biology

cell theory

1. all organisms made up of cells
2. cell is basic unit of life
3. all cells arise from pre-existing cells

nucleoli

region in nucleus where ribosome assembly occurs

endosymbiotic theory

cell engulfed bacterium to gain it’s ATP producing skills, have own DNA (maternal)

mitochondrial inner membrane

where Krebs cycle takes place (where electron transport chain and ATP synthase are embedded)

cristae

folds of membrane increase surface area for activity

rough endoplasmic reticulum

organelle that has ribosomes on surface that make proteins for outside the cell or for embedding in membrane

smooth endoplasmic reticulum

organelle that has role in lipid metabolism (produces phospholipids) steroid hormone synthesis, detoxification

golgi apparatus

organelle with transport vesicle at cis face, secretory vesicle released from trans face

lysosomes

organelle that breaks down cellular material, are membrane bound vesicles that have hydrolytic enzymes with low pH

autophagy

process where intracellular waste enclosed in vesicle which fuses with lysosome for degradation

peroxisome

organelle that accumulates and neutralizes peroxides, protects against oxidative stress, and breaks down fatty acids through beta-oxidation

microfilaments

smallest, composed of double helix of actin polymers, play role in cell movement, contribute to cleavage furrow

G-actin

single actin monomer is globular protein

F-actin

polymerize G-actin to create actin strand polymer form

phagocytosis

engulfment of particles by cell

microtubules

tubulin dimers that maintain structural integrity of cell, acts as highways for vesicles, form mitotic spindles for mitosis

tubulin dimer

polymers of alpha-tubulin and beta-tubulin

kinesin

motorprotein that moves from nucleus to membrane (- to +)

dynein

motor protein that moves from membrane to center of cell (+ to -)

centrosome

main microtubule organizing centers (MTOCs), made of 2 centrioles

centriole

made of 9 sets of microtubule triplets

flagella

whip-like structures involved in cell mobility

* eukaryotic flagella flap back and forth (ATP)
* prokaryotic have rotary motion (powered by protein gradient)

9 + 2 structure

outer ring of 9 pairs of microtubules surrounds inner ring of 2 microtubules, make up flagella/cilia

synapse

cell edge

cilia

shorter proejcts that help move substances across cell surface

depolymerize/polymerize

polymerize at + end (add to microtubule) and depolymerize (shrink microtubule) at - end

treadmilling

polymerizing and depolymerizing microtubules/microfilaments at same time (no net change)

intermediate filaments

size between microfilaments and microtubules, protein polymers that provide structural support and involved in cell-to-cell adhesion processes

lamin (nuclear lamina)

provides sturctural support to nucleus

proteases

enzymes that catalyze breaking bonds

primary structure

linear chain of amino acids that form backbone of the protein

C-terminus

carboxylic acid end of protein, new amino acids added to this end

N-terminus

beginning (amine group) of amino acid chain/primary structure

oligopeptide

composed of 2-20 amino acid residues

polypeptide

long, unbranched chain longer than oligopeptide

secondary structure

first layer of protein folding, involve backbone H bonding interactions

alpha helix

secondary protein structure

* H bonds between amino H of one amino acid and carbonyl O of another amino acid further down same strand

beta pleated sheet

secondary structure, can be antiparallel or parallel

* proline makes kinks in amino acid sequences

amyloid fibrils

caused by improperly folded beta sheets

tertiary structure

3D folding protein, results from side chain interactions

* ionic, disulfide bonds, hydrophobic interactions

quaternary structure

aseembly of multiple protein subunits together

* homo = same subunits, hetero = dif subunits

purines

nitrogenous base with 2 rings, A and G (PURe As Gold)

pyrimidines

nitrogenous base with 1 ring, C U and T (CUT the PY)

Chargaff’s rule

A-T will have same number of bases, C-G will have same number of bases

melting temperature (Tm)

