BCHM-3050 Lecture Notes - Lecture 12: Schiff Base, Aldehyde, Cyclic Adenosine Monophosphate

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Chapter 12: Carbohydrate Metabolism

Overview of Carbohydrate Catabolic and Anabolic Processes

The breakdown of glucose via glycolysis is the beginning of the generation of a large amount of ATP

per molecule of glucose.

Gluconeogenesis includes the synthesis of polysaccharides (glycogen)

Catabolism: the process of breaking large, complex macromolecules down to their simplest parts.

oEnergy is released

oReactions are oxidative

Anabolism: Opposite of catabolism. The building up and synthesis of large macromolecules and the

storing of energy.

oEnergy is required

oReactions are reductive

**Glycolysis as a whole is a catabolic reaction**

What to Know for Each Reaction

Major structures of substrates/products

Enzymes (name and abbreviations)

Basic Thermodynamics

Alpha Glucose

6 carbons

Cyclic

OH on the C#1

Alpha Fructose

Furanose (5 membered ring)

Anomeric center is at C#2

Glycolysis Overview

Phase 1: Energy Investment

oStart with glucose and prime it for a cleavage reaction by an aldilase. To cleave this product,

you have to add phosphate groups, and to do this, you have to have energy. Product of one

reaction becomes the substrate of the next reaction.

oGlyceraldehyde moves on from #6.

Phase 2: Energy Generation

oUse energy invested in the first phase to make energy.

Glycolysis: Reaction 1

Hexokinase (HK) – 1st ATP investment

oAlpha D glucose is converted to alpha glucose 6 phosphate (G6P).

oΔ G = -18.4 kJ/mol

o**IS THE FIRST IRREVERSIBLE PROCESS**

oMagnesium helps to coordinate and help with cleavage.

oIs a phosphorylation reaction and TAKES ENERGY – ATP helps to power the cleavage.

The intracellular concentrations of substrates/products with VARY – meaning that the ΔG will vary.

Hexokinase isoforms have different substrate specificities and binding affinities.

oBroad Substrate Specificity: fructose/mannose. Low Km for isoforms 1, 2, and 3.

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** Low Km = high specificity **

oHigh Km for hexokinase IV (glucokinase)

Hexokinase IV contributes toward the role of the liver as a glucostat, which allows the liver to adjust

the rate of glucose utilization in response to varying blood glucose levels.

Glycolysis: Reaction 2

Glucose-6-Phosphate Isomerase

oG6P is isomerized to fructose-6-phosphate. Phosphate group is still on C#6, and isomerization is

from pyranose to a furanose ring (constitutional isomers)

oBreak oxygen bond and move to #2 Carbon.

oGo from hemiacetal group to hemiketal group.

oBecause we are breaking the bond, it can be alpha or beta with rotation.

IS REVERSIBLE

oΔG = +1.7 kJ/mol

Reaction 2/3 sets the stage for a symmetric aldol cleavage (RXN 4)

Glycolysis: Reaction 3

Phosphofructokinase-1 (PFK1) ~ (2nd ATP Investment)

oInvests another ATP molecule. PFK1 takes the fructose 6 phosphate (F6P) and add on a second

phosphate group to the #1 carbon of the fructose to make Fructose 1,6 bisphosphate (FBP)

oΔG = -15.9 kJ/mol

PFK1 (allosteric enzyme) is a major control point for glycolysis, and is referred to as a committed step

for glycolysis. **

PFK-1

Is one of the MOST IMPORTANT control/regulation points of glycolysis.

oThe PFK enzyme is a homotetramer (4 identical subunits)

oIt has 2 active sites and 4 allosteric sites

ATP is also an allosteric effector

o(ATP)/(ADP) or (ATP)/(AMP) ratios INCREASE

Its forward product (F-1,6-bP) acts as a non allosteric inhibitor and helps drive the reverse reaction for

gluconeogenesis via the gluconeogenic enzyme fructose-1,6-bisphophatase.

Activators (allosteric):

oADP

oAMP

oFruc-2,6-bP (feedforward stimulation)

Inhibitors (allosteric):

oATP

oPEP

oLOW pH

F2,6BP

Activates glycolysis and inhibits gluconeogenesis

Product of 2nd step in glycolysis is F6P.

PFK-2 are distinct from the enzymes found in glycolysis and gluconeogenesis.

