Chapter 6 - Structure and Function in Cells and Viruses Flashcards
1
Q
Summarize the events in zygotene
A
- homologous chromosomes pair up (synapsis) in preparation for crossing-over (genetic recombination)
- the synaptonemal complex (RNA scaffold) appears between the pairing chromosomes and facilitates their union
2
Q
1-letter abbreviation of isoleucine
A
I
3
Q
Equation: isoelectric point (pI)
A
pI = [pKa1 + pKa2]/2
4
Q
What are 3 major groups added to C1 of phospholipids?
A
- phosphoethanolamine
- phosphocholine
- serine
5
Q
What is the beginning and end result of meiosis?
A
1 diploid cell makes 4 haploid cells
6
Q
In the titration of protonated glycine by a strong base, how does its charge change over time and which groups are changing?
A
pH < pKa α-COOH: +1 (fully protonated)
First midpoint: pH = pKa α-COOH: +0.5
Equivalence point: pH = pI (physiologic pH): 0
Second midpoint: pH = pKa α-NH3: -0.5
pH > pKa α-NH3: -1 (fully deprotonated)
7
Q
1-letter abbreviation of proline
A
P
8
Q
What is simple diffusion?
A
spontaneous movement of solute molecules through a lipid bilayer, from high to low concentration (down the concentration gradient)
9
Q
Cytosine structure
A
10
Q
Lysine structure
A
11
Q
In what direction do microfilaments grow (polymerize)? In what direction do they depolymerize?
A
They are polymerized fastest at the + end and depolymerize fastest at the - end.
12
Q
What is the purpose of the rough endoplasmic reticulum?
A
The bound ribosomes synthesize membrane and secretory proteins that are then passed through into the lumen where post-translational modification begins. Modified proteins are shuttled to the Golgi apparatus.
13
Q
What holds sister chromatids together?
A
centromere
14
Q
What are anomers?
A
carbohydrates that differ diastereomerically (α/β) at the anomeric (C1) carbon
15
Q
How do proteins get into the nucleus from the cytoplasm?
A
through nuclear pores that span the inner and outer membranes
16
Q
What is nucleoplasm?
A
the mixture of chromatin and the aquous phase of the nucleus
17
Q
What is the secondary structure of a polypeptide?
A
spatial arrangement of amino acids that are close to one another (β-pleated sheets and α-helices)
18
Q
3-letter abbreviation of glycine
A
Gly
19
Q
3-letter abbreviation of threonine
A
Thr
20
Q
What is the general function of progesterone?
A
It prepares the uterine lining for implantation of an ovum and maintains it if implantation occurs.
21
Q
What are bivalent chromosomes? Tetrads?
A
Those that have undergone synapsis in meiosis because there are four chromatids. The paired homologous chromosomes are also called tetrads.
22
Q
In order for an organism to reproduce asexually, should it be diploid or haploid?
A
either
23
Q
Alanine structure
A
24
Q
Acrocentric chromatids
A
25
Summarize the events in Meiosis II: Telophase II
- nuclear membrane forms
- chromosomes decondense
- cleavage furrow of cytokinesis deepens
26
What are the two major types of bulk transport?
- endocytosis
- exocytosis
27
What are peripheral membrane proteins?
proteins weakly attached to the surface of the lipid bilayer
28
Summarize the events during anaphase
- centromeres aligned at the metaphase plate divide and the two sister chromatids can now be called daughter chromosomes, and move toward opposite poles
- microtubules exhibit **depolymerization** at the kinetochore
- cytokinesis begins (cleavage into two daughter cells)
- the cell is 4n
29
What is the difference between pyranose and furanose?
pyranose: 6-membered cyclic carbohydrate
furanose: 5-membered cyclic carbohydrate
30
What are the two structures of viruses?
- isometric
- helical
31
Describe prokaryotic DNA structure
double-stranded and circular
Bacteria sometimes have plasmids, which are also circular and double-stranded, but smaller
32
What are the convoluted foldings of mitochondria's inner membrane called?
cristae
33
What is the sedimentation coefficient of eukaryotic ribosomes? What about the large and small subunits?
80S
Large subunit: 60S
Small subunit: 40S
34
What are mesosomes?
invaginations of bacterial cell membranes
35
What is the pKa of aspartate's side chain?
