Chapter 5 - Energy Crisis Solved by Glycolysis

Chapter 5 - Energy Crisis Solved by Glycolysis

Remember the solution to the osmosis crisis. What new crisis does this create? Why?

• proton pump (of hydrogen ions)

• creates an energy crisis because the cells are now depleting the environment of ATP when using it to pump protons out of the cell

What did the calcium pump do?

• pumped out divalent cation Ca⁺⁺

• used 1 ATP and converted it to ADP

• worked for the same purpose as the proton pump

How does the sodium potassium pump work? What is the net movement of ions it creates?

• takes in 3 Na⁺ and 2 K⁺

• net flow of 1 Na⁺ out of the cell

• used 1 ATP and converted it to ADP

What are the 3 phase of glycolysis?

1. Investment

2. Crux Reaction

3. Harvesting

What happens during the Investment phase of glycolysis? What is the resulting molecule?

• glucose is split into two 3-carbon molecules

• ATP invests into glucose by giving it two phosphates (1 from each ATP)

• the resulting molecules are G3P an another molecule that rearranges to become G3P

  • Glucose’s 3-carbon molecule with a Phosphate attached

What is it called when a phosphate group is added?

phosphorylated

What is the important result of phosphorylating a glucose molecule twice during glycolysis?

it creates a reducing power

What kind of atoms get reduced and what kind of atoms do the reducing?

• get reduced: high electronegativity (their charge is REDUCED from neutral to negative when they accept electrons from the other atom)

• doing the reducing: the electron that wants to give up their electrons (gives the electron to the more electronegative atom, and reducing it)

What does it mean to be oxidized? What types of atoms get oxidized?

• an atom that gives away an electron is oxidized

• less electronegative atoms

In NaCl, which atom is reduced and which is oxidized?

• Na⁺

• Cl^-

• Na is oxidized, Cl is reduced

What is reducing power? What level of chemical organization does this refer to?

• a molecule’s ability to donate elections

What are the three ways you can tell that a molecule was reduced? Oxidized?

Reduced

• gains a hydrogen

• loses an oxygen

• charge is reduced to a negative charge

• gains electron

Oxidized

• gains an oxygen

• loses a hydrogen

• charge becomes positive/more positive

• loses electrons

How do free protons and electrons play a role in oxidation-reduction reactions?

they don’t! these only happen between molecules

Explain the reducing power of these 1-carbon molecules.

CH₄

CH₂O

CO₂

CH₄ - maximally reduced (cannot gain any more H’s, and does not have any O to lose)

CH₂O - in the middle (could lose an O, doesn’t have 4 H’s bonded to carbon, so could gain)

CO₂ - maximally oxidized (cannot lose any H, cannot gain any more O)

Out of the following molecules, which has the greatest reducing power, and which has the least?

CH₄

CH₂O

CO₂

Greatest - CH₄

Least - CO₂

What is a redox reaction?

oxidation-reduction reaction ( the gain and loss of electrons powered by the difference in reducing power of molecules)

What is the reducing power of G3P?

• very high, really wants to give up an electron

What happens in the Crux reaction of glycolysis? What does this reaction NOT require and why?

• G3P (which really wants to give up an electron) reacts with NAD⁺ (which really wants electrons)

• the difference in reducing power is so great that G3P can gain an additional phosphate without the use of ATP

• NAD⁺ is reduced to NADH (reduced by G3P)

• G3P is oxidized to 1, 3 Biphosphoglycerate

What is a cofactor? What is the cofactor in the Crux reaction?

• a molecule that is required for the function of an enzyme

  • usually really good at transferring electrons

• NAD⁺ is the cofactor for Crux

What happens in the harvesting phase of glycolysis?

• the 4 phosphates from the 2 1,3 biphosphoglycerates are harvested to add on to 4 ADPs

• the products are 4 ATPs and 2 pyruvate

Draw out the steps of glycolysis.

What is the GROSS output of ATP in glycolysis? What is the NET output?

• gross: 4 ATPs

• net: 2 ATPs (because 2 ATPs are invested

What does the structure of NAD look like? What does this tell you about where the two other phosphates used to phosphorylate the 4 ATPs at the end of glycolysis come from?

• looks like two RNA molecules

• there are two phosphates that come from here

What is the most common way that cells gain NAD⁺ for more glycolysis reactions?

fermentation

Explain the two types of fermentation with their reactants and products. Include the redox process that produces NAD⁺.

