Chapter 6 - Structure and Function in Cells and Viruses Flashcards
Glycerophospholipid
main component of all biological membranes, two fatty acid tails esterified to C1 and C2, with a phosphate group on C3, amphiphilic in nature
Sphingolipids
derivatives of amino alcohols, C2 carbon has amino group that can be linked to a FA via amide linkage (called a ceramide) structural residue that is common to all sphingolipids
Sphingomyelin
sphingolipid with a phosphoethanolamine or phosphocholine group on C1 of ceramide
Cerebroside
sphingolipid when a single monosaccharide is attached to C1 of ceramide
Gangliosides
several sugar residues are attached to C1 of the ceramide
Steroid Hormones
- Progesterone
- Glucocorticoids
- Mineralocorticoids
- Androgens
- Estrogens
Progesterone
function in women, prepares the uterine lining for implantation of an ovum; after implantation this steroid is necessary to maintain the endometrial lining of the uterus, stimulates mammary tissue growth for parturition, also synthesized in low levels in testes and adrenal cortex of both sexes
Cortisol
secreted by adrenal glands, in liver it acts to increase glycogen synthesis and gluconeogenesis, in skeletal muscle it acts to decrease both glucose uptake and protein synthesis, and increases protein catabolism, in adipose tissue it increases lipid mobilization and decreases glucose uptake (aka hydrocortisone)
Aldosterone
synthesized and released from adrenal cortex, increases reabsorption of Na+ at kidney, intestines, salivary glands, and sweat glands, increase in blood vol, BP, and blood flow
Testosterone
synthesized in male in Leydig cells of testes and aids in sperm maturation
Estradiol
primary estrogen in women, synthesized in theca cells of the ovarian follicles
Purines
Adenine (A) and Guanine (G)
Pyrimidines
Thymine (T) and Cytosine (C) and Uracil (U) in RNA
Phosphodiester Bond
links nucleotides together, backbone of DNA and RNA consists of alternating pentose and phosphates
What are the differences between DNA and RNA?
RNA uses uracil instead of thymine, ribose ring of RNA is hydroxylated at 2’ position whereas in DNA it’s not
messenger RNA (mRNA)
RNA polymers that allow for synthesis of proteins are called transcripts of mRNA
transfer RNA (tRNA)
RNA polymer that brings amino acids to site of protein synthesis
Chromatin
a complex of linear, double-stranded DNA, and protein (histones), as it prepares for division (mitosis and cytokinesis) the chromatin highly condenses into chromosomes
Gamete
egg or sperm, 23 chromosomes, (22 autosomes, 1 sex chromosome)
Zygote
fertilized egg, diploid or 2n, somatic cells, 23 pairs of chromosomes, 46 chromosomes total
How do chromatids becomes chromosomes?
individual chromatids become chromosomes when the centromere joining the sister chromatids divides and the chromatids are allowed to separate
Histones
basic proteins consisting of a high percentage of Lys and Arg
Nonhistones
proteins that associate with DNA, but are not histone proteins, they are acidic (-), e.g., RNA polymerase
Core Histones
H2A, H2B, H3, H4, bind roughly 1 and 3/4 turns of DNA or 146 base pairs
3 Major Phases of the Cell Cycle
Interphase (G1, S, and G2), Mitosis (prophase, metaphase, anaphase, telophase), Cytokinesis
First Growth Phase (G1)
G1 lasts about 10 hours, RNA and proteins are actively being synthesis
Synthetic Phase (S)
6-8 hours, each of the 46 strands of chromatin, except centromeres, are replicated
Second Growth Phase (G2)
2-6 hours, chromatin begins to condense becoming more tightly coiled, protein synthesis is active
Prophase
two centriole pairs move apart, microtubules begin to radiate from each pair in all directions, finishes with chromosomes, each with a pair of sister chromatids
Mitotic Spindle
formed by microtubules during prophase, these spindles separate chromosomes during anaphase
Metaphase
fully condense chromosomes align themselves along equator of cell (metaphase plate), nuclear membrane has complete disappeared
Anaphase
centromeres of each chromosome aligned on metaphase plate divide and two sister chromatids (now daughter chromosomes), move towards opposite poles (should have 92, 46 moving towards each pole)
Telophase
