Phosphorylated nucleotides

Question 1

What processes do cells require energy for?

Answer 1

1) Synthesis - e.g. of large molecules such as proteins
2) Transport - e.g. pumping molecules or ions across cell membranes by active transport.
3) Movement - e.g. protein fibres in muscle cells that cause muscle contraction.

Question 2

What is ATP?

Answer 2

• Adenosine Triphosphate (ATP) is a molecule that supplies energy in cells.
• Composed of nitrogenous base, pentose sugar and 3 phosphate groups.
• Unlike DNA and RNA, in ATP, the base is ALWAYS ADENINE.
• Sugar is ribose.

Question 3

Hydrolysis of ATP

Answer 3

• Large amounts of energy released when liberated phosphate undergoes other reactions involving bond formation.
• More energy is released than used, approx. 30.6 kJmol-1
• Removal of phosphate group is hydrolysis reaction.
• ATP + H20 -> ADP + Pi + energy
• ADP = Adenosine Diphosphate; Pi = inorganic phosphate.
• Hydrolysis of ATP happens in association w/ energy-requiring reactions.

Question 4

Why is ATP not a good long term store?

Answer 4

• Instability of phosphate bonds mean that it is not a good long term energy store. Fats and carbo. are better for this.
• Energy released in breakdown if these molecules is used to make ATP.
• This occurs by reattaching phosphate group to ADP molecule - this is Phosphorylation
• Water is removed so it’s a condensation reaction.
• ATP is good immediate energy store.

Question 5

Properties of ATP

Answer 5

• Small: moves easily into, out of and within cells
• Water soluble: processes happen in aqueous env.
• Contains bonds between phosphates w/ intermediate energy: large enough for cellular reactions but not so large that energy is wasted as heat
• Releases energy in small quantities
• Easily regenerated

Question 6

How does a nucleotide become phosphorylated?

Answer 6

To phosphorylate a nucleotide, you add one or more phosphate groups to it.