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cell biology > semester 1 > Flashcards

semester 1 Flashcards

1
Q

what is the nucleus?

A
  • a double membrane supported by a fibrous protein mesh

- aqueous solution containing; genetic material, RNA, protein

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2
Q

why have a nucleus?

A
  • separates fragile chromosomes from cytoskeletal cytoplasmic filaments to protect it
  • separate RNA transcription (nucleus) from translation machinery (cytoplasm):
    • control over RNA processing (nucleus)- alternative splicing
    • regulation of RNA export- how fast/slow RNA is moved out of nucleus controls how rapidly protein starts to accumulate
    • enables regulation of import/export of other proteins
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3
Q

describe an ancient prokaryotic cell

A

bacillus subtilis DNA attached t cell membrane at many points

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4
Q

what’s the genetic blue print of deoxyribonucleic acid ?

A
  • nucleotides linked by covalent bonds between 5’ phosphate 3’ -OH group of deoxyribose
  • results in sugar-phosphate backbone from which bases exist. order of bases is the stored information
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5
Q

define DNA

A

a double helix, a sugar-phosphate backbone with pairs of bases protruding into the middle

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6
Q

what is a key property of nucleic acids that enable them to store information?

A

the ability to form complimentary base pairs

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7
Q

which nucleic acids pair in DNA?

A
  • T forms 2 hydrogen bonds with A

- C forms 3 hydrogen bonds with G

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8
Q

what does each base in DNA contain?

A

1 large purine and 1 small pyrimidine

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9
Q

what does “ DNA’s 2 strands are antiparallel” mean?

A

means the 2 DNA strands are exactly complementary to one another

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10
Q

how does DNA maximise efficiency of base pairing?

A

winds into a double helix, 1 complete turn per 10bp, this creates 2 grooves; the major and the minor

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11
Q

what’s the function of DNA?

A

storage of genetic information; replication, gene expression

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12
Q

why must DNA be replicated accurately?

A

to function as the hereditary molecule

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13
Q

describe DNA replication

A
  • 2 complimentary strands separate
  • each serve as a template for a new complementary strands
  • each of 2 resulting double strands is exactly same as parent
  • semi-conservative replication: each new DNA molecule contains half of the original
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14
Q

describe gene expression

A
  • regulatory (promoter) sequences say where transcription starts
  • 1 strand serves as a template for RNA synthesis
  • RNA processing to; top and tail the message (capping and polyadenylation), remove introns (splicing)
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15
Q

describe telomeres

A
  • end of chromosomes (protective)
  • 1000x GGGTTA (human)
  • special replication mechanism
  • shorten with age
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16
Q

describe centromeres

A
  • hold metaphase chromosomes together
  • attaches to mitotic spindle
  • repetitive sequence; highly packaged
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17
Q

what are nucleosomes?

A
  • made up of histone proteins
  • 2 molecules of each of 4 histone (H2A, H2B, H3, H4)
  • 146nt of DNA winds 1.65 times around histone core to form the nucleosome
  • hydrogen bonds form between DNA and histone octamer
  • each nucleosome is separated from the next by up to 80nt of linker DNA
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18
Q

describe linker DNA between nucleotides

A
  • regulatory proteins may disrupt nucleosome binding

- structural proteins result in higher level packaging

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19
Q

describe looped domains

A
  • 30nm fibre pulled into loop
  • loops fastened to a “scaffold” by proteins
  • looped domains in interphase chromatin can unwind for gene expression
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20
Q

how does packaging effect gene expression?

A
  • heterochromatin (dark); highly packaged DNA, silenced gene

- euchromatin (light); active genes

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21
Q

what is the result of further condensation producing the mitotic chromosome?

A
  • 10,000x packaging

- 2nm DNA double strand to 1400nm mitotic chromosome

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22
Q

describe the nuclear envelope

A
  • 2 concentric membranes
  • contiguous with one another but are functionally distinct
  • inner membrane attaches to the nuclear lamina and chromatin
  • outer membrane continuous with endoplasmic reticulum
  • perforated by pores-many molecules transported across; nuclear proteins in, RNA molecules out, ribosome subunits in + out
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23
Q

what do subunits contain?

