Lysosome Diagram Labeled – Membrane, Enzymes, Pump

All 10 parts on the diagram

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Start here: 4 main parts 4

Membrane Keeps the lysosome's contents apart from the rest of its cell. A single membrane, a phospholipid bilayer.
Lumen The acidic space inside. It is about pH 4.5 to 5, while the cytosol round it is about pH 7.2.
Hydrolytic enzymes Over 60 different hydrolases that work best in acid. They break proteins, fats, sugars and nucleic acids down into their building blocks.
Lysosome Full of enzymes that digest what the cell no longer needs. A small membrane-bound organelle, a few hundred to a cell.

In the membrane: 3 3

Glycocalyx A coat of sugar chains on the membrane's proteins, lining the inside. It protects the membrane from the lysosome's own enzymes.
Proton pump A pump in the membrane, a V-ATPase, that pushes hydrogen ions in. That is what keeps the inside acidic.
Transport protein Lets broken-down building blocks out into the cell to be used again. A protein in the membrane.

Where it comes from and what it meets: 4 3

Golgi apparatus Enzymes made in the endoplasmic reticulum are tagged here. They are sent off in vesicles to become part of lysosomes.
Phagosome A bubble of membrane round something the cell has swallowed. That could be a bacterium. The bubble fuses with a lysosome to be digested.
Autophagosome A double membrane wrapped round a worn-out part of the cell. Here it holds a mitochondrion. It fuses with a lysosome in autophagy, or self-eating.

How this list was compiled: Read 2026-09-27. Wikipedia, Lysosome, https://en.wikipedia.org/wiki/Lysosome : a membrane-bound organelle limited by a single phospholipid bilayer; the membrane carries heavily glycosylated proteins forming a glycocalyx that protects it from the enzymes inside; over 60 hydrolases, which need an acidic pH of about 4.5 to 5.0, against the cytosol's 7.2; a proton pump (V-ATPase) in the membrane moves protons into the lumen; products are exported through membrane transporters or vesicles to be reused; hydrolases are made in the endoplasmic reticulum, tagged with mannose-6-phosphate in the Golgi apparatus and sent in vesicles; lysosomes fuse with phagosomes and with autophagosomes carrying damaged organelles (autophagy); several hundred per cell. Licence: own work

The drawing: Drawn for this site by script, 2026-09-27. Own work, nothing traced. Licence: own work

How it works

A lysosome diagram labeled in two views: one lysosome cut open, then the Golgi apparatus it comes from and the things it digests. Start with the 4 main parts.

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Inside the lysosome

A single membrane holds over 60 digestive enzymes. A proton pump in the membrane keeps the inside acidic, which is where the enzymes work best, and a sugar coat on the inner face protects the membrane itself.

What it digests

Enzymes come from the Golgi apparatus in vesicles. Lysosomes fuse with phagosomes carrying things the cell has swallowed, and with autophagosomes carrying its own worn-out parts.

Lyso- means breaking down and -some means body: a lysosome is a body that breaks things down.

Questions and answers

What is the function of a lysosome?

It digests what the cell no longer needs: swallowed bacteria and debris, and the cell's own worn-out parts. Its enzymes break these down into building blocks the cell can reuse.

Why is the inside of a lysosome acidic?

A proton pump in its membrane pushes hydrogen ions in, keeping it at about pH 4.5 to 5. Its enzymes work best at that acidity.

Where do lysosomes come from?

Their enzymes are made in the endoplasmic reticulum, tagged in the Golgi apparatus and sent off in vesicles, which become part of lysosomes.