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Molecules and Cells > Amino Acids, Proteins, Polysaccharides, Lipids > Flashcards

Amino Acids, Proteins, Polysaccharides, Lipids Flashcards

1
Q

what are the key biological roles of proteins

A

transport
storage
enzyme catalysis
motion
skeletal support
immune protection
nerve impulse transmission
control of metabolism, growth and differentiation

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2
Q

what are examples of proteins that aid with transport

A
  • oxygen on haemoglobin
  • the sodium potassium pump
  • cellular uptake of glucose
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3
Q

what is an example of a protein that aids with storage

A

ferritin in the liver that stores iron ions

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4
Q

why is enzyme catalysis of key biological importance

A

allows reactions to take place in cells at 37 degrees rather than at 200 - without these enzymes the reactions would not be able to proceed within the human body

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5
Q

how do proteins aid with motion

A

muscle protein and intestinal flagallae

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6
Q

how do proteins aid with skeletal support

A

collagen in bones and skin

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7
Q

how do proteins aid with immune protection

A

antibodies

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8
Q

how do proteins aid with nerve impulse transmission

A

neuronal receptors

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9
Q

how do proteins aid with control of metabolism, growth and differentiation

A

insulin, gene repressors, epidermal growth factor

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10
Q

what is the basic structure of proteins

A

they consist of a single polypeptide chain such as prolactin, or could exist as several interacting chains such as pyruvate dehydrogenase

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11
Q

what is an unbranched polypeptide chain a polymer of

A

amino acids linked by peptide bonds

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12
Q

what is the smallest functional protein

A

a tripeptide, with only 3 amino acids joined together, called thyrotropin releasing hormone

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13
Q

how many different amino acids are there that proteins are made from

A

20

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14
Q

how are amino acids aysmmetric

A

the central, or alpha, carbon atom in amino acids has four different groups attached to it

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15
Q

what is the exception to the rule that amino acids alpha carbon has four different groups

A

glycine

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16
Q

what are the two isomers of amino acids called

A

the d isomer and the l isomer

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17
Q

what is the l isomer of amino acids like

A

the Nh2 group is on the left hand side of the central carbon

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18
Q

what is the d isomer of amino acids like

A

the Nh2 group is on the right hand side of the central carbon

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19
Q

when does the d isomer occur

A

in bacterial cell walls, but not in proteins

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20
Q

what is the isomer of amino acids that is contained in proteins

A

the l isomer

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21
Q

what does cationic mean

A

fully protonated

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22
Q

what does zwitterion mean

A

dipolar - positive and negative charge

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23
Q

how are zwitterion amino acids formed

A

when the carboxyl group on the amino acid dissociates its hydrogen ion to counteract an increase in the alkilinity in the medium of the amino acid

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24
Q

what does anionic mean

A

all the protons are lost

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25
Q

what is the pH of cationic amino acids

A

1

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26
Q

what is the pH of dipolar amino acids

A

7.4

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27
Q

what is the pH of anionic amino acids

A

11

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28
Q

how many different classifications of amino acids are there

A

7

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29
Q

what is the aliphatic classification of amino acids

A

when the r group contains only carbon and hydrogen

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30
Q

what is the hydroxyl classification of amino acids

A

when the r group has a hydroxyl group

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31
Q

what is the sulfur classification of amino acids

A

when the r group contains sulfur

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32
Q

what is the aromatic classification of amino acids

A

when the r group contains an aromatic ring

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33
Q

what is the acidic classification of amino acids

A

when the r group contains a carboxylic acid group

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34
Q

what is the basic classification of an amino acid

A

the r group has an amino group

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35
Q

what is the imino classification of an amino acid

A

this is proline, where there is a 5 membered ring in the r group

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36
Q

are amino acids restricted to just one classification

A

no

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37
Q

what are the different ionisation characters of amino acid r groups

A
  • neutral
  • basic
  • acidic
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38
Q

what are the neutral amino acids

A
  • glycine
  • alanine
  • valine
  • leucine
  • isoleucine
  • serine
  • threonine
  • methionine
  • proline
  • phenylalanine
  • tryptophan
  • asparagine
  • glutamine
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39
Q

what are the basic amino acids

A
  • lysine
  • arginine
  • histidine
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40
Q

what are the acidic amino acids

A
  • aspartate
  • glutamate
  • cysteien
  • tyrosine
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41
Q

what is electronegativity

A

the power of an atom to attract electrons toward itself

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42
Q

why are polar r groups hydrophilic

A

charge

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43
Q

are polar r groups hydrophilic or hydrophobic

A

hydrophilic

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44
Q

are nonpolar r groups hydrophilic or hydrophobic

A

hydrophobic

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45
Q

what is hydroxyproline

A

a post synthetic modification of the proline side chains. done so the hydroxyl group can stabilise collage fibre

