Structure and function of lysosome

By
Prof (Dr.) Ichha Purak
Department of Botany
Ranchi Women’s College, Ranchi

8/20/2020 Structure and function of Lysosome 2
CONTENTS
DEFINITION
INTRODUCTION
DISCOVERY OF LYSOSOMES
DISTRIBUTION / LOCATION OF LYSOSOME
ORIGIN / SYNTHESIS OF LYSOSOME
SHAPE AND SIZE OF LYSOSOME
CHEMICAL COMPOSITION OF LYSOSOME
LYSOSOMES ARE KNOWN AS SUICIDE BAGS
HOW THE CELL IS PROTECTED FROM LYSOSOME RUPTURE
COMMON FUNCTIONS OF LYSOSOME
TYPES OF LYSOSOMES
DISORDERS IN HUMAN RELATED WITH LYSOSOME
SUMMARY
QUESTIONS
BOOKS CONSULTED
REFERENCES

The term Lysosome is derived from Greek word lysis ( means destroy or dissolve)
and soma ( means body).
Lysosome is an organelle which can break down almost all types of
macromolecules ( as Nucleic acids, proteins, polysaccharides, lipids etc.).
Lysosomes are spherical, membrane bound organelles which are generated from
trans Golgi apparatus ,cut off as vesicles.
Lysosome enclose or contain a number of (about 50) hydrolytic enzymes and so
function as part of the recycling system of the cell cleaning up debris and wastes .
The Lysosomes are made up for intracellular and extracellular digestion .
DEFINITION

INTRODUCTION/STRUCTURE OF LYSOSOME
The cytoplasm of animal cells contain one to many tiny, spheroid or irregular
shaped, membrane bounded vesicles or organelles known as lysosomes.
They digest the material taken in by endocytosis ( such as phagocytosis,
endocytosis and pinocytosis), parts of the cell (by autophagy) and extracellular
substances.
Lysosomes are membrane enclosed compartments having hydrolytic enzymes used
for controlled intracellular digestion of macromolecules at acidic pH (about 5 in its
interior)
The acidic environment of lysosome is due to ATP-dependent proton pumps which
are present in the membrane of lysosome, which accumulates protons (H+) inside
the lysosomes.

DISCOVERY OF LYSOSOMES
Lysosomes were discovered by a Belgian biologist, Christian de Duve in 1950s.
De duve was awarded a share of 1974 Nobel Prize for Physiology and Medicine for
his discovery of lysosomes and other organelles known as peroxisomes
Lysosomes were initially discovered by the biochemical fractionation of cell extracts.
Later on they were seen clearly under electron microscope as membrane enclosed
vesicles.

DISTRIBUTION/LOCATION OF LYSOSOME
Lysosome is a membrane bound organelle found in many animal cells. Lysosomes are
absent in erythrocytes.
Lysosomes are distributed through out cytoplasm or between trans face of Golgi
Apparatus and Plasma membrane
Lysosomes are generally not present in plant cells.
In plant cells delicate membranous cavities are found known as vacuoles.
In young plant cells (meristematic cells) numerous small vacuoles are present along
with cell organelles like mitochondria, plastids , microbodies etc.
In mature plant cell (permanent tissue) small vacuole fuse to form large vacuole, as a
result the cell organelles and nucleus are pushed towards plasma membrane . In
plant cells role of lysosome is undertaken by the vacuoles. Vacuoles also contain
hydrolytic enzymes
Vacuole is filled with cell sap and help in excretion of waste and excess water. Cell
sap has many organic and inorganic substances.

In plants, vacuoles serve many functions, which make them multifunctional
organelles.
However, they also have basic properties similar to lysosomes found in the cells of
animal.
Vacuoles are also of acidic nature and contain various hydrolytic enzymes for
breaking different types of molecules
There are different types of vacuoles that serve different functions in plant cells .
Sap vacuoles - these vacuoles store salt, minerals and nutrients.
Contractile vacuoles - involved in osmoregulation and excretion,They are formed and
burst after some time, take up the function of excretion and osmoregulation .
Food vacuoles - involved in the digestion of nutrients , these vacuoles contain
digestive enzymes that digest these nutrients.

