Animal Cells: Labelled Diagram, Definitions, and Structure
What is a Cell?
In biology, cell is the smallest unit that can live on its own and that makes up all living organisms and the tissues of the body. A cell has three main parts: the cell membrane, the nucleus, and the cytoplasm.
What is Animal Cell?
Animals are made of eukaryotic cells having nucleus, cellular organelles, and are surrounded by a cell membrane or plasma membrane.
What is Plant Cell?
Plant cell are the basic unit of all plants. Plant cells, like animal cells, are eukaryotic, meaning they have a membrane-bound nucleus and organelles.
Animal Cells Diagram
Animal Cells Organelles and Functions
| Cell Organelles | Functions |
| Cell Membrane | A double layer that supports and protects the cell. Allows materials in and out. |
| Nucleus | The control center of the cell. Nucleus contains majority of cell’s the DNA |
| Mitochondria | Popularly known as the “Powerhouse”. Breaks down food to produce energy in the form of ATP. |
| Golgi Body | Processes and packages materials for the cell. |
| Lysosome | Contains digestive enzymes that destroy damaged organelles and invaders. |
| Rough E.R. | Builds and transports substances through the cell. Has ribosomes on it. |
| Smooth E.R. | Builds and transports substances through the cell. Does not have ribosomes. |
| Cytoplasm | Jelly-like fluid that surrounds and protects the organelles. |
| Ribosome | Helps make protein for the cell. |
| Vacuole | Stores food and water. |
| Nucleolus | A round structure in the nucleus that makes ribosomes. |
| Nuclear Membrane | Surrounds the nucleus. |
Plant Cells Diagram
Plant Cells Organelles and Functions
| Cell Organelles | Functions |
| Cell Wall | Gives shape and protection to plant cells. |
| Chloroplast | Changes sunlight into sugar for plant cells. Contains a green pigment called chlorophyll. |
| Cell Membrane | A double layer that supports and protects the cell. Allows materials in and out. |
| Nucleus | The control center of the cell. Nucleus contains majority of cell’s the DNA |
| Mitochondria | Popularly known as the “Powerhouse”. Breaks down food to produce energy in the form of ATP. |
| Golgi Body | Processes and packages materials for the cell. |
| Lysosome | Contains digestive enzymes that destroy damaged organelles and invaders. |
| Rough E.R. | Builds and transports substances through the cell. Has ribosomes on it. |
| Smooth E.R. | Builds and transports substances through the cell. Does not have ribosomes. |
| Cytoplasm | Jelly-like fluid that surrounds and protects the organelles. |
| Ribosome | Helps make protein for the cell. |
| Vacuole | Stores food and water. |
| Nucleolus | A round structure in the nucleus that makes ribosomes. |
| Nuclear Membrane | Surrounds the nucleus. |
Animals Cells Vs Plant Cells
Plant and animal cells have several differences such as plant cells have a cell wall or chloroplasts, but animal cells do not have either. Plant cells are fixed, rectangular in shapes, but animal cells are mostly round and irregular in shape.
On the other hand, plant and animal cells are both eukaryotic cells, so they have several features in common, such as the presence of a cell membrane, and cell organelles, like the nucleus, mitochondria and endoplasmic reticulum.
| Cell Organelles | Plant Cells | Animal Cells |
| Cell wall | Present (made up of cellulose) | Absent |
| Shape | Rectangular (fixed shape) | Round (irregular shape) |
| Vacuole | One, large central vacuole taking up to 90% of cell volume. | One or more small vacuoles (much smaller than plant cells). |
| Centrioles | Only present in lower plant forms (e.g. chlamydomonas) | Present in all animal cells |
| Chloroplast | Plant cells have chloroplasts to synthesize their own food. | Absent |
| Plasma Membrane | Cell wall and a cell membrane | Only cell membrane |
| Flagella | Present in some cells (e.g. sperm of bryophytes and pteridophytes, cycads and Ginkgo) | Present in some cells ( e.g. mammalian sperm cells) |
| Cilia | Most plant cells do not contain cilia. | Present |
| Lysosomes | Lysosomes usually not evident. | Lysosomes occur in cytoplasm. |
| Cytoplasm | Present | Present |
| Ribosomes | Present | Present |
| Mitochondria | Present | Present |
| Plastids | Present | Absent |
| Endoplasmic Reticulum | Present | Present |
| Peroxisomes | Present | |
| Golgi Apparatus | Present | Present |
| Microtubules/ Microfilaments | Present | Present |
| Nucleus | Present | Present |
Cilia and Flagella
Some eukaryotic cells either have cilia or flagella. Cilia are small, wiggling arm-like structures, whereas flagella are like a tail.
