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XIA BIOSCI107 > BIOSCI MOD2 > Flashcards

BIOSCI MOD2 Flashcards

1
Q

What is cell theory

A
  1. Alllivingorganismsarecomposedofoneormorecells
  2. Thecellisthebasicunitofstructureandorganisation
  3. Allcellsariseonlyfrompre‐existingcells
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2
Q

what are 3 universal things about cells?

A
  1. DNAastheheritablematerial,RNAasanintermediaryor
    messengerandproteinsastheworkers
  2. Majorcellularorganelles‐ functionsandarrangements
    withinthecell
  3. ATPasanenergysource
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3
Q

What do both prokaryotes and Eukaryotes have?

A

Bothhave:
Plasmamembrane,cytosol,
DNA,RNA,proteinand
ribosomes

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4
Q

What is the main difference between Eukaryotes and Prokaryotes?

A 
Eukaryoticcellshave
membrane‐boundorganelles
andaremuchlarger
Prokaryotecellslacka
membrane‐boundnucleus
Eukaryoticcellshave
membrane‐boundorganelles
andaremuchlarger
Prokaryotecellslacka
membrane‐boundnucleus
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5
Q

What is the definition of a cytoplasm?

A

Thecytoplasmiseverythinginsidetheplasmamembrane including
theorganelles,butnotincluding thenucleus

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6
Q

What is the cytosol?

A

The fluid portion of the cytoplasm is the cytosol-water plus dissolved and suspended substances

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7
Q

What is the plasma membrane

A

Theplasmamembraneisaselectivelypermeablebarrier
controllingthepassageofsubstancesinandoutofthecell

it is a physical barrier separating the inside and the outside of the cell

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8
Q

What is a phospholipid

A

hydrophilicpolarheads(phosphate)
• hydrophobiclipidtails(fattyacids)
• arrangedasadoublelayeraroundcytoplasm,tailtotail

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9
Q

What are plasma membrane proteins

A

they are the membrane proteins that mediate movement of hydrophilic substances
membrane proteins often have both hydrophobic and hydrophilic regions

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10
Q

What are integral proteins?

A

plasma membrane proteins embedded (partiallyorfully)

intothemembrane

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11
Q

what are transmembrane proteins

A 
plasma membrane proteins
integralmembraneproteinsthat
fullyspantheentiremembrane,
contactextracellularand
cytoplasmicareas
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12
Q

What are peripheral membrane proteins

A

associatedwiththemembrane,

butnotactuallyembeddedinit

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13
Q

What is the point of plasma membrane proteins generally,(4)

A

allowcell‐cellidentificationandfacilitateintercellularcommunication

1) transport
2) enzymatic activity-carry out chemical reaction-may/may not be part of enzymes
3) signal transduction-external signalling molecule causing relay of infor to interior-usually a signal cascade
4) cell-cell recognition
5) intercellular joining
6) attachment to the cytoskeleton and the extracellular matrix

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14
Q

fluid mosaic model

A

themembraneismosaicofproteinmolecules

bobbinginafluidbilayerofphospholipids

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15
Q

Nucleus facts

A 
Thelargestdistinctstructureinsidethecell
Enclosedbydouble
lipidbilayercalled
nuclearenvelope,
continuouswith
roughER
Entryandexitthroughnuclearpores
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16
Q

what are the functions of a nucleus

A
  • tohouse/protectDNAineukaryoticcells
  • MakeRNAandassembleribosomes
  • poresregulatemovementofsubstances(eg proteinandmRNA)inandout
  • Moleculesegregationtoallowtemporal andspatial controlofcellfunction
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17
Q

what is the function of a nucleolus

A

Nucleolus,rRNA production,assemblyofsmallandlargesubunitsofribosomes

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18
Q

DNAstrandsneedstobepackedtofitintonucleus:
DNAwrapped2xaroundgroupof8histones,toform
nucleosomes collectivelyknownaschromatin
Ascellpreparesforcelldivision,condensesfurthertochromatin
fiberthencondensesfurtherinto loopsthenstacksas
chromosomes.Mostofthetime,ourDNAispresentas
chromatinandchromatinfibers