A

repeats of phenylalanine and glycine amino acids

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24
Q

what is the key required for nuclear transport known as?

A

nuclear localisation signals (NLS), rich in positively charged amino acids; Arg, Lys, Pro

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25
Q

why does nuclear import require import receptor proteins

A
  • import receptors (importins) bind to NLS of cargo + to FG repeats of the nuclear pore complex
  • passes from 1 subunit to the next
  • eventually reaches the nucleus
  • complex dissociates in the nucleus
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26
Q

how is nuclear import regulated?

A

some proteins always need to be nuclear, others only in response to specific signals
eg. nuclear receptors are transcription factors turned on by hormones
eg chemical binding, phosphorylation, release of chaperones, unmasking of the NLS

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27
Q

describe the nuclear lamina

A
  • enmeshed between 2 networks of intermediate filaments
  • next to inner membrane
  • 2D lattice of fibres called intermediate filaments
  • provides support + organisation
  • made of proteins called Lamins
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28
Q

describe lamin structure

A
  • globular head ends

- rod-like central domain-helix

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29
Q

how does lamina attach to the membrane?

A

lipid like anchor on COOH terminus of each lamin attaches lamina to inner nuclear membrane between phospholipids

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30
Q

what are ribosomes?

A
  • 2 main subunits large(60s) and small(40s)
  • s = svedberg unit a sedimentation co-efficient
  • measure of how quickly a particle/molecule sediments
  • big particles sediment more quickly and have higher s values
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31
Q

how do ribosomes compare between prokaryotes and eukaryotes?

A

in prokaryotes there are only 2 ribosomal RNA making up large subunit rather than 3 and there is one making up the smaller. slightly fewer proteins making up these subunits compared to eukaryotes

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32
Q

what are the components of ribosomes?

A

an RNA core with proteins attached mainly to the surface

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33
Q

what are the 3 components of ribosome synthesis?

A
  • rRNA synthesis + processing
  • ribosomal proteins- transcription, translation
  • ribosomal subunits, assembly
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34
Q

describe RNA synthesis and nucleolus

A
  • occurs in nucleolus, discrete area within nucleus with no additional membrane
  • forms around parts of chromosomes (nucleolar organizers)
  • site of ribosomal subunit production
  • 10^6 ribosomes in each cell
  • multiple copies of rRNA genes to produce rRNA
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35
Q

describe the nucleolar organiser

A
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36
Q

describe large subunit of a ribosome

A
  • made from 2000 5s rRNA genes in 1 cluster on a chromosome not part of nucleolus organiser
  • transcribed by RNA polymerase III
  • length = 120nt
  • 5s rRNA transported to nucleolus for assembly
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37
Q

describe ribosomal proteins

A
  • ~55 structural proteins
  • transcribed by RNA polymerase II then translated in cytoplasm
  • transported into nucleus where they can be taken to the nucleolus for assembly into those ribosomes
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38
Q

how many bases are needed to encode 20 amino acids?

A

3 bases required to code for a single amino acid, triplet code gives 64 possibilities- enough for 20 amino acids, + stop codons

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39
Q

give 3 steps of translation

A
  • codon recognition
  • peptide bond formation
  • release of empty tRNA, important because otherwise next amino acid cannot be attached to growing chain
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40
Q

describe peptide bond formation

A
  • condensation reaction

- catalysed by ribosome called ribozyme

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41
Q

explain initiation of translation

A
  • small subunit with tRNA binds and scans for first AUG then large subunit binds and done
  • 3 binding sites, only 2 taken up by tRNA
  • small subunit only attracts large subunit when methionine codon is recognised by anticodon in tRNA
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42
Q

what are the stop codons?

A

TAG, TAA, TGA

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43
Q

explain terminating translation

A
  • specific set of codons that code for stop means get release factor binding
  • once release factor binds to A site, no more binding to that site of tRNA, means that when large subunit moves forward there’ll be no additional tRNA’s present for extension of polypeptide chain
  • as front moves forward tRNA is moving into E site which will move it up away from the mRNA and dislodge it so no more base pairing is occurring + then it’s displaced from ribosome
  • ribosome then dissociates and tRNA drifts off
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44
Q

why is it important to remove misfolded proteins?