3.9
36
1-letter abbreviation of methionine
M
37
Valine structure
38
What is chemotaxis?
attraction towards or repulsion away from certain chemicals (exhibited by bacteria)
39
Summarize the events during prophase
- centriole pairs begin to move apart and form **microtubules** that radiate from the **centrosome** or **microtubule organizing center/MTOC** (**aster** star)
- some microtubules attach at the **kinetochore** (near the centromere) of sister chromatids
- chromatin condensation is complete
- nucleolus disappears and nuclear membrane begins to break down
40
Fatty acid structure
carboxylic acids with a hydrocarbon side chain
41
Guanine structure
42
3-letter abbreviation of tryptophan
Trp
43
What are ampholytes?
amphoteric molecules that exist as zwitterions at physiological pH
44
What are nonhistones?
They are acidic proteins that bear a net negative charge and interact with DNA (ex: RNA polymerase)
45
3-letter abbreviation of valine
Val
46
1-letter abbreviation of serine
S
47
Summarize the events in diplotene
- crossing-over becomes visible at structures called **chiasmata** (single: **chiasma**)
48
What is the form of genetic information as a cell prepares for division?
chromosomes (highly condensed - visible)
49
In order for an organism to reproduce sexually, should it be diploid or haploid?
diploid
50
What is active transport? What are two types?
transportation of a solute from low to high concentration, requiring energy
- primary active transport
- secondary active transport
51
Which type of RNA helps define the site of protein synthesis?
ribosomal RNA (rRNA)
52
What is the general function of testosterone?
It aids in sperm maturation and development of secondary sex characteristics
53
What is the difference between an envoloped and non-enveloped virus?
An enveloped virus is surrounded by a lipid membrane that is attached to the nucleocapside by **matrix proteins**. A non-enveloped virus is not surrounded by a membrane (naked).
54
3-letter abbreivation of phenylalanine
Phe
55
56
Serine structure
57
What is primary active transport?
hydrolyzes ATP to ADP and Pi for energy to move molecules across their concentration gradients
58
What is the major reaction that takes place in the smooth endoplasmic reticulum of hepatocytes and what purpose does it serve?
hydroxylation, which aids in detoxifying drugs, making them more water soluble for elimination
59
What stabilizes β-pleated sheets in polypeptides?
hydrogen bonds between CO and NH groups of different polypeptide chains
60
What is a signal recognition particle?
It recognizes **signal sequences** in growing proteins, halts translation, and directs the ribosome to a **signal sequence receptor** on the rough ER. Translation restarts and the polypeptide is inserted into the ER lumen, where the signal sequence is removed by a **signal peptidase** and the polypeptide is modified.
61
What is the structure of microfilaments? What is their diameter? What are the main protein components?
- 7 nm
- G-actin monomers form F-actin polymer
62
3-letter abbreviation of arginine
Arg
63
What is the bond called between monosaccharides?
O-glycosidic linkage
64
Glutamine structure
65
Summarize the events in Meiosis II: Metaphase II
- chromosomes line up along the metaphase plate
66
How does a capsid differ from a nucleocapsid?
A capsid does not contain nucleic acid, so it is an empty shell. A nucleocapside contains nucleic acid.
67
Where is rRNA transcribed?
from specific genes of DNA within the nucleolus
68
How does salivary α-amylase break down starch? What about pancreatic α-amylase? What about intestinal enzymes?
Salivary α-amylase hydrolyzes many of the α(1--\>4) linkages, breaking it down into oligosaccharides.
Pancreatic α-amylase hydrolyzes more linkages, breaking down the oligosaccharides into di- and trisaccharides.
Intestinal enzymes break it down into monosaccharides to be absorbed by the intestinal epithelial cells and passed into the blood.
69
What are some biochemical reactions that occur in the mitochondrial matrix?
- Krebs cycle
- β-oxidation of fatty acids
- ketone body metabolism
- gluconeogenesis
- urea cycle reactions
70
3-letter abbreviation of glutamine
Gln
71
What are the purine bases?
- adenine
- guanine
72
What is passive transport? What are the two types?
movement of a molecule from high to low concentration
- simple diffusion
- facilitated diffusion
73
What generally happens during the synthetic (S) phase?
All 46 strands of chromatin are replicated to make 92 sister chromatids. Daughter centrioles are synthesized.
