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Biology > Cell- och Molekylärbiologi > Flashcards

Cell- och Molekylärbiologi Flashcards

1
Q

Example of cell functionality in multicellular organisms

A

differentiation, apoptosis, gene regulation, cell division, coordination, sensing environment

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2
Q

What are intracellular signals also called?

A

Second Messengers

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3
Q

Name all forms of intercellular signaling methods

A

Contact dependent, Endocrine, Paracrine, Autocrine, Synaptic, Gap junction

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4
Q

Explain and name all parts of G-protein and GPCRs

A

GPCR = G-protein coupled receptor, is a transmembrane protein with seven transmembrane alpha-helices and a binding site on extracellular side.

G-protein, have three parts, alpha, beta, gamma. GPCR changes confirmation –> G-alpha part binds to GPCR and releases GDP. New GTP comes in and GPCR, G-alpha and G-beta/gamma produces each a signaling pathway.

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5
Q

What are enzyme coupled receptors?

A

Transmembrane enzyme that changes confirmation when ligand signal activates receptor. Usually a heterodimer that gets brought together to create a catalytic site in cytosolic side of cell.

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6
Q

Name different types of signaling reaction speeds

A

All-or-none, hyperbolic and sigmoidal.

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7
Q

Describe pros and cons of positive feedback and negative feedback in signaling pathways

A

Positive feedback –> no off button, good for differentiation.
Negative feedback –> switch that can sense change in concentration, and can work as an oscillator depending on length of delay

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8
Q

What is a Protein Kinase and Protein Phosphatase?

A

Protein Kinase adds a phosphate group to a specifik amnio acid. Protein Phosphatase removes a phosphate group.

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9
Q

Name enzymes that can regulate GTP

A

GAP = GTPase-activating protein which increases hydrolysis of GTP to become GDP.
GEF = guanine nucleotide exchange factors that promotes release of GDP from G-protein.

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10
Q

Describe cAMP and how it is catalyzed in cells.

A

Activated alpha-G-protein activates Adenylyl cyclase that catalyzes reaction that turns ATP into cAMP. (cyclic AMP)

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11
Q

Describe PKA and how it reacts with cAMP

A

cAMP-dependant Protein Kinase A (PKA) gets activated once cAMP reacts with it. Leads to release of two catalytic site units that travel through nucleus and activate CREB (CRE-binding protein). Cyclic AMP response elemet (CRE) is a sequence of nucleotides on DNA.

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12
Q

Name example of enzyme coupled receptor

A

Receptor tyrosine kinase have tyrosine kinase domain that can phophorylate tyrosine creating phophotyrosine docking sites.

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13
Q

Describe some general features of signaling pathways

A

Scaffold, amplify, integrate, spread, anchor, modulate

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14
Q

Describe nucleus receptors

A

They typically have ligand binding domain that has an inhibitory protein which releases when ligand attaches. Coactivator protein then attaches and makes it possible for receptor to bind to DNA-segment.

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15
Q

Name the sides of epithelial cells

A

Apex side towards extracellular medium and lateral surfaces that are attached to basal lamina.

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16
Q

Name the types of cell-cell junctions

A

Tight junction, adherence junctions. desmosome, gap junctions

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17
Q

Name the types of cell-matrix junctions

A

Actin-linked-cell-matrix junction and hemidesmosome

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18
Q

Name the overall 4 categories of junctions

A

tight junctions, cell-cell anchoring junction, channel forming junction and cell-matrix junction.

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19
Q

Name the transmembrane adhesion protein associated with cell-cell junctions and cell-matrix junctions.

A

Cadherin (cell-cell) and Integrin (cell-matrix)

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20
Q

Describe in detail what cadherins are

A

They are homophillic and sorts themselves out by only binding to their counterpart.
Have several domains with hinge region where Ca2+ can bind to make more rigid. Works a bit like velcro.
More cadherins = stronger connection between cells, they become more centered when in clusters. Binding occurs at N-terminal tips.
Intercellular part binds to alpha-catenin which binds to actin filament. If there is tension alpa-catenin stretches out and vinculin protein can bind wich then binds to more actin filaments.
Forms adhesion belts around epithelial cells.

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21
Q

What are non-classical cadherins?

A

Cadherins that are used in desmosomes and binds to intermediate filaments instead of actin filament.

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22
Q

What are adaptor proteins?

A

Proteins in between filaments and junction protein such as vinculin and alpha-catenin.

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23
Q

What are gap junctions made of and what are the different types?

A

6 connexins that form a connexon and two connexons form a channel. There can be homomeric and heteromeric connexons and homotypic and heterotypic channels.

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24
Q

What is the extracellular matrix usually made of?

A

GAG or glycosaminoglycans which are large charged polysaccharides that are made of the repeating disaccharide amino sugar + uronic acid.

ECM is also made of collagens which are three tripple alpha helices where every third amino acid is glycerin. Provides connective tissue with mechanical strength.