A

protein aggregates are a feature of progressive neurodegenerative diseases eg. Alzheimer’s, Huntington’s

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45
Q

explain protein turnover

A
  • The proteasome is an ATP-dependent protease
  • Abundant ~1% of the total protein
  • Hollow tube of many subunits including multiple proteases which face inwards
  • Multi-subunit cap structures at either end act as the gateways
  • The cap has ATPase activity, thought to unfold the target protein
  • The substrate is retained in the tube until munched
    into short peptides
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46
Q

how is protein degradation controlled?

A
  • Ubiquitin, a short peptide, can be attached to the NH2 side chains of lysine residues in proteins targeted for degradation
  • It is activated by binding to Ubiquitin Activating Enzyme (E1) which then transfers it to Ubiquitin Ligase (E2/E3 complex)
  • E2/E3 recognises the protein targeted for degradation and transfers Ub to it
  • Further Ub molecules are added by E1
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47
Q

how is protein degradation controlled?

A
  • Ubiquitin, a short peptide, can be attached to the NH2 side chains of lysine residues in proteins targeted for degradation
  • It is activated by binding to Ubiquitin Activating Enzyme (E1) which then transfers it to Ubiquitin Ligase (E2/E3 complex)
  • E2/E3 recognises the protein targeted for degradation and transfers Ub to it
  • Further Ub molecules are added by E1
  • Multiple ubiquitin chains are the signal for degradation by the proteasome
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48
Q

what doe ER look like?

A
  • membranous labyrinth
  • contiguous tubules + sacs, they’re still part of and connected to nuclear envelope
  • ER lumen bounded by ER membrane
  • ER membrane is contiguous with outer nuclear membrane
  • can constitute >10% of cell volume and up to 60% of cell membrane
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49
Q

describe rough ER

A
  • ribosomes make it rough

- ribosomes are making; secretory proteins, transmembranous proteins, ER and golgi proteins, lysosomal proteins

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50
Q

describe the production of secreted proteins

A
  • small subunit bind to mRNA once it finds AUG
  • large subunit starts generating protein
  • mRNA encoding cytosolic protein translated by polyribosomes in cytosol
  • common pool of ribosomal subunits in cytosol
  • mRNA encoding ER-targeted protein translated by polyribosomes attached to ER membrane by multiple nascent chains
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51
Q

describe the process of targeting protein production to RER

A
  • single peptide is hydrophobic or lipophilic amino acid and sticking out
  • recognition of single peptide by signal recognition particle (SRP) which pauses translation + then allows SRP t interact with SRP receptor in ER membrane. causes disengagement of SRP with ribosome
  • ribosome moves to protein translocator + translation starts to occur
  • polypeptide chain extends + that SRP gets stuck within protein translocator + stays there anchoring ribosome to protein translocator
  • as it hops up + down it keeps on translating mRNA into a polypeptide chain which is then released into ER lumen
  • meanwhile SRP and SRP receptor still on ER membrane are released allowing translation to restart
  • then disengagement of receptor from particle. receptor stays in ER lumen + recognition particle goes back to floating in cytoplasm
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52
Q

what is the fate of soluble proteins within the RER?

A

-protein will get cut off once it gets to the c terminal end + end up with signal peptide in the ER membrane and it will cut off that growing polypeptide chain, left with soluble peptide in the ER lumen

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53
Q

what is the fate of membrane bound proteins within the RER?

A

signal peptide part of way through amino acid chain, meaning ribosome only directed to protein translocator by signal recognition peptide part of way through translational process. means signal peptide still remains bound to protein translocator + protein gets fed through but not all of it

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54
Q

what is the fate of N-linked glycosylation within the RER?

