what are the components of basic cells theory?

all living organisms are made out of cells, the cell is the basic structural unit in organisms, all cells arise from cell division

what is cohesion?

the glue that holds the sister chromatids together

features of phase contrast microscopy

good for observing live, unstained transparent cells

features of differential interference contrast (DIC) microscopy

good for observing live, unstained transparent cells like phase contrast but more of a 3D image and better resolution

features of transmission electron microscopy (TEM)

for very small structures, high magnification, used to study internal structures of a sample, cells are fixed- not live

features of scanning electron microscopy (SEM)

used to examine surface details of a sample, cells are fixed- not live

features of fluorescent microscopy

specific molecules are visible, multiple labels possible, can do live imaging

what are the bonds in DNA and where are they?

the 5’ carbon of the new nucleotide bonds the the 3’ carbon of the strand via a phosphate bond. the bases bond with hydrogen bonds

which are the two larger bases in DNA?

the purines - adenine and guanine

how many bonds between AT and GC?

AT = 2 hydrogen bonds, GC = 3 hydrogen bonds

why do cells have chromosomes?

to fit DNA into a cell nucleus, to avoid tangling and breaking DNA, so after replication DNA is equally divided

what is the structure of chromosomes?

telomere at the top and bottom, p arm (always shorter arm), centromere, and q arm

what is the name of a chromosome with two arms the same length?

metacentric

what is the name of a chromosome with one long and one short arm?

submetacentric

what is the name of a chromosome with only one visible arm and what number are these human chromosomes?

acrocentric, humans have 5 autosomal- 13, 14, 15, 21, 22

mitochondria make their own..

DNA, RNA and proteins

what are some features of mitochondrial DNA?

has its own genome, circular double stranded DNA, 16,500 kb long, 37 genes coding for rRNA, tRNA, proteins

what is semi-conservative DNA replication catalysed by?

(DNA-dependent) DNA polymerase

what does helicase do?

uses ATP to break the hydrogen bonds

what does topoisomerase do?

breaks DNA, unwinds then fixes the break to stabilise the DNA

what does primase do?

generates an RNA primer 10-30 nucleotides

what does DNA polymerase do?

joins nucleotides together, proof-reads as it moves along

how many DNA nucleotides does the human genome contain?

3 billion

what percentage of the genome codes for proteins

1%

how many genes does the human genome have?

nearly 20,000

what is the start of a gene called?

the promoter sequence

what is the TATA box?

a region of the promoter where the transcription factors bind

which strand does RNA polymerase use in transcription?

template strand (3’ to 5’) so the RNA is synthesised in the 5’ to 3’ direction

what are regulatory elements?

enhancers and repressors which are upstream or downstream DNA sequences which bind to specific transcription factors and change the amount of RNA being made- loop over and interact with the promotor

when do regulatory elements control gene expression?

during development and differentiation and the response of cells to hormones and growth factors

what does each RNA polymerase do?

I transcribes rRNA, II transcribes mRNA and small regulatory RNAs, III transcribes small RNAs such as tRNA

what is a termination signal?

a sequence in the DNA that signals for the transcription complex to dissociate from the DNA

why is DNA used for the genome and RNA for transcription?

DNA is for storage, is highly stable, needs to be copied. RNA is to get genetic information to the cytoplasm to make proteins but stop when we don’t need them to allow environmental adaption (highly dynamic, responsive process)

when is the chemical difference between DNA and RNA?