PFK-2/FBPase-2

Regulating enzymes are regulated themselves.

BIFUNCTIONAL ENZYMES

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Document Summary

The breakdown of glucose via glycolysis is the beginning of the generation of a large amount of atp per molecule of glucose. Gluconeogenesis includes the synthesis of polysaccharides (glycogen) Catabolism: the process of breaking large, complex macromolecules down to their simplest parts: energy is released, reactions are oxidative. The building up and synthesis of large macromolecules and the storing of energy: energy is required, reactions are reductive. **glycolysis as a whole is a catabolic reaction** Phase 1: energy investment: start with glucose and prime it for a cleavage reaction by an aldilase. To cleave this product, you have to add phosphate groups, and to do this, you have to have energy. Product of one reaction becomes the substrate of the next reaction: glyceraldehyde moves on from #6. Phase 2: energy generation: use energy invested in the first phase to make energy. The intracellular concentrations of substrates/products with vary meaning that the g will vary.

Related Questions

1. C6H12O6 + 6O2 Ã 6CO2 + 6H2O Glucose is being _____ to _____ and oxygen is being _____ to _____. a. oxidized; carbon dioxide; reduced; water b. oxidized; water; reduced; carbon dioxide Incorrect c. reduced; water; oxidized; carbon dioxide d. reduced; carbon dioxide; oxidized; water

2. Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP? a. the citric acid cycle Incorrect b. glycolysis c. the digestion of starch to glucose d. oxidative phosphorylation

3. Which of the following is a catabolic pathway? a. gluconeogenesis b. production of starch Incorrect c. glycolysis d. production of glycogen

4. Per molecule, the oxidation of a fatty acid results in _____ energy storage than the oxidation of glucose. a. the same b. less Incorrect c. more d. None of the above; fatty acids cannot be oxidized.

5. Of the eight reactions in the citric acid cycle, how many are oxidation-reduction reactions? a. one b. two c. three d. four e. five

6. The process of glycolysis transfers the energy in sugar molecules into the stored energy of activated carriers such as ATP and NADH. Which statement is true about glycolysis? a. Only eukaryotic organisms do glycolysis. b. The ten reactions of glycolysis are identical in all eukaryotic cells, but are different in prokaryotic cells due to their diverse metabolic strategies. Incorrect c. The ten reactions of glycolysis are identical in almost all living organisms on the planet. d. There are many ways to oxidize glucose and transfer energy into activated carriers; the diversity of organisms on the planet is reflected in the diversity of their mechanisms of glycolysis.

7. Referring to the sentence completed in #13 above, the purpose of the latter reaction (in active muscle cells) is to _____. a. accumulate lactic acid in the cell, which provides additional energy for the production of ATP Incorrect b. slow down glycolysis until oxygen becomes available again c. accelerate the Krebs cycle, which will restore the oxygen supply d. regenerate NAD+ so that glycolysis can continue in the absence of oxygen

8. What are the products of the citric acid cycle? a. carbon dioxide, NADH, FADH2 and GTP b. carbon dioxide, NAD+, FAD and GTP c. NADH, FADH2, and acetyl CoA Incorrect d. carbon dioxide and water

9. Which statement is true about enzymes? a. Enzymes catalyze chemical reactions because they make inherently endergonic reactions exergonic. b. Each enzyme in a cell can catalyze many different chemical reactions involving chemically different substrates. Incorrect c. Enzymes can only catalyze reactions in one direction. d. After catalyzing a reaction, an enzyme is permanently altered and can no longer bind substrate. e. None of the above is true. 1

10. âG measures the change in free energy in a system as it converts reactant (Y) into product (X). When [X] = [Y], âG is equal to _____. a. RT b. ÎGÂ° + RT c. ÎGÂ° d. ln [X]/[Y]

11. The âGÂ° for the hydrolysis of ATP is -7.3 kcal/mol. What conditions in the cell would lead to a âG for ATP hydrolysis of -11 kcal/mol? a. An increase in the ATP/ADP ratio b. An increase in anabolic activity in the cell c. Transport of ATP out of the compartment where the reaction is occurring Incorrect d. A decrease in the ATP/ADP ratio

12. In the first reaction of glycolysis, a phosphate transferred from ATP to a glucose molecule to produce glucose-6-phosphate and ADP. Under conditions existing in the cell, the free energy change for this reaction is -8.0 kcal/mole. Which of the following statements is true? Recall that the âGÂ° for the hydrolysis of ATP is -7.3 kcal/mol. a. Glucose concentrations in the cell are always low, making this reaction more favorable than would be expected. b. This reaction is less favorable than would be expected, given the âGÂ° of ATP hydrolysis. c. Glucose-6-P concentrations in the cell are very low relative to glucose concentrations, making the reaction more favorable than would be expected. d. The âGÂ° for the addition of a phosphate to glucose must be -0.7 kcal/mole.

