Lecture 5/6 Flashcards
1
Q
What are alpha helices
A
Coil stabilized by hydrogen bonding btwn NH of 1 peptide bond CO of peptide bonds four AA’s in each direction
2
Q
What are beta sheets
A
2 polypeptide regions whose backbones are parallel antiparallel
- R groups stick out
- H bonding btwn CO of 1 peptide group and NH group of adjacent peptide
3
Q
What are motifs
A
common combo’s of a-helices and b-sheets connected by looped regions of varying lengths
4
Q
What is the purpose of motifs?
A
.
5
Q
What are domains
A
discrete, locally folded unit of tertiary structure that usually has a specific fxn (& contains several motifs)
6
Q
Example of domain?
A
enzyme glyceraldehyde phosphate dehydrogenase is a single polypeptide chain folded into two functional domains
7
Q
Thermodynamically-based approach defines protein domains as?
A
cooperative chain segments,
independently folded
8
Q
How many disulfide linkages that hold 2 chains of insulin together?
A
3
- 2 intermolecular, 1 intra
9
Q
Insulin molecules come together as ____ (stabilized by ___ zinc ions) for storage in the granules of the beta cells of the panreas
A
- hexamers
2. 2 zinc ions
10
Q
When do insulin molecules get secreted and how
A
when you start to eat a meal
- into bloodstream via exocytosis
11
Q
Diff btwn RNA and DNA?
A
- RNA has 2’OH and DNA has 2’H
1. RNA has uracil, DNA has thymine (alkyl group instead of H beside =O)
12
Q
What is phosphoester bond
A
btwn P1 and O
13
Q
What is phosphoanhydride bond
A
btwn P2 and O, P3 and O
14
Q
Adenine vs adenosine
A
Adenine is base only adenosine is sugar + base
15
Q
Fxns of nucleotides? Example of each
A
- Carry chemical nrg in their easily hydrolyzed phosphoanhydride bonds
e. g. ATP - Combine w/other groups to form coenzymes
e. g. coenzyme A - Used as small intracellular signaling molecules in the cell
e. g. cyclic AMP
16
Q
What are polysaccharides
A
polymers of sugar and sugar derivatives
17
Q
What are the monomers of polysaccharides
A
monosaccharides
18
Q
Formula for polysaccharides
A
CnH2nOn (n=3-7)
19
Q
What are carbohydrates
A
Hydrates of carbon
20
Q
Most common sugar in biological world
A
aldohexose D-glucose, C6H12O6
21
Q
Examples of pentoses
A
Ribose, deoxyribose
22
Q
How are carbons of glucose numbered
A
Beginning w/more oxidized end (carbonyl end)
23
Q
If OH is on the right, it is ___.
If OH is on the left, it is ___.
A
Right = D Left = L
24
Q
Most naturally occurring sugars are ___ isomers
A
D isomers
25
What are isomers
Same formulas but differ only in spatial arrangement of atoms
26
Why are these small differences in isomers have such a big affect
Have minor changes in chemical properties of the sugars but differences recognized by enzymes & other proteins thus have major biological effects
27
How is pyranose ring, predominant form of glucose, formed?
C1 aldehyde reacts w/OH on C5
| - C1 is now hemiacetal
28
How many alternative forms of pyranose ring structures are there? What are they?
- 2
| - alpha and beta
29
What determines the form of pyranose ring structure? Is alpha up or down, is beta up or down?
Spatial orientation of hydroxyl group of C1
- Alpha: 1' OH is below, 4' OH is below
- Beta: 1' OH is above, 4' OH is below
30
What is another name for C1 carbon of glucose
Anomeric carbon
31
Starch and glycogen have ___-D-glucose
Alpha
32
Cellulose has __-D-glucose
Beta
33
What is expelled during condensation of 2 monosaccharides, what is formed?
Water expelled, O-glycosidic bond formed
34
How is O-glycosidic bond formed
Anomeric carbon reacts w/a hydroxyl (disaccharides)
35
Examples of disaccharides joined by O-glycosidic bonds between 2 monomers
Maltose, lactose, sucrose
36
How are disaccharides distinguished by?