all daughter chromosomes have reached their respective poles, each chromosome uncoils/extends, microtubules of spindle apparatus disappear as nuclear membrane forms around each of 2 daughter nuclei, nucleolus reappears, cleavage furrow of cytokinesis deepens
Cytokinesis
cytoplasmic division of a cell into two daughter cells, begins during late anaphase and its completion signals the end of mitosis (or meiosis)
Meiosis
diploid 2N cells become haploid gametes (N), undergo DNA replication, then two nuclear divisions
Gametogenesis
formation of gametes
Reductive Division
after first nuclear division one cell with 46 chromosomes becomes two cells with 23 each, each will enter into interphase that precedes meiosis II
Meiosis I: Prophase I
long stage, further broken into five stages: leptotene, zygotene, pachytene, diplotene, and diakinesis
Leptotene
replicated chromosomes started condensing now becoming visible
Zygotene
homologous chromosomes begin to pair up longitudinally for crossing-over (genetic recombination aka synapsis)
Synaptonemal Complex
specialized protein and RNA scaffold, appears between the pairing chromosomes to join them
Pachytene
chromosomes continue to condense, become more distinct, genetic recombination occurs (crossing-over)
Diplotene
homologous chromosomes separate, crossing-over becomes visible at structures called chiasmata
Chiasmata
(singular: chiasma), at each chiasma any one of the four chromatids may be involved in a cross-over event
Bivalent
refers to homologous chromosomes which have undergone synapsis
Diakinesis
nuclear envelope begins to break down, nucleoli disappear, chiasmata move along lengths of chromatids until they reach ends, as homologous chromosomes begin to separate they appear to be joined to each other at their ends
Metaphase I
homologous chromosomes align on metaphase plate, microtubules from spindle apparatus are attached at the centromeres and the nuclear membrane has disappeared
Anaphase I
microtubules pull chromosomes apart, centromeres don’t divide, cytokinesis begins
Telophase I
migrating chromosomes (dyads) complete movement to opposite poles, nuclear membrane reforms, cytokinesis more pronounced
Cytokinesis
diploid cell with 46 chromosomes, divided into two haploid cells, each with 23 chromosomes
Interphase II
second meiotic interphase is brief, DNA replication does not take place during S phase of interphase
Meiosis II
quite similar to stages of mitosis
Prophase II
chromosomes begin to condense, microtubules of spindle apparatus attach to the kinetochores of each chromosome
Metaphase II
chromosomes line up along metaphase plate as haploid cells prepare for division
Anaphase II
centromeres begin to divide, chromatids of each of 23 chromosomes are pulled to opposite poles of dividing cell, chromatids are no longer sister chromatids, DNA replication and crossing-over during pachytene of prophase I, DNA no longer the same
Telophase II
a nuclear membrane forms around the expanding chromosomes, cleavage furrow deepens
Cytokinesis (of Meiosis)
four haploid cells, each with 23 chromosomes, will have been derived from one diploid cell (each of the four cells enters interphase where they’re arrested at G1 phase)
Sexual Reproduction
alternation of diploid and haploid phases of an organism’s life cycle
Germ Cells
haploid, produced by meiosis
Somatic Cells
diploid, produced by mitosis
Micelles
spherical structures that are formed when enough phospholipids congregate together such that polar heads interact with water while the hydrophobic tails exclude water
Lipid Bilayers
hydrocarbon tails of two phospholipid sheets interact with one another to exclude water
Lateral Diffusion
allows neighboring phospholipids to easily exchange places
Transverse Diffusion
movement of a phospholipid from one lipid plane to the next (a very rare event)
Trans-membrane Proteins
span the lipid bilayer
Simple Diffusion (passive)
movement of solute molecules through a lipid bilayer, from high conc. to low conc., down a concentration gradient
Facilitated Diffusion
concentration gradient, but solute molecules must interact with integral membrane proteins embedded in the lipid bilayer
Uniport
one type of solute molecule passes through a transmembrane protein in one direction
Symport
two different types of solute molecules pass thru a membrane in the same direction
Antiport
two different types of solute molecules pass thru a membrane in opposite directions
