Question
The diagrams show monomers formed by the digestion of macromolecules in the small intestine.
Which monomers could result from the digestion of an unsaturated fat?
A. 1, 2 and 4 only
B. 1 and 3 only
C. 4 and 5 only
D. 3, 4 and 5 only
▶️Answer/Explanation
Answer: D. 3, 4 and 5 only
Explanation:
What are unsaturated fats?
- They’re a type of lipid.
- Made of glycerol + fatty acids.
- Unsaturated fatty acids have at least one C=C double bond in their carbon chain.
Step-by-step breakdown of each monomer:
Monomer 1
- Structure: One carbon chain with a carboxyl group and LOTS of OH groups.
- That’s glucose, a carbohydrate.
- Not from fat digestion
Monomer 2
- Structure: Has NH₂ (amino) + COOH (carboxyl) = classic amino acid.
- That’s glycine, an amino acid from protein digestion.
- Not from fat digestion
Monomer 3
- Structure: 3-carbon backbone, each carbon with OH groups.
- That’s glycerol, the backbone of triglycerides (fats).
- YES! From fat digestion
Monomer 4
- Structure: Long hydrocarbon chain with a COOH group AND a double bond (C=C).
- That’s an unsaturated fatty acid.
- YES! From unsaturated fat
Monomer 5
- Structure: Long hydrocarbon chain with COOH group but no double bonds = saturated fatty acid.
- Still released when fats are digested (many fats contain both types).
Question
The diagram shows two molecules which can be linked by a condensation reaction
What would be the product(s) of this reaction?
A. Water and sucrose
B. Water and maltose
C. A dipeptide
D. Lactose
▶️Answer/Explanation
Answer: A. Water and sucrose
Explanation:
1. Identify the sugars:
- The left molecule is glucose (a 6-carbon sugar).
- The right molecule is fructose (also a 6-carbon sugar, but with a 5-membered ring).
2. What is a condensation reaction?
- A condensation reaction is when two molecules join together.
- During this process, one water molecule (H₂O) is removed.
- One –OH group from one sugar and an –H from the other are removed to form water.
3. What do glucose and fructose make when they join?
- When glucose and fructose join by a condensation reaction, they form a disaccharide called sucrose.
- At the same time, water (H₂O) is produced.
4. Final reaction: Glucose + Fructose → Sucrose + Water
Why not the other options?
B. Maltose – comes from glucose + glucose, not glucose + fructose.
C. Dipeptide – made from amino acids, not sugars.
D. Lactose – comes from glucose + galactose, not fructose.
Question
Lipids are more efficient energy stores than carbohydrates. What is a reason for this?
A. Lipids are bigger molecules than carbohydrates.
B. Lipids release more energy per gram than carbohydrates.
C. Lipids can be more easily mobilized than carbohydrates when needed.
D. Lipids can be used in aerobic and anaerobic respiration when needed.
Answer/Explanation
Answer: B. Lipids release more energy per gram than carbohydrates.
Explanation:
Lipids are more efficient energy stores because:
- They contain more carbon-hydrogen (C–H) bonds than carbohydrates.
- These bonds release more energy when broken during aerobic respiration.
- As a result, 1 gram of lipid provides more than twice the energy of 1 gram of carbohydrate.
That means the body can store more energy in less space using lipids — making them ideal for long-term energy storage, especially in animals.
Why the other options are wrong:
A. Lipids are bigger molecules than carbohydrates → Size doesn’t directly relate to how much energy they release per gram.
C. Lipids can be more easily mobilized than carbohydrates → Incorrect. Carbohydrates are actually faster to break down and mobilize for quick energy, which is why the body uses glucose first.
D. Lipids can be used in aerobic and anaerobic respiration → False. Lipids can only be used in aerobic respiration. Anaerobic respiration uses only glucose (carbohydrates), not fats.
Question
The table shows the range and classification of body mass index (BMI) values, as shown in the nomogram.
BMI value | Less than 18.5 | 18.5 to 24.9 | 25.0 to 29.9 | 30.0 or more |
Classification | underweight | normal weight | overweight | obese |
What is the approximate reduction in body mass that a person of height 155 cm and mass 95 kg
would have to lose to reach normal body mass?
10 kg
22 kg
36 kg
54 kg
▶️Answer/Explanation
Answer: C. 36 kg
Explanation:
Given:
- Height = 155 cm
- Weight = 95 kg
- Goal: Reach “normal weight” BMI, i.e. between 18.5 to 24.9
Step 1: Locating the point (155 cm, 95 kg) on the chart
Using the BMI chart:
- A person who is 155 cm tall and weighs 95 kg falls in the BMI = 40 zone.
- This is clearly in the “obese” category (BMI ≥ 30).
