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General Pathology > Cell Biology Review > Flashcards

Cell Biology Review Flashcards

1
Q

What are the 3 main types of RNA?

A

Messenger, mRNA
Ribosomal, rRNA
Transfer, tRNA

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2
Q

______ are triplets of nucleotides in the mRNA

A

Codons

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3
Q

mRNA is termed the _____ strand

A

sense

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4
Q

What tells which triplets to use to make sense?

A

The reading frame

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5
Q

What can cause a shift in the reading frame?

A

Insertions or deletions

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6
Q

What is the dense, inactive (not being transcribed) form of the chromosome called?

A

Heterochromatin

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7
Q

What is the disperse and active form of the chromosome called?

A

Euchromatin

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8
Q

What are enhancers and silencers and where are they found?

A

Regulatory DNA segments upstream of the promoter or downstream of the gene

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9
Q

List the two types of transcription factors (proteins)

A

Activators
Repressors

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10
Q

What is the function of activators?

A

Bind to enhancers increasing transcription

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11
Q

What is the function of repressors?

A

Bind to silencers decreasing transcription

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12
Q

What is the promoter?

A

Region of DNA that initiates transcription of a particular gene

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13
Q

Describe the parts of the promoter

A

Distal- upstream of the proximal promoter

Proximal

Core- has binding sites for transcription factors (i.e. TATA box), binding site for RNA polymerase and the transcription start site (TSS)

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14
Q

What is the function of the 5’ cap?

A

Protects the nascent mRNA from degradation and assists in ribosome binding

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15
Q

What is the function of 5’ UTR?

A

(leader sequence) - helps in regulation of translation

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16
Q

Describe the protein coding region

A

-Introns are spliced out (RNA processing) in the nucleus
-Exons are variably retained (alternative splicing) allowing for multiple proteins (isoforms) to be made from the same gene

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17
Q

What is the function of the 3’ UTR?

A

Determines termination and regulation of translation

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18
Q

What is the function of the poly A tail?

A

(Multiple adenine residues) which prevents degradation of the mRNA. Can also influence localization of the transcript and translation

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19
Q

It is estimated that >94% of the DNA that is transcribed is not translated into protein, rather it is used to __________

A

regulate transcription

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20
Q

Describe functional, non-protein coding DNA

A

-Structural DNA involved in cell function (telomeres, centromeres)
-Structural DNA involved in gene regulation (histone binding sites, promoters/enhancers, mobile genetic elements - transposons)
-Most is transcribed into non-coding regulatory RNAs

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21
Q

List the Housekeeping RNAs

A

Transfer RNA
Ribosomal RNA

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22
Q

List the regulatory RNA

A

-Long non-coding RNA (lncRNA - linear or circular)
-Small non-coding RNA (sncRNA): microRNA (miRNA) and small interfering RNA (siRNA)

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23
Q

Describe the features of Micro-RNAs (miRNAs)

A
  • 20-30 bp
  • ~6,000 miRNA genes, each regulating multiple protein-coding genes
    -Trimmed by enzyme Dicer
    -Associate with RNA-induced silencing complex (RISC) to bind to mRNA
    -Leads to posttranslational silencing of genes (most of the time)
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24
Q

Describe the features of small interfering RNA (siRNA)

A
  • dsRNA (20-24bp) designed to interfere with translation of a specific mRNA
    -Very useful in research: can create synthetically and use to decrease expression (i.e. knockdown) of a gene and study the effect of that gene
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25
Q

Describe the features of long noncoding RNA (lncRNA)

A
  • > 200bp
    -Many more of these than coding mRNA
    -Multiple ways of modifying gene expression:
    1. Interact with transcription factors to activate or suppress
    2. May alter acetylation or methylation of DNA or histones
    3. Stabilize secondary or tertiary structure of protein complexes that influence chromatin architecture or gene activity
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26
Q

What is the clinical relevance of long noncoding RNA (lncRNA)?

A

We proved that a multitude of them play a pivotal role in the different processes involved in the progression of the disease. lncRNAs could become unique and valuable biomarkers or future targets for personalized medicine

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27
Q

Where do single nucleotide polymorphisms (SNPs) occur?

A

Across the whole genome

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28
Q

What happens when single nucleotide polymorphisms (SNPs) occur in non-coding regions?

A

Can affect regulatory regions –> altered gene expression

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29
Q

Describe the interaction between single nucleotide polymorphisms (SNPs) and disease

A

-Effect on disease susceptibility is weak
-If co-inherited with a disease-associated gene, it can be a useful marker for that disease

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30
Q

What is copy number variation?

