Midterm 1 Flashcards
(231 cards)
1
Q
Proteins are ____, synthesized in ___ to a current need, _____ to an appropriate cellular location / target and then ____.
A
specific
response
transported
degraded
2
Q
Between Bacteria and Eukaryotes:
Basic components/mechanisms utilized by the protein biosynthetic pathway is…
A
remarkably well preserved
3
Q
The resource demands to synthesize proteins are significant. Production can account for __% energy used for biosynthesis.
A
90%
4
Q
___ ribosomes, ____ molecules of protein synthesis related factors and enzymes, ____ tRNA molecules in a typical bacteria cell can account for __% of the cells dry weight
A
15,000 ribosomes
100,000 molecules of protein synthesis related factors & enzymes
200,000 tRNA molecules in typical bacteria cell wall
35%
5
Q
Life depends upon the …(1)
and the… (2)
A
(1) information flow within a cell
(2) and the ability to change genetic information into functional proteins
6
Q
Life depends upon the information flow within a cell and the ability to change genetic information into functional proteins. This is referred to as the?
A
central dogma (principle) of biochemistry
7
Q
the central dogma (principle) of biochemistry consists of two inter-related processes:
A
transcription and translation
8
Q
Although there are differences in the processes in eukaryotic as opposed to prokaryotic cells, the flow of information and the basic steps of transcription and translation are ___.
A
identical
9
Q
common ___ and ___. This is a central feature of life.
A
components and mechanisms
10
Q
Replication
A
The DNA transmits information in a process
that involves many enzymes
11
Q
During transcription
A
DNA codes for the production of messenger RNA (mRNA) in 3 processes
12
Q
3 Processes of Transcription
A
initiation, elongation and termination
13
Q
In eukaryotic cells, the mRNA is processed and migrates from the…to the..
A
nucleus to the cytoplasm
14
Q
mRNA carries coded information to where? what do they do with this info?
A
ribosomes that “read” this information for protein.
15
Q
Do proteins code for production of protein, DNA or RNA?
A
No, but they do help in theses processes.
16
Q
Proteins are involved in almost all biological activities, __ or __.
A
structural or enzymatic
17
Q
The Origin of Life’ (3)
A
- (Bio)chemical evolution
- Self organization
- Biological evolution
18
Q
All life is composed of macromolecules made of the same …
A
30-40 molecules.
19
Q
Alkeksandr Oparin’s Hypothesis
environment
energy
accumulated into..
formed?
A
In an atmosphere made of methane, ammonia gases and water vapour (reducing environment), Lightning, heat from volcanoes or thermal vents caused reactions that would form organic compounds
These compounds accumulated in a “soup”, which may have been concentrated at various locations (seas)
Some would have a greater tendency to associate into larger complexes, and certain materials (i.e. clay) would facilitate.
Polymerization (joining together of small subunits).
Just add time.. spontaneous formation of membranes and catalysts
20
Q
How old is Earth?
A
4.54 billion years old
21
Q
Archeologists estimate modern humans have been on the Earth for about ____ years.
A
200,000
22
Q
Aleksandr Oparin showed how organic chemicals in solution may ..(1)
and outlined a way in which basic organic chemicals might form into (2) __ ___ __ (possible precursors of cells) from which …(3)
A
(1) spontaneously form droplets and layers
(2) microscopic localized systems
(3) primitive living things could develop.
23
Q
Oparin suggested that different types of coacervates (tiny droplet of assorted organic molecules) might have formed in the Earth’s primordial ocean and subsequently, been subject to a … eventually leading to…
A
selection process, eventually leading to life.
24
Q
Who tested Oparin’s theory?
A
Harold Urey and Stanley Miller
25
Urey's and Miller's experiment established the possibility of ..
abiotic production of biomolecules in relatively short periods of time under relatively mild conditions.
26
With CO2, CO, N2 and H2 in the atmosphere, scientists have shown the...
production of hundreds of organic molecules (carboxylic acids, nucleic acids, amino acids and sugars).