50% of DNA strands denatured

annealing

2 complimentary strands reassociate with one another

major and minor grooves of DNA

binding sites for transcription factors

B-DNA

most common form of DNA, right handed in helix shape, 10.5 bp per helix turn

A-DNA

more condensed, DNA-RNA hybrid helices

Z-DNA

left handed and looser than both A and B DNA

central dogma of molecular biology

DNA → RNA → protein

messenger RNA (mRNA)

template to synthesize protein

heterogeneous nuclear RNA (hnRNA)

precursor to mRNA

transfer RNA (tRNA)

transfers amino acids to growing polypeptide chain

ribozymes

RNA molecules that have enzymatic ability

reverse transcriptase

RNA → DNA

degenerate genetic code

more than 1 codon can encode for 1 amino acid

wobble hypothesis

first 2 nucleotides are specific in codon, third is less critical

prokaryotic replication

one origin of replication, proceeds in both directions along circular bacterial chromosome

helicase

unwinds DNA at replication fork

single stranded binding proteins (ssbp)

prevent strands from reconnecting after helicase unwinds them

gyrase/topoisomerase

alleviates supercoiling by making incisions to relax the strand

DNA polymerase

adds nucleotides from 5’ to 3’, reads from 3’ to 5’

DNA ligase

connects Okazaki fragments on lagging strand

DNA polymerase I

removes RNA primer, replaces primer with DNA, repairs DNA

DNA polymerase II

repairs DNA

DNA polymerase III

synthesizes new DNA and proofreads DNA via 3’ to 5’ exonuclease activity, capable of proofreading

eukaryotic DNA polymerase

* alpha: initiates DNA synthesis
* beta: reapirs DNA
* gamma: replicates mitochondrial DNA
* delta: synthesizes new DNA and replaces RNA primer with DNA
* epsilon: extends leading strand and repairs DNA

telomerase

extends telomeres because strands would progressively shorten

telomeres

repetitive sequences at end of the strand

DNA

deoxyribonucleic acid, double stranded, 1 OH group on sugar

RNA

ribonucleic acid, single stranded, 2 OH groups on sugar

G0 phase

resting phase, nondividing

M phase

cell division occurs through mitosis/meiosis, must pass spindle checkpoint

interphase

90% of cell cycle, DNA in euchromatin (G1, S, G2)

G1 phase

cell size and volume of cytoplasm increase, organelle duplication, actively synthesizes proteins and moelcules for cell division

* cell becomes committed to cell cycle

S phase

DNA replicated

G2 phase

prepares for M phase, phase G2 checkpoint must be passed

cyclin

proteins that control progression of cell cycle by binding to cyclin-dependent kinases (CDK)

* levels are cyclical, different types correlate with particular phase

prophase

first step in mitosis, nuclear envelope disintegrates, DNA condenses into chromatin

homologous

maternal and paternal copies of same gene

metaphase

step in mitosis where chromatids and spindle fibers are organized along metaphase plate

anaphase

step in mitosis where microtubule fibers pull at the kinetochore, splits apart into 2 daughter cells

telophase

step in mitosis where nuclear envelope reforms, cleavage furrow from cytokinesis splits cells

* mediated by actin and myosin proteins

mitosis

2 daughter cells, diploid (2n)

meiosis

4 daughter cells, haploid (1n), only occurs in germ cells (sperm and egg) with 2 rounds of division

meiosis prophase I

chromosomes pair up via synapsis to form tetrad (4 sister chromatids)

crossing over

same chromosome with dif alleles exchange genetic info

* only occurs between homologous chromosomes, not chromatids

chiasmata

cross over points, results in recombinant chromosome

independent assortment

meiosis metaphase, pairs line up in random order

meiosis anaphase I

2 chromosomes of homologous pair separated, each daughter has 23 chromosomes

gonads

where germ cells are located, ovaries/testes

2 heterozygous cross

25% homozygous dominant, 50% heterozygous, 25% homozygous recessive (1:2:1)

* 75% dominant phenotype, 25% recessive phenotype (3:1)

test cross

used to predict alleles of parents based on offspring, usually performed iwth homozygous recessivedihybri

dihybrid cross

9:3:3:1 ratio, 2 traits being scanned

complete dominance

one dominant allele masks effect of recessive

codominance

2 dominant alleles can be expressed at same time (ABO blood)

incomplete dominance

blended phenotype that is intermediate of the 2 homozygous phenotypes (gradient phenotype)

penetrance

percent of individuals with given genotype who display associate phenotypeex

expressivity

severity of a phenotype