74
Methionine structure
75
Describe the structure of gram (-) bacteria and how it affects their gram stain result.
They have a thin **peptidoglycan** layer between their plasma membrane and **outer membrane**. The outer layer contains **lipopolysaccharides** and **porins**.
They stain red/pink.
76
How are lysosomal enzymes made?
Glycoproteins that come from the Golgi are inactive precursors (proenzymes) that undergo proteolytic cleavage in an acidic environment (the lysosome) to form active enzymes.
77
Summarize the events in Meiosis I: Cytokinesis
- 2n --\> n (**reductive division**)
78
What are the 4 phases of Meiosis I: Prophase I?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
79
What is the primary structure of a popypeptide?
the sequence of amino acids in a protein and location of disulfide bonds
80
Proline structure
81
1-letter abbreviation of leucine
L
82
What is the function phosphatase?
It hydrolyzes and removes phosphate groups from the substrate.
83
What is the form of genetic information in a nondividing (interphase) cell?
chromatin (not visible)
84
What is the purpose glycosidase?
It hydrolyzes and breaks down carbohydrates.
85
3-letter abbreviation of aspartate
Asp
86
1-letter abbreviation of tyrosine
Y
87
What is the major protein in mitochondria's outer membrane and what is its function?
porin - a transmembrane protein that allows various molecules through
88
Which type of RNA allows for the synthesis of proteins?
messenger RNA (mRNA)
89
Whats is a cystine?
Two cysteine residues that are part of a disulfide bond are oxidized (lose their H's).
90
Arginine structure
91
Equation: number of stereoisomers
2n
n = # of chiral centers
92
Summarize the events during metaphase
- chromosomes align at the equator of the cell (**metaphase plate**)
- nuclear membrane has completely disappeared
93
1-letter abbreviation of valine
V
94
Where are ribosomes found?
- cytoplasm
- rough ER
- mitochondrial matrix
95
What are the Tollens' and Benedict's reagents used for?
They test whether sugars are reducing sugars. They must contrain a hemiacetal or hemiketal group to give a positive test.
96
1-letter abbreviation of cysteine
C
97
Histidine structure
98
1-letter abbreviation of glutamine
Q
99
What is bacterial conjugation? What are the individuals involved called?
The transfer of DNA occurs through cell to cell contact between the donor (male/F+) and recipient (female/F-).
100
What is the function protease?
It hydrolyzes peptide bonds to break apart proteins.
101
Aspartate structure
102
1-letter abbreviation of aspartate
D
103
What group(s) do non-reducing sugars contain?
ketal/acetal
104
The nucleic acid polymer that has a sequence identical to a positive strand is positively or negatively stranded?
positively stranded
105
What is the bond that links the DNA/RNA backbone to nitrogenous bases?
N-glycosidic linkage (between pentose sugar and nitrogenous base)
106
What are the 3 major lipid components in eukaryotic membranes?
- cholesterol
- sphingolipids
- glycerophospholipids
107
Which amino acid is not referred to as and α-amino acid? What is it called?
proline (α-imino acid)
108
How do enveloped viruses acces a host cell?
- Receptor-mediated endocytosis
- direct fusion with the plasma membrane: must contact a specific receptor
109
Describe binary fission in bacteria
Replicated DNA becomes enclosed by a new plasma membrane and cell wall to eventually separate from the parent cell.
110
What is the general function of cortisol in the liver, skeletal muscle, and adipose tissue?
Liver: increase glycogen synthesis and gluconeogenesis
Skeletal muscle: decrease glucose uptake and protein synthesis, increase protein catabolism
Adipose tissue: increase lipid mobilization, decrease glucose uptake
111
1-letter abbreviation of threonine
T
112
What are carbohydrates called that have 3, 4, 5, 6, and 7 carbons?
- trioses
- tetroses
- pentoses
- hexoses
- heptoses
113
Asparagine structure
114
Which portions of DNA/RNA are polar/nonpolar?
polar: phosphate groups on backbone
nonpolar: nitrogenous bases
115
3-letter abbreviation of histidine
His
116
What composes a haploid (n) cell? Which cells are haploid?
22 autosomes
1 sex chromosome
Gametes are haploid.
117
What are the 3 main stages of the cell cycle and their components?