27
Polymerization reactions are enhanced by ...
inorganic ions (Cu2+, Ni2+, Zn2+) and other molecules.
28
RNA could have been the preliminary catalyst (enzyme) and information storage molecule (gene), where protein and DNA originated later.
RNA - first catalyst and gene
29
Origin of Life: Self Organization (6)
```
1) Chemical complexity and organization
(not just simple components)
2) Extract, transform, use energy
(from environment --> storage molecules)
3) Self-replication and assembly
(genetic material contains info)
4) Adaptation
5) Functions of components are defined and regulated
```
30
Margulis's Hypothesis:
Endosymbiosis
early eukaryotic cells which were incapable of photosynthesis or aerobic metabolism, enveloped aerobic bacteria or photosynthetic bacteria to form endosymbiotic associations that eventually become permanent
31
Endosymbiosis
• Anerobic metabolism
- Bacterial Genome engulfed
• Symbiotic system an aerobic metabolism
• Cyanobacterial genome engulfed leading to the development of a chloroplast – a photosynthetic eukaryote
32
Life is based on morphological units called ___.
cells
33
Prokaryotes
| -what kind of organisms
bacteria
34
Prokaryotes
lack?
simple structures (3)
membrane-enclosed nucleus
| unicellular, filaments or colonies
35
Prokaryotes
| cell wall
polysaccharides, peptidoglycans
36
Prokaryotes & Eukaryotes
| cell membrane
lipid bilayer with protein
37
Prokaryotes
| DNA?
one or more copy of chromosome in condensed form (nucleoid)
38
Eukaryotes
| DNA
membrane enclosed nucleus contains DNA
| WAY more DNA than prokaryotes
39
Eukaryotes
| growth form?
unicellular or multicellular
40
Cell (Plasma) Membrane contains (2)
transporters, signal receptors
41
Cell (Plasma) Membrane engulfs particles by (3)
endo, phago and exocytosis
42
Cell Wall is found in ___
| made up of?
Plants
| cellulose and other carbohydrate polymers
43
Starting point for growth or development, kernel of a cell.
Nucleus
44
How does the Nucleus store genetic info?
chromosomes
45
Chromosomes consist of?
chromatin fibers made of nucleosomes (DNA + histones)
46
Nuclear Envelope
double membrane bilayer, perforated with many pores to allow passage of macromolecules (enzymes in, mRNA and protein out)
47
Nucleolus
site of..
contains...
site of ribosomal assembly (exported to cytosol by exocytosis)
contains chromosomal segments with multiple copies of genes to code ribosomal RNA.
48
Cytosol
| __ based
water based
49
Cytosol
(1) INCLUDES?
(2) EXCLUDES?
1) macromolecules
| 2) membrane bound organelles, cytoskeleton
50
Endoplasmic Reticulum is the..
most extensive membrane in cell
51
Rough ER
| function?
ribosome studded, protein synthesis
52
Smooth ER
| function?
no ribosomes, lipid synthesis
53
Golgi Apparatus
| Golgi is?
stack of flattened membranous sacs (cisternae)
54
Where are the vesicles form the ER transported to?
transported to Golgi
55
Macromolecules synthesized by smooth and rough ER are...
“addressed” by modifying enzymes, sorted, and packaged for secretion (exocytosis) or use within the cell.
56
Mitochondria likely evolved from?
aerobic bacteria
57
Mitochondria is the site of...
cellular respiration
58
Mitochondria has two ...
lipid membranes
| smooth outer and highly folded inner w/ invaginations called cristae
59
Mitochondria has two spaces
inner membrane space & matrix internal space
60
Mitochondria reproduce by?
fission (like bacteria) only from other mitochondria
61
Mitochondria
| What forms gel-like matrix of inner mitochondrial membrane?