A
  • almost all proteins synthesised into RER are glycosylated
  • by a 14 sugar modification added to sequence (Asn-X-Ser/ Asparagine)
  • precurser oligosaccharide is assembled onto special lipid molecule called phosphodolichol found in ER membrane + transferred to elongating peptide chain by membrane bound oligosaccharyl transferase enzyme found only in ER lumen
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55
Q

describe membrane synthesis

A
  • new phospholipids assembled in outer leaflet of ER membrane causes membrane to start to expand on 1 side of membrane
  • assembled by membrane bound enzymes which combine components
  • scramblase is a phospholipid translocator which causes 2 leaflets to equilibrate by flipping phospholipids from outer side of ER membrane onto inner membrane
  • new phospholipids carried to golgi then to plasma membrane or lysosomes and endosomes by vesicular transport
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56
Q

describe smooth ER

A
  • no ribosomes
  • in most cells
  • present between RER and golgi
  • specific roles
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57
Q

describe steroid hormone synthesis in SER

A
  • cholesterol main sterol generated in liver + has characteristic steroid ring, it has 4 which makes it inflexible but has tail a tail at bottom, can be made into testosterone
  • SER is expanded to accommodate for enzymes which make and modify cholesterol
  • eg testosterone is synthesised from cholesterol in abundant SER of leydig cells of testes
58
Q

explain detoxification of drugs and the smooth ER

A
  • occurs in hepatocytes of liver
  • cytochrome P450 attached to membrane + they’re able to modify these lipophilic drugs that are able to move straight through the plasma membrane into cell
  • they modify them to make them more hydrophilic, so they can be more easily dissolved within aqueous environment eg makes them more water soluble so can be excreted in kidney
  • further modification can occur in cytosol, before excretion from body in bile or urine
  • hepatocytes have large chunks of SER to enable them to have lots of copies of cytochrome P450+ they’re required for the metabolism of these drugs
  • hepatocytes are major producers of lipoproteins
  • cellular adaptation is to expand smooth ER membrane to enable cells to carry out expected functions
59
Q

describe the sarcoplasmic reticulum

A
  • occurs in muscle cells and acts as a calcium store in muscles
  • under resting conditions, high calcium ion conc. present within SER because calcium pumps closed
  • when action potential from nerve depolarises plasma membrane, voltage sensitive protein channels open + all allow movement of calcium into cell
  • rise in cytosolic calcium stimulates muscle contraction
  • process can revert back to closing of calcium channels
60
Q

describe the interphase

A
  • cell grows- doubling protein content
  • organelles double in size or number
  • during s-phase DNA synthesised
  • centrosome (microtubule organising centre) replicates
  • 2 gaps (G1 + G2) exist during which cell checks that everything is ready for the next phase
61
Q

what are the stages in order of the M-phase?

A
  • prophase
  • prometaphase
  • metaphase
  • anaphase
  • telophase
  • cytokinesis
62
Q

describe prophase

A
  • chromosomes condense
  • mitotic spindle (microtubules + associated proteins) forms
  • centrosomes move apart
  • protein complex (kinetochore) forms at centromere of the chromosome
63
Q

describe prometaphase

A
  • nuclear envelope breaks down which allows microtubules access to microtubules
  • chromosomes attach to microtubules via kinetochore complex
64
Q

describe metaphase

A
  • chromosomes align at equator

- sister chromatids attach to opposite poles by kinetochore microtubules

65
Q

describe anaphase

A
  • cohesive link between sister chromatids released
  • kinetochore microtubules shorten
  • centromeres move apart
  • all resulting in sister chromatids simultaneously pulled to opposite poles
66
Q

describe telophase

A
  • daughter chromosomes reach poles
  • new nuclear envelope forms from fragments attached to individuals chromosomes. therefore 2 nuclei
  • contractile ring begins to form around equator
67
Q

describe cytokinesis

A
  • ring contracts partitioning cytoplasm into 2 daughter cells
  • each cell contains; 1 nucleus, 1 centrosome, a share of all organelles
  • DNA decondenses and cells return to resting interphase (G1)
68
Q

explain relationship between the cell cycle and the cytoskeleton

A
  • mitosis is a time of increased instability in cytoskeleton
  • motor proteins play role in moving various components around
  • nuclear lamina (intermediate filaments) needs to disassemble prior to onset of mitosis
  • actin cytoskeleton involved in ring contraction during cytokinesis
69
Q

what is kinetochore microtubules role in the cell cycle?

