IB Biology Review
Topic 3: Chemistry of Life
Vocabulary
Macromolecule
term used to describe large molecules such as
carbohydrates, lipids, proteins, and nucleic acids
Monomer
the repeating unit molecules of polymers
Polymer
a long chainlike molecule consisting of repeating
building-block molecules linked by covalent bonds
includes proteins, carbohydrates, and nucleic acids
What are the four
groups of macromolecules?
Carbohydrates
Lipids
Proteins
Nucleic Acids
Examples of Monomers
What are the monomers of
Carbohydrates
Simple sugars (monosaccharides) like glucose
and fructose make polysaccharides
Proteins
20 different amino acids form polypeptides
Nucleic Acids
Nucleotides (A, T, G, C, and U) form DNA and
RNA
How are monomers linked and unlinked?
Linked by condensation/dehydration reaction
A molecule of water is removed to form a bond
Anabolic reaction
•
Unlinked by hydrolysis reaction
–
–
A molecule of water is added to break a bond
Catabolic reaction
Two Types of Covalent Bonds that Join
Monomers
Saccharide bonds join two adjacent
monosaccharides
Peptide bonds join two adjacent amino acids
MC-1.Which of the following reactions occurs
when a dipeptide is formed from amino acids?
A.
B.
C.
D.
hydrolysis
denaturation
condensation
oxidation
Correct answer: C
Special Types of Bonds
Two monosaccharides are joined by a
saccharide bond
•
Two amino acids are joined by a
–
peptide bond
DNA Structure
1. Alternating sugar and phosphate molecules
2. Bases are towards center (A/T) (G/C)
3. Hydrogen bond connects adjacent base pairs
2
4. Double helix
1
structure (twisted
ladder of
polynucleotides)
4
3
DNA Nucleotide Structure
Single nucleotide subunit
Deoxyribose (sugar)
molecule binds to phosphate
at the Carbon III and V
positions
MC-2. What is the composition of the
backbone of DNA?
A.
B.
C.
D.
alternating sugar and phosphate
molecules
complementary base pairs
alternating sugar and base molecules
a polysaccharide
Correct answer: A
Structure of Ribose and Glucose
Ribose has five carbon molecules
Glucose has six carbon molecules
Be able to draw these structures!
IB Required Monosaccharides
IB wants you to be able to list the
following monosaccharides
Glucose
Ribose
Fructose
Glyceraldehyde
Galactose
Monosaccharides always have a 1:2:1
carbon: hydrogen: oxygen ratio
Example: Glucose is C6H12O6
IB Required Disaccharides
IB wants you to be able to list the
following disaccharides
Sucrose (glucose and fructose)
Lactose (glucose and galactose)
Maltose (glucose and glucose)
table sugar
milk sugar
starch in seeds
IB Required Polysaccharides
IB wants you to be able to list the
following polysaccharides
Cellulose
Glycogen
Starch
cell walls
energy storage in animals
energy storage in plants
Structure of Fatty Acids
IB needs you to know this structure:
Where n stands for the different number of
carbon molecules that can be added or
removed to change the length of the chain
Structure of Fatty Acids
Saturated Fatty Acids
Have no double carbon bonds in any of three tails
Usually solid at room temperature
Example: butter
Unsaturated Fatty Acids
Have at least one double carbon bond in tails
Usually liquid at room temperature
Example: cooking oil
Which is better for you?
Unsaturated fatty acids
Phospholipid Structure
Molecules in the phospholipid
bilayer in cell membrane
Lipid Function
Energy storage / energy supply
Hormone production
Cushioning / protection
Insulation
Constituent of cell membrane (part of
phospholipid bilayer)
Energy Storage
Carbohydrates
–
–
–
Stored as glycogen in animals (in liver)
Stored as starch in plants (in roots)
More easily digested than lipids so energy
can be released more quickly
Lipids
–
–
–
Stored as fat in animals
Long-term energy storage
More energy per gram than carbohydrates
Health Risks of Lipids
Saturated fatty acids cause high
cholesterol
Athersclerosis / narrowing of (lumen of)
arteries
Hypertension / high blood pressure
Obesity / overweight
Amino Acid Structure
Twenty different amino acids
All share the same base:
What differs in each amino acid is “R” or the
side chain
Protein Structure
Primary Structure
The unique sequence of amino acids, each linked
together by a peptide bond
Secondary Structure
The Beta-pleated sheets and Alpha-helix structures
Tertiary Structure
in globular proteins involves the folding of polypeptides.
This folding pattern is stabilized by several types of
bonds including hydrogen bonds and ionic bonds
Quaternary Structure
of proteins is the linking together of two or more
polypeptide subunits. An example of this is hemoglobin
which has 4 subunits
Example: Hemoglobin has four subunits
Protein Function
A protein’s shape is the key to its function
Know at least four functions and an example
Hormones: Insulin helps regulate blood sugar
Enzymes: Catalase catalyzes breakdown of
hydrogen peroxide waste in blood
Transport Proteins: Ion channels and proton
pumps for active transport in cell membrane
Structural Proteins: Collagen, keratin, tubulin,
fibroin
Defense: Antibodies are proteins
Receptors: Hormone receptor or neurotransmitter
receptor on cell surface
MC-3. Which is not a primary
function of protein molecules?
A.
B.
C.
D.
hormones
energy storage
transport
structure
Correct answer: B
MC- 4. Which of the following are
connected by a hydrogen bond?
