Biochemistry Exam 2

Write the net equation of anaerobic glycolysis as it occurs in muscle tissue.

Glucose + 2 ADP + 2 Pi--> 2 lactate + 2 ATP + 2 H2O + 2 H+

overall reaction of glycolysis

Glucose + 2NAD+ +2ADP + 2Pi -> 2 Pyruvate + 2NADH +2ATP + 2H2O + 4H+

Three reactions in glycolysis operate far from equilibrium and are potential sites for major flux control. List the three enzymes and discuss why each enzyme is or is not the major control site of glycolysis.

Hexokinase catalyzes the first exergonic step of glycolysis. However, when the source of glucose-6-phosphate is from glycogen in skeletal muscle, rather than free glucose, the hexokinase reaction is not required. Pyruvate kinase catalyzes the last reaction of glycolysis and is therefore not a good candidate for regulation of the entire pathway.Phosphofructokinase catalyzes a very exergonic reaction at Step 3. This is near the beginning of the pathway, but after the entry of glucose-6-phosphate from glycogen, so it can regulate the entire pathway.

what are stages for extracting energy from food

1) Large food molecules are broken down into smaller units, such as amino acids, carbohydrates, and fatty acids. 2) The small units are further broken down to a subset of small molecules that are critical to metabolism, such as acetyl CoA. 3) ATP is produced by oxidation of the acetyl units.

catabolism produces what compounds for energy utilization?

1. ATP 2. other compounds with high phosphoryl transfer potential 3. reducing power (NADPH, NADH, FADH2)

How many high energy bond(s) does ADP have? A. 1 b. 2 c. 3 d. 0

A

What are the principal ways by which metabolic pathways are regulated? a. The amount of enzymes, the enzyme catalytic activities, and substrate accessibility & supply b. Enzyme synthesis, degradation, gene expression c. Allosteric regulation, reversable covalent modification, phopsphorylation d. Allosteric regulation, phopsphorylation, substrate accessibility & supply

A

What is substrate level phosphorylation?

ATP synthesis when the phosphate donor is a substrate with high phosphoryl transfer potential

During glycolysis, the steps between glucose and formation of the triose phosphates: A) consume two ATP and two NADH molecules. B) consume two ATP molecules. C) produce two ADP and two NAD+ molecules. D) produce two ATP and two NADH molecules. E) consume two NADH molecules.

B

In which of the following metabolic conversions is ATP "consumed" during glycolysis? A) 1,3-Bisphosphoglycerate = 3-phosphoglycerate B) Glucose =glucose-6-phosphate C) 2-Phosphoglycerate = 3-phosphoglycerate D) Fructose-1,6-bisphosphate = dihydroxyacetone phosphate + glyceraldehyde-3-phosphate E) Glucose-6-phosphate = fructose-6-phosphate

B

Which is the net equation of glycolysis as it occurs in aerobic cells such as brain cells? A) Glucose + 2 ATP = 2 lactate + 2 ADP + 2 Pi B) Glucose + 2 ADP + 2 Pi + 2 NAD+= 2 pyruvate + 2 ATP + 2 NADH + 4 H+ C) Glucose + 2 ADP + 2 Pi= 2 lactate + 2 ATP + 2 H+ D) Glucose + 2 ADP + 2 Pi= 2 CH3CH2OH + 2 CO2 + 2 ATP E) Glucose + 2 ADP + 2 Pi + 2 NAD+= 2 lactate + 2 ATP + 2 NADH + 4 H+

B

Which of the following are produced in anabolism? a. NAD+ b. NADPH c. ADP + Pi d. FADH2 e. ATP

C

feed-forward activation

Metabolite early in the pathway activates an enzyme further down the pathway

Why do muscles need to generate ATP under aerobic and anaerobic conditions?

Muscles initially function aerobically. However, when bursts of energy are required, the oxygen supply does not meet the demand. In order to generate sufficient ATP for energy demands the muscle depends on activity-dependent anaerobiosis.

galactose ( 6 aldose)

a component of lactose in milk

Phosphofructokinase (PFK) regulated

a key rate-limiting enzyme of the anaerobic glycolytic energy system - high levels of ATP inhibit its activity - high levels of AMP increase its activity a decrease in ATP/AMP = low cell energy= stimulates glycolysis

lactate fermentation: during strenuous exercise...

buildup of lactate in tissues as the oxygen supply becomes inadequate decrease in pH causes muscle pain and cramps also decreases blood pH - breath heavy and deep

the two processes of metabolism are linked by what?

by producing and consuming ATP and reducing power

how are metabolites with high phosphoryl transfer potential involved in metabolism?

can donate phosphoryl group to ADP to form ATP

major components of cell walls

cellulose, hemicellulose, lignin, pectin polysaccharides

how're metabolic processes unified?