Glycoproteins which are GAG + protein and are used to attach epithelial to basal lamina.

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25
Q

Describe the components used to attach epithelial to the basal lamina.

A

Laminin which is a glycoprotein that connects to itself and perlecan and integrin aswell as nidogen. Type IV collagen binds to itself and nidogen aswell as perlecan. This creates a mesh in which cell cans adhere to the basal lamina.

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26
Q

What are integrins and how do they work?

A

Integrins are transmembrane receptors that are split into two parts, alpha and beta. Once activated from the cytosolic side, the two chains will “split” and they can then connect to laminin. Can be activated by signal molecule kindlin or other intra/extracellular signals. They are used in hemidesmosome and actin-linked-cell-matrix junction. In actin-linked-cell-matrix junction integrins bind to the protein Talin which then binds to actin filament by vinculin.

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27
Q

Describe a summary of fertilization process

A

Egg is released from ovary and travels in oviduct where it gets fertilized by sperm. Then cleavage begins and the first cells divide. The morula enters the uterus and then once its a blastocyst (blastula for non mammals) , it attaches to the uterus wall.

28
Q

What are the 4 essential processes that make up embryo for an multicellular organism?

A

cell proliferation, cell specialization, cell interaction, cell movement

29
Q

What are interchangeable proteins between species called?

A

Homologous

30
Q

What are the different gastrulation layers?

A

Ectoderm, mesoderm and endoderm

31
Q

How does the same signal result in different outcome for cells?

A

There might be a combination of other signal or the cell could have a sort of cell memory where the order of incoming signal is important for differentiation.

32
Q

How does cell generate cell diversity?

A

Lateral inhibition (for over around 1mm then is called morphogen), sequential induction, asymmetric cell division, maternal-effect-genes, and lateral inhibition using delta/notch contact dependent receptors.

33
Q

Name the 3-axes in embryo growth

A

animal-vegetal (AV, inside/outside), anteroposterior (AP, head/tail) and dorsal-ventral (DV, back/stomach)

34
Q

Describe the segment-polarity genes of Drosophila

A

Morphogens induce gap-genes and then pair-rule genes. The Wnt and Hedgehog pathways codes for hedgehog proteins that induces Wnt gene to produce Wnt proteins that signals for the production of the engrailed proteins which then induces the hedgehog pathway. This creates the segmentation-polarity genes and works as positional labels for differentiation. It is the hox genes (Homeotic selection genes) that then permanently differentiates cell.

35
Q

What does the Hox genes encode for?

A

Hox proteins which are transcriptional regulators. They differentiate the cell into a specific type.

36
Q

How can Hox genes be regulated?

A

With Trithorax proteins that binds to chromatin to maintain Hox genes while Polycomb proteins represses Hox on chromatin.

37
Q

Exlplain the formation of the Spemann’s organizer

A

Lose VegT mRNA abd Wnt11 act as morphogen at the vegetal pole. Once sperm enters the Wnt11 mRNA rotates. Where Wnt11 and VegT overlaps is where the Spemann’s organizer is. It defines the dorsoventral axis and is located on dorsal pole. It produces morphogen to create the mesoderm.

38
Q

Which stemcells are totipotent, pluripotent and multipotent?

A

The zygote cell is totipotent, embryonic stem cell are pluripotent, and somatic stem cells are multipotent (these are the ones found in stem cells niches).

39
Q

Explain how different cells in the small intestine are made from stem cells

A

Intestinal stem cells are in small spaces called crypts. A stem cell spontaneously becomes a paneth cell which produces Wnt-signals that tells the cells within proximity to keep on dividing. EphB receptor proteins gene induced by Wnt expresses ephrin receptors which repel each other forming the crypts (u-shape).

40
Q

What is the process where the first blood vessels form called?

A

Vasculogenesis

41
Q

What is the process where new blood vessels are formed and how does it work?

A

Angiogenesis. When cells have low oxygen they start producing hypoxia-induced factor 1-aplha (HIF1alpha) which stimulates transcription of vascular endothelial growth factor (VEGF). The endothelial cell senses the concentration gradient of VEGF and tells the endothelial cells to proliferate and produce proteases to digest through the basal lamina. Capillary sprout are led by the stalk cell to form new vessels.

42
Q

What are red blood cells also called?

A

Erythrocytes

43
Q

Name the three types of leukocytes

A

Monocytes, Granulocytes and Lymphocytes

44
Q

Name the types of Monocytes and their roles

A

Macrophage and dendritic cells. Macrophage rests in connective tissue and are phagocytes that can take up invasive cells, they are long lived in contrast to neutrophils. Dendritic cells take apart components and show them on their receptor for T-cell activation.

45
Q

Name the types of Granulocytes and their roles

A

Eosinophils which kills multicellular parasites and certain infections. The release reactive oxygen species and enzymes that kill parasites once surrounded by eosinophils.

Basophils produces histamine and serotonine to induce inflammatory response as well as releasing enzymes to improve bloodflow and prevent blood clots.