- interphase (G1, S, G2)
- mitosis (pro, meta, ana, telophases)
- cytokinesis
118
3-letter abbreviation of cysteine
Cys
119
What is the rolling circle mechanism of replication?
It is the mechanism used in bacterial conjugation to replicate the "**fertility plasmid**," or "F factor."
120
What is the region called between nucleosomes?
linker
121
What is the sedimentation coefficient of mitochondrial ribosomes?
55S
122
What is the role of starch?
food reserve in plants
123
Summarize the events in diakinesis
- nuclear envelope begins to break down, nucleoli disappear
- chiasmata move along the lengths of the chromatids until they reach the ends
- as the chromosomes begin to separate, they appear to be joined at their ends
124
How many carbons make up the simplest carbohydrates?
3
125
How do non-enveloped viruses access a host cell?
Receptor-mediated endocytosis:
The receptors are located near **clathrin-coated pits** that promote vesicle formation. A virus is endocytosed, the vesicle pH lowers, the clathrin coat depolymerized to form a smooth vesicle called an **endosome**. pH of the endosome continues to fall, disrupting the membrane, and releasing the virus.
126
In which meiosis does reductive division occur?
meiosis I (2n --\> n)
127
1-letter abbreviation of tryptophan
W
128
In bacteria, where does replication begin on DNA?
replication origin
129
What is the tertiary structure of a polypeptide?
spatial arrangement of amino acids that are far from one another (all the α-helices and β-pleated sheets that make up a subunit)
130
Looking at a carbohydrate structure, what determines if it is D/L?
In a Fisher projection, look at the chiral carbon (also called reference carbon) farthest from the carbonyl carbon. If the hydroxyl group on that carbon is on the right, it is D. If it is on the left, it is L.
131
1-letter abbreviation of glycine
G
132
What generally happens during cytokinesis?
There is cytoplasmic division of a cell into two daughter cells.
133
Adenine structure
134
1-letter abbreviation of glutamate
E
135
How many amino acids make up an oligopeptide?
10+ amino acids
136
What keeps the lysosomal environment acidic?
an ATPase proton pump in its membrane pumps 2 hydrogens in for every hydrolyzed ATP
137
Phenylalanine structure
138
Equation: Henderson-Hasselbalch pH
pH = pKa + log [A-]/[HA]
139
3-letter abbreviation of aparagine
Asn
140
3-letter abbreviation of tyrosine
Tyr
141
What is secondary active transport?
ionic gradients that have been established by primary active transport systems provide the driving force that allows for cotransport of other molecules against their gradient
142
What is the function lipase?
It hydrolyzes and breaks down phospholipids.
143
Sucrose structure
α-D-glucopyranose and β-D fructofuranose (glucose + fructose)
144
What are the 3 families of amino acids?
- nonpolar R group
- polar R group
- charged R group
145
What is the role of glycogen? What is its structure?
It is the storage polysaccharide common to all animals, mainly in skeletal muscle and liver tissue.
It is a branched polymer of D-glucose with branch points every 8 to 12 residues.
146
3-letter abbreviation of alanine
Ala
147
What are glycoproteins?
carbohydrates that are attached to membrane proteins (exterior)
148
What composes a diploid (2n) cell? Which cells are diploid?
- 44 autosomes
- 2 sex chromosomes
Somatic cells are diploid.
149
Cysteine structure
150
3-letter abbreviation of isoleucine
Ile
151
What is the purpose of the Golgi apparatus? What are some example?
It chemically modifies proteins.
- **Glycolsylation**: addition of carbohydrates
- Sulfation: addition of inorganic sulfate
- Proteolysis: reducing the size of the protein
152
Tyrosine structure
153
Tryptophan structure
154
Uracil structure
155
Are D or L amino acids found in proteins?
L amino acids
156
What is the pKa of arginine's side chain?
12.5
157
Summarize the events during telophase
- daughter chromosomes have reached each pole
- chromosomes begin to uncoil and extend
- microtubules being to disappear
- nuclear membrane forms around each of the two daughter nuclei
- nucleolus reappears
- cleavage furrow of cytokinesis deepens
- the cell is 4n
158
What are different shapes of bacteria?
159
What is the pKa of glutamate's side chain?
