trap it in the cell

phosphoglucose isomerase

this enzyme is used for the second step of glycolysis; reversible reaction that converts glucose 6-phosphate to fructose 6-phosphate; important because without the conversion glucose 6-phosphate will not be able ot be cleaved into two 3 carbon sugars

phosphofructokinase (PFK)

this enzyme is used for the third step of glycolysis; adds a second phosphate to form fructose 1,6-bisphosphate to trap in it the fructose form; creates a symmetrical structure that can split into two; irreversible reaction

aldolase

this enzyme is used for the fourth step of glycolysis; cleaves the 6C to two 3C sugars one an aldose (GAP) and the other a ketose(DHAP)

triose phosphate isomerase

DHAP and Gap are isomers and this enzyme can change them to one or the other

1,3,BPG (1,3-Bisphosphoglycerate)

oxidation of GAP forms a high phosphoryl compound

glyceraldehyde 3-phosphate dehydrogenase

this enzyme is used for the fifth step of glycolysis; a compound with high phosphoryl transfer potential, 1,3-Biophosphoglycerate, is generated by the oxidation of GAP in a reaction catalyzed by this

would not occur

if the oxidation reaction and acyl phosphate formation are not couple, then ____

thioester intermediate

couples the oxidation and acyl formation which lowers the activation energy

substrate level phosphorylation

transfer a phosphate from a substrate to ADP (ex. formation of ATP from the high energy phosphoyl group 1,3-BPG)

oxidation reduction reaction

ATP is generated from phosphenolpyruvate conversion to pyruvate (phosphate is rearranged)

GLucose + 2Pi + 2ADP + 2NAD+ → 2 pyruvate + 2ATp + 2NADH + 2H+ + 2 H2O

the net reaction for glycolysis:

2; 4; 2

in glycolysis ___ ATP are used and ___ ATP are made which makes the net ATP ____

lactate

acetyl CoA → futher oxidation

Actealdehyde → ethanol

what three forms can pyruvate turn into?

lactate

is acidic so the muscle cells do not keep it for long (the liver helps out)

lactate

pyruvate gets turned into this with lactate dehydrogenase And NADH (which turns into NAD+); is anaerobic

acetyl CoA

pyruvate get turned into this with the addition of O2 and release of CO2; is aerobic and can go through further oxidation

acetaldehyde

pyruvate gets turned into this through alcoholic fermination from pyruvate decarboxylase (TPP) and the release of CO2; is aerobic

ethanol

pyruvategets turned into this after it is turned into acetaldehyde through alcohol dehydrogenase and NADH with the release of NAD+

physiological condition, tissues, and organisms

the fate of glucose is varies with _____

decarboxylase

whrn some form of carbon comes out of a reaction

alcoholic fermentations

are the means of oxidizing NADH; the conversion of glucose into two molecules of ethanol

thiamine (vitamine B)

is a compoenent of the coenzymes thiamine pyrophosphate (TPP), which is used in decarboxylation reactions (pork and legumes are good sources of this)

NADH

____generated by glyceraldehyde 3-phosphate dehydrogenase is oxidized by alchol dehydrogenase, regenerating NAD+

reoxidized to NAD+

the NADH produced by the glyceraldehyde 3-phosphate dehydrogenase reaction must be ____ for the glycolytic pathway to continue.

alcohol dehydrogenase

in alcoholic fermentation, ____ oxidizes NADH and generates ethanol

lactate dehydrogenase

NADH can also be oxidized by converting pyruvate to lactate in a reaction catalyzed by _____

lactic acid fermentation

the conversion of glucose into 2 molecules of lactate

glucose + 2Pi + 2ADP → 2lactate + 2ATP + 2H2O

lactic acid and regenerate NAD+

in lactic acid fermentation, lactate dehydrogenase oxidizes NADH to produce____-

glycolytic intermediates

fructose from table sugar or high-fructose corn sytrup and galatose from milk sugar are converted into this

fructose and galatose

these sugars convert to metabolites of the glycolytic pathway

phosphofructokinase (PFK)

fructose leads to type II diabetes because of the manner in which fructose in processed in the liver, the key regulatory eneryme of glycolysis is by-passed/ not regulated

fats

excess acetyl CoA synthesized and converted to ___

galactose-glucose conversion pathway

galatose is converted into glucose 6 phosphate by the _____ which begins with the phosphotylation of galatose by galactokinase

galactose

is highly toxic if transferse is missing

galactosemia

results if galactose 1-phosphate uridyl transferase activity is deficient; symptons include failure to thrive, jaundice, and liver enlargment that can lead to cirrhosis; cataracts may form

cataracts

a clouding of the lends due to water accumulation, form because the galatose is converted into galactitol

galactitol

is osmotically active and causes water to diffuse inot lens; poorly metabolized

phosphorylated and metabolized

notice all sugars are ____ by entry into the glycolytic pathway

reducatse enzyme

high levels of glucose present in the lends of the eye causes the lens to swell which affects clarity of vision. ____ reduces glucose into sorbitol (polyol pathway) that causes the lends to become less clear and more opaque (leads to cataract formation)

lactase

a deficiency of this casues lactose intolerance

lactose intolerance

when lactose can not be broken down into galactose and glucose wht lactic acid ferments by bacteria which draws the water in the intestine