Respiratory Enzymes
62
Mitochondria
| What do these respiratory enzymes do?
couples chemical energy from nutrient oxidation to synthesis of ATP (energy storage molecule)
63
Mitochondria
| ATP synthesized by coupling reaction (chem e from nutrient oxidation) is exported where?
to rest of cell to fuel processes
64
Mitochondria is somewhat self sufficient because?
contains DNA, RNA and ribosomes for the synthesis of mitochondrial components
65
Chloroplasts contain
chlorophyll
66
Chloroplasts reproduce by?
fission like mitochondria but uses solar energy
67
Photosynthetic by-product of ATP is?
O2
68
Chloroplasts
| Thylakoids
contain pigments that absorb light
69
chloroplasts likely evolved from?
cyanobacteria
70
Lysosomes
membraneous sacs containing a
large variety of low pH hydrolytic enzymes that digest molecules
plants contain analogous vacuoles
71
Peroxisomes
| site of?
site of breakdown of amino acids and fats, leading to the production of free radicals and
H2O2
catalase: 2H2O2 -> 2H2O + O2
72
• some plants contain specialized peroxisomes
Glyoxysomes – site of a series of Rxs collectively called the glyoxylate metabolic pathway
73
Cytoskeleton function
- organizes, adds structure to the cytosol, but not part of it
- gives cell shape and ability to move
- orchestrates internal motion of
organelles
74
Cytoskeleton structure
extensive array of filaments (actin, intermediate) and microtubules (that make up centrioles)
75
Chromatin -> ___-> ___
DNA -> Nucleotides
76
Plasma Membrane -> ___-> ___
protein -> amino acids
77
Cell wall -> ___-> ___
lipids, cellulose -> sugars
78
Viruses vs Virions
cellular parasite vs inactive
79
Viruses are ___ than cells
simpler
80
How are viruses simpler than cells?
DNA/RNA in protein (sometimes with lipid) coat
81
How do viruses replicate?
by hijacking the host cell machinery
82
Prions were originally thought to be a?
| but now evidence shows that they are just a?
virus
| mis-folded protein
83
Amphipathic
having both hydrophobic and hydrophilic parts
84
water has __% ionic character
33%
85
H2O is highly __ with a net ___
polar
| dipole
86
Which are Stronger?
| H-bonds or covalent bonds?
Covalent bonds
87
H2O is a good solvent for ?
| such as?
polar and ionic material
| - salts, small polar molecules ( aa's, sugars, nucleic acids) and exterior or proteins
88
Solubility in WATER enhanced for molecules that
can form hydrogen bonds (H-bonds)
| i.e. hydroxy, keto, carboxy, amino groups, and these are termed hydrophilic (water loving) groups
89
Solubility reduced for molecules that
can not form H-bonds
i.e. hydrocarbons such as alkanes(C(n)H(n+2), alkenesC(n)H(2n), and these are termed hydrophobic (water fearing) compounds
90
C vs H electronegativity
C is only slightly more EN than H
91
H bonds vs dipole-dipole forces
Hydrogen bonds are 10-20 times stronger than other dipole-dipole forces.
92
Molecules with H bonds
| bp & mp
have unusually high bp and mp
| greater internal cohesion
93
Entropy ___ as crystalline substances dissolve
increases
94
Why does Entropy increase as crystalline substance dissolves?
as a salt dissolves, ions leave crystal lattice structure acquiring greater freedom of motion
95
Micelles
stable structure of amphipathic compounds
96
Enzyme Substrate Interactions in Water
Enzyme-substrate interaction displaces ordered water.
Interaction is stabilized by h-bonding, ionic, and hydrophobic interactions
Binding of substrate to enzyme releases ordered water
97
can water be part of a proteins structure?
