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1.1 Flashcards

1
Q

Role of Na/K-ATPase on phospholipid bilayer

A

Continuously maintains gradient

  • Pumps out 3Na+
  • Pumps in 2K+
  • Using energy from ATP hydrolysis (1 Pi used)
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2
Q

Where are nuclear pores found?

A

Nuclear pores - on nuclear envelope

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3
Q

Function of nuclear pores

A

Allow movement of RNA

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4
Q

Function of nucleolus

A

Site of ribosome synthesis

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5
Q

Function of chromatin

A

To efficiently package DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence. Packaging DNA into chromatin allows for mitosis and meiosis, prevents chromosome breakage and controls gene expression and DNA replication

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6
Q

Composition of chromatin

A

DNA + associated proteins

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7
Q

Which is looser, euchromatin or heterochromatin?

A

Euchromatin

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8
Q

Function of heterochromatin

A

TIghtly packed (prior to replication of DNA)

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9
Q

Function of euchromatin

A

Loose + uncoiled for DNA transcription

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10
Q

What is the endoplasmic reticulum?

A

Interconnecting tubular vesicles (cisternae)

  • Rough and smooth variants
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11
Q

Function of ER and Golgi?

A

Make up a specialised transport system within the cell - which allows post-translational modification of proteins as well as lipid synthesis

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12
Q

mRNA exits nucleus and moves where?

A

RER

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13
Q

What is the role of ribosomes on RER?

A

Create an amino acid chain by translating the mRNA

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14
Q

Where does the newly made protein chain move to and from?

A

From RER to SER

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15
Q

What occurs at the SER?

A

Post-translational modifications

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16
Q

Where does proteins from SER go to?

A

Cis-face of Golgi apparatus

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17
Q

Role of Gogli

A

Further processing of amino acid chain by: removal of certain parts of protein chain or adding sugar/other molecuels

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18
Q

After an amino acid chain has been processed by the Golgi where does it exit from and go?

A

Exits at the trans-face

Goes where it’s needed e.g. lipid bilayer

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19
Q

What is motile cilia?

A

Apical membrane protrusion of axoneme (microtubule) with rhythmical movement

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20
Q

Where is motile cilia found?

A

Respiratory epithelium

Fallopian tubes

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21
Q

What is microvilli?

A

Multiply small foldings of apical membrane to increase SA (for absorption)
- Basolateral membrane can have deep folds

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22
Q

1 word summary of the role of motile cilia and microvilli

A

Motile cilia - movement

Microvilli - absorption

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23
Q

What maintains the structure of microvilli?

A

Actin microfilaments

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24
Q

What is the cellular cytoskeleton?

A

Glycoproteins that maintain the structure + transport

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25
Q

Which 3 different molecules that make up the cellular cytoskeleton?

A

Microfilaments - actin (cell movement)

Intermediate filaments - alpha-helices (mechanical stability)

Microtubules - hollow tubes (intracellular transport, chromosome alignment, cilia movement)

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26
Q

Function of microfilaments

A

Changes shape of the cell including movement for phagocytosis

Actin most common

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27
Q

Function of microtubules

A

Intracellular transport
Chromosome alignment
Cilia movement

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28
Q

What connects cells?

A

Cell junctions

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29
Q

What are the 3 main types of cell junctions?

A

Occluding
Anchoring
Gap junctions

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30
Q

Anchoring junctions subtypes

A

3 types of junctions:

  • Adherens
  • Desmosomes
  • Hemidesmosomes
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31
Q

Role of occluding (tight) junctions?

A

Sticks cells together, stops molecules passing from one side of cells to other so they form a barrier

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32
Q

Function of occluding junctions

A

Separate apical + basolateral membrane for protein specialisation

Determine if epithelium is tight or leaky

Barrier

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33
Q

Function of anchoring junctions

A

Cell-to-cell - extracellular matrix

  • All have: cytoskeleton component, link protein, cell-cell protein
  • Adherens, desmosomes, hemisdesmosomes
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34
Q

Composition of adherens

A

Actin + beta-catenin + cadherins

  • Make an adhesion belt
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35
Q

Composition of desmosomes

A

Intermediate fibres + desmoplakins + desmogleins (cadherins) - pemphigus

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36
Q

Composition of hemidesmosomes

A

Intermediate fibres _ desmoplankins + integrin proteins

  • Anchor cell to basement membrane
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37
Q

Function of gap functions

A

Electrical synapses - functional connections between cytosol of two adjacent cells

Allow connection between cells

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38
Q

What are gap junctions made of?

A

A collection of connexons (each connexon is made of 6 connexin monomer proteins)

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39
Q

Where are gap junctions found?

A

Myocardium, myometrium, enteric smooth muscle

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40
Q

Function of peoxisomes

A

Single membrane, lytic enzymes for beta-oxidation of very long chain fatty acids - produce hydrogen peroxides

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41
Q

Function of centrioles

A

Quiescent except for spindle formation during mitosis

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42
Q

Function of lysosomes

A

Single membrane, lytic enzymes for macromolecule digestion and cell turnover

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43
Q

Gap junctions form what type of channel?

