Amino Acids, Proteins, Polysaccharides, Lipids Flashcards
(174 cards)
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
2
Q
what are examples of proteins that aid with transport
A
- oxygen on haemoglobin
- the sodium potassium pump
- cellular uptake of glucose
3
Q
what is an example of a protein that aids with storage
A
ferritin in the liver that stores iron ions
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
5
Q
how do proteins aid with motion
A
muscle protein and intestinal flagallae
6
Q
how do proteins aid with skeletal support
A
collagen in bones and skin
7
Q
how do proteins aid with immune protection
A
antibodies
8
Q
how do proteins aid with nerve impulse transmission
A
neuronal receptors
9
Q
how do proteins aid with control of metabolism, growth and differentiation
A
insulin, gene repressors, epidermal growth factor
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
11
Q
what is an unbranched polypeptide chain a polymer of
A
amino acids linked by peptide bonds
12
Q
what is the smallest functional protein
A
a tripeptide, with only 3 amino acids joined together, called thyrotropin releasing hormone
13
Q
how many different amino acids are there that proteins are made from
A
20
14
Q
how are amino acids aysmmetric
A
the central, or alpha, carbon atom in amino acids has four different groups attached to it
15
Q
what is the exception to the rule that amino acids alpha carbon has four different groups
A
glycine
16
Q
what are the two isomers of amino acids called
A
the d isomer and the l isomer
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
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
19
Q
when does the d isomer occur
A
in bacterial cell walls, but not in proteins
20
Q
what is the isomer of amino acids that is contained in proteins
A
the l isomer
21
Q
what does cationic mean
A
fully protonated
22
Q
what does zwitterion mean
A
dipolar - positive and negative charge
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
24
Q
what does anionic mean
A
all the protons are lost
25
what is the pH of cationic amino acids
1
26
what is the pH of dipolar amino acids
7.4
27
what is the pH of anionic amino acids
11
28
how many different classifications of amino acids are there
7
29
what is the aliphatic classification of amino acids
when the r group contains only carbon and hydrogen
30
what is the hydroxyl classification of amino acids
when the r group has a hydroxyl group
31
what is the sulfur classification of amino acids
when the r group contains sulfur
32
what is the aromatic classification of amino acids
when the r group contains an aromatic ring
33
what is the acidic classification of amino acids
when the r group contains a carboxylic acid group
34
what is the basic classification of an amino acid
the r group has an amino group
35
what is the imino classification of an amino acid
this is proline, where there is a 5 membered ring in the r group
36
are amino acids restricted to just one classification
no
37
what are the different ionisation characters of amino acid r groups
- neutral
- basic
- acidic
38
what are the neutral amino acids
- glycine
- alanine
- valine
- leucine
- isoleucine
- serine
- threonine
- methionine
- proline
- phenylalanine
- tryptophan
- asparagine
- glutamine
39
what are the basic amino acids
- lysine
- arginine
- histidine
40
what are the acidic amino acids
- aspartate
- glutamate
- cysteien
- tyrosine
41
what is electronegativity
the power of an atom to attract electrons toward itself
42
why are polar r groups hydrophilic
charge
43
are polar r groups hydrophilic or hydrophobic
hydrophilic
44
are nonpolar r groups hydrophilic or hydrophobic
hydrophobic
45
what is hydroxyproline
a post synthetic modification of the proline side chains. done so the hydroxyl group can stabilise collage fibre
46
what does insufficient hydroxylation of hydroxyproline lead to
scurvy
47
what is y-carboxyglutamate
post synthetic modificationo f glutamate. carboxylation of glutamate in prothrombin
48
what does lack of carboxylation of glutamate lead to
haemorrhage
49
what is o-phosphoserine
phosphorylated serine - the most common form of regulation of protein activity
50
what is the primary structure of a protein
the amino acid sequence
51
what is the secondary structure of an amino acid
the arrangement in space of amino acids close to one another in a polypeptide chain
52
what are some examples of secondary structure
alpha helixes and beta pleated sheets
53
what is tertiary structure
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
54
what is quaternary structure
the 3d interaction of protein subunits in proteins with more than one polypeptide chain
55
what is an amino acid residue
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
56
describe alpha helixes
- 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
57
what are examples of proteins with alpha helixes
haemoglobin, myoglobin, keratins, fibrins, myosin
58
how many amino acid residues are there per turn of the alpha helix
3.6
59
describe beta pleated sheets
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
60
where are beta pleated sheets found
