Proteins

Question 0

Proteins are made from (6)

Answer 0

• Carbon, hydrogen, oxygen, nitrogen and occasionally sulfur
• Polypeptides that make up the protein are synthesised on the ribosome while they are assembled into proteins when released int o the cytoplasm

Question 1

Functions of proteins (5)

Answer 1

• They are structural components
• They are membrane carriers and pores
• All enzymes are proteins
• Many hormones are proteins
• Antibodies are proteins

Question 2

Excess amino acids in mammals (3)

Answer 2

• Too many amino acids can be toxic
• The process of removing the amino group is called deamination
• Amino acids are converted to urea and excreted as piss

Question 3

Amino acids (4)

Answer 3

• All amino acids have the same structure with a carboxyl group at one end an an amino group at the other end
• The R-group determines the amino acid
• R-groups can be negatively or positively charged while others are hydrophobic or hydrophilic
• The monomeric unit for a protein

Question 4

Condensation reaction

Answer 4

When the amino group of one amino acid bonds with the carboxyl group of another forming a peptide bond while losing a water molecule

Question 5

Hydrolysis

Answer 5

The splitting of a bond with the use of a water molecule

Question 6

Essential amino acids

Answer 6

Amino acids that animals cannot build from materials that they take into their body

Question 7

Dipeptide bond

Answer 7

The bond between two amino acids

Question 8

Proteins and polypeptides are made on the…

Answer 8

Ribosomes

Question 9

Primary structure (3)

Answer 9

• The unique amino acid sequence of a protein
• Held by Peptide bonds
• Folds over to form secondary structure

Question 10

Secondary structure (3)

Answer 10

• The coiling and pleating of parts of the polypeptide molecule
• Forms an alpha helix or a beta pleated sheet
• Held by H-bonds

Question 11

Tertiary structure (3)

Answer 11

• The globular structure of a protein
• Made from folded over alpha helices and beta pleated sheets
• Held by disulfide bridges, ionic bonds, H-bonds and hydrophobic interactions

Question 12

The importance of maintaining tertiary structure (3)

Answer 12

• Tertiary structure is vital for the proteins function
• Hormones have to be a specific shape to fit hormone receptors
• Enzymes have specifically shaped active sites for substrates to fit in

Question 13

Effect of an increase in heat (3)

Answer 13

• As heat increases, the molecule gains KE
• The molecule vibrates and breaks H-bonds breaking the structure
• With the shape of the active site changed, the enzyme cannot function

Question 14

Effect of an increase in pH (3)

Answer 14

• As the pH deviates from 7 the concentration of H+ ions increase
• Some H-bonds and ionic bonds are broken as the electrostatic attraction is too great
• The shape of the active site is changed as tertiary structure is lost

Question 15

Hydrophilic R groups

Answer 15

Water soluble as water molecules can cluster around it

Question 16

Hydrophobic R groups

Answer 16

Are water insoluble as they turn inwards away from the water source

Question 17

Globular proteins (4)

Answer 17

• Roll up to form a ball
• Usually soluble
• Usually have metabolic roles
• Examples include enzymes, antibodies and plasma proteins

Question 18

Fibrous proteins (4)

Answer 18

• Form fibres
• Usually insoluble
• Usually have structural roles
• Examples include collagen in cartilage and keratin in hair

Question 19

Quaternary structure (2)

Answer 19

• Only some proteins have quaternary structure
• Proteins can have quaternary structure if they have a prosthetic group or more than one polypeptide subunit joined together

Question 20

Haemoglobin (6)

Answer 20

• Consists of two alpha chains, two beta chains and four haem rings
• Carries O2 and CO2
• Haem gives haemoglobin its colour
• Globular
• Has quaternary structure as it has multiple polypeptide sub units and a prosthetic group
• Soluble

Question 21

Collagen (6)

Answer 21

• Transport protein
• Fibrous protein
• Made up of three polypeptide chains
• Hydrogen bonds between each polypeptide chain gives the protein its strength
• Each collagen makes staggered covalent bonds with other collagen molecules
• Insoluble

Question 22

Functions of proteins (5)

Answer 22

• Prevents artery walls from bursting
• Provides a strong connection that allows muscles to pull bones for movement
• Bones are made from collagen
• Cartilage an connective tissues are made from collagen
• Collagen can be injected to revive skin conditions

Question 23

Haemoglobin (6)

Answer 23

• Consists of two alpha chains, two beta chains and four haem rings
• Carries O2 and CO2
• Haem gives haemoglobin its colour
• Globular
• Has quaternary structure as it has multiple polypeptide sub units and a prosthetic group
• Soluble

Question 24

Collagen (6)

Answer 24

• Transport protein
• Fibrous protein
• Made up of three polypeptide chains
• Hydrogen bonds between each polypeptide chain gives the protein its strength
• Each collagen makes staggered covalent bonds with other collagen molecules
• Insoluble

Question 25

Functions of proteins (5)

Answer 25

• Prevents artery walls from bursting
• Provides a strong connection that allows muscles to pull bones for movement
• Bones are made from collagen
• Cartilage an connective tissues are made from collagen
• Collagen can be injected to revive skin conditions

Question 27

What makes collagen so strong (7)

Answer 27

• Every third amino acid is glycine in the polypeptide chain
• Glycine is a small molecule so they can be tightly bound
• The chains are held together by H-bonds
• Each collagen molecule forms covalent bonds called cross links with neighbouring molecules
• The cross links are staggered along the collagen molecule to prevent lines of weakness
• Their result is a structure called a fibril
• Many fibrils together fomr a fibre

Question 28

The Biuret Test (5)

Answer 28

• The Biuret test is the test if a sample contains proteins
• Add sodium or potassium hydroxide to the sample
• Add copper sulfate and leave for 5 minutes
• Polypeptides present -> purple
• Polypeptide not present -> blue

Question 29

Antibodies (4)

Answer 29

• Globular
• Identifies and neutralises pathogens
• Binds onto the antigens of pathogen by the lock and key hypothesis
• Tags pathogens so they can be englufed by phagocytes

Question 30

Actin and Myosin (3)

Answer 30

• Fibrous
• Myosin converts chemical enrgy into mechanical energy in the form of ATP
• Actin form thin filaments that transmit force generated by myosin to the end of the muscle

Question 31

Insulin (2)

Answer 31

• Blobular
• Regulates carbohydrate and fat metabolism by causing cells to absorb more glucose from the blood and converts it to glucagon

Question 32

Monomer

Answer 32

A single molecule that can combine to make a long chain of monomers called a polymer

Question 33

Which enzymes digest proteins?

Answer 33

Trypsin

Chyrotrypsin

Question 34

Effect of heat on proteins

Answer 34

• Molecules gain KE as heat increases
• Molecules vibrate more vigorously causing ionic and hydrogen bonds to break
• Protein loses secondary and tertiary structure so is therefore denatured