Step 2: Target the upper limit of “normal weight” for 155 cm
From the graph:
A person who is 155 cm and has a BMI of 24.9 (top end of normal weight range) weighs approximately 59 kg.
Step 3: Calculate the required weight loss
- Starting weight = 95 kg
- Target weight = 59 kg
- Weight to lose = 95 − 59 = 36 kg
Question
The diagram shows the product of a polymerization reaction.
What is formed in this polymerization reaction?
A. A dipeptide formed by the hydrolysis of two nucleotides
B. A tripeptide formed by the hydrolysis of three amino acids
C. A dipeptide formed by the condensation of two amino acids
D. A tripeptide formed by the condensation of three amino acids
▶️Answer/Explanation
Answer: D. A tripeptide formed by the condensation of three amino acids
Explanation:
What do we see in the structure?
This is a peptide chain a molecule made from amino acids joined together.
- There are three amino acid units visible in the chain.
- Each amino acid is connected by a peptide bond (—CO—NH—), which is formed by condensation (removal of water).
- The ends of the chain still show a free amine group (-NH₂) and a free carboxylic acid group (-COOH) — just like in peptides!
So, what is happening here?
This structure is:
- A tripeptide (3 amino acids),
- Formed by condensation reactions (not hydrolysis!),
- Linking the amino group of one amino acid to the carboxylic acid of another.
Let’s eliminate wrong options:
A. Hydrolysis is incorrect — this is condensation, not breaking.
B. Again mentions hydrolysis — not correct.
C. It’s a tripeptide, not just a dipeptide.
D. Perfect! It matches everything:
✔ Tripeptide
✔ Formed by condensation
✔ Made from 3 amino acids
Question
What is a consequence of the ability of water to form many intermolecular hydrogen bonds?
A. Ice has a higher density than water and floats, providing habitats for fish-eating mammals.
B. Light can pass through water, so algae can photosynthesis.
C. Some small invertebrates can walk on water surfaces.
D. Small amounts of energy are needed to change water from one state to another, so that evaporation rates and condensation rates are rapid.
▶️Answer/Explanation
Answer: C. Some small invertebrates can walk on water surfaces.
Explanation:
Water molecules can form hydrogen bonds with each other this gives water several special physical properties, like:
- High surface tension
- High specific heat capacity
- High boiling and melting points
- Ice being less dense than liquid water
Now let’s evaluate each option:
A. Incorrect – this is scientifically wrong.
Ice actually has a lower density than water, which is why it floats.
This does result from hydrogen bonding, but the statement says higher density, so it’s wrong.
B. This is due to water’s transparency, not its hydrogen bonds.
So, this is not related to the question.
C. Correct
Because of hydrogen bonding, water has high surface tension.
This allows insects like pond skaters to walk on water.
D. Wrong – water actually needs a lot of energy to change state because hydrogen bonds must be broken.
So, this is the opposite of what’s true.
Question
Which reaction occurs when a dipeptide is formed from amino acids?
A. Hydrolysis
B. Condensation
C. Transcription
D. Oxidation
▶️Answer/Explanation
Answer: B. Condensation
Explanation:
When two amino acids join together to form a dipeptide, something important happens:
What actually happens?
- The amino group (-NH₂) of one amino acid reacts with the carboxyl group (-COOH) of another.
- A water molecule (H₂O) is removed in the process.
- This forms a peptide bond between the two amino acids.
This type of reaction is called a: Condensation reaction – Because water is removed to join two molecules together.
Let’s eliminate the wrong options:
A. Hydrolysis = opposite of condensation (adds water to break a bond)
C. Transcription = copying DNA into RNA (nothing to do with peptides)
D. Oxidation = involves electron loss or gain, not peptide formation
Question
What type of molecule is formed by the chemical reaction shown in the diagram?
A. Dipeptide
B. Disaccharide
C. Diglyceride
D. Cellulose
▶️Answer/Explanation
Answer: B. Disaccharide
Explanation:
STEP-BY-STEP ANALYSIS OF THE DIAGRAM:
- The image shows two hexose sugar rings (specifically glucose molecules) reacting.
- Each glucose ring has -OH (hydroxyl) groups.
- In the reaction, a glycosidic bond forms between the two glucose units.
- This bond is formed by removing a molecule of water (H₂O) a condensation (dehydration synthesis) reaction.
- The resulting compound is two glucose molecules linked together via an α-1,4-glycosidic bond.
IDENTIFYING THE PRODUCT:
- The product is maltose, which is a disaccharide.
- A disaccharide is made when two monosaccharides are joined by a glycosidic linkage, with the elimination of a water molecule.
EXPLANATION OF OPTIONS:
A. Dipeptide
- Made from two amino acids (not sugars).
