Module 3 WK9+10+11 Flashcards
Which term describes the inactive form of an enzyme?
Apoenzyme
Which term describes the active form of an enzyme?
Holoenzyme
Which type of organic molecules are tightly or covalently bound to an enzyme?
Coenzymes
What are molecules that diffuse to and bind an enzyme for its catalytic activity then diffuse away?
Cosubstrates
What is the main function of B-group vitamins?
Haematopoiesis and energy production
Which type of molecules are metal ions loosely or tightly bound to an enzyme?
Cofactors
Most B-group vitamins are bioactive only as coenzymes.
true or false
true
B vitamins correct name to the corresponding vitamin.
Vitamin B1: thiamin
Vitamin B2: riboflavin
Vitamin B3: niacin
Vitamin B5: pantothenic acid
Vitamin B6: pyroxidine
Vitamin B7: biotin
Vitamin B9: folate
Vitamin B12: cobalamin
What is the coenzyme form of thiamin?
Thiamin diphosphate (TDP)
In what form is thiamin present in plant products?
Free thiamin
What is the role of thiamin diphosphate (TDP) in the oxidative decarboxylation of pyruvate?
TDP is a coenzyme for pyruvate decarboxylase
role of thiamin in the pentose phosphate pathway?
Thiamin is a coenzyme of transketolase in the pentose phosphate pathway
In which food product is mandatory fortification of thiamin required in Australia?
Bread-making flour
What are thiamin antagonists?
Chemical compounds that lower the bioavailability of thiamin
What is the name of the type of beriberi caused by alcohol use disorder?
Wernicke-Korsakoff syndrome
good animal source of thiamin?
Pork
coenzyme forms of riboflavin
The two coenzyme forms of riboflavin are flavin mononucleotide and flavin adenine dinucleotide
FMN and FAD in food need to be converted to riboflavin for absorption
What is the primary function of FAD and FMN in the body?
Act as electron carriers in oxidation-reduction reactions
What is the role of riboflavin in the synthesis of niacin?
Riboflavin acts as a coenzyme in the conversion of tryptophan to niacin
good dietary source of riboflavin?
Dairy products
sign of riboflavin deficiency?
Lesions on the corner of the mouth
Niacin can be endogenously synthesised from which amino acid?
Tryptophan
coenzyme form of niacin?
NADP, NAD+, NADH, NADPH
function of niacin?
Acts as an electron carrier in oxidation-reduction reactions
Niacin is found in animal products as…
Nicotinamide
Animal products (meat and fish) are better sources of niacin than plant products.
true or false
true
good plant source of niacin?
Peanut butter
Niacin deficiency can lead to pellagra. What are the symptoms of pellagra?
Dermatitis, diarrhea, dementia, and even death
What is the upper level (UL) for niacin based on preventing?
Peripheral vasodilation
What are the coenzyme forms of pantothenic acid?
4’-phosphopantetheine and coenzyme A
absorption of pantothenic acid?
The coenzyme forms of vitamin B5 must be converted to pantothenic acid for absorption
functions of 4’-phosphopantetheine?
To act as a coenzyme in fatty acid production
To convert folate to its coenzyme form
function of acetyl-CoA in the body?
Synthesis of cholesterol and steroid hormones
Synthesis of fatty acids and ketones
Modification of proteins through post-translational acetylation
Synthesis of acetylcholine, a neurotransmitter
pantothenic acid deficiency symptom?
Burning feet syndrome
Which is the most stable form of vitamin B6?
Pyridoxine
What is the coenzyme form of vitamin B6?
Pyridoxal phosphate
All 6 forms of vitamin B6 are found in food.
true or false
true
All forms of vitamin B6 can be converted to PLP in the liver.
true or false
true
What is the primary role of PLP as a coenzyme?
Amino acid metabolism
function of PLP?
Conversion of homocysteine to cysteine
Deamination of amino acids for energy production and gluconeogenesis
Synthesis of neurotransmitters from amino acids
Synthesis of non-essential amino acids
common symptom of vitamin B6 deficiency?
Microcytic, hypochromic anaemia
What can result from vitamin B6 toxicity?
Nerve damage
coenzyme form of Biotin
carboxybiotin
Biotin is a water-soluble vitamin that acts as a coenzyme in various…
carboxylase enzymes
Biotin can be found in food in its.. (form) … freed by… for absorption
free form or bound to lysine residues in protein to form biocytin, which is then freed by the enzyme biotinidase for absorption.
carboxybiotin function
several metabolic pathways. Biotin is important for the conversion of pyruvate to oxaloacetate in gluconeogenesis and the conversion of acetyl-CoA to malonyl-CoA in fatty acid synthesis. Biotin is also involved in the biotinylation of histone proteins, which promotes gene expression.
Good dietary sources of biotin
liver, soybeans, and eggs.
association between raw egg and biotin
raw egg consumption can lead to biotin deficiency due to the tight binding of biotin to the protein avidin in raw egg whites, which prevents its absorption.
symptoms of biotin deficiency
dermatitis, hypotonia, nervous system dysfunction, and alopecia.
Why is folic acid more efficiently absorbed than naturally occurring folate?
Folic acid contains only one glutamic acid residue, while naturally occurring folate typically contains three or more.
What is the digestive enzyme that converts the polyglutamate form of folate to the monoglutamate form for absorption?
Folate conjugase
What is the primary role of folate?
Providing one-carbon units for methylation reactions
functions of folate?
Pyrimidine synthesis
Amino acid metabolism
Purine synthesis
Methylation reactions
Which reaction requires 5-methyltetrahydrofolate (5-MTHF)?
The conversion of homocysteine to methionine
symptom of folate deficiency?
Megaloblastic anemia
Why is the upper level (UL) for folate set at 1000 μg?
Because high doses may mask vitamin B12 deficiency
Which of the forms of vitamin B12 are used in fortified foods and supplements?
Hydroxocobalamin and cyanocobalamin
two coenzyme forms of vitamin B12?
Methylcobalamin and 5-deoxyadenosylcobalamin
How long can the body’s stores of vitamin B12 last?
3-5 years