4.2
160
1-letter abbreviation of asparagine
N
161
Summarize the events during Meiosis I: Metaphase I
- homologous chromosomes align on the metaphase plate
- centromeres appear to be distant, chromosomes seem to touch each other only at their ends
- microtubules are attached at the centromeres
- nuclear membrane has disappeared
162
Describe the difference between sister chromatids and homologs within a homologous pair.
Sister chromatids are the identical strands of each chromosome after replication. Homologs are individual members of a homologous pair (1 homolog from mom, 1 from dad)
163
What is the space within the endoplasmic reticulum?
lumen
164
Which type of RNA brings amino acids to the site of protein synthesis?
transfer RNA (tRNA)
165
What are the two forms of starch? Describe their structures.
**α-amylose**: a linear, unbranched polymer of D-glucose residues linked together in α(1--\>4) linkages
**amylopectin**: a branched polymer of D-glucose residues linked together in primarily α(1--\>4) linkages but at the branch points in α(1--\>6) linkages (branch points every 24-30 residues)
166
What amino acid forms disulfide bonds?
cysteine
167
3-letter abbreviation of proline
Pro
168
What are the 5 major classes of steroids?
- androgens
- estrogens
- progesterone
- glucocorticoids
- mineralocorticoids
169
Summarize the events in leptotene
- the replicated chromosomes have begun to condense and become visible
170
What are the membranous sacs called in the Golfi?
cisternae
171
What are the two types of phospholipid movement within a bilayer and how frequent are they?
- **lateral diffusion**: between neighbors, happens frequently
- **transverse diffusion**: between layers, happens rarely
172
What are the pyrimidine bases?
- thymine
- cytosine
- uracil
173
1-letter abbreviation of phenylalanine
F
174
In hepatocytes, what is the final enzyme-catalyzed reaction that releases glucose from glygocen? What enzyme is used?
Glucose-6-phosphate + H2O ---\> Glucose + Pi
Enzyme that carries out reaction: **glucose-6-phosphatase**
175
The side chain of which amino acids is weakly ionized at neutral pH?
Histidine
176
At physiological pH, how are amino acids charged in their main structure? What is the term for this?
The α-amino group is positively charged, while the α-carboxyl group is negatively charged. They are zwitterionic.
177
Telocentric chromatids
178
3-letter abbreviation of methionine
Met
179
Is E. coli gram negative or positive?
gram negative
180
1-letter abbreviation of alanine
A
181
3-letter abbreviation of glutamate
Glu
182
3-letter abbreviation of serine
Ser
183
What is a symport?
integral membrane transporter that allows two different types of molecules (**cotransport**) to pass through in the same direction
184
What two functional groups must a carbohydrate have?
- aldehyde (aldose)/ketone (ketose)
- 2+ alcohol groups
185
Summarize the events in Meiosis I: Anaphase I
- microtubules pull homologous chromosomes apart toward each pole
- chromosomes still consist of sister chromatides (**dyad**)
- cytokinesis begins
186
What are inclusion bodies?
cytoplasmic structures within bacteria that store organice and inorganic molecules (like glycogen or phosphate)
187
What is the general function of aldosterone?
It increases the resabsorption of Na+, causing retention of Na+ in the ECF, thereby increasing ECF volume. This increases blood volume, pressure, and flow.
188
What is the structure of microtubules? What is their diameter? What are the main protein components?
- 25 nm
- α-tubulin + β-tubulin = dimer
189
Is viral mRNA positive or negative stranded?
positive stranded
190
Thymine structure
191
1-letter abbreviation of arginine
R
192
What happens to the hydrolysis products in a lysosome?
They diffuse out of the lysosome to be utilized in different organic processes.
193
What is the average pKa for the α-amino group on amino acids?
~9.4
194
What is the average pKa of α-carboxyl group on amino acids?
~2.2
195
What is an abbreviated drawn-out structure of a nucleotide?
196
What do bacteria use for movement? What is it composed of?
flagella, composed of the protein flagellin
197
2' deoxy-D-ribose (DNA) and D-ribose structures
198
What is the order in which a protein passes through the Golgi?
cis ► medial ► trans
199
What is the basic molecular formula of carbohydrates?
(CH2O)n
200
Glycine structure
201
What is significant about the interphase between meiosis I and II?
It does not have an S phase.