A.
B.
C.
D.
the hydrogen and oxygen atoms
of a water molecule
base pairs of a DNA molecule
two amino acid molecules of a dipeptide
two glucose molecules in a disaccharide
Answer: B
IB Exam Question
1. Draw a diagram of the molecular
structure of a portion of DNA.
(4 marks)
sugar-phosphate backbone;
bases toward centre;
A—T, G—C base pair;
hydrogen bonds labelled;
twisted ladder;
two polynucleotides (two strands shown);
IB Exam Question
2. To which parts of the deoxyribose molecule
do phosphates bind in DNA?
(1 mark)
A.
B.
C.
D.
I and V
III and V
II and III
III and IV
Correct answer: B
IB Exam Question
3. Which molecules represents ribose?
(1 mark)
Correct answer: D
IB Exam Question
4. Outline how monosaccharides are
converted into polysaccharides.
(2 marks)
condensation;
involves the removal of water to join
monosaccharides together
catalysed by enzymes;
consists of many monosaccharides linked
(glycosidic) to make polysaccharide;
IB Exam Question
5. Describe the use of carbohydrates and
lipids for energy storage in animals.
(5 marks)
Answers must discuss both carbohydrates and lipids to
receive full marks.
carbohydrates:
stored as glycogen (in liver);
short-term energy storage;
more easily digested than lipids so energy can be released
more quickly;
more soluble in water for easier transport;
lipids:
stored as fat in animals;
long-term energy storage;
more energy per gram than carbohydrates;
lipids are insoluble in water less osmotic effect
IB Exam Question
6. Draw the structure of a fatty acid.
(1 mark)
OR
IB Exam Question
7.
Correct answer: D
IB Exam Question
8. Outline the production of a dipeptide by a
condensation reaction. Include the structure of a
generalized dipeptide in your answer. (5 marks)
carboxyl / COOH group of one amino acid reacts with amine /
NH2 group of another;
water / H2O is eliminated;
These steps can be shown
diagrammatically, e.g.
peptide / covalent bond is produced;
diagram of dipeptide, with
peptide bond shown; e.g.
Award [1] if the two amino acids forming the dipeptide are shown correctly.
The radicals can be shown as R or H. Award the second mark if the C-N
bond is labeled as peptide bond or dipeptide bond. The label can include the
H bonded to the N and the O double bonded to the C.
IB Exam Question
9. List four functions of proteins,
giving an example of each.
(4 marks)
Name of function and named protein must both be correct for the
mark.
storage – zeatin (in corn seeds) / casein (in milk);
transport – hemoglobin / lipoproteins (in blood);
hormones – insulin / growth hormone / TSH / FSH / LH;
receptors – hormone receptor / neurotransmitter receptor /
receptor in chemoreceptor cell;
movement – actin / myosin;
defence – antibodies / immunoglobin;
enzymes – catalase / RuBP carboxylase;
structure – collagen / keratin / tubulin / fibroin;
electron carriers – cytochromes;
pigments – opsin
active transport – sodium pumps / calcium pumps;
facilitated diffusion – sodium channels / aquaporins;
IB Exam Question
10. Explain the significance of polar and non-polar
amino acids.
(5 marks)
• Non-polar amino acids have non-polar (neutrally charged) R
groups. \
• Polar amino acids have R chains with polar groups (charged
either positive or negative).
• Proteins with a lot of polar amino acids make the proteins
hydrophyllic and therefore able to dissolve in water.
• Proteins with many non-polar amino acids are more
hydrophobic and are less soluble in water.
• With these abilities, proteins fold themselves so that the
hydrophilic ones are on the inner side and allows hydrophilic
molecules and ions to pass in and out of the cells through the
channels they form.
• These channels are vital passages for many substances in and
out of the cell.
IB Exam Question
11. Outline the difference between fibrous and
globular proteins, with reference to examples of
each protein type.
(4
marks)
• Fibrous proteins are in their secondary structure, which could
be in the alpha helix or beta pleated forms.
• They are made of a repeated sequence of amino acids that can
be coiled tightly around in a pattern that makes it a very strong
structure.
• Two examples are keratin (in hair and skin) and collagen (in
tendons, cartilage, and bones).
• Globular proteins are in their tertiary or quaternary structure,
which is folded, creating a globular, three-dimensional shape.
• An example of globular proteins are all enzymes
IB Exam Question
12. State one function of glucose and glycogen in
animals, and cellulose and starch in plants.
( 4 marks)
• Glucose: Energy for Cellular respiration
• Glycogen: Energy from this polysaccharides is stored in the
liver of animals
• Cellulose: Provides strength to cell walls
• Starch: Energy from this polysaccharide is stored in roots of
plants
IB Exam Question
13. List several examples each of monosaccharides,
disaccharides and polysaccharides
( 6 marks)
• Monosaccharides: Glucose, Fructose (fruit sugar) , Lactose
(milk sugar), Ribose (in RNA)
• Dissacharides:
Sucrose (Glucose and Fructose),
Maltose (Glucose and Glucose)
• Polysacchrides:
Starch (plants) , Glycogen (animals),
and Cellulose (plants)
Chapter Five Quiz
Excellent multiple choice quiz on
Campbell Biology textbook CD or website
Go to Chapter 5: The Structure and Function
of Macromolecules -> Activities Quiz
Use this to study!