Workshops Flashcards
A chemical reaction for which the associated enthalpy change (delta H) is positive:
A) Cannot occur spontaneously
B) May occur spontaneously if coupled to a reaction in which the enthalpy change is negative and of greater magnitude
C) Raises the temperature of the surroundings
D) Will inevitably occur spontaneously
B) May occur spontaneously if coupled to a reaction in which the enthalpy change is negative and of greater
When may a chemical reaction with a positive enthalpy change occur?
Spontaneously if coupled to a reaction in which enthalpy change is greater and more negative
A chemical reaction for which the associated free change (delta G) is large and negative:
A) Cannot occur spontaneously
B) Is likely to be irreversible in the cell
C) Will inevitably occur spontaneously
D) Will occur very rapidly
B) Is likely to be irreversible in the cell
When is a reaction likely to be irreversible?
A chemical reaction for with the free energy change is large and negative
What is a polar molecule?
A) a molecule with no charge
B) a molecule with opposite charges at opposite ends
C) a molecule with identical charges at opposite ends
D) a molecule with an unequal number of protons and electrons
B) a molecule with opposite charges at opposite ends
How does water arrange around ions?
A) the more negative atoms attach to positive ions
B) the more positive atoms attach to negative ions
C) water forms a hydration shell
D)All of these are true
D) all of these are true
How does water arrange around ions?
More negative atoms attach to positive ions. More positive atoms attach to more negative ions. Water forms a hydration shell
Which is true regarding the structure go hydrogen bonds?
A) hydrogen bonds can only arise from the covalent interaction between oxygen and hydrogen atoms
B) It os only the hydrogen atoms of a water molecule which interact with polar molecules
C) hydrogen bonds involve a linear arrangement of one hydrogen atom between 2 electronegative atoms
D) Hydrogen bonds are angled at 104.3 degrees
C) hydrogen bonds involve a linear arrangement of one hydrogen atom between 2
Characteristics of hydrogen bonds
Linear arrangement
Bond between hydrogen atom and electronegative atom
104.5 degrees bond angle
Which of the following about amino acids is correct?
A) Amino acids are classified according to the structures and properties of their side chains
B) Amino acids are uncharged at neutral pH
C) Amino acids in proteins are mainly in the D- configuration
D) Twenty four amino acids are commonly used in protein synthesis
A) Amino acids are classified according to the structures and properties of their side
What happens to amino acids at a neutral pH
They reach their iso-electric point
Have an overall charge of 0
Precipitate out of solution
All amino acids contain an alpha carbon bonded to the following structures
A) An amino group (-NH2), a carboxyl group (-COOH), a hydrogen (-H), a side chain (-R)
B) an amide group (-CONH2), a carboxyl group (-COOH), a hydrogen (-H), a side chain (-R)
C) an amino group (-NH2), a carboxyl group -COOH), a hydroxyl group (-OH) , a side chain (-R))
D) an amide group (- CONH2), a hydrogen (-H), a side chain (-R)
A) An amino group (-NH2), a carboxyl group (-COOH), a hydrogen (-H), a side chain (-R)
Which of the following statements is true about a peptide bond? (RCONHR’)
A) it is not planar
B) It is capable of forming a hydrogen bond
C) Electron resonance between amino and carbonyl groups creates a partial double bond
D) the cis configuration is favoured over trans configuration
C) Electron resonance between amino and carbonyl groups creates a partial double bond
What does negative delta G mean?
Reaction is thermodynamically favourable/ feasible
How do you change a negative value of delta G to a positive value of delta G?
Have a negative value for InKeq
- this is done by changing concentration of reactants and products so that numerator is smaller than denominator
What does positive enthalpy mean?
Heat is being absorbed by the system
What is the standard free energy of a life process?
Delta G prime
What is Keq?
Ratio of products over reactants
During the formation of the peptide bond, what takes place?
The alpha amino group of one amino acid acts as a nucleophile to displace the hydroxyl group of another amino acid forming a peptide bond
Compare solution A with pH=4 to solution B with pH= 6
A) concentration of H+ in solution A is twice than that in solution B
B) Solution A has greater buffering capacity than solution B
C) The concentration of H+ in solution A is 100 times than that in solution B
D) The hydroxide concentrations are equal in the two solutions since pH only measures the concentration of H+
C) The concentration of H+ in solution A is 100 times than that in solution B
What is the log scale for pH 4 and pH 6?
0.0001/ 0.000001 = 100
How many zeros does pH 1 have
0.1
Two weak acids, A and B, have pKa values of 4 and 6 respectively. Which statement is true?
A) Acid A dissociates to a greater extent in water than acid B
B) For solutions of equal concentration, acid B will have a lower pH
C) B is the conjugate base of A
D) Acid A contains more ionising groups than acid B
E) The equivalence point of acid A is higher than that of acid B
A) Acid A dissociates to a greater extent in water than acid B
Explain how pKa acids are smaller with increasing strength
Strong acids favour [H+][A-] so ratio to [HA] gives a larger value. Since pKa= lopKa, values become smaller with increasing acid strength.
