Chapter 3- Biological molecules

Question 1

what bond is formed between amino acids?

Answer 1

peptide bonds

Question 2

How do the interactions between the R groups of amino acids contribute to the folding of polypeptides into proteins?

Answer 2

-the R groups of amino acids making up a protein are able to interact with each other forming different types of bonds.
- these bonds lead to polypeptides (long chain of amino acids) folding into proteins.

Question 3

what is the structure of an amino acid?

Answer 3

• Amine group (-NH₂) = consisting of a nitrogen atom bonded to two hydrogen atom
• Carboxyl group (-COOH)= consisting of C=O and a hydroxyl group (-OH)
• A single hydrogen atom is bonded to the central carbon
  -. R Group
• Central Carbon Atom

Question 4

draw the structure of an amino acid

Answer 4

H H
| |
N— C—C=O—OH
| |
H R

Question 6

what are the levels of protein structure?

Answer 6

• primary structure
• secondary structure
• tertiary structure
• quaternary structure

Question 7

Describe the primary structure in the levels of protein structure.

Answer 7

• The primary structure of a protein refers to the sequence of amino acids in a polypeptide chain.
• The order of amino acids is determined by the genetic code (DNA sequence) and is held together by peptide bonds.
• The primary structure is important because it dictates the protein’s final shape and function.
• only bonds involved are peptide bonds

Question 8

Describe the secondary structure in the levels of protein structure.

Answer 8

• The secondary structure refers to the folding of the polypeptide chain into structures such as alpha helices or beta-pleated sheets.
• The oxygen, hydrogen and nitrogen atoms of the amino acids interact.
• Alpha helices are coiled structures
• while beta-pleated sheets are made of parallel strands of polypeptides that are folded.
• secondary structure is the result of hydrogen bonds

Question 9

Describe the tertiary structure in the levels of protein structure.

Answer 9

• The tertiary structure refers to the overall 3D shape of a single polypeptide chain.
• It is stabilized by a variety of bonds and interactions between the R groups (side chains) of the amino acids, including:
  Hydrogen bonds
  Ionic bonds
  Disulphide bridges (covalent bonds between sulfur atoms)
  Hydrophobic/ hydrophillic interactions ( weak interactions between polar and non-polar R groups)
• The tertiary structure is critical for the protein’s function

Question 10

Describe the quaternary structure in the levels of protein structure.

Answer 10

• refers to the arrangement of multiple polypeptide chains (subunits) into a functional protein.
• Not all proteins have quaternary structure, but those that do are composed of two or more polypeptide chains. These subunits can be identical or different.
• Quaternary structure is held together by the same types of bonds that stabilize tertiary structure (hydrogen bonds, ionic bonds, hydrophobic interactions, and disulphide bridges).
• Example: Haemoglobin, a protein made of four polypeptide chains, has a quaternary structure.

Question 11

what enzymes break down peptides into amino acids, and what role does water play in this process?

Answer 11

• protease are enzymes that turn peptides back into amino acids.
• a water molecule is used to break the bond through hydrolysis

Question 12

list features of a globular protein

Answer 12

• compact
• water soluble
• 3D spherical shape
• e.g. insulin

Question 13

list features of a fibrous protein

Answer 13

• strong
• long/straight
• insoluble
• sometimes flexible
• e.g. collagen, elastin and keratin

Question 14

what is a conjugated protein?

Answer 14

• globular proteins that contain a (non- protein) prosthetic group.
• The prosthetic group is often a metal ion, vitamin, or carbohydrate
• e.g. haemoglobin

Question 15

what are proteins without prosthetic groups called?

Answer 15

simple proteins

Question 16

what are fatty acid chains with no double bonds present called?

Answer 16

fatty acid chains that have no double bonds present between the carbon atoms are called saturated, because all the carbon atoms form the maximum number of bonds with hydrogen atoms

Question 17

what are fatty acid chains with double bonds present called?

Answer 17

a fatty acid with double bonds between some of the carbon atoms is called unsaturated. the presence of double bonds cause the molecules to kink or bend and they therefore cannot pack closley together.

Question 18

what are triglycerides made up of?

Answer 18

1 glycerol bonded (ester bond) to 3 fatty acids

Question 19

what are phospholipids made up of?

Answer 19

2 fatty acids, 1 glycerol and 1 phosphate

Question 20

roles of lipids

Answer 20

due to their non polar nature, lipids have many biological roles including:
- hormone production
- electrical insulation necessary for impulse transmission
- membrane formation and the creation of hydrophobic barriers
- water proofing.
also have an important role in long term storage.

Question 21

what roles do lipids have in long term storage?

Answer 21

triglycerides in particular have an important role in long term energy storage. for example:
- thermal insulation to reduce heat loss
- cushioning to protect vital organs
- buoyancy for aquatic organisms

Question 22

what are organic compounds?

Answer 22

• molecules that contain the chemical elements carbon (C) and hydrogen (H
• examples are: Carbohydrates, lipids, proteins and nucleic acids

Question 23

what are the 3 types of carbohydrates?

Answer 23

monosaccharides, disaccharides and polysaccharides

Question 24

what functions do carbohydrates have?

Answer 24

• Source of energy e.g. glucose is used for energy-release during cellular respiration
• Store of energy e.g. glycogen is stored in the muscles and liver of animals
• Structurally important e.g. cellulose in the cell walls of plants

Question 25

what is adhesion?

Answer 25

the attraction of water molecules to the impermeable walls of xylem tissue