A

draaw

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19
Q

what is a chromosome

A

comprises of many genes

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20
Q

what is a gene

A

a dna segment that contributes to phenotype or function

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21
Q

what are ribosomes

A

twosubunits,smallandlargemadeofribosomalRNA

(rRNA)incomplexwithmanyproteins

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22
Q

what is the function of ribosomes

A

Function:proteinproduction(translation),foundintwoplaceswithinthecell:
freeinthecytoplasm‐ makingproteinstobeusedincytoplasm(non
endomembranedestinations)
OR attachedtotheRER ‐ makingnon‐cytoplasmicproteins/endomembrane

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23
Q

What is the ER

A

TheERisanextensivenetworkof
tubesandtubules,stretchingout
fromthenuclearmembrane

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24
Q

What are some of the features of rough ER

A

Continuouswithnuclearenvelope
Dottedwithattachedribosomes

proteinsenterlumenwithin
theroughER forfolding
RoughERmembrane
surroundstheproteintoform
transportvesiclesdestined for
theGolgi
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25
Q

What are the major features of rough ER

A

Majorfunctionisproduction of:
• Secreted proteins
• Membrane proteins
• Organelle proteins

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26
Q

SER

A

ExtendsfromtheroughER
Lacksribosomes
doesn’tmakeproteins

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27
Q

What is the function of an ser

A 
Majorfunctionisasahousingunit
forproteinsandenzymes
Synthesizeslipids,includingsteroids
andphospholipids
Storageofcell‐specificproteins,not
allcellsmakeallproteins
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28
Q

what are cisternae

A

membraneous sacs

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29
Q

What are functions of golgi apparatus

A

Functions:
modify,sort,packageandtransport
proteinsreceivedfromtheroughERusing
enzymesineachcisternae
Formationof:
• secretoryvesicles(proteinsforexocytosis)
• membranevesicles(PMmolecules)
• transportvesicles(moleculestolysosome)

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30
Q

how do proteins move in the golgi

A

from cis to trans, and they mature at the exit cisternae

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31
Q

what are lysosomes

and what are its main functions

A

vesiclesformedfromGolgimembrane that contain strong digestive enzymes
2)MembraneproteinspumpH+ in
tomaintainacidicpHwithin

Mainfunctionisdigestionof:
• substancesthatenteracell
• cell componentse.g.
organelles ‐ autophagy
• entirecells‐ autolysis

Oncedigested,allbuildingblocks(aminoacids,lipids,etc.)arerecycled

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32
Q

What are our main categories of fuel

A 
Ourmajorcategoriesoffuel:
• Proteins:
brokendowntoaminoacids
• Fats:
brokendowntosimplefats
• Carbohydrates:
brokendowntosimplesugar
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33
Q

what are the net products of the citric acid cycle

A 
Resultsin:
2ATP
6NADH
2FADH
2
4CO2
(perglucosemolecule)
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34
Q

Where does the citric acid cycle occur?

A

in the mitochondrial matrix

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35
Q

what does the citric acid cycle require?

A

oxygen

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36
Q

what are FADH2 and NADH

A

FADH

2 andNADHareelectrondonorsintheelectrontransportchain

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37
Q

Where does glycolysis occur

A

Occursinthecytosolandoxygenisnot required

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38
Q

what are some citric cycle intermediates used for

A

amino acid synthesis
neurotransmitter synthesis
fatty acid synthesis
gluconeogenesis

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39
Q

What does it mean for a series of reactions

A

product of the first reaction is a substrate for the next

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40
Q

what is substrate level phosphorylation

A

ATPisgeneratedbythedirecttransferofa

phosphategrouptoADP

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41
Q

what processes in the mitochondria undergo substrate level phosphorylation

A

GlycolysisandCitricacidcyclemakeATPvia

substratephosphorylation

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42
Q

how many atp does chemiosmosis produce

A

Thisresultsintheproductionof26or28ATP

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43
Q

how many atp does oxidative phosphorylation produce

A

0

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44
Q

cellular respiration is versatile

A

it can derive energy from more than just carbohydrates

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45
Q

how is cellular respiration controlled?