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46
Q

what does insufficient hydroxylation of hydroxyproline lead to

A

scurvy

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47
Q

what is y-carboxyglutamate

A

post synthetic modificationo f glutamate. carboxylation of glutamate in prothrombin

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48
Q

what does lack of carboxylation of glutamate lead to

A

haemorrhage

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49
Q

what is o-phosphoserine

A

phosphorylated serine - the most common form of regulation of protein activity

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50
Q

what is the primary structure of a protein

A

the amino acid sequence

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51
Q

what is the secondary structure of an amino acid

A

the arrangement in space of amino acids close to one another in a polypeptide chain

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52
Q

what are some examples of secondary structure

A

alpha helixes and beta pleated sheets

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53
Q

what is tertiary structure

A

the 3-D structure of all the atoms in a single polypeptide chain - the interactions between r groups fold proteins into a compact 3d shape

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54
Q

what is quaternary structure

A

the 3d interaction of protein subunits in proteins with more than one polypeptide chain

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55
Q

what is an amino acid residue

A

when two or more amino acids combine to form a polypeptide, the elements of water are removed. what is left of each amino acid is called an amino acid residue

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56
Q

describe alpha helixes

A
  • a form of secondary structure
  • rod like, right handed shape
  • found in strong, extensible proteins
  • stabilised by hydrogen bonds
  • the carbon monoxide group is hydrogen bonded to the nh amino acid
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57
Q

what are examples of proteins with alpha helixes

A

haemoglobin, myoglobin, keratins, fibrins, myosin

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58
Q

how many amino acid residues are there per turn of the alpha helix

A

3.6

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59
Q

describe beta pleated sheets

A

zig zag chains
several chains side by side
the carbon monoxide and nh groups align, and hydrogen bonding occurs
this creates a sheet like structure

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60
Q

where are beta pleated sheets found

A

in proteins where flexibility is needed like silk fibroin

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61
Q

what are parallel beta pleated sheets

A

the chains run in the same direction, and the atoms are orientated in the same way

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62
Q

what are anti parallel beta pleated sheets

A

these are when the chains run in opposite diections

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63
Q

what are triple helixes

A

structure found only in collagen. three chains wound roung each other to form a rope like structure. there are no hydrogen bonds in each chain. each chain is made up of around 1000 amino acids. each chain has a repeating structure, and they are held together by hydrogen bonds

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64
Q

what is collagen

A

a major component of connective tissue like skin, bone and tendons - they are very strong, water insoluble fibres

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65
Q

what is within the helix

A

a small glycine residue - bulky r groups on either side of the glycine prokect outward

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66
Q

how are the chains intra and inter molecularly cross linked

A

covalent bonds between lysine and histidine

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67
Q

what are fibrous proteins

A

principally structural proteins that are insoluble and metabolically unreactive

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68
Q

what are examples of fibrous proteins

A
  • collagen
  • keratin
  • fibrin
  • elastin
  • myosin
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69
Q

what is keratin found in

A

skin hair fur and wool

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70
Q

what is fibrin found in

A

blood clots

71
Q

what is elastine found in

A

elastic fibres of connective tissue like arterial walls

72
Q

where is myosin found

A

in muscle

73
Q

what are globular proteins

A

spherical proteins where the backbone of the chains fold on itself. they are water soluble and form compact structures

74
Q

what sort of structures are found within globular proteins

A

tertiary and quaternary structures

75
Q

what are globular proteins with tertiary structures

A

myoglobin and actin

76
Q

what are globular proteins with quaternary structures

A

haemoglobin

77
Q

what is myoglobin

A

a globular protein associated with tertiary structures that specialises in oxygen storage in muscles

78
Q

describe the structure of myoglobin

A

made of single chain with 153 amino acids. there are 8 helical regions, joined by regions of random coiling where the chain makes a major directional change.
the interior contains entirely non polar residues except for two non polar histidine residues, which allows for the attachments and function of haem group.
the prosthetic haem group is held in a hydrophobic pocket, and held in positition by hydrophobic interactions between haem porphyrin ring and non polar side chains of amino acids in surrounding helical segments.

