B1.2 Proteins

Question 1

how is the generalised amino acid

Answer 1

it is composed of a variable group, carboxyl groups, amine group

Question 2

what are the 4 groups in which the 20 amino acids are organised into

Answer 2

1. non- polar side chains= hydrophobic will contain either just a h or ch as a variable group
2. polar side chains, hydrophilic can either have an oxygen in ending except 1 sulfur in cys
3. electrically charged side chains
   - acidic= negative charge
   - basic= positive charge

Question 3

explain each of 20 amino acids

Answer 3

each have different R-groups can be polar or non-polar linear or ringed; distinct chemical and physical properties

Question 4

what do condensation reactions form

Answer 4

dipeptides and longer chain amino acids
the peptide bond forms when carboxyl group of one amino acid reacts with the amine group of another forming a dipeptide and water is a byproduct
peptide bond= covalent bond which is very stable
even longer chain amino acids= polypeptides

Question 5

what are essential amino acids

Answer 5

amino acids the body cant produce must obtain through diet
necessary for growth, maintenance and repair of bodys tissues and organs

Question 6

what are non essential amino acids

Answer 6

produced by body from other amino acids or by breakdown of protein

Question 7

what is a genetic code

Answer 7

set of rules which specifies how info is stored in dna is translated into sequence of amino acids that make up proteins
->provides instructions for protein synthesis through processes of transcription and translation

Question 8

what is transcription

Answer 8

dna transcribed- mrna

Question 9

what is translation

Answer 9

mrna translated into sequence of amino acids

Question 10

genetic code is composed of

Answer 10

codons, groups of 3 nucleotides specify type of amino acid or stop signal required

Question 11

how is it possible to be 64 different codons but only 20 amino acids

Answer 11

degenerate some amino acids coded for by multiple coded for by multiple codons allows possibility silent mutations= change DNA sequence not result in change in amino acid sequence of protein

Question 12

what is the infinite variety peptide chains

Answer 12

ability combine 20 dif amino acids in any sequence

Question 13

what is a polypeptide

Answer 13

chain of amino acids linked by peptide bonds

Question 14

what is a protein

Answer 14

a complex 3d structure made of 1 or more polypeptide chains

Question 15

explain protein composed 1 polypeptide chain

Answer 15

amino acids interact with each other folding chain into a functional protein

Question 16

explain protein composed of more than one polypeptide

Answer 16

polypeptide chain can additionally interact with each other contributing overall structure of protein

Question 17

single chain polypeptides=

Answer 17

function; enzymes and hormones, molecules possess specific primary structure= linear sequence of amino acids that make up protein

Question 18

why is the structure of a protein important

Answer 18

biological function

Question 19

explain denaturation

Answer 19

process structure protein altered cause loss function; usually permanent
ph and temp can cause

Question 20

what can extreme change in ph affect

Answer 20

protein solubility and shape; altering proteins change- leads irreversible changes in protein structure cause inactivity

Question 21

what can high temp cause in proteins

Answer 21

can break weak hydrogen bonds holding protein structure together, cause protein to unfold and lose function

Question 22

how are amino acids linked together

Answer 22

by ribosomes to make polypeptides

Question 23

what do R groups give each amino acid

Answer 23

its unique characteristic present in polypeptide determine properties of assembled polypeptides

Question 24

R groups which are hydrophobic

Answer 24

non- polar repel water molecules

Question 25

R groups which are hydrophilic

Answer 25

polar or charged, acidic or basic, attract water molecules

Question 26

what do polar R groups contain

Answer 26

partial charges that interact with water molecules while charged R-groups can be positive charged (basic) or negative charge (acidic)

Question 27

how many levels are there of protein structure

Answer 27

4

Question 28

describe primary structure of proteins

Answer 28

specific sequence of amino acids joined together from polypeptide chain
determines how polypeptides chain will fold, leading to 3d structure protein precise position each amino acid within protein is critical determing its shape

Question 29

describe secondary structure of proteins: pleating and coiling

Answer 29

folding patterns that occur within polypeptide chain common type secondary structure; alpha helices and beta-pleated sheets
ability fold into coils and pleats achieved through hydrogen bonding between carboxyl group and amino acid in different part of polypeptide chain. Hydrogen bonds occur regular positions help stabilize and aid in formation of secondary structure
collectively hydrogen bonds= strong, hold confirmation of protein
alpha helix hydrogen bonds from between amine hydrogen 1 amino acid and carboxyl oxygen from another amino acid 4 residues away in sequence, repeated pattern allows polypeptide chain to coil- helical structure
beta pleated sheets form sections polypeptide chain run parallel each other hydrogen bonds form between adjacent strands, individual strands forming flat surface of the sheet