A

Phosphofructokinase can be rate
limiting for glycolysis
it is inhibited by citrate and ATP
(though can be stimulated by AMP)

negative feedback control-integral to the production of atp

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46
Q

what is the role of insulin

A

ProducedbybetacellsofIsletsofLangerhansinpancreas
• Function:promoteglucoseuptakeintocells(forATP
productionorstorageinliver

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47
Q

what is the role of glucagon

A

• ProducedbyalphacellsofIsletsofLangerhansinpancreas
• Function:Stimulatesthebreakdownofglycogentoincrease
bloodsugarlevels

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48
Q

what happens if you lose function of insulin

A

Noglucoseincells
• NoATPfromglucose
• Noglycogen“forarainyday

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49
Q

type 1 diabetes

A

Bodydoesnotproduceinsulin,asbetacellsofpancreasaredestroyed,
oftenthisisautoimmune,orgeneticorthroughenvironmentalfactors
• Affects5– 10%ofdiabetics,andonsetusuallyoccursinchildrenor
adolescents.
• Requiresinsulinreplacement

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50
Q

type 2 diabetes

A
  • Bodyproducesinsulin,butreceptorsarenonfunctional(insulinresistance)
  • Most(>90%)diabeticsareTypeII,usuallyadultsovertheageof40
  • Canbelinkedtootherpathogies andobesity,butnotsurehoworwhy
  • Averyactiveareaofresearch
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51
Q

is the mitochondria part of the endomembrane system?

A

nope

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52
Q

anatomy of mitochondria

A 
Mitochondriaaremadeupof:
• Outer mitochondrialmembrane
• Inner mitochondrialmembrane,with
foldscalledcristae
• Fluidfilledinteriorcavity,calledthe
mitochondrialmatrix
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53
Q

other stuff about mitochondria

A

Themoreenergyacellrequires,themore
ATPitmustmake,thegreaterthenumber
ofmitochondriapresentinthatcell.

Mitochondriacarryaseparatesmall(37genes)genomeencodingmitochondrialspecificproducts2

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54
Q

what is the point of the cytoskeleton

A 
Fibres orfilamentsthathelpto
maintainthesize,shapeand
integrity ofthecell:
•Actasscaffoldingacrossthecell
•Involvedinintracellular
transportationandcellmovement
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55
Q

microfilaments

A

Comprisedofactin moleculesassembledintwolong
chains,twistedaroundeachother
30
Assembledanddisassembledasrequired‐ dynamic
Function:
Beartensionandweightbyanchoringcytoskeletontoplasmamembrane
proteins,andpromoteamoeboidmotilityifrequired(eg.macrophage)
Foundaroundtheperipheryandliningtheinteriorofcell

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56
Q

intermediate filaments

A

Diameter:8‐12nm.
Comprisedofdiverserangeofdifferentmaterials;oneexample: keratin
Foundinthecytoplasmofthecell.
Diameter:8‐12nm.
Comprisedofdiverserangeofdifferentmaterials;oneexample: keratin
Foundinthecytoplasmofthecell.
Usuallythemostpermanentofcytoskeleton

beartensionandweightthroughoutcell,e.g.,duringcellanchoring,
• actasscaffoldforcellularorganelles,e.g.,thenucleus.

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57
Q

microtubules

A

gella
Functions:
• Supportcellshapeandsize
• Guideformovementoforganelles,
• e.g.,vesiclesfromGolgitomembrane
• Chromosomeorganization– celldivision
• Supportandmovement ofcilia /flagella
32
Diameter:
:tubularstructure,25nmwithcentrallumenof15nmdiameter
Comprisedoftubulin dimers(alphaandbeta),coiled,toformatube
Extendsfromcentrioleintocytoplasm/nucleus
Assembledanddisassembledasrequired‐dynamic

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58
Q

What is an organism’s genotype

A

anorganismshereditaryinformation

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59
Q

What is an organism’s phenotype

A

actual observable or physiological traits

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60
Q

what is meant by gene expression

A

theprocessofgoingfromDNAtoafunctionalproduct

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61
Q

definition of DNA

A

istheheritablematerialthatisused
tostoreandtransmitinformationfrom
generationtogeneration

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62
Q

what is RNA

A

actsasamessengertoallowthe
informationstoredintheDNAtobeusedto
makeproteins

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63
Q

What are the 3 main steps of creating a protein

A

Transcription ofRNAfromDNA
Processingofthepre‐mRNAtranscript
Translation ofthemRNAtranscripttoaprotein

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64
Q

How is gene expression tightly regulated

A 
1)Transcriptionfactorsneedto
correctlyassembleandDNAneedsto
beaccessible.
2)Mostcontrolisatthispoint.
Capping,extentofpolyadenylation,
alternatesplicing,producingastable
3)mRNAabletobetranslated
specificproteinsassist
intheexportofmRNA
4)Regulatoryproteinscanblock
translation,variablemRNAlife‐spans
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65
Q

