12.1. Energy

Question 1

The need for energy in living organisms

Answer 1

illustrated by anabolic reactions such as:

• DNA replication and protein synthesis
• active transport
• movement (like muscle contraction)
• the maintenance of body temperature
• transmission of nerve impulses

Question 2

Anabolic Reactions

Answer 2

Energy consuming reactions

Question 3

ATP stands for

Answer 3

Adenosine Triphosphate

Question 4

ATP structure

Answer 4

Similar to RNA

• 3 phosphates
• Ribose
• Adenine

Question 5

ATP function

Answer 5

• “the energy currency in every living cell”
• Releases energy when hydrolysed (loses one of its phosphate groups)
• ATP –> ADP

Question 6

ATP + H2O –> (reversible)

Answer 6

ADP + H3PO4 (Phosphoric Acid) ± 30.5 kJ

Question 7

ADP stands for

Answer 7

Adenosine Diphosphate

Question 8

How is ATP synthesised

Answer 8

1) substrate-linked reactions in glycolysis and in the Krebs cycle
2) electron transport chain on the membranes of mitochondria and chloroplasts

Question 9

How is ATP synthesised by substrate-linked reactions in glycolysis and in the Krebs cycle

Answer 9

In respiration, energy released by reorganising
chemical bonds (chemical potential energy) during
glycolysis and the Krebs cycle is used to make some ATP.

Question 10

How is ATP synthesised by electron transport chain on the membranes of mitochondria and chloroplasts

Answer 10

• most ATP in cells is generated using electrical potential energy.
• This energy is from the transfer of electrons by electron carriers in mitochondria and chloroplasts.
• It is stored as a difference in proton (hydrogen ion) concentration across some phospholipid membranes in mitochondria and chloroplasts, which are essentially impermeable to protons.
• Protons are then allowed to flow down their concentration gradient (by facilitated difusion) through a protein that spans the phospholipid bilayer.
• Part of this protein acts as an enzyme that synthesises ATP and is called ATP synthase.
• The transfer of three protons (from high concentration of hydrogen ions outside the mitochondria / chloroplast to lower concentration of hydrogen ions inside) allows the production of one ATP molecule, provided that ADP and an inorganic phosphate group (Pi) are available inside the organelle.

Question 11

Where is ATP synthesised?

Answer 11

(electron transport chain)

• matrix of the mitochondria
• stroma of chloroplast

Question 12

Coenzymes function

Answer 12

A molecule required for an enzyme to catalyse a reaction

Question 13

Coenzymes in respiration

Answer 13

NAD, FAD and Coenzyme A

Question 14

What is the function of NAD and FAD during respiration?

Answer 14

• Both NAD and FAD are reduced during respiration
• By “reducing” means to add hydrogen, so reduced NAD means to add hydrogen
• They receive and transport hydrogen ions
• Without the presence of NAD or FAD to accept the hydrogen, the dehydrogenase enzymes involved in respiration would not be able to remove hydrogen from their substances

Question 15

What happens when a substance is “reduced”?

Answer 15

• Lose Oxygen
• Gain Electrons
• Gain Hydrogen

Question 16

What happens when a substance is “oxidised”?

Answer 16

• Gain Oxygen
• Lose Electrons
• Lose Hydrogen

Question 17

Loss of an electron from a hydrogen atom

Answer 17

H –> H+ + e-
The loss of an electron forms a hydrogen
ion, which is a single proton.

Question 18

ATP synthase function

Answer 18

enzyme for synthesis of ATP
- has 3 binding sites
- a part of the molecule (γ) that rotates as hydrogen ions
(H+) pass. 
- This produces structural changes in the binding sites and allows them to pass sequentially through three 
phases:
■■ binding ADP and Pi
■■ forming tightly bound ATP
■■ releasing ATP.