Life at the Cellular Level 3

Question 1

What is the basic rule of energy?

Answer 1

Energy cannot be created or destroyed, it merely changes its form

Question 2

What are the two laws of thermodynamics?

Answer 2

1. Energy can be converted from one form to another but the total energy of the universe remains constant
2. All energy transformations ultimatelty lead to more disorder in the universe, ie, increase in entropy

Question 3

What is entropy?

Answer 3

Degree of disorder in a system, quanitity representing the unavailability of a systems therman energy for conversion into work (measures in J/K)

Question 4

What happens as usable energy decreases and unusable energy decreases?

Answer 4

Entropy increases

Question 5

How do cells create and maintian order?

Answer 5

By performing lots of chemical reactions which require energy

Question 6

How do the reactions within cells obey the second law of thermodynamics (leads to an increase in disorder/entropy)?

Answer 6

Chemical reactions used to create order generate heat which is discharged into the surrounding environment and disorders it, leading to an increase in total entropy

Question 7

What is Gibb’s free energy?

Answer 7

Amount of useful, free energy in a system that can be used for work (measured in kJ/mol)

Question 8

What are the 3 quantities that can define free energy?

Answer 8

Enthalpy (H)

Entropy (S)

Absolute temperature (T)

Question 9

What formula expresses free energy?

Answer 9

G = H - TS

Question 10

What is enthalpy?

Answer 10

Total heat content of a system

Question 11

What is absolute temperature?

Answer 11

Temperature measured from absolute zero in kelvin

Question 12

What does enthalpy reflect?

Answer 12

The number/kinds of bonds being broken or formed

Question 13

When can spontaneous reactions occur?

Answer 13

If a system gives up energy

Becomes more random and increases in entropy

Question 14

Why must spontaneous reactions have a negative value for delta G (change in G)?

Answer 14

Because they must decrease enthalpy and/or increase entropy

Question 15

What does a positive and negative delta G mean?

Answer 15

Delta G positive means the reaction requires energy

Delta G negative means the reaction releases energy

Question 16

Why do most biological reactions require a positive delta G?

Answer 16

Because they require order

Question 17

What is energy coupling?

Answer 17

Transfer of energy from catabolism to anabolism

Question 18

How do cells carry out energetically unfavourable reactions?

Answer 18

By using energy coupling

Question 19

How does energy coupling allow energetically unfavourable reactions to happen?

Answer 19

The unfavourable reaction with a positive delta G is driven by the favourable reaction with a negative delta G as the net free energy change is less than 0

Question 20

What is catabolism?

Answer 20

Metabolic pathways that break down moelcules into smaller units releasing energy (negative delta G)

Question 21

What is anabolism?

Answer 21

Synthesis of complex molecules from simper ones using energy (positive delta G)

Question 22

Why do reactions never reach the equilbrium?

Answer 22

Because delta G = 0 is incompatible with life, this doesn’t happen because energy is passed from the envionment to the organism and vice versa

Question 23

What is the dyamic steady state?

Answer 23

Flow of energy between molcules, a continuous series of reactions

Question 24

Why do the concentrations of intermediate molecules in a dynamic steady state remain constant?

Answer 24

Because as soon as they are made they are used

Question 25

What does a simple dynamic steady state system look like?

Answer 25

When a=b the system is in a dynamic steady state due to maintaning the concentration of intermediate molecules

Question 26

What is metabolism?

Answer 26

Chemical processes in a living organism where food is broken down and used for energy production

Question 27

What happens during metabolism in terms of free energy?

Answer 27

Flows between catabolic and anabolic processes, with energy being lost as heat

Question 28

Each step of a metabolic pathway is catalysed by an enzyme, what are some of their properties?

Answer 28

They are selective

They can be regulated

Question 29

Why is glucose often used as a food molecule

Answer 29

It has a high potential energy

Question 30

Why does the breakdown of glucose occur in a series of small reactions?

Answer 30

To allow the energy to be extracted in stages, as if it was broken down in one step to much energy would be produced and most of it would be lost to heat

Question 31

How does glucose metabolism begin?

Answer 31

A small amount of energy must be inputed, activated carrier molecules store released energy

Question 32

What does endergonic mean?

Answer 32

Anabolic pathway is supplied with free energy

Question 33

What does exogonic mean?

Answer 33

Catabolic pathway releases free energy

Question 34

How is free energy supplied and stored?

Answer 34

Using the interconversion of ATP and ADP

ATP + H₂O ⇔ADP + P_i

Question 35

Is ATP to ADP + P_i exogonic or endogonic?

Answer 35

Exogonic

Decrease in free energy

Delta G is negative

Question 36

Is ADP + P_i to ATP exogonic or endergonic?

Answer 36

Endergernic

Requires free energy input

Delta G is positive

Question 37

How to enzymes allow us to do reactions that would otherwise be impossible?

Answer 37

By lowing the activation energy

Question 38

Why does potential energy in food molecules arise?

Answer 38

Because they contain large amounds of H atoms

Question 39

What steps following the oxidaiton (breakdown) of glucose?

Answer 39

Releases electrons that flow through a series of intermediate steps to another spiecies, such as O₂

Can be described as an electromotive force (EMF)

Question 40

What carrier molecules do cellular redox reactions use?

Answer 40

NAD⁺

FAD⁺

NADP⁺

Question 41

What do activated carriers acts as in biochemical pathways to fuel oxidation and biosynthesis?

Answer 41

Coenzymes