What types of proteins are transcribed

A

HousekeepingproteinsareactivelytranscribedfromDNAcontinuously
• ProteinandmRNAarepresentinlargequantities(e.g.Tubulin)
• Typicallyhavelonghalflifeincells
HousekeepingproteinsareactivelytranscribedfromDNAcontinuously
• ProteinandmRNAarepresentinlargequantities(e.g.Tubulin)
• Typicallyhavelonghalflifeincells
Otherproteinsareproducedinresponsetostimuliasrequired
• Cellsignaling(e.g.ligandbindingacellsurfacereceptor,oractivatingan
intracellularreceptor)
• Signaltransducedandmayenternucleustoactivatetranscription
• resultsintheproductionofashort‐livedproteintocarryouttherequired
function

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66
Q

Define anabolism

Define catabolism

A

Anabolism means building up

Catabolism means building down

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67
Q

What is the function of catabolic reactions

A

They help transfer energy from complex molecules to ATP. Complex molecules being things such as glycogen, proteins and triglycerides

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68
Q

What is the function of anabolic reactions

A

transfer energy from ATP to complex molecules

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69
Q

What is the definition of the ATP cycle

A

the transfer of energy between complex and simple molecules in the body, with ATP as the mediator

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70
Q

What are our 3 major sources of fuel and what are they broken down to

A

Proteins
Fats
Carbohydrates

Proteins are broken down to amino acids
Fats are broken down to simple fats
Carbohydrates are broken down to simple sugars

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71
Q

How is energy lost in the fuel is needed to generate atp

A

heat, energy lost in nitrogenous waste

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72
Q

Where does glycolysis occur

A

cytosol

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73
Q

What is pyruvate oxidation and where does this happen

A

pyruvate oxidation is causing the formation of Acetyl Coenzyme A
and it happens in the mitochondrial matrix

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74
Q

Where does the citric acid cycle occur

A

citric acid cycle happens in the matrix of the mitochondria

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75
Q

Where does oxidative phosphorylation occur

A

across the inner membrane

76
Q

Is oxygen required for glycolysis

A

nope

77
Q

what happens in glycolysis

A

2 ATP are invested
4 atp PRODUCED
2 nadh are produced

78
Q

Is oxygen required for pyruvate oxidation

A

yes

79
Q

What is the role of pyruvate oxidation

A

it links glycolysis to the citric acid cycle by forming acetyl CoA

80
Q

What are the products of the pyruvate oxidation

A

no ATP
1NADH per pyruvate
CO2(per pyruvate I’m assuming)

Acetyl group

81
Q

What are the products of the complete citric acid cycle

A

2ATP
6NADH
2FADH2
4CO2

(per glucose molecule)

82
Q

What happens to citric cycle intermediates

A

The intermediates are used to synthesise lots of other stuff

LIKE fatty acids
amino acids
neurotransmitter
amino acids
glucose
83
Q

What is meant by a series of reactions and is the citric acid cycle considerred to be one

A

Yes, the citric acid cycle is considerred to be a series of reaction

This is when a product of the first reaction is the substrate for the next

84
Q

Define substrate level phosphorylation

and which two parts of the process

A

glycolysis and citric acid cycle; use substrate phosphorylation

it is defined as the direct transfer of a phosphate group to ADP

85
Q

what is the definition of oxidative phosphorylation

A

ATP is generated from the oxidation of NADH and FADH2 and the subsequnt transfer of electrons and pumping of protons

86
Q

how many ATP is produced in the ETC

A

26 to 28

87
Q

WHy is 26-28 ATP produced in electron transport chain and chemiosmosis, why not just 26 and why not just 28

A

Phosphorylation and redox reactions are not directly coupled, so have a ratio rather than a straight number

Energy stored in the H+ gradient may be used solely to produce ATP or may be split between making ATP and powering other mitochondrial processes

Glycolytic NADH electrons must be shuttled into the mitochondria, and transferred to either NAD+ or FAD, The latter of which promotes production less ATP

88
Q

Give the steps of the electron transport chain

A

NADH and FADH2 are oxidised to donate 1 or 2 electrons
electrons transfer from protein to protein along the chain in a series of redox reactions
At each transfer, each electron gives up a small amount of energy which enables H+ ions to be pumped into the intermembrane space.
OXYGEN PULLS THE ELECTRONS DOWN THE CHAIN AND IS THEN THE FINAL ELECTRON ACCEPTOR WHERE IT IS REDUCED TO WATER

89
Q

What is chemiosmosis and what is the process

A

The hydrogen ions in the intermembrane space rush down their concentration gradient through ATP synthase.