YES
98
Cells often require a strongly controlled environment:
| Sites of Control (3)
1) Organelles/Membranes
(compartments with barriers to limit movement to and from)
a) protein pumps
b) pores
2) Aqueous properties (pH)
3) Cell membrane environment (affects membrane proteins)
99
water hydrates the hydrophilic portion but excludes the hydrophobic region to give (2)
micelles and lipid bilayers
100
hydration of hydrophilic portion and exclusion of hydrophobic region produces micelles and lipid bilayers in a process that...
reduces entropy (↓ S) or increases the order of
the lipid system,
BUT
increases entropy of surrounding water (basis of cell membranes)
101
Osmosis
water moves from a region of high to low water concentration
102
Units of π
atm
103
van't Hoff Equation
π = icRT
i - van't Hoff factor
c - molar concentration of solute (M)
R - gas constant (0.08206 L atm/K mol)
T - absolute temperature (K)
104
Water moves fairly freely across the cell membrane by means of
aquaporins
105
Not all molecules can cross the membrane because
membrane is semi-permeable
106
If osmolarity of solutions on either side of a membrane are equal, they are called ...
isotonic
107
higher osmolarity than that of the cell
hypertonic solution
108
lower osmolarity than that of the cell
hypotonic solution
109
Examples of Osmosis
1) fresh water fish in salt water
2) a cell in distilled water
3) blood
4) bacteria & salt
5) wilted lettuce
110
Principle of Electroneutrality:
any macroscopic region of a solution must have equal positive and negative charges
111
The cytoplasm contains which __1__ that can not permeate the plasma membrane
- The cytoplasm also contains __2__ to which the plasma membrane is semi-permeable
1) proteins, organic polyphosphates etc.
| 2) cations (Na+, K+, Cl-, etc.)
112
the greater the charge concentration of protein...
the more unequal the final distribution of diffusible ion.
113
Ionization of Water
```
Slight tendency of H2O to undergo reversible ionization"
hydrogen ion (proton) and hydroxide ion
```
114
At 25˚C, [H2O] is?
55.5 M
115
Equilibrium constant for water
Keq = [H+][OH-]/[H2O]
116
```
Kw = ? at 25˚C
Keq = 1.8 x 10-16 M
```
Kw = Keq x [H2O]
= (55.5 M)(1.8x10^-16)
= 1.0 x 10^-14 M2
117
At neutral pH at 25˚C [H+] and [OH-]
are equal
118
pH = ?
log 1/[H+] = -log [H+]
119
neutral pH
basic pH
acidic pH
pH = 7
pH > 7
pH < 7
120
The pH of blood is normally kept within ...
| Outside the narrow range...
7.35-7.45
| the organism can not function.
121
The pH of the cytosol of most cells is ___
however, in lysosomal organelles the pH is ___
How come?
~ 7.4
~ 5.0
This is the pH at which the degradative enzymes (proteases) of the lysosome function best, and they are actually inactive at cytosolic pH!
122
What are BUFFERS used for?
used to control the pH within a system
123
What are Buffers?
Buffers are weak acids or bases that react with acid or base such that even relatively large additions of an acid or base do not lead to large changes in pH
124
When acid is added to water..
it dissociates to the hydronium ion (H3O+) and a conjugate base (A-):
125
The strength of an acid is determined by
the degree of dissociation;
large – strong
small – weak
126
In dilute solutions, [H2O] is essentially constant (55.5 M); therefore the term [H2O] can be ...
combined with the dissociation constant as follows:
Ka = Keq [H2O] = [H+][A-]/[HA]
127
pKa
= -log Ka
128
lower values of pKa
| higher values of pKa
stronger acid
| weaker acid
129
Ka = ?
= [H+][A-]/[HA]
130
The __ of a solution, and the ___ of an acid and its conjugate base are related by the H-H equation
pH
| concentration
131
The Henderson-Hasselbalch (H-H) Equation
pH = pKa + log[A-]/[HA]
132
when the molar concentration of an acid (HA) and its conjugate base (A-) are equal...
[A-]/[HA] = __
and log[A-]/[HA] = __
1
log1 = 0
So the pH of the solution simply equals the pKa of the acid.
