---
title: "Cell Adhesion Proteins | General Biology I"
description: "Cell adhesion proteins let cells stick to each other and the extracellular matrix in General Biology I, shaping tissues, signaling, and movement."
canonical: "https://fiveable.me/college-bio/key-terms/cell-adhesion-proteins"
type: "key-term"
subject: "General Biology I"
unit: "Unit 5"
---

# Cell Adhesion Proteins | General Biology I

## Definition

Cell adhesion proteins are membrane proteins that help cells attach to other cells and to the extracellular matrix in General Biology I. They keep tissues organized and also send signals inside the cell.

## What It Is

Cell adhesion proteins are surface proteins in General Biology I that let cells bind to each other or to the extracellular matrix (ECM). They are part of how multicellular organisms stay organized, because cells do not just float next to each other, they need controlled connections to form tissues and organs.

The main idea is that these proteins do two jobs at once. First, they act like physical connectors, linking a cell to nearby cells or to the ECM outside the cell. Second, they can trigger signals inside the cell when they bind, so the cell can respond by changing shape, movement, growth, or gene expression.

Different families do this in different ways. Cadherins usually help cells stick to other cells, especially in tissues that need tight organization. Integrins link cells to the ECM, which is the material surrounding cells that includes proteins like collagen and other support molecules. Selectins are often involved in temporary sticking, such as in immune cell movement.

These proteins are embedded in or attached to the plasma membrane, so they sit right at the boundary between the cell and its environment. That location matters because the membrane is not just a barrier, it is also a communication surface. When a cell binds to another cell or to the ECM, the cell can sense what is around it and adjust accordingly.

A useful way to picture them is as molecular handshakes. The handshake can be strong and stable, like in a tissue layer that needs to stay together, or loose and temporary, like when a white blood cell rolls along a blood vessel wall before moving into damaged tissue. The strength and timing of adhesion change depending on the cell type and the signals it receives.

If adhesion proteins stop working correctly, cells may lose their normal placement and behavior. That can affect development, wound healing, and even cancer, since cells that detach too easily can invade other tissues more easily.

## Why It Matters

Cell adhesion proteins show up anywhere you need to explain how cells become organized into tissues instead of staying as isolated units. In General Biology I, they connect membrane structure to bigger ideas like cell communication, development, and homeostasis.

They also give you a clean example of structure-function relationships. A protein’s shape, location in the membrane, and binding partner all affect what it can do. If a cadherin cannot bind properly, cells may not hold tissue layers together the way they should. If an integrin cannot connect to the ECM, the cell may lose its anchor or fail to receive outside signals.

This term also helps when you study disease and cell movement. Cancer cells often change adhesion behavior, which can let them break away from the original tumor and spread. Immune cells use adhesion in a more controlled way, sticking where they are needed and then moving on. So this one concept helps explain normal tissue structure and what goes wrong when cells stop adhering normally.

## Connections

### Cadherins

Cadherins are a major family of cell adhesion proteins that usually bind one cell to another. In tissues, they help neighboring cells stay lined up and organized, especially where stable cell-cell contact matters. If you are looking at epithelial layers or tissue formation, cadherins are often the proteins doing the sticking.

### Integrins

Integrins connect cells to the extracellular matrix instead of mainly to other cells. They matter because they anchor a cell in place and can also relay information about the outside environment into the cell. In biology diagrams, they often appear as membrane proteins linking the cytoskeleton to the ECM.

### Extracellular Matrix (ECM)

The ECM is the network outside cells that gives tissues support and a surface for attachment. Cell adhesion proteins, especially integrins, connect cells to this matrix. That connection affects how cells migrate, how tissues hold shape, and how cells respond to mechanical and chemical signals.

### [Integral proteins](/college-bio/key-terms/integral-proteins)

Cell adhesion proteins are often integral proteins, meaning they are embedded in the membrane. That placement lets them span the boundary between inside and outside, which is why they can link external structures to internal cell parts. When you see a membrane protein with an outside binding site and an inside signaling effect, think of an integral protein.

## On the AP Exam

A quiz question might show a tissue diagram, membrane graphic, or cell-movement scenario and ask you to identify which protein family is doing the binding. Your job is to trace the connection: cell to cell means cadherins, cell to ECM means integrins, temporary sticking in movement or immune response may point to selectins. In short-answer or lab questions, you may explain how adhesion changes cell shape, tissue strength, or migration. If a prompt describes cancer spreading, wound healing, or white blood cells leaving the bloodstream, adhesion proteins are usually part of the mechanism you should name and explain.

## cell adhesion proteins vs Extracellular Matrix (ECM)

These are easy to mix up because they work together, but they are not the same thing. The ECM is the material outside cells, while cell adhesion proteins are the membrane proteins that attach the cell to that material or to other cells. Think of the ECM as the surface and the adhesion proteins as the connectors.