A
  • attach to chromosomes
  • during prometaphase they grow and shrink as grope to find a target
  • during metaphase motor proteins (+ & -) pull chromosomes around until aligned
  • during anaphase they shorten and motor proteins move chromatids towards centrosome
70
Q

how is the cell cycle controlled?

A

crucial that each step;

  • occurs at right time
  • occurs only once per cycle
  • goes to completion
71
Q

what are the 3 checkpoints to ensure successful mitosis?

A
  • restriction point (end of G1), environmental check (growth factors, nutrients, cell size), DNA damage check. if cell doesn’t pass checkpoint it’ll withdraw from cell cycle and remain in quiescent state
  • G2-M transition, environment check (size), DNA damage check, replication complete
  • meta-anaphase transition, chromosomes attached to spindle
72
Q

what are cyclins?

A

needed to turn on cyclin dependant kinases (CDKS), levels of cyclins rise and fall during cell cycle

73
Q

give an example how cdk-cyclin complexes regulate transition through different stages of cell cycle

A

M-Cdk regulates G2-M transition (active)+ meta-anaphase transition

74
Q

what is meant by cyclin levels oscillate?

A

induction of cyclin protein expression vs. protein degradation

75
Q

describe cyclin levels oscillating

A
  • anaphase promoting complex; a ubiquitin ligase which targets the M-cyclins for degradation
  • SCF complex ubiquitinates the G1/s-cdk complex
  • at end of mitosis all cdk rests to zero
76
Q

what are microtubule accessory proteins?

A

increase microtubule instability chromosome condensation complex is activated by M-cdk

77
Q

what are the products of meiosis and their roles?

A
  • progeny cells have half number of chromosomes than parent cells had
  • cells are the gametes required for sexual reproduction
78
Q

what do 2 gametes fusing form?

A

a diploid gamete

79
Q

what are germ-line cells?

A

the only cells that can undergo meiosis the rest of cells that can’t are called somatic cells

80
Q

define haploid number

A

one copy of each chromosome

81
Q

define diploid number

A

2 copies of each chromosome (except sex chromosomes in males)

82
Q

how many chromosomes do the majority of cells in humans contain?

A

diploid number (46) of chromosomes

83
Q

how many chromosomes do mature gametes contain?

A

23, the haploid number

84
Q

why is sexual reproduction important?

A
  • opportunity to mix traits of both parents to produce genetically distinct offspring, some may have selective advantage
  • recombination further increase possibilities
  • fertilisation of eggs by sperm produces a diploid zygote which develops via mitotic division, differentiation + apoptosis into a mature organism
85
Q

define homologous chromosomes

A

a set of one maternal and one paternal chromosome

86
Q

describe interphase 1

A

DNA replicates; pairs of chromatids

87
Q

describe prophase 1

A
  • leptotene; condense
  • zygotene; homologous chromosome align + linked by synaptonemal complexes
  • pachytene; pairs of chromosomes coil; crossing over (recombination)
  • diplotene; synaptonemal complexes break down; pairs of chromosomes linked at crossover points (chiasmata)
  • diakinesis; chromosomal condensation reaches maximum
88
Q

describe necrosis (type of cell death)

A
  • accidental death following acute insult
  • cells swell + burst
  • contents release + cause inflammation
89
Q

describe programmed cell death

A
  • eg apoptosis
  • cells die in an organised manner + are engulfed + digested
  • requires ATP
  • no inflammation
90
Q

what are some examples of why we need programmed cell death?

A
  • in frog, regression of tadpole tail
  • in brain formation of connections between neurons requires surplus cells be eliminated by apoptosis
  • to destroy cells that represent a threat to integrity of organism eg; -cells infected with virus of cells with DNA damage
91
Q

what are the features of apoptosis?

