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Biochemistry Exam 1 Questions and Solutions
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Biochemistry Exam 1 Questions and Solutions
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Biochemistry Exam 1structure of amino acids - Answer -1. amino group (NH2)
2. carboxyl group (COOH)
3. Hydrogen
4. side chain (R)
How many amino acids are there? - Answer -20
vary in size, shape, charge, H-bonding(polarity) and chemical reactivity
Ampholyte (zwitterion) - Answer --near neutral pH
-carboxyl group loses a proton (H)
Ampholytes as zwitterions at a certain pH known as the molecules isoelectric point
*good buffers* resist change to pH of solution
isoelectric point (pI) - Answer --The pH at which molecule has a net zero charge
-The ionization & buffer capacity of AA is altered by change in pH of environment
,What will be the effect for the acidic and basic groups on amino acids or proteins when the pH of a
solution increases? - Answer -pH increases= Alkaline deprotonation occurs-> gives up proton-> neg
charge====ANION
pH decreases= basic gains a proton-> pos charge-> CATION
types of amino acids - Answer -Hydrophobic
Hydrophilic
Acidic
Basic
hydrophobic amino acids - Answer -(R- group nonpolar)
**Glycine
-Alanine (R=CH3)
- Leucine & Isoleucine (R=4 carbon chain)
- Valine ( R= 3 carbon chain)
- Phenylanlanine (R=phenyl ring)
- Tryptophan (R=indole ring)
- Proline & Methionine = unique
hydrophilic amino acids - Answer -UNCHARGED
*glycine
Serine & Threonine
,- Cysteine (-SH thiol ring),very reactive, affects
structure via disulfide bonds to form Cystine
- Tyrosine
- Glutamine & Aspargine have both carboxamide
side chain)
Acidic amino acids - Answer -(NET NEG CHARGE)
- aspartic acid and glutamic acid
basic amino acids - Answer -(NET POS CHARGE - accepted h+)
- Lysine (4 amino butyl side chain)
-Arginine (Guanidinium group side
chain)
- Histidine (has imidazole side chain)
Role of amino acids - Answer -1. Biosynthesis
2. Energy
Biosynthesis - Answer -- serves as building blocks for the synthesis of macromolecules
Protein synthesis- 75% of AA is needed and used
other macromolecules synthesis- heme, glycosamine, nucleotides, biogenic amines, etc.
Energy - Answer --AA in excess cant be stored or excreted
, -surplus is used as fuel
Most amino groups converted - Answer -urea--> urea cycle--> waste
carbon skeleton is oxidized to acetyl CoA; acetoacetyl Co A; pyurvate
Aminoacidopathies - Answer -inherited disorders of amino acid metabolism
abnormal specific enzyme in metabolic pathway or in the AA membrane transport system
-Phenylketonuria
- Tyrosinemia
- Alkaptonuria
- Maple Syrup Urine Disease
- Homocystinuria
Name a deficiency that can lead to hyperphenylalaninemia? - Answer -PKU or Phenylketonuria
Phenylketonuria - Answer --Autosomal recessive trait (1 in 15000 births).
-Absence of phenylalanine hydroxylase (PAH).
-Phe accumulates >1200 mmol/L & metabolized by alternative pathway resulting in **presence of
degradative substances in blood & urine****.
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