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PBL Week 1 > Cell in health & disease > Flashcards

Cell in health & disease Flashcards

1
Q

Define homeostasis

A

process by which internal variables are kept within a normal range of values.
e.g. blood pressure, temp, blood glucose.
Kept within normal ranges by using NEGATIVE FEEDBACK loop

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2
Q

Give example of positive and negative feedback loop

A

negative feedback - control of blood sugar by insulin
positive feedback loop - coagulation (clotting) cascade

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3
Q

What 9 housekeeping functions are needed to keep cells alive?

A

Protection- plasma membrane

Nutrition- methods of entering or exiting cell

Movement- cytoskeleton

Communication- cell receptors

Energy generation- ATP & mitochondria

Recycling & renewable- cell cycle, cell matrix, stem cells

Proteins- ribosomes, rough endoplasmic reticulum, smooth endoplasmic reticulum & Golgi body

Waste disposal- autophagy & heterophagy
Growth factors

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4
Q

List main functions of mitochondria

A
  1. Generation of ATP (by oxidative phosphorylation w/in inter membrane space).
  2. Source of molecules used to create proteins, nucleic acids and lipids (intermediate metabolism).
  3. Regulation of apoptosis (programmed cell death).
  4. Source of reactive oxygen species.
  5. Production of haem (for haemoglobin).
  6. Generation of heat.
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5
Q

What can damage mitochondria?

A

Toxins

lack of blood supply

Trauma

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6
Q

What is the function of lysosome?

A

membrane-bound organelles

contain enzymes which breaking down proteins, nucleic acids, carbohydrates & lipids.

function as the digestive system of the cell degrading material taken up from outside the cell & digesting obsolete components of the cell itself

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7
Q

What is the function of Golgi apparatus?

A

protein modifications

glycosylation of proteins and lipids

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8
Q

What is the function of rough endoplasmic reticulum?

A

Production of proteins & lipids

production of all of the cell organelles.

Ribosomes translate mRNA into proteins- these proteins fold in the endoplasmic reticulum.

Sugars can also be added to proteins in the RER.

If proteins misfold they are degraded or if this is excessive a stress response is triggered which can then initiate apoptosis.

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9
Q

What is the function of smooth endoplasmic reticulum?

A

site of steroid & lipoprotein synthesis.

Make drugs less hydrophobic allowing their export.

Release & storage of calcium ions that regulate muscle contraction.

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10
Q

Where is the cytoskeleton found? What are the 4 components ?

A

Found in cytoplasm
1. Actin microfilaments- controls cell shape & movement
2. Microtubules- forms cilia & flagella (i.e. movement) & participate in chromatid separation during mitosis
3. Nuclear membrane lamins- maintain structure of nucleus & regulate gene transcription
4. Intermediate filaments eg. cytokeratin- give strength to cells

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11
Q

What is the function of tight functions & anchoring junctions in relation to movement?

A

They hold cell together

Help w/ cell polarity

Does this by- desmosomes attach intracellular cytoskeleton of adjacent cells together using
Cadherine proteins at these junctions

Hemidesmosomes- attach cell to extra-cellar matrix

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12
Q

Give example of disease that affects tight junctions

A

Pemphigus vulgaris
Skin disease- antibodies are directed against Desmoglein-3
Keratinocytes fall apart
causes blisters & erosions

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13
Q

List the 7 ways in which molecules can move across membranes (nutrition) & give one example of a substance which uses each method

A
  1. Passive diffusion eg. oxygen, CO2, polar molecules (H2O) & hydrophobic molecules
  2. Fast channel proteins (using concentration gradients) eg. sodium.
  3. Slow carrier proteins eg. amino acids- use ATP
  4. Endocytosis (receptor or caveolae mediated) eg. LDL (receptor-mediated) and folate (caveolae-mediated).
  5. Exocytosis- large molecules
  6. Phagocytosis eg. bacteria.
  7. Trancytosis eg. antibodies from breast milk passing through intestinal cells into baby.
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14
Q

Which ion channel is damaged in the disease cystic fibrosis?

A

cystic fibrosis transmembrane regulator or CFTR
- responsible for chloride transport across cell membranes.
- leads to the secretion of sticky thick mucus

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15
Q

What is caveolae-mediated endocytosis?

A

uptakes vitamins & works by forming cavities in the plasma membrane produced by folding

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16
Q

What is receptor mediated endocytosis?

A

Uptake of LDL & transferrin (iron transporter).
Used to allow larger molecules to enter cell.
1.Receptors bind to the solute
2. The plasma membrane then folds & creates a vesicle
3.Vesicle then fuses w/ lysosome & releases its contents.
4. Receptors are recycled back to the plasma membrane

17
Q

What is transcytosis?

