proteins

Question 1

what are proteins?

Answer 1

• functional capabilities of a cell

Question 2

why is there more proteins than genes?

Answer 2

• because of processes changing isoforms of different proteins

Question 3

what are the building blocks of proteins?

Answer 3

• amino acids
• determine genetic code

Question 4

what determines the identification of amino acids?

Answer 4

• variable group/ side chain

Question 5

what are amino acids joined by? what determines function?

Answer 5

• joined covalently by peptide bonds
• how they are folded determines function

Question 6

what is a peptide?

Answer 6

• shortened parts of a protein

Question 7

what is primary structure?

Answer 7

• describe the amino acid sequence of a protein
• base determinant of protein shape and function

Question 8

where do peptide bonds form in the primary structure?

Answer 8

• form between carboxyl group and amino group

Question 9

what is the secondary structure?

Answer 9

• how peptides are folded
• force responsible is hydrogen bonds (10-100x weaker than covalent)

Question 10

what does abundance of H atoms give rise to?

Answer 10

• many connectors that stabilise the secondary structure
• makes up for the fact that hydrogen bonds are weak

Question 11

how are hydrogen bonds formed in the secondary structure?

Answer 11

• created by a hydrogen atom with partial positive charge an atom usually O or N with partial negative charge

Question 12

what are the most widely encountered structures in secondary structure?

Answer 12

• a helix
• b pleated sheet

Question 13

what is the tertiary structure?

Answer 13

• confirmation of an entire polypeptide> peptide
• stabilised by H bonds but use other interactions; electrostatic bonds, van der whaals interaction, disulfide bonds and hydrophobic interaction

Question 14

what are electrostatic bonds?

Answer 14

• ionic bonds formed between positive and negatively charged groups

Question 15

what are van der whaals interactions?

Answer 15

• non- covalent attraction due to movement of ions in atomic or molecular orbitals

Question 16

what are disulfide bonds?

Answer 16

• forms between sulfhydryl group of amino acid cystine

Question 17

what are hydrophobic interactions?

Answer 17

• tendency for hydrophobic molecules to cluster together when immersed in water
• come together in a folded protein
• forces are a result of a mutual repulsion of surrounding water

Question 18

what is the quaternary structure?

Answer 18

• interactions between sub- units of polypeptide chains

Question 19

describe the universality of interactions

Answer 19

• H bonds, electrostatic bonds, van der whaals interactions and hydrophobic interactions develop both within+ across all classes of biomolecules

Question 20

what is denaturation of a protein?

Answer 20

• breaking of bonds within a protein molecule
• usually irreversible; affects the function of proteins
• occurs due to environmental factors> heat, pH levels

Question 21

what are enzymes?

Answer 21

• essential catalysts that target substrates
• accelerate metabolic reactions
• named after the substrate or type of reaction they catalyse

Question 22

what are reactants called?

Answer 22

• substrates

Question 23

what are the three main features of enzymes?

Answer 23

• speed up reactions (10^5- 10^17)
• display high specificity> each enzyme catalyses 1 or a group of reactions
• catalytic power is regulated

Question 24

what is the active site?

Answer 24

• complementary structure of enzyme and substrate
• found at the surface of the enzyme

Question 25

what is the lock and key theory?

Answer 25

• attraction is at a small area known as active site
• only complementary to one substrate

Question 26

what is the induced fit model?

Answer 26

• not complementary to just one so enzyme undergoes conformation change on interaction with substrate

Question 27

what do many enzymes need the presence of?

Answer 27

• need nonprotein chemical entities or cofactors in their active site
• usually metal ions or organic compounds

Question 28

what are metalloenzymes?

Answer 28

• metalloenzymes are metal ions embedded in organic compounds
  e.g., heme

Question 29

how many enzymes need a coenzyme?

Answer 29

• 1800 of 5000

Question 30

what is Michaelis constant?

Answer 30

• substrate concentration at half max rate

Question 31

describe how substrate availability affects reaction

Answer 31

• increased substrate speeds up the reaction to a point
• when all active sites are occupied the rate plateaus

Question 32

how does enzyme concentration affect reaction?

Answer 32

• more enzyme concentration increases rate of reaction

Question 33

how does temperature affect reaction time?

Answer 33

• increased temperature causes increased kinetic energy to a point before denaturation

Question 34

how does pH affect reaction time?

Answer 34

• around a pH of 8= ideal conditions for rate (below/ above - denaturation)
• changes in H+ cause removal or additions of proteins from active site