common molecules such as ATP and oxidation/reduction rxns

deoxyribose (5 aldose)

component of dna

ribose (5 aldose)

component of rna, coenzymes

Polysaccharides

composed of many monosaccharide units 1. starch (plants) = amylose a(1,4) and amylopectin a (1,4) & a (1,6) 2. glycogen (animals) a (1,4) & a (1,6) 3. cellulose (plants) B (1, 4)

Gluconeogenesis

consumes 6 high energy bonds in making one glucose from 2 pyruvate 2 pyruvate + 4 ATP + 2 GTP +2NADH +6 H20--> GLUCOSE +4 ADP + 2 GDP +6 Pi +2NAD+ +2H+ place of synthesis : liver endergonic process that requires energy glycolysis is exergonic

why is atp a high energy compound?

contains two phosphoanhydride bonds that are unstable due to electrostatic repulsion, resonance instability, and stabilization due to hydration

anomer (a & b)

cyclic sugars that differ only in positions of substituents at the hemiacetal or hemiketal carbon a = the -OH group attached to the hemiacetal or hemiketal C is below the plane of the ring B= the -OH groups is above the plane of the ring

artery blockage

decreases oxygen supply, increasing glycolysis and lactate levels, produces cramps, stops beating (cardiac arrest)

relationship between electromotive force and delta G of reaction?

delta G = -nFe

Most monosaccharides are chiral compounds

enantiomers - mirror images diasteromers - different configurations but not mirror images, one or more stereocenters epimers - differ from each other by one stereocenter **D-sugars predominate in nature

what is the purpose/ use of glycolysis

energy production (ATP, NADH) a. substrate level phosphorylation : formation of atp under anaerobic conditions b. produce substrate for oxidative phosphorylation (respiration)

phosphagens

energy-rich storage molecules in animal muscle ex. phosphocreatine & phosphoarginine = phosphoamides have higher group-transfer potential than atp , used to replenish atp when needed via creatine kinase reaction

why are two different e- carriers , nad+ and fad, involved in metabolism?

fad is involved in one- electron transfers and two-electrons transfers; higher standard reduction potential than nad+ nad+ is involved in ONLY two- electron transfers

Regulation of Gluconeogenesis

fructose - 1,6- bisphosphate is the key enzyme regulation : atp high , enzyme activity increases, and gluconeogenesis increases amp levels high (atp low), enzyme activity increase, glycolysis increases

Fructose (6 Ketose)

fruit sugar, honey syrup

what two 3-carbon molecules are generated by the cleavage of fructose -1,6 bisphosphate?

glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

how many atp and nadh are produced from one glucose molecule?

4 atp 2 nadh

why are the vitamins niacin (b3) and riboflavin (b2) necessary for metabolism?

these are NOT synthesized in humans, but are components of coenzymes requires for redox reactions in metabolism niacin - nad+ riboflavin - fad

why is fermentation important to the cell?

to regenerate nad+ so glycolysis can continue

disaccharides

two simple sugar linked by a glycosidic bond ex. lactose (milk sugar) -- reducing sugar maltose (malt sugar) -- reducing sugar sucrose (cane sugar) -- nonreducing sugar

NAD+ is required for the oxidative step glycolysis. Briefly discuss how NAD+ is regenerated from NADH under aerobic and anaerobic conditions in skeletal muscle.

under aerobic conditions, electrons pass from the reduced coenzyme (NADH) through a series of electron carriers to oxygen, the final oxidizing agent. This regenerates the oxidized coenzyme (NAD+). Under anaerobic conditions, the electrons of NADH are transferred to pyruvate to form lactate, the end-product of glycolysis under anaerobic conditions.

cori cycle

working muscles utilize glucose to produce lactate, which is released to the blood, transported to the liver and converted back to glucose in the liver. glucose in the liver is released to the blood and transported back to the muscle. glucose usage and replenishment

4 ways cells control/ regulate flux?

1. allosteric control of rate- determining step 2. covalent modification of enzymes to activate or deactivate them 3. substrate cycles in which two opposing reactions are catalyzed by different enzymes 4. genetic control to alter amount of enzymes in response to cellular needs

features of metabolic pathways

1. forms = linear , cyclic, spiral 2. discrete steps = multistep pathways w multiple enzymes 3. regulated = 1) the amount of enzymes - synthesis/degradation (transcription/ expression) 2) enzyme catalytic activities - allosteric regulation , reversible covalent modification (de- phosphorylation) 3) accessibility and supply of substrates 4. compartmentalized - permits separate pools of metabolites within a cell, simultaneous operation of metabolic paths, high local concentrations of metabolites, coordination regulation of enzymes

carb nomenclature

1. functional group = aldose or ketose 2. # of carbons = 3c - triose , 4c - tetrose , 5c - pentose, 6c - hexose

what does a high-energy compound mean?

