BCH210H1 Lecture 27: Lecture 27

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amethystfly536

25 May 2018

School

UTSG

Department

Biochemical Engineering and Applied Chemistry

Course

BCH210H1

Professor

Stavroula Andreopoulos

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Lecture 27: Glycolysis and Enzyme Inhibition

• When phosphocreatine levels fall (bind to phosphate and act as storage to replenish ATP), additional ATP

production is required

• Glycogen breakdown generates glucose 1-phosphate (must be converted to G6P for glycolysis)

• Glucose enters muscle cells from the blood using GLUT4 transporters

- GLUT4 has 12 transmembrane helices and forms a binding site for glucose transport

• Glucose provides a substrate for the glycolysis that will lead to ATP production in muscle (and other cells)

Glycolysis

• Stage 1 – first five steps (energy input phase/ stages that need energy to

generate a lot more energy)

- Require 2 ATP for glucose

- At the end of stage 1, 2 GAP (glyceraldehyde 3-phosphate)

• Stage 2 – last five steps (generate ATP and NADH)

- Generates 4 ATPs (stage 2 runs twice) and NADHs

- At the end of stage 2 is 2 pyruvate

• All takes place in cytoplasm which will head to mitochondria if O2 is available

- In mitochondria - further oxidation and production of waste products (CO2) and

ATP through oxidative phosphorylation

• Under cellular conditions, concentration of substrates and products can change

the free energy for reaction

Free energy of glycolysis

• Negative overall pathway – favorable under standard conditions

• Negative overall pathway (greater change in free energy) for actual

free energy

- Some have VERY big negative slopes (1,3,10) - regulated

- 2.4.5.6.7.8.9 are flat - reversible

Glycolysis and beyond

• Glucose enters the glycolytic pathway (10 enzymes) found in the cytoplasm

• Glucose (6C) is converted into 2 pyruvate (3C) and energy release of 2 ATP (net)

• If O2 is available, pyruvate enters mitochondria and is converted to acetyl CoA

• Further oxidation takes place in the mitochondrial matrix and a lot more ATP is made

Glycolysis Regulation (Favorable with negative free energy changes)

1. Hexokinase can be inhibited by buildup of its product (product inhibition), glucose-6-phosphate

3. PFK-1 inhibited by the amount of ATP, and activated by the amount of AMP or β-Dfructose-2,6-bisphosphate

10. Pyruvate kinase is regulated by phosphorylation → inactivation.

• All three steps involve large ΔG°’ and are irreversile

- That is why we need regulation as above

- The availability of glucose also regulates glycolysis (no glucose = pathway off)

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1. Hexokinase (recognizes hexoses)

• Glucose is phosphorylated using ATP

• Adding phosphate to C6 from ATP

• Hydroxyl on C6 attacks y phosphate → transfer phosphate to C6

Hexokinase Binding

• Mg2+-ATP2- binds to large lobe away from glucose binding

• Substrates bind in the active site via charged and polar residues

- Negative ATP interacting with positive AAs

- Glucose with hydroxyls interact with polar AAs

• This results in a conformational change where the enzyme closes around the substrates – induced fit model of

binding (transfer of P to C6)

• C6 hdrol attaks the γ phosphate → G6P

Hexokinase Mechanism

• ATP (negative charges coordinated with Mg ion)

• 2 positively charged amino acids (Lys and Arg) coordinate

negatively charge ATP and hold in active site

• Glucose hydroxyl on C6 attacks y phosphate

• Glucose 6-phosphate + ADP

2. Phosphoglucose Isomerase

• The 6 member ring opens up to the linear form, an

isomerization reaction moves the C=O from C1 to C2

• Aldose sugar to ketose sugar

3. Phosphofructokinase (PFK-1)

• PFK-1 phosphorylates C1 hydroxyl using ATP

- 2nd ATP requiring step

- Phosphate from ATP transferred to C1 by

hydroxyl on fructose 6-phosphate attacking y

phosphate

• PFK-1 is inhibited allosterically by ATP and activated by Fructose 2,6 bisP and AMP (lower energy)

- F-2, 6-BP also activates (auxiliary enzyme)