in proteins where flexibility is needed like silk fibroin
61
what are parallel beta pleated sheets
the chains run in the same direction, and the atoms are orientated in the same way
62
what are anti parallel beta pleated sheets
these are when the chains run in opposite diections
63
what are triple helixes
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
64
what is collagen
a major component of connective tissue like skin, bone and tendons - they are very strong, water insoluble fibres
65
what is within the helix
a small glycine residue - bulky r groups on either side of the glycine prokect outward
66
how are the chains intra and inter molecularly cross linked
covalent bonds between lysine and histidine
67
what are fibrous proteins
principally structural proteins that are insoluble and metabolically unreactive
68
what are examples of fibrous proteins
- collagen
- keratin
- fibrin
- elastin
- myosin
69
what is keratin found in
skin hair fur and wool
70
what is fibrin found in
blood clots
71
what is elastine found in
elastic fibres of connective tissue like arterial walls
72
where is myosin found
in muscle
73
what are globular proteins
spherical proteins where the backbone of the chains fold on itself. they are water soluble and form compact structures
74
what sort of structures are found within globular proteins
tertiary and quaternary structures
75
what are globular proteins with tertiary structures
myoglobin and actin
76
what are globular proteins with quaternary structures
haemoglobin
77
what is myoglobin
a globular protein associated with tertiary structures that specialises in oxygen storage in muscles
78
describe the structure of myoglobin
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
why is the prosthetic haem group in myoglobin so important
absence would lead to an apoprotein which is not as tightly folded
80
what is haemoglobin
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
how many amino acids are in the alpha chains on haemoglobin
141
82
how many amino acids are in beta chains of haemoglobin
146
83
what are the two half molecules of haemoglobin made up of
an alpha and a beta chain
84
what is formed when the two half molecules of haemoglobin are fitted together
a central open channel
85
where are peripheral proteins
on the membrane surface
86
where are integral proteins
within the lipid bilayer
87
what do channel proteins do
they form a channel in the membranes and facilitate movement of small molecules across the membrane which is known as simple diffusion
88
what do carrier proteins do
they bind to transported molecules which is known as facilitated diffusion
89
what is another way that molecules can pass over the membrane
shuttling mechanism - bind, transfer, transfer, release
90
what is an example of a messenger protein
hormones
91
what do hormones do
they allow cells to communicate with each other
92
what are the modes of action of messenger proteins
- influence the rate of synthesis of enzymes and other proteins
- affect the rate of enzymatic catalysis
- alter permeability of cell membranes
93
how do hormones allow cells to communicate with each other
- hormone binds to receptor
- message relayed to the inside of the cell
- cascade of events
- cellular action
94
what is another example of messenger proteins
insuline
glucagon
human growth hormone
95
what does insulin do
sugar uptake by cells from the bloodstream
96
what does glucagon do
sugar release by cells into the bloodstream
97
what can hormones be derivatives of
- protein
- polypeptide
- amino acid
or steroids
98
what are enzymes
globular proteins that are biological catalysts. increase reaction rates by up to 10 to the power of 20
99
are enzymes highly specific
yes
100
what proteins are involved in muscular contraction
myosin and actin
101
what proteins are involved in immune protection
antibodies and cytokines
102
what are polysaccharides
molecules built up from monosaccharides that function in storage and structure
103
what are monosaccharides
building blocks of complex carboyhdrates
104
what are aldoses
monosaccharides with an aldehyde group
105
what are ketoses
monosaccharides with a ketone group
106
what is glucose
aldose monosaccharide with linear and ring form
107
what are disaccharides
dehydration/hydrolysis reactions of monosaccharide units that form or catabolise complex carboyhdrates
108
what are polysaccharides
isomers of monosaccharides that give rise to a variety of polysaccharides
109
what are examples of polysaccharides
starch and cellulose
110
what is starch
a 1-4 linkage of alpha glucose. it is a food reserve
111
what is amylose
unbranched starch
112
what is amylopectin
branched glucose units - linked units until the branch point
113
what is glycogen
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
what is cellulose
unbranched, linked glucose units that cannot be digested by animal's enzymes (except for some ruminants which contain beta glycosidases)
115
what is beta-glucosidase
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
what role does cellulose play
a structural one. about 80 cellulose molecules associate to form a microfibril, the main architectural unit of the plant cell wall
