Chapter 6: Making Life Work

Question 1

What is ATP and why is it important?

Answer 1

Adenosine Triphosphate:
- Universal currency of all cells. - ATP provides the energy that all cells can readily use.
- The energy is contained in the molecules’ chemical bonds, which, when broken, release energy the cell can utilize.

• (ATP has adenine as the nitrogenous base, but guanine, cytosine, thymine, or uracil can also be used for the base (GTP, CTP, TTP, UTP). ATP is the best energy carrier, which is why it’s used more often. GTP is the next best carrier.)

Question 2

What are the 2 things that all organisms need? What are the differences between Chemotrophs and a Phototrophs?

Answer 2

** All organisms need carbon and energy!

CHEMOTROPHS: Get energy from chemical compounds, like glucose.

PHOTOTROPHS: Get energy from the Sun

Question 3

What are the differences between an autotroph and a heterotroph?

Answer 3

AUTOTROPHS: Producers (make their carbon from environment)

HETEROTROPHS: Consumers (get their carbon from environment)

Question 4

Describe and give examples for Chemoautotrophs and Chemoheterotrophs.

Answer 4

• Chemoautotrophs: receiv energy from inorganic chemicals and PRODUCE carbon from CO2
  (ex: many extremophiles)
• Chemoheterotrophs: receive energy from inorganic chemicals and CONSUME carbon from organic compounds
  (ex: all animals & humans)

Question 5

Describe and give examples for Photoautotrophs and Photoheterotrophs.

Answer 5

• Photoautotrophs: receive energy from sun and MAKE carbon from environmental CO2
  (ex: plants, algae)
• Photoheterotrophs: receive energy from sunlight and CONSUME carbon from organic sources
  (ex: purple/green nonsulfur bacteria)

Question 6

What is catabolism and anabolism and how are they related? Which one is endergonic and which one is exergonic?

Answer 6

METABOLISM is divided into two branches:
- Catabolism: the BREAKDOWN of molecules into smaller units, producing ATP (exergonic)
- Anabolism: the BUILDING of molecules from smaller units, requiring an input of energy (endergonic)

Question 7

Describe the general principles behind the first and second law of thermodynamics

Answer 7

First Law: ENERGY IS NEITHER CREATED NOR DESTROYED. New energy is never formed and energy is never lost. Energy just changes from one form to another.

Second Law: WHEN ENERGY CHANGES FORM, THE TOTAL AMOUNT OF ENERGY REMAINS CONSTANT. However, the energy available to do work (in this case within a cell) decreases. Therefore, there is a price (loss of energy to do work) when transforming energy. The amount of disorder (entropy) increases when energy is transformed.

Question 8

How do enzymes relate to activation energy of reactions?

Answer 8

Enzymes are CATALYSTS that can decrease the activation energy which accelerates the reaction.

Question 9

What is the difference between Endergonic and Exergonic reactions? Which one is spontaneous? Is ATP Hydrolysis endergonic or exergonic?

Answer 9

Endergonic: requires energy
(non-spontaneous)

Exergonic: releases energy
(spontaneous)

• (The reaction of ATP with water (ATP Hydrolysis) is exergonic because it releases energy)

Question 10

What is a substrate?
What is an enzyme inhibitor?

Answer 10

Substrate: The molecule (usually a protein) that an enzyme works on
Enzyme Inhibitor: Common substrate that the body uses to turn off enzymes

Question 11

How are enzymes inhibited? Why is this important?

Answer 11

Competitive Inhibition! Other molecules (enzyme inhibitors) compete for the active site of the enzyme

• Enzyme inhibition by small molecules serves as a major control mechanism of biological systems.