79
Q

why is the prosthetic haem group in myoglobin so important

A

absence would lead to an apoprotein which is not as tightly folded

80
Q

what is haemoglobin

A

a protein associated with quaternary structures that has a role in oxygen transport. two pairs of polypeptide chains are folded in a shape similar to myoglobin. four haem groups lie on the surface of the molecule in individual pockets, far apart. each alpha subunit is in contact with both beta chains. few interactions occur between the two alpha or two beta chains

81
Q

how many amino acids are in the alpha chains on haemoglobin

A

141

82
Q

how many amino acids are in beta chains of haemoglobin

A

146

83
Q

what are the two half molecules of haemoglobin made up of

A

an alpha and a beta chain

84
Q

what is formed when the two half molecules of haemoglobin are fitted together

A

a central open channel

85
Q

where are peripheral proteins

A

on the membrane surface

86
Q

where are integral proteins

A

within the lipid bilayer

87
Q

what do channel proteins do

A

they form a channel in the membranes and facilitate movement of small molecules across the membrane which is known as simple diffusion

88
Q

what do carrier proteins do

A

they bind to transported molecules which is known as facilitated diffusion

89
Q

what is another way that molecules can pass over the membrane

A

shuttling mechanism - bind, transfer, transfer, release

90
Q

what is an example of a messenger protein

A

hormones

91
Q

what do hormones do

A

they allow cells to communicate with each other

92
Q

what are the modes of action of messenger proteins

A
  • influence the rate of synthesis of enzymes and other proteins
  • affect the rate of enzymatic catalysis
  • alter permeability of cell membranes
93
Q

how do hormones allow cells to communicate with each other

A
  • hormone binds to receptor
  • message relayed to the inside of the cell
  • cascade of events
  • cellular action
94
Q

what is another example of messenger proteins

A

insuline
glucagon
human growth hormone

95
Q

what does insulin do

A

sugar uptake by cells from the bloodstream

96
Q

what does glucagon do

A

sugar release by cells into the bloodstream

97
Q

what can hormones be derivatives of

A
  • protein
  • polypeptide
  • amino acid

or steroids

98
Q

what are enzymes

A

globular proteins that are biological catalysts. increase reaction rates by up to 10 to the power of 20

99
Q

are enzymes highly specific

A

yes

100
Q

what proteins are involved in muscular contraction

A

myosin and actin

101
Q

what proteins are involved in immune protection

A

antibodies and cytokines

102
Q

what are polysaccharides

A

molecules built up from monosaccharides that function in storage and structure

103
Q

what are monosaccharides

A

building blocks of complex carboyhdrates

104
Q

what are aldoses

A

monosaccharides with an aldehyde group

105
Q

what are ketoses

A

monosaccharides with a ketone group

106
Q

what is glucose

A

aldose monosaccharide with linear and ring form

107
Q

what are disaccharides

A

dehydration/hydrolysis reactions of monosaccharide units that form or catabolise complex carboyhdrates

108
Q

what are polysaccharides

A

isomers of monosaccharides that give rise to a variety of polysaccharides

109
Q

what are examples of polysaccharides

A

starch and cellulose

110
Q

what is starch

A

a 1-4 linkage of alpha glucose. it is a food reserve

111
Q

what is amylose

A

unbranched starch

112
Q

what is amylopectin

A

branched glucose units - linked units until the branch point

113
Q

what is glycogen

A

has the same structure as starch but is more highly branched - the actual structure resembles a tree branch. it is also a food reserve, and has an inner region and an outer region. at the branch point there is a linkage

114
Q

what is cellulose

A

unbranched, linked glucose units that cannot be digested by animal’s enzymes (except for some ruminants which contain beta glycosidases)

115
Q

what is beta-glucosidase

A

an enzyme that catalyses the hydrolysis of the glycosidic bonds of cellobiose - this results in the production of glucose, which is an important step for the effective utilisation of cellulose

116
Q

what role does cellulose play

A

a structural one. about 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall

117
Q

what are parallel cellulose molecules held together by

A

hydrogen bonds between the hydroxyl groups attached to the carbon atoms

118
Q

what is a cellulose molecule

A

an unbranched beta glucose polymer

119
Q

what are lipids

A

fatty acids such as triglycerides, diglycerides, and sterols

120
Q

what are triglycerides

A

these are lipids involved in storage, such as tristearine glycerol

121
Q

what are diglycerides

A

lipids involved in membrane structure, such as phosphatidylcholine and phosphatidylglycerol

122
Q

what are sterols

A

lipids involved in membrane structure like cholesterol

123
Q

what are glycerides

A

these are based on glycerol

124
Q

what is phosphatidylcholine

A

a diglyceride which is a major phospholipid of membranes

125
Q

what are triglycerides main role

A

storage compounds

126
Q

what are diglycerides main role

A

major component of biological membranes

127
Q

what are fatty acids

A

acyl lipids

128
Q

what are examples of sterols

A

cholesterol
cortisol
estrogen
testosterone

129
Q

how do monosaccharides link

A

through glycosidic bonding, where the OH group on the 1st carbon of the one monosaccharide binds with the hydrogen ion on the 4th carbon of another monosaccharide