Both structures are made of long protein fibers called microtubules, with a structure where nine microtubules form a ring around two central microtubules.
Cell Membrane
The cell membrane encloses the cell’s contents. It monitors what comes in, and what goes out. It has a characteristic called semi permeability, meaning it can “choose” what molecules can come in and out of the cell.
Cytoplasm / Cytoskeleton / Centrosomes
There are water and nutrients within the cell. The cytoskeleton is a collection of protein strands that reinforce the cell.
Centrosomes are a part of this reinforcement. They assemble long microtubules out of proteins. The cytoplasm provides the infrastructure that is necessary for cells to thrive and for the organelles to do their jobs within the cell.
The nucleus of the cell has its own type of cytoplasm, called the nucleoplasm.
Endoplasmic Reticulum
The endoplasmic reticulum(s) are organelles that create a network of membranes that transport substances around the cell.
They have phospholipid bilayers. There are two types of ER: the rough ER, and the smooth ER. The rough endoplasmic reticulum is rough because it has ribosomes (which is explained below) attached to it. It helps in the synthesis and packaging of proteins.
The smooth endoplasmic reticulum doesn’t have ribosomes attached. It contains enzymes that help with the creation of important lipids. It has a role in the process of cell detoxification or removal of waste materials. The smooth ER adds a carboxyl group to noxious substances, making them soluble in water.
Ribosomes
Ribosomes create proteins. They can float freely in the cytoplasm or can be attached to the nuclear envelope. They create proteins by assembling amino acids into polypeptides.
As the ribosomes build an amino acid chain, the chain is pushed into the endoplasmic reticulum. When the protein chain is complete, the endoplasmic reticulum pinches it off and sends it to the Golgi apparatus.
Golgi Apparatus
The Golgi apparatus focuses on protein processing and packaging. Golgi bodies are the Golgi apparatus’s layers. Golgi bodies cut up large proteins into smaller hormones.
They can combine proteins with carbohydrates to make various molecules. They then package these products into sacs like structure popularly known as called vesicles, which ship the products of the Golgi body to other parts of the cell, and outside the cell as well.
Lysosomes
Lysosomes are enzyme sacs that break down cellular waste – they process cell digestion. They can take substances from outside of the cell and cellular waste and turn them into simple compounds.
The compounds are then transferred into the cytoplasm where they can be used as a cell building material.
Nucleus
The nucleus is a highly specialized organelle that lives in its own double membrane with the nucleolus. The nucleus stores the cell’s DNA and holds all the information the cell needs to do its job.
Chromatin is a web-like substance that holds the nucleus’s DNA. Chromatin gathers into rod-shaped chromosomes that hold DNA molecules when the cell is ready to split during cell division.
The nucleolus lives inside the nucleus and is the only organelle that is not enveloped by its own membrane. It makes ribosomal RNA, rRNA, which is important during protein synthesis.
Ribosomal RNA or rRNA combines with proteins to form the basic units of ribosomes. When the units are done, the nucleus spits them out of the nuclear envelope, where they are assembled into ribosomes.
The nucleus sends orders in the form of messenger RNA, or mRNA. The messages are sent to ribosomes, which carry out the orders in the rest of the cell.
Mitochondria
The mitochondria is the “power house” of the cell. This is where cellular respiration takes place. During this, energy is derived and converted into ATP from fats, carbohydrates, and other biomolecules.
Mitochondria almost act as independent cellular organelle and have their own DNA, know as mitochondrial DNA (mtDNA) which is an exact replication of the mother’s DNA.
Animal Cells Citations
- Relationships between the central spindle and the contractile ring during cytokinesis in animal cells. Microsc Res Tech . 2000 Apr 15;49(2):202-8.
- Establishment of the mechanism of cytokinesis in animal cells. Int Rev Cytol . 1986;105:245-81.
- Cytokinesis in plant and animal cells: endosomes ‘shut the door’. Dev Biol . 2006 Jun 1;294(1):1-10.
- Cytokinesis in animal cells. Cold Spring Harb Perspect Biol . 2015 Feb 13;7(4):a015834.
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