202
What is the major type of active enzyme within a lysosome?
hydrolytic enzymes (acid hydrolases - they only function at acidic pH)
203
What is an antiport?
integral membrane transporter that allows two different solute molecules (**cotransport**) through in opposite directions
204
What eukaryote produces asexually?
yeast
205
How does the Benedict's reagent react with an aldose/ketose?
The sugar is oxidized and the Cu2+ ion is reduced to give a brick-red precipitate.
206
What is the major enzyme in peroxisomes and what is its purpose?
Catalase degrades hydrogen peroxide that has accumulated from oxidation of fatty acids and amino acids.
2H2O2 ---\> 2H2O + O2
207
3-letter abbreviation of leucine
Leu
208
The nucleic acid template (complement) of a positive RNA strand is positively or negatively stranded?
negatively stranded
209
What are the 5 types of histones?
- H1
- H2A
- H2B
- H3
- H4
210
Metacentric chromatids
211
What are the 3 components of nucleotides?
- nitrogenous base
- pentose sugar
- phosphoric acid
212
What is the pKa of histidine's side chain?
6.0
213
How does the Tollen's reagent react with an aldose/ketose?
The sugar is oxidized and the Ag+ ion is reduced to silver metal, which precipitates as a silver mirror on the sides of the reaction vessel.
214
What is the directionality of a single strand of DNA?
5' --\> 3'
215
What is the quaternary structure of a polypeptide?
subunits that associate with one another
216
What is the structure of intermediate filaments? What is their diameter? What are the main protein components?
- 8-12 nm
- can be made of different proteins depending on the cell
217
What is a prokaryote? What are the two domains?
single-celled organism that lacks a nucleus, mitochondria, and any membrane-bound organelles
- Archaea
- Bacteria
218
What is a glycocalyx? What are two examples?
a polysaccharide layer that covers the surface of a bacterial cell
- capsule
- slime layer
219
What is the direction of amino acid synthesis?
amino terminal ► carboxyl terminal
220
What is the structural residue common to all sphingolipids? What is its structure?
Ceramide
221
What is a glycolipid?
a membrane lipid attached to a carbohydrate (usually on the exterior)
222
What are the 3 main components of a cell's cytoskeleton?
- microtubules
- microfilaments
- intermediate filaments
223
Cholesterol structure
224
Glutamate structure
225
What four atoms make up the peptide bond?
amide: 0=C-N-H
226
1-letter abbreviation of histidine
H
227
Is the hydrolysis of a peptide favorable or unfavorable?
favorable
Peptide synthesis requires energy.
228
What is the purpose of nuclease?
It hydrolyzes and breaks down DNA.
229
What 3 molecules/organelles do mitochondria contain?
- DNA (mtDNA)
- ribosomes
- tRNA
230
What is the process called through which a virus introduces its genome into a host?
penetration
231
What are the 4 groups bonded to an amino acid's α-carbon?
- basic amino group (NH2)
- acidic carboxyl group (COOH)
- hydrogen (H)
- specific side chain (R)
232
What is the sedimentation coefficient of prokaryotic ribosomes? What about the large and small subunits?
70S
- Large subunit: 50S
- Small subunit: 30S
233
How does the α anomer differ from the β anomer?
α anomer: OH group at anomeric carbon is on the opposite side of the ring from the CH2OH group attached to the reference carbon
β anomer: OH group at the anomeric carbon is on the same side of the ring from the CH2OH group attached to the reference carbon
234
From what region do microtubules grow? In what direction? What are 3 examples?
microtubule organizing centers (MTOC) add to the + end which extends toward the cell periphery
- centrosome
- kinetochores
- centrioles
235
What are integral membrane proteins?
proteins embedded in the lipid bilayer (either **trans-membrane proteins** or exposed at only the interior/exterior)
236
What are the core histones involved in nucleosomes?
- H2A
- H2B
- H3
- H4
237
What is Tay-Sachs disease?
a recessive disorder in which there is an absence of the lysosomal enzyme hexoaminidase A , allowing accumulation of a particular glycolipid within the lysosome
238
Summarize the events in pachytene
- chromosomes continue to condense and become more distinct
- genetic recombination occurs via **crossing-over**
239
What is a uniport?
integral membrane transporter than only allows one type of solute through in one direction
240
Describe the structure of gram (+) bacteria and how it affects their gram stain result.
They have a thick **peptidoglycan** layer outside their plasma membrane. They also have **techoic acids** that extend to the surface of the cell.