1. greater free energy of hydrolysis than a typical compound 2. contains one or more very reactive bonds that require less energy to break

properties of chiral molecules

1. physical properties of enantiomers are identical except different optical activity (rotate the plane of polarization of light) 2. enantiomers have identical chemical properties toward all reactions whose molecules are achiral 3. enantiomers react differently toward reactants whose molecules are chiral

common properties of lactate and alcohol fermentation

1. pyruvate as a substrate 2. oxidize nadh to nad+ 3. self-limiting process

how many net atp molecules are produced from 1 glucose under anaerobic conditions

2 atp

importance of ATPs intermediate phosphoryl group-transfer potential to energy metabolism in cell?

ATP formed from ADP by transfer of phosphoryl groups from compounds with higher- phosphoryl group transfer potentials. The ATP then transfers a phosphoryl group to compounds with lower phosphoryl group-transfer potentials

How is glycolysis maintained under anaerobic conditions?

Pyruvate can be reduced to either lactate or ethanol, and this reaction is accompanied by the oxidation of NADH to regenerate NAD+

Accumulation of which of the following compounds is the cause of stiff and sore muscle after vigorous exercise? a. pyruvate b. acetyl-CoA c. ethanol d. lactic acid e. glycerate

D

In skeletal muscle cells, the NADH that is produced by glycolysis under anaerobic conditions (vigorous exercise) is regenerated to NAD+ by the conversion of: A) acetaldehyde to ethanol. B) lactate to pyruvate. C) phosphoenolpyruvate to pyruvate. D) pyruvate to lactate. E) glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate.

D

Which of the following are produced in catabolism? a. NAD+ b. NADP+ c. FAD d. FADH2 e. all the above

D

Which of the following is at a higher level of oxidation than CH3CHO? A) CH3CH2OH B) CH3CH3 C) CH2=CH2 D) CH3CO2H E) none of the above

D

Which of the following metabolic conversions is considered to be the major control point of glycolysis? A) Fructose-1,6-bisphosphate --> dihydroxyacetone phosphate + glyceraldehyde-3-phosphate B) Glucose --> glucose-6-phosphate C) 2-phosphoglyerate --> phosphoenolpyruvate D) Fructose-6-phosphate --> fructose-1,6-bisphosphate E) pyruvate --> lactate

D

. Molecule(s) with a higher phosphoryl transfer potential than ATP: a. phosphoenolpyruvate b. creatine phosphate c. 1,3 bis-phosphoglycerate d. a and b e. a, b, and c

E

In eukaryotes, the enzymes that catalyze the reactions of glycolysis are located in: A) the cell nucleus. B) the endoplasmic reticulum. C) the mitochondria. D) the lysosomes. E) the cytosol.

E

The major purpose(s) for which organisms require energy: a. performance of mechanical work b. active transport c. synthesis of biomolecules d. a and c e. d. a, b, and c

E

What is the purpose of phosphorylating glucose in cytosol? a. to trap glucose in the cell b. to destabilize glucose and facilitate the next series of metabolic steps c. to convert it to a more soluble form d. all of the above e. a and b

E

Which of the following are used in biosynthesis processes? a. NADH b. NADPH c. ATP d. all the above e. a and c f. b and c

F

The ethanol formed naturally by alcoholic fermentation is usually 5-12%, which is much lower than the concentration in distilled liquors. Why?

Organisms such as yeast, which are responsible for the ethanol production, can only tolerate low levels of alcohol. Higher levels would be toxic to live cells.

Why is it more sensible for phosphofructokinase to be an important control step, rather than hexokinase?

Phosphofructokinase catalyzes the first committed step in the glycolytic pathway. At this point, the molecule is committed to entering the glycolytic path. In contrast, production of G6P is the first step in many different paths. Thus, glycolytic control would not be maintained by tight regulation of hexokinase.

lactate fermentation

Pyruvate --(NADH-> NAD)-> Lactate

phosphoryl-group - transfer potential

The ability of a compound to transfer its phosphoryl group high-energy compounds : have group transfer potentials equal to or greater than that of ATP ex. phosphocreatine, phosphoenolpyruvate low energy compounds: have group transfer potentials less than that of atp ex. glucose- 6 phosphate

how does glycolysis produce energy?

substrate level phosphorylation: formation of ATP by transferring a phosphate group from a substrate of a reaction to ADP oxidative phosphorylation : the process in which ATP is formed as a result of the transfer of electrons from NADH or FADH 2 to O 2 by a series of electron carriers.

sucrose

a1 --> B2 of -D-glucose and -D-fructose nonreducing sugar because both -OH groups are used in glycosidic bond formation

carbohydrate general structure

aldehydes or ketones with at least two hydroxyl (OH-) groups = aldoses and ketoses composed of C,H, O formula = (CH2O)n n>=3 simplest carbs = glyceraldehyde & dihydroxyacetone`

glycolysis

an ANAEROBIC pathway in which 1 glucose (6C) is converted to 2 pyruvate (3C) molecules with production of 2 ATP and 2 NADH

metabolism as two processes, how are they unified?

