Biochem, proteins, amino acids

Question 1

Draw the structure of an amino acid

Answer 1

[drawing]

Question 2

What are the two functional groups called on an amino acid?

Answer 2

primary amino group, carboxylic acid group

Question 3

What is the position called that is adjacent to the carboxylic acid group?

Answer 3

alpha position

Question 4

How many naturally occurring amino acids are there?

Answer 4

about 20

Question 5

What is the range of amino acids that some people argue?

Answer 5

18-22

Question 6

The majority of amino acids exhibit optical isomerism as they have…

Answer 6

chiral carbons

Question 7

What amino acid does not have a chiral carbon?

Answer 7

glycine

Question 8

What happens in nature in the production of amino acids?

Answer 8

only one enantiomer is made - only one form in the body

Question 9

What happens in the lab in the production of amino acids?

Answer 9

a racemic mixture, 50:50 mixture of both enantiomers so are optically inactive

Question 10

Discuss the properties of amino acids

Answer 10

-have both acidic and basic properties
-classed as amphoteric

Question 11

Why are amino acids amphoteric?

Answer 11

contain:
-carboxylic acid group that is acidic - donate protons
-amino group that is basic - accept protons

Question 12

What is the equation for amino acids acting as an acid/donating protons?

RCH(NH2)COOH + OH- –>

Answer 12

RCH(NH2)COO- + H2O

Question 13

What is the equation for amino acids acting as a base/accepting protons?

RCH(NH2)COOH + H+ –>

Answer 13

RCH(N+H3)COOH + H2O

Question 14

At room temperature, what state are amino acids?

Answer 14

white crystalline solids

Question 15

Name some other properties of amino acids?

Answer 15

dissolve in water and have high melting points

Question 16

Why do amino acids have such high melting points?

Answer 16

-NOT because of hydrogen bonding
-because amino acids exist as zwitterions, which have ionic bonding (stronger than hydrogen bonding)

Question 17

What is a zwitterion?

Answer 17

an ion that has both a positively charged and a negatively charged group

Question 18

In strong alkali, what happens to a zwitterion?

Answer 18

COO- zwitterion loses a proton/acts as an acid

Question 19

In strong acid, what happens to a zwitterion?

Answer 19

N+H3 zwitterion accepts protons/acts as a base

Question 20

How does the zwitterion behave in acid/alkaline conditions?

Answer 20

as a buffer

Question 21

How do amino acids join together to form peptides?

Answer 21

by peptide links

Question 22

What type of polymerisation do amino acids undergo?

Answer 22

condensation - water is formed as well as the peptide

Question 23

How many different ways are there to make a dipeptide?

Answer 23

2 - can make them from different combinations of the ends of the molecules

Question 24

In the body, what is condensation polymerisation catalysed by?

Answer 24

enzymes

Question 25

Describe the primary structure of a protein

Answer 25

sequence of amino acids

Question 26

Describe the secondary structure of a protein

Answer 26

-primary structure of amino acids is held together in a particular shape by hydrogen bonds between amide hydrogen and carbonyl oxygen -can be coiled into an alpha helix -can be folded into a beta pleated sheet

Question 27

Describe the tertiary structure of a protein

Answer 27

-overall 3D structure/shape of a protein -extra bonds form between the peptide chain such as disulphide bridges and ionic bonds

Question 28

What is a thiol functional group?

Answer 28

-SH

Question 29

Two thiol groups make...

Answer 29

a disulphide (R-S-S-R')

Question 30

What role do disulphide bridges play in protein structures?

Answer 30

help to stabilise the tertiary structure

Question 31

What may affect the formation of disulphide bridges/hydrogen bonds?

Answer 31

temperature and pH changes

Question 32

How can mixtures of amino acids be separated?

Answer 32

thin layer chromatography

Question 33

Describe briefly TLC?

Answer 33

-amino acids can be located on a chromatogram using developing agents like ninhydrin or UV light -identified by Rf values

Question 34

Write the two word equations that describe the condensation and breakdown of amino acids

Answer 34

amino acids ----> (cond. polym.) peptide (polyamide) + water

Question 35

What are enzymes?

Answer 35

speed up chemical reactions in biological systems

Question 36

Aside from breaking up a substrate, what else can enzymes do?

Answer 36

-join together two substrate molecules -change the functional group of a substrate

Question 37

What is the relationship between enzymes and optical enantiomers?

Answer 37

-enzymes active sites are stereospecific -active sites only work on one enantiomer of a substrate

Question 38

How do some drugs work?

Answer 38

they are inhibitors that block the active site of an enzyme and stop it from working

Question 39

What is the challenge of finding drugs that will work with an enzyme?

Answer 39

-active site of an enzyme is very specific so is hard to find a drug that will fit snuggly in the active site -more difficult if the molecule is chiral as only one enantiomer will fit into the stereospecific active site

Question 40

What is an example of inhibitors used to treat high blood pressure?

Answer 40

ACE inhibitors - reduces the production of angiotensin so blood vessels enlarge and blood pressure is reduced

Question 41

What other areas of medicine can inhibitors be used?

Answer 41

-antiviral -anticancer

Question 42

What does DNA stand for?

Answer 42

deoxyribonucleic acid

Question 43

What does DNA contain?

Answer 43

all the genetic information of an organism

Question 44

What is the monomer of DNA?

Answer 44

nucleotides

Question 45

What is a nucleotide made up of?

Answer 45

-phosphate group -pentose sugar -base

Question 46

Draw a phosphate ion

Answer 46

[drawing]

Question 47

What is the pentose sugar in DNA?

Answer 47

2-deoxyribose

Question 48

Name the four bases and their complementary base pairs

Answer 48

Adenine - Thymine Guanine - Cytosine

Question 49

When phosphate and sugar bond, what happens?

Answer 49

a water molecule is lost

Question 50

How are mononucleotides joined together?

Answer 50

by covalent phosphodiester bonds between the phosphate group and pentose sugar