◼ PFK-2 will transfer phosphate to C2 which can stimulate PFK-1 and

activate to speed things up

Allosteric Regulation of PFK-1

• PFK-2 (F-2,6-phosphate) and AMP allosterically activates PFK-1

• High concentration AMP, outcompete ATP binding to allosteric site

• ATP acting as allosteric regulator but also enzyme reaction using ATP

• Lots of AMP, binding allosteric site, inhibit enzyme

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BCH210H1 Full Course Notes

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Document Summary

Glut4 has 12 transmembrane helices and forms a binding site for glucose transport: glucose provides a substrate for the glycolysis that will lead to atp production in muscle (and other cells) Glycolysis: stage 1 first five steps (energy input phase/ stages that need energy to generate a lot more energy) At the end of stage 1, 2 gap (glyceraldehyde 3-phosphate: stage 2 last five steps (generate atp and nadh) Generates 4 atps (stage 2 runs twice) and nadhs. At the end of stage 2 is 2 pyruvate: all takes place in cytoplasm which will head to mitochondria if o2 is available. In mitochondria - further oxidation and production of waste products (co2) and. Atp through oxidative phosphorylation: under cellular conditions, concentration of substrates and products can change the free energy for reaction. Free energy of glycolysis: negative overall pathway favorable under standard conditions, negative overall pathway (greater change in free energy) for actual free energy.

Related Questions

1. Plants need which of the following to carry on photosynthesis?

a. H2O

b. CO2

c. O2

d. both O2 and CO2

e. both H2O and CO2

2. Organisms that derive their chemical energy either from the process of chemosynthesis or photosynthesis are classified as

a. autotrophs.

b. parasites.

c. heterotrophs.

d. saprophytes.

e. mutualists.

3. The carbon source for organisms that derive their energy from photosynthesis is

a. carbon monoxide.

b. carbon dioxide.

c. hydrocarbons.

d. methane.

e. glucose.

4. The oxygen released in photosynthesis comes from

a. carbon dioxide.

b. glucose.

c. ribulose bisphosphate.

d. water.

5. When chlorophyll a molecules absorb energy, the molecules

a. release electrons.

b. release X-rays.

c. release energy.

d. release electrons and X-rays.

e. release electrons and energy.

6. The flow of what particle across the thylakoid membrane powers the production of ATP?

a. electrons

b. hydrogen ions

c. oxygen

d. carbon dioxide

e. phosphate ions 2

7. The light-independent reactions were discovered by

a. M. D. Hatch.

b. Andrew Benson.

c. Melvin Calvin.

d. Robert Hill.

e. both Andrew Benson and Melvin Calvin.

8. For each six atoms of carbon dioxide fixed in the light-independent reactions, how many molecules of PGAL (phosphoglyceraldehyde) are produced?

a. 2

b. 3

c. 6

d. 12

e. 15

Chapter 7

9. The ultimate source of energy for living things is

a. the Krebs cycle.

b. fossil fuels.

c. the sun.

d. glycolysis.

e. aerobic respiration.

10. When molecules are broken apart in respiration

a. the heat produced is used to drive biological reactions.

b. the oxygen in the compounds that are broken apart is used as an energy source.

c. the energy released in respiration is channeled into molecules of ATP.

d. ATP is converted into ADP.

e. ADP is released as a waste product.

11. ATP

a. can be produced by photosynthesis.

b. is produced in the degradation of organic compounds such as glucose.

c. is generated in anaerobic respiration.

d. is released in aerobic respiration.

e. all of these

12. Which part of the energy-releasing pathway can convert all carbon that enters to carbon dioxide?

a. fermentation

b. glycolysis

c. Krebs cycle

d. electron transport

e. phosphorylation

13. Which liberates the most energy in the form of ATP?

a. aerobic respiration

b. anaerobic respiration

c. alcoholic fermentation

d. lactate fermentation

e. All liberate the same amount, but through different means.

14. Aerobes use ________ as the final electron acceptor in electron transport phosphorylation.

a. hydrogen

b. carbon

c. oxygen

d. H2O 3

15. Glycolysis depends on a continuous supply of

a. NADP.

b. pyruvate.

c. NAD+.

d. NADH.

e. H2O.

16. Glycolysis

a. occurs in the mitochondria.

b. results in the production of pyruvate.

c. occurs in the cytoplasm.

d. occurs in the mitochondria and results in the production of pyruvate.

e. results in the production of pyruvate and occurs in the cytoplasm.

17. The end product(s) of glycolysis is(are)

a. acetyl CoA.

b. carbon dioxide.

c. pyruvate.

d. glucose.

e. glucose and carbon dioxide.