A
  • cell surface “bleb” appearance
  • shrinkage of cell and nucleus
  • cleavage of nuclear DNA
  • condensation of chromatin
  • nucleus fragmentation
  • cleavage of cytoskeleton
  • signals on outside cause cell to be engulfed by its neighbours or macrophages
92
Q

what is the caspase cascade?

A
  • caspases are cell death proteases
  • synthesised as inactive pro-caspases
  • activated by each other by cleavage
  • small numbers of initiator caspase activate a cascade generating lots of effector (executioner) caspases
  • these cleave cellular components eg. nuclear lamina, activate DNases
  • activation is complete and irreversible, therefore tight regulation is crucial
93
Q

what sets of the caspase cascade?

A

intrinsic pathway;
-switched on by damage or stress
-damaged mitochondria release cytochrome C (electron carrier)
-cytochrome C in cytoplasm activates one of the initiator caspases which activates a cascade
extrinsic pathway;
-proteins from other cells bind to death receptors on cell surface
-death receptors aggregate and cause caspase 8 to be cleaved, which activates the cascade

94
Q

define wavelength

A

distance between the tip of 2 neighbouring waves

95
Q

what is the wavelength of radiation for different microscopy?

A

-light microscopy: visible light (400-700nm)
-fluorescence microscopy: uv light (200-400nm)
-electron microscopy: electron waves (0.01-0.001nm, 100,000 times smaller than visible light
-

96
Q

describe magnification

A
  • apparent increase in size of an object
  • beam of radiation refracts as is passes through a lens; glass lenses refract light, magnetic lenses refract electron beams
97
Q

why does light bend when passing through glass lens?

A

because glass has a higher optical density than air, so light travels slower through glass

98
Q

what factors can affect the ability to magnify an object by a convex glass lens?

A
  • thickness of lens
  • curvature of lens
  • speed of light in lens
99
Q

describe resolution

A
  • ability to distinguish between objects that are close together
  • smallest distance between 2 particles at which they can be seen as separate objects
100
Q

what’s max resolution of a light microscope?

A

200 nm (0.2 micrometres)

101
Q

what’s max resolution of electron microscope?

A

0.0078nm

102
Q

what is the equation for resolution distance?

A

(0.61 x wavelength) / numerical aperture

103
Q

what is numerical aperture

A

ability of an objective to collect light

104
Q

why does oil increase resolution

A

stops light from refracting

105
Q

describe contrast

A
  • differences in intensity between 2 objects, or between an object and its background
  • important in determining resolution
  • staining increases contrast
106
Q

what can a light microscope be used with?

A

live unstained cells and fixed stained specimens

107
Q

what are the components of a light microscope?

A
  • ocular lens (eyepieces): remagnifies the image formed by objective lens
  • body: transmits image from objective lens to ocular lens using prisms
  • objective lenses: primary lenses that magnify specimen
  • stage: holds microscope slide in position
  • condenser: lens focuses light through specimen
  • diaphragm: controls amount of light entering condenser
  • illuminator: light source
  • course focusing knob: moves stage up and down to focus image
  • fine focusing knob: sharpens image
108
Q

what’s the equation for total magnification?

A

magnification of objective lens x magnification of ocular lens

109
Q

describe fluorescent microscopes

A
  • fluorescent substances absorb uv light and emit visible light
  • used to identify cells and cellular components with high degree of specificity
  • can be used with fixed or live cells and tissue
110
Q

what is the excitation filter? (fluorescence microscope)

A

selects only wavelength that excites a particular fluorescent dye

111
Q

what is emission filter? (fluorescence microscope)

A

selects only wavelength emitted by fluorescent dye

112
Q

describe electron microscopes

A
  • study subcellular structures (100 micrometre- 1nm)
  • uses electrons rather than light
  • shorter wavelength of electrons gives greater resolution
  • very high magnification (100,000x)
  • samples are fixed + stained or coated with electron dense material eg gold
113
Q

what is the aim of fixation?

A
  • preserves cells + tissue components maintaining their natural structure
  • prevents degradation caused by autolysis and bacterial attack
  • fixation makes cells permeable to staining reagents
114
Q

what is chemical fixation?

