Biological molecules tonight

Question 1

Describe how a peptide bond is formed between 2 amino acids to form a dipeptide.

Answer 1

amino group and carboxylic group
Condensation reaction
Water removed

Question 2

The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how.

Answer 2

hydrogen bonds
Between amino group and carboxylic group
Forming alpha helix or beta pleated sheets

Question 3

two proteins have the same number and type of amino acids but different tertiary structures. Explain why

Answer 3

• different primary sequence of AA
• R group bond form in different places

Question 4

At what level of protein structure do hydrophobic interaction occurs?

Answer 4

Tertiary, Quaternary

Question 5

What does a haemoglobin molecule contain?

Answer 5

4 polypeptide chains
with 1 haem group

Question 6

Describe one similarity and one difference between the induced fit model of enzyme activity and the lock and key model.

Answer 6

sim
- substrate binds to AS
- enzyme substrate complexes formed

diff
As changes shape, but doesn’t change in lock and key

AS not complimentary to substrate with induced fit, but is complementary in lock and key

Question 7

The scientists expressed their results as Percentage of lipid in plasma membrane by mass. Explain how they would find these values.

Answer 7

mass of each lipid/ mass of all lipids x 100

Question 8

ester bond

Answer 8

between carbon and oxygen

Question 9

Name the type of reaction that joins monosaccharides together.

Answer 9

condensation reaction

Question 10

Which of the fatty acids, X or Y, in the figure above is unsaturated

Answer 10

Contains double bond between (adjacent) carbon atoms in hydrocarbon chain.

Question 11

what is the significance of quaternary structure in proteins?

Answer 11

holds together multiple polypeptide chains
and other molecules necessary for protein function
therefore contributing to the overall structure and function of proteins

Question 12

What are the two common secondary structure found in proteins and what causes their formation

Answer 12

alpha helix and beta pleated sheets
formed due to hydrogen bonding between carboxyl and amino residue of polypeptide chain

Question 13

Describe the structural nature of enzymes

Answer 13

globular proteins
specific tertiary structure
complementary to substrates
substrates bind to active site of enzymes

Question 14

Explain the tertiary structure of proteins and the forces involved in its formation

Answer 14

Folding of polypeptide into specific complex shape
due to IMFs between R group
e.g. Hydrogen bonds, ionic bonds, disulfide bridge and London forces

Question 15

Explain the relationship between substate concentration and enzyme activity

Answer 15

increase substrate conc increases rate of reaction
as more enzyme substrate collisions
there is a max rate when all active sites are occupied
enzymes saturation

Question 16

rate of reaction calculation

Answer 16

change in conc or substrate/ time

Question 17

what type of bond is formed in condensation reaction to create a polypeptide

Answer 17

peptide bond
between amine group of one AA and carboxyl group
releasing water

Question 18

What is the monomer of proteins, and how many naturally occurring variations exist

Answer 18

amino acid
20 variations each distinguished by unique R group

Question 19

Difference between competitive and non competitive inhibitors

Answer 19

competitive - bind the active site of enzymes, blocking substrate form binding

Non competitive inhibitors - bind to different site on enzyme - causing a conformational change that alters the shape of the active site

Question 20

what impact does Ph have on enzyme activity

Answer 20

change ion Ph away from optimum can disrupt ionic forces and hydrogen bonds
causing enzymes tertiary structure to deform
This alters the shape of the active site
reducing its complementarity to the substrate and decreasing the reaction rate

Question 21

How are polypeptides broken apart and what is required for this reaction

Answer 21

broken apart by hydrolysis reactions
requires the addition of water to break the peptide bonds

Question 22

How is the presence of proteins tested using buret test, and what constitutes a positive result

Answer 22

adding copper sulphate and sodium hydroxide to a solution
+ve - blue –> purple
shows presence of peptide bond

Question 23

How does temperature affect the rate of enzyme controlled reactions?

Answer 23

increasing temp initially increases rate of reaction by providing more kinetic energy for successful enzyme substrate collision
optim temp - enzymes denature
decreasing the rate as the active site loses its complementary shape

Question 24

Differentiate between globular and fibrous proteins structure providing examples of each

Answer 24

globular proteins have specific shape and involved in functions like enzyme catalysis and molecular signalling

fibrous proteins are structural and provide strength and flexibility
e.go collegen and keratin

Question 25

what is the primary function of enzymes in biological systems?

