17.1 - Energy Cycles

Question 1

Give 3 examples of metabolic activites (requiring energy)

Answer 1

• Active transport, e.g. used for the uptake of nitrates in root hair cells, phloem sucrose loading, selective reabsorption of glucose & aas in kidney and nerve impulse conduction
• Anabolic reactions: build up of polymers (proteins, polysaccharides, nucleic acids)
• Movement: cilia, flagella, contractile filaments in muscle cells

Question 2

What is the importance of the C-H bond?

Answer 2

• Energy used* to *break bonds (endothermic), energy released to form bonds (exothermic)
• Inorganic molecules (such as carbon dioxide and water), contain stronger bonds than organic molecules, so they require more energy to break and more energy to from than the weaker (albeit more abundant) organic bonds.
• During respiration, when large organic molecules are broken down into smaller inorganic ones, total energy required to break these bonds is less than the amount released when inorganic bonds form. Excess energy is used to synthesise ATP
• C-H bonds are non polar, don’t require lots of energy to break, when they break, they form strong C-O and H-O bonds which release lots of energy.