Biological Molecules (proteins)

Question 1

proteins contain:

Answer 1

carbon, hydrogen, oxygen and nitrogen

Question 2

proteins do:

Answer 2

• catalyse reactions as enzymes
• carrier proteins transport molecules across membrane
• antibodies defend against disease
• structural proteins support cells and tissues
• hormones transmit information
• transport proteins
• contractile proteins

Question 3

monomers

Answer 3

amino acids

Question 4

amino acids are made of:

Answer 4

• amino group
• carboxylic acid group
• R-group

Question 5

what is the r-group?

Answer 5

variable side group that determines properties

Question 6

where does the peptide bond form?

Answer 6

between the carboxyl group of one amino acid and the amino group of another

Question 7

what does DNA control?

Answer 7

the sequence and number of amino acids

Question 8

proteins are:

Answer 8

folded polypeptides

Question 9

primary structure:

Answer 9

sequence of amino acids held together by polypeptide bonds between the carboxyl group of one amino acid and the amino group of another in a polypeptide

Question 10

secondary structure:

Answer 10

initial folding of the primary structure into:
- alpha helix
- beta pleated sheet
which are held together by H-bonds between the N-H of one amino acid and the O=H of another

Question 11

tertiary structure:

Answer 11

further folding of the polypeptide chain to give a more complex 3D shape, stabilised by:
- hydrogen bonds between polar R-groups
- disulphide bonds (covalent bonds between sulphurs in cysteine)
- ionic bonds between positive and negative R-groups
- hydrophobic interactions between non-polar R-groups

Question 12

quaternary structure:

Answer 12

more than one polypeptide chain bonded together
- can have prosthetic groups

Question 13

types of protein:

Answer 13

globular and fibrous

Question 14

globular proteins:

Answer 14

• spherical and water soluble
• metabolic role
• hydrophilic outside, hydrophobic inside
• emzymes, channel proteins, tramsport proteins and hormones

Question 15

fibrous proteins:

Answer 15

• insoluble in water
• regular, repetitive amino acid sequence
• keratin, skin, ligaments

Question 16

haemoglobin:

Answer 16

• 3D globular protein for oxygen transport
• four polypeptide chains held together by hydrogen bonds
• two alpha globins and two beta globins
• four prosthetic groups (haem, contain iron)
• compact, spherical and water soluble

Question 17

collagen:

Answer 17

• fibrous protein in skin, hair and ligaments
• three identical left-handed alpha helix polypeptide chains wound around each other in a triple helix
• every third amino acid is glycine
• held by H-bonds and covalent bond crosslinks
• stable, strong and insoluble