A

Movement of endoyctosed vesicles from the apical to the basolateral plasma membrane
i.e between the top & bottom/ sides of the cell

18
Q

List 4 mechanisms by which cells communicate

A
  1. Autocrine signalling- occurs at a neuromuscular junction- acetylcholine travels from nerve, across the synaptic space, to the receptor on muscle cell.
  2. Paracrine signalling- where a cell produces & secretes a messenger that binds to its own receptors. Occurs during cell development or to amplify a response. e.g. malignant tumours can survive by producing Growth Factors
  3. Endocrine signalling- Targets the cells in the immediate vicinity. e.g. Growth factors are involved in generation of blood vessels, wound healing, cell movement & cancer spread via this mechanism
  4. Synaptic signalling- involves a mediator being released into the bloodstream and travelling to a distant target e.g. FSH from the pituitary gland targets follicles cells in the ovaries.
19
Q

List 5 signal types which cells can respond to

A

Pathogens

Damage to neighbouring cells

Contact w/ neighbouring cells

Contact w. extracellular matrix

Secreted molecules e.g. growth factors

20
Q

List 4 possible outcomes following a ligand binding to a cell surface receptor & give 1 example of ligand associated w/ each

A
  1. Ion channel opens e.g. neurotransmitters at neuromuscular junction
  2. G-protein is activated e.g. hormones
  3. A tyrosine kinase is activated e.g. epidermal growth factors
  4. Latent transcription factor is activated e.g. interferon
21
Q

Explain 2 ways cells detect signals

A
  1. Cell surface receptors - usually transmembrane proteins.
  2. Intracellular receptors - transcription factors. These receptors are activated by lipid-soluble ligands e.g. Vit D, oestrogen, testosterone or steroid hormones
22
Q

Describe function of a transcription factor & given 1 example of a transcription which facilitates cell division & 1 which stops it

A

Transcription factor- protien which controls rate of transcription of genetic info from DNA to messenger RNA by binding to specific DNA sequence

MYC- facilities cell division

P53 stops division

23
Q

List 5 functions of growth factors

A
  1. Stimulate activity of proteins needed for cell survival, growth & division.
  2. Promote entry of cells into the cell cycle
  3. Relieve blocks on cell cycle progression
  4. Prevent apoptosis
  5. Enhance synthesis of cell components
24
Q

Give 2 examples of growth factors & explain how they work

A
  1. Epidermal Growth Factor - causes squamous epithelial cells of the epidermis to divide and wound healing to begin.
  2. Platelet Derived Growth Factor - causes scar tissue formation & supports healing
25
Q

List 4 functions of extracellular matrix

A
  1. Anchors cells- maintains their polarity & supports cell migration
  2. Control cell proliferation
  3. Provides a scaffold for tissue repair/ regeneration
  4. Created tissue microenvironment
26
Q

Describe the components of the extracellular matrix? Examples of conditions?

A
  1. Collagen - major structural protein that has triple helical structure which is strengthened by lateral cross links of covalent bonds which Need Vit C to maintain strength
    - E.g. Osteogenesis Imperfecta & Ehlers-Danlos Syndrome are genetic collagen defects.
  2. Elastin - provides elasticity = important in skin or heart valves. Elastin is made from a protein called Fibrillin.
    - E.g. Marfan’s syndrome- caused by mutation in fibrillar-1 gene- heart defects & lens dislocations seen
  3. Integrins - glycoproteins that cross cell membranes to link cells to the outside world. Important for cell shape, movement & division. Mediate interaction between white blood cells & lining of blood vessels in inflammation
  4. Hydrated gels - important for resistance to compression & lubrication. Also important in joint cartilage. e.g. proteoglycans
27
Q

What drives cell cycle progression?

A

Driven by proteins called cyclins & cyclin-associated enzymes called cyclin-dependent kinases (CDKs)

28
Q

Where are the checkpoints in the cell cycle & what happens at each checkpoint?

A
  1. G1/S (synthesis) checkpoint (start)- to check if nutrition, environment & cell size are favourable for replication & that all DNA is intact
  2. G2/ M mitosis checkpoint- to check that DNA has been completely replicated
  3. Metaphase/ anaphase checkpoint- to check that all DNA is intact & if all chromosomes are attached to mitotic spindle

*Look at diagram on notes

29
Q

What enforces cell cycle checkpoints & given example of 1 of these? What is the consequence of defective cell cycle enforcer?

A

Cyclin- dependent kinase inhibitors (CDKIs) stop cell cycle & enforce checkpoints

E.g. P16

Defective CDKI checkpoint proteins allow cells w/ DNA damage to replicate increasing risk of malignancy

30
Q

What is the difference between embryonic stem cells & adult stem cells?

A

Embryonic stem cells- totipotent stem cells- can give rise to all types of differentiated tissues

Adult stem cells- can only replace cells in the tissue in which they reside & these checks are found in stem cell niches in many organisms

31
Q

Give 2 properties of stem cells

A
  1. Self-renewal- the capacity of stem cells to retain their numbers
  2. Asymmetric division- capacity of stem cells to generate 2 daughter cells- 1 which will differentiate into mature cells & 1 which remains undifferentiated & retains self- renewal capacity
32
Q

Name some stem cell niches

A
  1. Area around blood vessels in bone marrow.
  2. Bulge region of hair follicle.
  3. Limbus of cornea
  4. Crypts of Gastrointestinal tract

PBL Week 1 (8 decks)

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