DNA has a H (stability) where RNA has an OH (flexability)

what is alternative splicing?

the various combinations of exons which generates different protein sequences

what is mRNA processing?

the addition of a 5’ cap and 3’ polyA tail to protect degradation of the RNA, facilitate transport out of the nucleus and the stabilise the mRNA

what is involved in translation initiation?

at least 10 proteins- eukaryotic initiation factors (eIFs) help the 40s subunit find the mRNA and dissociate when the 60s subunit binds

how does translation termination work?

when a stop codon is reached, a release factor binds to the A site which hydrolyses the bind between the polypeptide chain and the tRNA; the chain is released from the P site. the remaining parts of the translation complex dissociate

why are the 5’ and 3’ untranslated regions (UTRs) important?

to initiate and regulate the speed of translation

what are the three types of filaments?

actin (microfilaments), intermediate filaments, microtubules

what are the functions of actin/microfilaments?

stabilise the cell membrane, cell protrusions (microvilli, pseudopedia, lamellipodia, filopodia), cell migration, cytokinesis contractile ring, muscle contraction

what are the types of intermediate filaments?

keratin, lamin, vimentin, neurofilament

what are the anchoring sites of the cytoskeleton parts?

actin- focal adhesions and adherens junctions, intermediate filaments- desmosomes and hemidesmosomes, microtubules- centrosome (MTOC)

what is the structure of microtubules?

alpha- and beta-tubulin dimers with a plus (GTP bound) and minus (GDP bound) end

what is the structure of actin filaments?

made by joining G actin subunits together, they have a plus end (actin bound to ATP) and a minus end (ADP actin)

what is the difference between filopodia and lamellipodia?

filopodia- finger like extensions, lamellipodia- sheets that follow behind the filopodia and draws the cell forwards

what is pseudopodia?

temporary arm like extensions of the cell membrane to engulf bacteria (phagocytosis)

what is the role of microtubules in mitosis?

metaphase- the MT spindle aligns the chromosomes, anaphase- DNA separated by shortening MT

what are the microtubule motor proteins?

kinesin moves towards + end (anterograde) dynein moves towards - end (retrograde)

what is the length stability of each cytoskeleton component?

actin = dynamic, intermediate filaments = more stable, microtubules = very dynamic

what is the polarity and motor ends of each cytoskeleton component?

actin- polarity via ATP-actin, +end motor is myosins. intermediate filaments- no polarity or motor ends. microtubules- polarity via GTP-tubulin, +end motor is kinesins, -end motor is dyneins

what are the parts of the extracellular matrix?

epithelial cells, basal lamina, connective tissue, blood vessel, fibroblasts

what are the functions of the extracellular matrix?

attaching tissue layers, signalling via ECM receptors, enclosing organs, attaching muscles, skeleton

what does collagen have to do with scurvy?

caused by lack of vitamin C with is needed for the activity of prolyl hydroxylase (turns proline into hydroxyproline) more than 10% of collagen amino acids are hydroxyproline

what is significant for basement membrane?

trimer called laminin- makes a meshwork with collagen IV fibres (the basal lamina)

what are polysaccharides made up of?

chains made of sugar dimers called glycosaminoglycans (GAGs)

what are proteoglycans?

polysaccharides joined to a core protein

what is the primary defect in sanfillipo syndrome?

lysosome failure due to buildup of heparan sulfate

what are the types of cell junctions?

tight junctions, adherens junctions, desmosomes, gap junctions, hemidesmosomes

what are tight junctions?

most apical, make a watertight barrier

what are adherens junctions?

made of cadherins (transmembrane molecule) which connects cortical actin between adjacent cells. (on the inside surface they are attached to actin filaments, hold epithelial layers together) they regulate cell signalling and cell division

what are desmosomes?

connect intermediate filaments between adjacent cells with desmocollin and desmoglein (basically cadherens), primary function is structural stability

what are hemidesmosomes?

attach cells to basement membrane, (connect intermediate filaments to basal lamina). have adhesion molecules (integrins) which bind ECM molecules like laminin and collagen

what are gap junctions?

pores that connect the cytoplasm of adjacent cells, made by connexons, vital for passing currents (small things, not proteins)

what are integrins?

transmembrane receptor proteins on the surface of cells that mediate their adhesion to other cells and the ECM, exist as a heterodimer (one alpha and beta integrin)