proteins

Question 1

Define the monomers of proteins

Answer 1

Amino acids are the monomers of proteins.

Question 2

What is a dipeptide and how is it formed?

Answer 2

A dipeptide is two amino acids joined together.

Question 3

What is a polypeptide?

Answer 3

A polypeptide is more than two amino acids joined.

Question 4

What are proteins made of?

Answer 4

Proteins are made of one or more polypeptides.

Question 5

State the four components of a general amino acid.

Answer 5

All amino acids have:

A carboxyl group (-COOH)

An amine/amino group (-NH₂)

A variable R group (side group)

A hydrogen atom

Question 6

What is the general structure of an amino acid?

Answer 6

H₂N–C(R)H–COOH

Question 7

What makes each amino acid different?

Answer 7

The only difference between amino acids is the R group.

Question 8

How many amino acids are used in living organisms?

Answer 8

20 amino acids are used in living organisms.

Question 9

What is unique about the R group in glycine?

Answer 9

Glycine is the only one with an R group that is a hydrogen atom.

Question 10

Describe what occurs during a condensation reaction between two amino acids.

Answer 10

A condensation reaction joins amino acids together and forms peptide bonds and releases a molecule of water.

Question 11

Describe how a peptide bond is broken.

Answer 11

Hydrolysis breaks peptide bonds; reverse of condensation.

Question 12

What is the primary structure of a protein?

Answer 12

The primary structure is the sequence of amino acids in a polypeptide.

Question 13

What bonds are involved in the primary structure?

Answer 13

Peptide bonds.

Question 14

Why is primary structure important?

Answer 14

Primary structure is important as it determines overall structure/function. A single amino acid change can affect protein function.

Question 15

What causes secondary structure formation?

Answer 15

A secondary structure forms when Hydrogen bonds form between amino acids.

Question 16

What shapes result from secondary structure of proteins?

Answer 16

Secondary structure of proteins form the shape Alpha helix (α-helix) and beta-pleated sheet (β-sheet).

Question 17

What happens in tertiary protein structure?.

Answer 17

In a tertiary protein structure Further folding into a 3D shape occurs

Question 18

Name the bonds involved in tertiary structure.

Answer 18

Hydrogen bonds, ionic bonds (between charged R groups), disulfide bridges (between two cysteines), and hydrophobic/hydrophilic interactions (between polar/non-polar R groups).

Question 19

What does the tertiary structure determine?

Answer 19

Tertiary structure Determines specific function. For single-chain proteins, this is the final structure.

Question 20

What defines quaternary protein structure?

Answer 20

quaternary protein structure Applies to proteins with more than one polypeptide chain. Structure refers to how the chains are assembled.

Question 21

What bonds are involved in quaternary structure?

Answer 21

Chains held together by same bonds as tertiary structure.

Question 22

What additional components may quaternary proteins include?

Answer 22

Quaternary proteins May include prosthetic groups (non-protein components).

Question 23

Give examples of proteins with quaternary structure.

Answer 23

Haemoglobin, insulin, collagen. Have a quaternary structure

Question 24

Do all proteins have quaternary structure?

Answer 24

Not all proteins have this level (e.g., myoglobin does not).

Question 25

Describe the structure and roles of enzymes.

Answer 25

Enzymes have a spherical shape due to tight folding. They are soluble. Roles in metabolism: Break down large molecules (digestive enzymes). Synthesis of large molecules.

Question 26

Describe the structure of antibodies and their function.

Answer 26

• Antibodies are proteins made of four polypeptide chains: two long (heavy) chains and two short (light) chains. They have variable regions that form antigen-binding sites. • The shape of the variable region is complementary to a specific antigen, allowing binding. Function of antibodies: • Antibodies are involved in the immune response. • They bind to antigens on the surface of pathogens to help neutralise or destroy them.

Question 27

Describe the structure and function of transport proteins.

Answer 27

Transport proteins are Found in cell membranes (e.g., channel proteins). They Contain hydrophobic and hydrophilic amino acids folded into channels. and its Function is to: Transport molecules and ions across membranes.

Question 28

Describe structural proteins and give examples.

Answer 28

structural proteins are Physically strong and have Long polypeptide chains parallel with cross-links. Examples: Keratin (hair and nails) Collagen (connective tissue) Collagen has three polypeptide chains tightly coiled to increase strength for supportive function in animals.

Question 29

Name two more functions of proteins.

Answer 29

Proteins are responsible for Hormones: Some are proteins (e.g., insulin); act as chemical messengers. Muscle contraction: Proteins like actin and myosin are involved in muscle movement.

Question 30

How do you test for proteins using the Biuret test?

Answer 30

Procedure: Make solution alkaline: Add a few drops of sodium hydroxide. Add copper(II) sulfate solution.

Question 31

What is a positive and negative result in the Biuret test?

Answer 31

Positive: there is a colour change from blue to Purple colour if protein is present. Negative: the solution Stays blue → no protein. Colours are pale, observe carefully.

Question 32

Match each protein structure level with its bonds.

Answer 32

Primary proteins - are made of Amino acid sequence joined via Peptide bonds Secondary proteins are made of α-helix / β-sheet linked via Hydrogen bonds Tertiary proteins have a 3D folded structure with Hydrogen, ionic, disulfide, hydrophobic interactions Quaternary proteins are made of Multiple polypeptides and prosthetic groups linked together by Hydrogen, ionic, disulfide, and hydrophobic interactions