1.1

• What are the two main types of proteins mentioned in the study material?

  Globular and fibrous proteins
• How do fibrous proteins differ from globular proteins in terms of solubility?


  Fibrous proteins are insoluble in water, while globular proteins are soluble
• What structural feature of fibrous proteins contributes to their strength and toughness?


  The presence of many cross-linkages forming long fibers
• What is keratin, and where is it found?

  Keratin is a fibrous protein found in hair
• What is the composition of a single collagen fiber?


  A single collagen fiber consists of three identical polypeptide chains twisted around each other
• What type of bonds link the polypeptide chains in collagen?


  Hydrogen bonds
• What is the primary function of globular proteins?


  Globular proteins have many different functions, including enzymes and hormones
• What is haemoglobin, and how many polypeptide chains does it consist of?


  Haemoglobin is a globular protein consisting of four folded polypeptide chains
• What is the biuret test used for?


  The biuret test is used to test for the presence of proteins
• What color change indicates a positive result in the biuret test?


  The color change from blue to purple indicates a positive result
• What happens to the color of the biuret test at low protein concentrations?


  The color change is difficult to detect by eye at low protein concentrations
• How can the biuret test be used semi-quantitatively?


  By comparing the intensity of purple in two identically treated solutions
• What is the purpose of using a colorimeter in the biuret test?


  To measure the absorbance of the purple biuret for estimating protein concentration
• What wavelength filter is used in the colorimeter for the biuret test?


  A yellow filter at 580 nm is used
• What is required to measure the actual concentration of proteins quantitatively?


  A biosensor is needed to measure the actual concentration
• What are the roles of proteins based on their molecular shape?

  • Fibrous proteins: structural functions (e.g., in bone)
  • Globular proteins: diverse functions (e.g., enzymes, antibodies, hormones)
• Match the polysaccharide with their components.

  1. Glycogen - Glucose
  2. Phospholipid - Glycerol, fatty acid, phosphate
  3. Haemoglobin - Amino acids
  4. Cellulose - β-glucose
• What is the structure of the polypeptides in fibrous proteins?


  Polypeptides are in parallel chains or sheets
• What is the significance of the iron-containing group in haemoglobin?


  The iron-containing group, haem, is essential for oxygen transport
• How does the structure of collagen contribute to its function in tendons?


  The twisted structure of collagen provides strength and toughness needed in tendons
• What is the basic unit that forms polypeptide chains in proteins?

  Amino acids
• What type of bond joins amino acids in a polypeptide chain?

  Peptide bonds
• What is the primary structure of a protein?


  The sequence of amino acids in a polypeptide chain
• How can a change in the sequence of amino acids affect a protein?


  It can alter the protein's properties
• What is a condensation reaction in the context of protein formation?


  It involves the removal of a water molecule to form a peptide bond
• What stabilizes the α-helix secondary structure of proteins?


  Hydrogen bonds between the -CO and -NH groups
• What is the β-pleated sheet in protein structure?


  A less common secondary structure that is sheet-like and stabilized by hydrogen bonds
• What determines the tertiary structure of a protein?


  The interactions between different R groups of the amino acids
• What is the quaternary structure of a protein?


  A complex structure formed by more than one polypeptide chain
• What are fibrous proteins characterized by?


  Long, thin molecules that are insoluble in water
• Give an example of a fibrous protein.


  Keratin
• What is a characteristic of globular proteins?


  They are usually spherical and soluble in water
• What is the test for protein?

  Add copper (II) sulphate and sodium hydroxide
• What does the biuret test indicate?


  The presence of peptide bonds in a protein
• What happens to the color intensity in the biuret test with increasing protein concentration?


  The intensity of the purple color increases
• What is a dipeptide?


  A compound formed from two amino acids joined by a peptide bond
• What is the significance of the R group in amino acids?


  It determines the unique properties of each amino acid
• What is a zwitterion?


  An amino acid that has both a positive and a negative charge at pH 7
• What is the process of atherosclerosis?


  It involves the deposition of atheroma in the arteries, restricting blood flow
• What are triglycerides primarily used for?


  Energy reserves