Chapter 6 - Structure and Function in Cells and Viruses Flashcards
Summarize the events in zygotene
- 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
1-letter abbreviation of isoleucine
I
Equation: isoelectric point (pI)
pI = [pKa1 + pKa2]/2
What are 3 major groups added to C1 of phospholipids?
- phosphoethanolamine
- phosphocholine
- serine
What is the beginning and end result of meiosis?
1 diploid cell makes 4 haploid cells
In the titration of protonated glycine by a strong base, how does its charge change over time and which groups are changing?
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)
1-letter abbreviation of proline
P
What is simple diffusion?
spontaneous movement of solute molecules through a lipid bilayer, from high to low concentration (down the concentration gradient)
Cytosine structure
Lysine structure
In what direction do microfilaments grow (polymerize)? In what direction do they depolymerize?
They are polymerized fastest at the + end and depolymerize fastest at the - end.
What is the purpose of the rough endoplasmic reticulum?
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.
What holds sister chromatids together?
centromere
What are anomers?
carbohydrates that differ diastereomerically (α/β) at the anomeric (C1) carbon
How do proteins get into the nucleus from the cytoplasm?
through nuclear pores that span the inner and outer membranes
What is nucleoplasm?
the mixture of chromatin and the aquous phase of the nucleus
What is the secondary structure of a polypeptide?
spatial arrangement of amino acids that are close to one another (β-pleated sheets and α-helices)
3-letter abbreviation of glycine
Gly
3-letter abbreviation of threonine
Thr
What is the general function of progesterone?
It prepares the uterine lining for implantation of an ovum and maintains it if implantation occurs.
What are bivalent chromosomes? Tetrads?
Those that have undergone synapsis in meiosis because there are four chromatids. The paired homologous chromosomes are also called tetrads.
In order for an organism to reproduce asexually, should it be diploid or haploid?
either
Alanine structure
Acrocentric chromatids
Summarize the events in Meiosis II: Telophase II
- nuclear membrane forms
- chromosomes decondense
- cleavage furrow of cytokinesis deepens
What are the two major types of bulk transport?
- endocytosis
- exocytosis
What are peripheral membrane proteins?
proteins weakly attached to the surface of the lipid bilayer
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
What is the difference between pyranose and furanose?
pyranose: 6-membered cyclic carbohydrate
furanose: 5-membered cyclic carbohydrate
What are the two structures of viruses?
- isometric
- helical
Describe prokaryotic DNA structure
double-stranded and circular
Bacteria sometimes have plasmids, which are also circular and double-stranded, but smaller
What are the convoluted foldings of mitochondria’s inner membrane called?
cristae
What is the sedimentation coefficient of eukaryotic ribosomes? What about the large and small subunits?
80S
Large subunit: 60S
Small subunit: 40S
What are mesosomes?
invaginations of bacterial cell membranes
What is the pKa of aspartate’s side chain?
3.9
1-letter abbreviation of methionine
M
Valine structure
What is chemotaxis?
attraction towards or repulsion away from certain chemicals (exhibited by bacteria)
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
Fatty acid structure
carboxylic acids with a hydrocarbon side chain
Guanine structure
3-letter abbreviation of tryptophan
Trp
What are ampholytes?
amphoteric molecules that exist as zwitterions at physiological pH
What are nonhistones?
They are acidic proteins that bear a net negative charge and interact with DNA (ex: RNA polymerase)
3-letter abbreviation of valine
Val
1-letter abbreviation of serine
S
Summarize the events in diplotene
- crossing-over becomes visible at structures called chiasmata (single: chiasma)
What is the form of genetic information as a cell prepares for division?
chromosomes (highly condensed - visible)
In order for an organism to reproduce sexually, should it be diploid or haploid?
diploid
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
Which type of RNA helps define the site of protein synthesis?
ribosomal RNA (rRNA)
What is the general function of testosterone?
It aids in sperm maturation and development of secondary sex characteristics
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).
3-letter abbreivation of phenylalanine
Phe
Serine structure
What is primary active transport?
hydrolyzes ATP to ADP and Pi for energy to move molecules across their concentration gradients
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
What stabilizes β-pleated sheets in polypeptides?
hydrogen bonds between CO and NH groups of different polypeptide chains
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.
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
3-letter abbreviation of arginine
Arg
What is the bond called between monosaccharides?
O-glycosidic linkage
Glutamine structure
Summarize the events in Meiosis II: Metaphase II
- chromosomes line up along the metaphase plate
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.
Where is rRNA transcribed?
from specific genes of DNA within the nucleolus
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.
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
3-letter abbreviation of glutamine
Gln
What are the purine bases?
- adenine
- guanine
What is passive transport? What are the two types?
movement of a molecule from high to low concentration
- simple diffusion
- facilitated diffusion
What generally happens during the synthetic (S) phase?
All 46 strands of chromatin are replicated to make 92 sister chromatids. Daughter centrioles are synthesized.
Methionine structure
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.
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.
Summarize the events in Meiosis I: Cytokinesis
- 2n –> n (reductive division)
What are the 4 phases of Meiosis I: Prophase I?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
What is the primary structure of a popypeptide?
the sequence of amino acids in a protein and location of disulfide bonds
Proline structure
1-letter abbreviation of leucine
L
What is the function phosphatase?
It hydrolyzes and removes phosphate groups from the substrate.
What is the form of genetic information in a nondividing (interphase) cell?
chromatin (not visible)
What is the purpose glycosidase?
It hydrolyzes and breaks down carbohydrates.
3-letter abbreviation of aspartate
Asp
1-letter abbreviation of tyrosine
Y
What is the major protein in mitochondria’s outer membrane and what is its function?
porin - a transmembrane protein that allows various molecules through
Which type of RNA allows for the synthesis of proteins?
messenger RNA (mRNA)
Whats is a cystine?
Two cysteine residues that are part of a disulfide bond are oxidized (lose their H’s).
Arginine structure
Equation: number of stereoisomers
2n
n = # of chiral centers
Summarize the events during metaphase
- chromosomes align at the equator of the cell (metaphase plate)
- nuclear membrane has completely disappeared
1-letter abbreviation of valine
V
Where are ribosomes found?
- cytoplasm
- rough ER
- mitochondrial matrix
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.
1-letter abbreviation of cysteine
C
Histidine structure
1-letter abbreviation of glutamine
Q
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-).
What is the function protease?
It hydrolyzes peptide bonds to break apart proteins.
Aspartate structure
1-letter abbreviation of aspartate
D
What group(s) do non-reducing sugars contain?
ketal/acetal
The nucleic acid polymer that has a sequence identical to a positive strand is positively or negatively stranded?
positively stranded
What is the bond that links the DNA/RNA backbone to nitrogenous bases?
N-glycosidic linkage (between pentose sugar and nitrogenous base)
What are the 3 major lipid components in eukaryotic membranes?
- cholesterol
- sphingolipids
- glycerophospholipids
Which amino acid is not referred to as and α-amino acid? What is it called?
proline (α-imino acid)
How do enveloped viruses acces a host cell?
- Receptor-mediated endocytosis
- direct fusion with the plasma membrane: must contact a specific receptor
Describe binary fission in bacteria
Replicated DNA becomes enclosed by a new plasma membrane and cell wall to eventually separate from the parent cell.
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
1-letter abbreviation of threonine
T
What are carbohydrates called that have 3, 4, 5, 6, and 7 carbons?
- trioses
- tetroses
- pentoses
- hexoses
- heptoses