They stain purple.
241
What is sphingomyelin's structure? Where is it found?
sphingolipids with phosphoethanolamine or phosphocholine attached to the C1 of the ceramide
They are abundant in myelin sheaths.
242
What holds nitrogenous bases together?
A=T: 2 hydrogen bonds
C≡G: 3 hydrogen bonds
243
What generally happens during the second growth phase (G2)?
Chromatin begins to condense, and protein synthesis is quite active as the cell prepares for mitosis.
244
Sucrose structure
β-D-galactopyranose and β-D-glucopyranose
(galactose + glucose)
245
What is facilitated diffusion?
movement down a concentration gradient with the help of integral membrane proteins
246
What is bacterial transformation?
uptake of DNA from the surrounding medium
247
Define permease
protein transporters that allow for movement of a solute across a membrane
248
Triacylglycerol structure
glycerol + esterified fatty acids
249
What is the pKa of lysine's side chain?
10.8
250
In what organelle are steroids synthesized?
mitochondria
251
Threonine structure
252
What are histones made of?
They are basic proteins consisting of a high percentage of lysine and arginine residues, with positively charged amino groups at physiologic pH, allowing an electrostatic relationship with the negatively charged DNA.
253
What is the host range of a virus?
viral specificity for a host cell, dependent upon the interaction of a virus with the host cell's surface proteins, glycoproteins, and glycolipids
254
What is pinocytosis?
endocytosis of extracellular fluid (ECF)
255
What is a nucleosome?
a specific length of DNA coiled around histones
256
What is phagocytosis?
endocytosis of particulate matter
257
Which cells do not contain mitochondria?
erythrocytes
258
Within what range is a weak acid in its buffering range?
within 1 pH unit of its pKa
259
3-letter abbreviation of lysine
Lys
260
Summarize the events in Meiosis II: Prophase II
- chromosomes begin to condense
- microtubules attach to the kinetochores of each chromosome
261
What are the 3 types of bacterial DNA transfer?
- conjugation
- transformation
- transduction
262
What are the building blocks of a virus's protein coat?
capsomers
263
What takes place of the nucleus in prokaryotes?
nucleoid
264
Leucine structure
265
Isoleucine structure
266
What is the bond called that links nucleotide units?
phosphodiester bond (between pentose sugar and phosphate group)
267
Summarize the events in Meiosis II: Anaphase II
- centromeres divide, and chromatids of each of the 23 chromosomes are pulled to opposite poles
- cytokinesis begins
- cell is 2n
268
What are glycerophospholipids? What is their structure?
They are the main component of all biological membrane (phospholipids)
Glycerol + 2 fatty acids (C1, C2) + phosphate (C3) which bears a negative charge at physiologic pH
269
What generally happens during the first growth phase (G1)?
RNA and proteins are synthesized, the **centriole pair** separates, the cell and its nucleus begin to increase in volume.
270
The side chains of which amino acids are highly ionized at neutral pH?
- Aspartate
- Glutamate
- Lysine
- Arginine
271
What is the general function of estradiol?
It regulates the ovarian cycle, controls certain metabolic processes, and develops secondary sex characteristics.
272
What stabilizes α-helices in a polypeptides?
hydrogen bonding between CO and NH groups that are 4 residues apart
273
What is bacterial transduction?
Viruses infect a host cell with their DNA. When they leave, they remove their DNA and sometimes remove some of the host's DNA with it. In this way, they can transfer bacterial DNA.
274
What is the reference compound for the L and D designation of carbohydrates?
Glyceraldehyde
275
Define the isoelectric point (pI) of an amino acid
the pH at which an amino acid carries no **net** electric charge
276
How does amino acid separation work by electrophoresis?
If two amino acids are placed in an electric field, any whose pH \> pI will migrate toward the anode (positive electrode), while any whose pH \< pI will migrate toward the cathode (negative electrode).
277
1-letter abbreviation of lysine
K
278
Summarize the events during Meiosis I: Telophase I
- the migrating chromosomes (dyads) are at each pole
- nuclear membrane reforms
279
If a cell is destined to never divide, it will remain arrested in which phase?
first growth phase (G1)
280
What are sphingolipids derived from?
lipids not based on a glycerol backbone. Instead they are derivatives of amino alcohols
