Pepitedes and protiens

Question 1

What is the structure of an a amino acid?

Answer 1

An a-amino acid consists of a central carbon atom, called the α carbon, linked to an amino group, a carboxylic acid group, a hydrogen atom, and a R
group.
* R group called a side chain. The side chain is
different for each amino acid.

Question 2

How are amino acids linked together?

Answer 2

• Amino acids are linked together by peptide bonds. * Peptide bond formation is a condensation reaction leading to the polymerization of amino acids into peptides and proteins.

Question 3

What are the properties of peptide bonds?

Answer 3

Peptide bonds are planar , rigid ,flexible . rigidity means chemical hydrolysis require extreme conditions.

Question 4

What are the types of peptides?

Answer 4

• Dipeptide two amino acids.
• Tripeptide three amino acids.
• Polypeptide many amino acids.
• At some point a polypeptide becomes a protein (at 50 joined amino acids).

Question 5

What are proteins?

Answer 5

Are polymers of amino acids linked by peptide bond.

Question 6

What is the primary structure of proteins?

Answer 6

Amino acid residues; Sequence of amino acids in the protein

Question 7

What is the secondary structure of proteins?

Answer 7

There are two very important secondary
structures of proteins, are:
1. α-helix
2. β-pleated sheet
* Both depend on hydrogen bonding

Question 8

What is the tertiary structure of proteins?

Answer 8

Polypeptide chain; * Tertiary structure results from the folding of α
helices and β pleated sheets
* Interactions Involved in Tertiary Structure
1. Hydrophobic/hydrophilic interactions
2. Hydrogen bonding
3. Disulfide linkages

Question 9

What is the quaternary structure of proteins?

Answer 9

Assembled subunits; * Association of more than one polypeptides
* Each unit called subunit
* Subunits (monomers) can be
identical (homopolymeric) or
different (heteropolymeric)
* Interactions Involved are:
* Hydrophobic/hydrophilic
interactions
* Hydrogen bonding

Question 10

How are proteins classified according to shape?

Answer 10

Globular
* Spherical
* Insulin, Hemoglobin,
Enzymes, Antibodies,
Myoglobin

Fibrous
* Long , thin fibers
* Keratin, Elastin, Collagen

Question 11

What is the structure of globular protiens?

Answer 11

Globular proteins are round structures.
Like their name, globular proteins have a
round, spherical formation. This is because the hydrophobic parts of the protein fold inwards while the hydrophilic parts become arranged around the external surface.
* Globular proteins are water soluble. As
only the hydrophilic components of the
protein are on the outer surface, globular
proteins are soluble in water.

Question 12

What is the function of globular proteins?

Answer 12

Due to their round shape and soluble
nature, globular proteins play a wide
variety of vital metabolic roles in the
human body.

Question 13

Which proteins are globular proteins?

Answer 13

enzymes, transport proteins, messenger proteins, hemoglobin.

Question 14

What are enzymes?

Answer 14

All enzymes are globular
proteins as their round shape can be
altered appropriately to fit their target sites with high specificity. Examples include digestive enzymes such
as amylase, pepsin, and lipase which break down starch, protein, and fats respectively

Question 15

What are transport proteins?

Answer 15

Due to their soluble nature, globular proteins function well as transport proteins as they can cross cell
membranes. An example is haemoglobin,
which transports oxygen.

Question 16

What are messenger proteins?

Answer 16

Their solubility also
makes globular proteins suitable as
messenger proteins, otherwise known as
hormones. They regulate the body’s
metabolic processes. An example would
be insulin, which regulates blood sugar
levels.

Question 17

What is haemoglobin?

Answer 17

Haemoglobin is made up of 4 globular subunits. Haemoglobin is a quaternary protein, made up of 4 tertiary globular subunits. Two of these subunits consist
of α chains, while the other two contains β chains.
* Each of these globular subunit is linked to haem. Each globular unit is covalently bonded to haemoglobin. Haem is not a protein, therefore it is called a “prosthetic group”. Haemoglobin contains iron, which oxygen binds to.
As haemoglobin is a protein that is associated with non-
protein structures, it is called a conjugated protein.

Question 18

What is the structure of fibruos proteins?

Answer 18

• Fibrous proteins are long chains. They are made up of repeated amino acid sequences that form long
  polypeptide chains. These chains twist together to form fibrous proteins.
• Fibrous proteins are water insoluble. As the hydrophobic parts of the polypeptide chains are not folded away from the external environment, fibrous
  proteins are not soluble in water.

Question 19

What is the function of fibruous proteins?

Answer 19

Structural proteins are usually fibrous proteins. As fibrous proteins are stable and insoluble structures, they are not suitable to function as metabolic proteins. Rather, they act well as structural proteins
which support and protect tissues.

Question 20

What is collagen?

Answer 20

• Collagen is a strong protein due to the types of bonds in its structure. The proteins in collagen are joined
  together by hydrogen and covalent bonding, both of which are extremely strong and stable bonds.
• Collagen fibres provide support and tensile strength to many structures. Collagen is present in the body as fibres, which consist of many collagen fibrils
  folded around each other. There are many different types of collagen, and they can be found virtually everywhere in the body, including skin, muscles,
  tendons and bones.

Question 21

What is denaturation?

Answer 21

• Is the breakdown of all non-covalent bonds in a
  protein, causing loss of the shape and function.
• But does not alter its primary structure

Question 22

What is denaturation caused by?

Answer 22

• Physical agent (temperature).
• Chemical agent (pH or salt concentration).
• Biological agent (bacteria)

Question 23

What are the functions of proteins?

Answer 23

• Structure and support (collagen).
• Transport (hemoglobin)
• Control and regulation (hormones).
• Protection and Defense (antibodies)
• Most important function is catalysis (Enzymes)