117
what are parallel cellulose molecules held together by
hydrogen bonds between the hydroxyl groups attached to the carbon atoms
118
what is a cellulose molecule
an unbranched beta glucose polymer
119
what are lipids
fatty acids such as triglycerides, diglycerides, and sterols
120
what are triglycerides
these are lipids involved in storage, such as tristearine glycerol
121
what are diglycerides
lipids involved in membrane structure, such as phosphatidylcholine and phosphatidylglycerol
122
what are sterols
lipids involved in membrane structure like cholesterol
123
what are glycerides
these are based on glycerol
124
what is phosphatidylcholine
a diglyceride which is a major phospholipid of membranes
125
what are triglycerides main role
storage compounds
126
what are diglycerides main role
major component of biological membranes
127
what are fatty acids
acyl lipids
128
what are examples of sterols
cholesterol
cortisol
estrogen
testosterone
129
how do monosaccharides link
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
what does it mean if a disaccharide has been labelled as alpha
the two monosaccharides that make up the molecule are lined up next to each other
131
what does it mean if a disaccharide has been labelled as beta
the two monsaccharides that make up the molecule are stacked
132
what are monosaccharides named after
according to the number of carbon atoms
133
what are examples of monosaccharides
glucose, fructose, galactose
134
what breaks down glucose
the enzyme amylase
135
what does glucose have to cross in order to provide the brain with nutrients
the blood brain barrier
136
what are polysaccharides involved in
storage and structure
137
what are starches
molecules with molecular bonds between sugar molecules that human intestial enzymes can break down
138
what are dietary fibres
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
why are dietay fibres critical
they slow the absorption of simple sugars in the small intestine as well as increasing weight of stools to reduce constipation
140
what are examples of disaccharides
maltose, sucrose, and lactose
141
give a summary of the breakdown of disaccharides
the appropriate enzyme will break it back down into the two monosaccharides. these monosaccharides are absorbed through the gut lining into the bloodstream
142
what are the names of the more complex carbohydrates
oligosacchardies and polysaccharides
143
what are the functions of polysaccharides
broken down into monosacchardies for immediat energy use or stored away for use when needed
144
what are monosaccharides and disaccharides
simple sugars that can be readily absorbed by the body
145
when can dietary fibres be partially absorbed
with the help of gut bacteria
146
what are the dispensible amino acids
these are the amino acids that our body can make in good quantity. they include:
- asparagine
- alanine
- serine
- aspartic acid
- glutamic acid
147
what are the essential amino acids
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
what are the conditionally essential amino acids
these are the ones made most of the time in our body. they include:
- tyrosine
- proline
- glycine
- glutamine
- cysteine
- originine
149
what does it mean to describe an amino acid as zwitterion
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
what is the composition of amino acids (basically, not including the R group that gives them their specific features and functions)
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
what feature of the cell can aid with the proteins taking their shape
the endoplasmic reticulum
152
what form of amino acids are proteins exclusively formed from
levo orientated amino acids
153
how would the strength of the peptide bonds linking amino acids be described
rigid
154
what is an example of a quaternary structure
haemoglobin with four polypeptide subunits coming together
155
what are the two main types of protein
globular and fibrous
156
what are the functions of globular proteins
enzymes or transport
157
what is the main function of fibrous proteins
structure
158
example of a transport protein
haemoglobin
159
example of a fibrous protein
collagen
160
what are the main functions of polysaccharides
storage and structure
161
which polysaccharides function in storage
glycogen and starch
162
which polysaccharides function in structure
cellulose
chondroitin sulphate
peptidoglycan
163
what are the monomers of lipids
fatty acids
164
what are the three main types of lipids
triglycerides
diglycerides
steroles
165
what is the function of triglycerides
storage
166
what is the function of diglycerides
membrane structure
167
what is the function of sterols
membrane structure
168
what are some triglycerides
tristearine
glycerol
169
what are some diglycerides
phosphatidylcholine
phosphatidoglycerol
170
sterol example
cholesterol
171
describe the bond in amylose
alpha 1-4 linked
172
describe the bond is amylopectin
alpha 1-4 linked unit
173
describe the bond at which the branch point occurs in starch
alpha 1-6 link
174
describe the structure of cellulose
unbranched beta 1-4 linked glucose units
