Alzheimer's»

Organelle Dysfunction Project · Anatomy

Alzheimer's: when the cell's recycling center breaks.

Alzheimer's disease is a brain disease that slowly erases memory, thinking and, in the end, the body's basic functions. The organelle behind it: the lysosome, the part of the cell that digests and recycles junk. When it fails, junk protein piles up inside brain cells until they die.

Start with the organelle
Healthy brain next to a brain with Alzheimer's Image: National Institute on Aging (ADEAR), public domain, Wikimedia Commons 01 07 Next: The Organelle Meet the lysosome, the cell's recycling center

01 / The disorder

Alzheimer's disease

Malfunctioning organelle: the lysosome (with the mitochondria hit next).

Alzheimer's is the most common cause of dementia, behind about 60-80% of cases. Dementia means memory and thinking loss bad enough to get in the way of daily life.

Neurons (brain cells) stop working, lose their connections and die. Two kinds of junk protein build up: beta-amyloid plaques between cells and tau tangles inside them.

It's named after Dr. Alois Alzheimer, who found those plaques and tangles in a patient's brain in 1906.

See the organelleAlzheimer's Association
Plaques and tangles: the junk proteins that build up in Alzheimer's.
Plaques and tangles: the junk proteins that build up in Alzheimer's.
Image: BruceBlaus (Blausen Medical), CC BY 3.0, Wikimedia Commons

02 / Who it affects

Who gets it

7.4MAmericans age 65+ living with Alzheimer's in 2026
2 of 3patients are women (4.5 million women vs 2.9 million men)
2×Black older adults are about twice as likely to have it as White older adults; Hispanic older adults about 1.5×
35.8%of people age 85 and older have it, versus 5.2% of people age 65-74

Age is the biggest risk, but Alzheimer's is not a normal part of getting old. Full numbers are on the Statistics tab.

03 / The big idea

A cleanup system that broke

Every cell has a lysosome: a tiny acid-filled bubble that breaks down old parts and junk. Brain cells never get replaced, so they need their lysosomes working for a whole lifetime.

A 2022 study found that in Alzheimer's, lysosomes in neurons lose their acid. Junk protein piles up inside them, and the neuron dies and leaves behind a plaque.

How it breaks
The lysosome when healthy, and in Alzheimer's.
The lysosome when healthy, and in Alzheimer's.
Image: Diagram made for this project, based on Lee et al. 2010 (Cell) and Nixon & Rubinsztein 2024

Sources for this tab

  1. Alzheimer's Association. What Is Alzheimer's Disease? https://www.alz.org/alzheimers-dementia/what-is-alzheimers
  2. National Institute on Aging. What Happens to the Brain in Alzheimer's Disease? https://www.nia.nih.gov/health/alzheimers-causes-and-risk-factors/what-happens-brain-alzheimers-disease
  3. National Institute on Aging. Alzheimer's Disease Fact Sheet. https://www.nia.nih.gov/health/alzheimers-and-dementia/alzheimers-disease-fact-sheet
  4. Alzheimer's Association. 2026 Alzheimer's Disease Facts and Figures (Alzheimer's & Dementia, 2026). https://pmc.ncbi.nlm.nih.gov/articles/PMC13098189/
  5. Lee JH, Yang DS, Goulbourne CN, et al., Nixon RA (2022). Faulty autolysosome acidification in Alzheimer's disease mouse models induces autophagic build-up of Aβ in neurons, yielding senile plaques. Nature Neuroscience 25:688-701. https://pmc.ncbi.nlm.nih.gov/articles/PMC9174056