This causes the turbine within ATP synthase to turn

90
Q

what does it mean that cellular respiration is versatile

A

We can derive energy from more than just glucose,
fats, proteins and more complex carbohydrates generate ATP also
monomers enter glycolysis and the citric acid cycle at different points

91
Q

How is cellular respiration controlled

A

Phosphofructokinase limits rate for glycolysis

Negative feedback control is integral to the production of ATP

92
Q

Definition of homeostasis

A

the maintenance of relatively constant conditions within physiologically tolerable limits

93
Q

What are the functions of insulin

and where is it produced

A

produced by beta cells of islets of langerhans in the pancrease

Function: promote glucose uptake into cells (for ATP production or storage in liver)

94
Q

What are the functions of glucagon

and where is it produced

A

produced in the alpha cells of islets of langerhans in pancrease

it stimulates the breakdown of glycogen to increase blood sugar levels

95
Q

What is diabetes mellitus

what are some of its side effects

A

the ability to produce or respond to insulin hormone impaired

results in abnormal metabolism of carbohydrates and elevated levels of glucose in blood

96
Q

What generally happens when you lose the function of insulin

A

no glucose in cells
no ATP from glucose
no glycogen “for a rainy day”

97
Q

What is type 1 diabetes
who does it usually affect
how is it often treated

A

Body does not produce insulin, as beta cells of pancreas are destroyed, this is usually genetic, or autoimmune

Since it is a genetic disease, it often happens in children and adolescents

The treatment requires insulin replacement

98
Q

What is type 2 diabetes

A

body produces insulin, but receptors are non functional

happens mostly to adults over age of 40 (queen the plague)

It is often linked to other pathogies and obesity, but it is unclear why

Treatment options include careful energy intake management
some drugs

99
Q

Why is extreme hunger and constant eating and unexplained weight loss symptoms of diabetes

A

The lack of functional insulin means that glucose is not able to get inside the cells to make ATP so the body asks for more glucose from both food and body stores

100
Q

List 10 different side effects of diabetes

A 
excessive thirst
frequent urination
extreme hunger or constant eating
unexplained weight loss
presence of glucose in urine
tiredness or fatigue
changes in vision
numbness or tingling in extremeties
slow healing wound or sores

abnormally high frequency of infection

101
Q

What is initiation of transcription

A

Assembly of multiple proteins required before transcription can commence

102
Q

What are the 3 main steps of initiation

A

Transcription factors are made, and several transcription factors bind to DNA( i assume near the promoter region)

After TFs bind, RNA POLYMERASE ii can now bind along more TFs to form the transcription initiation complex
transcription begins

103
Q

What happens during elongation

A

10-20 nucleotides exposed at a time when unwound

Complementary RNA nucleotides added to 3’ end of growing transcript

double helix reforms as transcript leaves the template strand

104
Q

what happens at t Termination

A

after transcription of the polyadenylation signal, nuclear enzymes release the pre-mRNA and RNA polymerase then dissociates from the DNA

N.B, proofreading less than for DNA replication

105
Q

what are some steps for mRNA processing

A

capping: a modified guanine nucleotide is added to the 5’ end
Tailing:50-250 adenine nucleotides are added to the 3’ end

106
Q

What is the point of mRNA processing

A

facilitate export, confer stability, facilitake ribosome binding once in cytoplasm

107
Q

splicing

A

introns are removed from the transcript

108
Q

What are exons

A

coding regions including things called UTRs-untranslated regions at 5’ and 3’ ends

109
Q

what are introns

A

non-coding regions intervening exons

110
Q

Where does splicing occur

A

at the SPLICEOSOME. the SPLICEOSOME is within the NUCLEUS

111
Q

What is a spliceosome

A

a large complex of proteins and small RNAs

112
Q

How does splicing occur

What determine splcing

A

introns are removed from the transcript and rejoined to form mature mRNA

short donor and acceptor sequences near the ends of the introns determine splicing.

