Midterm 1: Lec 5 Energy Slides

Question 1

What’s the difference between kinetic and potential energy?

Answer 1

Kinetic energy is work-associated; potential energy is stored energy

Question 2

Where is energy from the sun stored?

Answer 2

Stored as potential energy in chemical bonds of sugar molecules formed by photosynthesis

Question 3

First law of thermodynamics

Answer 3

Energy cannot be created or destroyed; it can only be converted from one form to another

Question 4

Second law of thermodynamics

Answer 4

In any energy interconversion, some energy is released as heat, which adds to the entropy of the system

Question 5

What happens as energy is utilized?

Answer 5

More and more of it is converted to heat

Question 6

Metabolism

Answer 6

Sum of all chemical processes occurring within a cell or organism

Question 7

Metabolic pathway

Answer 7

Product of one reaction becomes reactant in the next (series of reactions)

Question 8

Equilibrium constant (Keq)

Answer 8

Ratio of the concentration of products and reactants at equilibrium (high Keq means reaction goes far towards the right, or completion)

Question 9

What changes Gibbs free energy?

Answer 9

Breaking of chemical bonds in the course of chemical reactions

Question 10

What is the equation for ∆G?

Answer 10

∆G = ∆H - T∆S

-remember that ∆G indicates nothing about rxn rate

Question 11

Exergonic reaction

Answer 11

Products contain less free energy than reactants (negative ∆G) - occur spontaneously and release heat

Question 12

Endergonic reaction

Answer 12

Products contain more energy than reactants; need energy for reaction to happen

Question 13

What does a ∆G value near zero mean?

Answer 13

Reaction is readily reversible

Question 14

What does a large negative ∆G mean?

Answer 14

Reaction that goes almost to completion

Question 15

What does ATP hydrolysis release? What’s the equation?

Answer 15

Releases large amounts of energy

Equation is: ATP + H2O = ADP + Pi + energy

Question 16

What does the synthesis of ATP from ADP and Pi require?

Answer 16

Energy

Question 17

Where does the body store carbohydrates and lipids?

Answer 17

Carbs in glycogen; lipids in triglycerides

Question 18

∆G for ATP hydrolysis in standard vs. cell conditions

Answer 18

Standard: -7 kcal/mol
Cell: -12 kcal/mol (textbook says -14)

Question 19

What are the exergonic reactions in the energy-coupling ATP cycle?

Answer 19

Cell respiration and catabolism

Question 20

What are the endergonic reactions in the energy-coupling ATP cycle?

Answer 20

Active transport, cell movements, anabolism

Question 21

Equation for firefly bioluminescence

Answer 21

Luciferin + O2 = ATP; releases light

Question 22

What are the two ways that cells make ATP?

Answer 22

Substrate-level phophorylation and chemiosmosis (majority made this way)

Question 23

Where does chemiosmosis occur and what does it need?

Answer 23

Occurs in inner mitochondrial membrane, requires O2

Question 24

What happens in substrate-level phosphorylation?

Answer 24

Direct transfer of phosphate group to ADP from another molecule (like phosphoenolpyruvate, or PEP)

Question 25

Activation energy

Answer 25

Energy required to destabilize existing chemical bonds and start a chemical reaction

Question 26

What do catalysts do?

Answer 26

Reduce activation energy and increase reaction rate (but not affect final equilibrium)

Question 27

What do enzymes do?

Answer 27

Proteins that carry out most catalysis in cells (some done by ribozymes in RNA)

Question 28

What is the reactant molecule of an enzyme?

Answer 28

Substrate - enzymes usually relatively specific in choice of reactant molecule

Question 29

Where does substrate bind?

Answer 29

Active site

Question 30

What conditions do enzymes need/prefer?

Answer 30

Optimum pH and temperature (where they function best); sometimes they need a coenzyme

Question 31

When does an enzyme catalyzed reaction reach maximum rate?

Answer 31

When substrate concentration is high and all enzyme molecules are occupied with substrate molecules

Question 32

Competitive inhibition

Answer 32

Competitive inhibitor binds to active site, preventing substrate from binding (reversible)

Question 33

Uncompetitive inhibition

Answer 33

Uncompetitive inhibitor binds to enzyme-substrate complex, preventing release of products

Question 34

Noncompetitive inhibition

Answer 34

Noncompetitive inhibitor binds at site other than active site, changing enzyme structure so that normal substrate binding is blocked

Question 35

Allosteric regulation

Answer 35

Effector molecule binds to site other than active site of enzyme, inducing enzyme to change its shape

Question 36

For multi-subunit allosteric enzymes, what does the reaction rate vs. substrate concentration graph look like?

Answer 36

Has sigmoidal kinetics (and are important sites of metabolic control): once substrate binds first active site, quaternary structure changes and other sites are more likely to bind substrate - rapid rxn rate increase

Question 37

What is an example of an allosteric protein?

Answer 37

Hemoglobin (in the way it binds oxygen)

Question 38

Irreversible inhibition

Answer 38

Inhibitor binds to certain side chains at active site of enzyme and permanently deactivates the enzyme

Question 39

Allosteric regulation: what’s the difference between active and inactive form of enzyme?

Answer 39

Active form has proper shape for substrate binding; inactive form has shape that cannot bind substrate