Bonds and Polarity
electronegativity |
atom's attraction for electrons in a covalent bond (higher when atom more strongly pulls shares electron towards oneself) |
polarity |
polar when electrons are shared unequally because an atom is more electronegative |
hydrogen bonds |
form when H covalentaly bounds to electronegative atom is also attracted to another electronegative atom -- electronegative partners are usually O or N in living cells |
Mendel and the Gene
phenotype |
outward appearance |
genotypes |
allele combination |
progeny |
descendant, offspring |
Complete dominance |
dominant allele masks recessive allele |
incomplete dominance |
blending of phenotypes ie pink flower from red and white |
codominance |
two dominant alleles affect the phenotype in distinct, separate ways |
epistasis |
traits determined by two or more genes, one gene can alter phenotypic expression of gene at separate locus |
polar covalent bonds in water
- polar due to electronegativity of oxygen
- uneven distribution of charge
- polarity allows water molecules to form
hydrogen bonds |
Properties of Water
Cohesive behaviour |
bring water up roots of plants, surface tension |
ability to moderate temperature |
high specific heat capacity due to hydrogen bonds |
expansion upon freezing |
ice is less dense than water, floats |
versatility as a solvent |
polar dissolves polar |
Isomers
structural |
different covalent arrangements |
Cis-Trans |
same covalent bonds, differ in spatial arrangements |
enantiomers |
mirror images of each other |
microscopy
light microscope |
most used in laboratories today |
scanning electron miscroscope |
useful for studying the topography of a specimen |
transmission electron microscope |
used to study internal structure of cells |
Inheritance of Diseases (memorize)
Autosomal Dominant: huntington disease, achrondoplasia |
Autosomal Recessive: Cystic fibrosis, Tay-Sachs, Sickle cell anemia |
X-Linked Recessive: colour blindness, Duchenne muscular dystrophy, Hemophilia |
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Carbohydrates
- sugars and polymers of sugars
- usually made from multiples of CH2O
- built from monosaccharides |
Lipids
- does not form polymers
- hydrophobic
- mostly non-polar (hydrocarbons)
- includers fats, phospholipids, steroids |
Proteins
- made from amino acid chains that are
joined from peptide bonds (carboxyl
group to amino groups)
- catalyze rxns, structure support,
transport, defense, movement |
water molecule is released each time a peptide bond is formed (dehydration synthesis)
Phospholipids
- hydrophilic head
- hydrophobic tail
- amphipathic (having hydrophilic and phobic
parts
- spontaneously self-assemble into bilayer
when added to water |
sickle cell anemia
- crescent shaped exterior
- abnormal interactions with other sickle-cells reducing capacity to carry oxygen |
plants and some algae
sporophyte |
diploid cell that makes haploid spores by meiosis |
gametophyte |
a haploid that spores grow into via mitosis |
- haploid cells grow by mitosis into haploid multicellular organisms
- haploid adults produce gametes by mitosis
amino acid types
hydrophobic |
carbon rich side chains(in many membrane bound proteins) |
hydrophilic |
hydrogen bonds |
charged |
work well with oppositely charged amino acids or other molecules |
endosymbiont theory
modern eukaryotic cells evolved from prokaryotic cells that were engulfed by bigger prokaryotic cells. consistent with theory that all organisms arose from a single common ancestor |
other cell structures
peroxisome |
contain enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen |
centrosomes and centrioles |
help organize microtubule assembly in animal cells |
dna replication
SSB Proteins |
keeps dna from coming apart (reannealing) |
topoisomerase |
prevent dna from uncoiling |
helicase |
breaks apart the hydrogen bonds to separate the DNA strands |
DNA polymerase |
replicates DNA to build a new one |
Ligase |
puts together the DNA strands |
primase |
builds primers (made of RNA) for polymerase to build on |
okazaki fragments |
sequences of DNA neucleotides on the lagging strand that will later be bonded together by ligase |
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the nucleus
basic functions |
contains most of cell's genes |
nuclear envelope |
double membrane, each membran consists of a lipid bilayer |
nuclear pores |
regulate entry and exit of molecules |
nuclear lamina |
maintains shape of nucleus (composed of protein filaments) |