A

Hydrophilic channel

- Allowing charged molecules to pass through

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44
Q

Mitochondria

A

Folded double-membrane (cristae), site for oxidative phosphorylation mitochondrial DNA

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45
Q

What is arachidonic acid?

A

Lipid, bound inside of plasma membrane.

It’s acted upon by enzymes to be converted into signalling molecules called eicosanoids

46
Q

What are eicosanoids?

A

Signaling molecules made by the enzymatic or non-enzymatic oxidation of arachidonic acid or other polyunsaturated fatty acids

47
Q

What does phospholipase A2 cleave?

A

Phospholipid (in lipid bilayer)

48
Q

What arachidonic acid metabolite is responsible for: vasoconstriction and promoting platelet aggregation?

A

TXA2 (Thromboxane A2)

49
Q

What arachidonic acid metabolite is responsible for: vasodilation and inhibition of platelet aggregation?

A

PGI2 (Prostacyclin)

50
Q

What arachidonic acid metabolite is responsible for: vasoconstriction, bronchoconstriction, gastric mucus production?

A

PGE2

51
Q

What is prostacyclin?

A

Also called prostaglandin I2 (PGI2) is a prostaglandin member of the eicosanoid family of lipid molecules. It inhibits platelet activation and is also an effective vasodilator.

52
Q

What is PGE2 also known as?

A

Dinoprostone - a naturally occurring prostaglandin which is used in labour induction

53
Q

As a medication, what is PGE2 used for?

A

Labour induction, bleeding after delivery, termination of pregnancy, and in newborn babies to keep the ductus arteriosus open.

In babies it is used in those with congenital heart defects until surgery can be carried out.

54
Q

What arachidonic acid metabolite is responsible for: uterine contraction?

A

PGF2a (Prostaglandin F2alpha)

55
Q

What arachidonic acid metabolite is responsible for: leukocyte chemotaxis and bronchoconstriction?

A

LT (Leukotrienes)

56
Q

What is prostaglandin F2alpha used for?

A

It is a naturally occurring prostaglandin used in medicine to induce labor and as an abortifacient (stimulates uterine contraction)

57
Q

Where is oxytocin produced and released?

A

Produced in paraventricular nucleus of the hypothalamus.

Released by the posterior pituitary.

58
Q

How is fat catabolised?

A

beta-oxidation

59
Q

What happens to the products of beta-oxidation of fats?

A

Normally enter the TCA cycle and used as energy

60
Q

What happens to fat breakdown in starvation?

A

Lipolysis and beta-oxidation gives Acetyl-CoA (which enters TCA when there are metabolites - i.e. not in starvation)

Run-out of TCA intermediates (they are used as energy)

No oxaloacetate (first module that binds with Acetyl-CoA)

Acetyl-CoA substrate accumulates in cell and is turns into ketones

This is an alternative energy source and reduces proteolysis

61
Q

What does lack of insulin cause?

A

Ketogenesis

Leading to acidosis if high levels of ketones

62
Q

Which patients are at most risk of ketoacidosis?

A

Type 1 diabetes

63
Q

What happens as a result of hyperglycaemia?

A

Polyuria so patient becomes very dehydrated (happens in type 1 diabetes in the absence of insulin)

64
Q

Where does the TCA take place?

A

Mitochondrial matrix

65
Q

What generates a proton motive force using NADH and FADH2?

A

Electron transport chain - pumps protons into intermemebrane space

66
Q

What can interphase be divided into?

A

G1, S, G2

67
Q

What lies between the phases of interphase?

A

Check-points regulated by cyclins

68
Q

How do cyclins regulate the cell cycle?

A

They regulate cyclin dependent kinases which are needed to be activated for cell cycle progression

69
Q

Which part of the cell cycle is the major determinant of length?

A

Interphase - growth + prep for mitosis

70
Q

What does the G1 checkpoint make sure?

A

Cell is large enough to proceed to next phase (S)

71
Q

In the absence of growth factors what happens at the G1 checkpoint?

A

Cyclin dependent kinases are inactivated

This leads to unopposed activity of the pRB protein which is a tumour suppressor gene that forces cell to enter G0 phase

Cell growths before re-attempting G1 checkpoint

72
Q

What does the G1-S checkpoint check for?

A

DNA damage

73
Q

What happens at the G1-S checkpoint when there is DNA damage?

A

Increases p53 (tumour suppressor) levels which activates p21

This inhibits cyclin dependent kinases which prevents S-entry allowing time for DNA repair

Is DNA damage is too severe it undergoes apoptosis

74
Q

What does the G2-M checkpoint check for?

A
  • Incomplete DNA replication

- Damaged DNA

75
Q

What is the G2-M checkpoint regulated by?

A

M-CDK (maturation promoting factor)

Which is needed to initiate mitosis

76
Q

Where is the mitotic checkpoint?

A

Between metaphase and anaphase of mitosis

77
Q

What can cause genomic instability (loss of cell cycle control)?

A

Checkpoint failure (loss of tumour suppressor genes)
OR
Increased oncogene activity

78
Q

What can loss of tumour suppressor gene cause?