Permeases
protein transporters that allow movement of a solute across a membrane
Passive Transport
facilitated diffusion and simple diffusion
Active Transport
solute is being transported against its concentration gradient, energy will be required
Primary Active Transport
ATP powered, Na+-K+ pump is classic example
Na+-K+ ATPase
maintain intracellular concentrations of Na+ and K+, antiport, two K+ ions into the cell for every three Na+ out
Ca2+ ATPase
protein ensures that Ca2+ concentration within the cell is always at a low level by pumping two Ca2+ ions out of the cytosol for every ATP hydrolyzed
Secondary Active Transport
ionic gradients made by primary active transport systems can provide a driving force that allows for the cotransport of other molecules against their concentration gradients
Group Translocation
found in certain bacteria, sugar residue like glucose is phosphorylated as it is being transported through the plasma membrane
Endocytosis
invagination of a portion of their membrane, will eventually pinch off to form an internalized vesicle (an endosome)
Pinocytosis
cell drinking, invagination resulted in a vesicle containing liquid portion
Phagocytosis
cell eating
Bulk Transport
exocytosis and endocytosis
Smooth Endoplasmic Reticulum
lacks ribosomes, appears more tubular in shape, involved in synthesis of a lot of cell’s membrane lipids, including neutral fats, phospholipids, prostaglandins, and steroid hormones
SER of Hepatocytes
involved in hydroxylation reactions that aid in the detoxification of drugs
Rough Endoplasmic Reticulum
ribosomes line face of it, bound to membrane by their large (60S) subunit, ribosomes synthesize membrane and secretory proteins that are then passed through the membrane of the RER and into the lumen post-translational modification begins, then proteins are shuttled to Golgi for more PTMs
Golgi Apparatus
cisternae of Golgi is divided into three distinct regions, sorts and packages proteins on the trans face of the Golgi
Cis Cisterna
face the nucleus and endoplasmic reticulum
Trans Cisterna
face the plasma membrane
Phosphatases
remove phosphate groups from sugar residues
Peroxisomes
single membrane-bound organelles found within the cellular cytoplasm that contain a variety of enzymes
Microfilaments
7 nm in diameter, made of G-actin—the monomers begin to polymerize and form a long, double-helical structure called F-actin, each G-actin monomer is arranged in the same direction giving polarity
Cocci
spherical bacteria
Spirilla
bacteria that have a rigid twist to their rod-like structure
Prokaryotic cells
plasma membrane bounds cytoplasm, invaginations of bacterial cell membranes are called mesosomes, NO nucleus
Does the cytoplasm of bacterial cells contain membrane-bound organelles?
No
Inclusion Bodies
contain organic molecules like glycogen or inorganic stuff like phosphate granules
Nucleoid
a region of prokaryotic cells that contains their circular, double-stranded DNA chromosome
Plasmids
chromosomes which are circular and double stranded in bacteria
Gram positive (+)
bacteria that stained purple, thick homogeneous peptidoglycan layer outside their plasma membrane
Gram negative (-)
stain red or pink, much thinner peptidoglycan layer around plasma membrane, but around this layer is an outer membrane that contains lipopolysaccharides and porins to stabilize the membrane and act as an endotoxin
Bacterial Conjugation
transfer of genetic info occurs by cell-cell contact (F+ = male, F- = female), F = fertility plasmid, F factor replicates by a process called rolling circle mechanism
Transformation
uptake of genetic material from surrounding medium; this new genetic material is incorporated into host chromosome
Transduction
transfer of bacterial genes by viruses
Capsomers
building blocks composed of a specific number of individual proteins that make up the protein coat of viruses
Viruses are made of:
a nucleic acid and a protein coat
Naked Virus
gain access to host’s cytoplasm by receptor-mediated endocytosis—receptors are located near depressions called clathrin-coated pits
Clathrin
acts as a scaffold that promotes vesicle formation on host cell
Enveloped Viruses
enter host either through receptor-mediated endocytosis or by direct fusion with the plasma membrane