BIOGENESIS / SYNTHESIS OF LYSOSOME
Primary lysosomes originate from the Golgi apparatus (Trans side) in the form of
vesicles
Lysosomes appear initially as spherical bodies about 50-70nm in diameter and are
bounded by a single membrane.
Several hundred lysosomes may be present in a single animal cell.
lysosomes are formed by the fusion of transport vesicles budded off from the trans
Golgi network with endosomes, which contain molecules taken up by endocytosis at
the plasma membrane.
Lysosome membrane and the enzymes present within are synthesized separately .

Lysosome proteins are synthesized as other proteins but on ribosomes attached
to Endoplasmic Reticulum. The mRNA after transcription from DNA segments and
translocation to cytosol attach with smaller subunit of ribosome and due to
presence of signal codons in mRNA, ribosome becomes attached to Endoplasmic
Reticulum, to complete synthesis of polypeptide in its lumen.
Polypeptide becomes tagged with mannose-6-phosphate within the Golgi
apparatus and is then targeted to lysosome . As a result, vesicles containing these
enzymes bud off from the Golgi apparatus. The enzymes which help in
attachment of mannose-6-phosphate are N-aetyleglucoseamine
phosphotransferse and N-acetyleglucosamine phosphoglycosidase.

lysosome formation
Lysosomes form by budding off from the membrane of the trans-Golgi network. Macromolecules
(i.e., food particles) are absorbed into the cell in vesicles formed by endocytosis.
The vesicles fuse with lysosomes, which then break down the macromolecules using hydrolytic
enzymes. COURTSEY Encyclopædia Britannica, Inc.

Lysosomes are usually meeting places where several streams of intracellular traffic
take place .
Digestive enzymes are delivered to them by a route that leads outward from the
ER via the Golgi apparatus
This vesicle, now in the cytoplasm, then binds with a late endosome which is
another acidic, membrane-bound organelle.
The late endosome has proton pumps within its membrane that keep its internal
environment acidic.
The low pH causes dissociation of the protein from the mannose-6-phosphate
receptor. This receptor can then be recycled back to the Golgi apparatus.
The phosphate group is also removed from the mannose-6-phosphate tag, to
prevent the whole protein returning to the Golgi apparatus.

The late endosome can eventually mature into a lysosome, after it has received the
enzymes from the Golgi apparatus.
Lysosomes act as the waste disposal system of the cell by digesting obsolete or un-
used materials in the cytoplasm, from both inside and outside the cell.
Material from outside the cell is taken-up through endocytosis, while material from
the inside of the cell is digested through autophagy
SHAPE AND SIZE OF LYSOSOME
Lysosomes are acidic membrane bound spherical or irregular organelles about 1
μm in diameter
The size of lysosomes varies from 0.1 μm to 1.2 μm.
Lysosomal enzymes are synthesized in the endoplasmic reticulum (ER), transported
to the Golgi apparatus, and then tagged for lysosomes by the addition of mannose-
6-phosphate label.

CHEMICAL COMPOSITION OF LYSOSOMES
Lysosomes contain a number ( about 50-60) of
Acid hydrolases such as nucleases, proteases,
glycosidases, lipases, phosphatases, sulfatases
and phospholipases.
These enzymes take up the function of degrading
or breaking macromolecules or biological matter.
The acid hydrolases are hydrolytic enzymes that
are active under acidic conditions.
The lumen is maintained at an acidic pH by an H+
ATPase in the membrane that pumps H+ into the
lysosome
Figure 13-31 Lysosomes
From : Molecular Biology of the
Cell. 4th edition.Alberts B, Johnson
A, Lewis J, et al.New York:
Garland Science; 2002
Transport from the Trans Golgi
Network to Lysosomes

The lysosomal enzymes are grouped in six main categories
Nucleases - Nucleases are important enzymes that hydrolyze nucleic acids. Nucleases are
divided in to deoxyribonuclease (acts on DNA) and ribonuclease which hydrolyses RNA.
Hydrolysis action on nucleic acids results in the production of sugars, nitrogen bases as well as
phosphates.
Proteases - Proteases includes enzymes like collagenase and peptidases that acts on proteins
converting them to amino acids
Glycosidases - Glycosidases like beta galactosidase act on the glycosidic bonds of
polysaccharides converting polysaccharides to monosaccharides. For instance, the enzyme
galactosidase acts on such bonds converting lactose to glucose and galactose.
Phosphatases - Good examples of Phosphatases are acid phosphodiesterases. These are
important enzymes that act on organic compounds releasing phosphate in the process if the
compound has a phosphate group.
Lipases - Lipases include esterases and phospholipiases that act on lipids to produce acids
and alcohol
Sulphatases - Sulphatases are enzymes that act on organic compounds to release sulphates