A
  • use of cross-linking chemicals (formalin, glutaraldehyde)

- dehydration reagents (ethanol, methanol) denature, precipitation

115
Q

what is physical fixation?

A

freezing at -70 degrees Celsius

116
Q

what is embedding?

A
  • infiltrate fixed specimen with medium that hardens and supports tissue for sectioning
  • eg paraffin wax + resin
117
Q

describe the steps of embedding with paraffin wax

A
  • dehydration, removal of water from tissue
  • clearing, replacement of alcohol with xylene, tissue ready for embedding medium infiltration
  • embedding, tissue infiltrated + surrounded with liquid wax, wax solidified by coding or polymerization
118
Q

describe sectioning

A
  • samples that have been embedded in paraffin wax, sectioning is done using microtome that can cut sections of ~ 4-10 micrometres
  • if tissue has been fixed by freezing + has been embedded in cryoprotective medium its sectioned using a cryostat (-20 degrees Celsius), sections ~ 10-20 micrometres and stored at -80 degrees Celsius
119
Q

why is staining needed?

A
  • to reveal cells + their components
  • adds contrast to image
  • identify chemical components of interest
  • locate particular tissues, cells or organelles
120
Q

describe the staining method immunohistochemistry

A

-antibodies to detect specific proteins
-antibody-antigen specific interaction
-antibodies conjugated with fluorescent dye
direct; conjugated primary antibody
indirect; primary antibody + conjugated secondary antibody

121
Q

describe the staining method histochemistry

A
  • identification of macromolecules (DNA, RNA, carbohydrates, lipids) + chemicals compounds in cells + tissues using dyes
  • periodic acid schiff; detect carbohydrate macromolecules such as glycogen, and mucosubstances such as glycoproteins + glycolipids in tissues
  • periodic acid oxidises sugars + exposes aldehyde groups
  • aldehyde groups react with the schiff reagent to give purple- magenta colour
122
Q

describe the staining method histology

A
  • uses organic dyes with affinity for particular subcellular components
  • affinity depends on physico-chemical properties of dyes
  • haematoxylin, basic dye binds acidic components of cells: nuclear DNA + RNA
  • eosin, acidic dye binds basic components: proteins in cytoplasm
  • masson’s trichrome; identify and quantity fibrous tissue (collagen), aniline blue; collagen blue, bieblich scarlet; cytoplasm red, haematoxylin; nuclei dark blue
123
Q

what is epithelial tissue?

A

continuous layer of closely packed cells that covers the external body surface and lines body cavities and generally marks off our insides from our outsides

124
Q

where is epithelial tissue?

A

covers all internal+ external surfaces: skin, mouth, blood vessels, stomach, lungs, liver etc

125
Q

what are the 2 types of epithelial tissue?

A
  • epithelia, layers of cells covering internal or external surfaces
  • glands, structures that produce secretions
126
Q

what are the functions of epithelial tissue?

A
  • provide physical protection
  • control permeability
  • provide sensation
  • absorb nutrients
  • secretion
  • transport(ciliated epithelia sweep mucus, cells and other particles along the surface of the epithelium
127
Q

describe polarity as a characteristic of epithelial tissue

A
  • below epithelial cells is basement membrane
  • below basement membrane is connective tissue
  • epithelial cells have apical surface
  • basal surface is where epithelial cells come into contact with basement membrane
  • apical surface can be smooth and contains microvilli or cilia
  • microvilli increase SA by 20x increasing absorptive capacity, cilia help move materials
128
Q

describe specialised contacts as a characteristic of epithelial tissue

A
  • refers to cell junctions; tight junctions, desmosomes + gap junctions
  • cell junctions provide strength + impermeability by linking one epithelial cell with the neighbouring one + so prevent space between cells
129
Q

describe attachment as a characteristic of epithelial tissue

A
  • basement membrane made up of basal lamina + reticula lamina
  • basal lamina; glycoproteins secreted by epithelial cells, selective filter for molecules between connective tissue + epithelium
  • reticular lamina: layer of extracellular material (collagen) produced by connective tissue, gives basement membrane its strength
130
Q

describe avascularity as a characteristic of epithelial tissue

A

-no blood vessels: nutrients arrive by diffusion from blood vessels in connective tissue

131
Q

describe regeneration as a characteristic of epithelial tissue

A
  • epithelial tissue has high regenerative capacity, can reproduce rapidly
  • epithelial cells have hard life: exposed to mechanical friction, disruptive enzymes, toxic chemicals + bacteria
  • regeneration is essential to maintain tissue integrity and is achieved via cell division from stem cells
132
Q

what are stem cells?