A

-A type of genetic variation
- 1000-millions of base pairs of repeated segments of DNA
-Responsible for a significant portion of variation between people

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31
Q

What is CRISPRs?

A

-Clustered regularly interspaced short palindromic repeats (CRISPRs)
-Gene editing
-Allows inserting specific genes into cells, which may allow “correction” of genes associated with disease
-Human trials are promising

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32
Q

What is the purpose of membrane-bound organelles?

A

Allows cell functions to be compartmentalized without damaging the cell

33
Q

What is the function of the rough endoplasmic reticulum (RER)?

A

Synthesis and folding of plasma membrane proteins and secreted proteins

(factory builders)

34
Q

What is the function of the smooth endoplasmic reticulum (SER)?

A

-Lipid synthesis-membranes
-Specialized features based on cell type: liver (drug detoxification), ovaries/testes/adrenals (steroid hormone synthesis), muscle (calcium regulation)
-Protein transport

(factory builders)

35
Q

What is the function of the golgi apparatus?

A

-Modifies, packages, transports proteins/lipids
-Glycosulation (adding sugar resides) helps target where proteins will go and determine protein interactions with cell matrix

(packaging plant)

36
Q

What is the function of the proteasome?

A

Degrades denatured or other cytosolic proteins that are “tagged” (with ubiquitin) for destruction

(demolition crew)

37
Q

What is the function of the lysosome?

A

Digests (acid hydrolases) many macromolecules (protein, lipid, nucleic acid), damaged organelles and microbes

(demolition crew)

38
Q

What is the function of peroxisome?

A

Breaks down long chain fatty acids to make H2O2; catalase breaks down the H2O2 to water

(Demolition crew)

39
Q

In which organelle is DNA virtually entirely maternally inherited?

A

Mitochondria

40
Q

What is the function of mitochondria?

A

-Central roll in regulation of programmed cell death (apoptosis) and necrosis
-Makes ATP but can shift intermediates away from energy production to building lipids, nucleic acid and some proteins. This is based on cellular signals, nutrients, and O2 availability

41
Q

What does the plasma membrane contain?

A

A heterogeneous collection of different phospholipids, which are distributed asymmetrically

42
Q

What is the function of the plasma membrane?

A

-Cell-cell interactions: inflammation, sperm/egg
-Cell-matrix interactions: structural scaffold, can initiate intracellular second signals

43
Q

In regards to the protein component of the membrane, most are ___________ with _______ charged cytoplasmic domains that anchor to negatively charged membrane phospholipids

A

transmembrane (integral); positively

44
Q

T/F: Additional proteins can attach on the inside or outside of the cell membrane which anchors them to the cell

A

TRUE

45
Q

The extracellular face of the membrane and associated proteins are studded with carbohydrates to form ______ and ______ which together form the glycocalyxl.

A

glycolipids; glycoproteins

46
Q

What is the function of the glycocalyx?

A

-Chemical and mechanical barrier
-Helps in cell-cell and cell-matrix interactions

47
Q

In passive diffusion, what molecules are let through?

A

O2, CO2, small polar molecules, hydrophobic molecules

48
Q

What is the transporter for passive diffusion?

A

-Channel proteins - hydrophilic pores for rapid solute movement (passive transport)

-Solute concentration and/or electrochemical gradient moves solutes across membranes

49
Q

What is the membrane impermeable to?

A

Charged molecules

50
Q

What type of transporters do charged molecules use to get across the membrane?

A

Carrier proteins - bind solute –> conformational change –> transfers solute across (active transport- required ATP)

51
Q

In general, what is the typical state of a cell in terms of charge?

A

The inside of the cell is negatively charged and the outside is positively charged

52
Q

What maintains the cell gradient?

A

Na+ ATPases actively pump ions out of the cell to maintain this gradient and to prevent osmotic swelling

53
Q

What is the function of the cytoskeleton?

A

-Maintains shape, polarity, and organization of cellular components and creates a scaffold for proteins within the cell
-Like the highway connecting everything together

54
Q

Describe the actin microfilaments?

A

-Part of the cytoskeleton
- G-actin is most abundant cytosolic protein
- F-actin combine into fibrils that control cell shape and movement

55
Q

Describe the intermediate filaments

A

Fibrils giving tensile strength; many are cell specific

-Lamins (nuclear lamina)
-Vimentin (mesenchymal cells)
-Desmin (muscle cells)
-Neurofilaments (axons of neurons)
-Cytokeratins (epithelial cells)

56
Q

What are microtubules?