LYSOSOMES ARE KNOWN AS SUICIDE BAGS
Lysosomes can digest materials taken up from outside the cell, but some times
when they burst ,their enzymes digest their own cell so are called suicidal bags of
the cell.
Lysosomes cannot digest themselves - Most of the proteins present in its
membrane contain high amounts of carbohydrate-sugar groups.
Because of the presence of these groups, digestive enzymes are unable to digest
the proteins present on the membrane.
HOW THE CELL IS PROTECTED FROM LYSOSOME RUPTURE
Lysosomes contain a wide variety of hydrolytic enzymes (acid hydrolases) that break
down macromolecules such as nucleic acids, proteins, and polysaccharides. These
enzymes are active only in the lysosome’s acidic interior; their acid-dependent activity
protects the cell from self-degradation in case of lysosomal leakage or rupture, since
the pH of the cell is neutral to slightly alkaline.

COMMON FUNCTION OF LYSOSOME
The main function of lysosomes is the digestion of internal (non-functional cell
organelles) and external (food, bacteria, leukocytes, debris) material.
The processed material is either released to the cytoplasm, secreted, or stored in
lysosomes. Lysosomes break down macromolecules into their constituent parts,
which are then recycled and reused
The hydrolytic enzymes contained within the lysosome allow foreign particles to be
destroyed.
Lysosomes play an important role in phagocytosis.
When macrophages phagocytose foreign particles, they contain them within a
phagosome.
The phagosome then bind with a lysosome to form a phagolysosome.

These enzymes are critical in oxygen-independent killing mechanisms.
Lysosomes also help to defend against pathogen entry via endocytosis by
degrading pathogens before they reach the cytoplasm.
Lysosomes are heterogenous in shape and size. Diversity of lysosomes reflect
wide variety of digestive functions mediated by acid hydrolases for intra and
extracellular debris.
There are a number of processes through which lysosomes digest material.
These include: Endocytosis
In endocytosis, invagination of the plasma membrane of the cell results in the creation
of an endocytic vesicle that engulfs different types of extracellular molecules.
In phagocytosis (a type of endocytosis) large molecules/microorganisms like bacteria
are engulfed in a vacuole (phagosome).
In pinosomes (another type of endocytosis) a small amount of the surrounding fluid and
solute molecules are pinched off as pinosomes (pinocytic vesicle).

TYPES OF LYSOSOMES
A) There are two types of lysosomes : Secretory lysosomes and Conventional
Lysosomes
Secretory lysosomes are found in different cells as the Immune system such as T
lymphocytes, derived from the hemopoietic cell line .Secretory lysosomes are a
combination of conventional lysosomes and secretory granules. They differ from
conventional lysosomes in that they contain the particular secretory product of the
cell in which they reside.
Conventional lysosomes are involved in the dismantling and re-cycling of various
substrates presented to them through endocytocis, phagocytosis and by
autophagosomes. They are responsible for returning many amino acids to the
system.

B) There are two other types of lysosomes :
Primary lysosomes (storage grannules) - are formed from Golgi apparatus appearing
as small vesicles. These lysosomes and are surrounded by a single phospholipid
layer and contain acid hydrolases.
Secondary lysosomes (Digestive vacuoles) - are formed when primary
lysosomes fuse with phagosomes /endosome .
Endosomes are formed by invagination of plasma membrane carrying some
extracellular particles .
Compared to primary lysosomes, secondary are larger in size and capable of
releasing their content (enzymes) outside the cells where they degrade foreign
material.

Lysosomal storage diseases are genetic disorders in which a genetic mutation
affects the activity of one or more of the acid hydrolases.
In such diseases, the normal metabolism of specific macromolecules is blocked
and the macromolecules accumulate inside the lysosomes, causing severe
physiological damage or deformity.
DISORDERS /DISEASES IN HUMAN RELATED WITH LYSOSOME
LSDs are inherited disorders resulting from a lack of specific enzymes that break
down certain lipids (fats) or carbohydrates (sugars) in the body cells.
The scientific community has identified more than 40 types of lysosomal storage
diseases, which show various types of symptoms if some hydrolases for destroying
macromolecules are not synthesized in the cell .