Answer 25

enzymes catalyse biochemical reactions
without increasing the rate of reaction without being consumed in the process

Question 26

Discuss the induced fit model of enzyme substrate interaction

Answer 26

substrates initially collide with enzymes active site and form an enzyme substrate complex. This interaction induces slight changes in shape of active site making it more complementary to the substrate, which facilitates the reaction

Question 27

what is the primary structure of a protein and what role does it play in protein shape?

Answer 27

refers to sequence of amino acids in a protein
joined by peptide bonds
controls the overall protein shape and function

Question 28

How does enzyme concentration affect reaction rate?

Answer 28

increasing enzyme conc increase rate as there are more enzymes available to catalyse substrate molecules are instantly converted to products

Question 29

Explain how enzymes reduce the activation energy of reactions

Answer 29

enzymes lower the activation energy required to initiate a reaction by binding to substrate at their active site, straining the bonds in the substrates and facilitating their conversion into products

Question 30

what is the primary structure of a protein and what role does it play in protein shape?

Answer 30

the primary structure refers to the sequence of amino acids in a protein,
joined by peptide bonds
controls the overall protein shape and function

Question 31

What is the difference between a saturated and unsaturated fatty acid

Answer 31

saturated no c=c double bonds
unsaturated one or more c=c double bonds

Question 32

(a) In humans, the enzyme maltase breaks down maltose to glucose.
This takes place at normal body temperature.
Explain why maltase:
* only breaks down maltose
* allows this reaction to take place at normal body temperature.

Answer 32

1. Tertiary structure / 3D shape of enzyme (means);

2.      Active site complementary to maltose / substrate / maltose fits into active site / active site and substrate fit like a lock and key;

3.      Description of induced fit;

4.      Enzyme is a catalyst / lowers activation energy / energy required for reaction;

5. By forming enzyme-substrate complex;

Question 33

Scientists have investigated the effects of competitive and non-competitive inhibitors of the enzyme maltase.
Describe competitive and non-competitive inhibition of an enzyme.

Answer 33

1. Inhibitors reduce binding of enzyme to substrate / prevent formation of ES complex;

2.      Inhibitor similar shape (idea) to substrate;

3.      (Binds) in to active site (of enzyme);
		Accept allows max rate of reaction to be reached / max product will eventually be formed
		
4.      (Inhibition) can be overcome by more substrate;
(Non-competitive inhibition),

5.      Inhibitor binds to site on enzyme other than active site;

6.      Prevents formation of active site / changes (shape of) active site;

7. Cannot be overcome by adding more substrate;

Question 34

Describe how A quaternary protein is formed from its monomers

Answer 34

Amino acid joined by peptide bonds
- condensation reactions
- secondary structure formed by hydrogen bonding
- teritary structure is formed by interactions between R groups
- quaternary strcutre contains more than 1 polypeptide
- Quaternary strcutre is formed by interactions/ bonds between polypeptides

Question 35

Describe how the structure of a protein depends on the amino acids it contains.

Answer 35

1. Structure is determined by (relative) position of amino acid/R group/interactions;

2.      Primary structure is sequence/order of amino acids;
3.      Secondary structure formed by hydrogen bonding (between amino acids);
		Accept alpha helix/β-pleated sheet for ‘secondary structure’
4.      Tertiary structure formed by interactions (between R groups);

5.      Creates active site in enzymes
	OR Creates complementary/specific shapes in antibodies/carrier proteins/receptor (molecules);

Question 36

Describe the structure of proteins.

Answer 36

1. Polymer of amino acids;
   2. Joined by peptide bonds;
   3. Formed by condensation;
   4. Primary structure is order of amino acids;
   5. Secondary structure is folding of polypeptide chain due to hydrogen bonding;
   Accept alpha helix / pleated sheet
   6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide bonds;
   7. Quaternary structure is two or more polypeptide chains.

Question 37

The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how.

Answer 37

Hydrogen bonds form amino acids between NH and c=o group
beta pleased sheet

Question 38

Two proteins have the same number and type of amino acids but different tertiary structures. Explain why.

Answer 38

Different sequence of Amino acids
different primary structures
Form ionic/ hydrogen/ disulphide bonds in different places

Question 39

Name the chemical element found in all amino acids that is not found in triglycerides.

Answer 39

nitrogen

Question 40

Aspartic acid and pralinee are both amino acids. Describe how two amino acids differ from one another.

Answer 40

different R groups