Module 6: Making Life Work

Question 1

Why do cells need energy?

Answer 1

they need the energy to do the work of the cell.
- movement, growth, pump ions, perform reactions

Question 2

Phototroph

Answer 2

Obtain energy form the sun
- plants are most common

Question 3

Chemotroph

Answer 3

obtain energy from chemical compounds
- animals

Question 4

Autotroph

Answer 4

organism can convert CO2 into glucose since they make own organic source of carbon

Question 5

Heterotroph

Answer 5

organism is unable to convert CO2 and must ingest other organisms/molecules for a source of carbon

Question 6

What is metabolism?

Answer 6

chemical process that occur in a living organism to maintain life
- includes the building up and breakdown of chemical compounds. allows energy to be harnessed or released
- these reactions are continuously happening in cells
- many of these reactions are linked in such a way that the products of one are the reactants of another

Question 7

What are the two branches of metabolism?

Answer 7

Anabolism:** building** of molecules from smaller units, *requires an input *of energy (ATP)
Catabolism: breakdown of molecules into smaller units, produces energy (ATP)

Question 8

ATP

Answer 8

Adenosine triphosphate
- provides energy in a form that all cells can readily use to perform work of the cell
- the ATP molecule contains energy in its chemical bonds

Question 9

Potential energy

Answer 9

Energy that is not associated with movement but rather is stored

Question 10

Kinetic energy

Answer 10

energy of motion

Question 11

Chemical energy

Answer 11

chemical bonds between pairs of atoms in a molecule hold onto a form of potential energy

Question 12

Bond strength and potential energy are…

Answer 12

linked
- strong bonds = less PE
- weak bonds = more PE

Question 13

ATP has ___ amount of energy. Why?

Answer 13

high.
- the bonds between phosphate groups are weak
- has high PE
- when bonds between the phosphate groups are broken, the potential energy is released for cell to do work

Question 14

Do cells use all their energy at once?

Answer 14

no.
they keep it stored in a chemical form that is readily accessible to the cell
- most common chemical form used by the cell is ATP, the energy currency of the cell

Question 15

ADP

Answer 15

two phosphate groups

Question 16

AMP

Answer 16

one phosphate group

Question 17

First Law of Thermodynamics

Answer 17

energy can neither be created nor destroyed
- energy can be converted from one form to another
- when e- move from higher to lower energy level, energy released as heat or light

Question 18

Second Law of Thermodynamics

Answer 18

events in the universe have direction, proceed from higher energy to lower energy
- these events are thermodynamically favourable and are said to to be spontaneous, no input of external energy
- results in a reduction in the amount of usable energy because energy transformations are not 100% efficient

Question 19

Gibbs free energy

Answer 19

the amount of energy in a system available to do work
- delta G is the symbol for the difference in Gibbs free energy between R and P of a chemical process

Question 20

Delta G is +

Answer 20

the products of a reaction have more free energy then the reactants
- thermodynamically unfavourable, endergonic
- needs an input of energy

Question 21

Delta g is -

Answer 21

the reactants have more free energy then the products
- thermodynamically favourable, exergonic
- energy is available for use in another process (release energy)

Question 22

dG = dH - TdS

d = delta

Answer 22

H = total energy (enthalpy)
G = energy available to do work
S = energy lost to entropy or disorder
T = absolute temperature in Kelvin

Question 23

What happens when ATP is hydrolyzed?

Answer 23

The reaction of ATP with water is exergonic (spontaneous) and releases energy (-dG)
- at physiological pH the phosphate groups in ATP are negatively charged and resist one another

Question 24

Activation Energy

Answer 24

• chemical transformations require the breakage of certain covalent bonds within the reactant
• reactants must contain sufficient kinetic energy to overcome the activation energy barrier (Ea)
• enzymes catalyze reactions by decreasing magnitude of Ea barrier so reaction can proceed
• cells can carry out many reactions with a +dG (unfavourable)

Question 25

What are the two reasons cells carry out a +dG reaction, which is unfavourable?

Answer 25

1. relative concentrations of reactants to products is maintained above that defined by equilibrium constant
2. coupling endergonic and exergonic reactions
   - ex, hydrolysis of ATP drives endergonic reactions

Question 26

How are chemical reactions catalyzed?

Answer 26

chemical reactions are catalyzed by proteins called enzymes (“ase”= enzyme)
- active site of a an enzyme is formed by the assembly of certain amino acids in a three dimensional structure
- the enzyme active site binds the substrate(s) and converts it to the product
- the active site binds the substrate(s) and helps stabilize the transition state and lowers Ea

Question 27

Anabolic and catabolic reactions are catalyzed by __

Answer 27

enzymes

Question 28

Is it possible to affect enzyme activity?

Answer 28

yes
- enzyme activity can be reduced by two different kinds of inhibitors, reversible & irreversible
- enzyme activity can be increased by activators

Question 29

Negative feedback

Answer 29

• because energy is needed for chemical reactions, many metabolic pathways are regulated
• an example of regulation is where the final product in a pathway inhibits the first step of the reaction known as negative feedback
• important for maintaining balance in the cell and in helping the cell to conserve energy