- Linked by a peptide bond.
- Not related to the diagram.
B. Disaccharide
- Made from two monosaccharides (like glucose).
- Linked by a glycosidic bond.
- Formed by condensation reaction, producing H₂O.
- Correct match to what’s shown in the diagram.
C. Diglyceride
- Formed from glycerol + 2 fatty acids.
- Found in lipids, not carbohydrates.
- Not relevant here.
D. Cellulose
- A polysaccharide made of hundreds to thousands of glucose units.
- The image only shows two glucose units.
- Not cellulose.
Question
The diagram shows two polysaccharides, formed from condensation of many glucose molecules.
What are the names of X and Y?
▶️Answer/Explanation
Answer: A
Explanation:
Observation of Structures:
- X shows a highly branched structure
- Y shows a coiled/spiral helix structure
Structure Identification:
Structure X – Highly branched
- Could be either amylopectin or glycogen.
- But based on the image, X is very branched much more than amylopectin typically is.
- This level of dense branching is characteristic of glycogen, not amylopectin.
Structure Y – coiled/spiral helix
This is clearly amylose, the unbranched component of starch that coils into a helix.
FINAL CORRECT MATCH:
- X = Glycogen
- Y = Amylose
Question
The diagrams show how monosaccharide molecules are joined to form chains in two polysaccharides.
▶️Answer/Explanation
Answer: C
Explanation:
Let’s Analyze the Diagrams:
Diagram P:
- Shows parallel, linear chains.
- Each chain is unbranched, and the chains are aligned this indicates cellulose.
- Cellulose is made of β-glucose, but still, the monomer is glucose.
- However, it is not branched so not glycogen or amylopectin.
Diagram Q:
- Shows a highly branched structure.
- This is characteristic of glycogen (in animals) or amylopectin (in plants).
- Both are polysaccharides of α-glucose.
So,
- P = Cellulose
- Q = Glycogen or Amylopectin
- Both are made from glucose (NOT maltose!)
Question
What distinguishes cellulose from glycogen and starch?
A. Only cellulose is found in plants.
B. Only cellulose is made up of glucose monomers.
C. Cellulose is far more branched than starch and glycogen.
D. Cellulose has a structural role whereas starch and glycogen function in energy storage.
▶️Answer/Explanation
Answer: D. Cellulose has a structural role whereas starch and glycogen function in energy storage.
Explanation:
| Polysaccharide | Found in | Monomer | Function | Structure |
|---|---|---|---|---|
| Cellulose | Plants | β-glucose | Structural (cell wall) | Unbranched, linear |
| Starch | Plants | α-glucose | Energy storage | Amylose (unbranched), Amylopectin (branched) |
| Glycogen | Animals | α-glucose | Energy storage | Highly branched |
Evaluate Each Option:
A. Incorrect — starch is also found in plants (as energy storage).
B. Incorrect — all three (cellulose, starch, glycogen) are made from glucose monomers.
C. Incorrect — cellulose is NOT branched at all; it is linear. Glycogen is actually the most branched.
D. Correct! This is the fundamental distinction:
- Cellulose = structural (in plant cell walls).
- Starch & glycogen = energy storage (plants & animals, respectively).
Question
Which drawing represents beta-D-glucose?
▶️Answer/Explanation
Answer: B
Explanation:
Step-by-step Explanation:
1. Understanding the Question:
We’re looking for β-D-glucose in its Haworth (cyclic) form. This is a six-membered ring (called pyranose) formed when the linear D-glucose reacts with itself to create a ring.
2. Structure of D-Glucose (Pyranose Form):
D-glucose forms a six-membered ring with:
- Carbon 1 (C1): The anomeric carbon (where ring formation happens).
- Carbon 5 (C5): Has the CH₂OH group.
Depending on the position of the -OH group on C1, we get:
- α-D-glucose: OH on C1 is opposite side of CH₂OH (i.e., OH down, CH₂OH up).
- β-D-glucose: OH on C1 is same side as CH₂OH (i.e., both up).
3. Identifying β-D-glucose:
So, in the correct structure of β-D-glucose, we expect:
| Carbon | Substituent | Orientation |
|---|---|---|
| C1 | OH | Up |
| C5 | CH₂OH | Up |
Let’s check each option:
- OH on C1 → Up
- CH₂OH on C5 → Up
- Ring is six-membered (pyranose)
This matches β-D-glucose
Option B:
- Two CH₂OH groups → Invalid (glucose has one CH₂OH group)
- So not glucose at all.
Option C:
- OH on C1 → Down
- CH₂OH on C5 → Up
→ Opposite sides → This is α-D-glucose
Option D:
- Also shows two CH₂OH groups → Not D-glucose