133
pH midpoint of titration =
pKa of corresponding acid [HA] = [A-]
134
Slope lower near midpoint when [HA] ≈ [A-] because?
pH is relatively insensitive to addition of strong acid or base i.e. buffered solution
135
Buffered solution is maximal when?
pH = pKa
| useful range is within 1 pH unit of its pKa
136
Polyprotic Acids
Substances that have more than one acid/base group
137
Blood plasma is buffered in part by which system?
bicarbonate system
138
Bicarbonate Buffer System consists of?
Carbonic Acid H2CO3 as H+ donor
| Bicarbonate HCO3- as H+ acceptor
139
the pH of this bicarbonate buffer system depends on?
concentrations of H2CO3 and HCO3-
[H2CO3] depends on [CO2(d)] which in turn depends on [CO2(g)] (or partial pressure of CO2)
thus the pH of bicarbonate buffer exposed to gas phase is ultimately determined by [HCO3-] and by pCO2
140
Bicarbonate Buffer System is an effective physiological buffer near what pH?
7.4
141
Blood can pick up H+ from?
lactic acid produced n muscle tissue during vigorous exercise
142
Blood can lose H+ from?
protonation of NH3 produced during protein catabolism
143
pH optimum of an enzyme
maximal catalytic activity at a characteristic pH
144
The chemical properties of compounds are determined by:
chemistry of its functional group
| 3D placement in space
145
C-C bond characteristics
free rotation
146
C=C bond characteristics
forms a planar structure
147
C≡C bond characteristics
like a single bond
cylindrically symmetrical
allows for free rotation
148
Bulk Elements
H, Na, K, Ca, C, N, O, P, S, Cl
149
Amino Acid Function
Chemical Messengers
| Inhibitory/Excitatory Neurotransmitters
150
Inhibitory Neurotransmitters
(2) examples
both involve?
Glycine & Gamma-aminobutyric acid (GABA)
| both involve Cl- release
151
Glycine
function
involved in?
binds receptor that opens Cl- channel and makes synapse membrane less likely to depolarize
involved in motor and sensory functions
152
GABA
glutamic acid derivative also opens Cl- channel
most common neurotransmitter in brain
altered levels in Huntington's disease
153
Excitatory Neurotransmitters (3)
```
Glutamic acid and Aspartic acid
Derivatives of amino acids
- Epinephrine and norepinephrine are derived from Tyrosine
- can focus attention (AKA adrenaline)
– similar to amphetamines
```
154
Amino Acid Derived Molecules (3)
Histamine
Creatine and phosphocreatine
Nitrous Oxide
155
Histamine
– Histidine decarboxylation produces this powerful vasodilator.
Part of the allergic response and controls stomach acid release.
156
Creatine and phosphocreatine
Glycine and Arginine combine to produce this energy buffering system
157
Nitrous Oxide
Arginine is a precursor of this biological messenger
158
The “standard” amino acids are ...
α-amino acids
159
these α-amino acids
- primary amino (amino) group (-NH2)
| - carboxylic acid (carboxyl) group (-COOH)
160
Which amino acid is an exception but still referred to as an α-amino acid?
Proline because it has a secondary amino group
161
Amino acids at pH 7 exist in what form?
a zwitterionic, charged form.
162
All amino acids have chiral centers except?
Glycine (two H groups)
163
Amino acid carbons
| are named in sequence using the Greek alphabet (alpha, beta, gamma, delta, epsilon) starting where?
the carbon between the carboxy and amino groups
164
Configuration
A fixed spatial arrangement of atoms in an organic molecule that is created either by a double bond or a chiral center, about which groups are arranged in a specific sequence
165
Conformation
spatial arrangement of atoms that arise as a result of free bond rotation
166
Chiral molecule
a molecule that can NOT be superimposed on its mirror-image
167
R & S Designation
1) rank atoms around chiral center by atomic number (W > X > Y > Z)
2) if identical move one atom out
3) chiral center is viewed from center towards Z group ( Z behind chiral center)
Clockwise - R
counterclockwise - S
168
isoelectric point (pl)
pH at which a molecule’s net charge is zero
169
pKa of amino group
| pKa of carboxylic group
9. 4
| 2. 2
170
Proteins are made from amino acids, but first:
DNA must be transcribed to make messenger RNA (mRNA)
171
mRNA contains many ___, each codes for ?
codons
| one of the 20 amino acids
172
DNA strand is _'->_'
| RNA strand is _'->_'
DNA: 3'-5'
RNA: 5'-3'
173
Translation in Eukaryotes
mRNA is transported where? to become associated with?