endoplasmic reticulum
smooth |
synthesis lipids, metabolize carbohydrates, detoxifies poisons, stores calcium ions |
rough |
site for protein synthesis, produces transport vesiclres that distribute lipids and proteins to other components of the system |
- accounts for half of total membrane in the cell
- continuous with nuclear envelope
golgi apparatus and lysosomes
gogli apparatus |
processes and modifies proteins from ER to ship to target locations |
lysosomes |
compartment of enzymes, hydrolyzes proteins, fats, polysaccharides, nucleic acids, work best in acidic environments |
meiosis cell cycle
prophase I |
chromosomes condense, crossing over (synapsis) takes place |
metaphase I |
tetrads align in center of the cell |
anaphase I |
chromosome migrate to opposite sides, chromatids are still joined by centromeres |
telophase I |
cytokinesis occurs, two daughter haploid cells are formed |
prophase II |
chromosomes move towards center |
Metaphase II |
chromosomes aligned at center, centromeres facing opposite directions |
anaphase II |
chromatids separated, move towards poles |
telophase II |
cytokinesis divides into four nuclei, nuclear membrane develops, four daughter cells or gametes are produced |
whole process ends with four haploid daughter cells
Abnormal Chromosome numbers
Aneuploidy |
when nondisjunction occurs in the fertilization of gametes |
monosomic zygote |
zygote only has one copy of a particular chromosome |
trisomic |
zygote has three copies of a chromosome (down syndrome) |
Aneuploidy of Sex Chromosomes
XXX |
healthy, no unusual physical features |
XXY (klinefelter syndrome) |
extra X chromosome in males |
Monosomy (turner syndrome) |
produces XO females who are infertile |
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cell cycle in mitosis
interphase |
centrosomes have formed, chromosomes aren't seen clearly |
prophase |
chromosomes condense, mitotic spindle starts to form, microtubules lengthen moving centrosomes away from each other |
prometaphase |
nuclear envelope fragments, kinetochore formed on centromeres |
metaphase |
chromosomes align in the center of the cell |
anaphase |
chromosomes are split and sister chromatids move to opposite poles |
telophase |
fibers disappear and membrane reforms around each set |
cytokinesis |
cleavage of cell and its contants divide into 2 |
cancer occurs when cells don't properly respond to control mechanisms (uncontrolled mitosis)
subphases of interphase
G1 checkpoint |
growth phase: can continue on to other phases once receives go ahead at this stage |
S phase |
duplication of DNA |
cyclins and cycli-deependent Kinases (Cdk) |
always present but fluctuate during cell cycle based on concentrations of cyclin |
G2 |
final subphase, more growth and protein synthesis |
Maturation promoting factor (MPF) |
cyclin-Cdk complex that triggers cell passage past G2 phase into M phase |
M checkpoint |
won't enter anaphase unless chromosomes are all attatched to spindle microtubules at kinetechores, may delay anaphase to ensure daughter cells receive correct # of chromosomes |
cells grow in all three subphases of interphase but chromosomes are only duplicated during S phase
Sources of genetic variation
- crossing over during prophase I
- independent assortment of chromosomes
- Random fertilization |
Mutations
nondisjunction |
problem during meiosis that results intoo mayn or too few chromosomes: down syndrome (trisomy) |
deletion |
portion of chromosomes are lost, caused by viruses or chemicals |
duplication |
gene sequence is repeted one or more times within one or more chromosomes |
inversion |
certain gene segments become free and then are reversed |
translocation |
part of the chromosome changes places with another part |
DNA features
nucleotide |
phosphate group, 5 carbon sugar, nitrogenous base |
nitrogenous base |
adenine, guanine, thynine, cytosine |
phosphate group between 5' and 3' |
deoxynucleotides |
phosphodiester bonds |
phosphate group of one nucleotide bonds to the 3/ oxygen of another nucleotide |
5' to 3' |
on top (watson), runs 3' to 5' on bottom(crick) |
bonds between the two strands |
non covalent hydrogen bonds with complimentary base (base pairs) |
pyrimidines |
thynin and adenine, single ring structure |
purines |
guanin and cytosine, double rings |
- 2 types of nucleic acids (DNA and RNA)
- DNA provides directions for its own replication
- DNA, RNA, protein
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