A
  • Dysplasia –> cancer

- Replication of damaged DNA or wrong number of chromosomes

79
Q

Define gene mutation and gene amplification

A

Gene mutation: anyway where in pathway or associated DNA

Gene amplification: duplication or new chromosomes

80
Q

How can oncogenes become overactive?

A

There are 2 alleles for the oncogene just like any other gene

One mutated allele needed for it to go crazy

81
Q

What is familial adenomatous polyposis an example of?

A

An autosomal dominant inherited cancer syndrome

Causes loss of function mutation of APC gene

Which causes hundreds of colonic polyps which become cancerous and lead to colorectal cancer

82
Q

How is familial adenomatous polyposis treated?

A

Prophylactic total colectomy, it is incurable

Happens in late teens or early 20s

83
Q

How many alleles need to be mutated for tumour suppressor genes to malfunction?

A

2 gene allele mutations needed to cause loss of normal growth inhibition

(whereas only 1 oncogene allele mutation needed to increase cell growth)

84
Q

New DNA can only be made in which direction?

A

5’-to-3’

85
Q

What is the name of the fragments in which DNA polymerase synthesises DNA in the 5’-to-3’ direction?

And what are the fragments joined with?

A

Okazaki fragments

DNA ligase joins the fragments together

86
Q

What is the role of topoisomerase?

A

Unwinds DNA

87
Q

Roles of DNA helicase dna DNA polymerase.

A

DNA helicase splits DNA strands into the replication fork in bubbles

DNA polymerase adds new bases (it has proof-reading capabilities)

88
Q

Role of RNA polymerase?

A

Binds genes + synthesis RNA

Doesn’t have proof-reading capabilities

89
Q

What is RNA polymerase guided by to the correct place?

A

Transcription factors

90
Q

Which enzymes are involved in DNA transcription?

A

Helicase and topoisomerase enzymes

91
Q

What does an increased amount of transcription factor binding to DNA lead to?

A

Increased amount of pre-mRNA transcription hence increased amount of protein

92
Q

What does epigenetic modification do?

A

Affect gene activity or expression without influencing DNA itself

It affects histones (proteins DNA is wrapped in) to affect unwrapping

93
Q

Name the single stranded molecule that contains uracil.

A

RNA

94
Q

What is removed when pre-mRNA is processed into mRNA?

A

Introns removed

95
Q

What is polyadenylation?

A

Polyadenylation is the addition of a poly(A) tail to a messenger RNA.

The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases.

In eukaryotes, polyadenylation is part of the process that produces mature messenger RNA (mRNA) for translation.

96
Q

What is the guanine cap?

It’s function and purpose?

A

A capping enzyme (CE) is an enzyme that catalyzes the attachment of the 5’ cap to messenger RNA molecules that are in the process of being synthesized in the cell nucleus during the first stages of gene expression.

This process, known as mRNA capping, is highly regulated and vital in the creation of stable and mature messenger RNA able to undergo translation during protein synthesis.

Mitochondrial mRNA and chloroplastic mRNA are not capped.

97
Q

How is mRNA translated?

A

In triplets

Codons (3 nucleotides) correspond to anticodons on tRNA

Codons code for amino acids which are bound together in ribosomes

98
Q

What is the AUG codon?

A

mRNA ‘start codon’

It codons for methionine amino acid

99
Q

What does the smaller 40s subunit of ribosomes binds?

A

mRNA

100
Q

What does the smaller 60s subunit of ribosomes binds?

What is this subunit responsible for?

A

tRNA

Responsible for peptide bond formation

101
Q

What lagging strand (3’-to-5’) is replicated how?

A

In okazaki fragments

102
Q

What does transcription factors promote?

A

TATA box assembly to guide RNA polymerase

103
Q

The aim of meiosis is 2n to n. How is this achieved?

A

Replicate 2n to 4n, then divide twice to n

Makes 4 n gametes with random segregation of maternal/paternal chromosomes

104
Q

The aim of mitosis is 2n to 2n. How is this achieved?

A

Replicate 2n to 4n, then divide chromatids once, equally between 2 daughter cells

Makes 2 identical 2n daughter cells

105
Q

In which phase of mitosis does chromatin condense into chromosomes and nucleolus disappears?

A

Prophase

Spindles synthesis also happens

106
Q

In which phase of mitosis does the chromosomes line up along the metaphase plate?

A

Metaphase

107
Q

In which phase of mitosis does the spindles pull and separate chromatids through centromeres to opposite ends of the cell?

A

Anaphase

108
Q

In which phase of mitosis does the nuclear membrane reform,nucleoli reappear and chromosomes unwinds into chromatin?

A

Telophase

109
Q

In which phase of mitosis does myosin II and active filament ring contract to cleave the cell in two?

A

Cytokinesis

110
Q

In which phase of meiosis does alignment of sister chromosomes occur?

This is where crossing over of maternal and paternal material happens.

A

Prophase 1

111
Q

How is anaphase (1) different in meiosis and mitosis.

A

In meiosis homologous chromosomes are being separated

In mitosis sister chromatids are being separated

112
Q

What happens in anaphase 2 of meiosis?

A

Paired chromatids align and are separated through centromere

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