Summary
Polymers of amino acids that act as enzymes, structural parts, transporters, hormones and antibodies.
In depth
Protein functions include catalysis (enzymes), structure (collagen, keratin), transport (haemoglobin), defence (antibodies), movement (actin, myosin), signalling (insulin) and storage. The sequence of amino acids codes a specific three-dimensional shape that fits its function.
Humans make tens of thousands of different proteins from just 20 amino acids, and changing one amino acid can change function entirely.
Proteins make up about 15 to 20 percent of body mass. A typical cell has thousands of different proteins, and the human genome encodes about 20,000 genes that produce many more protein forms by alternative splicing and modification. Fibrous proteins (collagen, keratin) are long and structural, while globular proteins (enzymes, haemoglobin) are compact and soluble.
Nutrition: of the 20 amino acids, nine are essential for adults and must be eaten; complete proteins in meat, eggs and soy supply all of them, and grains and pulses combine to cover the gaps. Biuret reagent turns purple in the presence of peptide bonds, which is the standard lab test.
Key idea: structure determines function, so any change in shape alters activity.
Frequently asked questions
What is Proteins?
Polymers of amino acids that act as enzymes, structural parts, transporters, hormones and antibodies.
Which area of biology covers Proteins, and how advanced is it?
Proteins is one of the 51 topics in Biomolecules & Biochemistry. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Primary Structure, Tertiary Structure, Macromolecules.
Can you give an example of Proteins?
Sickle cell disease results from a single amino acid change in beta-globin.
What should I learn before Proteins?
Proteins is a Beginner topic, so no earlier topic is required. Other Beginner topics in Biomolecules & Biochemistry that pair well with it include Water Properties, Carbon Chemistry, Carbohydrates.
What topics are related to Proteins?
The closest topics to Proteins are Primary Structure, Tertiary Structure, Macromolecules, ATP Structure and Function. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Proteins?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Proteins. To practise the whole of Biomolecules & Biochemistry, use the Biomolecules & Biochemistry quiz.
How is Proteins different from Primary Structure?
Proteins: Polymers of amino acids that act as enzymes, structural parts, transporters, hormones and antibodies. Primary Structure: The linear order of amino acids in a polypeptide, which determines all higher levels of folding. Read both side by side and note what each one explains.
How should I study Proteins step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Primary Structure and explain the difference aloud. Finally, take the Biomolecules & Biochemistry quiz and come back to this page for any question you miss.