Component monosaccharides and their order, which carbons are involved in their glycosidic bond & configurations of the anomeric carbons
37
Even tho maltose and cellulose are both dimers of glucose, why is there such a big diff
- Significant impact on shape of resulting molecule, which determines the bonds accessible to specific enzymes
- diff enzymes are needed to catalyze their hydrolysis
38
What is lactose
principal carbohydrate in milk (& milk products)
39
How can disaccharides enter cells
Must be hydrolyzed to monosaccharides extracellularly
40
How can disaccharides enter cells
Must be hydrolyzed, by enzymes attached to outer surface of epithelial cells lining small intestine, to monosaccharides extracellularly
41
Enzyme that hydrolyzes lactose
Lactase (human
| - B-galactosidase (bacteria)
42
Why do people become lactose intolerant
Stop producing enough lactase
43
How is N-glycosidic bond produced
Anomeric carbon reacts w/nitrogen (e.g. nucleotides)
44
What groups allow formation of branched of sugars
Multiple OH groups participating in glycosidic bonds
45
What are 3 fxns of polysaccharides in living organisms (3 S's)
Storage
Structure
Signaling
46
Storage polysaccharide in plants? In animals? Are they alpha or beta glucoses
Plants: starch
Animals: Glycogen
Both a-D-glucose
47
What makes up starch
10-30% amylose
| 70-90% amylopectin
48
Is amylose branched or unbranched? Amylopectin?
- Amylose: unbranched
| - Amylopectin - branched
49
Where is glycogen found in animals? Difference btwn areas?
- liver (storage)
| - muscles (immediate nrg)
50
Amylose, amylopectin, and glycogen are all made of α-D-glucose. What distinguishes them?
Bonds
51
What are oligosaccharides?
Short chains
52
Characteristics of amylose
- Linear polymer
| - 1 ->4 linkage btwn glucose monomers
53
Characteristics of amylopectin
- Branched polymer
| - 1->4 and 1->6 linkage btwn every 25th glucose
54
Characteristics of glycogen
- Branched polymer
| - 1->4 and 1->5 linkage btwn every 10th glucose
55
Why are amylopectin and glycogen branched?
Enzymes catalyze removal of glucose from non-reducing ends (ends of branches) thus a lot of glucose can be released at once rather than one at a time if these polymers were a single chain
56
Cellulose is __-D-glucose and 1->___ linkage
b-D-glucose 1->4 linkage
57
Mammals cannot hydrolyze
β (1à4) bond and therefore
cannot use cellulose as food
Really?
.
58
Cell walls of most bacteria contain what 2 sugars? What linkage?
GlcNAc and MurNAc
| - B(1->4)
59
Where is chitin found
Insect exoskeletons, crustacean shells, fungal cell walls
60
How does the structures of starch and glycogen and cellulose differ
- Starch & glycogen coil spontaneously into loose helices but structure not highly ordered cause numerous side chains of amylopectin and glycogen
- Cellulose forms rigid, linear rods. These aggregate into microfibrils & when combined w/other polymers in cell wall like pectin and protein extensin, resemble "reinforced concrete"
61
Why are lipids not true polymers?
Not built up of monomeric subunits so not polymerized
62
Why are lipids still considered macromolecules?
Large MW and association w/other macromolecules
63
What are the main storage lipids
Triacylglycerols
64
What are the main constituents of membranes
Phospholipids
65
What is the role of sphingolipids
Plays roles in cellular recognition
66
Fxn of cholesterol
Both a membrane lipid & precursor for steroid hormones (in animal cells)
67
What lipids are biologically active?
- Lipid soluble vitamins A, D, E, K
| - smaller amounts than storage or structural
68
Fxn of biologically active lipids
- Carry signals from cell to cell & from tissue to tissue
69
Characteristic of lipids
Low solubility in water, relatively hydrophobic
70
Biological fxns of lipids?
