Animal Cells Explained | Definition, Functions & Diagram

Animal Cell Diagram

This animal cell diagram shows an animal cell labeled. Animal cells are a lot more complex than this animal cell diagram but this also depends on the type of cell it is. This diagram is typical of an animal cell GCSE level of knowledge.  An A Level Biology animal cell would require a lot more detail to be shown for a labeled animal cell diagram. 

What is an animal cell?

An animal cell is the fundamental unit of all animal organisms. It is often described as the basic building block of life. They are found in all living organisms that are classified in the Kingdom Animalia. 

What is animal cell structure?

Animal cell structure will vary depending on the type of animal cell you are looking at but all animal cells have some key features in common such as:

• A cell membrane: allows passage of substances into and out of the cell

• Nucleus: contains the genetic material, DNA

• Mitochondria: carries out respiration to release energy

• Ribosomes: create proteins

• Cytoplasm: carries out many cell chemical reactions

We will look at some of these in a little more detail later in this article.

Animal Cell Functions

The key functions of animal cells are:

• Give structure to the organism

• Allow animals to move

• Contain genetic material in the form of DNA

• Absorb nutrients, such as glucose, that are converted into energy

• Create proteins, including enzymes

• Break down and recycle materials 

Let’s take a look at some of the parts of an animal cell in more detail. This will include some of the common organelles of an animal; organelle is a fancy word to describe a structure within a cell, including both plant and animal cells.

Nucleus Animal Cell

The animal cell nucleus is the largest organelle within animal cells and contains the genetic material in the form of DNA and chromosomes. The function of the nucleus in an animal cell is to carry out and coordinate major cell processes such as DNA replication, transcription and translation. The nucleus is split into different key parts which are:

• Nuclear envelope - allows genetic material in and out of the nucleus through nuclear pores

• Nucleoplasm - a thick fluid that supports the nucleus

• Chromatin - a mixture of DNA and proteins

• Nucleolus - produces and assembles ribosome organelles

• Endoplasmic reticulum - surrounds the nucleus and is a site of protein synthesis

The nucleus of an animal cell

Ribosomes in animal cells

A ribosome is an intracellular organelle that is made of protein and RNA. RNA is a nucleic acid similar to DNA.  Ribosomes are the site of protein synthesis.

Cell membrane animal cell

The cell membrane is also known as the plasma membrane. It is found in all cells, including plant and animal cells. It separates the interior and exterior of the cell. The cell membrane is made up of a lipid bilayer, embedded with proteins, which is semipermeable; this means that certain substances can pass across the membrane helping to regulate what is transported into and out of the cell.  

Cell membrane of animal cell

Cytoplasm function in animal cells

The cytoplasm’s function is to support the cell and give it shape; it holds all the organelles of the cell. It is a gel-like substance that allows the movement of  substances around the cell such as hormones. 

Function of mitochondria in animal cells

The mitochondria are large organelles that are the site of cellular respiration, which releases energy to the cell in the form of ATP. They are membrane-bound organelles which is an important classification of all eukaryotic cells. Mitochondria also store calcium needed for cell signaling and they help regulate cell growth and death. 

Lysosome function in animal cells

Lysosomes are another membrane-bound organelle found within animal cells and contain hydrolytic enzymes. This allows them to digest waste cell material and pathogens. Animal cells can contain between 50 - 1000 lysosomes per cell and each lysosome contains around 50 different digestive enzymes. 

Centrosome function in animal cells

Centrosomes are structures that are required for the cellular process of cell division. They are also known as microtubule organisers, or microtubule organising centres (MTOC); this means that they are responsible for cell mobility, polarity and adhesion. They also play a critical role in the movement of microtubules during cell division. It is thought that irregular or extra centrosomes may play a role in abnormal cell division and therefore some cancers. 

Functions of rough endoplasmic reticulum in animal cells

There are two types of endoplasmic reticulum, rough (RER) and smooth endoplasmic reticulum (SER). The rough endoplasmic reticulum is dotted with ribosomes, which gives it its name. The RER is a continuous membrane of flattened sacs called cisternae,which are an extension of the nuclear envelope. 

The Rough Endoplasmic Reticulum

Types of animal cell

Examples of common animal cells include:

• Muscle cells

• Blood cells

• Skin cells

• Nerve cells

• Sex cells, also known as gametes

• Stem cells

Each of these are termed specialised cells and have their own unique structure related to their specific function.

You can read more about specialised animal cells here: Specialised cells

The difference between animal and plant cells

There are three key differences between plant and animal cells:

1. Plant cells have a cell wall running outside of their cell membrane, whereas animal cells only have a cell membrane

2. Plant cells contain a large vacuole (some animal cells can contain vacuoles but this is less common)

3. Plant cells contain chloroplasts which are the site of  photosynthesis

This diagram shows the difference between animal and plant cells

Five facts about animal cells

1. Animal cells are eukaryotic meaning they have a nucleus and membrane-bound organelles

2. Only red blood cells do not a nucleus

3. Animal cells carry out many critical reactions such as respiration, cell division, digestion of waste products

4. Fully-grown humans have over 40 trillion animal cells

5. Some stem cells, a specialised animal cell, are totipotent, meaning they can become any type of other animal cell

Animal Cell FAQs

In which type of cell would you find a permanent (sap) vacuole: a plant or animal cell?

A permanent vacuole is found in plant and fungal cells, not animal cells. Animal cells may contain vacuoles but these are not considered permanent. 

In animal and plant cells, in which part of the cell are chromosomes found?

Chromosomes are found within the nucleus of cells. Chromosomes are tightly coiled lengths of DNA.

What name is given to animal cells with the capacity to differentiate into a specialised cell?

Stem cells. Stem cells can be embryonic in form, or somatic stem cells.

What does an animal cell look like?

Animal cells are made up of several parts which are called organelles. These are spread out around the cell as shown in the diagram below. Animal cells can be different shapes and sizes depending on their function and location within the organism. 

A diagram of an animal cell showing an A Level animal cell

What does a plant cell have that an animal cell does not?

A plant cell has a cell wall, a permanent vacuole and chloroplasts and animal cells do not have these features. 

What is the function of the mitochondria in an animal cell?

Mitochondria are membrane bound organelles that process glucose to release energy to the cell in the form of ATP. 

What do lysosomes do in an animal cell?

Lysosomes have the function of digesting waste substances within the cell. Some may be recycled and reused by the cell.