1.10 - Protein and Nucleic Acid Metabolism

Question 1

major purposes of metabolism (3)

Answer 1

1. performance of mechanical work in muscle contraction and cellular movements
2. active transport of molecules and ions
3. synthesis of macromolecules from simple precursors

Question 2

how are toxic amino/ammonia by-products removed

Answer 2

the urea cycle

Question 3

what are amino acids broken down into? (2)

Answer 3

1. amino group
2. carbon skeleton

Question 4

what does the carbon skeleton of amino acids feed into?

Answer 4

fundamental metabolic processes

Question 5

what are amino acids precursors for?

Answer 5

hormones and neurotransmitters

Question 6

how are proteins ingested, absorbed and transported?

Answer 6

via intestinal lumen and moved via hepatic portal vein to liver

Question 7

what do muscle cells use as energy source during metabolic starvation or intense exercise?

Answer 7

branched chain amino acids (BCAA)

Question 8

role of liver in protein metabolism

Answer 8

fundamental in protein metabolism and amino acid recycling

Question 9

role of liver cells in urea cycle

Answer 9

remove ammonia (toxic byproduct of amino acid breakdown)

Question 10

essential amino acids (2)

Answer 10

1. body cannot synthesise on its own
2. must be acquired through diet or supplements

Question 11

non-essential amino acids (2)

Answer 11

1. can be synthesised by our body
2. synthesised using aminotransferases (transaminases)

Question 12

types of amino acid (4)

Answer 12

1. neutral amino acids
2. acidic amino acids
3. basic amino acids
4. branched chain amino acids

Question 13

neutral amino acid properties

Answer 13

do not carry charge in R group

Question 14

role of neutral amino acids (2)

Answer 14

1. alanine plays vital role in glucose-alanine cycle:
2. glucose converted into key intermediated pyruvate through activity of alanine aminotransferase (not only alanine used to make pyruvate)

Question 15

acidic amino acids (2)

Answer 15

1. glutamate
2. aspartate

Question 16

acidic amino acid properties

Answer 16

carry negative charge on R group at certain pH

Question 17

role of acidic amino acids in enzymes

Answer 17

often crucial in active site of enzymes as they interact with metal ions (i.e. Mg2+)

Question 18

metabolic role of acidic amino acids

Answer 18

vital intermediate and participate in TCA cycle and nitrogen removal

Question 19

role of acidic amino acids in nuerotransmission

Answer 19

glutamate is most abundant excitatory neurotransmitter in CNS

Question 20

basic amino acid properties

Answer 20

carry positive charge on R group at certain pH

Question 21

role of basic amino acids in epsilon amino group

Answer 21

crucial sites of covalent linkage

Question 22

role of basic amino acids in urea cycle

Answer 22

important intermediates, crucial for removal of toxic by-products of amino acid catabolism

Question 23

branched amino acid properties

Answer 23

contain branched chain R group

Question 24

role of branched chain amino acids in oxidation in muscles

Answer 24

can be used as temporary substitute for fatty acids as fuel for oxidation in muscles during short-term starvation

Question 25

what is required before branched chain amino acids can participate in metabolic events?

Answer 25

require glucose-alanine cycle to remove nitrogen from the amino groups

Question 26

role of branched chain amino acids in protein structure

Answer 26

very hydrophobic and important for protein structure

Question 27

what catalyses the metabolism of ketogenic amino acids into ketone bodies?

Answer 27

acetyl CoA

Question 28

what catalyses the metabolism of glucogenic amino acids into glucose?

Answer 28

pyruvate and oxaloacetate

Question 29

purine amino acid bases (2)

Answer 29

1. adenine 2. guanine

Question 30

pyrimidine amino acid bases (3)

Answer 30

1. cytosine 2. thymine 3. uracil

Question 31

structure of all amino acid bases

Answer 31

heterocyclic rings with both C and N

Question 32

functions of nucleotides (4)

Answer 32

1. ATP/GTP/CTP/TTP undergoing energy transduction 2. substrates for RNA and DNA biosynthesis 3. can be attached to coenzymes 4. metabolic regulators

Question 33

role of nucleotides in energy transduction

Answer 33

ATP most common energy transducer (other nucleoside triphosphates also provide energy in some situations)

Question 34

role of nucleotides as substrates for RNA and DNA (2)

Answer 34

1. 4 ribonucleoside triphosphates are essential substrates for RNA synthesis 2. 4 2'-deoxyribonucleoside triphosphates essential substrates for DNA replication

Question 35

role of nucleotides as metabolic regulators (2)

Answer 35

1. ATP prime carboxyl group of fatty acid to give acyl adenylate 2. acyl adenylate then replaced by CoA

Question 36

glucagon action on cAMP

Answer 36

activates cAMP cascades in liver

Question 37

epinephrine action on cAMP

Answer 37

activates cAMP cascades in muscle

Question 38

result of rise in cAMP (in muscles and liver)

Answer 38

activation of glycogen phosphorylase

Question 39

when do epinephrine levels rise greatly?

Answer 39

during exercise, when metabolic demands of muscles are high

Question 40

signal transductions by cAMP (3)

Answer 40

1. hormone acts as 1st messenger, activates receptor in plasma membrane (leading to dissociation of trimeric G-proteins) 2. exchange of GTP for GDP on Gas -> activation of adenylate cyclase and cAMP formation (2nd messenger) 3. cAMP activates cAMP-dependant protein kinase (PKA) -> phosphorylation of protein -> physiological response

Question 41

kinase

Answer 41

transfer phosphate groups from ATP to proteins

Question 42

phosphorylase

Answer 42

catalyse transfer of a phosphate group from donor to acceptor/substrate molecule

Question 43

effect of cAMP in muscle in response to epinephrine

Answer 43

cAMP cascade -> phosphorylation of serine hydroxyl of muscle glycogen phosphorylase -> promotes transition to active (relaxed) state