18. Which is capable of being reduced during both glycolysis and the Krebs cycle?

a. NAD+

b. FAD+

c. ADP

d. NADH

e. NADP+

19. The Krebs cycle takes place in the

a. ribosomes.

b. cytoplasm.

c. nucleus.

d. mitochondria.

e. chloroplasts.

20. The breakdown of pyruvate in the Krebs cycle results in the release of

a. energy.

b. carbon dioxide.

c. oxygen.

d. energy and oxygen.

e. energy and carbon dioxide.

ochremole959

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.

1.When something appears blue, it is absorbing all colors except__________.

yellow

blue

red

green

orange

2.During heavy exercise, lactic acid can build up in ourmuscles. Why? How does this resemble the metabolism of bacteria andyeast?

lactic acid is results from insufficient oxygen during sugarmetabolism; it is fermentation

lactic acid accumulates when we are dehydrated; bacteria andyeast use the same pathway

lactic acid is built up from carbon dioxide; bacteria and yeaststore energy in this way

3.Why must a cell keep a similar concentration of dissolvedsubstances with the fluid surrounding them?

to avoid dilution of potential energy

to avoid osmotic imbalance and rapid gain or loss of water

to maintain the correct amount of dehydration and hydrolysis

4.What is entropy?

the amount of energy in a system

the amount of disorganization

the amount of organization

5.Burning a log is the reverse reaction found in photosynthesis.What products would be formed in burning a log?

carbon dioxide and water

glucose and oxygen

oxygen and carbon dioxide

oxygen and water

6.The main reason that cellular respiration needs to occur stepby step instead of a single, big reaction is

cells don't store enough oxygen

too much energy would be released for the cell to harness

cells don't have many mitochondria.

cells produce the enzymes needed for cellular respiration veryslowly

7.Enzymes are catalysts because they operate to:

raise activation energy

lower activation energy

supply activation energy

supply the reactants

8.When ATP powers a reaction it becomes ADP. The ADP

can reform ATP by an exergonic reaction

is a waste product for lysosomal breakdown

can reform ATP by an endergonic reaction

can reform ATP by an oxidation reaction

can reform ATP by an equilibrium reaction

9.The energy source that drives photosynthesis is

water

glucose

carbon dioxide

oxygen

sunlight

10. What is the process by which enzymes regulate their ownactivity?

osmosis

self-propulsion

feedback inhibition

11.Coupled reactions are reactions in which a

endergonic reaction drives a spontaneous reaction

exergonic reaction drives a spontaneous reaction

endergonic reaction drives an exergonic reaction

exergonic reaction drives an endergonic reaction

12.How is water used in photosynthesis?

as a substrate for ATP synthase

as an electron donor

to combine with ADP forming ATP

as an electron acceptor

13.Why are the âDark Reactionsâ of photosynthesis referred to asâDarkâ?

they do not require light

they can only occur at night

they generate excess sugar and the leaves turn brown

14.What is the difference between potential and kineticenergy?

potential is stored, kinetic is being used

potential is being used, kinetic is ready to be used

potential is negative, kinetic is positive

15.The products of cellular respiration are

carbon dioxide, water, and ATP

glucose, water, and ATP

glucose, carbon dioxide, and ATP

oxygen, ATP, and water

carbon dioxide, glucose, and water

16.All of the following are correct about energy except:

The biological world gets its energy from the sun.

Chemical bonds store potential energy.

A boulder perched on a hill has kinetic energy.

Energy is defined as the ability to do work.

All forms of energy can be converted to heat.

17.What is needed for the end product of glycolysis, pyruvate,to enter the citric acid cycle?

More glucose for energy

ATP

Oxygen

Carbon dioxide

18.The enzyme that forms a transmembrane channel in mitochondriaand phosphorylates ADP

a carrier protein

ATP synthase

acetyl CoA

19.Fermentation is most common in

plants

microorganisms

animals

20.During adsorption of sunlight by photosystems, H+ ions aregenerated. Where do they come from? What are they used for?

from the breakdown of sugar; they help form water

water; they help form sugar

from carbon dioxide; they help dissolve NaCl

21.Glycolysis

does not use oxygen

uses oxygen

uses carbon dioxide

22.Photosynthesis is

not dependent on chlorophyll

a process that produces glucose and oxygen

a process that produces water and carbon dioxide

23.Breakdown of glucose generates many ATP molecules, each ofwhich can be used independently. Why is ATP ideally suited to powerbiological reactions?