anabolism and catabolism unified through production and consumption of ATP and reducing powers such as NAD(P)H. Catabolism degrades molecules to produce ATP and reducing power. Anabolism uses ATP and reducing power to synthesize molecules.

proteoglycans

animal cell surface and in the extracellular matrix; unbranched heterglycans of repeating disaccharides

lignin

aromatic polymers resulting from oxidative coupling of 4 hydroxylphenylpropanoids

gluconeogenesis

synthesis of glucose from noncarb precursors such as lactate, glycerol, and amino acids noncarbs (pyruvate) ---> glucose

glucose (6 aldose)

grape sugar, blood sugar, dextose

glycoside formation

hemiacetal/ hemiketal +alcohol --> acetal/ ketal involves joining the hydroxyl group of the hemiacetal and another hydroxyl group of another compound by dehydration

two regulatory steps in glycolysis

hexokinase --> glucose+atp = glucose -6 - pi +adp pyruvate kinase --> phosphoenolpyruvate +adp = pyruvate +atp

glycolysis as two stages:

hexose stage: 2 atp consumed per glucose triose stage: 4 atp are produced per glucose net : 2 atp

which metabolic reaction is most commonly used to break down food?

hydrolysis reactions

lactose

lactose B (1,4) reducing sugar because of the presence of a free hemiacetal - OH

peptidoglycans

major component of bacterial cell walls composed of alternating n-acetylglucosamine and n-acetylmuramic acid

maltose

maltose a (1,4) reducing sugar because of the presence of a free hemiacetal -OH two D-glucose

cellulose

most abundant , key source for biomass-based renewable energy structural component of plant cell walls human cannot digest bc lack of cellulase

Briefly discuss the hypothesis that increased consumption of high fructose corn syrup is linked to the increase of obesity.

n the liver, fructose is converted to fructose-1-phosphate by fructokinase. Fructose-1-phosphate is then cleaved to glyceraldehyde and dihydroxyacetone phosphate by a specific aldolase. These products are then converted to glyceraldehyde-3-phosphate. These reactions bypass phosphofructokinase, the key regulatory step of glycolysis. Under normal conditions, elevated ATP would decrease the glycolytic flux. However, high fructose in the diet bypasses this control, and the glycolytic flux can be directed toward fat synthesis instead.

reduced coenzymes conserve energy from biological oxidations

nadh used for atp synthesis nadph used for reductive biosynthesis fadh2

why are vitamins niacin and riboflavin necessary?

niacin is a component of NAD+ and riboflavin is a component of FAD --- components of redox reactions

glycoproteins

oligosaccharide chains exhibit great variability in sugar sequence and composition

where does body's energy come from?

oxidation of carbon releases energy most energy = methane > methanol> formaldehyde> formic acid> co2 = least energy

ATP

the cellular energy currency --- energy released from foods ATP contains two high energy bonds, and hydrolysis of ATP yields energy

major differences between primary and secondary cell walls

primary cell wall is made of mostly pectin polysaccharides, whereas secondary cell wall is made of cellulose, hemicellulose, and lignin

feedback inhibition

product of a pathway controls the rate of its own synthesis by inhibiting an early step

dietary fibers

provide bulk which help the body get rid of waste, give feeling of fullness while providing few calories reduce the risk of colon cacer, heart attack, adult diabetes, affect microbiota

what is atp hydrolysis used for in metabolic reactions

provides energy for endergonic processes

what is atp used for in metabolic reactions?

provides energy to drive endergonic processes by cleavage of both phosphoanhydride bonds

advantage of pyrophosphate cleavage of ATP

pyrophosphate cleavage of ATP produces PPi as one of the end products. then, inorganic pyrophosphatase catalyzes the exergonic hydrolysis of PPi -> 2Pi --- supplies sufficient free energy to drive endergonic process

what happens to pyruvate under aerobic conditions?

pyruvate + coenzyme a +nad+ = acetyl-coA +co2 +nadh glucose -> 2 pyruvate ->2 acetyl coa-> 6CO2 + 36 ATP

vitamin supplements for low carb diets contain higher amounts of biotin, why?

pyruvate decarboxylase requires biotin. high levels of supplemental biotin would promote glucose synthesis

alcohol fermentation

pyruvate is converted to ethanol in two steps: 1. pyruvate to acetaldehyde via pyruvate decarboxylase 2. acetaldehyde to ethanol via alcohol dehydrogenase

how is reduction potential related to free- energy

reduction potential = measure of its thermodynamic reactivity n = # of e transferred F= faraday constand 96.48 kj/v e = electrical potential difference = acceptor - donor