In eukaryotes, mRNA is transported to the cytosol to become associated with a ribosome (ribosomal RNA (rRNA) + protein)
The ribosome associates w/ transfer RNA (tRNA) that reads mRNA code
- each tRNA recognizes only one codon and carries a single amino acid
174
Which Amino Acids have more than one chiral center?
Threonine
| Isoleucine
175
Synthesis - Amino Acid Delivery
Each tRNA delivers an amino acid that will be coupled to the growing protein by the ribosome
176
One end of the tRNA is called ...
| the other end of the tRNA has the?
the acceptor stem that carries the amino acid to be coupled (via high E bond)
anticodon - 3 bases that are complementary to the mRNA codon
177
mRNA contains many ___, each codes for ?
codons
| one of the 20 amino acids
178
DNA strand is _'->_'
| RNA strand is _'->_'
DNA: 3'-5'
RNA: 5'-3'
179
Translation in Eukaryotes
mRNA is transported where? to become associated with?
In eukaryotes, mRNA is transported to the cytosol to become associated with a ribosome (ribosomal RNA (rRNA) + protein)
The ribosome associates w/ transfer RNA (tRNA) that reads mRNA code
- each tRNA recognizes only one codon and carries a single amino acid
180
Which Amino Acids have more than one chiral center?
Threonine
| Isoleucine
181
Synthesis - Amino Acid Delivery
Each tRNA delivers an amino acid that will be coupled to the growing protein by the ribosome
182
Protein Synthesis
40S and 60S ribosomal subunits bind to mRNA, and move along it, catalyzing the joining together of amino acids through peptide (amide) bonds
183
Peptide bond:
the linkage between two amino acids
184
Condensation Reaction
water is eliminated (amide linkage or
| amide bond)
185
The peptide C-N is shorter than an amine’s C-N bond which indicates?
This indicates a resonance, or sharing of electrons
186
The peptidyl C-N linkage and the four atoms to which the C and N are directly linked always form a ___ structure as result of the ?
planar
| partial double bond character
187
The peptide back bone of a protein can be described structurally as a ?
series of planes
188
Sequence
Covalent Linkages
189
Peptides are named from the ___ end to the __ end
amine end to the carboxyl end
190
Oligopeptide:
a few amino acids linked together (~ 10-30)
191
Polypeptide:
many amino acids linked together (~30-90)
192
Protein:
can contain thousands of amino acids (> 90)
193
2ndary Structure
Regular Backbone Structure
conformations within regions of the
protein principally based on hydrogen bonding
194
Tertiary Structure
overall protein structure (3D)
195
Quaternary structure
association of separate peptidyl chains
196
The sequence of a protein is simply its...
amino acid sequence.
197
Proteins are not straight lines, but
fold into structures almost immediately amer (and during) synthesis (some require help)
198
α-Keratins
part of a broader family of proteins (intermediate filaments)
- play structural role within cell
in hair, claws, horns, outer skin layer
forms a coiled coil
199
α-helix
The polypeptide backbone is wound around an imaginary axis with the R groups protruding outwards
200
How many amino acids per helical turn?