13. Protein E can bind to two different proteins, S and I. The binding reactions are described by the following equations and values: E + S --> ES Keq for ES = 10 E + I> EI Keq for EI = 2 Given the equilibrium constant values, which one of the following statements is true? a. When S is present in excess, no I molecules will bind to E. b. E binds I more tightly than S. c. The binding energy of the ES interaction is greater than that of the EI interaction. d. Changing an amino acid on the binding surface of I from a basic amino acid to an acidic one will probably make the free energy of association with E more negative.

Biochemistry Review Questions

What is the classification of the compound shown here?

A) an aldohexose B) a ketohexose C) an aldopentose D) a ketopentose

2. In a disaccharide, the CâO bond that joins the two rings together is called _____.

A) a hemiacetal B) a glycosidic linkage C) an alditol D) an anomer

3. What is the structure of amylopectin?

A) unbranched skeleton of glucose molecules joined by 1ï®4-ï¡-glycoside linkages

B) branched skeleton of glucose molecules joined by 1ï®4-ï¡-glycoside linkages

C) unbranched skeleton of glucose molecules joined by 1ï®4-ï¢-glycoside linkages

D) branched skeleton of glucose molecules joined by 1ï®4-ï¢-glycoside linkages

4. In a disaccharide, the CâO bond that joins the two rings together is called _____.

A) a hemiacetal B) a glycosidic linkage C) an alditol D) an anomer

5. Which type of linkage between the two rings is in the structure shown?

A) 1Â®4-b-glycoside linkage D) 1Â®1-a-glycoside linkage

B) 1Â®4-a-glycoside linkage E) 1Â®2-b-glycoside linkage

C) 1Â®1-b-glycoside linkage

6. What is the structure of cellulose?

A) unbranched skeleton of glucose molecules joined by 1Â®4-a-glycoside linkages

B) branched skeleton of glucose molecules joined by 1Â®4-a-glycoside linkages

C) unbranched skeleton of glucose molecules joined by 1Â®4-b-glycoside linkages

D) branched skeleton of glucose molecules joined by 1Â®4-b-glycoside linkages

7. Which amino acid is a basic amino acid?

A) serine B) arginine C) cysteine D) alanine E) valine

8. What monosaccharide is found in cellulose, starch, and glycogen?

A) glucose

B) galactose

C) N-acetyl-D-glucosamine

D) fructose

E) More than one of the monosaccharides above is found in cellulose, starch, and glycogen.

9. Which is not a reducing sugar?

A) glucose B) fructose C) sucrose D) galactose E) an aldopentose

10. Sucrose contains one _____ unit and one _____ unit.

11. What is the particular sequence of amino acids of a protein that are joined together by peptide bonds called?

A) the primary structure of a protein C) the tertiary structure of a protein

B) the secondary structure of a protein D) the quaternary structure of a protein

12. What is the charge on an amino acid at a pH below its pI?

A) positive

B) neutral

C) negative

D) The charge or lack of charge varies depending on the amino acid.

13. What is the C-terminal amino acid in the tetrapeptide glycylalanyisoleucylmethionine?

A) alanine B) glycine C) methionine D) isoleucine

14. How many different dipeptides can be formed when one valine reacts with one glycine?

A) 1 B) 2 C) 3 D) 4

15. What is the process of altering the shape of a protein without breaking the amide bonds that form the primary structure?

