Lysosomes Flashcards

1
Q

What is the key function of lysosomes?

A

To carry out digestive, hydrolytic reactions

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2
Q

Give some examples of enzymes found in lysosomes and what molecule they break down

A
Proteases (proteins)
Lipase (lipids)
Glycosidases (carbohydrates)
Nucleases (nucleic acids)
Phosphatases (phosphates)
Sulfatases ( sulfates)
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3
Q

What are the conditions like inside the lysosome?

A

Acidic (pH4-5)

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4
Q

What does heterogenous contents mean?

A

Lots of different molecules inside

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5
Q

Give examples of membrane proteins found in lysosome membranes

A
V-ATPase
Ion channels
Cholesterol transporters
Sugar transporters
Nucleoside transporters
Amino acid transporters
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6
Q

Give examples of molecules found on the lysosome membrane

A

Small GTPases
Tethering factors
SNAREs

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7
Q

What is a SNARE responsible for?

A

The final fusion process in the residue targeting process

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8
Q

What does V-ATPase do?

A

Pumps proteins into the lysosome (to make it acidic)

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9
Q

How do lysosomes move around the cell and what must the have to facilitate this?

A

Microtubules so must contain motor signals to attach to the micro tubules

Also signalling complexes ( involved in immune response and metabolic signalling)

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10
Q

Where are transcription factors regulated?

A

On the surface of lysosomes

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11
Q

What cell contains melanosomes and what is the clinical feature when defective?

A

Melanocyte- ocular and Cutaneous hyperpigmentation

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12
Q

Give the features of melanosomes

A
  • Very high conc of melanin

- Formed in a four-step process

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13
Q

Once formed where are melanosomes transported to?

A

Keratinocytes

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14
Q

How are extracellular substrates delivered to the lysosome?

A

Endocytosis
Fluid phase endocytosis of molecules and lipoproteins (inducts receptor- mediated endocytosis)
- phagocytosis of small particles (> 50 micrometers)

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15
Q

How are intracellular substrates moved around the lysosome?

A

Microautophagy
invagination
Macroautophagy
Selective protein transport

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16
Q

What does microautophagy mean?

A

Self eating

17
Q

What does invagination mean?

A

Where budding takes place into the lysosomes

18
Q

How does macroautophagy work?

A

Cytosol or organelles wrapped in the ER membrane which then fuses with the lysosomal membrane

19
Q

What group of molecules takes part in receptor-mediated endocytosis?

A

Low-density lipoproteins

20
Q

Give the steps of phagocytosis

A

1- particle binds to the cell surface
2- particle is engulfed (plasma membrane wraps itself around the particle - forms a phagosome)
3-lysosome fuses with the phagosome (phagolysosome)
4-digestion

21
Q

What gets broken down in phagocytosis?

A
  • Bacteria
  • dead cells
  • ageing blood cells (B-cells, RBCs)
22
Q

Are macrophages able to pick up particles bigger than themselves?

23
Q

Give the specialist names for the autophagy of mitochondria

24
Q

Give the specialist names for the autophagy of peroxisomes

25
Give the specialist names for the autophagy of ribosomes
Ribophagy
26
Give the specialist names for the autophagy of lipid droplets
Lipophagy
27
Give the specialist names for the autophagy of chloroplasts
Chlorophagy
28
Give the specialist names for the autophagy of infectious particles
Xenophagy
29
How does HIV deliver its virus?
Binds directly with the cell membrane
30
How does influenza deliver its virus
Taken up by endocytosis and the drop in pH means that the endosomal and viral membranes break, releasing the viral contents
31
How does polio and adenovirus deliver its virus?
Endocytosis
32
What are the steps in the secretory pathway?
- the mannose sugar is added in the Golgi body - the sugar is recognised by the MGP receptor - the receptor/sugar complex forms a clathrin-coated pit (and consequently a Clathrin coated vesicle) - this vesicle then carries the complex into the lysosome
33
What causes most lysosomal storage disorders?
The lack of an enzyme in the lysosome which leads to the accumulation of a substrate
34
What can mutations in lysosomal hydrolayses cause?
Substrate accumulation
35
What does I cell disease mean?
No lysosomes are made so nothing can be digested
36
What are the symptoms of I cell disease?
Skeletal abnormalities Developmental delay Enlarged liver and spleen
37
What causes death (usually) from I cell disease?
Pneumonia or congestive heart failure
38
What is I cell disease caused by?
A deficiency of UDP-N (acetylglucosamine)
39
What does mutations in the M6P tag in the golgi cause?
Persistant stuttering