A
  • undifferentiated cells (not committed to a specific cell type/ function)
  • self renewable (able to go through numerous cycles of cell division while still maintaining their undifferentiated state)
  • after division, each daughter cell has a choice: it can either remain a stem cell or it can embark on a course that commits it to terminal differentiation
  • different tissues have different regenerative capacity: high in epithelial tissue; very low in cardiac + nervous tissue
133
Q

what are glands?

A
  • specialised epithelial tissue structures that secrete substances
  • secretion; mucin- goblet cell, hormones- thyroid + adrenal glands, enzymes- pancreas, electrolytes + waste products- sweat gland
  • secretion is active process: glandular cells obtain substances from blood and transform them chemically into secretion product
  • glandular epithelial cells have prominent ER, golgi apparatus + secretory granules
134
Q

how are glands classified?

A
  • by site of product release- endocrine (internally secreting) or exocrine (externally secreting)
  • relative number of cells forming gland- unicellular or multicellular
135
Q

describe endocrine glands

A
  • secrete products hormones directly into extracellular space (by exocytosis)
  • hormones enter blood or lymphatic fluid + travel to target organs
  • target organs respond in some characteristic way
  • ductless glands: secretions not released into a duct
  • eg thyroid gland
136
Q

describe exocrine glands

A
  • secrete their products onto body surfaces (skin) or into body cavities
  • more numerous than endocrine glands
  • secrete products into ducts (except for goblet cells - unicellular glands)
  • unicellular or multicellular
  • eg sweat + salivary glands, liver, pancreas
137
Q

describe the unicellular exocrine gland: goblet cell

A
  • found in epithelial linings of digestive + respiratory tracts
  • produce mucin: complex glycoprotein that dissolves in water to form mucus
  • in digestive tract: mucus blocks microorganism, toxins, bacteria, digestive enzymes
  • in respiratory tact: mucus traps dust particles, bacteria + other inhaled debris, cilia move mucus towards pharynx to be swallowed- protects lungs from infections
138
Q

describe multicellular exocrine glands

A
  • composed of a duct and a secretory unit (secretory cells)
  • formed by invagination of epithelium into underlying connective tissue
  • connective tissue provides support + nutrients to glands
  • classified by modes of secretion
139
Q

describe modes of secretion of exocrine glands

A
  • merocrine glands- most secrete products by exocytosis
  • apocrine lands- a portion of plasma membrane buds off the cell, containing the secretion (mammary gland)
  • holocrine glands- the entire cell disintegrates to secrete its product (sebaceous gland)
140
Q

what are the roles of adult connective tissue?

A
  • binding + supporting
  • protecting
  • insulating
  • storing reserve fuel
  • transporting substances within body
141
Q

what is connective tissue?

A
  • encompasses all organs and body cavities + connects one part with another, but equally acts as a separator aswell + will separate 1 group of cells from another
  • comes from mesoderm, which is one of 3 primary germ layers in very early embryo
  • other layers; ectoderm which is outer layer and endoderm which is inner layer
  • mesoderm made up of mesenchyme, which is a loosely organised, mainly mesodermal embryonic tissue which will develop into connective + skeletal tissues
  • mesoderm + mesenchyme within it will differentiate into; bone, cartilage, connective tissue, adipose tissue
142
Q

what is the extra- cellular matrix (ECM) composed of?

A
  • collagen fibrils, strength
  • elastic fibres, stretch
  • ground substance, mechanical support, holds water
  • adhesion proteins, links between cells + ECM
  • basal laminae, sheet underlies/ surrounds many cell types

cell biology (1 decks)

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