Following are some examples of Types of Lysosomal Storage Diseases/
Disorders
Gaucher disease
Niemann-Pick disease
Tay-Sachs disease
Fabry disease
Mucopolysaccharidoses (MPS) diseases
Pompe disease
Hurler's disease
Inclusion –cell disease (I-cell disease)

Gaucher disease is an autosomal recessive inherited disorder of metabolism
where a type of fat (lipid) called glucocerebroside ,accumulates in the cell as it
cannot be degraded due to enzyme glucocerebrosidase is not formed by the cell.
A person will get Gaucher Disease if both parents are carriers of the disease.
Major signs and symptoms of Gaucher’s disease include enlargement of liver and
spleen , a low number of red blood cells (anaemia), decrease in blood platelets ,lung
disease, and bone abnormalities such as bone pain, fractures, and arthritis.
Disease can be managed upto some extent by enzyme replacement therapy
although it is expensive and enzymes are to be administered by intravenous infusion

Niemann-Pick is a rare, inherited disease that affects the body's ability to
metabolize fat (cholesterol and lipids) within cells.
Niemann-Pick disease also called sphingolipidose in which harmful quantities of
fatty substances or lipids, accumulate in the spleen, liver, lungs, bone marrow,
and brain.
The Niemann-Pick gene mutations are passed from parents to children as
autosomal recessive inheritance.
This means that both mother and father must have defective form of the gene
and pass it to child to become affected.

Tay-Sachs disease is a rare disorder passed from parents to child.
The gene that is mutated in individuals with Tay–Sachs disease, is HEXA,which
codes for enzyme (N-acetylhexosaminidase A(Hex-A) which cleaves a terminal
N-acetylgalactosamine group from a brain ganglioside GM2 , changes to brain
ganglioside GM3 (Figure 4.5 from I Genetics by P J Russel ) but when gene is
defected, enzyme is not formed and Ganglioside GM2 accumulates and causes
Tay Sach Disease .
So level of unprocessed gangliosides increases in child’s brain causing neurons
to swell and produce different clinical symptoms.
A cherry-coloured spot on the retina, surrounded by a white circle helps early
diagnosis of the disease.

Courtsey : iGenetics by P J Russel

Fabry disease is caused by mutations in the GLA gene.
This gene provides instructions for making an enzyme called alpha-
galactosidase A which normally breaks down a fatty substance called
globotriaosylceramide.
Mutated GLA gene alters the function of enzyme preventing breakdown of
globotriaosylceramide, so accumulates in cells lining blood vessels
skin,kidneys,heart and nervous system.
Fabry disease may cause pain, especially in the hands and feet, clusters
of small, dark red spots on the skin called angiokeratomas, a decreased
ability to sweat (hypohidrosis), cloudiness of the front part of the eye
(corneal opacity), and hearing loss .

Mucopolysaccharidoses (MPS) diseases is caused by absence or
malfunctioning of lysosomal enzyme needed to break down glucosaminoglycans
(GAGs) or muopolysaccharides .
These long chain sugars occur within cells of bone, cartilage ,tendons , cornea,
skin and connective tissue and in fluids that lubricate joints.
Because of absence of enzyme, GAGs collect in the cells, blood and connective
tissues which affect organ and system functioning
Pompe disease is caused when enzyme that can break down glycogen is not
synthesized .
Too much of glycogen accumulated damages muscles and organs .
This disease causes muscle weakness and trouble breathing and mostly affects
liver and heart .
Pompe disease results from a mutation in the GAA gene that allows the complex
sugar glycogen to accumulate in and damage muscles.

Hurler’s disease also known as mucopolysaccharidopsis Type IH (formerly known
as gargoylism) is a genetic disorder that results in build up of large sugar molecules
called glycosaminoglycans in lysosome .
The inability to break down these molecules result in variety of symptoms, caused
by damage of organ systems such as nervous system , skeletal system, eyes and
heart .
Hurler syndrome was first described by German pediatrician, Gertrud Hurler in
1919.
It is one of the 11 disorders of the mucopolysaccharidoses (MPS).

.
.
Inclusion –cell disease (I-cell disease )is caused by a mutation in the GNPTA
gene that leads to a deficiency in the enzyme UDP-N-acetylglucoseamine-1-
phosphotransferase.
I-cell disease is inherited as an autosomal recessive genetic trait. In this disease
almost all of the hydrolytic enzymes are missing from the lysosome of fibroblasts
and their undigested substrates accumulate in lysosomes.
I-cell disease (mucolipidosis II) is a rare inherited metabolic disorder
characterized by coarse facial features, skeletal abnormalities and mental
retardation. The symptoms of I-cell disease are similar to but more severe than
those of Hurler syndrome.