Neutrophil are short lived phagocytes that exist inte the blood.

46
Q

Name the types of Lymphocytes and their roles

A

B-cell which produces antibodies. T-cell which recognizes antigen so it can kill infected cells as swell as invasive species. Natural Killer cells can recognize MHC 1 type receptor but also kill stressed cells even without, hence natural killers. Analogous to cytotoxic T-cells.

47
Q

How are these cells made?

A

By Hemotopoeic stem cells that are attached to stromal cells in bone marrow.

48
Q

Describe a virion

A

Single virus that has RNA or DNA in capsid. They can also have an membrane envelope around usually formed by budding.

49
Q

What are the differences between G+ and G- bacteria?

A

G+ have a single cell membrane but with a large wall made of peptidoglycan- G- have two cell membranes with some peptidoglycans in the middle.

50
Q

Name the different methods of horizontal gene transfer

A

Transformation, takes in DNA by taking from environment.
Transduction, a virus implants DNA to bacterio, for example bacteriophage.
Conjugation, two bacterial cells conjugate and sends DNA to each other.

51
Q

What are protozoa?

A

Single cell eukaryotes can have more than a single form (yeast and mold form) and have a more elaborate lifecycle.

52
Q

What is the epidermis made of?

A

Basal cells (stem cells), prickle cells, granula cells and squames.

53
Q

What are the two types of immune response?

A

Adaptive and innate immune response.

54
Q

What are some other factors that might contribute to making it harder for invasive pathogen to infect?

A

Epithelial cells block passage to bloodstream. Other bacteria compete for nutrients. Tight junction blocks passage. Epithelial cell can excrete mucus (like in lungs) or regulate acidic pH. Epithelial cells secrete defensins.

55
Q

How does antibiotics work and how do they gain ressistance?

A

Antibiotics usually target cell wall synthesis by inhibiting a specific signaling pathway. Resistance can be gained by producing proteins that bind to antibiotic and degrades it, by changing the enzyme that is coupled with the signaling pathway that is inhibited by antibiotic and by pumping the antibiotic out of the cell.

56
Q

What are PRR and PAMP and which cells uses them for example?

A

PRR stands for Pattern Recognition Receptor that recognizes Pathogen Associated Molecular Patterns and are used by macrophages and neutrophils.

57
Q

What is the complement system?

A

3 pathways that lead to the cleavage of the enzyme C3 which subsequently leads to the formation of a hole in membrane of pathogen as well as recruitment of inflammatory cells, stimulation of adaptive immune response, coating of microbe and induction of phagocytosis.

58
Q

What are the 3 pathways that lead to the activation of the complement system?

A

The classical pathway, antibodies bind to an antigen on cell surface.
The Lectin pathway, floating PRR recognizes PAMP on cell surface.
Alternate pathway, the surface molecules activates themselves C3 cleavage.

59
Q

Explain the adaptive immune system

A

Dendritic cell phagocytes pathogens by recognizing PAMPs on PRR and then proteolyses them into small fragments which are shown on the dendritic cell surface on MHC 2 receptors. (Major Histocompability Complex) These are recognized by naive T-helper cells by TCR (T-cell Receptor). T-helper cell can then activate cytotoxic T-cells and B-cells to produce antibodies. Some B-cells are T-cell dependent while others are not. If antigen stimulates B-Cell Receptor (BCR) which is itself an antibody, then the cells starts secreting antibodies. If a B-cell needs T-cells activation then it will present its antigen on MHC 2 and get recognized by T-helper cell. Cytotoxic T-cells will recognize antigen that is on MHC 1 and will begin killin infected cells. Each of these types of cell either becomes effector cell or memory cell.

60
Q

Describe antibodies

A

Antibodies (Immunoglobulins) have a light and heavy chain. On these chains are variable and hyper variable regions at the tip (near N-terminal). These variable parts are made by the combination of different gene segments. Heavy chain have 40V 25D 6J and 5C. Light chain have 40V 5J 1C. More combinations are made by random loss of nucleotides during gene recombination and is called junctional diversification.

61
Q

What are tight junctions made of?

A

Occludin and Claudin

62
Q

How are transcription factors classified?

A

There are transcription regulator, inhibitors and activators. Regulators can bind to DNA helix like Leucine zipper and Helix-turn-Helix protein.

63
Q

Explain the role of NO in cell signaling

A

Acetylcholine activates a GPCR that makes the cell produce NO which diffuses to nearby cells and binds to guanylyl cyclase and transforms GTP to cGMP which relaxes smooth muscle cells and increases blood flow.

64
Q

How are stromal cells attached to hemotopoeitic cells?

A

By the anchoring protein Kit

65
Q

Explain delta notch lateral inhibition

A

Cell produces equal amounts of delta and notch receptor. Delta is a transmembrane signal protein that connects to notch receptor and inhibits the cell from specializing and the production of delta proteins.

Biology (2 decks)

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