Lysosomes CELL BIOLOGY

PRESENTED BY:-

NEHA MAYACH NEHA MAYACH

M.SC LIFE SCIENCE

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Contents Introduction

Lysosomal Enzymes

Site of Lysosome synthesis

Features

Pathways leading to lysosomes

Process for digestion

1. Phagocytosis

2. Endocytosis

3. Autophagy

Types of Lysosomes

Diseases

Some facts

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INTRODUCTION

What are Lysosomes…?

Lysosomes are spherical organelle that contain

enzymes acid hydrolases. They break up food so it is

easier to digest. They are found in animal cells, while

in yeast and plants the same roles are performed by

lytic vacuoles.

Discovered by De Duve in 1955.Named also.

1st electron micrograph by Novikoff.

In 1974 De Duve got nobel prize.

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Lysosomes are common in animal cells but rare in

plant cells contain hydrolytic enzymes necessary for

intracellular digestion.

The size of lysosomes varies from 0.1–0.8 μm. They

are larger in phagocytes(WBC) 0.8-2 µm.

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All these hydrolytic enzymes are produced in the

endoplasmic reticulum, and to some extent in

cytoplasm are transported and processed through

the Golgi apparatus.

and through golgi apparatus they pinch off as

single membrane vesicles.

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It is called :

"The Police Force of the Cell"

"suicide bags“

“Stomach of cell”

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SITE OF SYNTHESIS

Lysosomes are produced in the Golgi Apparatus

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FEATURES

A lysosome is a membrane bag containing

digestive enzymes

to digest food, the lysosome membrane fuses with

the membrane of a food vacuole and squirts the

enzymes inside.

The digested food can then diffuse through the

vacuole membrane and enter the cell to be used

for energy or growth.

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Lysosomes are the cell’s garbage disposal system. They are used for the digestion of macromolecules

from

1.Phagocytosis (ingestion of larger extracellular

material, like foreign invading microbes) .

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2.Endocytosis (ingestion of macromolecules where

receptor proteins are recycled from the cell surface),

and

3.Autophagy (wherein old or unneeded organelles or

proteins, or microbes that have invaded the

cytoplasm are delivered to the lysosome).

Autophagy may also lead to autophagic cell death,

a form of programmed self-destruction, or autolysis, of

the cell, which means that the cell is digesting itself.

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TYPES OF LYSOSOMES

Lysosomes pick up foreign invaders such as bacteria, food and old organelles and break them into small pieces that can hopefully be used again.

(Recycling unit of cell)

In human liver cells it is calculated that at least one mitochondria undergoes autophagy every 10 minutes. This reflects the highly active nature of the liver as an organ and it's need for a constant supply of fresh organelles. The electron micrograph below shows a lysosome in the process of destroying a membrane bound mitochondria.

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Tay Sach’s Disease 16 • A lysosomal storage disease(LSD)

– Due to a mutation in

lysosomal enzymes

B-N-hexosaminidase-A*

• Accumulations of un-degraded

glycolipid (Ganglioside) within

lysosomes in brain NERVE CELL

• Found in neurons of CNS

• Diagnostic feature-Cherry red

spot on Retina(By Tay-name of

scientist)

• Autosomal recessive genetic

disorder

Pompe’s Disease- lysosomes of some people lack enzymes for

digestion of Glycogen. In such persons excessive storage of glycogen

occurs in liver.

Lysosomal enzymes are synthesized in the cytosol and the

endoplasmic reticulum, where they receive a mannose-6-phosphate

tag that targets them for the lysosome.

If the lysosomal enzymes do not reach the target it causes inclusion-

cell disease, resulting in accumulation of waste within these

organelles.

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FACTS

The only thing that keeps the cell itself from being digested is

the membrane surrounding the lysosomes.

Highly polymorphic cell organelle.

Lyosomes of Osteoclast cells(bone eating cells) dissolves

unwanted part of bones.

Crinophagy - Excessive secretion of hormone in endocrine gland may be digested by lysosomes.

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These enzymes work only at low pH

(highly acidic) levels.

However because they can only work at

low pH levels and the rest of the cell has

a neutral pH level, they can be

neutralized if they accidentally escape

from the lysosome

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In white blood cells that eat bacteria,

lysosome contents are carefully released

into the vacuole around the bacteria

and serve to kill and digest those

bacteria. Uncontrolled release of

lysosome contents into the cytoplasm

can also cause cell death (necrosis).

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THANK YOU

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