Summary
Lysosomes process unwanted material into other substances that can be utilized by
the cell.
Lysosomes behave as cell’s recycling centre .
Lysosomes perform intracellular digestion of macromolecules of the cell.
Lysosomes contain unique membrane proteins and variety of hydrolytic enzymes .
The acidic pH ( about 5) of lysosome is maintained by an ATP driven H+ pump in
the lysosomal membrane.
Lysosomal proteins are synthesized on ribosome attached to ER ,transported through
Golgi apparatus and then carried from the trans Golgi network to late endosomes by
means of clathrin-coated transport vesicles.
The proteins destined for lysosomes are tagged by mannose -6-phosphate for
packaging into specific departing vesicles for lysosomal hydrolases.

Enzymes in the Golgi recognize and tag lysosome-bound proteins by
phosphorylating the mannose residues.
The lysosomal hydrolases contain N-linked oligosaccharides that are covalently
modified in a unique way in the cis Golgi network so that their mannose residues
are phosphorylated.
The mannose-6-phosphate groups are recognized by the mannose-6-phosphate
receptors (MPR) at the TGN
The mannose -6-phosphate receptors shuttle back and forth between the trans
Golgi network and these endosomes.
The low pH in the late endosome dissociates the lysosomal hydrolases from these
receptors, making the transport of the hydrolases unidirectional

MCQs (MULTIPLE CHOICE QUESTIONS ) ON LYSOSOMES
1. Which of the following organelle control intracellular digestion of macromolecules with the help of
hydrolytic enzymes?
a) Plastid
b) Peroxisome
c) Lysosome
d) Actin
2. Which of these are not the hydrolytic enzymes of lysosome?
a) Lipases
b) Sulfatases
c) Phosphatases
d) Aldolase
3.Digestion of cell’s own component is known as__________
a) Autophagy
b) Heterophagy
c) Phagocytosis
d) Pinocytosis
4. What is amphisome?
a) Early endosome
b) Fusion of endosome and autophagosome
c) Vacuole
d) The bigger size of lysosome
5. Name the single membrane which surrounded the vacuoles?
a) Contractile vacuole
b) Meninges
c) Tonoplast
d) Sarcolemma

6. Which of the following pumps excess water out of the cell?
b) Lysosome
c) Peroxisome
d) Vacuoles
7. Which of the following organelle works as a lysosome in the plants?
b) Peroxisome
c) Plastid
d) Vacuole
8. Lysosomes were discovered by
a) Haekal
b) De Duve
c) De Vries
d) Puekinje
9. Which of the following statements is incorrect with reference to lysosome
a) They are filled with acid hydrolase and other enzymes
b) they are monomorphic and uniform in structure and function
c) They may be autophagic
They can digest proteins,nucleic acids ,lipids and polysaccharides
10. Lysosomes are present in all except
a. muscle cells b. acinar cells
c. erythrocytes d. hepatocytes
11. Which of the following is the function of lysosomes
a. autophagy b. autolysis
c. digestion d. all of the above
12. Lysosomes are involved in
a. Extracellular digestion b. Intracellular digestion
c. both (a) and (b) d. none of the above

13.Who identified lysosome
a. Novikoff b. Claude
c. Palade d. none of the above
14. The main function of lysosome is
a) Digestion b) Replication c) Translation d) Translocation
15. Scavenging of worn out cell parts and denatured proteins in the cells is done by
a) Vacuoles b) Golgi bodies c) Lysosome d) Endoplasmic reticulum
16. What would happen if lysosome get ruptured inside the cells in which they are present
a) Cells will swell b) cells will shrink c) Cells will die
d) Nothing would happen
17. Three of the following statements regarding cell organelles are correct while one is wrong. Which one is
wrong
a) Lysosomes are double membrane vesicles budded off from golgi apparatus and contain digestive
enzymes
b) Endoplasmic reticulum consists of a network of membranous tubules and helps in transport,synthesia and
secretion
c) Leucoplast are bound by two membranes lack pigment but contain their own DNa and protein synthesizing
machinery
d) Sphaerosomes are single membrane bound and are associated with synthesis and storage of lipids
18. Microbodies differ from lysosomes in that
a) Microbodies are surrounded by a single unit membrane while lysosome membrane is double
b) Microbodies are surrounded by double membrane while lysosome membrane is single unit
c) Microbodies contain lytic enzymes while lysosome do not
d) Lysosome contain lytic enzymes while microbodies do not
19. The organelle whose major function is storage of hydrolytic enzymes are
a) Centriole b) Chromoplasts c) Lysosome d) Chloroplast
20. The cellular role for lysosome is not
a) Ingestion of foreign bodies b) Digestion of aged organelles
c) Cell destruction during developmeny d) Osmoregulation