Storage of energy: reduced compounds, lots of available energy
Hydrophobic nature: good packing
Insolation from environment:
- low thermal conductivity
- high heat capacity (can “absorb” heat)
- mechanical protection (can absorb shocks)
Water repellant:
- keep surface of organisms dry, prevent
excessive wetting (birds), prevent loss of water via evaporation
Provide membrane structure
Cofactors for enzymes (e.g., vitamin K for blood clot formation; coenzyme Q for ATP synthesis in mitochondria)
Signaling molecules (e.g., steroid hormones)
Pigments (colour of tomatoes, carrots, etc.)
Antioxidants (e.g., vitamin E)
71
How are lipids classified?
- based on structure & fxn
- lipids that contain fatty acids and lipids that do not
- lipids that contain fatty acids can be further separated into storage lipids and membrane lipids
72
What characteristics of fatty acids
- carboxylic acids w/CH chains 4-36 carbons
- most natural FA's have even $ of carbons
- most natural FA's unbranched
73
What are saturated FA's
no DB's btwn carbons in chain
74
What are omega-3 fatty acids
- essential nutrients
| - humans cannot synthesize inc ALA, DHA, and EPA
75
Which (saturated or unsaturated) FA's has DB's that is rigid and creates kink in chain
unsaturated
76
The double bonds in natural unsaturated fatty acids are commonly in __ confirmation, which kinks the chain
cis
77
Saturated fatty acids pack in a fairly orderly way due to _____ (e.g., van der Waals)
extensive favourable interactions
78
Unsaturated cis fatty acids pack less evenly due to the ___ (less extensive favourable interactions)
kinks
79
It takes ___ thermal energy to disrupt disordered/kinky packing of unsaturated fatty acids: ____ melting point
- less
| - lower melting point
80
Solubility of fatty acids _________ as the chain length increases
decreases?
81
Melting point decreases as the chain length __________ and
| the # of double bounds ____________
- decreases
| - increases
82
How are trans fatty acids formed
Partial hydrogenation of unsaturated FA's to reduce # of cis bonds
83
Purpose to hydrogenation
Inc shelf life or stability at high temps of oils in cooking
84
A ___ double bond allows a given fatty acid to adopt an extended (___) confirmation
- trans
| - less kinky than cis
85
Consuming trans fats increases risk of?
Cardiovascular disease
86
Majority of fatty acids in biological systems are found in the form of
___
triacylglycerols
87
How many ester linkages in triacylglycerol
3 ester linkages
88
Solid triacylglycerols are called? Liquid?
```
Solid = fat
Liquid = oil
```
89
The primary storage form of lipids (body fat) is in the ___ tissue
adipose
90
TAGs are less soluble in water than fatty acids due to
the lack of charged
| carboxylate group
91
TAG are ___ dense than water
less (fats and oils float)
92
Fatty acids carry more energy per carbon
| than polysaccharides because they are more ___
reduced
93
Difference btwn glucose/glycogen and fats for energy needs?
- Glucose/glycogen for short-term energy needs, quick delivery
- fats for long-term energy needs, slow delivery
94
The number of adipocytes increases most rapidly
| during what period of your life
late childhood and early adolescence
95
With fat loss, adipocytes shrink in size or number?
Shrink in size, never number
96
Membrane lipids contain ___ head groups and
___ tails (usually attached
fatty acids)
- polar
| - non polar tails
97
Membrane lipids diversification can come from? (3)
- modifying the backbone
- changing the fatty acids
- modifying the head groups
98
What determine the surface properties
| of membrane
properties of head group
99
All organisms have same membrane lipid head group composition? T or F
False
| Dif organisms have dif membrane lipid head group compositions
100
All tissues have the same membrane lipid head group compositions
False
| Diff tissues have dif membrane lipid head group compositions
101
In water, lipids can form what 2 shapes?
- surface film or spherical micelle
102
Lipid derivatives can form larger aggregates held together by ____ forces
hydrophobic
103
___ form large spherical fat droplets in cell cytoplasm
Triacylglycerols
104
____ and ____ form self-sealing lipid bi-layers, which are the basis for cell membranes
phospholipids and glycolipids
105
Lipid structures formed in water depend on what 2 things
- type of lipid
| - concentration
106
How many AA's present in a cell at a given time? How many build up protein? What confirmation are they all in?
