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Dr stead chem > Biochem, proteins, amino acids > Flashcards

Biochem, proteins, amino acids Flashcards

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1
Q

Draw the structure of an amino acid

A

[drawing]

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2
Q

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

A

primary amino group, carboxylic acid group

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3
Q

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

A

alpha position

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4
Q

How many naturally occurring amino acids are there?

A

about 20

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5
Q

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

A

18-22

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6
Q

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

A

chiral carbons

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7
Q

What amino acid does not have a chiral carbon?

A

glycine

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8
Q

What happens in nature in the production of amino acids?

A

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

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9
Q

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

A

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

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10
Q

Discuss the properties of amino acids

A

-have both acidic and basic properties
-classed as amphoteric

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11
Q

Why are amino acids amphoteric?

A

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

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12
Q

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

RCH(NH2)COOH + OH- –>

A

RCH(NH2)COO- + H2O

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13
Q

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

RCH(NH2)COOH + H+ –>

A

RCH(N+H3)COOH + H2O

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14
Q

At room temperature, what state are amino acids?

A

white crystalline solids

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15
Q

Name some other properties of amino acids?

A

dissolve in water and have high melting points

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16
Q

Why do amino acids have such high melting points?

A

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

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17
Q

What is a zwitterion?

A

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

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18
Q

In strong alkali, what happens to a zwitterion?

A

COO- zwitterion loses a proton/acts as an acid

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19
Q

In strong acid, what happens to a zwitterion?

A

N+H3 zwitterion accepts protons/acts as a base

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20
Q

How does the zwitterion behave in acid/alkaline conditions?

A

as a buffer

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21
Q

How do amino acids join together to form peptides?

A

by peptide links

22
Q

What type of polymerisation do amino acids undergo?

A

condensation - water is formed as well as the peptide

23
Q

How many different ways are there to make a dipeptide?

A

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

24
Q

In the body, what is condensation polymerisation catalysed by?

A

enzymes

25
Q

Describe the primary structure of a protein

A

sequence of amino acids

26
Q

Describe the secondary structure of a protein

A

-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

27
Q

Describe the tertiary structure of a protein

A

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

28
Q

What is a thiol functional group?

A

-SH

29
Q

Two thiol groups make…

A

a disulphide (R-S-S-R’)

30
Q

What role do disulphide bridges play in protein structures?

A

help to stabilise the tertiary structure

31
Q

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

A

temperature and pH changes

32
Q

How can mixtures of amino acids be separated?

A

thin layer chromatography

33
Q

Describe briefly TLC?

A

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

34
Q

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

A

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

35
Q

What are enzymes?

A

speed up chemical reactions in biological systems

36
Q

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

A

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

37
Q

What is the relationship between enzymes and optical enantiomers?

A

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

38
Q

How do some drugs work?

A

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

39
Q

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

A

-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

40
Q

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

A

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

41
Q

What other areas of medicine can inhibitors be used?

A

-antiviral
-anticancer

42
Q

What does DNA stand for?

A

deoxyribonucleic acid

43
Q

What does DNA contain?

A

all the genetic information of an organism

44
Q

What is the monomer of DNA?

A

nucleotides

45
Q

What is a nucleotide made up of?

A

-phosphate group
-pentose sugar
-base

46
Q

Draw a phosphate ion

A

[drawing]

47
Q

What is the pentose sugar in DNA?

A

2-deoxyribose

48
Q

Name the four bases and their complementary base pairs

A

Adenine - Thymine
Guanine - Cytosine

49
Q

When phosphate and sugar bond, what happens?

A

a water molecule is lost

50
Q

How are mononucleotides joined together?

A

by covalent phosphodiester bonds between the phosphate group and pentose sugar

51
Q
A

Dr stead chem (21 decks)

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