21. Which is concerned with autolysis
a) Ribosome b)Golgi bodies c) Lysosome d) Oxysome
22. Lysosome along with the food content is called
a) Primary lysosome b) Secondary lysosome c) Residual bodies d) Cytosome
23. The cell organelle showing extensive polymorphism is
a) Dictyosoe b) Chloroplasts c) Lysosome d) Ribosome
24. The Lysosomes are known as suicidal bags because of
a) Catalytic enzymes b) Hydrolytic enzymes c) Parasitic on nucleus d) Proteolytic enzymes
25. Secondary lysosomes are also called
a) Autophagic vacuoles b) Lipofusion granules c) Residual body d) Heterophagosomes
26. The ‘marker’ enzymes of lysosome is
a) Lysozyme b) Acid protease c) Acid phosphatase d) Beta galactosidase
27. Lysosomes are generally found in
a) Animal cell b) Plant cell c) Both a) and b)
d) Bacterial cells
28.A lysosome in which intracellular organelle is digested is called
a) Primary lysosome b) Secondary lysosome c) Autophagosome d) None of the above
29. Which of the following cell organelle is having single layered unit membrane
a) centrosome b) Lysosome c) Mesosome d)Nucleus
30. Which of the following organelle is called as the “ perinulear dense bodies”?
a) Lysosome b) Nucleolous c) peroxisome d) all of these
31. Which is the enzyme used as a marker for the lysosome
a) a) Pyruvate dehydrogenase b) Phospholipase c) Acid phosphatase d) Succinate
dehydrogenase
32. The pH of lysosome is
a) neutral b) acidic c) basic d) depends on the cell cycle
33. The staining technique used to locate lysosome is
a) a) Janus Green staining b) Bismarck stain c) Gamori stain d) Osmium tetroxide

34. The acidic pH of lysosome is due to
a) deposition of waste materials b) presence of hydrolytic enzymes which has an acidic optimum pH c)
presence of anabolic enzymes which has an acidic optimum pH d) All of these
35. Which of the following organelle is called as the “ suicidal bags of the cell ?
a) Lysosome b) Lysosome and Golgi c) Lysosome and ER d) Lysosome and mitochondria
36. Which of the following is the function of lysosome
a) autophagy b) autolysis c ) digestion d) all of these
37. During protein targeting, lysosomal proteins are tagged with
a) sialic acid b) KDEL sequence c) mannose-6-phosphate d) glycolipids
38. Which of the following is not a disease associated with lysosome malfunctioning
a) Tay-Sachs disease b) I-cell disease c) Pompe’s disease d) Marfan syndrome
39. Lysosomes involved in extracellular digestion are present in
a) cardiac cells b) sperm c) zygote d) All of these
40. The acidic pH in the lysosome is maintained by
a) GTP dependent proton pump in the lumen b) ATP dependent proton pump on the membrane
c) HCl in lysosome d) all of these
41. Lysosomal membrane is rich in
a) cardiolipin b) sialic acid c) sterols d) all of these
42. The main function of lysosomes is ____________
a) excretion b) synthesis c) mobility d) digestion
43. Where is the proton pump located in a lysosome?
a) cytosol b) membrane c) attached with enzymes d) extracellularly connected
44. In autophagy, the organelle’s to be ingested are covered by a ______________
a) protein coat b) oligosaccharides c) double membrane d) single membrane
45. After the digestive process in an autophagolysosome is over, it is termed as _______________
a) autophagosome b) residual body c) endosome d) peroxisome
46. Gaucher disease is caused due to deficiency of ______________
a) hexosaminidase A b) lysosomes c) glucocerebrosidase d) mannose phosphate