130
Q

what does it mean if a disaccharide has been labelled as alpha

A

the two monosaccharides that make up the molecule are lined up next to each other

131
Q

what does it mean if a disaccharide has been labelled as beta

A

the two monsaccharides that make up the molecule are stacked

132
Q

what are monosaccharides named after

A

according to the number of carbon atoms

133
Q

what are examples of monosaccharides

A

glucose, fructose, galactose

134
Q

what breaks down glucose

A

the enzyme amylase

135
Q

what does glucose have to cross in order to provide the brain with nutrients

A

the blood brain barrier

136
Q

what are polysaccharides involved in

A

storage and structure

137
Q

what are starches

A

molecules with molecular bonds between sugar molecules that human intestial enzymes can break down

138
Q

what are dietary fibres

A

molecules that intestinal enzymes cannot break down, and will pass through the small intestine undigested. they are somewhat broken down by bacteria in the large intestine, and will pass on as the bulk of faeces matter.

139
Q

why are dietay fibres critical

A

they slow the absorption of simple sugars in the small intestine as well as increasing weight of stools to reduce constipation

140
Q

what are examples of disaccharides

A

maltose, sucrose, and lactose

141
Q

give a summary of the breakdown of disaccharides

A

the appropriate enzyme will break it back down into the two monosaccharides. these monosaccharides are absorbed through the gut lining into the bloodstream

142
Q

what are the names of the more complex carbohydrates

A

oligosacchardies and polysaccharides

143
Q

what are the functions of polysaccharides

A

broken down into monosacchardies for immediat energy use or stored away for use when needed

144
Q

what are monosaccharides and disaccharides

A

simple sugars that can be readily absorbed by the body

145
Q

when can dietary fibres be partially absorbed

A

with the help of gut bacteria

146
Q

what are the dispensible amino acids

A

these are the amino acids that our body can make in good quantity. they include:
- asparagine
- alanine
- serine
- aspartic acid
- glutamic acid

147
Q

what are the essential amino acids

A

these are the ones we cant make on our own, and must obtain from diet. they include:
- tryptophan
- leucine
- isoleucine
- valine
- methionine
- histidine
- threonine
- phenylalanine
- lysine

148
Q

what are the conditionally essential amino acids

A

these are the ones made most of the time in our body. they include:
- tyrosine
- proline
- glycine
- glutamine
- cysteine
- originine

149
Q

what does it mean to describe an amino acid as zwitterion

A

this means they are double ions, as they have a positive charge from the amide group and a negative charge from the carboxyl acid group

150
Q

what is the composition of amino acids (basically, not including the R group that gives them their specific features and functions)

A

an amine group with a positive charge and a carboxyl acid group with a negative charge. these two groups are attached to the alpha carbon

151
Q

what feature of the cell can aid with the proteins taking their shape

A

the endoplasmic reticulum

152
Q

what form of amino acids are proteins exclusively formed from

A

levo orientated amino acids

153
Q

how would the strength of the peptide bonds linking amino acids be described

A

rigid

154
Q

what is an example of a quaternary structure

A

haemoglobin with four polypeptide subunits coming together

155
Q

what are the two main types of protein

A

globular and fibrous

156
Q

what are the functions of globular proteins

A

enzymes or transport

157
Q

what is the main function of fibrous proteins

A

structure

158
Q

example of a transport protein

A

haemoglobin

159
Q

example of a fibrous protein

A

collagen

160
Q

what are the main functions of polysaccharides

A

storage and structure

161
Q

which polysaccharides function in storage

A

glycogen and starch

162
Q

which polysaccharides function in structure

A

cellulose
chondroitin sulphate
peptidoglycan

163
Q

what are the monomers of lipids

A

fatty acids

164
Q

what are the three main types of lipids

A

triglycerides
diglycerides
steroles

165
Q

what is the function of triglycerides

A

storage

166
Q

what is the function of diglycerides

A

membrane structure

167
Q

what is the function of sterols

A

membrane structure

168
Q

what are some triglycerides

A

tristearine
glycerol

169
Q

what are some diglycerides

A

phosphatidylcholine
phosphatidoglycerol

170
Q

sterol example

A

cholesterol

171
Q

describe the bond in amylose

A

alpha 1-4 linked

172
Q

describe the bond is amylopectin

A

alpha 1-4 linked unit

173
Q

describe the bond at which the branch point occurs in starch

A

alpha 1-6 link

174
Q

describe the structure of cellulose

A

unbranched beta 1-4 linked glucose units

Molecules and Cells (13 decks)

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