An Introduction to Metabolism

Question 1

What is the purpose of catabolic pathways?

Answer 1

The releasing of energy by breaking down complex molecules into simpler compounds

Question 2

What is cellular respiration?

Answer 2

The breakdown of glucose in the presence of O2

Question 3

What is an example of a pathway of catabolism?

Answer 3

Cellular respiration

Question 4

What is the purpose of anabolic pathways?

Answer 4

To consume energy to build complex molecules from simpler ones

Question 5

What is an example of an anabolic pathway?

Answer 5

The synthesis of protein from amino acids

Question 6

What is potential energy?

Answer 6

Energy that matter possesses because of its location or structure

Question 7

How do molecules possess energy?

Answer 7

Due to the arrangement of electrons in bonds between their atoms

Question 8

What is chemical energy?

Answer 8

Potential energy available for release in a chemical reaction

Question 9

Why are complex molecules, such as glucose, high in chemical energy?

Answer 9

Because energy is released as they are broken down to simpler products

Question 10

Why are organisms open systems?

Answer 10

They absorb energy from light or food and release heat and metabolic wastes, such as CO2, to the surroundings

Question 11

What is the first law of thermodynamics, aka the principle of conservation of energy?

Answer 11

Energy can be transferred and transformed, but it cannot be created or destroyed

Question 12

What is the second law of thermodynamics?

Answer 12

Every energy transfer or transformation increases the entropy (S) of the universe

Question 13

What is entropy?

Answer 13

A measure of molecular disorder, or randomness

Question 14

How do living organisms increase the disorder of their surroundings?

Answer 14

Through their metabolism

Question 15

How do processes that increase the entropy of the universe occur?

Answer 15

Spontaneously

Question 16

Processes that decrease entropy are what?

Answer 16

Non-spontaneous; they require an input of energy

Question 17

What does the free-energy change of a reaction tell us?

Answer 17

Whether or not the reaction occurs spontaneously

Question 18

What is free energy?

Answer 18

The portion of a systems energy that can do work when temperature and pressure are uniform throughout the system

Question 19

What is Gibbs Free Energy equation?

Answer 19

ΔG = ΔH - TΔS

Question 20

What does the Gibbs Free Energy equation mean?

Answer 20

• ΔG = change in free energy
• ΔH = change in enthalpy (total energy)
• ΔS = change in entropy
• T = temperature in Kelvin (K)

Question 21

What does the ΔG for a process determine?

Answer 21

• Whether it is spontaneous or not; spontaneous when negative, non-spontaneous when zero or positive
• The maximum amount of work an exergonic reaction can perform

Question 22

When ΔG reaction occurs spontaneously, it is a..

Answer 22

Negative exergonic

Question 23

The chemical products of respiration store _____ less free energy per mole than the reactants

Answer 23

686 kcal

Question 24

A cell does three main kinds of work:

Answer 24

• Chemical work: pushing endergonic reactions
• Transport work: pumping substances across membranes against the direction of spontaneous movement
  -Mechanical work: such as beating cilia or contracting muscle cells

Question 25

What is energy coupling?

Answer 25

The use of an exergonic process to drive an endergonic one

Question 26

Most energy coupling in cells is mediated by ___

Answer 26

ATP

Question 27

What is ATP (adenosine triphosphate) composed of?

Answer 27

Ribose, adenine, and three phosphate groups

Question 28

How is ATP regenerated?

Answer 28

By the addition of a phosphate group to ADP

Question 29

What is a catalyst?

Answer 29

A chemical agent that speeds up a reaction without being consumed by the reaction

Question 30

What is an enzyme?

Answer 30

A macromolecule that acts as a catalyst to speed up a specific reactions

Question 31

How do enzymes lower EA?

Answer 31

• Substrates oriented to facilitate the reaction
• Substrates may be stretched to make the bonds easier to break
• The active site may provide a microenvironment that favors the reactions
• Amino acids in the active site may participate in the reaction

Question 32

How can an enzyme-catalyzed reaction be sped up?

Answer 32

By increasing substrate concentration

Question 33

When is the enzyme saturated?

Answer 33

When all enzyme molecules have their active sites engaged

Question 34

How can the reaction rate be sped up if the enzyme is saturated?

Answer 34

Only by adding more enzyme

Question 35

When inhibitors bind to the enzyme by weak interactions, what does it reverse in?

Answer 35

Reversible inhibition

Question 36

What are competitive inhibitors?

Answer 36

Inhibitors that closely resemble the substrate and can bind to the enzyme’s active site

Question 37

What are noncompetitive inhibitors?

Answer 37

Inhibitors that bind to another part of the enzyme, away from the active site

Question 38

What occurs with noncompetitive inhibitors?

Answer 38

Binding of the inhibitor causes the enzyme to change shape, making the active site less effective at catalyzing the reaction

Question 39

What occurs with competitive inhibitors?

Answer 39

Enzyme productivity is reduced because the inhibitor blocks the substrate from entering the active site

Question 40

What is feedback inhibition?

Answer 40

When the end product of a metabolic pathway shuts down the pathway