A

-Part of cytoskeleton
-Large fibrils allow movements of vesicles and organelles around cell
-Made of tubulin dimers
-Support for chromatid separation during mitosis
-Is the core of cilia and flagella

57
Q

Describe microtubule movement

A

-Negative end near the nucleus embedded in the centrosome paired with centrioles
-Positive end elongates or recedes outward into the cytosol

58
Q

How do two chemotherapy drugs, Taxol and Vincristine, work?

A

By stopping microtubule function so mitosis stops –> kills the cell.

59
Q

What is the function of occluding junctions (tight jxns)?

A

-Seals together as a barrier to prevent movement of molecules between cells
-Maintains cell polarity (apical and basal ends)

60
Q

What is the function of anchoring junctions (desmosomes)?

A

-Mechanically attach cells and their cytoskeletons (intermediate or microfilaments) to:
1. other cells (using cadherins)
2. the extracellular matrix - hemidesmosomes at the basal part of the cell are made of integrins that connect to basement membrane
-Distributes force through multiple cells and can influence cell shape and motility

61
Q

What is the function of communicating junctions (gap junctions)?

A

-Mediate passage of chemical or electrical signals between cells through pores made of connexin proteins
-Many small molecules pass through (ions, nucleotides, sugars, aa, vitamins, etc)
-Permeability reduced by lowered pH or increased intracellular calcium
-In cardiac muscle Ca2+ flows through gap junctions so cells contract as a unit

62
Q

What is the function of the extracellular matrix (ECM)?

A

-Mechanical support for cell anchorage and migration
-Control of cell proliferation and is thus a scaffold for tissue renewal- binds growth factor, water and minerals
-Created microenvironments (basement membrane is a boundy between epithelium and connective tissue)

63
Q

What is the extracellular matrix (ECM) comprised of?

A

-Interstitial matrix (made by mesenchymal cells)
-Basement membrane (made by mesenchymal and epithelial cells)

64
Q

What are the components of the ECM?

A

-Fibrous structural proteins (collagen and elastin) give tensile strength and recoil
-Water-hydrated gels (proteoglycans an hyaluronan) proivde resiliance, compressibility and lubrication
-Adhesive glycoproteins connect the matrix together

65
Q

Describe the adhesive glycoproteins and their function

A

-Fibronectin: bind ECM components to each other and to cells. In plasma, binds to fibrin within a blood clot
-Laminin: attaches cells to basement membrane and can alter growth and motility
-Integrins: transmembrane glycoproteins - cellular receptors for ECM components

66
Q

What must cells respond to in order to develop and adapt to their environment?

A

Extracellular signals

67
Q

What can loss of cellular communication lead to?

A

unregulated growth (cancer)

68
Q

What is paracrine signaling?

A

affects adjacent cells

69
Q

What is autocrine signaling?

A

cells signaling itself

70
Q

What is synaptic signaling?

A

neurons

71
Q

What is endocrine signaling?

A

hormones released into bloodstream to act on distant target cells

72
Q

What are the intracellular receptors?

A

Are activated by lipid soluble ligands that easily transit plasma membranes (vitamin D, steroid hormones)

73
Q

What are the cell surface receptors?

A

Generally transmembrane proteins. Ligand binding may:
-open ion channels
-activate G proteins
-activate an endogenous or associated enzyme
-trigger proteolysis or change protein binding to activate a latent transcription factor

74
Q

List the cell surface receptors

A

-Receptors associated with kinase activity
-Non-receptor tyrosine kinase
-G protein coupled receptors

75
Q

Describe the receptors associated with kinase activity

A

Add charged phosphate residues to target molecules (part of the receptor)

76
Q

Describe the non-receptor tyrosine kinase

A

Ligand binding recruits a tyrosine kinase molecules

77
Q

Describe the G protein coupled receptors

A

-Ligand binding –> binding of G protein exchanges GDP for GTP (active) –> other protein activation downstream
-Key pathways stimulated:
1. cAMP - 2nd messenger stimulates multiple effects
2. Inositol 3-phosphate (IP3) –> Ca2+ release

78
Q

T/F: Most signaling effects multiple pathways to induce multiple complementary effects (like a computer network)

A

TRUE

79
Q

Most pathways ultimately affect cell function by ____________ through transcriptions factors

A

changing gene transcription

-Signaling causes these proteins to undergo conformational changes (often due to phosphorylation), allows translocation to the nucleus, binding to DNA and alteration in transcription of genes

General Pathology (32 decks)

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