## Key Takeaways

- Cell adhesion proteins are membrane proteins that help cells stick to other cells or to the extracellular matrix.
- They do more than hold cells in place, because binding can also send signals that change cell behavior.
- Cadherins usually support cell to cell adhesion, while integrins connect cells to the extracellular matrix.
- These proteins help tissues stay organized, support development, and let cells move when they need to.
- Problems with cell adhesion can show up in cancer, immune movement, wound repair, and tissue structure.

## FAQs

### What are cell adhesion proteins in General Biology I?

They are membrane proteins that let cells attach to other cells or to the extracellular matrix. In General Biology I, you usually study them as part of membrane structure, tissue organization, and cell signaling. They matter because attachment is not just physical, it also affects how cells behave.

### What is the difference between cell adhesion proteins and the extracellular matrix?

The extracellular matrix is the material outside cells that provides support and a surface for attachment. Cell adhesion proteins are the proteins in the membrane that connect the cell to that material or to neighboring cells. So one is the outside framework, and the other is the connector.

### Are cadherins and integrins cell adhesion proteins?

Yes. Cadherins mainly bind cells to other cells, while integrins mainly bind cells to the extracellular matrix. They are two of the most common families you will see in introductory biology when tissue structure and cell movement come up.

### How do cell adhesion proteins relate to cancer?

Cancer cells can change or lose normal adhesion, which can let them detach from the original tumor and spread to new tissues. That is why adhesion is tied to metastasis. The basic idea is that cells that no longer stick where they should can move too easily.

## Related Study Guides

- [5.1 Components and Structure](/college-bio/unit-5/1-components-structure/study-guide/6GsvOMlJZV8ncXIO)

## About This Document

Canonical Fiveable pages are available as Markdown at the same path plus `.md`.

- [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns
- [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing
- [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`)
- [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`)

## Structured Data

```json
{"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/college-bio/key-terms/cell-adhesion-proteins#resource","name":"Cell Adhesion Proteins | General Biology I","url":"https://fiveable.me/college-bio/key-terms/cell-adhesion-proteins","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/college-bio/key-terms/cell-adhesion-proteins#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:21:07.934Z","isPartOf":{"@type":"Collection","name":"General Biology I Key Terms","url":"https://fiveable.me/college-bio/key-terms"},"author":{"@type":"Organization","@id":"https://fiveable.me/editorial#content-team","name":"Fiveable Content Team","url":"https://fiveable.me/editorial","parentOrganization":{"@id":"https://fiveable.me/#organization"},"member":[{"@type":"Person","name":"Amanda DoAmaral","sameAs":["https://www.linkedin.com/in/adoamaral"]},{"@type":"Person","name":"Becky Bahr","sameAs":["https://www.linkedin.com/in/becky-bahr-b52743132"]}]},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/college-bio/key-terms/cell-adhesion-proteins#term","name":"cell adhesion proteins","description":"Cell adhesion proteins are membrane proteins that help cells attach to other cells and to the extracellular matrix in General Biology I. They keep tissues organized and also send signals inside the cell.","url":"https://fiveable.me/college-bio/key-terms/cell-adhesion-proteins","inDefinedTermSet":{"@type":"DefinedTermSet","name":"General Biology I Key Terms","url":"https://fiveable.me/college-bio/key-terms"}},{"@type":"FAQPage","mainEntity":[{"@type":"Question","name":"What are cell adhesion proteins in General Biology I?","acceptedAnswer":{"@type":"Answer","text":"They are membrane proteins that let cells attach to other cells or to the extracellular matrix. In General Biology I, you usually study them as part of membrane structure, tissue organization, and cell signaling. They matter because attachment is not just physical, it also affects how cells behave."}},{"@type":"Question","name":"What is the difference between cell adhesion proteins and the extracellular matrix?","acceptedAnswer":{"@type":"Answer","text":"The extracellular matrix is the material outside cells that provides support and a surface for attachment. Cell adhesion proteins are the proteins in the membrane that connect the cell to that material or to neighboring cells. So one is the outside framework, and the other is the connector."}},{"@type":"Question","name":"Are cadherins and integrins cell adhesion proteins?","acceptedAnswer":{"@type":"Answer","text":"Yes. Cadherins mainly bind cells to other cells, while integrins mainly bind cells to the extracellular matrix. They are two of the most common families you will see in introductory biology when tissue structure and cell movement come up."}},{"@type":"Question","name":"How do cell adhesion proteins relate to cancer?","acceptedAnswer":{"@type":"Answer","text":"Cancer cells can change or lose normal adhesion, which can let them detach from the original tumor and spread to new tissues. That is why adhesion is tied to metastasis. The basic idea is that cells that no longer stick where they should can move too easily."}}]},{"@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"General Biology I","item":"https://fiveable.me/college-bio"},{"@type":"ListItem","position":2,"name":"Key Terms","item":"https://fiveable.me/college-bio/key-terms"},{"@type":"ListItem","position":3,"name":"Unit 5","item":"https://fiveable.me/college-bio/unit-5"},{"@type":"ListItem","position":4,"name":"cell adhesion proteins"}]}]}
```