mutations in these splice sites can affect generation of gene produc

113
Q

What is alternative splcing

A

splicing of DNA at different sites

it allows for multiple gene products from the same gene

114
Q

What is the wobble hypothesis

How is it derived

A

that tRNAs can base pair to more than one codon.

there are 64 possible codons, 61 of which code for amino acids, but there are only around 40 tRNAs as tRNAs can base pair to presumably to more than one codon

115
Q

what is translation-

A

when mature mRNA transcript exits nucleus and is bound by the ribosome

116
Q

What is the overview of translation

A

codons are translated into amino acids

tRNA molecules within the ccytosol with specific anticodons carry corresponding amino acids

Hydrogen bonds form between mRNA and anticodon of appropriate tRNA

The amino acid is added via peptide bonds to the growing polypeptide chain

117
Q

What are the functions of a ribosome

A

ribosome has binding sites for mRNA and tRNA

tRNA and mRNA held within ribosome to enable to formation of the polypeptide

118
Q

what does the A site do

A

holds next in line tRNA

119
Q

what does the P site do

A

holds tRNA carrying the growing polypeptide

120
Q

what does the e site do

A

tRNAs exit from here

121
Q

what is a tRNA

A

it is a physical link between the mRNA and the amino acid sequence of proteins

122
Q

what happens during translation initiation

A

an initiator tRNA=a tRNA carrying methionine is needed

the small ribosomal subunit with initiator tRNA already bound binds to the 5’ cap of mRNA

the small ribosomal subunit scans downstream to find the translation start site

Hydrogen bonds form between initiator anticodon and mRNA

Large ribosomal subunit then binds- completing initiation complex

GTP needed for the assembly of the translation initiation complex

123
Q

What happens in the elongation phase of translation

A

1) codon recognition
2) peptide bond formation
3) Translocation

124
Q

What is the codon recognition phase of translation

A

happens in elongation

it is when base pairs with complementary anticodon.

here GTP is invested to increase accuracy and efficiency

125
Q

What happens during the peptide bond formation phase of translation

A

happens during elongation
A large subunit rRNA catalyses peptide bond formation
and removes it from tRNA in P site

126
Q

what happens during translocation

A

moves tRNA from A to P site
tRNA in P site moves to E and is released.

Energy is required

127
Q

what happens to the empty tRNAs after elongation

A

empty tRNAs are reloaded in the cytoplasm using aminoacyl tRNA synthetases

128
Q

What happens at the termination step of translation

A

Ribosomes reaches a stop codon on mRNA
this causes release factor that promotes hydrolysis

the ribosomal subunits and other components dissociates

129
Q

Explain what happens when a ribosome reaches a stop codon on mRNA

A

Mrna STOP CODON IN THE a SITE IS BOUND BY A RELEASE FACTOR

130
Q

What happens to the bond between the p site tRNA and last amino acid when it is hydrolysed

A

polypeptide made is released

131
Q

What is needed for the ribosomal subunits and other components to dissociate in the translation termination step

A

hydrolysis of 2 GTP molecules

132
Q

what determines the properties of each amino acid

A

The side chains

133
Q

What is a primary structure

A

it is a structure determined by DNA sequence and it is held by covalent bonds between amino acids

it starts to form secondary structures as soon as it leaves the ribosome

134
Q

What is the N terminus and C terminus

A

N terminus is the amino end of the amino acid, and the C terminus is the carboxyl end of the acid. It should be noted that protein is coded from N to C i THINK

135
Q

What is a key component of secondary structures

A

secondary structures include alpha helices and beta pleated sheets that are held together by hydrogen bonds

136
Q

What is a tertiary structure

A

a tertiary structure is a 3D shape stabilized by side chain interactions.

The bonds often includes hydrgophobic interactions, hydrogen bonds
and sometimes disulphide bonds

137
Q

What is the definition of quaternary structure

A

multiple proteins associate to form a functional protein. May be homo or hetero

138
Q

what are the chaperone proteins

A

proteins that help with folding of polypeptide chains into tertiary structure

139
Q

what is a signal peptide

A

at the N terminus of the protein, the small strip is known as a signal peptide

it directs ribosomes to the RER methinks(thats what chen says_

wikipedia says: Signal peptides function to prompt a cell to translocate the protein, usually to the cellular membrane. In prokaryotes, signal peptides direct the newly synthesized protein to the SecYEG protein-conducting channel, which is present in the plasma membrane. A homologous system exists in eukaryotes, where the signal peptide directs the newly synthesized protein to the Sec61 channel, which shares structural and sequence homology with SecYEG, but is present in the endoplasmic reticulum.[3] Both the SecYEG and Sec61 channels are commonly referred to as the translocon, and transit through this channel is known as translocation. While secreted proteins are threaded through the channel, transmembrane domains may diffuse across a lateral gate in the translocon to partition into the surrounding membrane.