ATP has many hydrogen bonds

ATP has enough energy to power one biological reaction

ATP readily dissolves in water

24.Objects that are not actively moving but have the capacity todo so are said to possess:

kinetic energy

entropy

potential energy

living energy

25.The first stage of cellular respiration, called ___________,takes place in the cytoplasm of the cell and needs no oxygen.

photorespiration

citric acid cycle

glycolysis

oxidation

26.Diffusion

requires energy

utilizes proteins to move molecules across a membrane

moves molecules against a concentration gradient

does not require energy

cannot occur without a membrane present

27.What is the name of the molecule on which an enzymeworks?

substrate

monomer

polymer

28.ATP contains

phenylalanine

two phosphate groups

three nitrate groups

three phosphate groups

29.How does chlorophyll function in photosynthesis?

by absorbing carbon dioxide

by absorbing the sun's energy

by absorbing water

30.Objects that are moving are said to possess:

living energy

potential energy

entropy

kinetic energy

31.The respiration pathway that evolved first is probably

glycolysis

aerobic respiration

citric acid cycle

32.The energy source for the process of photosynthesis is

oxygen

sunlight

carbon dioxide

chlorophyll

glucose

33.Burning wood generates heat and light. What type of reactionis this?

exergonic

kinetic energy

endergonic

potential energy

equilibrium

34.What is meant by a âcoupled reactionâ in terms of energy?

many poymers are built simultaneously

energy released by one reactions powers another reaction

some reactions occur in the same organelle

35.The First Law of Thermodynamics states:

energy is constantly being created by entropy events

energy can be changed from one form to another, but cannot becreated or destroyed

energy can be used and then destroyed because of entropy'sactions on it

energy can be destroyed while it is producing entropy

36.How do we dispose of the carbon derived from the glucose thatis metabolized during respiration?

by breathing out

via our urine

it is broken down in lysosomes

37.Both plant and animal cells have mitochondria because theyboth

carry on respiration

carry on photosynthesis.

require water

38.What is Activation Energy?

the energy needed to initiate a reaction

the energy that transports water into cells

potential energy

39.If you put a plant in a chamber and shine a light on it

oxygen will decrease and carbon dioxide will increase

oxygen will increase and carbon dioxide will decrease

oxygen and carbon dioxide will increase

oxygen and carbon dioxide will decrease

40.What are the inputs and the output molecules for the overallphotosynthetic process?

input sugar and oxygen; output carbon dioxide and water

input oxygen and water; output sugar and carbon dioxide

input carbon dioxide and water;output sugar and oxygen

41.What kind of reaction is photosynthesis?

endergonic

kinetic energy

exergonic

potential energy

equilibrium

42.In the process of glycolysis, glucose is cleaved into a pairof three-carbon molecules called

lactate

pyruvate

acetyl CoA

ATP

alcohol

43.Entropy is

order

disorder

complexity

Both order and disorder are correct

Both complexity and disorder are correct

44.Glycolysis takes place in the _____________ and the citricacid cycle and electron transport chain take place in the___________.

cytoplasm; endoplasmic reticulum

mitochondria, chloroplast

mitochondria; cytoplasm

cytoplasm; mitochondria

45.The organelle that carries out photosynthesis in plants isthe

mitochondria

chloroplast

ribosome

chlorophylllysosome

46.The energy to power the Calvin cycle comes from

cellular respiration

oxygen

the light reactions of photosynthesis

47.Which of the following can be broken down into intermediateproducts that enter cellular respiration?

Proteins

Lipids

Carbohydrates

All of these.

48.When cellular product levels get too high, the responsibleenzyme is inhibited. This is an example of

promotion

denaturation

equilibrium

a coenzyme

feedback inhibition

49.How is respiration the opposite of photosynthesis?

respiration breaks sugar down to carbon dioxide; photosynthesisbuilds sugar from carbon dioxide

respiration builds sugar from carbon dioxide; photosynthesisbreaks sugar down to carbon dioxide

respiration requires energy input; photosynthesis gives offexcess energy

50.The molecule that absorbs sunlight for photosynthesis is

oxygen

carbon dioxide

chlorophyll

glucose

sunlight

amaranthbear841

BCH210H1 Lecture 27: Lecture 27

BCH210H1 Full Course Notes

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