Cell biology - theme 1

Question 1

cytosol environment

Answer 1

reducing environment

Question 2

nuclear lamina

Answer 2

intermediate filaments which support the round shape of nucleus

Question 3

pH of lysosomes compared to cytosol and why

Answer 3

lysosomes are more acidic pH 5.0 than cytosol pH 7.2

for hydrolases to break down bacteria and cell debris

Question 4

autophagy

Answer 4

intracellular digestion of intracellular and extracellular matter

Question 5

amphipathic

eg

Answer 5

hydrophobic and hydrophilic

e.g. phospholipid has hydrophobic tail and hydrophilic head

Question 6

3 types of cell filaments and relative thickness

Answer 6

actin (thinnest)
intermediate filaments (intermediate thickness)
microtubles (thickest)

Question 7

actin function and found in which cells

Answer 7

cell movement (macrophages), strength (microvilli), contraction (of muscle and contractile ring in cell division)

Question 8

intermediate filaments function and found in which cells

Answer 8

mechanical strength (toughest filament) 
in cells prone to mechanical stress e.g. nerve axon, muscles, skin epithelia

Question 9

2 types of intermediate filaments
general structure
an example of each

Answer 9

nuclear (meshwork) e.g. nuclear lamina
cytoplasmic (rope like) e.g. keratin filaments in epithelial cells, vimentin in connective tissue muscle and glial cells, neurofilaments in nerve cells

Question 10

microtubules structure and function

Answer 10

hollow tubes, thickest filaments
internal cell organisation e.g. transporting, positioning organelles and vesicles, cell division
provide tracks along axon

Question 11

function of fibroblasts

Answer 11

secrete ECM e.g. collagen around themselves by exocytosis

Question 12

what does actin allow fibroblasts to do

Answer 12

move and weave collagen in different directions

Question 13

collagen I

Answer 13

long fibrils

skin, bone, tendons, ligaments, dentine, interstitial tissues

Question 14

collagen II

Answer 14

long fibrils

cartilage, vitreous humour

Question 15

collagen III

Answer 15

long fibrils (I) 
skin, muscle, blood vessels

Question 16

collagen IV

Answer 16

sheet forming collagen

connects basal lamina to basal surface of epithelial tissue

Question 17

collagen V

Answer 17

long fibrils (similar to I) 
skin, bone, foetal membranes, placenta

Question 18

elastin

Answer 18

interwoven protein with collagen

Question 19

where is there lots of ECM

Answer 19

connective tissue

e.g. tendons, bone, soft jelly in eye

Question 20

where are GAGs found

Answer 20

dentine (I), eyeball (II), gingiva and cartilage particularly in knee (II)

Question 21

function of GAGs and how tho

Answer 21

fill space with fluid for resisting compression and impact of pressure
are negatively charged polysaccharides so attract Na+
[Na+] increases so osmosis of water into connective tissue

Question 22

gene expression

Answer 22

acetylation

euchromatin

Question 23

gene silencing

Answer 23

methylation

heterochromatin

Question 24

heterochromatin

Answer 24

more tightly packed nucleosomes so silence genes

Question 25

euchromatin

Answer 25

less condensed nucleosomes, more access to DNA so genes expressed

Question 26

problem with helicase in DNA replication and how to resolve

Answer 26

helicase creates torisonal force causing supercoiling of double helix
topiosomerase creates breaks to relieve stress and open up for more supercoiling

Question 27

okazaki fragment

Answer 27

lagging strand template of replication fork
polymerase unable to add bases to 5’ end
primase adds RNA primers along new strand so bases can be added onto the 3’ end of the primer
DNA ligase attaches fragments

Question 28

function of DNA polymerase

Answer 28

add bases to 3’ end

proof reading of correct base pairing as it has a nuclease active site

Question 29

bacteria cell shapes (4)

Answer 29

cocci (spherical) e.g. stretococcus
bacilli (straight rods) e.g. ecoli, salmonella
spirillum (curved rods) e.g. vibrio cholera
spirochetes (spirals) e.g. syphilis

Question 30

all bacteria have (4)

Answer 30

peptidoglycan
cytoplasmic membrane
DNA
ribosomes

Question 31

gram positive

Answer 31

thick peptidoglycan so stains purple
has lipoteichoic acid
no outer membrane

Question 32

gram negative

Answer 32

thin peptidoglycan so stains pink
has periplasm between inner and outer membranes (enzymes)
outermembrane has porins to allow ions, sugar, aa to enter periplasm
outermembrane has endotoxin liposaccharides

Question 33

molecular phylogeny

Answer 33

study of evolutionary relationships by comparing genetic information

Question 34

growth factors

Answer 34

organic nutrients e.g. carbohydrates, amino acids, vitamins etc

Question 35

bacteria can exchange DNA in three ways

Answer 35

transformation - DNA uptake from dead bacteria

transduction - virus injects DNA integrates into bacterial chromosome, virus leaves with bacterial genes and infects other cells

conjunction - direct transfer of DNA from one cell to another

Question 36

where do bacteria live

Answer 36

biofilms

associated with ECM

Question 37

test to quantify levels of protein in sample

Answer 37

ELISA test

Question 38

test to identify specific nucleotide sequences

Answer 38

DNA hybridisation
melt to 95 oC to break H bonds
excess oligonucleotide probe (complementary base sequence to target) is labelled with flurophore/ enzyme
probes hybridise with DNA