140
Q

what does the signal recognition particle do

A

the signal recognition particle recognises the signal peptide, and then it retards elongation and docks to the receptor

141
Q

what is the overview of the fate of protein (6 steps)

A

1)Polypeptide synthesis begins
2)SRP binds to signal peptide
3) SRP binds to receptor protein
4) SRP detaches and polypeptide synthesis resumes
5) signal cleaving enzymes cuts off signal peptide
the completed polypeptide folds into final conformation

142
Q

in the ER lumen, what happens to a secretory protein and what happens to a membrane protein when the completed polypeptide folds into final conformation

A

A secretory protein is solubilized in lumen, while a membrane protein remains anchored to the membrane

Both then go to the golgi via vesicles for further maturation

143
Q

Why do we need post-translational modifications

A

translation is now complete but the protein may not yet be functional

144
Q

What do some post-translational modifications do to a protein

A

it can confer activity-via phosphorylation or enzyme cleavage

it can confer an ability to interact with other molecules- this includes biotinylation, methylation of histones

or this can direct proteins towards particular locations- e.g ubiquitination for proteasome degradation

ULTIMATELY ALL OF THIS PROVIDES ANOTHER LEVEL of REGULATION

145
Q

What are the three main steps of a transduction method of cell signalling

A

reception
transduction
respons

146
Q

What happens at reception

A

signalling protein binds to a receptor protein and allows or causes the activation of a protein

147
Q

What happens during transduction

A

the activated protein may cause a relay of changes, this when relay molecules known as second messengers and other proteins may be activated

a common example includes the phosphorylation cascade

148
Q

Why are receptors specific

A

human body sends many chemicals- gotta be specific if we want to activate a target receptor

only certain cells at certain times will have particular receptors meaning that while the signal might be widespread the transmission of the signal occurs only where it is needed

149
Q

What are the 2 kinds of receptors

A

intracellular receptors

membrane bound-cell surface receptors

150
Q

Describe intracellular receptors

A

primary messenger is generally hydrophobic and/or small-lipid soluble, it can cross PM.
this typically includes sex hormones and thyroid hormones

after it crosses, it causes a significant change

151
Q

Describe membrane bound cell surfce receptors

A

primary messenger is generally hydrophilic and need help to cross PM

152
Q

what are GPCRs

A

G protein coupled receptors

these are typically transmembrane proteins and have the weird feature of passing the PM 7 times. there are many different ligands and have diverse functions

153
Q

what are G proteins

A

G proteins are molecular switches which either are on or off depending on whether GDP or GTP is bound

154
Q

generally how does a GPCR work

A

at rest, the receptor is unbound and G protein is bound to GDP, the enzyme is in an inactive state

the ligand then binds to receptor and binds the G protein. GTP displaces GDP. the enzyme is still inactive

the activated G protein dissociates from recptor. Enzyme is activated to elicit a cellular response

G Protein has GTPase activity promoting its release from enzyme and reverting it back to resting state

155
Q

explain the basic mechanism of a ligand gated ion channel

A

binding of ligad at specific site on receptor elicits change in shape

the channel opens or closes as the receptor changes shape
ions can then pass through channel

156
Q

what do protein kinases do

A

protein kinases are enzymes that transfer a phosphate group from ATP to another protein

series of protein kinases each add a phosphate to the next kinase

157
Q

what do phosphatases do

A

they are enzymes that dephosphorylate, rendering the protein inactive-but recyclable

158
Q

how is calcium often used as a common second messenger

A

conc grad- usually theres a low calcium concentration inside the cell and very high calcium concentration outside the cell.

The maintenance of concentration via calcium pumps important

159
Q

Why are there so many steps in cell signalling

A

it amplifies the response

provides multiple control points

allows for specificty of response

allows for coordination with other signaling pathways

160
Q

Why do somatic cells divide?