- 60
- 20
- L
107
What bond dictates final folding?
Non-covalent bonds
108
Can domains be separated from one another
yes
109
Similarity btwn DNA and RNA
both directional (5' -> 3') and antiparallel
110
Most naturally occurring sugars are __ isomers
D
111
Why can't disaccharides directly enter cells
Membrane is impermeable to disaccharides. There is not channels or carriers that take them up.
112
Which TEM would show a lactose intolerant person
Whichever image shows lactase enzyme being less dark and dense
113
Storage polysaccharides have __ links
alpha links
114
How do mammals digest cellulose
Microflora and rumination
115
Is b-D-gluose or a-D-glucose more stable
b-d-glucose cause no branching = more stable
116
Is chitin heteropolysaccharie or homopolysaccharide
homopolysaccharide
117
Alkyl chain emphasized on what molecule
Steriod
118
What kind of lipid does not have fatty acids
Archaebacterial ether lipids
119
why dont archaebacterial ether lipids have fatty acids
can survive high temps so membranes need to be more protected
120
are storage lipids polar or neutral
neutral (aggregate for storage)
121
are membrane lipids polar or neutral
polar
122
What would happen if FA became part of lipid bilayer
Saturated FA are very straight and packed together tightly so membrane becomes more stable
123
Why is it membranes are bad when liquid
leaky liquid anything can go in
124
Trans conformation looks similar to what FA's? Allows for what kind of packing
saturated FA's, more tightly packed
125
Charge of triacylglycerol?
Neutral
126
Main fxn of triacylglycerol
storage
127
How many FA in TAG
3
128
If u have a fatty acid w/just 1 hydrophobic tail what till it aggregate to
micelle
129
individual unit of micelle is what shape
conical
130
individual unit of bilayer is what shape
cylindrical
131
3 main types of lipids found in membranes
- phosphoglycerides
- sphingolipids
- steroids
132
What is the primary constituents of cell membranes
phosphoglycerides
133
Phosphoglycerides characteristic
Two fatty acids form ester linkages with the first and second hydroxyl of glycerol-3-phosphate
The highly polar phosphate group may be further esterified through a phosphodiester bond to a head group (R)
134
How are phosphoglycerides classified
by their head group
135
The backbone of sphingolipids is NOT glycerol but a long-chain amino alcohol ____
sphingosine
136
A fatty acid is joined to sphingosine
via an ___ linkage rather than an ester linkage usually seen
in lipids
amide
137
A polar head group is connected to sphingosine by a ____ or ___ linkage
glycosidic or phoshodiester
138
The sugar-containing glycosphingolipids are found largely where
in the outer face of plasma membranes
139
Fxn of sphingolipids
structure and cell signaling
140
What is the steroid nucleus made of
4 fused rings, hydroxyl group (polar head) in A-ring, various nonpolar side chains
141
Fxn of cholesterol and related steroids in membranes
- modulate fluidity and permeability
| - thicken the plasma membrane
142
How do mammals obtain cholesterol
From food or synthesize de novo in the liver
143
How is cholesterol transported
bound to proteins, is transported via blood vessels in low-density lipoproteins (LDL)
- tends to deposit in and clog arteries
144
What is the precursor to steroids
cholesterol
145
What causes cholesterol to precipitate
If the phospholipid: cholesterol ratio is 1:1, cholesterol is in effect soluble in the phospholipids
If the ratio is higher than 1:1, cholesterol will come out of solution and crystallize
146
Do steroid hormones have alkyl chain found in cholesterol?
no
147
Are steroids or cholesterol more polar
steroids
148
how are steroid hormones synthesized
from cholesterol in gonads and adrenal glands
149
how are steroid hormones transported
carried in bloodstream by carrier proteins
150
What are terpenes (class of lipids) formed from
5 carbon isoprene is fundamental building block
151
What is the precursor of cholesterol
isoprene