47. Which of the following organelle is called ‘Suicidal Bag’
a. Mitochondria b. Endoplasmic reticulum c. Lysosome d. Ribosome
48. In the ‘I-cell disease’, lysosomes are ___________
a) absent b) bloated c) short-lived d) immobile
49. Lysosomal storage disorders are caused due to ______________
a) absence of lysosomes
b) absence of a single lysosome
c) absence of integral membrane proteins
d) accumulation of lipofuschin granules
Answers : Note : Options in red colour are correct choice for MCQs

Answer the following Questions
What is lysosomes and its function?
Why is the lysosome important?
Where is the lysosome located?
What are lysosomes made of?
How big is a lysosome?
Why lysosomes is known as suicidal bag?
How are lysosomes created?
Do lysosomes have DNA?
Who discovered the lysosome?
Are lysosomes phagocytes?
Do lysosomes kill viruses?
What do lysosomes break down?

How do lysosomes break down proteins?
Is lysosome present in human body?
Which enzymes are present in lysosome?
What is stored in lysosomes?
Do lysosomes contain nucleic acids?
Can lysosomes destroy an entire cell?
How do lysosomes maintain their pH?
What diseases are caused by lysosomes?
Do eukaryotic cells have lysosomes?
What do lysosomes do in apoptosis?
Where do lysosomes receive material from?
How many enzymes are present in lysosomes?
How do lysosomes protect the body?

Write short notes on the following
a) Types of lysosomes
b) Primary lysosome
c) Secondary lysosome
d) Chemical composition of lysosomes
e) Enzymes present in lysosome
f)) Lysosomes as suicide bags
g) Functions of lysosome
h) Shape of lysosome
i) size of lysosome
j) Intracellular digestion by lysosome
k) Acid hydrolase enzyme of lysosome
l) Similarity of lysosome and vacuole in plant cells
m) Autophagosome
n) Autophagy
o) I-cell disease
p) Phagocytosis
q) Phagolysosome

BOOKS CONSULTED
Cell and molecular biology Concepts and Experiments Gerald Karp 5th Edition 2007 John
Willey and Sons, Inc
Cell and Molecular biology By P K Gupta: Rastogi Publications
Biocyclopaedia Is online for students and researchers in Biology Biocyclopedia.com
Cell Biology by Dr S P Singh and Dr B S Tomar Rastogi Publication,Meerut,U P ,India
Cell Biology 1997 Dr SC Roy and Dr K K De New Central Book Agency (P ) Ltd. Kolkatta , India
Molecular Cell Biology. 4th edition.2000 H Lodish, A Berk and S L Zipursky W. H. Freeman;
New York . Section 5.4 Organelles of the Eukaryotic Cell Lysosomes Are Acidic Organelles
That Contain a Battery of Degradative Enzymes
Lysosome : British Society for Cell Biology
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.New York:
Garland Science; 2002.
The Cell: A Molecular Approach. 2nd edition. Cooper GM.Sunderland (MA): Sinauer Associates;
2000.Lysosome (Figure : 9.35,9.36 and 9.37)
8/20/2020 Structure and function of GA 41
iGenetics A molecular Approach Third Edition Peter J Russell Benjamin
Cummmings,New York

REFERENCES
Bainton, D.F. (1981) The discovery of lysosomes. J. Cell Biol. 91 : 66s–76s
HSU VW, Lee S Y and Yang J S( 2009) Pathways of vesicular transport by the specific
vesicle-coating proteins .Nature Reviews, Molecular Cell Biology 10: 360-364
Trivedi et al 2020 Lysosomal Biology and Function: Modern View of Cellular Debris
Bin. Cells 1-35 Review Article
De Duve C ( 2005). "The lysosome turns fifty". Nature Cell Biology. 7 (9): 847–
849.
Novikoff A B, Beaufay H and De Duve C (1956) . Electron microscopy of lysosome
rich fractions from rat liver . The Journal of Biophysical and Biochemical Cytology.
2:179-184
Novikoff A B 1976 In Lysosome and Storage Diseases H G Hers and F Van Hoof
Editors .Academic Press, New York. 1-41
Rogers K (2019) Lysosome Biology from Encyclopaedia Britannica
Hurler, G. (1919). "Über einen Typ multipler Abartungen, vorwiegend am
Skelettsystem". Zeitschrift für Kinderheilkunde. 24 (5–6): 220–234.

THE END
THANKS Courtsey: The Cell: A Molecular
Approach. 2nd edition
Cooper GM. Sunderland (MA): Sinauer
Associates; 2000.
From :The discovery of lysosomes by
D F Bainton (1981)

Structure and function of lysosome

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