IB DP Biology D1.2 Protein synthesis-FA 2025- IB Style Questions For SL Paper 2

(a) 

• Proteins are made up of building blocks called amino acids.
• There are about 20 different amino acids used in making proteins.
• The amino acids are joined together by peptide bonds to form chains called polypeptides.
• A protein might be made of one or more polypeptide chains.
• These chains fold into a specific 3D shape, and that shape is what gives the protein its job or function.

(b)

• A gene in the DNA gives the instructions to make a protein – it’s like a recipe.
• When a gene is “turned on,” it goes through a process called transcription, where the DNA is copied into mRNA.
• The mRNA leaves the nucleus and goes to a ribosome, which is the protein-making machine.
• At the ribosome, translation happens: the mRNA code is read in groups of three bases (called codons), and each codon tells the ribosome which amino acid to add.
• tRNA molecules bring the correct amino acids to the ribosome.
• The amino acids are linked together in the right order to form a polypeptide.
• The sequence of amino acids depends on the order of bases in the DNA, and since each gene has a different sequence, it makes a different protein.

• Also, mutations (small changes in DNA) can change the protein, adding even more variety.

(c)

• Enzymes – speed up chemical reactions, like breaking down food or building molecules.
• Hormones – some proteins like insulin act as messengers between cells.
• Transport proteins – help move things across cell membranes (like glucose or ions).
• Hemoglobin – a protein in red blood cells that carries oxygen around the body.
• Receptors and cell markers – found on cell membranes, they help cells communicate and recognize each other.
• Structural proteins – like actin and myosin in muscles that help with movement, or proteins that form spindle fibers during cell division.

• Histones – help organize and pack DNA tightly into chromosomes.

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