Learning Unit 1: Introduction to Biochemistry
1. How many different types of macromolecules are there? Name
them.
Three. Carbohydrates, nucleic acid and proteins
2. What do mitochondria do in the cell of a eukaryote?
In the cell of a eukaryote, mitochondria function as the producer of energy which
is in the form of ATP (adenosine triphosphate)
3. What is the function of smooth endoplasmic reticulum (ER)?
Smooth endoplasmic reticulum functions in metabolic processes
 Synthesis of lipids
 Carbohydrates and calcium concentration metabolism
 Detoxification of drug
4. Name two characteristics that distinguish eukaryotic cells from
prokaryotic cells
Nucleus


Prokaryote
Lack of membrane-bounded
nucleus but instead, has
nucleoid

Organelles
Ribosomes as their only type of

organelles
Eukaryote
Presence of membranebounded nucleus
Cells contain internal
membrane-bounded organelles
such as mitochondria and
chloroplasts
5. What advantage does a eukaryotic cell gain by having organelles
like
mitochondria, nucleus, etc?
Eukaryote cell is more complex. Being more complex compared to prokaryote
cell, the metabolism and energy conversion within a eukaryote cell is much more
delicate and thorough. Thus, these organelles, each with specific additional
functions are crucial in processes that would allow the cell to survive, grow and
reproduce.
6. What do the letters ‘pH’ stand for and what is the definition of pH?
“H” stands for hydrogen, in this case, the hydrogen cation (H+)
“p” is shorthand for “negative logarithm thereof”.
The term refers to the negative logarithm of the hydrogen cation concentration,
which determines the acidity/basicity of solution in that certain solution.
a) What is the [CH3COOH]/[CH3COO-] ratio in acetate buffer at pH
4.2?
For [CH3COOH] = HA, [CH3COO-] = A- , pKa = 4.8
pH
= pKa + log([A-]/[HA])
4.2
= 4.8 + log([A-]/[HA])
4.2 – 4.8 = log([A-]/[HA])
-0.6
= log([A-]/[HA])
[A-]/[HA]
= -log (-0.6)
= 0.25
therefore we see it as: [A-] = 0.25 = 1
[HA]
1
4
b) You want to prepare 1 liter of 0.10 M buffer using NaHCO3 and
Na2CO3.
Calculate the mol of each required for a buffer at pH = 9.9.
For NaHCO3 = HA, Na2CO3 = A- , pKa = 10.2
pH
= pKa + log([A-]/[HA])
9.9
= 10.2 + log([A-]/[HA])
9.9 – 10.2 = log([A-]/[HA])
(-0.3)
= log([A-]/[HA])
[A-]/[HA]
= -log (-0.3)
= 0.5
therefore we see it as: [A-] = 0.5 = 1
[HA]
2
Moles required = 1L × 0.10 M
= 0.10 mol
Fraction NaHCO3 = 0.5
1 + 0.5
= 0.33
Fraction Na2CO3 = 1- 0.33
= 0.67
c) The crystalline salt of ammonium acetate (0.10 mol) was dissolved
in 1 liter of
water. Calculate the pH.
pKa = 4.8
pKa = 9.2
pH = (pKa + pKa)/ 2 = (4.8/9.2)/ 2
=7