3.6
201
Certain amino acids destabilize a helix
1. long blocks of Glu, Lys, Arg
2. bulky side chains (Asn, Ser, The, Leu) if close together in sequence
3. Pro (too rigid) and Gly (too flexible)
202
α-Keratins
part of a broader family of proteins (intermediate filaments)
- play structural role within cell
in hair, claws, horns, outer skin layer
203
Collagen
```
evolved to provide strength
found in connective tissue, tendoms
3 helices coiled around one another
3 aa / turn
left handed
```
204
β-Sheet
has h bonding like α-helices but between chains rather than within one chain
contains at least 2 strands (~6 strands/sheet
205
2 varieties of β-Sheets
Parallel and Anti-parallel
206
Antiparallel vs Parallel
Antiparallel more stable as a result of H-bonds
| Parallel less stable as a result of H-bond distortion
207
Tertiary (3°) structure:
three dimensional arrangement, or, folding of the secondary structural elements
208
Forces that influence folding (usually all are optimized:
```
1
2 a,b
3
4 a,b,c
5
```
1. Disulfide bridges
2. Hydrophilic
a) Ionic interactions (full charge interactions)
b) Hydrogen bonding (partial charge interactions)
3. Hydrophobic
4. Van der Waals forces – weak dipole attraction Van der Waals contact: repulsion = attraction
a) permanent dipoles
b) dipole-induced dipole
c) London Dispersion Forces (induced-induced)
5. Metal chelation
209
Which amino acids will contribute to:
| 1. Disulfide bridges?
Cys side chain
210
Which amino acids will contribute to
| 2. Ionic interactions?
(+) : Arg, Lys, His side chains
| (-) : Asp, Glu
211
Which amino acids will contribute to
| 3. Hydrogen bonding?
protein backbone amide C=O and amide N-H
Ser, Thr, Cys, Asn, Gln, Trp, Tyr side chains along with side chains of fully charged groups
other atom not involved with ionic interaction can form H bonds
212
Which amino acids will contribute to
| 4. Hydrophobic interactions?
Gly, Ala, Val, Leu, Met, Ile, Phe side chains
| proline with its restricting structure is often on outside turns
213
Motifs are
made up of secondary structures and are found in many structures
214
Smaller motifs can...
can contribute to larger ones
215
Domains are often a....
| often made from?
stable portion of 3° structure
| two or more covalently linked motifs
216
Proteins and Domains
Proteins can consist of one or more domains linked as one polypeptide unit, each being structurally independent with the characteristics of a small globular protein
217
What make a large contribution to stability in peptides?
hydrophobic interactions
218
α helices and β sheets are generally found in together in one protein but?
in different structural layers
219
Segments adjacent to each other in the amino acid sequence are usually ?
stacked together in the folded structure.
220
When is the β conformation most stable ?
when the individual segments twist slightly in the right handed sense.
221
The spatial arrangement of the subunits is called
| the?
quaternary structure
222
Binding curve for O2 to hemoglobin is?
| Function?
sigmoidal or cooperative
Function: in the tissues, O2 must be delivered, whereas in the lungs, O2 must be taken up.
223
Cooperative binding facilitates...
hemoglobins ability to bind successive oxygens
| makes hemoglobin much more sensitive to [O2]changes
224
Protein Functions in Transport
Myoglobin & Haemoglobin
myoglobin transports and stores oxygen in muscle, haemoglobin transports oxygen and carbon dioxide (CO2) in the blood
225
Protein Function in Organized Movement and Structure
actin & myosin
Myofibrils: units of muscle composed of proteins
Tropomyosin & troponin - control the process
226
Protein Function in Immune response
antibodies, produced by B lymphocytes, recognize foreign macromolecules (antigens), for example viruses!

227
Protein Function: Enzymes
Enzymes: carry out various chemical reac@ons within an organism
228
Opioid Receptors:
bind morphine (analgesia), heroin (addiction), enkephalin, endorphin (runner’s high) that cause various effects in the body ...
229
Protein Function: Ribonuclease
Ribonuclease chops up ribonucleic acids in ingested food (pancreas/intestine)
230
Receptors:
bind to specific molecules (messengers) and allows signals from the outside of the cell to be transferred to the inside of the cell
231
Receptor Exampel
An example is a G-coupled protein receptor such as the human opioid receptor that is involved in pain/ analgesia, emotions and addiction.