A

growth and development, tissue renewal

results in 2 daughter cells that are genetically and functionally identical to the parent cell

161
Q

Do all somatic cells divide?

A

many, but not all.

Some like muscle cells don’t divide at all

162
Q

What stages are found in the interphase

A

growth-aka gap phase 1
Synthesis of DNA-aka S phase

growth phase 2, G2

163
Q

What happens in G1

A

most cellular activities occur here;

cells here are metabolically active, the duplication of organelles and cytosolic components happen

Centrosome replication begins

164
Q

What happens in G0

A

known as the resting phase, it is a cellular state outside of the replicative cell cycle

165
Q

what is the cell cycle

A

it is the series of events that take place in a cell leading to duplication of its DNA

166
Q

What happens in the S phase

A

DNA replication occurs

strands are separated at the hydrogen bonds holding the nucelotides together

new strand of DNA is synthesized opposite each of the old strands

167
Q

What happens in the G2 phase

A

checks for correct DNA synthesis-it prepares for the mitotic phase

Cell growth continues
enzymes and other proteins are synthesized

Centrosome replication repeated

168
Q

How long does the following take;
G1 phase
S phase
G2 phase

A

g1= 8-10 hrs
S=8 hrs
G2=4 to 6 hours

169
Q

what does the mitotic phase include

A

mitosis plus cytokinesis

170
Q

What are sister chromatids

A

sister chromatids are the two identical chromatids per chromosome

sister chromatids are 2 identical copies of the same chromosome formed by DNA replication attached to each other by a structure called a centromere

171
Q

what are the 3 checkpoints called

A

M checkpoint, G2 check point and G1 checkpoint

172
Q

what are the 3 key regulatory molecules for G2 and what are their functions

A

Cyclin: a protein that fluctuates throughout the cell cycle. It pretty much attaches to target kinases and direct the Cdk to a specific set of target proteins

Cyclin dependant kinase (Cdk): a kinasethat is activated when attached to a cyclin: kinases phosphorylate protein making it more active

M phase promoting factor: an cyclin and a Cdk bound to its M cyclin partner

173
Q

what are the G1 “checkpoints” for cell division

A

1) undamaged DNA
2) Cell size
nutrition
3) appropriate signals

174
Q

what are the M checkpoints

A

All chromosomes are attched to spindles

175
Q

What happens when a cell does not pass the G1 checkpoint

A

cell enters G-0, EXITS CELL DIVISION

176
Q

what happens when the cell does not pass the M checkpoints

A

stop signal received, and cell division goes towards a halt

177
Q

How does DNA become changed

A

could be the result of an acquired change

or inherited change

178
Q

what are the 2 commonly affected genes

A

proto-oncogenes- genes that stimulate cell proliferatio
or
Tumor suppressor genes-genes that keep proliferation in check

179
Q

What happens when tumour suppressor genes lose function

A

it causes a loss of brakes

it means that cell division not under control

180
Q

what are 3 examples of tumor suppressor gene

A

TP53, brca1, brca2

APC, SMAD4

181
Q

what are 2 examples of oncogene

A

Ras- a GTPase

and Myc- a transcription factor

182
Q

what is a proto oncogene

A

A normal cellular gene that encodes a protein usually involved in regulation of cell growth or proliferation and that can be mutated into a cancer-promoting oncogene, either by changing the protein-coding segment or by altering its expression

183
Q

what is an oncogene

A

A gene whose product is involved either in transforming cells in culture or in inducing cancer in animals. Most oncogenes are mutant forms of normal genes (proto-oncogenes) involved in the control of cell growth or division

184
Q

why does an oncogene cause cancer

A

oncogene provides an excessive or uncontrolled growth promoting signal

185
Q

how does a carcinoma form

A

Loss of tumor suppressor gene such as APC

causes a small polyp to form

2) activation of ras oncogene
3) loss of tumor suppressor gene SMAD4

this may cause the growth of a larger benign growth - an adenoma

4) loss of tumor suppressor gene -53 and additional mutations causes carcinoma.

186
Q

What are primary human cells

A

cells that are directly cultured from their source organ tissue

187
Q

what are immortalised human cell lines

A

cell which would normally not proliferate indefinitely but have evaded normal cellular senescence

XIA BIOSCI107 (5 decks)

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