lecture 2: energy

Question 1

Forms of energy in life? (5)

Answer 1

1. Radiant energy (photosynthesis)
2. Chemical energy
3. Thermal energy (Heat)
4. Mechanical energy (movement)
5. Electrical energy

Question 2

What happens to energy in the ecosystem? (3)

Answer 2

• Energy = transformed as it flows through ecosystems
• Enters as radiant (sun) energy and exists as thermal energy
• Subjected to laws of thermodynamics in the organisms

Question 3

First law of thermodynamics?

Answer 3

Energy can be transformed or transferred but can not be destroyed or created

Question 4

Second law of thermodynamics?

Answer 4

As energy is transformed —> some converted to unusable energy (heat) —> as entropy of the system increase
- Entropy of the universe is always increasing

Question 5

Why do organisms require energy?

Answer 5

Use energy to power biological work

Question 6

3 kinds of biological work that organisms carry out

Answer 6

1. Synthesizing molecules to build complex structures and to reproduce
2. Movement of body, cells and substances within cells
3. Transport of chemicals across the cell membrane

Question 7

What is energy coupling?

Answer 7

• Biological work is accomplished by coupling a SPONTANEOUS process to a NON SPONTANEOUS process = OVERALL SPONTANEOUS process
• Most energy coupling relies on ATP hydrolysis

Question 8

What is a spontenous process? Examples?

Answer 8

• Downhill reaction
• Happens without added energy
• Gravity, diffusion, chemical reactions

Question 9

What makes a process spontaneous (2 factors)?

Answer 9

1. Change in POTENTIAL ENERGY
   - Spontaneous if goes from high potential energy to LOW potential energy
2. Change in the degree of order (ENTROPY)
   - Spontaneous if goes from high order (low entropy) to low order (more entropy)

Spontaneous reactions want to increase the entropy of the universe

Question 10

Gibbs Free-Energy Change (∆G) takes into account both…

Answer 10

the changes of potential energy and the changes in disorder

Question 11

How do you interpret ∆G?

Answer 11

• ∆G = spontaneous/exergonic process
  + ∆G = non spontaneous/endergonic process
  ∆G = 0: process is at EQ

Question 12

What does ∆G represent in a spontaneous/exergonic process?

Answer 12

Energy available to carry out work when a process occurs (goes from high G to low G in a graph)

Question 13

What does ∆G represent in a non spontaneous/endergonic process?

Answer 13

Energy required to carry out a process (goes from low G to high G)

Question 14

2 Characteristics of spontaneous processes

Answer 14

1. Can be used to carry out work
2. Proceed towards equilibrium (∆G = 0)

Question 15

What happens at the end if a spontaneous system is carried out in a CLOSED system?

Answer 15

Work will eventually stop when the process reaches equilibrium

Question 16

What is dynamic equilibrium?

Answer 16

Forward process occurs at the same rate as the reverse process

Question 17

Organisms are open or closed systems?

Answer 17

Open

Question 18

What happens if a spontaneous process is carried out in an open system?

Answer 18

• Process does not reach equilibrium and work always continues
• Reactants are products are maintained at a STEADY-STATE (stable) concentrations and NOT at EQ concentrations
• Process remains sponteneous

Question 19

What is ATP + use + characteristics?

Answer 19

• Adenosine triphosphate: energy currency
• Used for most work in the cell vis energy coupling
• ATP has high chemical energy —> so ATP hydrolysis is highly spontaneous

Question 20

ATP Structure (3)

Answer 20

(RNA nucleotide, building blocks for RNA)
1. Nitrogenous base
2. Ribose sugar
3. Three phosphates

Question 21

What is the hydrolysis of ATP?

Answer 21

ATP —> ADP + P
- Hydrolysis (break) of bond between the 2 outermost phosphate groups —> form ADP (with 2 phosphates) + P (1 inorganic phosphate)
- Highly spontaneous

Question 22

Why is hydrolysis of ATP highly exergonic? (2)

Answer 22

1. Goes from high potential energy to lower potential energy when more stable ADP and P are formed from ATP
2. Entropy of product molecules is higher than reactants (ADP and P vs only ATP) —> more molecules in products

Question 23

Why does ATP have high potential energy making it less stable?

Answer 23

3 phosphates with negative charges = high repulsion

Question 24

How is ATP hydrolysis used in cells?

Answer 24

• ATP hydrolysis produces energy as heat, but cells use the energy to make things happen
• ATP hydrolysis is used to alter molecules in order to perform synthesis, transport and mechanical work

Question 25

What is phosphorylation?

Answer 25

From ATP hydrolysis (ADP + P): transfer the phosphate to another molecule

Question 26

What can ATP/ATP hydrolysis do? (3 + description)

Answer 26

1. Activate reactants to perfom synthesis work
   - Phosphorylation of a reactant INCREASES its potential energy and produces an “ACTIVATED” reactant
   - Converts an ENDERGONIC reaction into an EXERGONIC reaction
   - First: reaction is non-spont., but COUPLED with ATP hydrolysis —> OVERALL spontaneous reaction
2. Phosphorylate transport proteins to perform transport work
   - Phosphorylation of protein causes protein to change its SHAPE —> change its ACTIVITY
   - Causes transport protein to do transport work
   - Protein phosphorylation is also used to REGULATE activity of other proteins
3. Interact with motor proteins to perform mechanical work
   - NOT phosphorylation: NON-COVALENT interaction of ATP with a motor protein —> ATP hydrolysis causes protein to change shape & change its INTERACTION with the CYTOSKELETON
   - Cause MOVEMENT at molecular level
   - BASIS of movement at cell & organismal level

Question 27

What is energy metabolism?

Answer 27

• Sources of ENERGY produced via
  1. photosynthesis
  or gained via
  2. ingestion, digestion, absorption
  can be TRANSFORMED into useable energy & STOED in organisms (starch, glycogen)
• Cellular respiration & fermentation can transform energy in GLUCOSE into ATP —> then ATP can be used to POWER CELLULAR WORK

Question 28

Organic molecules (carbohydrates, fats) have high chemical energy. What is chemical energy?

Answer 28

Potential for a molecule to be transformed in a chemical reaction
- Determined by the BONDS in that molecule
- Associated with large decrease in free energy when molecule is broken down

Question 29

Having high chemical energy is synonym is being…

Answer 29

good fuels in energy metabolism

Question 30

Why do organic molecules have high chemical energy?

Answer 30

• Lots of C-H non polar bonds: the more C-H bonds, the higher the chemical energy, the better the fuel
• C-H non polar bonds = “hilltop” electrons because they are equally shared between two atoms —> loosely held in between
• Polar bonds = “bottom” electrons because they are tightly associated with the more electronegative atom

—> Non polar bonds with loosely held electrons have more chance to react and to be transformed in a chemical reaction