Home › IB Biology › Practice › ProteinsIB Diploma · Biology B1.2
IB Biology B1.2: Proteins — Practice Questions & Answers
IB Biology B1.2 study notes: amino acids and peptide bonds, the levels of protein structure, how sequence determines shape, and the diversity of protein functions.
Here are 10 practice questions with full answers and explanations.
Start an interactive IB Biology quiz →
Practice questions with answers
1
Multiple choice
What is the generalized structure of an amino acid?
Alpha carbon with amine group, carboxyl group, R-group, and hydrogen
Beta carbon with hydroxyl group, phosphate group, R-group, and nitrogen
Gamma carbon with sulfate group, methyl group, R-group, and oxygen
Delta carbon with ketone group, aldehyde group, R-group, and sulfur
Tap an answer to check it.
Why Every amino acid has a central alpha carbon bearing an amine group, carboxyl group, hydrogen, and variable R-group.
2
Multiple choice
What type of reaction forms dipeptides and longer chains of amino acids?
Condensation reaction
Hydrolysis reaction
Oxidation reaction
Reduction reaction
Tap an answer to check it.
Why A condensation reaction joins amino acids into dipeptides and longer chains, releasing water.
3
Multiple choice
What is the product of a condensation reaction between two amino acids?
Dipeptide and water
A disaccharide
Polypeptide and oxygen
A nucleotide
Tap an answer to check it.
Why Condensing two amino acids forms a dipeptide plus a molecule of water.
4
Multiple choice
What are essential amino acids?
Amino acids that cannot be synthesized by the body and must be obtained from food
Amino acids that can be synthesized by the body
Amino acids that are only found in plants
Amino acids that are only found in animals
Tap an answer to check it.
Why Essential amino acids cannot be synthesised by the body and must be supplied in the diet.
5
Multiple choice
What are non-essential amino acids?
Amino acids that can be made from other amino acids by the body
Amino acids that cannot be synthesized by the body
Amino acids that are only found in plants
Amino acids that are only found in animals
Tap an answer to check it.
Why Non-essential amino acids can be synthesised in the body from other amino acids.
6
Multiple choice
What dietary consideration is especially important for vegan diets?
Ensuring intake of all essential amino acids
Avoiding all carbohydrates
Limiting lipid intake
Maximizing vitamin consumption
Tap an answer to check it.
Why Vegan diets must combine plant sources to supply all essential amino acids, which no single plant provides fully.
7
Multiple choice
How many amino acids are coded for in the genetic code?
Tap an answer to check it.
Why The genetic code specifies 20 different amino acids used to build proteins.
8
Multiple choice
What is a characteristic of peptide chains?
They can have any number of amino acids, from a few to thousands
They always have a fixed number of amino acids
They only contain essential amino acids
They only contain non-essential amino acids
Tap an answer to check it.
Why Peptide chains vary widely in length, from a few amino acids to thousands.
9
Multiple choice
What is the term for the loss of a protein's three-dimensional structure?
Denaturation
Anabolism
Hydrolysis
Condensation
Tap an answer to check it.
Why Denaturation is the loss of a protein's three-dimensional structure and hence its function.
10
Multiple choice
What factors can cause protein denaturation?
pH and temperature
Substrate concentration
Addition of water molecules
Competitive inhibitors
Tap an answer to check it.
Why Extremes of pH and temperature break the bonds holding a protein's shape, causing denaturation.
Key terms in Proteins
Amino acid: The monomer of proteins, with an amine group, a carboxyl group, a hydrogen and a variable R group around a central carbon.
R group (side chain): The variable part of an amino acid that differs between the twenty types and determines how the protein folds.
Peptide bond: The covalent bond formed by condensation between the carboxyl group of one amino acid and the amine group of another.
Polypeptide: A chain of amino acids joined by peptide bonds.
Primary structure: The specific sequence of amino acids in a polypeptide, determined by the gene.
Tertiary structure: The overall three-dimensional shape of a polypeptide, stabilised by interactions between R groups.
Quaternary structure: The arrangement of two or more polypeptide subunits in a protein, as in haemoglobin.
Denaturation: The loss of a protein’s three-dimensional shape, and therefore its function, caused by heat or extremes of pH.
See the full study notes for this topic.
Practise other IB Biology topics