A) hydrolysis B) competitive inhibition C) denaturation D) oxidation

16. Which of the following compounds is an enzyme?

A) glucose C) N-acetyl-D-glucosamine

B) triosephosphate isomerase D) dihydrofolate

17. What is a zymogen?

A) an amino acid with a neutral charge

B) inactive precursor of an enzyme

C) a molecule that causes an enzyme to lose activity

D) a nonprotein organic molecule needed for an enzyme-catalyzed reaction to occur

18. Which of the following will the cause the rate of enzyme activity to first increase and then level off?

increasing the enzyme concentration

increasing the temperature

increasing the substrate concentration

increasing the pH

19. Which of the following make up a nucleoside?

base + sugar

base + phosphate + sugar

base + phosphate

phosphate + sugar

20. Transcription corresponds to which of the following?

the separation of the two strands of DNA to enable the formation of two identical DNA molecules

the transfer of genetic information from DNA to RNA

the transfer of genetic information from RNA to DNA

the use of genetic information to synthesize a specific protein

21. Each individual tRNA contains _____

A) a base sequence that is identical to the informational strand of DNA.

B) the sequence of codons that determines the order of amino acids in the protein.

C) an anticodon of three nucleotides that is complementary to the codon in mRNA and identifies individual amino acids.

D) an anticodon complementary to any of the three stop codons.

22. Where does energy production occur in animal cells?

A) cell membrane B) cytoplasm C) mitochondria D) nucleus

23. How many molecules of CO2 are produced for each turn of the citric acid cycle?

A) 0 B) 1 C) 2 D) 3 E) 4

25. Which is not a reaction found in stage [2] of catabolism?

A) fatty acid oxidation C) oxidative phosphorylation

B) glycolysis D) amino acid catabolism

26. What is the classification of the reaction shown?

A) oxidation D) hydrolysis

B) reduction E) isomerization

C) decarboxylation

27. Synthesis of glucose from amino acids is called

A) Glycolysis C) Gluconeogensis

B) Glycogenesis D) Hydrolysis

28. The synthesis of large molecules from smaller ones in the body is referred to as

A) catabolism C) Ketogenesis

B) anabolism D)glycolysis

29. The nucleic acid base found in the mRNA but not in DNA is

A) Adenine C) Uracil

B) Guanine D) Cytosine

30. DNA rich in A-T base pairs have

A) 1 hydrogen bond C) 2 hydrogen bonds

B) 3 hydrogen bonds D) 4 hydrogen bonds

31. Where does the energy production occur in the cell?

A) Ribosome C) Mitochondria

B) Nucleus D) Cytoplasm

32. Where does the protein synthesis occur in the cell?

A) Ribosome C) Mitochondria

B) Nucleus D) Cytoplasm

33. In the process of transcription, the flow of genetic information is from

A) DNA to DNA C) DNA to protein

B) RNA to protein D) DNA to RNA

34. Ammonium ions are converted to non-toxic nitrogen containing compounds through

A) Amino acid metabolism C) Urea cycle

B) Citric acid cycle D) transamination

35. In protein structure, B-pleated cheats are examples of

A) Primary structure C) Secondary structure

B) Tertiary structure D) Quaternary structure

36. Lactose is a disaccharide formed of

A) Glucose + fructose C) Glucose + galactose

B) Glucose + glucose D) Fructose + galactose

37. Saponification is

A) Hydrolysis of fats by strong base

B) Hydrolysis of glycerol by lipases

C) Esterification

D) Oxidation reaction

38. The connection between amino acid residues in molecules of protein is

A) glycosidic linkage C) peptide linakge

C) ether linkage D) phosphodiester linkage

39. Polyunsaturated fatty acids are generally

A) Oil at room temperature C) Solid at room temperature

B) Semisolid at room temperature D) All of the above

40. Maximum energy is produced by

A) Carbohydrates C) Lipids

B) Proteins D) Nucleic acids

41. A polynucleotide contains _____

A) one free phosphate group at the 5' end.

B) a backbone of alternating sugar and base groups.

C) one free phosphate group at the 1' end.

D) one free OH group at the 5' end.

42. How many molecules of CO2 are produced for each turn of the citric acid cycle?

A) 0 B) 1 C) 2 D) 3 E) 4

43. How many molecules of GTP are produced for each turn of the citric acid cycle?

A) 0 B) 1 C) 2 D) 3 E) 4

44. Which is the enzyme that hydrolyzes triacylglycerols?

A) acetyl CoA D) lipase

B) protease pepsin E) succinate dehydrogenase

C) amylase

BCHM-3050 Lecture Notes - Lecture 12: Schiff Base, Aldehyde, Cyclic Adenosine Monophosphate

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