Activated Carriers

Flashcards covering activated carrier molecules, the groups they carry, and their roles in metabolism (ATP, NADH/NADPH, CoA, biotin, SAM, UDP-glucose, and related enzymes).

What is the general role of activated carrier molecules in metabolism?

They store energy in easily exchangeable forms and couple energetically unfavorable reactions to favorable ones, and provide chemical groups for biosynthetic reactions.

Name examples of activated carrier molecules widely used in metabolism.

ATP, GTP, NADH, NADPH, FADH2, Acetyl-CoA, carboxylated biotin, S-adenosylmethionine, and UDP-glucose.

In ATP, what high-energy group is carried and what is the linkage?

The phosphate group, stored in phosphoanhydride bonds.

What bonds store energy in ATP?

Phosphoanhydride bonds between the phosphate groups.

Which ATP bond cleavage is said to yield maximum energy release, and which phosphate group is transferred easily?

Cleaving the alpha-beta phosphoanhydride bond yields maximum energy; the gamma phosphate is transferred easily to other compounds.

What is carried by NADH and NADPH?

Electrons and hydrogens (reducing equivalents).

What molecule carries acetyl groups in metabolism?

Acetyl-CoA.

What does carboxylated biotin carry?

A carboxyl group.

What does S-adenosylmethionine (SAM) donate?

A methyl group.

What does UDP-glucose carry?

A glucose moiety.

What is the note about CoA regarding acyl groups?

CoA can carry any acyl group.

Which vitamin is associated with the NAD+/NADP+ system, and what is its ring?

Vitamin B3 (niacin) with the nicotinamide ring.

Which vitamin is associated with FAD/FADH2?

Vitamin B2 (riboflavin) with the flavin moiety.

How many electrons and protons does FADH2 carry?

Two electrons and two protons.

How do NADPH/NADP+ and NADH/NAD+ differ in terms of enzyme interactions and cellular roles?

NADPH/NADP+ are used in anabolic (biosynthetic) reactions; NADH/NAD+ are used in catabolic reactions; they bind to different enzymes, and the phosphate presence/absence mainly alters enzyme binding rather than electron transfer capability.

Which enzyme uses carboxylated biotin to transfer a carboxyl group, and what reaction is involved?

Pyruvate carboxylase; it transfers a carboxyl group to pyruvate to form oxaloacetate (carboxylation in metabolism).