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IB DP Biology- B1.2 Proteins IB Style Questions For HL Paper 1-New Syllabus

IBDP Biology HL Paper 1 -All Chapters

Question

The table shows some essential and non-essential amino acids. What is a valid conclusion?

Essential amino acidsNon-essential amino acids
ValineAlanine
LysineGlycine
(A) Lysine is synthesized by the human body.
(B) Alanine can only be obtained from food.
(C) Glycine is not used in the human body.
(D) Valine must be supplied in the diet.
▶️ Answer/Explanation

Correct Answer: \( \boxed{\mathbf{D}} \)

Essential amino acids cannot be synthesized by the human body and therefore must be obtained from the diet. Since valine is an essential amino acid, it must be supplied through food, whereas non-essential amino acids such as alanine and glycine can be synthesized by the body.

Question

Which row correctly matches the level of structure of a protein molecule with the bonds that stabilize it?

OptionLevel of StructureBonds
Aprimarypeptide and hydrogen bonds between amine and carboxyl groups
Bsecondaryhydrogen bonds between R-groups of amino acids
Ctertiarydisulfide, hydrogen and ionic bonds between R-groups of amino acids
Dquaternarycovalent bonds between hydrophobic and hydrophilic regions on the polypeptide subunits
▶️ Answer/Explanation
The tertiary structure of a protein is stabilized by interactions between the R-groups (side chains) of amino acids. These include disulfide bridges (covalent), hydrogen bonds, ionic interactions, and hydrophobic forces, which give the protein its three-dimensional conformation.
✅ Answer: (C)
Question

Which of the following elements are constituents of proteins?

I. Carbon

II. Nitrogen

III. Oxygen

A. I only

B. I and II only

C. I and III only

D. I, II and III

▶️ Answer/Explanation
Solution
Proteins are organic macromolecules that contain several key elements.
The primary elements include Carbon (C), Nitrogen (N), and Oxygen (O).
Thus, all three elements (I, II, and III) are constituents of proteins.
✅ Answer: D. I, II and III
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