proteins Flashcards
(22 cards)
What elements are found in proteins?
Carbon, hydrogen, oxygen, and nitrogen. Sometimes sulfur.
What gives proteins their diverse functions?
Their unique three-dimensional shape.
What happens when proteins are heated?
Weak bonds break, the protein loses its shape, and it becomes denatured.
What are proteins made of?
Polymers of amino acids.
What are amino acids?
Monomers (building blocks) of proteins.
How many naturally occurring amino acids exist?
20
What four groups are bonded to the central carbon in an amino acid?
- Amino group (NH2+), 2. Carboxyl group (COOH-), 3. Hydrogen atom, 4. Variable R group.
What gives different amino acids their properties?
The R group (side chain).
How are polypeptides formed?
By joining amino acids through condensation reactions.
What groups react to form a peptide bond?
The amino group (-NH2) of one amino acid and the carboxyl group (-COOH) of another.
What is released during peptide bond formation?
Water (H2O).
What type of reaction breaks peptide bonds?
Hydrolysis (addition of water).
What types of bonds hold a protein’s three-dimensional structure?
Peptide bonds, disulfide bonds, ionic bonds, hydrogen bonds, and hydrophobic interactions.
What are the main functions of proteins?
- Growth and repair, 2. Enzymes (biological catalysts), 3. Hormones (chemical messengers), 4. Transport proteins, 5. Structural proteins, 6. Antibodies for defense, 7. Energy source during starvation.
Give an example of a transport protein.
Haemoglobin (transports oxygen in red blood cells).
Give an example of a structural protein.
Collagen (skin and bones), Keratin (hair, nails, feathers).
What protein helps defend the body?
Antibodies.
When is protein used as an energy source?
During starvation, after carbohydrates and lipids are used up.
What is kwashiorkor?
A protein deficiency disease causing swollen stomachs, cracked skin, and malnutrition.
What is the test for proteins?
Biuret’s test.
What colour change indicates a positive Biuret’s test?
Violet.
What are the steps for the Biuret’s test?
- Add 2 cm³ of food solution. 2. Add 1 cm³ sodium hydroxide solution. 3. Shake thoroughly. 4. Add 1% copper (II) sulfate solution drop by drop, shaking after each drop. 5. Observe for violet colour change.