1. Two-step process converting pyruvate into ethanol

2. Pyruvate is converted directly to lactate

*NADH is re-oxidized into NAD⁺, losing its reducing power (losing its hydrogen)

*note that pyruvate is a product of glycolysis and is used in fermentatin (which creates one of the reactants for glycolysis

What new crisis does glycolysis create? Draw a simple work map of all of the previous crises, how they were solved, and what new crisis it created.

What are cations?

positively charged ions

What is the additional benefit of pumping cations out of the cell (other than prevent the osmosis crisis)?

it can create a very strong concentration gradient (with a much higher concentration existing outside of the cell)

Explain the co-transport system used to actively transport a glucose molecule even where there isn’t a high concentration of glucose outside of the cell.

• The sodium potassium pump pumps sodium ions (Na⁺) out of the cell

• One sodium ion binds to the glucose co-transporter (on the outside of the cell)

• The co-transport protein snatches a glucose molecule from the outside and bring it (along with the sodium ion) into the cell

How does the work done by the sodium potassium pump benefit the glucose co-transport protein?

• the sodium potassium pump pumps a lot of sodium ions outside of the cell

• when there are a lot more sodium ions outside of the cell than inside, the glucose co-transport protein works a lot faster

  • the concentration gradient is stronger, making sodium ions move faster and down the gradient into the cell

  • there are more sodium ions to attach to the co-transport protein

How does a coupled transport protein work? Use the example of the glucose co-transport protein.

• It uses the movement of one molecule (the Na⁺ ion) down its concentration gradient to bring in another molecule against its concentration gradient (the glucose molecule)

How much ATP is used to transport glucose into the cell? Which system(s) use this ATP?

• 1 ATP molecule

• the sodium potassium pump requires one ATP

After glycolysis, fermentation, the pumping of sodium ions outside of the cell, and the pumping of glucose molecules into the cell, what is the net gain of ATP? What does this mean for the efficiency of this system.

• Glycolysis produces 2 net ATP

• Sodium/Potassium pump uses 1 of those ATP to pump sodium ions out so that glucose can enter

• there is only 1 net ATP gained, making this system extremely inefficient

What is the only locomotion that does not require ATP? How is it powered?

• the flagella of bacteria

• powered by a strong concentration gradient (specifically the high concentration of protons on the outside of the cell)

What is ATP used for in RNA?

it is the a nucleotide

Draw out the hydrolysis of ATP.

What is the main point of glycolysis?

• harvest energy from glucose to create ATP

  • powering the proton pumps

With NAD+ and NADH, which donate electrons and which receives electrons? Describe what this means for redox reactions.

NAD+

• receives electrons

• gets reduced during glycolysis

NADH

• donates electrons

• gets oxidized during fermentation

Draw out the flow of energy and main products in a cell. Include glycolysis, fermentation, and proton pumps/co-transport proteins.

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Is this depolymerization or polymerization? How do you know? Explain how ATP is either used or produced.

• polymerization

• we have many (6) smaller carbon molecules (CO₂) on the reactant side

• there is one larger carbon molecule on the end that was polymerized from the smaller molecules

• ATP is on the reactants side, leaving ADP + an inorganic phosphate on the right

*note that water being a reactant does not indicate depolymerization

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

In this reaction, what is being reduced and what is being oxidized? How do you know?

• the CO₂ molecules are being reduced because they gained hydrogens

• the H₂O molecules are oxidized

  • it has to be the opposite of the other molecule

  • we also know because it lost a hydrogen

When a molecule is reduced, does energy increase or decrease? What about for a molecule that is oxidized?

• reduced = gains electrons, therefore gains energy/”reducing power”

• oxidized = loses electrons, therefore loses energy

What is the carbon molecule input of glycolysis? What is the carbon molecule output? What is the cofactor and what happens to it during the process?

• glucose is input

• pyruvate is the output

• NAD+ is reduced to NADH

What is the carbon molecule input of fermentation? What is the carbon molecule output? What is the cofactor and what happens to it during the process?

• pyruvate is input

• ethanol or lactic acid is output

• NADH gets oxidized to NAD+ to be used in glycolysis

Draw and map out the functions of a proto-cell that performs glycolysis, fermentation, and has a proton pump.