Lecture 9: Energy and Enzymes (start of final exam material)

Question 1

What are the 5 important functions energy is used for?

Answer 1

• movement
• chemical reactions
• temperature control
• nerve signals
• cell division/ reproduction

Question 2

What is the difference between kinetic energy and potential energy

Answer 2

• kinetic: active motion energy

- potential: stored energy

Question 3

Explain the potential energy in bonds:

• which bonds have the highest PE and the lowest; why?
• what happens to the PE of the products if a chemical reaction creates more polar bonds?

Answer 3

• highest PE: non polar bonds (equal sharing of electrons and long weak bonds) vs lowest PE: polar bonds
• the products have a lower PE

Question 4

Explain the first law in thermodynamics

Answer 4

• energy in = energy out

Question 5

Write out the chemical breakdown of glucose

Answer 5

• C6H12O6 + 6O2 6CO2 + 6H2O + 2800kJ

Question 6

What is enthalpy (H)?

Answer 6

• the total energy in a molecule; most of it is stored potential energy

Question 7

Explain the change in enthalpy in an:

• exothermic reaction
• endothermic reaction

Answer 7

• exothermic: change in enthalpy is NEGATIVE

- endothermic: change in enthalpy is POSITIVE

Question 8

Define: entropy (s)

Answer 8

• amount of disorder

Question 9

What is the Gibbs free energy equation? State the whole equation.

Answer 9

Calculates the energy associated with a chemical reaction that can be used to do work.
delta G = delta H + T(deltaS)
- H is enthalphy, T is temp, S is entropy

Question 10

Explain the change in entropy in the chemical breakdown of glucose

Answer 10

• entropy increases because more disorder occurs

Question 11

Explain delta G/ the change in free energy if:

• the products have less free energy than the reactants
• the products have more free energy than the reactants
• what does this mean about the reactions?

Answer 11

• delta G is negative and the reaction is exergonic and spontaneous
• delta G is positive and the reaction is endergonic and non spontaneous

Question 12

define: exergonic and endergonic reactions;

- what drives endergonic reactions?

Answer 12

exergonic: reaction that releases energy
endergonic: reaction that absorbs energy; driven by ATP

Question 13

Draw a diagram of the free energy overtime of a spontaneous reaction. Also:

• explain and label delta G, Ea, transition state.
• explain the speed of the reaction and what it is dependent on.
• how can you accelerate the reaction?
• what stabilises the transition state

Answer 13

• see google doc
• speed of reaction may be fast or slow depending on activation energy required
• to accelerate the reaction you must lower the activation energy (with a catalyst)
• enzymes stabilize the transition state

Question 14

Draw the hydrolysis reaction of ATP and the coupled reaction diagram

Answer 14

• see google doc

Question 15

explain the metabolic pathway

Answer 15

• reactions are sequential (A–>B–>C–>D)

Question 16

define: oxidation and reduction

Answer 16

• oxidation: loss of electrons

- reduction: gain of electrons

Question 17

write out the oxidation of glucose reaction

Answer 17

• see google doc

Question 18

Fill in the blank: redox reactions often involve electron _____ such as _____ and ______. Both of these transfer __ electrons

Answer 18

• carriers
• F. A. D.
• NAD+
• 2

Question 19

Glucose

• stored as? (3)
• function
• what is glycolysis?

Answer 19

• glycogen, fats, and starch
• function: energy
• glycolysis: cellular respiration (set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into (ATP))

Question 20

define: catabolism and anabolism

Answer 20

catabolism: breakdown of complex molecules
anabolism: creation of complex molecules (ex: making glucose)

Question 21

Give the photosynthesis equation

Answer 21

• see google doc

Question 22

Write out the metabolic pathway

Answer 22

• see google doc

Question 23

what process produces ATP? How is this accomplished?

Answer 23

• cellular respiration; transfer of electrons

Question 24

What are the 4 steps/stages of cellular respiration?

Answer 24

• glycolysis
• pyruvate processing
• citric acid cycle
• electron transport and oxidative phosphorylation

Question 25

Explain step 1 of cellular respiration: glycolysis - location - what is oxidized and reduced - what goes in - what comes out - equation - anaerobic or aerobic?

Answer 25

- cytosol - oxidized: carbon; reduced: oxygen - what goes in: 2 ADP, 2 NAD+ - what comes out: 2 new ATP (4 total) , 2 NADH - glucose + 2NAD+ + 2ATP --> 2 pyruvate + 2NADH + 4 ATP - anaerobic

Question 26

Explain step 2 of cellular respiration: pyruvate processing - location - what goes in - what comes out - equation

Answer 26

- matrix - oxidized: carbon and pyruvate; reduced: oxygen - what goes in: 2NAD+ - what comes out: 2NADH - 2 pyruvate + 2 NAD+ + 2 CoA -> 2 acetyl-CoA + 2 NADH + 2 H+ +2CO2

Question 27

Explain step 3 of cellular respiration: citric acid cycle - location - for every glucose molecule, how many times does the cycle run? - equation

Answer 27

- matrix - twice 2 acetyl-CoA + 6NAD+ + 2FAD + 2ADP --> 4CO2 + 6NADH + 2FADH2 + 2ATP + 2CoA

Question 28

Explain step 4 part 1 of cellular respiration: electron transport - location - how does it occur? - what is the role of ubiquinone and cytochrome c? - how much ATP is created?

Answer 28

- cristae (inner membrane of mitochondria) or prokaryote plasma membrane - transfer of electrons from soluble redox coenzymes (NADH or FADH2) onto membrane-bound electron acceptors; electrons move down "chain" until it reaches the final acceptor: O2; creates a proton gradient (PE) - ubiquinone and cytochrome c: shuffle electrons between molecular complexes - 25

Question 29

Explain step 4 part 2 of cellular respiration: oxidative phosphorlyation - define: chemiosmosis

Answer 29

- proton gradient drives the synthesis of ATP - see google doc - chemiosmosis: movement of ions across a semipermeable membrane according to electrochemical gradient

Question 30

Why is oxygen the final electron acceptor? What happens in cellular respiration if no oxygen is available?

Answer 30

- larger change in PE than other substrates | - only substrate level phosphorylation occurs and we need to regenerate NAD+

Question 31

Explain fermentation and how it occurs in humans and yeast

Answer 31

- extraction of energy from carbs in the absence of respiration (anaerobic) - humans: glycolysis ends at pyruvate and is reduced to lactate to regenerate NAD+ - yeast: glycolysis ends at pyruvate which is decarboxylated and reduced to alcohol